1979 GS750 Blowing Blue smoke

[ehkmcveh]

Anybody know a good place to get parts in Canada for my 79
Tried motorcyclecanada...not much selection...

[ehkmcveh]

Is there a proper way to clean these. I have dremel bits that can get the job done but not really sure. The instruction video I seen didn't show here cleaning it at all. I took all the carbon deposits of the piston so might as well do the valves also. They seem to be seating alright

[Steve]

About your "low" compression numbers, I have a couple of questions.

1. Did you adjust the valves before doing a compression check? If not, you might have a couple valves that have clearances tight enough to leak just enough to give you lower readings.

2. How long has it been since the bike has been run regularly? I don't mean fired up to verify it's running, I mean ridden a couple hundred miles a week, minimum. If the bike has not been run regularly, the rings might be stuck, the cylinder walls might be just a bit rusty, and a few other small details that plague an engine that has not been run.

Good thing you also have an oil leak to justify changing the gaskets. I would hate to see low compression numbers after your gasket change, then watch them improve after a few hundred miles of exuberant use.

.

[ehkmcveh]

1. No compression was done first before anything. The valves will be lapped once I can get my crank case leak figured.
2. Just took it on a 250 mile ride, but before that barely rode it all year. Maybe like 2000 miles last year. Symptoms started happening after the 250 mile ride. Crank case oil leak was already there (but got worse). Started blowing blue smoke. And mileage went in the toilet.

They don't look took rusty, but after a Honning should clean that up. Got bigger problems right now (crank case leak!)

[ehkmcveh]

Have this stubborn head gasket that won't fully come off. Picture attachedIMG_7664.jpg
Is this good enough to seal?!? Just small bit of green gasket that have turned to concrete.
Have hit it with a number of things, gasket remover chemical but won't seem to budge.

Got the pistons and new rings in and want to seat the cylinder head. I do not have the specialty tool to pinch the rings... anyone have any DIY tips to sit the cylinder head

[JTGS850GL]

That's the base gasket. Not the head gasket. Hard to tell how high those spots are, but I'd still try to remove them as best as possible. You can use a wood chisel to get the high spots. There is no pressure inside that gasket so it's not like it has to hold back cylinder pressure like the head gasket does. Only use a Suzuki OEM gasket for the base and the head gasket. The only other head gasket I would trust is a Cometic gasket. Stay clear of cheap aftermarket sets.

[ehkmcveh]

yeah base gasket, oops. I have a Suzuki gasket waiting to go on. the spots are pretty level though. I will try and go at it some more but they are just concrete!

[ehkmcveh]

Got the cylinder mounted but ran into some difficulty installing tappet.
attached shows a lip on the inside wall where the tappet slides into. It occurred from me trying to re-align it to get it in.IMG_7674.jpg
Is there a way to smooth this out. I have some 220 grit sandpaper but wasn't sure if I can take that to aluminum.

I had the tappet in all the way but it did not move easily like the others, almost seized. I managed to get it out.

[ehkmcveh]

Doing some more reading, tappet = Shim bucket, I was reading someone suggest using 600-1000 grit sandpaper but no reply saying success or not. I have the valve springs out right now. Anyone run into this?

[ehkmcveh]

Alright.... compression question. Did some reading on the forum but still need a little clarification on my specific situation.

Just finished got the rebuild back together and having 50-70 psi readings on all 4 cylinders. Tested with the carbs off (full throttle). Once the pressure gets to the max you can basically see the gauge start dropping slowly.

During rebuild, lapped al valves with fine compound. Cleaned them up. Tappet clearances within 0.03 to 0.08mm after shim changes
Timing was done according to the service manual. T-1.4... 1 arrow flush with cylinder head, pointing forward. from 2 arrow count 20 pins to the 3rd arrow. Then put idler assembly and cam chain tensioner back on.

All piston rings were replaced and oriented as shown in the service manual.

The head gasket was NOT changed. It appeared to be made of sturdy material and I cleaned the surfaces with scotch bright. I realize that gasket is compressed and then de-compressed (during rebuild) that it loses some integrity.

The engine has not been run yet. Have read that these readings are not to be worried about until you run the bike a bit ?!?
Just wondering if you should get strong reading right after the rebuild (not ran yet), or do you have to wait a bit for it to "seal up"

Alright guys, rip into me on what I did wrong

[ehkmcveh]

Started the bike yesterday... Was doing more reading and said taking comporession test off fresh rebuild is useless until a few miles are on it.
Now start working on the carbs.... bike is doing about 20MPG

[boris.h]

yep, you need to make the rings sit and get married with the cylinders shape. that's not the case before doing some km.

No blue smoke anymore? Did you measure the valves wooble?

I had a similar issue after an engine rebuild and had to disassemble / assemble the engine some times. the engine had only fex km (less than 50). I re-used the same head gasket without any issue few times, 4, 5 times. After few hundred km, its integrity started to going over. Had to buy a new one.

About my oil leak (and making blue smoke) issue on the 4rth cylinder, even if the rings were new, even if all the seals were new, the oil leak came from the only part I did not changed: valves guides.... 0.15mm radial play for the intake valve, 0.35mm radial play for the exhaust valve.....

[ehkmcveh]

yep, you need to make the rings sit and get married with the cylinders shape. that's not the case before doing some km.

No blue smoke anymore? Did you measure the valves wooble?

I had a similar issue after an engine rebuild and had to disassemble / assemble the engine some times. the engine had only fex km (less than 50). I re-used the same head gasket without any issue few times, 4, 5 times. After few hundred km, its integrity started to going over. Had to buy a new one.

About my oil leak (and making blue smoke) issue on the 4rth cylinder, even if the rings were new, even if all the seals were new, the oil leak came from the only part I did not changed: valves guides.... 0.15mm radial play for the intake valve, 0.35mm radial play for the exhaust valve.....

Yup no more blue smoke. Think I have a small leak on my oil pan (since I went it to take a look). I believe its dripping on my exhaust pipe, so when the bike engine begins to get hot it appears that the head is smoking ! Need to investigate a little more.

Have a new gasket on the oil pan so prob just need to drop it and clean the metal surfaces (scotch bright) a little better

[ehkmcveh]

Just tapped a piece of paper to the base of the bike, to capture where the oil leak is coming from the bike.... it doesn't look that bad so its not the oil pan causing the smoking.
Just had the bike started up, when it got warm it appears the smoke is coming out of the head gasket. Not really sure what that means... it doesn't smell like exhaust... almost plastic like?

I hope there is not engine damage occurring

[ehkmcveh]

Here is a ruff video of the smoke at lower speeds.