need some help with a high Rpm miss

mark '87 930 · May 29, 2007

Hey guys, new to this forum, but alright with a set of tools.

I have an '88 CR125 that starts and idles fine. But the bike does not want to go into high rpm. It's kind of like it's hitting the rpm limiter. It does this if you wind the throttle in neutral, or when you are under load and you want to give er.

The previous owner seemingly had spliced in another stator at some point and did a bad job of splicing the wires together, so I cleaned that all up and soldered them together and put it all back together.

What do you think? I checked the jetting and it seems fine. I should also say it was running fine at end of last season.

Stator? (I have another so I can swap to test)
Coil?
CDI box?
carb's (I have another so I can swap to test)

mark '87 930 · May 30, 2007

Anyone?

iamdawalru5 · May 30, 2007

I rode an 87 model of your bike, and it did the same thing. This one wouldn't shift out of third, but you could tell it wasn't as high revving as some other 125s of the day. It pretty much almost died out right up on top. Don't quote me, I am no mechanical guru this is just what I have experienced.

mark '87 930 · May 30, 2007

So i changed the stator and pick-up.. same thing.
Could it be something as simple as the fuel/oil mix ratio?

84cr125 · May 31, 2007

maybe, what are you running?

02yz426f · May 31, 2007

What is your ratio?

mark '87 930 · May 31, 2007

30:1. the manual specifies 20:1 but I thought that was because of the older oils and how they were manufactured?

02yz426f · May 31, 2007

I dont know, but that sounds pretty rich to me. The newer bikes run 32:1 to 40:1. I am no expert, but maybe somebody else can verify that your ratio is correct.

renes · Jun 1, 2007

Jetting can definitely be a problem. Doing a sparkplug check would be a very good idea. You know, running the bike in 2 or 3rd up a hill at full throttle, then killing the bike and checking color of plug.

But...one area I would definitely check is the pipe. Two strokes rely heavily on a good pipe with little or no dents, especially the critical area just outside the cyclinder just before it starts to expand. If there are dents here, then the top end especially will be held back. And when I say dents, I mean the inner diameter is greatly effected by the dent. It will feel like you've hit a rev limiter. But bad jetting will also feel this way too.

mark '87 930 · Jun 4, 2007

Thanks all, I tested and tuned the bike on the weekend and she runs great. I ended up replacing the stator with another I had, but the real issue was the jetting. It was WAY too rich. I fouled many plugs as well which gave me a good indication.

need some help with a high Rpm miss

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