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crf250r bottom end rebuild.
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Posted by: justin1022---------------------
hey guys i picked up a cheap crf250r. only problem is it has seazed bottom end. i was wondering if anyone hear could help me out on what the problem is. i think its the crank but i dont no much about these bikes. also i am going to be pulling the engine soon but have never pulled a engine on a machine with a rad. so i was wondering if you just drain the rad fluid then disconnect all the hoses?
right now i currently got a brand new trx450r with maybe half a hour on it and a 400ex done right up that will beat almost any 450 ive raced so far.
Posted by: gregorious77---------------------
yep as you said drain off the fluid and disconnect the hoses.
Posted by: justin1022---------------------
kp and also do you no anything about these bikes the year is a 2004. any particular problems? and would you think its the crank? it has a hot cam in it im not sure what stage though.
Posted by: IndyMX---------------------
There's only one way you will ever really know for sure what the cause of the problem is..
Tear it down and look.
Do you have a service manual? If not, get one. By the sounds of it, you've never had one apart, so it'd be in your best interest to have the manual handy.
Posted by: Matt90GT---------------------
yup buy the manual. period.
Posted by: whenfoxforks-ruled---------------------
You really do not even need all the special pullers. A shop manual, and it almost comes apart by itself.
Posted by: justin1022---------------------
ha im only 15 and your right i never had a 250 or 450 apart. i can rebuild my 400exs top end though and i have a friend that had a trx450r and he blew the crank outa it like 6 times because of it being a 480. so if i run into trouble he could help out. i am defenetly buying a manul though. i have one for my 400ex and it helps out alot. that would sure be nice if some outside gears just pilled up or somthing easy ha.
Posted by: _JOE_---------------------
I would also replace the cam chain and tensioner/guides while you're in there. Be aware this bike is ALOT more maintenance then your 400ex/450r. Check the valve clearances and change the oil often. Be particularly anal about keeping dirt out of the engine.
Posted by: justin1022---------------------
ok ill check it all out i am for sure redoing the valve clearence. and oil i herd has to be dropped out of these bikes every 8 hours. is that about right?
Posted by: IndyMX---------------------
I change the oil in my 450 about every 3 rides..
Remember, there are separate oil for the engine and transmission.
Don't drain both and forget to fill one..
Two drain bolts, two fill holes.
Posted by: justin1022---------------------
ok. thanks. also, is it worth it to bore out these bikes?
Posted by: whenfoxforks-ruled---------------------
Sure, but it will shorten the engine life. Check out what Eric offers, http://www.eric-gorr.com/
Posted by: justin1022---------------------
ok thanks. i was on ebay and its like 600$ for a athena kit but i would rather not get athena. i guess il have to do some research before i spend that kind of money to up it 40cc.
Posted by: Ol'89r---------------------
For reliability, keep it the stock bore.
Add a high compression piston and a stage 1 Hot Cam and have someone with the proper knowledge and tools go through your cylinder head and do a valve job and set it up correctly. An FMF power bomb header and 'Q' silencer makes a great package and produces excellent torque.
You can buy a complete crankshaft from Service Honda at a discount. Click on the link on the left side of the page. You can get your piston, timing chain and gaskets from them also.
Like others have suggested, buy a manual. Read the manual cover to cover a couple of times. It will tell you everything you need to know as to how to remove your engine, disassemble it and reassemble it.
If you have any questions that the manual doesn't answer for you, ask in this thread.
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