RPM's won't go over 1700

[toddingalls]

1990 yamaha 115 hp 2-stroke
RPM's won't go over 1700, or so.
She just bogs down and dies w/ anything over about 1700 rpms.
theres no alarm going off... don't think it's in limp mode, but not positive
cleaned carbs still same problem
compression okay
good spark
fresh fuel
changed fuel filter
Any ideas?

[99yam40]

If what you say is true, I would think your carbs are in need of cleaning

[toddingalls]

First thing I did was clean the carbs.. any other ideas?

[toddingalls]

Ps... there's a lot of vibrition when the motor gets up around 1700 rpms also (before it dies)

[TownsendsFJR1300]

F115

If its vibrating badly at that RPM and the RPM's don't rise anymore (the carbs are clean) sounds like a spark plug may be misfiring.

If their old, or you don't know their age, they need to be changed. You'll notice a difference in a 2 stroke with new plugs as they affect performance much more than a 4 stroke.

Some Yamaha combustion chamber cleaner before the plug change wouldn't hurt either being a 21 year old engine.

Can you rev the engine past 1700 with just the throttle link (at the engine itself, in neutral, in the water-using the carb linkage)? Or is the limited RPM's just under load (in gear, under way)?


Good luck.

[toddingalls]

Thanks for the reply.
I will try new plugs.
She will rev up past 1700 in neutral, just not under load.

[TownsendsFJR1300]

F115

Make sure you check the gap before installing, they sometimes get bumped in the box....

If the carb bowls have a drain screw, drain them and try to catch what comes out looking specifically for any debris. (I use an old tuna fish can, fits in most places). You may have a piece of crap as well getting sucked into one of the main jet at 1700 RPM's as well