Freeing a Seized engine.

Hi,
I have got myself a cheap '76 Z650 but the engine is seized.

I have the head off and the pistons seem in pretty good nic, but the bike has been sitting around for a long time and it has seized from standing.

The two centre pistons seem to be at TDC which I believe is making it harder to free them up.

I have left them sittting over night with oil in the chambers (as much as I could get in to chambers 2&3) and I still cant get it to turn over even with some gentle taps with a mallet on the pistons.

Does anyone have an idea??

A little rust in the cylinder bores can make the cylinder a chore to remove! First make sure it isn't the base gasket holding the thing together. Then, get some PB Blaster at Walmart and spray some on the crowns so it has a chance to soak in... hopefully it can make its way past the rings. PB Blaster is FAR more likely to loosen things up than is regular oil or WD40, etc. If that doesn't work, try a torch; heating the aluminum around the pistons. Be careful so as not to get the thing red hot and warp the cylinder. Try tapping on the piston crowns GENTLY as you turn the 17mm nut on the crank... hopefully the rust isn't deep and will break loose.

What is PB blaster? would it go by a different name here in Australia?

I don't know the names of products in Australia, but you'll want to use a high-quality penetrating oil. A machine shop should be able to recommend an appropriate product to you. Good luck!

Formerly from Australia. I recall using a product called Penetrene which I think I got from Repco to free up a stuck 2-stroke motor. Used it for a lot of stuff like WD-40.

You may have to be patient, sometimes days, giving a squirt, waiting, tapping gently etc, putting a LITTLE heat on it, squirting some more.

www.pbblaster.com/display.cfm?p=1661405D...3E7-89EFB7A4DF1892A9

The above link lists US retailers sellig PB Blaster. Couldn't tell from their web site if they sold overseas.

You can try KROIL too. It's GREAT STUFF !!!

KROIL is good stuff but it stinks like none other. I have only used it a few times as a guy that I worked for had a can of it that was ancient, I didn't know you could still get it. I've never seen it in the stores. A trick I have used is to fill the cylinders with Marvel's Mystery oil and let them soak for a couple days, refilling the cylinders as some may leak past a piston. Another product you might try that is similar to WD-40 it is called S'Ok I don't know where to get it and it is VERY expensive 8-10 dollars for a 8 oz can. But it is the best penetrating oil I have ever used.

another thing you could try is to fill the crankcase up full with penetrating oil. Not sure what you have in Australia, but, here, WD-40 is available in 1 gallon cans. part of the problem might be that the crank bearings are seized to the crank. I am not sure about the KZ's but I would guess that the crank and rod bearings are similar to those in a regular engine, being just a piece of steel, and not roller, or ball bearings. if this is the case, then filling the crankcase up completely full would allow those parts to soak as well, making it easier. also, if the engine is frozen to this extent, I would imagine scarring ont eh cylinder walls and I would say that it shouldn't be run in that condition, that the engine shoudl be torn down the rest of the way and rebuilt. Not sure of your intentions, but if it was just to run it after freeing it, then, bad idea.

I have used Kerosene to free up a car motor. Let me know if it works.

Rather than using a wrench to turn the motor, you might try using the kickstarter as well. I had luck in college getting a kz650 unstuck by letting it soak and then repeatedly jumping up and down on the kicker...

I then proceeded to run the motor for 1.5 years until I wrecked the bike with no additional work. The 650s are amazingly tough. I can't reccmoned this, but it amazes me how tough these motors are.

Z Parts wrote:

I have used Kerosene to free up a car motor.

I have too. If you can get it in a higher gear like 3rd or 4th and it's had kerosene in the crankcase and cylinders for a day or so?
Maybe you can "rock it" and break it free.
Worked for me once.
good luck


Post edited by: ~DW~, at: 2005/10/28 03:28