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HELP - need help picking an engine

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Not entirely sure if this is the correct place to post this or not but i need some opinions. 

 

BACKSTORY: I ride all desert (mostly ocotillo wells) and I've ridden the same 07 crf250r for the past   err  maybe 6-7 years (im 21 so most of my "riding life", fresh off a xr80 to the crf) and I do all the regular maintenance stuff one is supposed to do; clean air filter every weekend and oils and filter change every season (i don't ride that much), and everything has been awesome until the past few years. Within the past few years I have put two pistons and a crank in the bike and the rod bearing on the crank just went out again   its gonna need a piston, cylinder, crank, oil pump, etc etc. I think this is due to me seeking more power now that I'm a lil more experienced and heavier, so I'm probably beating on it a little more now than I used to. Worst part is i couldnt even get a season out of the last piston i put in er... I understand its a race bike and the manual says the pistons only supposed to last 10 hrs but I'm tired of dumping money into this engine, but I love the rest of the bike.

 

PLAN: rebuild the crf, sell the engine, stuff a 2 stroke engine in it. I know a guy that welds aluminum so changing engine mount locations won't be a problem, nor would any mechanical or electrical issues. Intake, exhaust, and sprocket positions might be a bit concerning though, but i bet we could cook something up. I like the idea of a power band, and I've heard that 2 strokes are more reliable (generally) and cheaper to rebuild, so that sounds awesome. 

 

QUESTION: what 2 stroke engine should I get??? a cr250 makes sense cuz honda, but I'm hearing people sing praises of the yz250 as well. Or maybe I should go for a 300 two stroke! I don't know... Would I actually get the more power? plz halp! Thx.

Edited by SandSoldier

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also anyone want a freshly rebuilt 07 crf250r engine? lol
2001 CR250 engine, send it to eric gorr and you will have a beast of an engine depending what porting you do.

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Putting a 2 stroke engine in a 4 stroke chassis is major surgery.  The frame has to be cut in several places, the cradle will need to be opened up to fit the exhaust.  It's a lot more than altering engine mounts.  

Why not just sell the bike as is, and start over?  There is nothing special about an 07 crf chassis, or engine.  I think it will be a ton of work, and very expensive.  Why not just sell it and buy an 04+ CR 250 if that's what you want?  Better bike than what you can build,  and much less prone to failure than a frankenbike.

I appreciate a project, but the logic just doesn't line up here.  You'll be lucky to sell the rebuilt engine for what the rebuild will cost, and have a butchered chassis that may, or may not crack and fail.

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Sell it, buy a KTM, Husky or Beta 250 or 300 and never look back.  The Yamaha YZ250X is another good option.

If you are on a budget and can't buy new, consider an older but clean Yamaha YZ250.

Doc

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Unless you can find a cr500 engine to stuff in there. Then it's worth doing just for the entertainment value.

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thanks guys! if it requires more than just engine mounts and exhaust work i may consider another bike, I was under the impression that cr and crf frames were pretty similar.

also i think a cr500 may be a lil much for me lol

Edited by SandSoldier
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Sell it and start over. The frames/parts do not swap. 

 

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If you are rebuilding it regardless I would make sure it is done right and keep riding it. How often are you riding? A seasonal oil change probably isn’t cutting it unless you are going out 2-3 per season. Those bikes do not hold that much oil do they?

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Yeah, my friend talked me out of the swap thing. Along with the fact that the exhaust would be   well    interesting    to work out, resale value would probably tank. Not sure exactly how many hours we put on a season, my next bike will have an hour meter for sure. The thing that gets me is I rode more and maintained the bike less for the first half of the bikes life and aside from having to put valves in it ONCE, it's been dead realiable, but now its just been a mess and i ride less and maintain it more

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3 minutes ago, SandSoldier said:

Yeah, my friend talked me out of the swap thing. Along with the fact that the exhaust would be   well    interesting    to work out, resale value would probably tank. Not sure exactly how many hours we put on a season, my next bike will have an hour meter for sure. The thing that gets me is I rode more and maintained the bike less for the first half of the bikes life and aside from having to put valves in it ONCE, it's been dead realiable, but now its just been a mess and i ride less and maintain it more

Old 4 strokes wear out.  Sounds like you were thinking right when you said full rebuild.  Might be close to the value of the whole bike.

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On 6/29/2018 at 8:45 AM, Doc_d said:

Sell it, buy a KTM, Husky or Beta 250 or 300 and never look back.  The Yamaha YZ250X is another good option.

If you are on a budget and can't buy new, consider an older but clean Yamaha YZ250.

Doc

+1 on the YZ250 if you are on a budget. You can get them used for a reasonable price and anything from 2006 and up is great. Even the 2001-2005 are great if you revalve the forks. The engines on these bikes are pretty bulletproof. There are tons of good used parts available at low prices. Aftermarket tanks (larger for desert) are plentiful. Simple and cheap to rebuild. Excellent powerband that can be tuned by simply changing the timing (retard 2 degrees to take hit for woods riding and get a bonus of huge overrev). 220 pounds ready to ride (one gallon of gas).

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+1 on the yz250 idea. Anything 02+ is AMAZING! Ive become a way better woods rider coming off an 06 yz250f. You have to work more on a 2 stroke but the power and the million different things you can do to them is the best part.

About the crf issue. Rebuild and sell it but i will let you know now, YOU WILL LOSE MONEY on it for sure. My dad is currently trying to sell his 06 450r and has had to basically sit on it.

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oh man you guys are scaring me lol. I was thinkin about $700 piston crank cylinder etc (doing all work oursevles), list er for $3500 "freshly rebuilt etc etc" and see where it went from there. Am i crazy here thinkin i can get in the 3ks for it??

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oh man you guys are scaring me lol. I was thinkin about $700 piston crank cylinder etc (doing all work oursevles), list er for $3500 "freshly rebuilt etc etc" and see where it went from there. Am i crazy here thinkin i can get in the 3ks for it??

700+ just for the top end (since you need a cylinder). Not including any of the bottom end stuff like crank, bearings, seals, etc. i can tell you now you wont get $3k anything for it. Newer bike 14> are going for around $3k-3.5k now if the person isnt trying to get a fortune for their bike. I would expect around $2-2.5k for it...

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Sell it and buy a proper 250 or 300 2 stroke. Beta or KTMs for trail style riding
If you like MX bikes than 04-08 RM250. 05-present YZ250. Any others... have the motors ported by Eric Gorr and you’ll be fine

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