yamaha f 60 four stroke

[squidlips 2]

it backfires through a carb at 3600 rpm,i have replaced coils,spark plugs,h.t leads and h.t lead caps.the engine is a 2003 model with 155 hours on it.<br />any help would be much appreciated<br />regards karl

 

[bigbrownbuku]

Re: yamaha f 60 four stroke

start by checking that you havent mixed up the plug wires, its not top to bottom aligned.<br /><br />next do a leakdown test. pickup a genuine service manual and check the belt alignment hasnt moved.

 

[squidlips 2]

Re: yamaha f 60 four stroke

thanks ben.<br />all the h.t leads are on the right way round i have double checked that.<br />all the compressions are within the limits that the manual says.the engine ran for 4 hours today occasionally missfiring,the revs drop to 2000 then pick up again,i came back from fishing 4 hours running without any missfiring.<br />do you think it could be a sticking inlet valve?<br />what is a leak down test?<br />regards karl

 

[Triton II]

Re: yamaha f 60 four stroke

Squidlips, how long has the engine been doing this? Was it after a service? Why did you replace all the ignition stuff, did the engine get drowned? If it's not ignition, it may be an idea to check your valve clearances, it's easy to do with the F60, and it's probably better to be too loose than too tight with them. Rodbolt suggested in a previous maintenance post on valve clearances that you may need to use a special type of feeler gauge, but I did it with normal feeler gauges at 200 hours on my 2003 FT60B (same powerhead as the F60) and all 8 valves were well within limits. Good luck, keep posting!

 

[squidlips 2]

Re: yamaha f 60 four stroke

thanks for your reply triton<br />the coils etc were replaced by me as one coil was sparking out.the engine only started this when i was out fishing,i noticed the coil sparking to earth thats why i changed the coils etc <br />the engine has never been under water.<br />i wondered if this sparking has damaged the cdi unit? as a qualified car technician it would seem that the timing was out but it only appears to be one cylinder so i would assume that ruled timing out.the only other thing i can think of is valve clearances,the problem is that no yam dealer seems to have any test equipment here they all say them engines are bullet proof.<br />regards karl

 

[Triton II]

Re: yamaha f 60 four stroke

Hi Karl,<br /><br />I have the full service manual for your engine on CD as a .pdf file. I'll email it to you if you send me an email to <mdbarnett@optusnet.com.au>. Cheers,<br /><br />Mark.