Froze Pistons

[mattsch]

So I'm working on restoring a 68' CB160 with my kids, and have a couple of quesitons. The pistons are frozen. I have tried the PB Blaster-rocking-it-back-and-forth thing, and haven't had any success, so we've decided to crack the case open and try and tap the pistons free. The issue we're having is that the Cam Chain master link is not visible to take apart, (hence I cant get the heads off). Anyone have any suggestions for me as to how to actually get to the Pistons? Please let me know if this is a dumb question, as I'm pretty new to this, and have only been reading the manual, which seems more for bikes that havent been sitting for 25 years...

Thanks guys!

 

[Sonreir]

If you can find a replacement cam chain, the simplest and easiest solution is to just cut it.

Barring that, squirt a combination of diesel and ATF into the cylinders and heat the engine up (either use a blow torch or actually light up the diesel/ATF combo). The heat cycling will allow the diesel and ATF into the micro cracks around the pistons and may help free it up.

 

[Sonreir]

Also... I'm not sure it's the case for the CB160, but can't you just remove the cam sprocket from the cam and slip the cam out without having to break the chain?

 

[650hardtail]

heat cyls w torch till nice and warm

 

[ProSimex]

If it went on in one piece, it'll come off in one piece.

 

[mattsch]

I have taken off the left side case, and was going to pull the chain out that way, but the master link on the smaller chain is connected to the "back side" of the chain, and there isnt enough room to pull the link out towards the case. So you guys are saying if I do get the smaller chain off, I can remove the cam from the side case, correct?

 

[mattsch]

Got it!!! Thanks for the help!!!

 

[ProSimex]

There ya go!

 

[mattsch]

So I got the pistons free. Next question is "what now?" The pistons will go down all the way, but when going upward, they get tight, and stop again. Is there a product I can put down into the cylinder to clean out all of the carbon build up? I'm assuming that is the issue when the pistons are going up. Figured I'd add a pic of the fire, since all fire is awesome...

Thanks again for the help!!!

 

[Sonreir]

You can seafoam the engine to remove the carbon build up, but if the pistons were stuck to begin with, you're almost definitely going to need an hone and new rings. You may even be looking at having to bore the engine and get new pistons. Find the specs for your cylinders and bring them to a machinist.

The machinist will do the honing and then measure to spec to ensure everything is OK.

 

[ktree]

So I got the pistons free. Next question is "what now?" The pistons will go down all the way, but when going upward, they get tight, and stop again. Is there a product I can put down into the cylinder to clean out all of the carbon build up? I'm assuming that is the issue when the pistons are going up. Figured I'd add a pic of the fire, since all fire is awesome...

Thanks again for the help!!!

Yeah, at least get it honed and re-ring it.
As far as de-carbonizing is concerned, these products have changed my life

http://www.google.com/products/catalog?q=omc+engine+tuner&hl=en&client=firefox-a&hs=d7D&rls=org.mozilla:en-USfficial&prmd=ivnsfd&bav=on.2,or.r_gc.r_pw.&biw=1280&bih=881&um=1&ie=UTF-8&tbm=shop&cid=657991433842015278&sa=X&ei=RBZhTqvuK8Hd0QH3kokY&ved=0CF4Q8wIwAQ

and for continuous treatment (so it will never happen again)
http://www.simyamaha.com/category_s/1725.htm

 

[teazer]

I would remove the barrels and pistons and examine the mess. Pistons can be cleaned quite effectively with a wire brush and simple green. For the barrels, clean out as much of the coagulated gunk with a soft scraper (eg hard plastic ruler) then get a 3 legged hone form Sears, coat hone stones with WD40 or kerosene and run it up and down a couple of times. You are not trying to remove metal - just enough to clean up the surface so that you can see how bad the corrosion holes are.

Then you will know whether it's a disaster that needs a rebore or if it will work with fresh rings.

 

[mattsch]

All good suggestions! I ordered some of that Tuner Spray, and will try taking out/cleaning the pistons first (I like the idea of only needing new rings if possible), since i'm poor...

Thanks again!

 

[teazer]

The barrels just lift off once you break the seal with the base gasket, then remove circlips and push out wrist pins.

 

[mattsch]

Got the motor apart last weekend, one of the pistons was blown out on the bottom side, literally cracked and Convexed, (hence the sticking as the piston went up into the cylinder)! A friend of mine who is an airplane mechanic picked up a batch of parts to run through their parts cleaner for me this week. My question is, Does anyone have any suggestions for a good place to get the cyliders honed around Milwaukee? I was thinking Competition Cycle on 124th, since its close to home, but if anyone has anything better to say about another place, I'd apreciate it!
This was my first engine dismantle, hope the "putting-it-back-together" goes as smoothly!!!
Thanks!