XT350 Performance Mods

I'm looking for any performance mods for an XT350. Let me know what you've got.

I'm interested in this thread also!

there was a thread in the vintage section devoted to this but i have most of it if not more done to mine.

if you are using it off road,

-a uni air filter,

-supertrapp silencer,

- 2 heat ranges colder on the plug with gap closed 10thou (jets it 2 sizes larger across the whole throttle range),

-air screw adjusted out 1 turn from bottomed (or whatever your bike runs better with it set to),

-shim needle up in primary carb with eyelet from small red electrical connector. does not have to be done if you use a larger/drilled pilot jet

-drill pilot as stock is lean and no others are availible. do not go too big as these are expensive from yamaha. a wire run through to enlarge it might work as well

-install xt600 stock main jet or equivilent as it is larger and fixes the lean on upper rpms even with stock exh. can use mikuni jets for snowmobile but they are not numbered the same.

-tpi valve installed on airbox lid. can be closed for water crossings but allows more airflow. some guys ran a drilled airbox lid and covered the holes with duct tape for water crossings.

you can run a k+n filter without the airbox but i do not reccomend it for off road. jetting has to be probably at least 2 steps ritcher than what i have listed above.

i cannot give you specific jet #'s as mine has gone even farther on the power quest. i have porting, oversize ss head pipe, and custom ground webcam camshafts in mine. still running a swiss cheeze'd air box as it is my primary off road ride.

hope this helps you out some.

Edited by maim
oops

maim

I wanted to know if your carb and exhuast was done before the porting and cams...if so could you give accounts of the power that that made.

I have done the carb up and my bike runs starts and stuff great wheelies in 1st and second but I may want a pipe

- 2 heat ranges colder on the plug with gap closed 10thou (jets it 2 sizes larger across the whole throttle range)

Maybe I'm missing something , but exactly how can that happen ?

-air screw adjusted out 1 turn from bottomed (or whatever your bike runs better with it set to)

The stock XT350 carbs have an air screw ? I know they have a pilot ( idle fuel adjustment ) screw under the brass plug on the front underside of the primary carb .

bill, i had the carbs and the supertrapp done before the porting and cams. it did make a difference but never put it on the dyno to see.

pd350, there is a reason why it works but i forget. all i know is that it works as i have done it to multiple bikes/sleds/lawnmowers/trucks. i was told this by a njk rep and it does work. they reccomend doing this because of the ethenol blended gas/fuel we get nowadays. whenever i pull the plugs, they all read on the ritch side of safe and i some cases have made more power. there is a whole writeup on why this works on a dyno pull for a rx1 snowmobile somewhere on thenet.

i might have called it wrong on the screw but i know mine with all the mods prefers 1/8 turn but only holds at 1/2 turn atm.

Well , I guess it's gonna cost me a spark plug to find out if it'll do the XT any good . As far as why and how it works , I'd just be guessing .

A good rule of thumb about carb adjustment screws : if they are located behind the needle ( toward the air supply ) , they are most likely an air adjustment ; if they are located ahead of the needle ( toward the head ) , they are most likely a fuel adjustment .

Thanks for the tips maim ... :)

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