Ski gets a miss help

[cambo au]

so where do i start i have been chasing a problem with my ski for what seems like ever and am now at a loss as to what to try next so here is the story
when i leave the ramp my ski runs ok not brilliant but ok after anywhere between 5 mins to 1/2 hour it develops a miss mid to top in trying to fix this problem i have replaced entire stator,cdi,brand new oem coil,new earth lead also tryed a jumper lead from front cover to neg battery,disconnecting stop switch,my ski did not have dual pulse so i put dual pulse on it ,rebuilt the carbs the only thing i have not changed out is the tbm flywheel
if i disconect a plug lead at a time the rear cylinder always is the week cylinder its like it fouls the rear plug if i put a new plug in the rear it will run ok for a minute then be the same again
i have also changed theo rings in my head thinking my sleeves may have dropped all checked out ok i have also blocked my water lines off and leekdown tested my cylinder and head 100 psi with 0 leekdown so that eliminates orings,waterjacket broken through i did this both hot and cold

i am at my wits end and am at a loss as to what to try next i know every one is going to tell me to try and swap out the flywheel witch i will do this weekend but i just thought some one might have a idea i have not thought of

thanks

 

[Watty]

Hi Chris,

How well is your ski tuned? Just for testing purposes, lean out your top end about a 1/4 of a turn. If it makes a substantial difference, you could chase it from there.

Also, when it starts running like crap, pop off you flame arrestor and test. See if that makes a difference, and also check a few idle to 1/3 throttle blips and see if there's excess fuel leaking into the rear carb through the bombsight. I'm assuming you've already checked the carbs.

Try letting the ski sit on the beach for 15 minutes once it starts running bad, and heck the plugs for small droplets of water.

There's plenty of other things you can try, but thats what I would start with if it was running ok not that long ago.

 

[cambo au]

hey leigh
yeh it was running really on song no water on plugs and the carbs are checked all holding psi no leaky neele and seats
it really feels electrical but i have changed all that but i will try the flame arrestor off next out

 

[OCD Solutions]

If it was electrical you should see the problem in both cylinders. You may have a small internal leak. After everything you have already done, it might be time to pop the head off and have a look inside.

 

[WFO Speedracer]

Have you swapped out the spark plug boots?

 

[madscientist]

mine was doing something similar just before the coil dropped dead

 

[tipafew]

Hmmmm, yeah I would have said coil or CDI, but you have already changed both of those.

 

[cambo au]

brand new coil only done 1/2 hour last ride i have had the head of all looks ok if i had a seal leak it would be lean so i dont think that is it and the head had 0 leak down at 100 psi so it aint orings

 

[tom21]

Hi Chris,

How well is your ski tuned? Just for testing purposes, lean out your top end about a 1/4 of a turn. If it makes a substantial difference, you could chase it from there.

Also, when it starts running like crap, pop off you flame arrestor and test. See if that makes a difference, and also check a few idle to 1/3 throttle blips and see if there's excess fuel leaking into the rear carb through the bombsight. I'm assuming you've already checked the carbs.

Try letting the ski sit on the beach for 15 minutes once it starts running bad, and heck the plugs for small droplets of water.

There's plenty of other things you can try, but thats what I would start with if it was running ok not that long ago.

If I read your response right you just dismissed what was posted here. its asking if your carbs are in good shape its asking if they are properly adjusted. too little or too much fuel could make for a lousy ride. turn some screws and see whats up.

 

[cambo au]

i wrote that my ski was running on song
witch i meant was tunned really well and it started doing this after that yes i have turned screws on the carbs but i did state that i would pull the arrestor when it started doing it witch
at this stage i cant afford to dissmiss anyones advise

 

[Geeshow]

same problem here

 

[OCD Solutions]

Check everything again, you are missing something. These engines are not very complicated at all. Verify your tank is properly vented, make sure you don't have any fuel leaks under the hood, clean all the carb internal filters, blow out or replace your fuel lines, check all ground points, pull the flywheel cover and check for water or oil intrusion. Go back to the basics.

Have you checked/replaced the voltage regulator or trigger coils? Swapped CDI's?

 

[tom21]

water in the tank. may not show up on plugs but it will make the ski run like crap.

air leak? takes a little more time to check but is worth looking at.

you said in the first post the ski ran ok, not great but ok. then it runs like a song. which is it? does it run great or just ok?

I know you said the leak down was good but what is the compression on those cylinders?

 

[tipafew]

Boykid brings up a good one. Check tank venting.

 

[Geeshow]

will check all what you said. new fuel lines and all.