I don't know how to say this ..... But ..... It won't fit .

Buy a base gasket from each and look if you need to .

Rick

 

go down to your local polar ice dealership and ask for a gasket from each and compare. all these guys on here say it can't be done. and by the way what are the credientials of this rick ritter guy. anyone rick maybe just wondering

 

He is the own RCR an has been building parts an mods for the the Polaris atv's for long time. He is one off the guy's you buy pipes,porting, heads an alot more parts for them. He is very helpful to people on here because of his work with the Polaris motors.

 

I'll get a couple gaskets off the shelf today . The bolt holes may be close - but the transfer area is different .

I am just trying to help . It is weird though that most every part in a 350 will swap to a 400 except the jug and head . I was told once the reason for the big change was a patent infringement on the intake boost ports on the 350's .

Rick

 

go to the home page and read his article on boring. then look at who built almost all the 400 motors on this forum.



long story short he's a guru.

 

Ok fellas - I took a base gasket from each off the shelf today . The bolt pattern is IDENTICAL - ( I didn't remember that) - the transfer port openings are different - and I can see the sleeve on the 400 is quite a bit to big . Anything is possible with machine work (you can get a 400L jug onto a 250r Honda with some machine work and welding) but I can see you just can't drop a 400L jug on a 350L bottom.

Cylinder heads - a 350 head will only fit a 350 and a 400 will only fit a 400 . The bolt pattern is different .

And there we have it .............. :-)

Rick Ritter

 

Thanks for the info Rick. I knew it would fit the bolt pattern on the block but was worried about the rest. I don't think I will try it, sounds to risky and I am not willing to put that kinda money in it. I have both heads and could see everything was close except for the angle of the plug, but didn't have the 350 jug so couldn't compare. Sat the jug on there today and it looks as if the piston is a lot bigger on the 400. I would have to turn off a lot of the bottom sleeve to get it to fit inside the block.

So, I have a 91 350 trailboss in really good condition except for the cylinder and piston for sale if anyone is interested.

 

I want a 2wd 350. I don't need an engine :-) .

Maybe we can help each other ?

Remember too - the internals from the 350 will fit the 400 cases . Maybe swap cases over ?

At any rate - I think we can help each other . Is your 350 a 2wd ? I have been looking around to find one - do you have it ?

 

Yeah, who is this Rick Ritter guy? LOL get out of the closet pal. Rick says it won't work, it won't work. Search in the forum, this is a top notch engine builder. I say, in rick we trust. Doc

 

I didn't know that the 350 had intake boost ports, the first few years of the 400 didn't, but in 96 when the engine were started to be produced by robin of the usa instead of fuji heavy industries they then had them. i can only assume that the switch from fuji to robin had something to do with the lawsuit fuji and polaris had against. IRS (injection research specialists) sued them both for stealing their two-stroke injection for snowmobiles. anyway back to the cylinders. the majority of you think think that the boost ports gave more power. well my opinion was that in stock forom the ones without felt better to me. case in point our old 91 350 trail boss than our 94 sportsman 400 would always beat our 96 sportsman 400. Is this normal. any way a question for rick ritter is anyone using fuel pumps on 400 with bigger carbs. and if so when is this necessary. My brother has a 2000 scrambler with a 432 big bore and 38 mm roundslide and he has fuel delivery problems. likes to quit after long periods of wide open throttle. espescially on less than half a tank. thanks for the help everyone