Please sticky Offical 350x to 250x/300ex swap info

[JIMFROMTEXCO]

350x 250x/300ex swap info
i just left fischer cycle sales about 3 hours ago talking with bud fischer himself about the 350x swap.. you have to take the top rear Mount down to 1 1/2 inch from the shifter side of the motor and make a 4" spacer for the oppisite side, then the front bottem mount you have to make spacers to get it to bolt tight. on the shifter side you could use a 1/4" thick washer and on the kicker side you need approximently a 2" spacer.. and thats it to mount the engine. for the exhaust you can order a powroll or take the stock 350x header cut between the flange and the first bend on both sides and add about 2" of material. The top right fram rail has to be heated up and taped in approximetly 1/16th to 1/8th of an inch to clear the oil line for the head. If your using the 300ex engine kill swith it has to be in the off position to run. the 250x will work on the on position. you will also need the 350x cdi box.

im almost complete with my swap waiting on my top end to get back to me to finish but the bottom end is in the frame and my sprokets line up perfectly.

If you have te complete trike to do the swap with use the swinger,shock and axel for a complete set up.. the swinger is almost 2" longer and the axel is 2 1/4 wider..

any questions on the swap let me know i can help

[dork]

the spacer lengths are 55.5mm, 25mm, 5mm.

the mount will need to be 1 3/8" wide. leave a little more than that when you cut it, so you can finish it with a file.

i used the 250x wire harness since it closely matches the 350x connectors, the 300ex harness has too many extra connectors and shouldn't be used. if you use the 250x wire harness, there are only 2 mods to be done. first, you have to swap the position of the wires in the 2 way connector at the cdi. they release from the connector with a small pick or flat head. second, depending on what stator the 350x has, you may need to change the connector for it. the stator has a white(or clear) 2 wire connector, that plugs into the white connector on the 250x. also the 350x has either a red connector with 2 wires or 2 single wires for the pulse generator. if you have the single wires, then you can just plug them into the 250x harness. if you have the red connector with the 2 wires, then you need to change either the connector on the 350x or the 250x so they're compatible. heres the color code:

350x engine........................250x harness

black/red.............................black/red

the wires below can be singles or together in a red connector
blue/yellow.........................blue/yellow
green/white........................grey

the wires below are in the clear connector
yellow.................................white/yellow
green..................................green

the grey black wire on the 250x isn't used.

you should grind down the head of the top oil line bolt, 1/16 to 1/8", since it sits close to the frame. or clearance the frame like he mentioned.

if you use the 350x sprocket, flip it around so the step faces the motor. otherwise a 250x/300ex sprocket will fit.

[bigpat]

is there any difference between the 85 and 86 350x motors

[2muchquad]

The clutch cable routing is different(so are the cables)and the crankcase vent tube is straight on the 86 and angled on the 85.Otherwise the internal parts are the same;)

[zell250x]

but there are a black and green single wires on my 350x and i think the 87 250x doesnt have a gray/black wire. i have the clear plug together and a black/red wire together, but i dont know where the green wire and the black wire goes?

[dork]

i'll check the 350x schematics

[zell250x]

i got it going! thanks alot, i just over looked a couple wires, running good, big difference from the old 250x. thanks again

[dork]

cool, have fun with it:cool:

[JIMFROMTEXCO]

Awesome to hear i like mine alot! i like it more then i liked my old 400. its just alot tourqier.. alltho mine is allready broke :rolleyes: sumhow i broke an intake valve. no bigge i just have to do my top end rebuld a little earlier then winter. im going .10 over with a wiseco 10:5.1 and i would like to find some kibble white valves or sumthing better then stock. maybe a good mid range cam with a mild port job and 400ex carb... i havnt seen toomuchquad on here in awhile.. hows that 385rex coming along?

[2muchquad]

Its going good,i havent posted on here in a while but i check it almost daily.Im looking for a aftermarket axle but im not coming out the pocket $350!:( How did you break a intake valve?

[JIMFROMTEXCO]

im not exactly sure how it happened. it seemed like it was running strong. it made a little tapping noise but from what i read it was normal checked the valves often because the tapping was there.

[dork]

your best bet for valves is going to be oem honda, unless you want some custom ones made. they are actually very good and if you keep them adjusted and run good springs they last. your valves are probably original, think about it they're over 20 years old:eek: considering how atvs are used they held up real well. you can still get them from honda and if they stop making them, vesrah makes them which are copies of the oem stuff. make sure you replace the springs with new ones or if you get a cam run the r/d or kibblewhite springs. also check your valve guides, they're probably starting to wear and allowing the head to wobble on the seat.

[2muchquad]

I went with the vesrah replacements myself.I think i only paid $65 for all 4 of them.Did your adjuster nuts loosen up on the rocker arms?i have seen that happen and start making tapping noises.Like Dork said if you have excess play in your valve guides thats no good either.:( Try and get that scoot back on the road..er trails asap:)

[JIMFROMTEXCO]

well for now im going to use the other valves i have.. but i did sell my bottem end for my 250x and im going to spend that on a new valve train

[2muchquad]

bump:)

[David28]

Originally posted by JIMFROMTEXCO
350x 250x/300ex swap info
i just left fischer cycle sales about 3 hours ago talking with bud fischer himself about the 350x swap.. you have to take the top rear Mount down to 1 1/2 inch from the shifter side of the motor and make a 4" spacer for the oppisite side, then the front bottem mount you have to make spacers to get it to bolt tight. on the shifter side you could use a 1/4" thick washer and on the kicker side you need approximently a 2" spacer.. and thats it to mount the engine. for the exhaust you can order a powroll or take the stock 350x header cut between the flange and the first bend on both sides and add about 2" of material. The top right fram rail has to be heated up and taped in approximetly 1/16th to 1/8th of an inch to clear the oil line for the head. If your using the 300ex engine kill swith it has to be in the off position to run. the 250x will work on the on position. you will also need the 350x cdi box.

im almost complete with my swap waiting on my top end to get back to me to finish but the bottom end is in the frame and my sprokets line up perfectly.

If you have te complete trike to do the swap with use the swinger,shock and axel for a complete set up.. the swinger is almost 2" longer and the axel is 2 1/4 wider..

any questions on the swap let me know i can help

does anyone have any pictures of this?? I want to see where the motor mounts were moved to..

thanks

[2muchquad]

The 350x mounts are the same as the 250x.The top rear mount on the 350x is trimmed down a bit thats all.

[zell250x]

what jetting should i run if i use a 400ex carb on my 350x? the 250x carb works but the float level is wrong and cannot be changed. and also is there a big difference between the 350x and 400ex carb?

[dork]

the 400ex carb is bigger 36vs.31 and has an accelerator pump. a relatively stock 350x should take a stock pilot or one size bigger and a main jet in the range of 150-175 depending on pipe and mods. stock needle position should be ok. i put one on my buddies 350x trike and it took a 42 pilot and 175 main. its .080 over , 9.5:1, epoxied ported head, stock cam, and supertrapp exhaust.