1981 GS 750 cam chain broke in 1989

[GregT]

Only in the Nortern Hemisphere Paul.....works fine down here.

Seriously, the hardest part of assembling a multi cylinder bike motor is fitting the barrel over the pistons and rings. Doing this first, one cylinder at a time, then attatching rods to crank while it sits in the top case bearings is so easy you'll see one reason why everything now is plain bearing cranks....

 

[laverda1200]

Hi Greg

too late for me, maybe next time. I have already buttoned up the bottom end. Roller bearing crank engine habits.

I typically bend up wire piston supports to keep the pistons from moving around, attach stainless steel hose clamps around the rings, then lower the barrel and tap gently. Worked fine on the KZ 650 engine I just rebuilt, anyways.

this evening I am doing my craft project of making a new cylinder base gasket for the Suzuki motor out of high temp gasket sheet (the stuff they replaced asbestos sheet with) as I am not going to use the Athena kit base gasket, then I'll put the barrels on and stick the partially completed motor back in the frame before finishing the head. The carbs are completely rebuilt, all I need to do then is find an inexpensive used exhaust system to be able to try and fire the engine for the first time since 1989....

Paul

 

[laverda1200]

cylinder base gasket made, pistons all cleaned in my ultrasonic tank, barrels fresh out of my parts washer tank, local Suzuki stealer wants over $200 for a set of piston rings, so measured existing ring end gaps, all fine, and will re-use the rings, ready to slip the barrels on......see attached photo

Paul

 

[dueller]

Wow that came out beautifully cleaned! Jealous that you have an ultrasonic cleaner at home shop! Used on to clean out a float bowl on a Yammy XS 400 that I bought. Worked great after only 10 minutes in the tank!

 

[laverda1200]

Hi Dueller

yeah, the photo clearly shows how well the pistons cleaned up, what the photos don't show is that the underside/insides/ring lands of the pistons are all as clean as the outside.

a couple of the most used tools in my home garage are the recirculating parts washer tank (about $200 plus solvents) and the small but heavy duty stainless steel ultrasonic tank (about $400 but Chinese knockoffs can be had for $75 or less). Also useful is Gunk Hydroseal http://www.gunk.com/products/cat_PC_PW.asp to soak carb bodies, pistons, pretty much anything. Those pistons in the photo all spent 24 hours soaking in Hydroseal before they did several cycles in the ultrasonic tank.

I also soaked the cylinder barrels for 24 hours in Hydroseal, then thorughly washed them off in the parts washer tank, I did both crankcase halves in the parts washer tank, etc.

In the ultrasonic, I use hot water and a bit of Dawn dish soap for most parts cleaning, works really really well on carb bodies. Often I soak parts overnight in Hydroseal (I have a couple of gallons in a covered bucket that I use over and over and over) before finishing them off in the ultrasonic tank, then for carb bodies, use a fine tip blow nozzle at 100 psi to be absolutely sure the carb passages are all clear.

the carbs from this Suzuki 750 project sat from 1989 to present with fuel in them, the slides were gummed solid, as were most of the passages, after my cleaning process they look like new inside and out, even the insides of the float bowls.

for all the rusty fasteners and bits on the Suzuki 750, including the heavily rusted rear shock springs, Evapo Rust is amazing stuff, just toss all the rusty bits in overnight, all the rust will have disapeared overnight, well worth hunting up a supply for yourself. http://www.evaporust.ca/ I have salvaged all the original rusty fasteners on the Suzuki 750, they all look like new now. Originality, plus saves on buying all new fasteners or replating.

Paul

 

[dueller]

Hi Dueller

for all the rusty fasteners and bits on the Suzuki 750, including the heavily rusted rear shock springs, Evapo Rust is amazing stuff, just toss all the rusty bits in overnight, all the rust will have disapeared overnight, well worth hunting up a supply for yourself. http://www.evaporust.ca/ I have salvaged all the original rusty fasteners on the Suzuki 750, they all look like new now. Originality, plus saves on buying all new fasteners or replating.

Paul

Yeah, I've heard of that stuff mentioned before. I've also seen a thread on here mentioning a hydrolysis process using a cathode and anode and water with some Borax in it and a 2amp battery charger.

 

[laverda1200]

so, bottom end of the engine, with pistons/barrels installed is back in the frame and I have turned my attention to the 16 valve head.

Man, those valves are tiny.

I have removed all the valve stem seals, and cleaned up all the valve stems/faces/comvbustion chamber.

BUT I have tried 8 of the 16 valves so far (4 intake, 4 exhaust) with the lapping paste, and not one, repeat not one, of the 8 valves so far is making full contact with the respective valve seats. Bizarre.

the only thing I can think of is that the valve guides can't be aligned correctly, as the valves themselves appear perfectly straight. From the combustion depositson the valve stems this engine has obviously been running like this for a long time before the cam chain broke, but the previous owner swears the head has never been done before, so I don't get it.

Thoughts, anyone? Suggestions? In the meantime, I am going to start hunting eBay for another head, but who knows whether another used head will be any better.......

local machine shops willing to replace valve guides and cut valves on a motorcycle head are few and far between around here, the quality is dubious, and the prices are ridiculous. Can anyone think of a way for me to resolve the head issue myself?

Paul

 

[Nessism]

Sounds strange about the valves. Bent? The service manual details how to measure valve run out with a V-block and dial indicator. Might be worth a check.

 

[gearhead13]

I have a 750 head here collecting dust, has all the cam caps and I think all of the valves if you are interested, pm me
I am in BC so shipping shouldnt be too bad.

 

[laverda1200]

pm sent

Paul

 

[laverda1200]

so, several bent valves, and some valve guide damage, presumably from the cam chain having broken back in 1989......

thanks to fellow Canadian and forum member Gearhead13 from whom I just purchased a used head and valves for a very reasonable price, so the engine rebuild is on hold while I wait for the Canada Post system to get the head to me, then I will clean up the "new" used head, lap in the valves, use all new valve guide seals, etc, before proceeding further.

Paul

 

[laverda1200]

the used head from Gearhead13 arrived to day, record time! Thanks Gearhead13.

I will go through this head this weekend, hope to have the 750 engine running sometime next week if al goes well!

Paul

 

[laverda1200]

well, the replacement cylinder head from Gearhead13 is all cleaned up, valves lapped in, new valve guide seals all installed, and all 32 of those tiny little collets are properly installed on the 16 tiny little valves..... what a job for these 57 year old eyes. I swapped over all the rocker arms (except for the one broken one) and three of the rocker arm rods from my original head (except for the bent one), and also installed the one used rocker arm rod and one used rocker arm I found from the local wrecker.

I have installed the cams in the head on the bench, and am going to set initial valve clearances with the head on the bench. I made a quick pair of fixtures to hold the head up off the bench far enough the valves can open and close while I turn the cams. Should get me close to correct tolerances and much easier for me than doing the initial valve clearance setup with the head on the engine.

Paul

 

[laverda1200]

is there a FAQ somewhere as to how to properly set up the valve clearances on teh 16 valve head with the screw adjustable valve rockers?

looks to me that after I slack off the locknut as far as possible I can then set the valve clearance with one of the two screw adjusters, lock that one down, then turn in teh second screw adjuster until it touches its valve stem, make sure it doesn't change the valve clearance, then lock it down? Or, is there some trick to get both screw adjusters even to make sure the pressure from the two valve stems is roughly equal on the rocker arm?

I was looking at the end of the screw adjusters, expecting to find a slot or something to use a screwdriver on like other similar engines, but found only something that looks like the end of a Robertson's screwdriver, really odd. Sorting through my screws and bolts odds and ends I found that a number 10 Robertson screw head seems to fit the rocker adjuster head fairly well, so I cut off the head of the Robertson screw and welded the head to a short length of metal rod I had laying around, seems to work OK on the rocker adjuster. I am assuming there is some sort of special tool for this purpose?

any help or suggestions appreciated.

Paul

 

[gearhead13]

Yes, there is a special tool, I got mine at Z1 enterprises:
http://www.z1enterprises.com/Tappet-Tool-Set--8mm-9mm-10mm-2870.aspx
Works quite well, except for a couple of the adjusters , I use a 9mm wrench on.

 

[Nessism]

I recommend using two feeler gauges at the same time and adjust the drag on the feelers so they are equal on both valves. The idea is to avoid any side loading on the cam follower causing it to twist.

 

[laverda1200]

Yes, there is a special tool, I got mine at Z1 enterprises:
http://www.z1enterprises.com/Tappet-Tool-Set--8mm-9mm-10mm-2870.aspx
Works quite well, except for a couple of the adjusters , I use a 9mm wrench on.

thanks both of you...

so I am not the only one who has a weird mix of 8 mm and 9 mm lock nuts on the various rocker arm adjusters, presumably.

I am doing the initial clearnce setting with the cams bolted in but the head still on the bench and rasied off the table surface a bit to allow the valves to open.

we have been having really spectacular weather here, odd for the fall, but it is nicer weatherwise than it has been most of the summer, so I have been mostly riding rather than wrenching, the Suzuki head can wait until the weather sucks again...

Paul

 

[gearhead13]

The 8mm nuts are off of a gsx(r) oil cooler I believe.
The weather is nice here too, but the bike is torn apart Its like torture, have to wait another week or two yet.

 

[laverda1200]

yeah, with the short Canadian riding season, being off the road for mechanical reasons during nice weather really sucks.

If you can manage it, a great reason to own more than one bike....... My ZX 14 is my main ride these days, bulletproof, change the oil and the tires regularly, that's about it, sucker is as reliable as a stone.

Paul