Broken cam chain = bent valve

[chuck hahn]

Tap 2 one inch putty knives ( one on top of the other ) between the cases and the jugs. These will act to protect the surfaces. Next use a wide flat tip and go between the knife blades and tap the screw driver in some..repeat on the other side of the engine. Going back and forth youll break it loose.

 

[Nessism]

I'd get a block of wood and use it to distribute the load across the fins and then whack it with a hammer to get the cylinder loose. I don't recommend trying to drive something unto the gasket space since it's easy to damage the gasket surfaces that way.

 

[chuck hahn]

which is why you use the 2 putty knives..they go in flat and dont ruin the surfaces...it the screw driver which will jack it all up. Using the putty knives to sleeve the screw driver tip elimintes the gouges and dimples

If youre gonna use a block of wood be damned sure its on a thick and solid spot. Ive snapped fins before that way and was not happy.

 

[Nessism]

The fins are joined together with vertical ribs so to speak, so get a block of wood that's wide enough to span across at couple of these ribs. That way when you hammer the block the load will be distributed across a lot of different fins. Forcing a putty knife between the block and cylinder is a great way to mar the gasket surfaces. It would most likely work but you could also damage something.

 

[chuck hahn]

true enought ed..but MISS just one time or have the wood slip.. if you got straight into the base gasket you wont mar the surfaces..ive done it more than one time.

 

[hannibal]

Thanks guys. I'm going to try more taps with the precision adjustment tool. I could live with a broken fin easier than a leaky base gasket.

 

[hannibal]

The mallet and wood block worked perfectly to tap on the fins without damaging them. I also used the wood block to hammer upward on the top front edge of the cam chain area. Now that I've gotten the jugs loose, I'm finishing up cleaning up all the grime and oil on top of the transmission case. Still need to remove the starter and clean underneath it.

I still can't get the crank to spin freely. The broken cam chain link is bent back on the chain (don't laugh at my crappy drawing) so it won't spin forwards or backwards.

My plan is to leave the jugs on, flip the engine over, and remove the bottom half of the case. I should be able to see what's going on under the crank sprocket. Once I get the broken chain off and assuming the crank sprocket isn't damaged (fingers crossed), I'll reattached the bottom half of the case and turn the motor right side up. Then I can rotate the crank to clean the tops of pistons #1 and #4.

Assuming this all goes well, I'll remove the jugs and pull off the lower case again, and remove the crank to install a new chain.

Thanks again guys!

 

[hannibal]

I've been making good progress this week. Just cleaning and removing things as I go. My last step is removing the clutch basket so I can remove the plate (2 plates?) behind it.

I removed the six bolts, washers, and springs, then pulled off the pressure plate and the plates. Now I'm trying to remove the 32mm clutch hub bolt. The manual says to use a special tool to hold the hub so you can break the bolt loose. How do you guys do this? I've been glancing at it all day and can't figure out a DIY version. Any suggestions?

 

[eil]

This is actually the second time I've seen those screws back out and ruin an engine. The first was when I was helping a friend get his GS700E running again. He was redoing the top-end for some reason I don't recall now and he bought a second-hand set of cams off eBay. Well apparently the PO of those cams took out the bolts and put them back in before selling, but without the all-important red loctite. Neither of us thought to check because we're not engine experts and who would take that gear off a perfectly working camshaft anyway?

Well as you can guess, after little bit of riding, the engine grenaded exactly the same as yours. I went back over to help him disassemble the engine a few days later but eventually lost contact with him. I presume the engine is still torn apart in his garage or he sold it as a basket case by now.

 

[chuck hahn]

Put the engine in 5th gear wiggling the sprocket shaft on the left side while working the shifter lever up. Next get the air impact out and take the nut off the clutch hub. Wiggle the clutch or sprocket shaft to get the tranny back down to neutral.

 

[hannibal]

Time to buy an impact driver since that's what everyone suggests.

Edit: I'm gonna go ahead and ask the next logical question. How do you reattach the nut and torque it to spec (30 lb-ft)?? I guess that isn't a lot of torque so you can hold it with one hand while tightening with the other?

 

[chuck hahn]

Same way except I also wedge a hammer handle between the rear brake pedal and the frame to hold the rear brakes on for that added resistance.

 

[hannibal]

Thanks guys. I made some good progress last weekend. Got the cases split and doesn't seem to be any damage to the lower chain guide bucket. The last 3 or 4 links on the broken chain were folded back on itself, preventing the crank from turning more than a few degrees.

I'm out of town and forgot to save my shopping list to my phone so I can't order til I get home. A few questions on parts: is an OEM cam chain the way to go? Also, I'm considering replacing the guides. Front guide is reasonable but the rear guide (12810-45040) is listed at $350. This can't be right can it?

I'm not planning to replace any of the case seals on the crank, trans, or countershaft. I didn't have any leaks from here so I think I'll be good just reusing the seals.

Any thoughts? And thanks again. I never would have made it this far without this forum.

 

[jdion81]

I don't know if you got the head cleaned up yet, but I wanted to offer what I used to get the carbon off - paint stripper. I used the "premium" kind that will eat/burn your skin through rubber kitchen gloves. I brushed it on and it instantly started loosening the carbon. I let it sit over night and took a nylon brush to it to get it the rest of the way off.

As for the tensioner - I also needed a replacement, the original and the spare that I got with a donor engine had several lateral cracks. I too, almost passed out from the new cost of a tensioner guide. So, I have one on the way from eBay (under $40).

 

[hannibal]

I've been using simple green pro to clean. It's not strong enough for the piston tops or combustion chamber so I'll consider paint stripper.

In my mind, there's no way a piece of plastic can cost that much. Did you buy a new or used one on ebay?

 

[jdion81]

I got a used one. I did ask the seller if there were any cracks in it and they told me that there were not. We'll see what it looks like when it gets here.

Here's another one that I was looking at:
1980 Suzuki GS850 G Cam Chain Tensioner Guide Rail Slider Good Used 119314 http://r.ebay.com/ZRtgow

It looks like it cross references to fit the 77 750 also.

use part number 12810-45040 and then click on "Where used"

http://www.suzukipartshouse.com/oemparts/partsearch/suzuki

 

[hannibal]

Bought used guides on ebay. Both guides for $16. At that price, I can buy all of them and still be cheaper than new guides.

I got the cases apart and removed the broken chain. My plan was to put the cases beck together, turn the motor over, and clean the piston tops. I cannot get the cases back together. If the front closes up, I have a 3mm gap at the back. If I get the back half to close, I have a gap at the front. Got pretty frustrated and took a break. Any tips? And sorry for the stupid questions.

 

[chuck hahn]

Recheck that all the trans bearings are seated properly and the half circle retainer clips things are in right. Also see that the shifting forks are in the grooves on the shifting drum all the way and also into the gears as well.

 

[hannibal]

Thanks Chuck! One end of the driven shaft had moved and it wasn't sitting in the retainer clip.

The journey continues...