Rando or anyone else who can answer this i would appreciate it. I am in the market for a 250-450cc used dirt bike. Almost everyone i see that is more than 3-4 years old has "fresh rebuild" or "rebuild XX hours ago" in the sales description. Are these newer 4 stroke liquid engines that prone to failure or is everyone riding the piss out of them? I recently sold (should have kept) a honda crf230 with over 100 hours on it and it ran like it was brand new. I have a 2000 XR70 that will not die either for my kids I had a 1990 Honda 300 fourtrax with countless hours on it and still runs fine. I did blow up a sea doo xp before but that was due to a poor oiling design on their part. I have seen a few that are for sale with bad engines. I am on the fence of buying a newer one or one that i knows has issues so i can fix it correctly. Thoughts?

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Posted by MrBobDobalina

BRo.LA

Member since Oct 2011

2991 posts

Posted on 11/30/20 at 12:00 pm to bayou choupique

If you're talking about a racing dirtbike (CRF, YZ, RMZ etc.) then yes those engines get the piss ran out of them bouncing off the rev limiter nearly every time they are used. If you are talking about the 230cc bike you had before its a different type of riding all together and those engines can last the life of the bike without being rebuilt. 4 strokes normally run 75ish hours before needing a full rebuild and it will cost you north of $1000. A 2 stroke needs a rebuild around 50 hours but will only set you back the cost of a piston and some rings (~$200)... I'm team 2 stroke all the way for the record. Way less moving parts, way more badass, and much much much easier to rebuild and service [no valves!!!]

The trail bike engine you had vs the race engine of a motocross bike is something like a minivan compared to a viper. Totally different engines designed to operate at different ranges, which drastically reduces the life cycle of the engine.

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Posted by X123F45

Member since Apr 2015

27392 posts

Posted on 11/30/20 at 12:12 pm to MrBobDobalina

Basically everything he said.

The newer 250 motors are even more impressive. My little cousin has one and it revs well over 16000 rpm. That's insane.

Used racing dirtbikes are always a roll of the dice when you buy them.

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Posted by bayou choupique

the banks of bayou choupique

Member since Oct 2014

1818 posts

Posted on 11/30/20 at 12:58 pm to MrBobDobalina

quote:
If you're talking about a racing dirtbike (CRF, YZ, RMZ etc.) then yes those engines get the piss ran out of them bouncing off the rev limiter nearly every time they are used. If you are talking about the 230cc bike you had before its a different type of riding all together and those engines can last the life of the bike without being rebuilt. 4 strokes normally run 75ish hours before needing a full rebuild and it will cost you north of $1000. A 2 stroke needs a rebuild around 50 hours but will only set you back the cost of a piston and some rings (~$200)... I'm team 2 stroke all the way for the record. Way less moving parts, way more badass, and much much much easier to rebuild and service [no valves!!!]

good point about the crf230, the engine looks and sounds a lot like a 250/300 atv motor which is bullet proof. the crf 230 was not that fast but i guess the trade off is the reliability. I did ride a newer crf250r last weekend and holy schitt it was fast compared to that 230. a guy i know down the street has a newly rebuilt cr85, that would be a fun little bike to play around with.

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