1985 250sx Seized Engine Teardown

[almac16]

Hi,

I hope someone can help me. Last year my 85 250sx seized up after running dry of oil. I am finally getting around to tearing it down for the rebuild. I took all of the head bolts out, but I am having trouble with the timing chain. My engine is seized solid and I cannot turn the engine enough to get the timing chain bolts out.

How do you get the timing chain bolts out when you are working with a 100% seized engine. I tried a 4 foot bar on the crank and couldn't get it to turn the engine enough.

I also took the side case off, the clutches and don't see how I can get at the timing chain from the bottom end.

Thanks for any replies,

[Yamada]

It's just an idea like thats but cut the chain and buy a new one. It's will cost you some $$$$$$$$$ but i'm sure that it will work.

[almac16]

.......ahhh yes. My brother and I almost did that, then I said I would ask before I resort to cutting. But that would definitely work.

Man, that bike is s-e-i-z-e-d!! I was driving wide open on the road for about 40 miles and it just stopped solid.

I've since bought a 86 250es but can't stand it compared to the sx. Too big and luggy.

I just hope someone can help me and I save the chain.

[Xowner]

well with the fact that the engine locked up with no oil i wouldnt use much outta it and new timing chain would be something i bought new b/c it might be strected from the sudden lock up

just my two cents

good luck!

[kdagenais]

I would recomend replacing the chain anyways because they only are $69.05 from Service Honda. Then you won't have to worry about bending valves cause the timing chain slipped out of time. I will never do another top end rebuild on a 4 stroke without replacing one. Anyway that is my opinion but not necessary right or wrong. Good Luck on the rebuild!

[almac16]

good point on the timing chain. I never thought of that. Does it matter that it seems super tight now before I've taken it off?

[kdagenais]

Does it look tight down by the crank? The reason I ask is cause it is hard to tell on top if it is really tight or not. If you look at the chain with the tensioner in place and then remove the tensioner see how much the guides & chain moves. If it moves a lot (1/2" to 1") I would replace it.
That reminds me did you remove the tensioner to get the chain off?

[almac16]

I do have the tensioner off. I took the side case off etc. I will look again to see how much play there is now that it is off.

I will probably buy a new one I guess. But can you get it apart without cutting the chain? (just in case)

[kdagenais]

But can you get it apart without cutting the chain? (just in case)
Only thing I can think of is soak everything in oil cylinder etc. overnight and see what happens. Other than that I have no ideas. You might have a prblem getting the cylinder off also if it is the piston seized. You might want to consider buying this http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=2477251579&category=43977. You probably wil have the same amount of money wrapped up in it by time your done. Just a thought!

[almac16]

Only thing I can think of is soak everything in oil cylinder etc. overnight and see what happens. Other than that I have no ideas. You might have a prblem getting the cylinder off also if it is the piston seized. You might want to consider buying this http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=2477251579&category=43977. You probably wil have the same amount of money wrapped up in it by time your done. Just a thought!

I might try oil in the cylinder again. I did try that when it first seized, but like I said that was last May.

I just called our local dealer and it's 73USD (or 100CDN for me) dollars taxes included for a new timing chain.

I'd really hate to have to spend that much more on this rebuild. That motor on ebay is way to expensive! I could buy a complete 250sx for that much. Might not look good but it would run.

I actually might be getting another motor from my friend who's 250sx frame broke.

I am going to pick up a factory manual on the way home today and see if it says anything.

I'd really like to get this apart without cutting the chain.

[atctim]

Just an idea, but why not put the Big Red engine in the SX???

[almac16]

Just an idea, but why not put the Big Red engine in the SX???

..i'd love to, but my girlfriend wants to drive the Big Red :)

...and considering she wouldn't get on the sx with me that is a big step!

She finds the Big Red with the racks and everything a lot more stable, plus it is a little wider etc etc.

I'd love to slam the es motor in the sx 'cause it runs mint!

[kdagenais]

I have a feeling if it is the lower end you are gong to be looking at allot more money than you might think. But maybe if you are lucky it is the top end but unlikely. Keep trying to free the engine up by working it back and forth maybe she will free up enough to get the other bolt out of the cam.
Keep Us posted on your progress.

[threewheelin-feelin]

why were u driving it dry anyway lol and what happend to u when it locked up did u go flying lol

[JoeSuzuki]

Try and unseize before repairing, that way youll know if something got damaged before replacing it.

Put diesel in the cylinder for 3 days, then use a tork bar on the flywheel. It works 99% of the time. Especially since its freshly siezed and didnt get time to rust.

[almac16]

why were u driving it dry anyway lol and what happend to u when it locked up did u go flying lol

Well the bike had a little leak on the oil line. I filled it up in the morning about 7am and went on a run. Every long weekend in May there is a big rally here in Nova Scotia. Well it is an all day event and the bike never stops. I didn't think it would ever leak that much oil, but I guess I was wide open all day. At the end of the rally we were about a good 30 minute wide open drive away from home and we hit the road.

when it seized I just skidded for about 30 ft, I actually was able to pull the bike over to the side of the road while skidding.

My friend with a Honda 350 4x4 blew a 4 inch hole in the side of his brand new FMF pipe, and the other guy with us on a honda 250EX came out of it fine.

It's really hard on the bikes going wide open for that long and I guess I learnt my lesson.

I was hoping to get the sx going to the rally this year on May 22.


Regardless I will be taking the 250ES if I don't get the SX going.

I was suppose to be working on it tonight, but I changed the brake shoes on my friends truck instead.

Tomorrow, I guess.

[almac16]

Hi,

I got the timing chain off. I put the impact gun on it the crank and worked it back and forth enough to get the chain off.

Well I got the head off and it is A-Ok.

It was the crank shaft bearings that are shot and jammed the crank.

Is this worse than having a piston jam up????

I hope it doesn't cost much more.

[kdagenais]

Congratulations on getting it apart! I am not an expert by any means about lower end rebuild on motorcycles. I have only one that went out on me and it wasn't worth fixing anyway. If I had to guess you will probably need all new bearings and possibly a new crank & rod. I am not sure if motorcycle cranks can be turned or not. I am sure somebody on the board here can give you some direction. At least you know what you are in for from here.
Good Luck and keep us posted on your progress.

[hondaATCman]

Hi,

I got the timing chain off. I put the impact gun on it the crank and worked it back and forth enough to get the chain off.

Well I got the head off and it is A-Ok.

It was the crank shaft bearings that are shot and jammed the crank.

Is this worse than having a piston jam up????

I hope it doesn't cost much more.

Ahhh man, that really sucks!! I would rather have a piston sieze before crank bearings any day. Now you gotta split the cases, take the tranny out, pull the crank, and replace the bearings. I would recommend send the cases and crank to a professional shop so they can fit it with new bearings and seals, press and true the crank and match it to fit in the cases. And it you never done this before, you will need a manual!! Good luck!!

[almac16]

I am buying a second hand crank that seems to be in excellent shape.

I already have the cases almost split (all bolts out and ready to go)

I have a clymer manual AND a OEM Honda Manual.

Between the two of them I should be able to get it back together again.

Does this sound like a good plan? It must be easier to just put in a new crankshaft that already has the bearings in place then it would be to press in new ones?