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Engine seized, hope not!!

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Here’s the story, my son just purchased a used CRF250, and valves were supposedly recently done. On his fifth ride, the bike starting making noise so he shut it down & pushed it home. Got home tried to re-start and it bearly did. Put it away for the next day. By the time I got home the engine was locked up.

I want to take the head off but can’t get it to TDC. Can I simply loosen the cam chain & carefully remove the cam? I’m assuming its under some spring load.

Also I plan to pull the clutch side off just in case some went wrong there.

I’m new the 4-stroke re-build game, any help would be appreciated. Even I don’t want to risk putting it back together on my own yet I hope to save a few $$ for him from the shop.

John

hey i am the son who was ridding it, well out in the woods the bike stalled, but then it took a long time to start it up, the throttle had to wide-open and it finally started then to get it to move it had to be revving high and with the clutch half way. then i heard metal clank so i shut it off and walked it a good 3 miles, but i still could kick the engine over for the rest of the day but it wouldn't start up, so the next day i was trying to start it up again but then is locked up after a good 10 kicks, and now i wanted to take the cam apart but the notches are not lined up, can i take it apart still?? or will it have to be reset with the bottom end??

Nick

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You don't have to be @ TDC but like you stated the lobes may be compressing the springs.

Hopefully you can release the tension on the cam chain after removing the tensioner. If not try rocking the bike backwards in gear. You should be able to get it to move enough to relieve some tension on the cam sprocket. Then you can slide the cam bearing over to get the cam out.

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four strokes are pretty easy. when you have no fear of getting into it.....the valves and clearances are a wierd know how but with research its easy to learn......about the bike sezing up i dont know....open it up and figure it out i guess

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as for it seizing up, its possible that as it barly started it could of hydrolocked (to much fuel in the jug), removing the spark plug will allow you to get at tdc if it has hydro locked.

even if the orginal owner had new valves put in if they didnt have the seats cut or he lapped the stock titanium valves ( would of removed the coating) the new valves wont last very long at all.

any information on the bike as for model age 04,05,06,07,08 etc.

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I strongly suggest buying a Honda service manual these are expensive engines to maintain and you want to put it together correctly. Remove the cam chain tensioner. Use caution on next step! Remove cam bearing covers and don't let bearings clip on bottom side fall into engine. Also remember which cover is right and left they must go back in same place. Lift the cam and slide to the left and you will get enough slack to remove the chain. Make sure to align the TDC marks before putting it all back together.

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hope you did not do an oil change and put oil in the wrong side.sometimes if you run it without oil the camchain guide melts to the chain when it cools it will not spin over let us know what you find.

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hey i am the son who was ridding it, well out in the woods the bike stalled, but then it took a long time to start it up, the throttle had to wide-open and it finally started then to get it to move it had to be revving high and with the clutch half way. then i heard metal clank so i shut it off and walked it a good 3 miles, but i still could kick the engine over for the rest of the day but it wouldn't start up, so the next day i was trying to start it up again but then is locked up after a good 10 kicks, and now i wanted to take the cam apart but the notches are not lined up, can i take it apart still?? or will it have to be reset with the bottom end??

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2006 CRF250 we've done 2 oil changes since we got it, on 5 rides. The weird thing is that it did not lock up initially. Going to get the clutch side off next before ripping the head off

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here's the update, its the valves. I reached around the intake lobe and felt a divit in it. Just need some time to tear it down this weekend.

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OK its not the valves, that notch as say is for the decomp-mech.

Stripped it down to the case and its in the crank. Took the clutch plates out and tranny shaft spun no problem. So I'm looking at splitting the cases. Found another good documentation on

https://www.crfsonly.com/forum/viewtopic.php?t=24959&view=next&sid=095f711da6f500796edde96422f74ddf

a real horror story, but a real good read and lots of pics.

Anyone split a case?? seems to be long & tedious but it can be done on the garage bench.

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These cases are very easy to split. The only special tool you really need is a flywheel puller. A few hits with a plastic mallet and they fall apart.

I suggest you get a shop manual. Don't forget to remove the trans drain plug when you split the case. It holds them together also.

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So I'm planning to attack the case split and rebuild, hope to get the manual today and clear the work bench tonight.

Any recomendations for or against any parts? I figure to go for OEM crank & bearings. We'll replace the piston, I've always used Wiseco. I was also reading about the "dry fitting" the piston. From what i can tell the new piston is put in dry or with some type of "dry" lube. This I suppose seat the rings better???? Sounds just weird but I don't know.

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Heh TJ, have you used cylinder honers??? When i did my first CR85 rebuild I brought it to my local shop to have looked at. The blessed it and honed it out. Ever since then 5 or more 2-stroke top ends rebuilds at home I've been looking for one of these.

I also am leaning towards OEM parts simply because if I get in too deep I may have to have the shop help me out. I figure they'd look more kindly on me if they get all of my business.

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So I'm reading like a ton of threads, how difficult is to open up the cases, do I really need any special Honda tools or just a flywheel puller?

On the clutch I've always simply put the bike in gear with it on the wheels to loosen the basket screw. It always worked quite easily. Anything wrong with that technique???

And finally does the crank need to be pressed in??

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Getting the clutch basket off is proving to be a bear! Tried at first with bike in gear, brake on as I usually do & nothing. Got the Motion Pro clutch holder tool and even with that and bike in gear on the brake still coudn't budge it.

This Saturday for sure what ever it takes it'll be off. I ahve an impact tool but would rather not not have to use it.

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