Mah baby has a cold

[MrSavvy]

Trying to narrow down the cause of this issue.
Around 6-7k, the power band stops. The engine/exhaust noise gets super flat. Reminds me of a clipping audio driver (speaker).

This only happens sometimes.
If I drive like a granny, it doesn't happen as often.

If I really get on it, from 20mph-40mph, that's when this problem pops up. I hit 40-ish mph, around 6k or 7k rpm's, blahhhghghh engine starts clipping and power is gone/dropping.
The rpm's/power steadily decline down to barely idling.
Sometimes the problem goes away. This morning I had to limp to work at 15mph. Another time, I sat in a parking lot playing with idle mixture screw/revving/idling for almost an hour before I could ride.

• Warming up for a shorter amount of time seems to make it happen sooner (SOMETIMES).
• Happens on fresh/full tank of gas, just as much as lower/emptier tank of gas. New gas or older gas, no difference. Seafoam doesn't help.
• Gas tank open or closed, doesn't make a difference.
• Cleaned carbs, installed new plugs, flushed gas. Didn't help.
• Shimmed with 2 washers, helped start-up and increased flat lower-range power band. Didn't help this RPM issue though.

This problem has been happening off and on, since I bought the bike. Happens more often in the winter.

Sh*tty cell phone video. Can see the RPM needle jumping around (always present), and can sort of hear the "clipping" engine/exhaust noise.
https://www.youtube.com/watch?v=MsLs...ature=youtu.be

Thanks guys!

[Motofool]

Air intake or exhaust restriction.

[MrSavvy]

Originally Posted by Motofool

Air intake restriction.

Do you think so?? That crossed my mind just the other day!
I checked my OEM setup and the filter. Everything was clear, but the filter was definitely dirty. I was looking at the Kleen Air delete, guess I should just go that route.

As you saw in the video, I am running a Yoshi slip-on, so I'd assume the air flow is fine on exhaust. I haven't checked the cat though. I'll knock out the intake issues, then check the headers/cat if the problem persists. (if that sounds like a good course of action to you)
I haven't messed with the exhaust on a bike before, just 4 wheeled vehicles, but I ain't scurred.

Side note; Another thing that struck me as a possible indicator of fuel/air ratio is: on decel I get popping/backfiring. No flames, nothing crazy. But it's noticeable.

[jkv45]

Sounds like restricted air or fuel flow to me.

A few things came to mind -

One thing you could do is to drain the fuel from the floatbowl when you start it up and it's running good. Measure (basically) how much comes out. Then run it until you have the problem, shut it off, and check the amount again. Check that both carbs have the same amount of fuel in the floatbowl.

Did you change the float levels when you had the carbs apart?

You could also check the vacuum line to the petcock, and take the fuel line off, apply vacuum to the petcock, and confirm that fuel is flowing out of the petcock at a reasonable rate.

When it starts to run poorly, add choke (enrichener) to see what effect that has.

[alex.s]

i think it would not sound like how he described if it didn't have fuel and spark... it sounds like an air restriction. too much fuel for the air.

[alex.s]

wait a second. the choke is on in that video, you are turning the choke off right?

[alex.s]

Originally Posted by MrSavvy

I haven't checked the cat though.

there is no cat on that bike.

[MrSavvy]

Originally Posted by jkv45

Sounds like restricted air or fuel flow to me.

A few things came to mind -

One thing you could do is to drain the fuel from the floatbowl when you start it up and it's running good. Measure (basically) how much comes out. Then run it until you have the problem, shut it off, and check the amount again. Check that both carbs have the same amount of fuel in the floatbowl.

Did you change the float levels when you had the carbs apart?

You could also check the vacuum line to the petcock, and take the fuel line off, apply vacuum to the petcock, and confirm that fuel is flowing out of the petcock at a reasonable rate.

When it starts to run poorly, add choke (enrichener) to see what effect that has.

Good idea on measuring gas. I'm assuming your idea/s are to show me if it's getting gas flow?
I'll give that a shot if the air intake hypothesis is squashed.
I did change the float levels, but I also re-synced the carbs when I finished.
I checked the petcock in the past, and it appears to be working correctly. Might be worth checking again though after the air intake.
As for choke while running poorly, it causes the bike to start bogging down and almost kills it, when the bike is running really bad. Same as opening the throttle.

I think the air intake would make sense. Because adding more gas causes the problem to worsen.
If I'm adding more gas to the mix, but more air can't be added, that would explain why it runs even more poorly when more throttle is applied.

Originally Posted by alex.s

wait a second. the choke is on in that video, you are turning the choke off right?

The choke wasn't on. I have the idle screw/knob set to idle at around 1k rpm's. The bike idles while bouncing between 1.5k and 2k rpm's lately, though. The needle keeps jumping, as seen in the video.
Choke takes my 250 to 4k rpm's. I leave the choke on very rarely, and when I do, only to the stoplight leaving my small neighborhood.
So yes, choke is off when riding.

Originally Posted by alex.s

there is no cat on that bike.

Ok, I wasn't sure. Lol.

[alex.s]

in the video you posted, the choke looks like its on. are you sure it is all the way off?

[MrSavvy]

Originally Posted by alex.s

in the video you posted, the choke looks like its on. are you sure it is all the way off?

Positive. Chalk it up to my crappy cell phone and shaky hands.

Edit: at 0:99-1:04 you can see the choke lever is almost touching my front break lever.

[alex.s]

oh yeah down is on for that choke. my bad. it's been awhile since i've used a choke... or even had one.

[MrSavvy]

No problem. haha
I'm envious.

[jkv45]

I might pull the plugs and take a look at the color for a confirmation of a lean or rich mixture.

How much did you change the floats? It's kinda tricky to measure, and it's rare that they are far off. I'm now thinking that you may be getting too much fuel (floats set too high), or the carb slides are not lifting properly.

Did you shim the needles? Any chance the needles are not seated correctly? Carb diaphragms looked good?

Have the valves been adjusted lately?

[MrSavvy]

Originally Posted by jkv45

I might pull the plugs and take a look at the color for a confirmation of a lean or rich mixture.

How much did you change the floats? It's kinda tricky to measure, and it's rare that they are far off. I'm now thinking that you may be getting too much fuel (floats set too high), or the carb slides are not lifting properly.

Did you shim the needles? Any chance the needles are not seated correctly? Carb diaphragms looked good?

Have the valves been adjusted lately?

I take it back. I didn't adjust the float height, only cleaned them.
I shimmed the needles less than 2-3mm (see 5th bullet, 1st post). The needles are definitely seated correctly. Of that much I'm sure. haha
Diaphragms were flawless, no tears.

Checking the plugs for color would be worth a shot, good idea. I'll do that first.

[jkv45]

Originally Posted by MrSavvy

I take it back. I didn't adjust the float height, only cleaned them.
I shimmed the needles less than 2-3mm (see 5th bullet, 1st post). The needles are definitely seated correctly. Of that much I'm sure. haha
Diaphragms were flawless, no tears.

Checking the plugs for color would be worth a shot, good idea. I'll do that first.

Post a photo of them if you can.

I'm not sure which direction to go at this point, but hopefully that will help decide.

If you drain the floatbowls, check closely for debris or water. If it's lean, and you get any debris out of the floatbowl, a partially plugged main jet might be a possibility.

[MrSavvy]

Will post back this weekend with updates. No internet access over Thanksgiving.

Happy Thanksgiving guys. Thanks for the pointers.

[Motofool]

Originally Posted by MrSavvy

Do you think so?? That crossed my mind just the other day!
I checked my OEM setup and the filter. Everything was clear, but the filter was definitely dirty. I was looking at the Kleen Air delete, guess I should just go that route.

As you saw in the video, I am running a Yoshi slip-on, so I'd assume the air flow is fine on exhaust. I haven't checked the cat though. I'll knock out the intake issues, then check the headers/cat if the problem persists. (if that sounds like a good course of action to you)
I haven't messed with the exhaust on a bike before, just 4 wheeled vehicles, but I ain't scurred.

Side note; Another thing that struck me as a possible indicator of fuel/air ratio is: on decel I get popping/backfiring. No flames, nothing crazy. But it's noticeable.

According to the behavior based on changes of temperature, it seems to me that your engine is suffering from an over-rich mix after it gets to operational temperature.

Cold engine = lean mix: More mass of air (not heated) and less fuel (part of it condensates on the cold walls of the carb-intake-valves).

Hot engine = Ideal mix: Less mass of air (same cylinder's volume to be filled, less mass of heated air) and more fuel (there is no condensation but vaporization, which helps mixing the liquid into the mass of air).

If a restriction to the flow of fresh air or exhaust gases exists, that ideal mix when the engine is hot tends to be rich and the engine can only breath so much (hitting reduced top rpm's).
That was typical of two-stroke engines that developed carbon deposits that partially blocked the exhaust port.

The exhaust popping suggests eventual occurrence of afterfire.

Copied from
http://en.wikipedia.org/wiki/Back-fire

"A back-fire or backfire is an explosion produced by a running internal combustion engine that occurs in the induction system rather than inside the combustion chamber. Unburned fuel or hydrocarbons ignited from a slower burning, lean fuel air mixture that is still burning inside the cylinder when the intake valve opens.
Not to be confused with afterfire which is caused by an excessively rich fuel air mixture that is not completely burned during combustion. It is then ignited in the exhaust. A visible flame may momentarily shoot out of the exhaust pipe. Either condition causes a popping noise, together with possible loss of power and forward motion."

This is, of course, just a hypothesis.
There is no replacement to checking things first hand, as you can do.

[MrSavvy]

Alright guys, I finally had some time to work on my bike. She's my only ride at the moment so it's hard to make time to work on her.

I took the 250 out on the highway the other day, got up to around 90, and when I pulled off on an exit ramp the loss of power and sputtering kicked in.

I limped home in 2nd @ ~15mph.

Started with diagnostics.

I drained both carbs. Both had the exact same amount of gas in each.
I inspected the petcock. Gas flowed freely in "res" and didn't flow in "on" position. I didn't apply vacuum because I know gas flows when it's "on".

Next I pulled the plugs. They both looked fine. Not black and crispy and not white.

Right plug.
Left plug.

The oxidation and rust forming on the right plug is a bit unnerving. But I did use some plug grease, and the threads are clean, so I have no reason to believe water got into the head.

Again, I inspected the air filter and air intake box/snorkel. There's absolutely nothing that would cause a blockage or decreased airflow. I cleaned the filter and re-oiled it a couple weeks back, for sh*ts'n'gigs.

I've been running CR8E's from NGK. I got the Iridium for the durability. I picked up a pair of CR7E's, at the recommendation of the parts lady at the Kawa dealership.
Running a step hotter plugs might help during the colder weather? But at the same time I'm nervous about burning up my engine on a day that's not as cold. (days range from 35 degrees Fahrenheit to 65 degrees or so, currently)



From here, I'm heavily considering breaking down the carbs again (already did that last year) and inspecting the jets again. Possibly replacing the jets with another set of OEM jets (there's always a chance the previous owners have an aftermarket jet kit installed?).

I also considered doing a compression test. I haven't done one on a bike before, just cars/trucks.

Also, I haven't inspected the exhaust really. Not sure how or if that's needed.

I'm open to any tips, suggestions, advice, anything. Thanks for reading!

[jkv45]

Originally Posted by MrSavvy

Again, I inspected the air filter and air intake box/snorkel. There's absolutely nothing that would cause a blockage or decreased airflow. I cleaned the filter and re-oiled it a couple weeks back, for sh*ts'n'gigs.

I've been running CR8E's from NGK. I got the Iridium for the durability. I picked up a pair of CR7E's, at the recommendation of the parts lady at the Kawa dealership.

Running a step hotter plugs might help during the colder weather? But at the same time I'm nervous about burning up my engine on a day that's not as cold. (days range from 35 degrees Fahrenheit to 65 degrees or so, currently)

From here, I'm heavily considering breaking down the carbs again (already did that last year) and inspecting the jets again. Possibly replacing the jets with another set of OEM jets (there's always a chance the previous owners have an aftermarket jet kit installed?).

I also considered doing a compression test. I haven't done one on a bike before, just cars/trucks.

Have you tried riding the the air filter out temporarily?

A hotter plug might be fine for low to medium rpms, but during extended high rpm running (like highway riding) it may be too hot. Ambient temp doesn't affect plug heat range once you are at operating temp. Plug heat range isn't the problem.

Removing the carbs and going through them again might be a good next step. Replacing all of the brass jets is also a good idea, as is removing the idle mixture screws, cleaning the passages, and looking at the condition of the o-rings. Plan to sync the carbs when you are done.

From what you are saying, I would look at an air or fuel restriction (main jet).

Compression test isn't a bad idea.

Have you checked the valves lately?

[MrSavvy]

Originally Posted by jkv45

Have you tried riding the the air filter out temporarily?

A hotter plug might be fine for low to medium rpms, but during extended high rpm running (like highway riding) it may be too hot. Ambient temp doesn't affect plug heat range once you are at operating temp. Plug heat range isn't the problem.

Removing the carbs and going through them again might be a good next step. Replacing all of the brass jets is also a good idea, as is removing the idle mixture screws, cleaning the passages, and looking at the condition of the o-rings. Plan to sync the carbs when you are done.

From what you are saying, I would look at an air or fuel restriction (main jet).

Compression test isn't a bad idea.

Have you checked the valves lately?

I'm too nervous to drive a car or ride a bike without a filter at all.

Good info on the plugs. I also didn't really think a hotter plug would solve my issues, because this issue pops up in the summer as well. Just not as often.

I'll be tearing down the carbs tomorrow. Depending on what I find, I might go with new jets. Everything I see regarding jet kits is aftermarket and tuning. I can't find much/any info on OEM jet replacement.

I haven't checked the valves, period. I feel like I need to. I swear I can hear a bit of valve chatter, at least more than when I purchased the 250.

I've put around 5k (close to 12k total on the odo) miles on the bike and haven't checked the valves, clutch, or compression. Just upkeep on oil, coolant, brakes, chain, and suspension parts (dust caps, oil seals, fork oil, etc).

[jkv45]

Originally Posted by MrSavvy

I'm too nervous to drive a car or ride a bike without a filter at all.

Good info on the plugs. I also didn't really think a hotter plug would solve my issues, because this issue pops up in the summer as well. Just not as often.

I'll be tearing down the carbs tomorrow. Depending on what I find, I might go with new jets. Everything I see regarding jet kits is aftermarket and tuning. I can't find much/any info on OEM jet replacement.

I haven't checked the valves, period. I feel like I need to. I swear I can hear a bit of valve chatter, at least more than when I purchased the 250.

I've put around 5k (close to 12k total on the odo) miles on the bike and haven't checked the valves, clutch, or compression. Just upkeep on oil, coolant, brakes, chain, and suspension parts (dust caps, oil seals, fork oil, etc).

Running without a filter isn't problem for a short period. I would try it before doing much else. It's just a test to see if it changes anything.

Definitely check and adjust the valves.

I would make sure to get OEM jets and float needles. Aftermarket ones may cause other problems and complicate troubleshooting. Many professional shops that rebuild carbs will automatically replace the brass parts as part of a standard cleaning/rebuild.

[MrSavvy]

Originally Posted by jkv45

Running without a filter isn't problem for a short period. I would try it before doing much else. It's just a test to see if it changes anything.

Roger. I'd have to ride for a couple of days, probably. Since the issue I'm having can be sporadic. But I can give it a shot. I'll just clean out the air box really well, and I already keep a cover on the bike at night when I don't ride.

Most recently, before my post at 1pm yesterday, when the bike bogged down and lost power it didn't regain it. Normally I can let it idle for a while, or let it rest over night and come back and it's good to go. This time it bogged down, limped home, and even a day later it wouldn't crank up and run correctly.
It's just a weird problem to deal with. haha

[jkv45]

Originally Posted by MrSavvy

Roger. I'd have to ride for a couple of days, probably. Since the issue I'm having can be sporadic. But I can give it a shot. I'll just clean out the air box really well, and I already keep a cover on the bike at night when I don't ride.

Most recently, before my post at 1pm yesterday, when the bike bogged down and lost power it didn't regain it. Normally I can let it idle for a while, or let it rest over night and come back and it's good to go. This time it bogged down, limped home, and even a day later it wouldn't crank up and run correctly.
It's just a weird problem to deal with. haha

That would be the time to try taking the air filter out - when you are experiencing the problem. I wouldn't ride it for an extended period without the filter, just stop and take it out while it's not running well.

Not sure that it's the problem, but it might be something that would help you isolate it.

When you say - "it wouldn't crank up and run correctly" it makes me think the battery voltage may be low - in which case it won't crank or run right. I'd check it. Should be 12.7V minimum after sitting for an hour or so after riding. If that's good, check it while cranking. You should still see around 10V minimum while cranking. Also check the battery terminals and grounds.

[MrSavvy]

Just an update; Today I completely disassembled, cleaned, and reassembled both carbs.
I found what looked like crystallized gas deposits on one maybe both of the main jet "holders". I also think one of the main jets was clogged with a little-something.

I'm going over to Fastenal tomorrow morning to see if I can get some stainless bolts to replace these JIS screws. Lowes and Home Depot didn't have the correct lengths of M4x.7.

I'm also going to check my valves before I put the bike back together. My local Kawasaki dealer has a handful of valve shims that they'll sell me when I get the measurements.

I did notice the float bowl gaskets are pretty worn out. That could definitely cause some issues. I'll be ordering two gaskets to replace them, asap.

Lastly, I will check the battery when I have the bike back together. I don't think that's the root of the issue, but it won't hurt to check. I know I accidentally drained the battery (twice?) a year or two back. Charged it back up with my trickle charger and started fine since. But I'll check anyway.

[MrSavvy]

I replaced 90% of the hardware on my carbs with stainless steel hardware. Looks so much better.

I stripped down my 250 and removed the valve cover. I measured the lash on all 8 valves. My feeler gauge reads in the same increments as the one used by Headshrink, in this thread.

As follows;
Intake:
1) .178mm
2) .178mm
3) .205mm
4) .152mm
Exhaust:
5) .203mm
6) .203mm
7) .178mm
8) .152mm

As I understand, exhaust should be between .22-.29. Intake should be .15-.24.
So, technically all of my intake valves are within spec, although #4 is super close to the minimum allowed. And all 4 exhaust valves need new shims.
I'd just purchased 8 new shims, though, depending on price. To avoid having to check my valves again sooner.

Since I've been unable to find anything else wrong with my bike so far, and since the plugs aren't showing rich/lean conditions, I have my fingers crossed for the exhaust valves being the culprits.

Next step is to remove the cams and pull the shims. I'd like to pull both cams at the same time, and measure all the shims in one go. So I can replace all the shims at the same time and button the 250 back up.
I just need to determine the best way to do so. Lining up TDC, using Kawasaki's method, doesn't line up the camshaft lobes correctly. There's always pressure on at least one set of lifters.


Do our 2009 (or 08+) Ninjas come with paint already on cam gears and the main crank (where the 1|T and 2|T are located)? Mine has white paint markings. I was curious if someone worked on my engine prior to me purchasing it.

Thanks for reading! Let me know if anybody has any tips or advice. Thanks



Edit: I'm trying to work through this in my head... if the exhaust valves are outside the allotted specs, that means they aren't closing completely, right? Which would create an exhaust leak. So when gas combusts in the cylinder, part of the ignited gas and combustion process is leaked into the exhaust. Which would explain the popping I hear and would also explain my loss of power. Am I correct, or not so much?

[MrSavvy]

Originally Posted by alex.s

oh yeah down is on for that choke. my bad. it's been awhile since i've used a choke... or even had one.

Originally Posted by Motofool

(...)There is no replacement to checking things first hand, as you can do.

Do either of you gentlemen have any thoughts regarding my last post?

[alex.s]

the intake looks fine. the tight exhaust might have been causing performance issues. the cam gears have markings cast into the metal. they use the same gear for both so they have both markings, the paint marker indicates which markings the cam gear is for (one cam gear will be marked intake, it's on the intake cam- other exhaust, on the exhaust cam) you line up those markings on the cam gears with the case. i don't know what method you're looking up, but just put the crank to tdc and then look at the cam gears.

[Motofool]

Originally Posted by MrSavvy

Do either of you gentlemen have any thoughts regarding my last post?

The way you have been chasing the problem is not the best.

Re-read your posts and list all the things that you have checked or manipulated, without having a final conclusion on any.

I perfectly understand that you have limited experience with these things.
Nevertheless, a step by step testing process is the only way to narrow the actual problem.

You need to test each thing/system until you eliminate any doubt about its proper functioning.
Otherwise, you may introduce new problems that did not exist in the first place, making the proper diagnostic more complicated.

http://faq.ninja250.org/wiki/Troubleshooting

http://faq.ninja250.org/wiki/Intake

http://faq.ninja250.org/wiki/Exhaust

http://www.theyeagergroup.com/2008_n..._clearance.htm

http://faq.ninja250.org/wiki/Engine

I still believe that those spark plugs show excessive fuel in the mix and that your intake and/or exhaust passages are sporadically restricting the flow of gasses/air.

Out of adjustment valves and carbs do not produce sporadic behavior in an engine.
Possible causes could be:
1) Something blocking the intake (rag under the seat, loose part).
2) Something blocking the exhaust (loose baffle, loose noise reducing material).
3) Loose electrical connection at any point of the ignition circuit (more frequent it is the connections to the coils).

Things that can worsen the problem:
1) Valves that do not fully close after the shafts have dilated (low compression = low torque and missing explosions).
2) Excessive level of fuel in each bowl.
3) Dirty air filter.
4) Choke that does not fully close.

Regarding the adjustment of valves:
- Keep journals and bearings of cam shafts matched. Mark each part before disassembling and return it to the same exact orientation and position. When in doubt, take pictures.
- There are two top end centers for one cycle or full rotation of each camshaft. That is why these are 4-stroke engines. The TDC that you need for each cylinder is the one that has all four valves closed. Do not rotate the engine backwards.
- Service your cam tensioner.

Please don't feel bad; we all have been learning and at the point where you are now.
You will resolve the current mystery and your machine will perform again.

[MrSavvy]

Originally Posted by alex.s

the intake looks fine. the tight exhaust might have been causing performance issues. the cam gears have markings cast into the metal. they use the same gear for both so they have both markings, the paint marker indicates which markings the cam gear is for (one cam gear will be marked intake, it's on the intake cam- other exhaust, on the exhaust cam) you line up those markings on the cam gears with the case. i don't know what method you're looking up, but just put the crank to tdc and then look at the cam gears.

Thanks for the info! I did a lot more reading today and see exactly what you're talking about.




And oh man, thank you Motofool. That's exactly what I needed, a bit more detailed guidance on how to go about this.

I understand and am willing to do a step-by-step process. I'm just limited by my current knowledge and how much research I can do.

I'll put off installing new shims for the time being, then. If that's not the cause of my current issue. Like you said, I don't want to introduce new possible issues with per-existing problems too. I've done that with my previous car, replacing my turbo when it wasn't the root cause.

1) I know without a doubt my airbox and under-seat area are 100% clear of debris. I keep the bike clean inside the fairings and I double checked to be sure.
My air filter is perhaps too old or dirty, that's an easy quick thing to replace and knock off the possible culprit list. Aside from replacing my filter, and inspecting my air box, I don't know what else to check on intake. I would assume that's it, because next in the line of airflow is the carbs, which I've pulled.

2) I haven't messed with the exhaust because I'm not sure where to look or what to inspect. How far would you recommend me breaking the exhaust down? Any pointers on where to look? I can go as far as removing the slip-on, unbolting the exhaust from the headers, and inspecting it that way? That's all that comes to mind.

3) This I can tackle! I already noticed the ground for the right coilpack had oxidation on the spade terminal/plug, and was possibly making a poor connection. I'll thoroughly inspect all possible wires, grounds, and such tomorrow.

All of your info is very helpful and I'll continue to read over it as I hop on the right track to diagnosing my 250.

Originally Posted by Motofool

Please don't feel bad; we all have been learning and at the point where you are now.
You will resolve the current mystery and your machine will perform again.

Thanks, man. I hope she'll be back up and running soon. My heart's already aching to ride. heh
I guess I just feel bad for asking for all of this advice and pointers from you guys. I'm sure you have better stuff to be doing than helping me. haha
But then again, I always pass down what knowledge I have in life to people who know less than me about cars/bikes. So thank you for doing the same.

Oh and that's a great tut from 'theyeagergroup.com' thanks! I didn't find that one.

[Motofool]

Originally Posted by MrSavvy

..........

I'll put off installing new shims for the time being, then. If that's not the cause of my current issue. Like you said, I don't want to introduce new possible issues with per-existing problems too........

I would continue on with the shims.
You can only improve any condition by properly adjusting the valves and servicing the cam chain tensioner.

Again, valves that don't fully close get damaged and start a chain reaction of poor performance.
The reason of the gaps is to compensate for dilatation with heat of the shaft of the valves.

At engine operational temperature, each valve should fully seat and close while the gap is minimum (less tapping noise/max opening of the valve and still a safe margin that ensures full closing).
With wear, the gaps only get smaller.

After it reaches the minimum that is recommended by the manufacturer, that safe margin and the tapping noise disappear and the valve starts leaking (fresh mix if intake or hot gases if exhaust).
After leaks appear, the max compression decreases and what is worse, the edges and seats of the exhaust valves can get burned and deformed if the condition persists for some time.

[MrSavvy]

So this happened.
http://oi57.tinypic.com/2002zxy.jpg

I rounded off the head of the first bolt (far left). I was a bit confused, because I know how to correctly use a socket wrench. lol
I inspect the last three bolts, that I hadn't touched yet. I noticed the edges of the bolts were all rounded already. Two possible conclusions; These are some sort of demon bolt from Japan? (as JIS is to Phillips)
Or either somebody has worked on the engine and removed the cam chain guide previously, and rounded the bolt heads then.
I swear, the heads on these particular bolts are so small in comparison to their body. There's hardly anything to grab onto with a socket or vice-grips. Ughh

Anyway, this is what I've been dealing with today and probably won't have all 3 out until tomorrow. I'll probably have to break out the dremel. But even worse, I have to buy new bolts. Probably order online. Having to bum rides from family is the worse. F*ck.

[alex.s]

buy 5x, 8mm socket heads. insure they are 6 sided and not 12 sided as most are. also get some 5 minute 2part epoxy. mix the epoxy up and put some in each of 4 of the 5 8mm socket heads. now place these over the stripped bolts and allow them to cure. once they are cured, remove them with your socket wrench. use one of them at the hardware store to get replacement bolts. use the 5th socket head to install the new bolts using a quarter inch socket wrench. those bolts torque to 14ftlbs

[MrSavvy]

Originally Posted by alex.s

buy 5x, 8mm socket heads. insure they are 6 sided and not 12 sided as most are. also get some 5 minute 2part epoxy. mix the epoxy up and put some in each of 4 of the 5 8mm socket heads. now place these over the stripped bolts and allow them to cure. once they are cured, remove them with your socket wrench. use one of them at the hardware store to get replacement bolts. use the 5th socket head to install the new bolts using a quarter inch socket wrench. those bolts torque to 14ftlbs

You're the man. I was wondering if I could use regular old steel bolts from the hardware store. I wasn't sure if they were stretch bolts or anything.

I'll try your suggestion. Hopefully they break loose. Thanks.

[alex.s]

the stock bolts are brass. just so you break the bolts instead of breaking the threads in the head. don't overtighten. the head is aluminum. so using steel bolts means overtightening will **** up the threads in the head (quicker than you expect)

[MrSavvy]

Originally Posted by alex.s

the stock bolts are brass. just so you break the bolts instead of breaking the threads in the head. don't overtighten. the head is aluminum. so using steel bolts means overtightening will **** up the threads in the head (quicker than you expect)

Thanks for the info, good to know.
I'm skeptical that even 2-part epoxy will give the socket what it needs on the rounded head. Only because I know how tight these bolts are. lol
But I'll definitely give it a shot!

The next option is to use a dremel, cut a slot on the head, and use a flat head screwdriver. Clamp vice grips to the center of the flathead, near the screwdriver blade, and use as leverage to unscrew.
It's worked every time in the past, but I'll have to tape off the engine so metal doesn't invade my head. Just a royal PITA.
It is what is is, though.

[alex.s]

trust me. i've done this several times on those exact bolts on 3 different engines. 2500psi 2 part epoxy. 6 sided socket. fully cured. dont cut. dont spill.

[MrSavvy]

I suddenly find myself convinced. haha
We have a local Harbor Freight. I'm betting they have the least expensive sockets. I know Autozone charges $7+ per single.

Edit: I take it back. Home Depot has singles for less than $4. Score.

[ninjunk]

wait, what? brass? 8mm?

I highly doubt they are brass as it looks like they are rusting. zinc plated steel would be my guess.

They are certainly not 8 mm, they are listed HERE as part number 92154 which is a 6mm x 45

these are pretty common on the jap motorcycle stuff, they stick an 8mm head on a 6 mm bolt (which normally would have either a 10mm hex or a 5mm allen)

why do they do this? i have no idea, maybe it has something to do with the way they torque or assemble them. either way its real easy to strip the head.

you can probably pull them out with a vise grip if you are careful. I'd replace them with a socket head (allen head) screw with a SAE washer. You could replace them with a graded 10mm hex headed bolt, but sometimes its hard to find those in 10.9

the washer is super important. It has to be an SAE washer with a close fit to the shank. a regular washer wont be hard enough.

[alex.s]

Originally Posted by ninjunk

wait, what? brass? 8mm?

I highly doubt they are brass as it looks like they are rusting. zinc plated steel would be my guess.

They are certainly not 8 mm, they are listed HERE as part number 92154 which is a 6mm x 45

these are pretty common on the jap motorcycle stuff, they stick an 8mm head on a 6 mm bolt (which normally would have either a 10mm hex or a 5mm allen)

why do they do this? i have no idea, maybe it has something to do with the way they torque or assemble them. either way its real easy to strip the head.

you can probably pull them out with a vise grip if you are careful. I'd replace them with a socket head (allen head) screw with a SAE washer. You could replace them with a graded 10mm hex headed bolt, but sometimes its hard to find those in 10.9

the washer is super important. It has to be an SAE washer with a close fit to the shank. a regular washer wont be hard enough.

how to tell its not steel: put grinder to it. no sparks means its not steel.

the thread size is 6mm. the head size is 8mm.

why do they do this? because its an aluminum head that has weak threads. they dont want to risk damaging the head so they use brass fasteners which will strip before damaging the head of the engine.

also. what the hell are you talking about with an sae washer and a 10.9 bolt. have you ever stripped the threads out of aluminum? its a bad idea to have fasteners stronger than your threads.

[alex.s]

also.... you don't use zinc plated steel inside an oil bathed engine.