MicroSquirt.com read only forum (Jan.15,2018)

Hi folks,

I've got my bike (a 1982 Yamaha SECA 750) running pretty decently now. It even maintains idle pretty well throughout the warmup process. However, during the initial few minutes of running, say at 40 to 50 degrees or so, it kind of loses power around 4000 RPM. Currently I've got 150% WUE at 40 degrees and 145% at 50 degrees. I'm running an oil temp sensor, so it doesn't move too fast, and the engine is really competely warmed up around 100 - 120 degrees. The power loss seems to go away before that, though, but I haven't datalogged the whole thing.

At a guess, would you say the power loss is likely from an over rich, or over lean situation?

Thanks,
Paul

Paul,

It's hard to say from a distance if this is rich or lean. Generally cold engines run better when too rich than too lean, so I would start by assuming too lean. However, then you have to go by how the engine reacts. On the other hand, the oil may not be warming as fast as the internal engine components, and you might have too much cold enrichment. Only testing will tell. It may aslo be that the engine wants a different cold enrichment amounts at different rpms, and sorting the 4000 rpm issue out might adversely affect the idle (though hopefully you move through this quickly and it isn't serious).

Lance.