possible engine seizure... quick question! *Now Screwed*

JohnnySomersett

JohnnySomersett

Active Member
I have a horrible feeling my engine might have seized last night :o

To crank by hand (kickstart is missing) which side cover should I go in to get a breaker bar on the crankshaft? And I'm guessing I need to drain the oil first?

Bike is a 1971 CB250

Thanks in advance.
 
Re: possible engine seizure... quick question!

You'll need to remove the cover off the left side of the crankcase to access that bolt. You don't need to remove the whole side cover, just the smaller circular one up front. Part #4 in this pic: http://www.cmsnl.com/honda-cb250k0-general-export_model15728/partslist/E10.html#results

You don't need to drain the oil but a little may come out that opening, totally normal, so have a tray or something underneath.
 
Re: possible engine seizure... quick question!

HerrDeacon said:
You'll need to remove the cover off the left side of the crankcase to access that bolt. You don't need to remove the whole side cover, just the smaller circular one up front. Part #4 in this pic: http://www.cmsnl.com/honda-cb250k0-general-export_model15728/partslist/E10.html#results

You don't need to drain the oil but a little may come out that opening, totally normal, so have a tray or something underneath.
Click to expand...

Excellent, I kinda thought as much but Im at work going over things in my head. Should be getting out early in an hour or so to start getting it apart.

It happened while moving (about 40mph), just cut out and stopped. The starter motor is just clicking and groaning and rolling in gear just drags the wheel. It has been eating oil recently and I've been topping it up regularly - however, in what short time of light I had last night, I checked the oil level and it was pretty ****ing low!

If I get it unseized with penetrating oil and muscle - is it a certainty that the engine will need major work or is there a chance it'll run fine afterwards? Pretty new to bikes if I'm honest (but good with cars).
 
Re: possible engine seizure... quick question!

If it actually seized up, a proper rebuild SHOULD be done. Sometimes you can get away without it but I wouldn't chance it. Until you get it apart and inspect the possible damage AND determine the cause of your issue(s) there's no real way to determine what all you'll need to do though. Also... Motors don't "eat oil". It either leaks or is getting burnt. Either way its a bad situation.
 
Re: possible engine seizure... quick question!

VonYinzer said:
If it actually seized up, a proper rebuild SHOULD be done. Sometimes you can get away without it but I wouldn't chance it. Until you get it apart and inspect the possible damage there's no real way to determine what all you'll need to do though.
Click to expand...

Thought so. Bummer.

Ah well, good way to learn I guess. Wish me luck!
 
Re: possible engine seizure... quick question!

Well...that's that fucked then.

I opened the left side cover to reveal the rotor, all the oil came out (way more than my little drip tray could handle) and I gave the bolt on the rotor one firm push and the bloody bolt sheered right in half inside the engine. Great.

The other side the previous owner decided to round out half the bolts so much my impact driver had no effect so I can't get that off either.

On the plus, I guess, I can move the pistons up and down an inch by moving the rotor so it hasn't seized that I can tell so maybe it dropped a valve or something. I dunno.

I do know, however, that I'm beyond my knowledge and tools capabilities so an inevitably expensive trip down the garage is on the cards here.

What a crappy day.
 
Its a basic four stroke motor man. Buy a GOOD manual, and a decent set of hand tools and have at it. It won't bite. Document your progress with LOTS OF PICTURES here on DTT and we'll walk you through the tricky stuff. As tasks that require any specialty tools come up you can buy or borrow them then. Seriously, you're doing yourself a great disservice by not at least trying to rebuild it yourself first.
 
I have pretty good tools already thanks to owning classic cars for many years. I don't know why this seems so daunting but it does! Maybe it's the frustration coming out the wrong way, coupled with impatience. I'm gonna sleep on it and step away for a day or two - reset my brain and go from there.

The manual I have is average at best, but there doesn't seem to be many about for it that I can find.

And it does bite... The fist of bloody knuckles pays testament hahaha
 
I have a Haynes manual on paper and a .pdf of the official Honda shop manual. If you have better then I'll definitely have one/them. PM on it's way
 
Well, between HerrDeacon popping a decent manual my way and the local 'old timer' motorcycle shop saying "stop being a pussy and get your hands into it boy!", I've decided to just man up and do it myself :P

Hopefully you guys can help along the way. The shop I know said that if there's any bits that I can't do because of special tools or can't get my head around then just to drop by and get them to help/do it for beer tokens which is nice too!

Look out for a thread coming soon! Ill be pulling the motor out tonight and getting it on the bench ready for the long task.


I have gone over in my head that it might be worth, while it's open, perhaps doing a few small things to increase performance? I've always been a fan of squeezing a little extra out of small engines (in cars) so maybe some jetting, cam change or whatever? Would be nice if anyone has links to people that make performance parts for these engines that I could look at and weigh up the potential? Or, is there parts for others that fit (like, say, 350 pistons in a 250 head etc etc?)


I would appreciate if anyone can list the basic things I should change as part of a rebuild? Piston rings? Gaskets? Valves? etc?
I'd like to renew the engine at the same time as trying to make it work again hahaha
 
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