2001 injected 250

[Dr1532]

I know this issue has been posted many times, but have not found any fixes, i have twin injected 01 Yamaha, the port engine is worse than the starboard. when throttling up stumbles and shakes like you could not believe, transferring from the 4 to 6 cylinder change, everything has been changed, linked& sync, injectors, cleaned, vst filter changed , 02sensor changed tps changed . it is not as bad if the motors are trimmed up. but still has an issue. some times i have to pull the throttle back and hammer it to get it to run on 6 cyl. runs fine at idle and when it is running on all 6. my brother has the same engine and his transfers with out an issue, he runs 93 octane me mid grade. I imagine that it is the computer that controls this , could it be a wiring issue (ground) ????
or a computer issue, it has become a true pia, and i want to get it fixed . thanks

[DennisG01]

You'll get some more informative answers, I'm sure, but have you drained some fuel out of the VST tank to check quality?

A suggestion... it sounds like you're throwing a lot of parts ($$) at it in "hopes" that it will get better. Maybe it's time to take it in to a Yamaha tech?

[Dr1532]

it went to a Yamaha tec, they did the injectors, , syc the links, tps, 1300 hundred later for both motors. he wanted to do a leakdown test, not with my money, in other words they did nothing as even though the injecters were a tad dirty according to the paper work , they did not need cleaning. the fuel is fine

[DennisG01]

Well, ground issues can often be a culprit of many things. The good thing is that it's relatively easy to check - just inspect, clean and reinstall all of the grounds, starting at the battery. You certainly don't need 93 for that engine. I run 89 (it's all that's available where I am, otherwise I would run 87). But I also ALWAYS add Startron and RingFree - those are two things I won't compromise on.

I'm sure some others will chime in with more advice, and possibly something more specific - especially in regards to your question about the ECM, as that I can't speak to.

When is the last time the engines have been de-carboned? Not sure if that is the problem, just asking.

[Dr1532]

they were decarboned in the spring, i use ring free faithfully, not a fan of star tron at all but it is my opinion, I am curious if I start off trimmed up high the issue is not so significant as if they were trimmed back. a friend of ours has this same problem in one of his, he is going to look at it in the spring

[DennisG01]

I'd like to hear an expert's opinion on this, but it seems as though if trimming the engine up reduces the problem, then the issue is not with the ECM. My first thought, just thinking out loud, goes to a mechanical connection such as an electrical connection that gets stressed in such a way when the engine tilts that it makes a better connection. So maybe start your ground/electrical search in areas such as that. Everything attached on the engine side should be void of stress if the cable clamp (where all the cables/hoses enter the lower engine cowl) is attached properly... I think... correct?

BUT, could it be something with a fuel (injector?) vs gravity issue? Don't know... maybe I'm stretching on that one.

[99yam40]

it went to a Yamaha tec, they did the injectors, , syc the links, tps, 1300 hundred later for both motors. he wanted to do a leakdown test, not with my money, in other words they did nothing as even though the injecters were a tad dirty according to the paper work , they did not need cleaning. the fuel is fine

Rodbolt may chime in if you post model #s of your motors.

Seems like leak down test would have been the 1st thing to do on any motor to make sure all is well before sinking money into them.

Just how much is 1300 hunderd?

[Dr1532]

the reason I would not let him do a leak down test is because the hone marks were still in the cylinders a year ago , and the motors had the same problem, I have done my fair share of leak down tests and would have done it myself if i felt it warranted doing, I have read alot of post here and other sites, this problem is not uncommon. not sure what you meant by 1300

[rodbolt17]

very FIRST thing I would do in my shop is spark and compression test, leak down is ok on a two stroke as well. doesn't take long.
but if that cyl,even with hone marks, cannot seal all else is a waste of my time and your money.
has anyone monitored CDI output voltage? fuel rail pressures? spark plug cap resistance? fuel lift pumps?

basic stupid stuff but it will bite you.

[Dr1532]

pressure was done, aswell as caps, not cdi output thanks , that will be tried, i have a yami, oem serv manual is it in there ??

[99yam40]

i have a yami, oem serv manual is it in there ??

Yes it is in there, but you do need the proper test equipment to get the readings to compare to manual specs.
A DVA adapter with a regular DVM will do.

not sure what you meant by 1300

You are the one that wrote 1300 hundred, and I was asking what you meant by that

[Dr1532]

i paid 1300 to supposedly have the engines fixed.

[99yam40]

Apparently you still do not realize what you wrote.
1300 is thir**** hundred

But 1300 hundred is a strange number.
thir**** hundred hundered
I was just jacking with you