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Need more dispacement? 250 and 300 R&D

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Hey all lets get some backround info outta the way first. I have a 2000 TE 610( thats forsale) and want to get a 2002 WR360 in the worst way:), but may have to settle for a near new WR300. Im not new to the 2 stroke world as i learned how to ride on a kx250 and have had a growing desire smell the sweet smell of the blue haze. Im also going to school for mechanical engineering, and know my way around an engine. So couple all that with the fact i have a broken ankle:cripple:, cant ride, and have been laying on the couch almost permenantly; I needed something to occupy myself. In what a believe was a percocet induced euphora it hit me, the only thing i enjoy more than porn was trying to do new things with engines:D...

so i know we've all heard the saying:

" theres no replacement for displacement :doh:"

Well for us big bore kit guys we all know the 300 is a punched out 250 cylinder and not much more boring is possible, although i thought i saw a possible 340 kit once..

and with that i started to see what top ends can fit on a late model wr250/300 (~2009) and for the purposes of this writeup any comparisons will be against the afformention models

The First Candidate ~96-02- wr360

I started on halls cycles looking up the parts catalogs to compare specifications and so far the top end needle bearings are the same so their pistons would be a direct fit and the cylinder stud holes take the same bolt as well, unfortunately the powervalve systems are different and would take some doing to get working properly. I also could not find the dimensions of the mounting holes for both the new wr250/300's or the 360 so after thinking awhile i got it... Fleabay!:smashpc: i looked for anyone with a gasket, topend and cylinder forsale and asked them to measure the distance of the mounting holes. I am still waiting for more responses.

Pre 95 wr360

still waiting on responses for measurements of the cylinder, these models are non powervalved and would make a swap simple.

still looking for a measurement source for the needle bearing

got a measurment of 112 mm diagonally from a 92 360

~84-88 wr400

Now we are getting some serious displacement, non powervalved watercooled cylinders

86 wr400 113mm diagonally from the center of the four mounting holes

86 xc400 bolt holes diameter-10.5mm holes side to side 87.5mm front to back-76mm

84 wr400 wrist pin OD 17.85mm. , ID 11mm, width 24.60mm

~86-90 wr/cr430

non powervalved watercooled waiting on measurements of the mounting holes and need to find a source of the needle bearing measurement

84-87 cr/wr500

big bad 500 wouldnt it be nice if this jug bolted right in:banana: waiting for mounting hole measurement and need a source for the needle bearing measurement.

85 CR500 "The diagonal measurement eye to eye between these mounting holes is 123mm."???

87 cr500 bolt holes front to back 77mm, side to side 84mm

pre 84 500

aircooled cylinder just outta curiosity cause seeing this on a modern engine would be hilarious:lol: waiting on measurements from the mounting holes and need a source for the needle bearing

A man Selling a bunch of gaskets:

The Husqvarna (Pre Cagiva case design changes??) base and head gaskets have the same center to center dimensions: 75mm front to back and 84mm side to side.

The Cagiva base gasket is not symmetrical, so is 102mm front to back and 95mm & 120mm side to side.

Okayyy so yeah you might find this stupid and unlikely anyone would ever do this. Im aware theres other things that go into this such as exhaust, reeds, and carbs but if they do bolt in and use its reeds its not too hard to get a exhaust to fit, route coolant lines, make a carb boot and jet.

I like knowing if things are possible are not and if your curious too and have some of these parts go out and measure them! Also add anything i got wrong or missed. Im just one man..👍


unfortunately I cannot measure any of the parts myself and do not know how accurate these people are when they give them to me but I would say a few mm difference can in actuality be a match and would be worthy of further investigation. :busted:

FIRST CONCLUSION: A case change starting in 1990 separates 90&up with the front and back bolt holes being of different widths, while 89 & earlier have symmetrical bolt widths and swapping of cylinders would have to be between these two groups

Edited by goincb89

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I'd stick to the 2002 WR360 plan myself. It's already as big or bigger than the 300 will stretch to and has the 6 gear box. If you want to go modern, put it in a later chassis.

If you want to go really crazy, see how far you can stretch that motor. It'd be a better basis to start with than the 300 IMHO.

Get well soon. I hate broken bones!

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I am curious about your engine swap findings and interest in "bigger is better", especially since I have a 1991 Husqvarna/Cagiva 260 WXE (see my other TT posts about it) and a critical decision to make.

Since an oversize piston kit for the 260 cannot be found (I'm currently looking at every conventional source with no luck), I'm torn between: 1) selling it (but its so awesome I hate to think about that); 2) finding a complete 1989-91 top end for the 250 which should bolt right up (I think); 3) going bigger and trying to find a kit to boost it up to a 360; or 4) trying to find ANY size motor other than the 260 (125; 250; 360) from those years for a complete engine swap.

Good luck with the broken ankle; I'm nursing a fractured rib so TT is a great place to spend some time pondering things like engine swaps and big bore kits. I hope you'll keep this thread up to date with your findings.


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hey captcatfish

well ive been slowing getting some info in and if your able to measure your wrist pin bearing and the dimensions of your cylinder base mounting holes and lets see if we cant find another cylinder/piston that will fit:thumbsup:

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I have a 2000 WR360 and will always own that bike. The 360 motor from any year bolts directly into any WR250/300 frame. All you will need is frame to head stays and hoses. All very easily findable. Pipes are easy as well and still readily available for the 360. Find an old beat up 360 from any year, they are out there for not a lot of $$. Get a WR250/300 that is reasonable and make your swap.......you are gonna love it.

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