chone's engine saga

[choneofakind]

So the other day, my engine decided to stop running. Mid ride. I got it to fire up on one piston, and backfiring and sputtering at 25 mph, limped 5 miles home and shut the bike off asap.

My first thought was the headers. Bought some high temp rtv and sealed them. Not the cause. Then I noticed that one header was hotter than the other. So I decided to check the basics: fuel, spark, and air.

problem found very quickly!!! Spark plug popped out. While this was weird, the engine (that I could see) wasn't damaged, and the spark plug was intact. So I double checked the gap, and put it back in. It turns out, it was only running on one piston because only one plug was in (duh) and the excessive engine noise was from the gaping hole that the plug used to be in. The backfiring was from the fuel mixture getting pumped out that same hole, and the spark plug setting it off right there. Problem solved! or so I thought...

Today, I got my first test ride after replacing the plug. Worked fabulously, albeit with an uneven idle that I equated to not being up to temp. About 3 miles from my starting point (i made a loop) it blew the plug out again. I shut off the engine asap and pushed it about 1.5 miles home. ugh. @alex.s , we are now brothers in arms. Bike pushers for life. That was a better workout than running 1.5 miles

Now, my worry is that the threads in the head stripped, allowing the plug to blow out. That is thankfully fixable. The shop can bore it out and replace the threading with a threaded sleeve that is welded in, which = $$$ ok, I can live with that. However, my largest worry is that the engine is damaged, because the electrode on my spark plug is currently slammed all the way down (no clearance) and I know it was gapped properly when I re-installed it. (I double checked it.

What causes an engine that has never given any issues whatsoever to suddenly start contacting the plugs violently enough to blow them out of the head, even though they're correctly gapped and torqued?

Anyhow, the bike is headed to the shop. I don't have the tools or time (2 jobs, 7 days a week) to take off the head and inspect. I also would rather have an expert check it out. Pardon my lack of decent internet connection, I would update everyone when I can. In the mean time, thank god that my parents got another cage for the summer so that I can get back and forth from my jobs (bicycle as well).

Everyone has that interesting motorcycling story, and this one appears to be evolving into mine. I just consider this a rite of passage, and a minor annoyance. I hope paying for this work doesn't blow my track day allowance. Thankfully, this bike is my fun toy, and will always be my learning tool and I'm not depending on it for transportation. I think with the right attitude, I can learn a lot from this.

[Motofool]

Yes, that is weird.

Hope the thread in the head is OK.

Best!

[Alex]

I don't think you need to even weld it. It's a perfect application for a helicoil.

[alex.s]

isn't it a great workout? up hill is even better.

[Jiggles]

Originally Posted by choneofakind

Everyone has that interesting motorcycling story, and this one appears to be evolving into mine.

Crashing is easier

[csmith12]

Noooooo!!!!!!!!!!!!!!!

[Jono]

Well that is just the worst!


When did you change the spark plugs last?? Did you strip the threads? I always turn the new sparkplug counterclockwise to get it to seat in the threads. <--If that makes sense. Then turn clockwise. Boom, never strip the threads.

Maybe it just rattle loose over time and ruined the threads. Idk. Kinda weird.

I would have done the helicoil like Alex said before ever taking it to a shop. http://www.popularmechanics.com/cars...repair/4212608 A shop will never touch my ninjette.

[davenay67]

Originally Posted by alex.s

isn't it a great workout? up hill is even better.

It's a Ninja, it weighs like a buck-fifty. Try pushing a litre-bike wighing closer to 500lbs. That, my friend, is a workout..!!

[davenay67]

Originally Posted by choneofakind

What causes an engine that has never given any issues whatsoever to suddenly start contacting the plugs violently enough to blow them out of the head, even though they're correctly gapped and torqued?

You don't necessarily have piston to plug contact here. The compression generated by the engine is enough to blow a plug out that has a weak / damaged thread.

I would determine if the plug or the head has thread damage to start with. Can you swap the plugs around and try again. A helicoil will fill a damaged thread in the head.

I know you are busy with 2 jobs and all, but I have found that I have only truly learnt to repair something when I did the repair myself. Or at least was there when a friend helped me repair it.

[cbdallas]

I've never heard of this happening to a Ninja, but it's a well-documented problem with the early 2000's Ford F-150 4.6 V8. They've had a LOT of heads deforming in the area of the spark plug - essentially the spark plug hole gets out-of-round, and becomes unable to hold a spark plug. It's either that, or a spark plug was over-torqued at some point, or perhaps cross-threaded, and the head can no longer hold onto it. A helicoil will be your best bet for a fix.

[alex.s]

Originally Posted by davenay67

It's a Ninja, it weighs like a buck-fifty. Try pushing a litre-bike wighing closer to 500lbs. That, my friend, is a workout..!!

the ninja weighs close to 400lbs. and i have pushed a 550lbs bike up hill for 3 miles in cali summer heat.

[csmith12]

pm sent

[greg737]

This has happened to other EX-250s. Here's a thread on another forum that is very similar to what happened here.

http://forums.ninja250.org/viewtopic...12aeb57b5de367

And here's a How-To that details how you would fix the problem with a Helicoil Insert.

http://faq.ninja250.org/wiki/Helicoi...park_plug_hole

[csmith12]

Will the helicoil fix hold up to track punishment?

[greg737]

Originally Posted by csmith12

Will the helicoil fix hold up to track punishment?

Properly installed, yes.

The Helicoil is high-quality steel and when installed in the aluminum head material it's stronger than the surrounding metal.

Here's a quote from the Helicoil FAQ I referenced in my last post:

The helicoil does make a stronger than stock hole, though; the BMW factory used to helicoil all their plug threads.

[alex.s]

helicoil... great and all for fixing the damaged threads... but why were they damaged? why is the piston slamming into the plug in the first place? bandaiding the effects of the problem does nothing to fix the problem.

my vote is on a $300 engine swap. any issues with the new engine can be resolved using stuff from the old engine.

dave made a good point about compression being enough to blow out the plug from bad threads, but that ignores the fact that the plug was obviously contacted (impailed electrode tip) those dont bend from compression. they bend because the piston hits them. the piston would only hit them if the piston is floating around in the cylinder (broken connecting rod), or the piston has something on the top of it, adding to the height, and thats what hit the plug, or the plug itself is too long or incorrect.

so i think either, incorrect plug, broken connecting rod, shattered cylinder internals, broken valve thats floating in the cylinder, or maybe just some random crap in the cylinder

regardless, i think you wont know for sure what the issue is until you open the cylinders up

[greg737]

Re-read the original post.

He was able to ride it again after re-installing the spark plug. Yes, the engine spit the plug out again after 3 miles of riding but this re-install ride does serve to prove that the engine is still intact (with the exception of some sparkplug threads).

I don't think the piston hit anything. Just bad threads, possibly chewed up by crossthreading and further weakened/softened by the heat of combustion gasses that normally can't get up into the sparkplug threads.

[Kygirl]

My bike had a bad habit of spitting out plugs for a while as well (only spat out the right cylinder and usually at high rpms on the highway.) I finally torqued my plugs down to the exact spec in the manual and haven't had problems recently. Sounds like yours will be a more complicated and costly fix. =( Hope you get it sorted out in time for your track day!

[csmith12]

He will or he can ride my 250. I am not gunna let him miss this.

[alex.s]

Originally Posted by greg737

Re-read the original post.

He was able to ride it again after re-installing the spark plug. Yes, the engine spit the plug out again after 3 miles of riding but this re-install ride does serve to prove that the engine is still intact (with the exception of some sparkplug threads).

I don't think the piston hit anything. Just bad threads, possibly chewed up by crossthreading and further weakened/softened by the heat of combustion gasses that normally can't get up into the sparkplug threads.

tell me how his spark plug tip was impacted then. im assuming it was still attached to the plug wire which is how he still had it, which means it shouldnt have hit the ground or anything that would cause that kind of damage. if it hit something else along the way it surely would have shattered the fragile brittle porclean. are you saying that compression impacted his spark plug tip?

and as far as the logic of "it ran for 3 miles before dying again... it must be good!"... im not even going to begin to explain the problem with that.

[FrugalNinja250]

Stripped plug hole in the head from previous over-tightening. It doesn't take much, especially if reinstall an old plug without a new crush-washer. For a piston to hit the plug would require the kind of internal engine damage usually associated with fire and structural metal pieces grenading in all directions.

[alex.s]

Originally Posted by FrugalNinja250

Stripped plug hole in the head from previous over-tightening. It doesn't take much, especially if reinstall an old plug without a new crush-washer. For a piston to hit the plug would require the kind of internal engine damage usually associated with fire and structural metal pieces grenading in all directions.

all im saying is a blown out plug doesnt have its tip impacted. a plug that has been hit has its tip impacted.

and there very well could be plenty of damage to the engine internals without fire and explosions immediately. the engine has barely been run since the problem started. what happens when he puts the plug back in with a helicoil, and the piston hits it again, but this time shatters the plug instead of blowing it out. now you've got a busted up plug getting crunched arouund in the piston. the fact is that it needs to be inspected. to blindly assume its OK is a horrible idea and a great way to potentially ruin an engine that isnt dead yet.

you dont need to split the engine to do a basic inspection. pull off the headers and look at the valves. crank it over by hand with things off so you can see the individual phases and hear each part working. if theres a problem its usually pretty obvious

[choneofakind]

Update: I called the shop. Stripped threads = $$$$$ I decided that I'm going to do as much of the labor as possible instead of paying someone else to do the stuff that I'm able to do.

so what my dad and I decided was a reasonable attack was
1) take off the head, take the head to the shop, have them install a helicoil. This way I'm paying for as little as possible, and have a trusted machinist do the work necessary to fix the boo boo

2) buy a used engine.\ and get it up to snuff with parts from my current engine. Maybe not the cheapest option, but still an option

note: both these options are just assuming that there is nothing wrong with the engine besides stripped threads that will no longer hold the plugs in place during compression. If other things are damaged, option 2 will look better, but will also take longer to find the right engine.

Originally Posted by alex.s

isn't it a great workout? up hill is even better.

It made me really regret making fun of you for so long. Karma I guess.

Originally Posted by csmith12

Noooooo!!!!!!!!!!!!!!!

I know right!!! It couldn't have been a worse time either! I pm'd you back. Working on it.

Originally Posted by Jono

I would have done the helicoil like Alex said before ever taking it to a shop. http://www.popularmechanics.com/cars...repair/4212608 A shop will never touch my ninjette.

Trust me, they were installed right when I changed them 3k miles ago at the same time as my valve adjustment. I did the same procedure of turning them CCW and making sure they don't strip. Funny thing is, the distance from my house to where it blew the first time is about the same as from my house to where it blew on my test ride after re-installing the plug. Sooo that means something changed recently.

Originally Posted by greg737

This has happened to other EX-250s. Here's a thread on another forum that is very similar to what happened here.

http://forums.ninja250.org/viewtopic...12aeb57b5de367

And here's a How-To that details how you would fix the problem with a Helicoil Insert.

http://faq.ninja250.org/wiki/Helicoi...park_plug_hole

Thanks for the reading. It's much needed research for me. I'll start on that.

Originally Posted by alex.s

helicoil... great and all for fixing the damaged threads... but why were they damaged? why is the piston slamming into the plug in the first place? bandaiding the effects of the problem does nothing to fix the problem.

my vote is on a $300 engine swap. any issues with the new engine can be resolved using stuff from the old engine.

dave made a good point about compression being enough to blow out the plug from bad threads, but that ignores the fact that the plug was obviously contacted (impailed electrode tip) those dont bend from compression. they bend because the piston hits them. the piston would only hit them if the piston is floating around in the cylinder (broken connecting rod), or the piston has something on the top of it, adding to the height, and thats what hit the plug, or the plug itself is too long or incorrect.

so i think either, incorrect plug, broken connecting rod, shattered cylinder internals, broken valve thats floating in the cylinder, or maybe just some random crap in the cylinder

regardless, i think you wont know for sure what the issue is until you open the cylinders up

That's also what's been bugging me. I think I'm going to have to open it up anyways. I'm going to do what I can to get the costs down so that the shop is literally only doing the machining to install the helicoil. As far as I know, the valves were all in really good shape as of my last adjustment, and nothing was damaged. Either way, I'll get a chance to open her up and see what's going on before I pay for work.

edit: after I convinced myself to not part out this bike and buy a new one with the money from it and the money I'll be making this summer (gotta pay for books somehow) I decided that it might actually be fun to learn how to take apart my engine. I mean, that's one of the things I've never touched on my bike before. I learned about carbs by playing, and adjusting the valves was really easy compared to what I thought it would be, so I guess this is just the next thing right??? I have 25 days and as little money as possible to get this fixed so I can get out at mid-ohio with csmith12!!!! challenge accepted. Reading about helicoils ho!

[choneofakind]

option 3 that I just thought of:
a lightly used head; just swap some parts with my engine.

since it looks like I'm going to be removing the head either way, might as well ask my noobie questions now.

Can I remove the head without removing the entire engine?

How do I remove the head? I am willing to start loosening bolts and learning as I go in an attempt to try something new, but not without some guidance first.

If I remove (potentially replace) the head, I will need a new head gasket for when I re-install it, correct?

[alex.s]

you should remove the engine first. even if you dont need to, it will make your life much easier. grab a teardown guide, they have pretty good instructions. i wouldn't bother buying any parts or anything until you've opened it up and know exactly what the damage is

[choneofakind]

so get a service manual, and then remove the engine and go from there? What all is included in removing the entire engine?

Anyone know where I can get an official Kawasaki service manual for the 250R? I've read some reviews that say the official ones are loads better than the Hayes manuals.

[alex.s]

plugs wires off, radiator and water pipes off, exhaust off, carbs off, disconnect the starter, the case ground, the oil pressure sensor, the stator and pickup coil, the case vents and emission vents, the chain, the clutch cable. then put a jack under it and put a tiny bit of pressure up on the engine then take out the engine bolts. lower the jack slowly

[choneofakind]

That sounds do-able, even though it will be a lot of work. I haven't taken off the radiator or water hoses yet, but I was planning on changing coolant anyways.

I can get to the carbs and exhaust tonight. I'll figure out the radiator and water hoses over the weekend hopefully. I might need my dad's help on the engine part though. Thanks dude.

[etiainen]

Get a new bike!!!!!

Newgen!!

Sorry to hear that your booger green baby is daiiiid.

GL getting things running!

[alex.s]

honestly the engine comes out pretty easily. you can have it out in an hour if you are in a hurry.

[FrugalNinja250]

Originally Posted by alex.s

all im saying is a blown out plug doesnt have its tip impacted. a plug that has been hit has its tip impacted.

All I'm saying is that for a piston to reach a plug generally, in the engines I've built, either a connecting rod has let go, or something broke off the piston. In any engine that runs without banging, clanging noises it is not physically possible for a piston to hit a plug. Hell, in the engines I'm familiar with the piston edges will hit the cylinder head long before it comes close to the plug, and of course once it hits the head it stops, meaning it will *never* come close to the plug.

Basic engine knowledge sure is handy to have...

[alex.s]

like i said- give me a reason for how the plug electrode was contacted and ill shut my mouth.


maybe youll say something like "it hit something on the way out"... well, thats speculation isnt it? the point ive been trrying to make is that we dont know the problem. it needs to be examined. it could be simple. it could be complicated. but neither of us know, and noone will know until the engine is open. ive had shards hang around in 2 stroke cylinders just bouuncing arouund causing more and more damage until i opened the head and took the **** out. yes the engine still ran, but it was completely ****ed up inside. compression took a **** even though the engine still ran before and after the shard was removed. the fact is that we DO NOT KNOW. so speculating that its fine is one thing, but encouraging someone to ignore problems and simply "roll it back up the hill and try again" is foolish in my opinion and will lead to disaster.

[EMSRacer07]

Originally Posted by alex.s

like i said- give me a reason for how the plug electrode was contacted and ill shut my mouth.


maybe youll say something like "it hit something on the way out"... well, thats speculation isnt it? the point ive been trrying to make is that we dont know the problem. it needs to be examined. it could be simple. it could be complicated. but neither of us know, and noone will know until the engine is open. ive had shards hang around in 2 stroke cylinders just bouuncing arouund causing more and more damage until i opened the head and took the **** out. yes the engine still ran, but it was completely ****ed up inside. compression took a **** even though the engine still ran before and after the shard was removed. the fact is that we DO NOT KNOW. so speculating that its fine is one thing, but encouraging someone to ignore problems and simply "roll it back up the hill and try again" is foolish in my opinion and will lead to disaster.

From my engine building experience and my little experience with the little 250 engine. I could say that if the threads are completely gone the plug could have traveled down further than in its installed position and that could have been enough to have the piston give it a smack.

[Jono]

@choneofakind Don't get a new bike because of a minor mechanical problem.

These engines are super easy to remove from the bike. I was a total newbie when I swapped my entire bike to a new frame then back to my old frame. Didn't even have a service manual or anything. It really is simple. You are mechanically inclined, right?

If the helicoil doesn't do the trick look into getting a new used engine. They can be bought for very cheap.

Good luck with everything! You can do this!

[greg737]

Honestly, there's too much "noise" in this thread for me to even hope my voice will be heard...

But, yes, the plug tip being bent in is exactly the same result that the guy in the other thread I linked to had. In the end he found a dent in the bottom of his fuel tank and it was decided that the plug (still in its plug-lead wire) had bounced off the bottom of the tank and re-impacted on the camshaft cover. He put in a Helicoil and the engine ran great. End of story.

[loz944]

I have built many engines over the last 28 years from simple single cylinder 2 stroke to high performance Porsche engines .
the chances that a piston can actually strike a plug is very very remote unless

a. the engine has been highly modified very rare

b. the wrong plug has been installed ie to long a reach but reading the op that's not the case

with a four stroke engine if the piston lets go the con rod you are far more likly to have it bend a valve

in my opinion the plug hit something after it blew out ie rocker cover etc

people need to stop scare mungering and give genuine advice


for example turn the engine over by hand with the plug back in and you will feel or hear if there is any contact

remove head fit a helicoil and have a good look in the engine

[flynjay]

Originally Posted by choneofakind

Can I remove the head without removing the entire engine?

It is easier and will take less overall time to remove then engine first. It is not really that hard.

At the minimum you need to remove the head to check for any damage to the piston. You do not need to remove the drive chain just take it off the front sprocket.

[csmith12]

I am a total n00b at wrenching on bikes but had my engine out in less than 2 hours while having a few brews and taking pics along with way for my build thread. Do it! It's not hard at all.

[etiainen]

I think putting it all back together was more annoying.

Lol.

I think getting a jack to borrow was the most amount of work.

[alex.s]

yeah make sure you have a floor jack. trying to get it back in without one is damn near impossible unless you're big and muscley or have 2 helpers