oil ratio for fresh rebuild

[wylie catter]

I just put new piston, rings, bearings and so forth in my 88 model 4hp yamaha. It calls for 100.1 but but should I run richer for a breakin period. And would it hurt it to run 50.1 from then on out? Everything else I own is 50.1 and it would be more convenient.

Thanks

 

[robert graham]

Re: oil ratio for fresh rebuild

I'd run it 50:1 now during break-in period and then back to the recommended 100:1 afterwards, but I doubt it would hurt it any to just keep it at 50:1 from then on. My 90HP Yamaha has always been on 50:1 except during the break-in, when I used double the oil. The 50:1 has to be better from an internal corrosion protection stand-point anyway. Good Luck!

 

[wylie catter]

Re: oil ratio for fresh rebuild

I figure the only thing that the richer mixture could hurt that I know of is the spark plug. But plugs run in 50.1 motors all time.

And I wonder what a reasonable breakin time would be for that motor?

 

[old-gubbins]

Re: oil ratio for fresh rebuild

My manual for a 2.5 Merc says "first tank: 25:1 then 50:1"
For a Suzuki 8hp : First five hours @ 30:1, (TCW III), varying between 1/4 and (occasionally up to) 3/4 throttle, with limited SHORT bursts to full throttle after the first couple of hours. This seems like a sensible regime to me. Don't run at one constant throttle setting when running in.
I vote for 50:1 when run in.

Hope this helps,

O-G