2006 YAMAHA 90TLR WILL NOT IDLE ...PLEASE HELP!

[ovrclkd]

My '06 Yamaha 90TLR will not Idle in NEUTRAL. It sounds like its running lean. misfires and quits. Once I put it in gear it's "OK". I have rebuilt the carbs, soaked the parts in a gallon can of carb cleaner, blown them out with air, new gaskets etc. It ran fine before putting it away two years ago so I figured it was bad gas or ethanol based crud somewhere. The fuel pumps rebuilt, filters clean, fresh gas in a new tank. The timing is on, sync & link perfect etc. I am at my wits end with this so if anyone has had a similar issue I would LOVE to know what the remedy is. It WILL idle with the center carbs fuel enricher lever in the "Get Home" OFF position. (though it's pretty rough) I have worked on all my Yami's for years (especially the 3 cyl 70 & 90) and cannot figure this out. Thank you for any input and replies. JR

 

[nayborbob2]

I bought a 1986 70 yamaha and it had sat 2 yrs. I did about the same stuff you did but I could not find diaphrams for fuel pump so I replaced the whole pump. I soaked my carbs but rubber parts were in ok shape (including float needles) so I reused them. Did you check float height? I tried to run engine before soaking carbs and it only ran on one cylinder. I took out the spark plugs and they confirmed 2 cylinders were not even getting fuel! I think you have a fuel delivery issue. Maybe double check the needle valve settings? That and float height are about all there is to check/mess up. I guess it runs good at power under load also?

 

[JKTrevecca]

I'm no expert so take this advice as worth what you paid for it ;-)

If you'll take a propane torch and open the valve w/o lighting it, then hold it in front of each carb with the engine running, you'll be able to isolate which carb/cyl (s) are causing you problems at idle because the engine should smooth out with the propane gas going into that carb/cyl. Clear as mud? If the engine idles noticeably better with the propane torch allowing propane to enter one cyl, you'll know that cyl has a fuel delivery issue at idle.

Did you replace or at least flush out and clean the fuel line and primer bulb? If not, any old gas that is gummed up and/or has trash in that was left in the bulb/lines could have been pumped into your freshly cleaned carbs. I just re-built the carbs on my 90hp after they were re-built professionally 3 months ago. I was skeptical of the carbs being the cause of my issues but they were. I think the carbs on these things are ULTRA sensitive to dirt/trash/gumming up.

Good luck!

 

[robert graham]

My 1999 Yamaha C90 has always run great but a while back it quit idling right, so I removed each idle mixture screw, taking notice of each screw's turns out from lightly seated....sprayed carb cleaner into each jet opening and replaced screws....idles great now!...just like before....maybe some trash in that idle circuit?....

 

[ovrclkd]

Thanks for all the replies guys ... I am going to try the propane trick though I DID put my hand over each carb throat to narrow one down. It didn't seem to matter. I am wondering if the fuel enricher valve on the center carb is the culprit? I'll try the propane thing and if I don't blow the cylinder head off will post the results ... actually I'll definitely let you know if that happens

 

[ovrclkd]

Hi .. sorry for the delay but I tried propane in the carbs ... didn't narrow it down to one carb. It still coughs and quits in neutral at idle. Do you think the starter assembly "needle" thing on the center carb is the culprit? I can tell you it gets hot to the touch. When I start it the engine races as it did before and then drops down to 7 -800 rpm then coughs and quits like its really lean. This seems to be a common issue from what Ive read and heard. Someone must know what causes this.

 

[ovrclkd]

Hi .. sorry for the delay but I tried propane in the carbs ... didn't narrow it down to one carb. It still coughs and quits in neutral at idle. Do you think the starter assembly "needle" thing on the center carb is the culprit? I can tell you it gets hot to the touch. When I start it the engine races as it did before and then drops down to 7 -800 rpm then coughs and quits like its really lean. This seems to be a common issue from what Ive read and heard. Someone must know what causes this. Question, can I remove the plugs hiding the low speed needles and adjust them without damaging the carburators?

 

[erniefish]

Yes you can , and should remove the plugs, if you can ,get some left handed drill bits , try them, no matter what ,start very small, near the edge, increase size till you can get a pick/ small screw driver in there. Those screws need to be removed to complete the cleaning, also check bypass valves, I had a bad batch on a v6, chased my tail for days till I figured it out , good luck

 

[99yam40]

Apparently you did not do a very good job of cleaning the carbs if you did not remove the pilot screws.
They need to come out to clean all of the passages

 

[ovrclkd]

Thanks erniefish, I appreciate the "intelligent" reply. Being this is my first encounter with carbs where the low speed screws were not visible and capped I wasn't sure how to proceed. I'll follow your advice on removal. Hopefully this resolves it. JR

 

[ovrclkd]

Yes you can , and should remove the plugs, if you can ,get some left handed drill bits , try them, no matter what ,start very small, near the edge, increase size till you can get a pick/ small screw driver in there. Those screws need to be removed to complete the cleaning, also check bypass valves, I had a bad batch on a v6, chased my tail for days till I figured it out , good luck

erniefish ... I did as you instructed and it fixed the problem, the engine purrs like a kitten even at 600 RPM! It actually idles better than it did when new.
I found the top pilot screw was out by only half a turn so I pulled them apart,cleaned everything (again), set the needles at 1 1/2 as a baseline then turned each one in till it coughed then back out a 1/2 turn.

Thanks so much for the insight and everyone's replies, it's nice to have it running so smoothly.

​Jay R.