Basic jetting question.

I have a basic jetting question.

I have a 92 DR650. Stock motor with a K&N inside a stock air box. I just installed a Supertrapp muffler with 10 or so disks (up its loud). I installed a Dynojet kit per the stage 1 instructions. The starts and runs/idles fine. My question is during WOT pulls the bike often/usually pulls hard to 5k where it falls on its face. At that point the bike feels like it starts to cut out. I know I am more then likely off on the main jet but I am not sure what way to move, larger or smaller.

Thanks in advance,


could be either but it shouldnt be that far if you followed the instructions exactly.

I will just try one size each way then. Thanks Eddie.

Ok well now I am starting to get pissed. I have tried all the jets I had. I started with my largest and worked down so I KNEW I wasnt moving in the wrong direction. As I went smaller the bike performed better and better. Where I am at now I feel that if I went one size down then the bike would be perfect. My only concern if that size is the stock jet size (137.5). All I did was add a slip-on (Supertrapp, 12 disks) so maybe I am not really flowing that much air then before up top. The bike feels much better on the low end. I attribute that to the pipe or the taper of the Dynojet needle (more likely the needle).

Eddie- Should I be concerned runnng what amounts to the stock size if that is the jet that allows the bike to pull to the redline or should I be looking elsewhere? The bike runs perfect till about 1k before redline.

the end demension of the needle dictate main jet.

it doesnt really corralate to the stock needle main jet requirement.

honestly,the supertrapp is the issue.

take the end cap off and i bet its cured.

Thanks Eddie. To get this straight you're saying I don't need to get too hung up on the number on the jet as long as the bike is running good? I am obviously concerned that I will burn the bike up if the main jet is the same.

I know the Supertrapps aren't the greatest but with a bike this old (92) I don't have a ton of options.

exactly,theres no danger of engine damage if it rev cleanly.

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