First full motor rebuild @ bottom end compatibility

[MotoLife1896]

Hey guys! I’m new to the forum and looking for some advice. I recently picked up a free 2007 CRF250R from a coworker that no longer had interest in the bike after it blew up on him for the second time. I know this is going to be an expensive build but this is something I’ve wanted to do for years and finally have the opportunity. Onto the problem, the crank rod is blown directly up the middle of both the left and right cases so I know they’ll need replacing. Should I send off the head or just order a new one? Pretty sure it’s probably messed up. Should I be able to get away with buying two new engine cases, left and right, a bottom end rebuild kit, top end rebuild kit, new cylinder, have the valves shimmed and be good to go? Again I’m new to this so if I sound clueless please excuse me. And my biggest question, with the purchase or download of a factory service manual and a case of beer, I this something I can do myself or would I be best off going to a experienced repair shop, which is quite costly. I’d greatly appreciate any and all opinions!

[MotoLife1896]

Hi everyone, I recently acquired a 07 CRF250R and I’m curious if it is possible for someone new to the sport to tear this engine down and do a top and bottom rebuild, both crank cases are damaged at the moment so a bottom end rebuild is certainly needed. Any tips and suggestions would be greatly appreciated

[luke428]

A rebuild is really is IF you have a service manual. If not you NEED one.

[MotoLife1896]

A rebuild is really is IF you have a service manual. If not you NEED one.

I CERTAINLY agree! I do plan on ordering the factory service manual soon to make sure everything is done properly because the last thing I want to do is rebuild and then it blows up again[emoji24]

[highmarker]

clean location, clean tools, don't guess if not sure consult the manual or parts fiche. Crf250 is one of the easier motors to do. when you say both crankcases do you mean the inner halves or the outer covers which can be replaced without splitting the cases.

[MotoLife1896]

clean location, clean tools, don't guess if not sure consult the manual or parts fiche. Crf250 is one of the easier motors to do. when you say both crankcases do you mean the inner halves or the outer covers which can be replaced without splitting the cases.

I certainly do appreciate your reply! That’s some really good advice, I see engines like puzzles, if it doesn’t fit, it’s probably not where it goes but I’ll definitely be following the manual every step of the way. Unfortunately it’s both inner cases that are damaged, it looks as if the piston broke off because the rod came up and is sticking out of the back

[Confederate]

Might I suggest you should get a whole nuther engine to rebuild. That one is toast.

[MotoLife1896]

Might I suggest you should get a whole nuther engine to rebuild. That one is toast.

I’ve already tried looking but they are few far between so I’m stripping this one and basically building a new one, new cases, new head, everything

[Dmouse]

 I don't think those engine cases can be repaired, looks pretty rough, hope you got a good deal

[MotoLife1896]

 I don't think those engine cases can be repaired, looks pretty rough, hope you got a good deal

Oh yeah no repairing those! I found a good deal for two new cases on Bike bandit, $400 later but atleast they’re new and don’t have to worry about matching them together

[870]

I would say go for it. Get a manual. Take your time and ask questions. Your going to make some mistakes but that's how we learn.

[MotoLife1896]

I would say go for it. Get a manual. Take your time and ask questions. Your going to make some mistakes but that's how we learn.

I really appreciate your reply! That’s certainly right though, that’s the only way we’re going to learn and I’d feel better riding a bike that I know I can tear down and fix myself rather than calling someone to work on it for me. Manual is definitely on the way though!

[Bruce Martens]

4 hours ago, MotoLife1896 said:

well wouldn't ya know its another wiseco junk shaft. head over to this post to see how we really feel about wiseco cranks lol

 

[MotoLife1896]

well wouldn't ya know its another wiseco junk shaft. head over to this post to see how we really feel about wiseco cranks lol
 

Haha I definitely won’t be using Wiseco anything for this build! I hear Hotrods is the way to go so that’s the direction I’m headed, because, this above, just isn’t going to cut it lol

[yamahadude112]

Just curious but what did you pay for this beauty? Unless you got it for a steal of a price or the rest of the bike is in great condition, this just looks like a big headache, but that’s just me lol

[MotoLife1896]

Just curious but what did you pay for this beauty? Unless you got it for a steal of a price or the rest of the bike is in great condition, this just looks like a big headache, but that’s just me lol

Haha I actually got this beauty for free! It blew up on my coworker twice so he wanted to get rid of it and it’s always been a dream of mine to have one, even if I have to rebuild it, so I gladly took it off his hands

[yamahadude112]

Haha I actually got this beauty for free! It blew up on my coworker twice so he wanted to get rid of it and it’s always been a dream of mine to have one, even if I have to rebuild it, so I gladly took it off his hands

Dang you are one lucky son of a gun, well in that case you got nothing to lose by rebuilding it. Did your coworker ever figure out why it blew up?

[MotoLife1896]

Dang you are one lucky son of a gun, well in that case you got nothing to lose by rebuilding it. Did your coworker ever figure out why it blew up?

I certainly agree! But no he never figured anything out, there’s so many things that I see could have gone wrong though, first there’s a wiseco kit on it lol But I think he left the fuel on when he went to the track and hydro locked the engine, either that or it wasn’t properly lubricated or just wasn’t rebuilt properly, but I’m hoping to tear into it soon and see exactly what went wrong and hopefully not have it happen again

[Bruce Martens]

9 hours ago, yamahadude112 said:

 Did your coworker ever figure out why it blew up?

Well I'd be willing to bet that,just like my bike, the only reason it blew up was because it had a wiseco crank. My wiseco crank, or more specifically the rod, broke 3/4 of the way across at mid rpm and still idled, albeit smacking the head from added rod length. All my bearings still spun freely, no failure other than the rod, also from what I've heard hotrods cranks are pretty good, when I rebuilt mine I put in a stock one from motosport, witch was like $100 off so it was basically the same as a hotrods.

[LSHD]

10 hours ago, MotoLife1896 said:

Haha I definitely won’t be using Wiseco anything for this build! I hear Hotrods is the way to go so that’s the direction I’m headed, because, this above, just isn’t going to cut it lol

For such an important part, why not use OEM? One of the best parts you can get and the extra cost will soon be forgotten when spread out over the many hours it will last.