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View Full Version : Trying to get my new '85 ATC 250R to run at it's best



bdf136
03-23-2008, 12:51 PM
OK,

I just bought an '85 ATC 250R and I'm trying to get it back to running at it's best.

When I first got it, midrange was a bit shakey. So here is what I did to it.

- Cleaned the airfilter (it was caked in heavy oil)
- Flushed the coolant
- Thoroughly cleaned the carb (it had a 142 in it, but I replaced it with a 148)
- Drained the gas and started running 50:1 Fully synthetic Amsoil in it mixed with 93 octane.

It now runs a lot better, but I think there is still something a little funky on the bottom end to mid. I was going up a little hill on a trail yesterday and I almost didn't make it because I had to get off the gas for a second to avoid a rock. The revs were really low and it barely pulled out of it. Should I think about just putting a smaller front sprocket on it? I honestly don't know what size I have on it now. It's probably stock though.

It also takes about 20 minutes for the engine to run right. When I first start it up, it misses at the mid and top end. When the engine is really warm and I keep it in high revs, it runs great. However, you must be either accelerating or decelerating. There is no in between.

I am somewhat new to the two-stroke world, so I don't know if I'm just not used to the powerband yet. But I do feel like there should be a bit more umph on the low to midrange.

Any suggestions would be much appreciated. Thank you!

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Long Live the R

bdf136
03-23-2008, 12:52 PM
Sorry,

I forgot to say that I removed the stock pipe and put on an FMF fatty.

CSR400EX
03-23-2008, 10:28 PM
what position is the clip on the needle???? and also how many turns out is the air fuel screw??

bdf136
03-24-2008, 03:46 PM
The clip is at 2. I moved it to three but it seemed to worsen, so I moved it back.

The air screw is at 2 turns out.

CSR400EX
03-24-2008, 03:50 PM
air screw should be at 1 1/2 turns out, FMF says to use a 145 main for their pipe, so it sounds like you richened it up and it got worse, so i would try a 145 main.