Hi all, I have a '96 LT80. It has FMF Fatty Pipe with Power Core 2 Silencer, DG 20mm Carb. with K&N filter with Outerwear, 428 MX Chain with 13T Front sprocket and smaller rear (not sure how many teeth), and Boyessen Reeds. My problem since I got the machine last winter is that it has plenty of low and mid power, and as soon as power ban kicks, it just falls on it's face. It was bone stock when I bought it on a freshly rebuilt motor with 0 hours (the motor was professionally rebuilt). So as I have owned it, I have added the above mods. one at a time in hopes of finding what the problem is, and I have not found it yet. The only thing I can think of that is left that could be bad is possibly the CDI?? Any help would be greatly appreciated.

 

IMO Your problem is the FMF pipe. They are like that.
You need to go up a bunch on the front sprocket to compensate.

 

I believe I read that somewhere on here, that the FMF is not a "high RPM pipe". Unfortunately, I found this site after I had bought the pipe. But it was having the high RPM sputtering even when the machine was totally bone stock. What pipe would you reccommend I use?? I still have the stock one, I could throw it on, but I feel that I would have the same problem, but if you think it's worth a shot, I guess I could try it. Other than the pipe, what do you think the problem could be??

 

I would suggest checking the valve clearences. A valve adjusted too tight could cause this situation.

 

It's a 2-stroke, so there are no valves, just reeds.

 

Oops!
[img]i/expressions/face-icon-small-blush.gif[/img]

Okey then, how about bad reeds?

 

It could be the reeds, they ARE aftermarket boyessen reeds, so I know they aren't gonna last longer than OEM, but I was even having this problem with it when it was bone stock, so I have replaced everything I possibly can, but the CDI and clutches, but it has perfect low and mid range power, so I am totally clueless

 

OK, Just how fast is it now?
Is your chain size 520 or 428?

 

I'd say it only does about 25mph and my chain size is 428.

 

You have had this problem since it was bone stock (with a rebuilt engine), you did the mods, and the problem is still there. This seems to indicate that it's something that you have NOT changed. Is it possible that the porting was mis-machined (doubtful, but possible)? I have seen on "Orange County Choppers" spark plug wires that are clear, and show when the plug fires. If you could locate one of these wires, that would show you if you are loosing spark.

I'm just trying to help narrow it down to whether it's fuel related, or electrical.