2006 250 HPDI - loss of top end speed

Hey All,
Recently lost cylinder 2 and decided to have both 1 and 2 rebuilt. The tech different pistons that I guess do better under heat. He also had all fuel injectors rebuilt. He has done this same job on several Yamaha's with good success including for my buddy 2 years ago.
I had several issues during and after the break in hours. REALLY rough idle and running overall, burned thru a ton of gas and oil in 2 hours of part of the break-in time, HORRIBLE hole shot (seemed like it took a minute to get on pad) and lost top end speed.

* so, I adjusted the idle and I'm good there now
* replaced plugs since all were fouled which I figured was the cause of all the other problems. (fouled from the heavy lube used for rebuild I guess)
* felt like a shimmy, prop slip or plug missing while running - even after replacing all plugs (kind of felt like running thru current eddy - was on CA Delta with strong current but never felt that before the job was done?)
* Top end speed loss - still not corrected.
* compression matched in both new cylinders at 110 and all other cylinders were at 116-117

Took it back to the tech and he hooked it up to the computer. He said it sounded like a possible coil problem... but, he tested all the coils, injectors and basically checked all motor stats and said EVERYTHING looked good. He suggested to change props (mine had some damaged blades - but was that way prior to losing cylinder), he also adjusted my hot foot (maybe the cable had been stretched) and he said that he noticed my motor bushings were worn and he thinks I may have lost some trim range.

So, here's where I'm at as of running it yesterday on Folsom Lake (CA):

* idles good in neutral and in gear (after adjustment)
* swapped props to non damaged (same prop - Yamaha Ti 25)
* very good hole shot
* very good mid range power
* NO top end - can't get over 60 MPH (5400 RPM max)
* back to normal fuel and oil consumption (been using Lucas oil products)

Anybody ever had the same problem or any Yamaha mechanics out there have any idea's of what's going on?

Also, if I have lost say 1/4 inch of trim range, would this be enough to lose that much top in speed?

Thanks much for any thoughts

Randy

Quote:

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Originally Posted by onewalker

Hey All,
Recently lost cylinder 2 and decided to have both 1 and 2 rebuilt. The tech different pistons that I guess do better under heat. He also had all fuel injectors rebuilt. He has done this same job on several Yamaha's with good success including for my buddy 2 years ago.
I had several issues during and after the break in hours. REALLY rough idle and running overall, burned thru a ton of gas and oil in 2 hours of part of the break-in time, HORRIBLE hole shot (seemed like it took a minute to get on pad) and lost top end speed.

* so, I adjusted the idle and I'm good there now
* replaced plugs since all were fouled which I figured was the cause of all the other problems. (fouled from the heavy lube used for rebuild I guess)
* felt like a shimmy, prop slip or plug missing while running - even after replacing all plugs (kind of felt like running thru current eddy - was on CA Delta with strong current but never felt that before the job was done?)
* Top end speed loss - still not corrected.
* compression matched in both new cylinders at 110 and all other cylinders were at 116-117

Took it back to the tech and he hooked it up to the computer. He said it sounded like a possible coil problem... but, he tested all the coils, injectors and basically checked all motor stats and said EVERYTHING looked good. He suggested to change props (mine had some damaged blades - but was that way prior to losing cylinder), he also adjusted my hot foot (maybe the cable had been stretched) and he said that he noticed my motor bushings were worn and he thinks I may have lost some trim range.

So, here's where I'm at as of running it yesterday on Folsom Lake (CA):

* idles good in neutral and in gear (after adjustment)
* swapped props to non damaged (same prop - Yamaha Ti 25)
* very good hole shot
* very good mid range power
* NO top end - can't get over 60 MPH (5400 RPM max)
* back to normal fuel and oil consumption (been using Lucas oil products)

Anybody ever had the same problem or any Yamaha mechanics out there have any idea's of what's going on?

Also, if I have lost say 1/4 inch of trim range, would this be enough to lose that much top in speed?

Thanks much for any thoughts

Randy

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If he put Wiseco pistons in those two cylinders, then that could be the problem JTM, Stroker guy who builds high performance Yammies, has had a ton of issues with them. They tend to swell with heat and essentially keep the engine from turning higher RPMs. They tore one engine down multiple times and keep re-boring beyond what Wiseco recommended, never could get them to run right. Switched back to Yamaha oem pistons and ran great. Just a thought. You might could try and message him.

Another thing to look at, make sure butterflies are opening all the way up. When I got mine back from Hydrotec, mine had nothing on top end. Turns out the arm that goes to the oiler that has two holes was in the wrong position, so at full throttle it was hitting the stop pin on the oiler keeping it from opening all the way up. Good luck!

Thanks for the info... I will see what pistons he used for sure!! I know he has been using whatever they are for years on several other motors including my buddies, but his 2005 yammi did not have the same problems as mine.. same exact pistons and same 2 cylinders... but interesting about those pistons. I will follow up with him on those as long as having him check the butterflies that you mentioned.

Thanks much for the reply.. much appreciated.

Randy

Does sound like you are running on 5 cylinders. A faulty ignition coil may not show up on computer.

Had the same problem, top speed was only 60, ended up being the throttle cable inside the cowling, whole cable would move while pushing on the hotfoot. The bracket that secures the cable was loose, ended up tightening it up with a zip tie, speed it back up 80mph again! Finally a quick and cheap fix!!! Good luck

I had similar symptoms on my HPDI and it was a bad spark plug boot. Got a new boot and it ran on all six cylinders again. I hope it's something simple for you.

Awesome.. Thanks for your input and prior experience... I HOPE it's a loose bracket or bad boot.. be happy with either one of them!! Keep you posted incase anybody else runs into this situation.

Any one know how to get a hold of Stroker

like to talk with him about wisco piston I had same issue

Most use WSM pistons with good results.

who builds those pistons

HQ office is in NY but as far as where they are actually made idk.

update...
Yes Wisco pistons used..

* Spark plug boots appear to be fine.. no corrosion and all plugs show signs of combustion/usage.
* Cable bracket is secure.

Going to have TPS checked next...

Does anybody know if intermittent sluggish hole shot and no top end speed can be caused by exhaust blow back into the cowling? Someone was telling me that leaking exhaust in cowling might cause symptoms. Would that gag the engine?

Thanks,
Randy

TTT

update - BRAND NEW injector installed today for #2 cylinder due to fouling plugs after few minutes of running. ran boat and still fouling plug.. WHYYYYY

Thoughts?

Well, several things come to mind. New injectors can flood. We had several brand new hpdi injectors tested in recent months and all were flooding. They can be adjusted to flow less. Reed valves can be sticking closed and not allowing enough air...are they original or replacements? Coil or plug wire maybe bad. Run motor in gear on yds to verify or do a spark test. Inspect or replace the spark plug, it maybe bad also.

Thanks Rich... will flooding injectors turn the plug just black and not wet foul the plug?

The reeds are original...tech tested plug wires and coils last month and appeared to be all good, but he does think after talking to him today that it could be a weak coil.. he said it would not be normal since he tested and appeared to be fine, but he felt it could be a concern.. going to either put in another good coil to see if that fixes the issue or maybe swap coils and see if problem follows the coil. I have replaced 4 sets of plugs since October.. seems like #2 is getting too much or too hot or combo of both... it's like I took a black sharpie to the prongs and entire solenoid...all the others have that light chocolate milk color on the solenoid... not jet black.. no build up.. just black. It's crazy!
Thanks for the info.. I will check the coil again..

Mike in post #6 mentioned to check the spark plug boot. The boots have a specific built in resistance and are spec'd for 4k-6k ohms. The boots easily unscrews from the wire and can be checked for resistance end to end. Should take about 5 minutes. I replaced one of mine that measured 56K ohms.