Xt350 jetting help

Bought a 91 xt350 from a guy who put aftermarket DG silencer. He never got around to jetting it. It wouldn't hardly run so I took the carb out, it had a 125 main jet it in which I changed to a 122 and he had washers under the needle since there are no adjustment slots. Took those out now it runs good till about half throttle and then sputters really bad. What should be my next step as I have almost no experience in this area.

When making changes , do one thing at a time . That way you can much easier find the sweet spot .


You should start by reinstalling one needle washer .


I have to ask why you went to a leaner main ? Most guys want a richer main .

Is your air box completely stock ? No alterations ?

The Stock Primary carb jet should be a #125 and the secondary jet is a #106. Running a pipe like that your going to end up turning your air/mixture out more turns than stock setting. Stock is 2 1/2. I run a SuperTrap and I didnt get all the plates with the bike so in order to make my bike run smooth and just run right I have it turned out 5 1/2 turns. No Smoke!


So what I'm getting at is you have to be able to tune that muffler to your jets or buy more plates or buy Larger jets and see where your sweet spot is with your carbs. Ask yourself, What is that pipe tuned for? What Jets? At this point you have No idea. Maybe someone here might have the same setup and can get you in the right dirrection.


Have you cleaned the carbs real good? (pd350) is the man to talk to! :thumbsup:

Air box is completely stock although I'll be picking up a uni filter for it soon. At this point I'm just trying to get it to run correctly. After I made the changes I rode it around and it still sputters after half throttle but it runs better when I take the air box cover off

Here's what I run for comparison sake : an iridium spark plug ; stock jets ; about 2.5 turns out of the pilot screw ;a single #4 washer primary needle shim ; Air box cover > back facing side removed and a competition Uni filter installed ; secondary to primary carb synchronization is adjusted for immediate secondary function . I have the stock exhaust pipe/muffler and have drilled four 1/4" holes in the baffle centering plate .


I can't say just what the difference is between the DG silencer and stock muffler . I wouldn't think all that much , other than sound and probably , the DG has less restriction .

Ok played with the air fuel mix screw and got it a little better. Still rolls past half throttle but when I took the air box cover off and removed the air filter just to test it out I got up to full rev with no hesitation till wot. Again I have a 122 main. Don't know what my pilot is but I believe I have one smaller I can put in. What should I do since obviously I can't run with no filter


I took the air box cover off and removed the air filter just to test it out I got up to full rev with no hesitation till wot. Again I have a 122 main.


I'd do a plug chop . That would tell you the true story of what's going on in your motor at that time .


Under the conditions you mentioned above , hit the kill switch at WOT while riding with the motor at normal operating temperature , shift to neutral and stop . Pull the spark plug and pay attention to it's tip / porcelain color and condition . Take a good pic and post it if at all possible .

ImageUploadedByThumper Talk1381018877.788109.jpg

Looks kinda funny but here it is

I can't tell if that's some sort of deposit on the tip of the electrode ???


That shot was taken of a WOT , hot , under power , chopped plug ?


How does that plug compare to the plugs in this chart ? ( great detail of your hand , but the plug is a bit fuzzy ;) )



Well I've got it really close now. I can run through all the gears just fine and it will only sputter slightly which is close enough for me to have a mechanics fine tune it when I get the valves adjusted and everything checked out. The front suspension really sucks is there anything that I can swap the forks with?

Haven't been on this forum since I got myself a xr 650l. I had the same problem with my 350. You are rich on the secondary carb. Go down one size on the main on that carb. The test it again. Should be a lot better. Then try the standard main in the secondary again without the shim and test. Make sure your carbs are sincro'd just like the manual says. Lots of little bogs creeping in there also.

Be careful of pulling the plug with the engine hot. Put anti-sieze on it.

The TT350 has the same carbs but bigger jets. Sudco can supply an ternate jetting for those Tekekaki carbs.

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