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Hello all.
I need some input / info on how big I can go using a ultra/xcr crankcase, and what is the best/cheapest way? I have a 96 ultra sks w/slp pipes and i love it the way it is! I also have a 2000 XCR800 newly rebuild and havent ridden it much (got it in pieces) looking forward to ride it more though! I have 2 extra ultra 680 motors lying around from a spx 97. and a set of modblaster pipes im not using!

The question is what is the best and biggest i can go ? can i put jugs from a 700/800 twin on it and have a 1050 or 1200cc without a lot of fabricating? can the crank take it ? I know there was a 1100 kit from someone at some point, but that is/was extreamly expencive! The 800 big bore is waisted on me since i got the xcr800 and i want even more!! Has anyone gone biggger and how did they do it ?

The motor I come up with will be put in a Wegde sled i have with 144" track i also have to be a "climber" (i like the wedge best) :)
 

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You cannot get that kind of size without fabrication.

The stroke is the same on all the modular motors (xcr600/ultra680/xcr700/xcr800), just the bore is different. To get 1100, you need to go to bigger bore, with a 65mm throw XCR crank you'd have to go to 85mm bore pistons from the stock 72mm (xcr 800) bore. That is over 1/2" bigger cylinder, so to do that with a stock jug, there would hardly be any room left in the ports.

This is why the 1100 kit is expensive, it's custom built jugs, heads, and most likely custom pistons.. Then, you'll never get anywhere with the pipes you have, you need pipes for larger CC volume.
 

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check out amsnow used section. lots of used big engines for sale. cheaper then building new.
 

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HTG made a 1080 kit which consisted of custom cast jugs bolted to the stock crankcase. A setup like that made 250hp at Dynotech.
Generally speaking, a reed valve motor can make amazing power without crankcase modifications, and is not so restricted by the bore spacing leaving little space for transfer ports either since it can have booster ports in the back leading straight to the reed valve.
 

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more is always more$ if you can find a 1080 kit its probally the least expensive way to get more. but why would you want more when you say you havent even ridden the xcr 8 much? thats gonna be your best bang for your buck. problem with going big bore is when you teat something up its always very expensive to rebuild. the xcr 8 parts are readily available and reasonable. properly set up i cant imagine you needing more.
 

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very few made hp like priceperformance he could get up to 1100 cc, htg made a 1200 kit but they didn't hold up very well. I love my 1000 but on the trail it was simply stupid and just spun until you let off the gas. if I had to do my 1000cc build over again I would look for a used water craft, lots of engine for very little money.
 

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when I was researching big bore kits for my build the responses were that htg stroker crank in our bottom end wasn't the best route to go. a billet crank from other sources would have been better but added a lot to the price of the build.
 

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What is the biggest bore I can go on a polaris 650 triple I was told 120 thousandths is what the motor is that I bought I'm trying to find out if that's true if they can go 120 thousandths on them
 
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