Yamaha 130hp saltwater series timing or carbys?

[nickbill]

Hi all.

I have a yamaha 130hp saltwater series V4 which i love. however I had a mate around to service it (a qualified outboard mechanic) and when he removed the spark plug caps on 2 of the cylinder heads (one at a time) they had no effect on the performance of the engine. when he removed the other 2 caps (again one at a time) they nearly killed the engine. also the engine run generally rough as i was told it should sound like a sewing machine when running perfectly.

we checked the timing and all 4 cylinders are dead on TDC. ran a compression test and all compresson is perfect. visual inspection of the carbys showed they were still really clean.

so my questions are:

1) should the timing be spot on TDC for all cylinders?
2) could the timing be the reason for my rough running?
3) what the hell should i do about it?

Thanks guys, looks forward to nutting this one out.

Nick

[jb123]

clean/rebuild carbs

[ausnoelm]

seems more like you have a slight spark problem, seeing as two plugs removed makes no difference, have you replaced the spark plugs and/or the leads on those two cylinders, have you performed a spark test? you cannot just "look" at carbies, they need to be stripped and rebuilt with new gaskets and so on, buy a genuine manual for your motor and do some trouble shooting before you start pulling things to bits

[nickbill]

plugs were replaced when the engine was serviced so theyre no more than 5 hours old. the only reason i dont think it would be a carby issue is that there is 2 carbys on top and 2 carby on the bottom, each running the cylinder directly behind it. if there was an issue with the carbys i would have thought it would be both tiop cylinder or both bottom cylinders, not both the left ones considering they are running off 'serparate' carbys.

Not sure if a spark test was done, what does that involve?

[nickbill]

***, thanks for all the supports guys...

[Tucker]

If you don't "think" you have spark then by a spark tester to be sure. Gotts start somewhere.