CL350 seized engine

[Davidov]

I got a complete 1969 CL350 with a seized engine.
I need some input from CL/CB twin gurus.

It had been sitting for an unknown number of years, so I figured the pistons were seized in the cylinders. I haven't ruled that out.

I removed the starter just to see if it was maybe stuck, causing the motor not to turn. I removed it, and still would not turn.
I noticed the starter drive was completely missing from the inside of the case.
I did fish out the drive chain, and it seems to be in tact.

Is this a common problem? Could the starter gears have falled into the bottom end and seized something?

 

[Davidov]

Here's a close look.

 

[Big R]

It probably fell when you pulled the starter motor out. Have you not pulled the left side cover from the engine?

 

[Davidov]

That's my next step, remove the cover to look for any loose objects.

Shouldn't the gear stay in place when the starter is removed?

 

[Big R]

It's been a while since I worked on a 350, but I believe the cog just slips over the starter shaft.

 

[BCBarker]

Big Rich is right. There is nothing holding the starter gear on the shaft so when you removed the starter motor and shaft, the gear just fell down.

 

[Bobdot]

what happens when you kick it over (with your foot)? good indicator of the overall condition.

bob.

 

[Davidov]

Kick starter doesn't move at all.

I managed to break the bolt that holds the generator in place. Looks like I'm pulling the complete engine now!
Here's a visual aid of the complete bike.

 

[Big R]

I would keep the engine in the frame unless it's REALLY seized up. Try putting some penetrant in the bores and letting it soak. If you can un-stick the motor now, it will make the tear down easier.

Here's an article on penetrants:
http://grassrootsmotorsports.com/tech-tips/55/

 

[Davidov]

Thanks, Rich.
I did penetrant oil, ATF, Acetone, and Engine oil. (at different times)

It's pretty dang seized. I took the top "acorn" nuts off the top of the valve cover, and then cranked the generator bolt.
The pistons are seized so much that is was actually lifting the cylinders/head off the bottom end!

Out comes the engine!

 

[Big R]

Do you have access to Aero Kroil? It can be tough to find sometimes.

There was a thread somewhere (I think it was either Swan or Speedfiend) that went into pretty good detail on a different way to un stick a piston. It involved pouring something (I forget what exactly and don't want to guess) on top of the piston, letting it soak, then lighting it on fire. The heating/cooling cycle broke the piston free.

 

[Davidov]

I did see that. A guy did it on a BSA engine that had been sitting for 40 something years.
I figure the slow, uncompressed burn of the fluid will not harm the engine.
Another trick I want to try is smack the piston with a wooden dowel or hammer handle. Gently of course.

 

[djelliott]

A lot of it is just soak and wait. I freed one up after letting it soak for awhile by using a strap wrench on the generator rotor. When it's all said and done you'll of course need the cylinders bored and some new pistons.

 

[VonYinzer]

Ya, soak and wait... If you pull that motor and try to break it all free youre going to damage something. Maybe break a cooling fin or some other fragile alloy bit. Force isnt the answer in this case. Also, not sure if you planned on it but pull the bottom end apart too. If enough moisture and whatnot got into that motor to stik the pistons that bad, the bottom end will likely have some big issues as well.

 

[Davidov]

I wore myself out beating the piston that was seized.
Unfortunately the spare CB350 engine was seized as well. It had to be driven out as well.

 

[Davidov]

I finally got around to measuring both my original CL350 engine and the spare CB350 engine.

I honed the cylinder before taking measurements, to remove rust and also to take note of any out-of-round spots.

There was a cracked cylinder in the CL, which was a result of BEATING the seized pistons out.
The CB engine had a severely rusted cylinder, which left a nasty corroded mark on the cylinder wall.

After honing, and taking all the specified measurements, I found there are two usuable cylinders. Bore, Taper, and Out of Round all measured within specs per the factory service manual.

I need to measure the pistons now to see if any are usable. If not, I can buy a set of STD sized pistons with rings.
AMIRITE? (Am I right?)

 

[Wee Todd]

big man is right,,,,re attach the top end.........fill it with diesel fuel to the top...the top! let it soak and shock load the crank

 

[Davidov]

Is there anyone that built a 350 engine that can advise me on pistons?

 

[SONICJK]

Pistons are easy to come by.
Check ebay they have some cheaper ones if you want to bore your engine a little.
You can also order Honda OEM pistons.
Bikebandit had the OEM ones for 61.73 apiece.
http://www.bikebandit.com/houseofmotorcycles/1968-honda-cb350/o/m9109#sch394881

 

[legendary_rider]

Sirius consolidated in Cambridge Ontario sells race pistons for $100 for the pair. They're the cheapest on everything I found. I ended up buying 67.5 overbore from Todd Henning Racing though for about $450!