Country Joe....I forgot to mention that I still have a 38mm Keihin PE carb that came off one of my 350's before I modified it. It's reasonable. Sparks still sells these as an upgrade for the 350X.

 

MX4life.......sorry I missed your original question......I do not think the bolt patterns are the same on the two motors, so the answer would be no, at least not without some expensive mods.

The biggest difference in the 400ex motor and the 350 X motor other than the displacement, is the valve sizing, and weight due to the 400 ex being a dry sump motor and only a 5 speed. As I mentioned in an earlier post, I have seen 350X's taken all the way up to 550 cc's, but serious case work is involved. It's still one of the toughest motors out there though.

We are looking at opening up the exhaust valves slightly on the 350X head, but only with a lot of other changes to the head flow, and some timing changes as well. Will let you know. This is on a 350X "supermotor" which I am working on right now. Target is 60+ hp. The builder who is doing the work is a GTR-1 Porsche specialist, who builds a lot of Lemans cars and gets his power from head flow and friction reduction because they are working on fixed displacements all the time. He commonly gets 150 - 170 hp./liter on naturally aspirated air cooled car engines. The other aspect I like about this builder, is that he builds for durability as many of the races are 24 hours. They target 100 hours on these race engines before tear down. Lot's of exotic stuff going into this one.

 

I just bought a PE 38mm carb for my350x. what mods did you have to do for it to work right? I cant figure out what is wrongsoitried a400ex carb and it still isn'trunning right. What size jets are you using for the PE Carb? I talked tosomeone and they said to go back to the stock airbox. The engine is on a 250x. The bike never idles I have to give it some throttle to start it, and it spurdders when i slam the throttle WOT
MODS TO ENGINE
92mm JE piston
Shaved Flywheel
FST CAM with needle bearings
PORTED HEAD (72%on exhaust side) flow tested
UNi POD FILTER on carb
Ti retainers and springs
Powroll supertrapp ehaust
38mm PE CARB from SUDCO or 400ex carb whatever runs better
Need JETsize for both carbs

 

Are you using the stock rubber inlet pipe between the air filter and your carb? If you used a larger smooth wall pipe it will seriously affect the jetting because it will increase the air flow velocity. What color is your spark plug?

In addition the 400 ex carb is really too small for a 450+ cc motor which is what you have if its not stroked, and if it has a 6 mm stroker kit, it would be a 492 cc.

You will need very pretty large jets for this motor in either the PE or the stock 400 ex xarb.

Call the dealer where you bought the PE carb and ask them......and be sure to tell them the cc's of your motor.

 

Thanks i will check everything tomorrow i will try the PE out again I think it as a 160 main which sounds like it will be to small. I will contact Sudco and get the right jets

 

MDE3 check your PM.

 

I should be receiving a 38mm Keihin PE carb soon. It's going on a 250x with hi-compression piston (.40 over), race cam, race porting & clamp on air filter. Any ideas on the jetting?

 

I JUST BOUGHT ONE OFF BAY FOR 600, AND THAT ONE GUY THAT SAID THERE'S ALWAYS A FEW ON THERE, WELL THATS NOT RIGHT. VERY RARLEY IS THERE EVER MORE THAN 1 OR 2 I LOOKED FOR ABOUT 3 WEEKS BEFOR I FOUND ONE. BUT YOUR GONNA PAY BETWEEN 500-800 DOLLARS FOR A DECENT RUNNING 350X MOTOR...SO I SAY IF YA SEE ONE FOR A GOOD PRICE AND IT'S IN GOOD SHAPE, JUMP ON IT