Ninjette suddenly won't idle/run properly...

[infinitethrill]

So, on the way to the parents garage with stainless steel brake line in bag to be installed, the bike all of a sudden starts running very strange, less than a mile to destination. Pulling away from stop stalls the bike. I have a K&N filter on the carbs, dan moto slip on, jet kit (running 110 main jets and needles shimmed up twice. Anyway, I get it to chug and I make it to garage. The bike will idle weakly and will go up and down on its own, and with some throttle will slowly rev up with a intermittent popping sound that would make the airfilter and carb shake. I got gas about 5 miles earlier, but made the distance with no problems.

Unrelated, but back when I was installing the jet kit and pulling the airbox, I took it for a run one exit down the freeway. Sure enough, at the very bottom, it wont start. That ended up being the carb that was loose in those rubber grommets between carb and engine creating a vacuum leak leaning it out. Fixed that after a 2 hour push up a hill at midnight. This is not the same issue however.

Pulled the fairings, and inspected the slides in the carb. Everything looks okay. Took apart and sprayed everything down with carb cleaner. Engine is making suction and sounds okay when being turned over with no carb attached. Carb back on the bike, with no air filter again tried to turn it over. Found the issue: the slide on the right side (didn't run it long enough to check the left) is bouncing up (almost like its vibrating very fast maybe) and the gas is igniting inside the carb with little pops of flame. This I assume isn't good. Everything is hooked up okay aside the K&N filter at this point. the raspy air intake noise I got when installing the K&N filter is the part that sounds distorted, along with a popping exhaust when bike stalls, but general intake sounds strange.

Ideas of where to go from here? the jets are not clogged, all that was cleaned out. Jetting and Idle mixture screws adjusted around 4000 miles ago, and have had no issues since.


Edit: here is a Video of the popping I just saw.
http://f.cl.ly/items/233U0f1I0S3q1S0q2Y0w/IMG_0849.MOV

Thanks for the help everyone!

- Billy

[jmgrande]

Try changing your spark plugs. Just a suggestion.

[infinitethrill]

Originally Posted by jmgrande

Try changing your spark plugs. Just a suggestion.

I pulled one spark plug shoe and then the other and tried turning over, didn't run better/worse/either way... Did the spark plugs back with valve job 5000 miles or so ago. Still suction from either side of engine when you cover the inlet with the palm of your hand. Don't have spark plugs till tomorrow but will definitely try.

[jmgrande]

Originally Posted by infinitethrill

I pulled one spark plug shoe and then the other and tried turning over, didn't run better/worse/either way... Did the spark plugs back with valve job 5000 miles or so ago. Still suction from either side of engine when you cover the inlet with the palm of your hand. Don't have spark plugs till tomorrow but will definitely try.

I only have about 700 miles on my bike and the sparks plugs **** the bed. I just figure it's worth shot for under $10. And don't forget to gap them!

[cbdallas]

I can't even remember anymore...does the petcock on the new gen have a "prime" setting? If so, you can drain the tank with that by removing the line to the carb. But since you just filled up, it might actually be quicker to take the tank off and dump it.

[jmgrande]

Yeah, it's in the left side of the bike. You have to remove the black side panel to see it.

[infinitethrill]

I know how to drain the gas... How can I use a soda pop bottle for gas, what do I do with the vacuum line in that situation? before I dump $20 worth of gas...

[infinitethrill]

New Video: http://cl.ly/0P1f0j1p2514150r0j0n

So tonight, got back to work on the bike, basically left it as it was popping in the first video. Started it up: ran fine. cool. blipped throttle. great. took a quick spin up street and back: nice. went back to garage and gear up for a trip outside the neighborhood. all seems well up to this point, when I am about to leave neighborhood under a bit of load it started making an almost bubbling like noise with pops on the throttle when I gave more gas. Back to the garage with the same issue as last night. damn.

Took out the carbs, removed air filter, opened float bowls and drained, floats look okay, then removed the tops of the diaphragms and took out the diaphragms springs and needles, pulled apart all jets and sprayed with carb cleaner, and disconnected all hoses... checked operation of everything. everything looks okay. reassembled, and as always have a hell of a time getting the diaphragms back in place. some time in the freezer and vaseline to make it not pop back out did it. again, bike fires up and runs well, and then has issues. I haven't related it to the warm up period either, warm and cold it exhibits the same issue. I connect the throttle to troubleshoot. under any load (going up a driveway at lowish RPM's) it will get bad with the popping. It pops on certain speed throttle openings, and still as far as I can tell only igniting in the right side. bike stuttered and died and did not make reliable power at all. But just a minute ago without being altered it ran me around the neighborhood fine.

Gas: still using the same gas here. Gonna find a place to dump the whole tank, and then refill as I continue this testing. it came from the pump at 76 where I always get gas...anyway always good troubleshooting, but I don't believe this will fix it. The valves were done late at 18,000 miles, by myself. two previous owners before the bike was 8300 and they didn't say anything. clearances were low but definitely not closed. bike is now 23,500 ish. I work during the day so for the past 3 days I've only been able to look at the bike between 9 and 12pm, and its my only ride. Is the next job really draining the oil pulling the head and inspecting valve operation and lash? It could be something to do with a valve stuck open or closed, but I have no idea if this could even be related. plz help guyse? I miss riding already!

by the way all the california emissions systems were stripped off and plugged over 9000 miles ago so I doubt that would be a problem.

[infinitethrill]

any help guys? there is some stuff online about preignition but it all refers to when the fuel is already in the chamber, but not much has come up about it happening in the carb... can't work on bike tonight, but tomorrow will be at it from 6pm and on. Just want to know if anyone has heard of anything like this before.

[KELPHYN]

As you said in your OP, it ran fine BEFORE you filled up and you have done everything BUT change the gas. HMmmm. If you have some hose and a jar/bottle, make temperary gas tank with good gas and try that. Drain carbs again too. Just plug the vaccum hose with a bolt or something. Put one end the hose in the jar/bottle of gas,(make sure that end stays submerged) connect the other end to line that goes to the carbs. Keep the jar higher than carbs. You will have make sure you gas flowing from jar first.Try good gas first before tearing more stuff apart. Water in gas can do some weird things to passages in the carburator. Maybe even a little methelhydrate in the good gas wouldn't hurt either.

As to the popping, worse case scenario you have an intake valve sticking open, but if that were the case it would be doing it every time that cylinder fired. If it was lack of valve lash it would get worse as the engine got hotter.

My bet is still on bad gas. Keep us posted

[infinitethrill]

Tested with known good gas. Same issue. As always, jumped right on the bike and sped up and down the street. The bike will act like a normal cold bike and once warming it will exhibit these issues. Day 4 of troubleshooting, I finally get the genius idea of using my phone camera to see whats going on in my carb. Check the videos -

Here is the carb popping issue.
Vid 1: http://cl.ly/1b2Y0L070W2I1I1Q3a3T

Here is the sloppy idle issue. Now I know its sparking even at idle: not the carbs.
Vid 2: http://cl.ly/021i2f2I2b0d1y0K3N1u

This is staring down the venturi. FIRE!!!
Vid 3: http://cl.ly/2C2Y2A3y1Y3S1w0e211h

so yeah. Tomorrow morning getting set to pull the valve cover and turn everything over to observe performance? Make sure the valve clearance is okay. If any tolerances are out of speck adjust by replacing/filing down shims. how do I inspect the actual valves, and is it necessary? I will post throughout the day if issues arise... is it possible this is a spark plug issue and is switching the plugs to opposite sides and firing up the engine to test or is this definitely a valve? anyway yeah will be working on it soon so this will be updated.

[KELPHYN]

Okay not the gas. I'd say the best clue is that it doesn't really start till the engine starts warming up. As you valves heat up the stems get longer (heaty expansion) decreasing the amount of clearance between cam follower(bucket) and the camshaft lobe. If there is not enough initial valve clearance the bucket stays pressed against the the cam, never completely closing. Hense when the cyclinder ignites it fire back through the intake valve.When your are checking your valves pay extra attention to the intake valves on that side, probably are tight. Could be just one, could be both. Be sure you check all the valves and adjust any if you have to. You got it all apart anyway. Keep us posted to your findings. Fingers crossed that's it.

[choneofakind]

That's a backfire. That's not good.

Check your valve clearance, plugs, ect.

Link to original page on YouTube.

[infinitethrill]

So, currently have the head open. Started with the feeler gauges and thought I had come across something when the 2 right intake valves were completely closed. A quick turnover to 2T quickly resolved that however. There is nothing out of speck with the valve clearance tolerances there. About to pull the plugs to see if thats an issue.

I have seen photos of the valve it itself online, but not sure how to open the engine further to inspect that. All google seems to know about is the valve adjustment...

[choneofakind]

http://www.ninjette.org/forums/showthread.php?t=9787

[infinitethrill]

This is what I am looking at. Valve lash is okay on all valves afaik. Spark plugs look okay.

One bucket removed in photo, that is the right intake valve...



once you lift the buckets and the shims, how do you get at the actual valve? right now everything looks okay, not sure of whats next...


edit: reading service manual. need to pull the cylinder head to inspect valve seat. man this is a big job, lol

[KELPHYN]

Is that one bucket deformed or is it just a reflection?

What actually were your valve clearances?

intake should be no less than 0.0059 in (0.015mm)

and no more than 0.0094 in (0.24mm)

If you have any less than the minimum clearance, adjust. Taking your word you have done it right.

Ideally you would like to be halfway between the minimum and the maximum, around 0.0076 in (0.195mm)

Even if you getting close to the minimum clearance I would adjust them just encase.

[KELPHYN]

One way you can check for a leaky valve is reinstall cams and install the one spark-plug. Then turning the motor over by hand, listen to the intake side. As you go through the compression cycle, you would hear hissing back through the intake if a valve is leaking. If your not sure what you are hearing, try it with the side you're not having problems with to see if there is a difference.

But then you don't have the problem till the engine is warm so not sure if that would help. Do you know what a cylinder leak down test is? Have the equipment or know someone does? Then you could run the bike till it does it, quickly do the test add see if it's a leaking valve.

You say your plugs are fine? Both about the same color? Unless the one plug is showing signs of running really lean, can't see you having a burnt vavle or seat. Then if they are really black you could have carbon build up, which can cause preignition from hot spots when the intake valves open.

Really hate speculating and putting to many ideas out there when I'm not doing the work myself.

[infinitethrill]

Talk about roller.


Engine in a crate...


The Ninja 250 is hella light.



Tuesday work will resume. and yeah, I have done the valve jobs before, and all is still up to spec. Both plugs are the same color. I have a jet kit that I tuned myself. I know the mixture was correct across all throttle openings. Everything points to intake staying open (damaged valve). Might even get everything ported while its open...

[choneofakind]

Originally Posted by infinitethrill

Might even get everything ported while its open...

yes! hey, if it's already off the bike, you might as well

[gilmorec61]

Wow man, crazy stuff...

[KELPHYN]

Keep us posted. Pictures of what you find if you remember and if it is a valve try to determine what caused it to fail so it won't happen again. Good luck

[KELPHYN]

One other thing to check before you pull the head is to look really at the intake manifold and carb boot for cracks that would open as the engine warms up causing a vaccum leak.

[infinitethrill]

Originally Posted by KELPHYN

One other thing to check before you pull the head is to look really at the intake manifold and carb boot for cracks that would open as the engine warms up causing a vaccum leak.

2'nd paragraph of my first post, vacuum leak... lol It's not the same issue...

[KELPHYN]

I knew that, just meant to take a closer look, hate to see you pull the head if you don't have to.

Also noticed you said you have a service manual. Maybe look up the proceedure for checking the coils.

just having hard time thinking you have a damaged valve if the plugs aren't showing any signs.

[jmgrande]

I still think you should change the plugs.

[infinitethrill]

So yes, it is a stuck open intake valve. A small amount on the exhaust on the same cylinder too.



Cylinder walls seem okay.



Some carbon buildup is apparent. Going to switch to a smaller main jet.

New head gasket comes in on tuesday and will be installed, then engine back in the bike and a complete reassembly.

[KELPHYN]

Good job on tracking problem and sifting through advice and only taking what you needed. Update us when your up and running again.

[infinitethrill]

So, follow up. Taking the very last cylinder head bolt out was lame. It was submerged in oil at the time, and the allen key was already starting to strip. This was the last bit that I needed to open the head myself to inspect the valves and piston. Dropped the engine out of the bike for the first time (now that was quite the experience) and dropped it off at my friend's Honda shop where they removed the stripped bolt and did a leak test. Yes, an intake valve on the right cylinder *was* leaking. Before trying to pull the head did a valve lash check and everything was okay. So it ended up being carbon bild up holding the intake valve open on that side (also an exhaust on the same side and an exhaust on the other side, however those were minor. They removed the valves and cleaned the carbon off. Everything was sealed up with a new head gasket and new bolt. The shop recommended a cylinder hone and new rings (just as maintenance). Engine is at 23,000ish miles... Not in my budget at my current moment. Anyway got the engine back after 2 weeks and got the cams and timing correct and redid a complete valve job. 2 intake valves on the bad cylinder were at something like .20 instead of .22. I changed 6 shims, 2 were okay and everything was perfect. Sealed it up and mounted everything back where it belonged on the bike, reattached everything. Pressed starter. It fires up after 20 seconds of cranking (this bike has new fluids) and after having a choppy idle for the first 15 seconds or so began to purr away. Sweet! Revved it up a bit, response was perfect. Topped off the fluids again, threw on a helmet and rode up to the top of my street and back. Ran up to 60mph totally fine. Back the driveway, I go to take my gear off when the idle suddenly gets weird again, and when revving the throttle just slightly and anything more the carb began popping again. After 8 solid hours of work doing such an intensive project, one I thought was fixed, has just returned again. What else could possibly be the culprit now? I wish I had known good parts I could just swap one at a time, but no. Sucks to go so long without transportation too. Thanks for all the help too, definitely helped with ideas on what to diagnose and such.

[KELPHYN]

That totally sucks. Thought you had it. You sure the valve is no longer sticking? Did your friend pull the valves and check the faces and seats when he cleaned up the head? Did he lap the valves in when he reassembled the head?Can you friend do the leak test again, while the engine is warm? If yes, the only thing to look at now is ignition. Did you put in new plugs? What plugs are you running? You have a shop manual? Read trouble shooting section starting on page 16-32. Maybe swap diodes from one side to the other and see if problem switches to other cylinder. Then try same thing with coils. Anybody else with 250R you could try their IC ignitor?
Don't know what else to suggest.