Engine Teardown and Rebuild

[Rustitution]

Originally Posted by Midnight_tinkerer

As the rings are not jammed on no'2 piston, the material that was bouncing around in the chamber, has probably lodged itself under a valve causing your loss of compression.

I was hoping that was the issue but it doesn't look like it I got a big c clamp and made a jig out of wood that would let me compress the springs and get them off Screw specialty tools, its better just to make it your self and save MONEY.

So I got the valves off here is the head with the valves off

Cylinder 1 Exhaust Valves


Cylinder 2 Exhaust Valves


Cylinder 1 Intake


Cylinder 2 Intake


So from what I see all the valves need a good lapping I will post the pictures of the valves themselves but the intake ones have really nice defined seat edge so they wont need much in the terms of lapping the exhaust ones have some carbon build up. So that will need some attention.

[Rustitution]

Ok on to the valves themselves lets start with intake side

Intake Valve Cylinder 1





Cylinder 2





They seem to be fouled up around the stem but the seats are clean the flash didn't give the shine I was expecting but oh well. Any tips on cleaning the stem. I have an ultrasonic cleaner that I use for carbs would you recommend something like that and then a mild lapping?

[Rustitution]

Ok now Exhaust

Cylinder 1




Cylinder 2




The stems look cleaner I'm assuming because its gas flow vs atomized liquid on the intake side but the seats have some solid carbon deposits. what ever I do with the intake valves I will do with these and then address the seats.

[fast1075]

The exhaust valves look bent to me. Partial face seal, partial carbon. If so, there is your major loss of compression.

While not always feasible for a hobbyist, the correct diagnostic for loss of compression prior to engine tear down is a leak-down test. The test identifies the amount of blowby, and whether it is going into the crankcase (piston/ring/cylinder), leaking head gasket, or leaking intake or exhaust valves.

Best of luck, at least the head does not look to be trashed.

[Rustitution]

Originally Posted by fast1075

The exhaust valves look bent to me. Partial face seal, partial carbon. If so, there is your major loss of compression.

While not always feasible for a hobbyist, the correct diagnostic for loss of compression prior to engine tear down is a leak-down test. The test identifies the amount of blowby, and whether it is going into the crankcase (piston/ring/cylinder), leaking head gasket, or leaking intake or exhaust valves.

Best of luck, at least the head does not look to be trashed.

Yeah I wasn't thinking before I tore it down but I don't really have a good setup to do a leak down test. As I have discovered earlier I'm doing this more for educational purposes. I got my certification a few months ago but don't have access to a shop to continue to hone these skills so a full top end teardown and rebuild I figured was good practice, and since I'm replace almost everything I'm guess what ever the issue is will be resolved.

As for the bent valve Everything looks true to my eye it could just be my camera. non of the valves stuck and came free easily so I'm hoping all is well.

[Ninjinsky]

As a crude test try rolling the valve shaft along the edge of a table and see if the heads run true or if you have a wobbler.
TBH I haven't seen any thing so far that would result in serious compression loss.
No stuck valves in the first set of pics, no broken rings, the head gasket did not show signs of blowing
Without going back I recall you said valve clearances were within spec.

My gut reaction is still that this was not a major fault internally but something peripheral.
Do you actually have the compression figures the workshop got or was it a word of mouth thing?

Looking close up at the 'dings' they do look very like a loose plug electrode gradually getting "hammered" straight.

[Rustitution]

Originally Posted by Ninjinsky

As a crude test try rolling the valve shaft along the edge of a table and see if the heads run true or if you have a wobbler.
TBH I haven't seen any thing so far that would result in serious compression loss.
No stuck valves in the first set of pics, no broken rings, the head gasket did not show signs of blowing
Without going back I recall you said valve clearances were within spec.

My gut reaction is still that this was not a major fault internally but something peripheral.
Do you actually have the compression figures the workshop got or was it a word of mouth thing?

Looking close up at the 'dings' they do look very like a loose plug electrode gradually getting "hammered" straight.

Yeah it is all very odd, the only thing I could see was the score on the cylinder wall. The valves were within spec, that electrode getting hammered did some surface damage and you can see it actually damaged the top of the crown of the piston. and some carbon build up on the valves So I'm hopping by addressing all the issues that I will be in the clear.

New Rings, New Gaskets, Cleaned head and pistons, carbon in the exhaust valves reseated etc. new plugs, fresh gas and viola that should do it.

I bought the bike from a close friend of mine (used to be roommates) and he didn't get any paperwork from the shop. The shop is down the road so I'm sure I could get any paper work or maybe I recollection. The took it their because they thought it was a carb cleaning so the guy cleaned the carbs and then it still didn't work did a compression test and found cylinder 2 with no compression. I don't know if it was 0 compression or just low compression.

It has been a fun project though so I have that going for me.

[Ninjinsky]

I think we agree here.
Also you may want to consider getting the workshop to briefly run a ball hone through the barrel just to glaze bust it and give your new rings a cross hatch to bed in to.

[Rustitution]

I did that already just a quick hone to get some cross hatch and then measure with my caliper and they were still well within spec so here's hoping. just waiting on a few parts now will try to clean the head and valves this weekend and start to put it together. Bikebandit is taking it's sweet time getting me my parts

[fast1075]

Cylinder is tapered and barreled. You need a good set of snap gauges and a dial indicator to check accurately. There ARE calipers that measure that finely, but they are not the tool for the job, and are QUITE expensive.

I have a set of Mitotoyo calipers that I bought years ago that CAN measure to .0001, but calipers are not capable of measurement other than at the very top and very bottom of the bore. And the very top of the bore (above the top ring) does not wear at all (the part you CAN measure with a dial gauge).

Anyways, you seem curious enough and stand to learn something good.

Ans if there was NO compression on one cylinder, the piston/cylinder is not badly enough damaged to completely lose compression, but a couple of whacked exhaust valves COULD. I'm sticking with my bent valve theory as the major culprit.

[Ninjinsky]

Cool. I didn't read the whole thread in detail, my bad.

Looking forward to hearing this kitty purr again

[zhuuka]

Originally Posted by Rustitution

The took it their because they thought it was a carb cleaning so the guy cleaned the carbs and then it still didn't work did a compression test and found cylinder 2 with no compression. I don't know if it was 0 compression or just low compression.

It has been a fun project though so I have that going for me.

To answer that question, his had low compression when the mechanic got it running.

[Rustitution]

Cool thanks Z as you can see I've been busy lol

[zhuuka]

Originally Posted by Rustitution

Cool thanks Z as you can see I've been busy lol

Yeah man, didn't take you long to tear the thing apart, lol.

[Rustitution]

As I told you off line I am just waiting for bike bandit to ship me my dang parts to get this thing put back together

[Alex]

Fun thread!

[garth285]

Big bore kit... big bore kit... big bore kit.... lol

[Rustitution]

Originally Posted by Alex

Fun thread!

Thanks Alex, parts should be arriving tomorrow or Wednesday and then the fun really begins. and by fun i mean cursing and trying to figure out what i did wrong on the rebuild.

Originally Posted by garth285

Big bore kit... big bore kit... big bore kit.... lol

haha this is a budget rebuild and the only pig more kits I found are for the new gen 250 and the timing chain channel are different so it wouldn't work without serious modification. at least that is my understanding. but again budget rebuild.

[Midnight_tinkerer]

The best thing I have found for cleaning carbon off valves is a wire wheel on a bench grinder. Cleaning carbon from the ports is a little harder. I use a small flat blade screwdriver to scrape the majority of it out. Then proceed to sand the exhaust ports with wet & dry paper or a Dremel with a sanding cylinder. It's messy & time consuming. I try not to sand the inlet too much as it is best to leave the surface rough cast. But I try to polish the combustion chamber & exhaust port, to slow carbon build up and to reduce surface area to minimise heat absorbtion. Every now & then I spray some carb cleaner, which helps dissolve some of the carbon.

Better still, find somebody with a caustic hot wash bath.

Those inlets valves are very dirty. This may be from the engine spending too much time at low rpm. Just another reason to keep the revs up.

[Rustitution]

Originally Posted by Midnight_tinkerer

...Those inlets valves are very dirty. This may be from the engine spending too much time at low rpm. Just another reason to keep the revs up.

Thanks for the input I was thinking something along those lines. the previous owner did not do much riding and kept the RPM's to a minimum so that explains that.

As for an update on the build I did the exhaust valves the other night with some fuel tubing and a brass brush and some WD40 they came out good. should be doing the intake ones tonight and lapping the valves. My gaskets and rings will show up tonight so this weekend I can commence on the rebuild. and with fingers crossed get this baby running.

[cuong-nutz]

Originally Posted by fast1075

The exhaust valves look bent to me. Partial face seal, partial carbon. If so, there is your major loss of compression.

While not always feasible for a hobbyist, the correct diagnostic for loss of compression prior to engine tear down is a leak-down test. The test identifies the amount of blowby, and whether it is going into the crankcase (piston/ring/cylinder), leaking head gasket, or leaking intake or exhaust valves.

Best of luck, at least the head does not look to be trashed.

It does look like bent exhaust valves but then again it could be just the poor focus, angle, and flash skewing the appearance.

Those are some nasty build up on the intake side. Very dirty air filter. I've had good luck with soaking the heads in a bath to remove carbon build up. The casting flaws on the intake and exhaust ports are absurd! Glad Kawasaki inproved QA for the later models.

[M42]

oooops wrong thread!

[Rustitution]

so the gaskets I received happened to be the wrong ones ... yay fun times. more waiting.

[FvnnyL3tt3r1ng]

Bump

[Rustitution]

So its actually funny you bumped the post, I spent all day sunday putting the engine together, and all day yesterday putting everything back in the bike. got her all wired up and lubed up, but the fuel isn't flowing, and I won't go into details but I think the petcock is frozen, I need to drain the fuel and put in some new gas, but the gas cap lock is also frozen so hopefully it spends a nice portion of the day in the sunlight. and then she will be good to go.

[garth285]

Wd40 will help!

[Rustitution]

sprayed that into the lock this morning, I know the gas is at least a year old so I just want to replace it so I'm starting with the cap then will check with the petcock once i get the cap situated, hopefully i don't need a new petcock or cap for that matter.

[ninjunk]

This is a cool thread, good pictures and great writeup, thanks for posting.

I just wanted to add, that when you lap the valves, any bent-ness will show up real quick.

The carbon buildup could be from not having them adjusted and having them hang just a tiny bit open, scorched and blow by. It doesn't take much not-sealing-ness to loose compression, valves are real touchy that way.

I'm not positive, but in theory you might see excessive wear around the base circle of the camshaft from the follower riding it all the way around. That would be one indication the valves were hanging.

[ninjunk]

If you look in the upper corner of this picture



you can see on the cam lobe that the slightly darker line that indicates where the cam was rubbing the follower, continues dark and at the same width all the way around the cam. If the valve clearance was correct, i'd expect to see that line show up dark on the lobe face, but get lighter where it wraps around the back side of the base circle.

Its hard to tell from the pictures, but seeing a dark stripe that was consistent color and width all the way around would tell me that the follower was riding with spring pressure instead of closing and coming off the cam. Given the design of this system, i'm guessing this is an incredibly common occurrence, and a theory of why these bikes have a lot of cold starting and 'carburetor' problems.

[ninjunk]

whoops, i broke the internet.. sorry y'all

[Rustitution]

haha my stupid high resolution images always getting in the way, and that is a good point. reguardless I had to readjust all the spacing on all of the valves after reassembly, now they are all dead center within spec .04-.06 on intake and .05-.07 on exhaust. crossing fingers. I miss placed one little baggy and it had the rear wheel nut and the chain tensioners in it so I need to get that sorted, (ordered a new set off of flebay $28 shipped not to bad) but after that she should be on the road again.

[Rustitution]

Alright update time, I'm starting to get stumped. I put the entire thing back together and checked it twice. I now have compression in Cylinder 2, but now it just cranks and wont start. So I first checked fuel, and it was getting fuel but I used some started fluid, better but still not turning over, air box looks good I didn't do anything to it but it looks clean, pulled the plugs and the spark was kinda weak, pulled the trigger and ordered a new battery and plugs (won't hurt right) got them this week set up the battery and let it charge on low to 24 hours. put it in the bike, started to get this popping sound (had no exhaust on so I am thinking that what it was put on the headers no it sounds like it is trying to run but its not, not even on started fluid. I'm so confused.

[Rustitution]

one question for those who have done this when reinstalling the heads you need to rotate the crank till 2T meaning cylinder 2 is top dead center, is there a wrong side where 2 is top dead center, meaning could the spark be firing in the exhaust phase? I couldn't find anything that indicated that could be an issue but I'm just clearing some thoughts in my head

[juliusmichaelhonrada]

Originally Posted by Rustitution

one question for those who have done this when reinstalling the heads you need to rotate the crank till 2T meaning cylinder 2 is top dead center, is there a wrong side where 2 is top dead center, meaning could the spark be firing in the exhaust phase? I couldn't find anything that indicated that could be an issue but I'm just clearing some thoughts in my head

The ignition timing cannot be changed its fixed in the flywheel , and the marks 2T are accurate unless you broke your flywheel.

You will only see the marks IN/EX line up once every 2 rotation of the crankshaft or every two 2t marks

[juliusmichaelhonrada]

Before i tear my engine down , can you give a brief meaning of honing and lapping , im familiar in removing the camshaft , timing and clearances , what i am worrying about is that is there any special way to remove the cam chain guide because pieces might fall into the crankcase? Or it is straightforward?

Im also having the exact same problem , my cylinder #2 is misfiring and im suspecting low compression because of the black plugs vs the brown plugs of cyl#1 and i switched ignition coils and spark plugs but still the problem is #2 , im also suspecting bent valves because the previous owner set the timing relative to 1T , and he switched intake cam to the exhaust cam

[Mohawk]

Originally Posted by Rustitution

haha my stupid high resolution images always getting in the way, and that is a good point. reguardless I had to readjust all the spacing on all of the valves after reassembly, now they are all dead center within spec .04-.06 on intake and .05-.07 on exhaust. crossing fingers. I miss placed one little baggy and it had the rear wheel nut and the chain tensioners in it so I need to get that sorted, (ordered a new set off of flebay $28 shipped not to bad) but after that she should be on the road again.

Where did you get those valve clearance numbers ? Unless something changed, they should be .08-.13 inlet & .11-.16 exhaust !

Your numbers are too tight & they won't seal when the big is hot.

[sickopsycho]

Are you sure the top compression ring was not broken? As in you measured the ring gap before removing it from the cylinder? It looks an awful lot to me like the top compression ring broke, causing foreign material in the cylinder (the ONLY way those marks on the head could have gotten there) and causing that streak down the side of the cylinder. That would explain all of the symptoms, including your loss of compression. Great thread, though. Excellent write up, I'm curious to see how it ends up. =)

[Mless5]

So how did this saga end?