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Hey there guys, just bought my first 250R (88') with some work done to it. They actually took a pilot 400 motor and bored it out to a 436 runing 110 octane. I am not a huge fan of that, but i bought it and would like to fix it up and change some things on it. What is the best way to adjust the bike to run more of 98-100 octane. I mainly want a bike that I can take to the dunes and have fun with that runs good. Any ideas would be great. Also what are some of the best sites to find parts? I need to get a new silencer and pipe possibly, some other parts like like headlight stuff, chain guides & Rollers, and a thumb throttle to replace the twist (not fond of the twist throttle yet). Any suggestions would be greatly appreciated.
 

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to lower your compression, i have a feeling youll have to re-chanmer your head. i doubt that the head you have on there has replaceable domes. have you checked the compression yet? its possible it could be run on lower octane gas, and the previous owner just ran 110. you're probably best off checking the forums and ebay for a thumb throttle. as for new parts, theres BVC racing, the site sponsor, rockymountainatv.com and motosport.com are some the big ones. magicracing.com is also quite good.
 

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It sounds like you have a wild motor there. If you start making changes, you better know what you are doing, or it will grenade. I would recommend having a shop do the work. One that is familar with the Pilot top end engines.

For the pipe, is it a specail pipe to meet up to that top end or do standard 250R pipes work. You will want something that is made for big bores. If it is a standard type pipe, then most silencers will work.
 

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Thanks,

From what I can tell it looks alot like the whale pipe, and its got some DG silencer that does not go with a "R". Do you guy have any suggestions to replace the pipe or silencer. For right now I really want the silencer gone and replace it with something that atleast looks correct. Thanks for the websites also.
 

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Check ebay and some of the manufacturer's websites. FMF, ESR, BIll's, DG, Pro Circuit, CT, Duncan, FTZ, LRD, etc. etc. Basically look at price and which one looks the best. If you need a spark arrestor or need it extra quiet that narrows it down a lot. ESR has a new spark arrested silencer coming out soon.

www.esr250.com www.ctracing.com www.duncanracing.com www.lrdperformance.com
 

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also if your just looking for a play bike you may want to seriously consider selling that engine and getting a more typical motor. that engine may work fine, but, you will have to be more careful with it, and replacing parts is going to be more expensive and they will probably be harder to find.
 

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Welcome to the site. Neat little set-up you have!

You might be able to run 98-100 octane depending on your current compression, squish, etc, etc. But I am just wondering, if you are willing to pay for 98-100 octane, why not just leave it for 110, its not much more $? Many duners use high octane race fuel and alky to dune with, and it doesn't cause problems, it actually makes your bike run cooler.

I would be careful buying a new pipe, because the one that is currently on it might be tailored to fit the Pilot exhaust flange. If they are different from a TRX flange? Not sure. If its a whale pipe, its probably either an ESR, FTZ, or CT. So maybe you can get a silencer from one of those companies to better match your current pipe.

As far as a thumb throttle, I have run a billet Terry Cable throttle assembly & cable. They are universal and can be found at many atv parts dealers & eBay. I have used this assembly with up to a 44mm carb with no problem, so it will not doubt handle that big Pilot carb.
Here is a link:
http://www.terrycable.com/products/product...spx?id=MTA1Mw==

As far as chain rollers, guides, etc I have always ran UPP, which are are hard poly and hold up well.
Here is a link:
http://www.uppracing.com/index.php?cid=45

Good Luck and keep us updated!

Teddy
 
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