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.
- Took off the stock pipe and put on an FMF fatty.

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!

----------------------------------------

Long Live the R

 

First off, I think you made a great choice of rides bro! Second, jetting is tricky, but extremely important with two-strokes. Get it wrong and it cost you money and/or heart-ache. As I recall 148 sounds like it could be about right for your set up (however, maybe a bit fat), but!! the only way to know is to read what the plug is telling you. Two-strokes will always be top-end power producers, the key with them is to maximize the band of the top end to how (and where) you ride. Meaning, If ya bog them they will dissapoint ya, ride them where they produce, they will excite ya.

With that said, check the color of your plug. It should be a "light Chocolate" brown. Anything more, or less means your jetting is off.

Once you get the plug color correct, you can "dial-in" the needel settings for idel and very lower end.

I wasn't there so, check the plug and maybe you should have down shifted to keep her in the "R"'s!

Good luck, hope this helped!

 

The plug is a dark chocolate color. So does that mean I should tone down the main jet? Or does that mean I should tone down the slow jet? I'm already running it at 50:1 so I don't think I should make it any more lean.

Also, my clip position is currently at two. I moved it to three, but it seemed to augment the midrange sputters. The bike is currently on the DL because I have to wait for my new chain and sprockets to come in before I can ride it again. I think I'm going to move the clip to the first position and see what happens.

I think I need a new idle screw because the one in it looks really beat up. I have one of those ordered as well. I have the screw all the way in to keep it ideling well. Is that normal? It doesn't seem normal to me.

I just ordered a set of pro series two-stage boyesen reeds to put on. I figured it couldn't hurt.

 

No, sounds like your in the range... hard to tell without seeing it. Better to be rich than lean. If it looks like shmeg is starting to collect on it, and you foul a plug it's to rich.

If you are putting the new reeds on it, I would what to make any changes other than to replace that idle jet. I think you will like those reeds. I have the V-force set up and I noticed a difference on the low/mid. Also, you can hear the reeds fluttering on idle, sounds cool.

One last thing, I'm not sure where your at, but there are folks that can dyno-tune them. They typically charge $75 an hour and it should not take more than two to get it totally dialed.