Timing??or something else??

[hunter3001]

Hello. iam new to this site but iam in great need ...i have a 40 yamaha[4 stroke}My motor shut off a few weeks ago ,after been going for about 10 minutes...i coulnt get it going again ..well we blamed it on a head gasket gone and water got in on the piston and plugs! ,why I though that, was the morning before this happened I was using the motor and it wasnt getting its water correctly because it was a cold morning,but i didnt notice it till about an half hour forsure later of atleast half trottle.So i just waited for a few minutes with the motor shut off ..than when i started it the ice i guess had melted from the heat of the motor and it began to get its water correctly ...so I used it the rest of the day and never had a problem,but like i said next day i had trouble, we sent it to a yamaha shop and they put a new gasket on it ,we got it back and after a long long time of priming and picking i got it going, so i took it for a test run and as soon as i gave it some trottle..it would pop and sputter and to keep it going I had to release the trottle,but when you got past the poping and gave it full trottle it was great till you slowed down again. than we thought it wasnt put on timing correctly by the yamaha shop..so we had to take it off again send it back, than got it back again ..still the same!!! ....they say its on timing correctly..but i doubt it cause I moved her timing belt a cog one way and it would be over the poping but than it wouldnt have no power at full trottle. work great at slow speed. So now the yamaha shop says they dont know whats wrong!!!Any advice??

 

[rodbolt]

Re: Timing??or something else??

time to find a shop that trouble shoots rather than replaces parts. you have 4 major subsystems that all must remain happily married or its trouble in paradise. the block mechanical subsystem including the ability of the head and head gasket to seal. the intake system to include the valve train and carbs the ignition system which lights the fire and the exhaust system that includes the exhaust part of the valve train and the flow of burned gasses out the prop. so now if I were a real tech here is where I would start. do a leakdown test first. its quick,easy and will identify any mechanical problems with cyl sealing and tell me if its rings,valves(also which valve) or leakage of gases into the cooling system. wow I just confirmed or eliminated 1 out of 4 subsystems in 20 min.next I will hook up my s-48 spark tester and test for spark. this will only confirm if the parts are capeable of making spark not nessasarily its occurring at the proper time. for that I need a timing light. wow anothjer 20 min and I have confirmed or eliminated another subsystem. now its time to check carbs for debris, water or misadjustments. see where I am leading? diagnostics is the easy part. just do it as subsystems. could be its a technician induced failure due to improper cam installation that bent a valve. could be a lot of things. time to confirm or eliminate subsystems. a compression test for this is a teat on a boar hog.

 

[hunter3001]

Re: Timing??or something else??

wow!!!!!!I think thats way over my head!! i dont have the tools for that job ..i dont think!!!thank you anyway!!There is nothing i can check to see what the problem is ??If i cant solve it atleast i could find out whats the problem!!seeing i live out in the country i dont have a lot of shops to pick from!!haha Thanks anyway

 

[rodbolt]

Re: Timing??or something else??

without at least a timing kight there is not much you can do. if you have a timing light make sure the cam belt is on correctly and check the timing and timing advace when the TPS is moved or the throttle advanced.<br />the timing should range from about 5* ATDC to about 28*BTDC from idle to wot. check for any sensor leads that may have been left off.<br /> and post a model number so I can tell if its tiller,remote or what. the overheat protection should have prevented that mean of an overheat.

 

[bigbrownbuku]

Re: Timing??or something else??

a couple o tips hunter. <br />if its been cold enough to freeze i usually start the engine and run it for a minute or so then shut it down and let it "heat soak". then restart it after a short while.<br />dont run your engine while its running that badly. its been my expierience it will injest water thru the exhaust (sometimes poorly diagnosed as a bad head gasket). if your yamaha shop doesnt have even simple tools like a leak down tester to help diagnose water entry or a vacuum gauge set to get your motor running smoothly again after head work, take it somewhere that does.