Yamaha 150 TRXC vibration issue

[Psalm 99]

Looking at the pics from the mechanics manual, I couldn't find a reference for just purchasing the seats alone. With something of this quality, it seemed like the seats could be removed and replaced. The pics from Boats.net on this website don't mention a needle valve seat. Probably something real simple that I'm just missing. Figure I'm probably going to feel like an idiot.

[99yam40]

I did not realize any carbs came without replacable seats.
Maybe you are right.

not sure if 600 is fine enough, but if it held fine after then you must have trash in there now keeping it from sealing off/

[boscoe99]

There are no replaceable inlet valve seats. If the needle valve fails to seat either the valve or carburetor body will have to be replaced.

[Psalm 99]

Thanks, I'll try to fix what I've got, otherwise I'm looking at a pretty expensive part.

[TownsendsFJR1300]

flooding carb is washing out carbon and oil from cylinders and exhaust.

+1 ^^^. The carb needle is hanging up (or not sealing) and flooding the engine. Inspect the float as well and make sure that's NOT leaking and does indeed "float".

It's also very possible the crankcase is now full of fuel...Pull all the plugs and spin the motor over(pull the safety clip to kill the spark). If you have an air compressor, some spritzs of air will help dry it out...

Rodbolt posted previously how to repair the needle seat, IF THAT'S leaking. (I forgot-do a search)
I don't know if you can replace the seat itself..

If the needle is hanging up for some reason, re-check how it attaches to the float. There's often a very small spring between the two...

With that flooding, I would at least pull that carb NOW and check that needle/seat etc. You don't want a hydraulic lock and destroy the engine..


Also, that mix will NOT hamper starting of your engine, (it simply flooded).
I've run that mix in my 600cc bike and couldn't tell the difference(running/starting wise)

[Psalm 99]

Engine sat overnight and starting work this morning. Plan to pull all carbs and do a complete cleaning job. Good thoughts on flushing out engine before trying to start again. My fault on flooding engine, should have known better but never happened before. Did find that the oil intake was set a little on the high side (pump lever arm about 1/8" above seat with engine off). I'm thinking that even the small amount of the RF solution I got through the engine really began a good cleaning process if the black sludge out the exhaust is any indication.

[Psalm 99]

Success! As suggested, I left the RF solution in the carbs/engine overnight. Main problem appeared to be leaking needle valve seat(s) in #3 carb. Priming engine in morning revealed tight valve seats and no leakage. Applied pressure to priming bulb for a few minutes to be certain leak was fixed. Removed plugs all of which had varying degrees of black gritty stuff. Disengaged spark as recommended and turned engine over a number of times. Turned water on to muffs and started engine using recommended RF solution. Ran engine at about 1800 rpm for about 5 minutes then increased engine speed to 2100 rpm where the vibration had been noticeably worse. Engine vibration did increase and engine speed would vary between 1900 - 2100 rpm. With time (about 30 minutes), engine vibration became noticeably less and engine speed slowly increased without throttle adjustment to 2300-2400 rpm. Backed off throttle to 2100 rpm and let engine run for another 15 minutes until about 4 gallons of Rf solution fuel had run through engine. Placed engine in idle (750 rpm) for a few minutes and shut down. I'll leave the RF solution in the carbs overnight again then run a little fresh gas through the engine but, at this point my problem appears to have gone away and the engine has never run so nicely. I am grateful to this Forum for their good direction. Hopefully, this experience the recommendations received will help others with similar problems.

[TownsendsFJR1300]

Success! As suggested, I left the RF solution in the carbs/engine overnight. Main problem appeared to be leaking needle valve seat(s) in #3 carb. Priming engine in morning revealed tight valve seats and no leakage. Applied pressure to priming bulb for a few minutes to be certain leak was fixed. Removed plugs all of which had varying degrees of black gritty stuff. Disengaged spark as recommended and turned engine over a number of times. Turned water on to muffs and started engine using recommended RF solution. Ran engine at about 1800 rpm for about 5 minutes then increased engine speed to 2100 rpm where the vibration had been noticeably worse. Engine vibration did increase and engine speed would vary between 1900 - 2100 rpm. With time (about 30 minutes), engine vibration became noticeably less and engine speed slowly increased without throttle adjustment to 2300-2400 rpm. Backed off throttle to 2100 rpm and let engine run for another 15 minutes until about 4 gallons of Rf solution fuel had run through engine. Placed engine in idle (750 rpm) for a few minutes and shut down. I'll leave the RF solution in the carbs overnight again then run a little fresh gas through the engine but, at this point my problem appears to have gone away and the engine has never run so nicely. I am grateful to this Forum for their good direction. Hopefully, this experience the recommendations received will help others with similar problems.

Excellent and thanks for the details...Please let us know how the on the water test works for you..

I run RF regularly in EVERY gas machine, (truck, bike included) I own. Reg mix unless there's an issue.

Many folks are skeptical of "snake oils", but as you've seen (and your improvement is more than I would have expected), it does work...

Using it regularly and a stabilizer (not cheap) but IMO, is well worth the preventive maintenance aspect, lack of later issues, etc, is well worth it.