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Head Job on a 1980 GS750E (Part II: The Return of Carmine)

  • Thread starter Thread starter Carmine
  • Start date Start date
C

Carmine

Guest
Hello, I was on here a couple of years ago with a 1980 GS750E that was rescued as a derelict from a home in Novato. I trucked it down to Sunnyvale and started replacing the things that were broken.

Thanks to Tom MLC and Ken who visited me, and the advice of the rest of the forumites, I got it going. But first I got too busy, and then I moved to a place without a garage, and then I lost my job. Now I'm ready to go for phase 2 of the wrenching: The head job.

I asked my pal Dusty to check it out. He helped me out tremendously, cobbling together a new set of carbs out of two almost-working ones and making a custom rail to hold the throttle cable. We got it started. But it would run only until it got throttle then it would choke and die.

The #4 carb was filling up with gas because there wasn't a vacuum and the bike was trying to run on the other 3 cylinders.

He talked it over with some other mechanics and they said that the exhaust valves weren't sealing and it needed a valve job. Well I can't afford to have a pro do it, but I do have a lot of time.

I need to get some batteries into this camera, then I can take some pics for you guys. I got some cherry trim panels and gas tank in the original blue with pinstripes.

So what do I need to plan on doing? I have put more money into the bike than I could sell it for. I want to save it and ride it. Will I need to take out the engine?
 
I wouldn't start a valve job based upon talk and the fact that the bike isn't running correctly

What are your compression numbers?

When did you adjust the valve clearance?

Your symptoms sound more like air leaks on the intake side

1. Did you replace the carb O rings?
2. Re place O ring between head and intake boot?
3. Air box on? Sealed? Pods?

If you mean your #4 carb is overflowing, you have a stuck float, not a vacuum problem
 
Hi,

I concur with Mr. Big T. Start with the carbs. Go through the Carb Rebuild Series, making sure they are spotless and reassembled with new O-rings from http://cycleorings.com. Bench sync, adjust float heights and mixture screws as necessary. Adjust the valves as suggested. Then vacuum sync the carbs. Go through the Stator Papers to make sure your charging system is in order. At this moment there's no need to go tearing into the motor until all of the basics are done. Check out the mega-welcome for a bunch of tips and suggestions. Then check out my little BikeCliff website for some documentation. Keep us informed.

Thank you for your indulgence,

BassCliff
 
Never pull a motor apart based on speculation. A compression test will tell you if you have bad valves.

The previous posters gave you good advise.
 
FOR PHOTOS CLICK HERE:
http://picasaweb.google.com/supportguyjoe/GS75051909#

Compression numbers are 155-160-155-150, I tested them when Tom visited a couple years ago. I don't have my own tools yet

I have not done a valve clearance test. I'll work on that soon.

I gave Dusty the carb rebuild docs and the rebuild kits, and 2 sets of carbs from Ebay. We got it together and bench synched the carbs with calipers.

O ring between head and intake boot? No, not sure where that is? just have the rubber sleeves on the engine ports and then on the carbs.

Airbox is here but missing door. Right now pods are in. Dusty said he had to put jets one size bigger to account for the increased airflow. He tried restricting the flow through the cones by covering part of the mesh with duct tape.

I've had a crisis of faith since losing my job and I've been doubting I had any mechanical ability at all. I just realized I was trying to do it all on my own when I really need you guys.

Thanks again,
Carmine
 
Good compression numbers. You don't need a valve job.
Are you getting a good spark on #4?
 
Nothing wrong with those compression #s. You need to go back and either install the original airbox or get a jet kit to do it right. Just bumping the jet size up one size will NOT do it...
 
Well I have a Jardine 4-into-1 and those K&N pods installed, so I think I need to get a jet kit. I hear Dynojet stage 2 might be best. Maybe stage 3.
 
Compression numbers are great. Your bike does not have the intake o-rings. Why not try a factory jet kit? They are highly recommended by some. ;)
 
Love the photos Carmine :) Thats a very nice color. I have the same model myself which I recently bought. Hope you get her on the road soon :)
 
BassCliff said:
Hi,

I concur with Mr. Big T. Start with the carbs. Go through the Carb Rebuild Series, making sure they are spotless and reassembled with new O-rings from http://cycleorings.com. Bench sync, adjust float heights and mixture screws as necessary. Adjust the valves as suggested. Then vacuum sync the carbs. Go through the Stator Papers to make sure your charging system is in order. At this moment there's no need to go tearing into the motor until all of the basics are done. Check out the mega-welcome for a bunch of tips and suggestions. Then check out my little BikeCliff website for some documentation. Keep us informed.

Thank you for your indulgence,

BassCliff
Click to expand...

Thanks BassCliff -- I found out that my buddy was alright with the general carburetor knowledge, but he didn't touch the mixture screws behind the metal plugs. So I'm going to pop those plugs and turn the screws myself. At least that's the plan... I'll have a machine shop on speed dial so I don't get tempted to force one of those tiny screws. I'm using the K&N filter cones and a carburetor set that was tuned for another motorcycle and another airbox... so I'm going to give it the full Dynojet Stage 3 treatment, drilling out the ports and all.
 
While those carbs are off I strongly recommend a full carb tear down and changing the O-rings with a kit from cycleorings.com

BTW, where in CA are you? There are quite a few of us kicking about in various places in the state.
 
Nessism said:
While those carbs are off I strongly recommend a full carb tear down and changing the O-rings with a kit from cycleorings.com

BTW, where in CA are you? There are quite a few of us kicking about in various places in the state.
Click to expand...

Thanks -- I looked through the DynoJet parts kit and there weren't nearly enough O-rings. They did put it in a nice clear box and included 2 "Dynojet" stickers. Cause the stickers add 10 horsepower apiece :D

I'm in Mountain View, CA. I'd like to get on the GSers' Google Earth Map but Pulseman's message box is full
 
Carmine said:
Thanks -- I looked through the DynoJet parts kit and there weren't nearly enough O-rings. They did put it in a nice clear box and included 2 "Dynojet" stickers. Cause the stickers add 10 horsepower apiece :D

I'm in Mountain View, CA. I'd like to get on the GSers' Google Earth Map but Pulseman's message box is full
Click to expand...
Uhm. There should have been NO orings in the DJ kit that *I* recall. You need to replace the orings in your CARBS with a set from cycleorings.com
If you dont clean the carbs, you're just wasting your time.
 
TheCafeKid said:
Uhm. There should have been NO orings in the DJ kit that *I* recall. You need to replace the orings in your CARBS with a set from cycleorings.com
If you dont clean the carbs, you're just wasting your time.
Click to expand...

Quite right and I've placed the order to CycleORings.com tonight.
Looking in the box it seems what I thought were some O-rings were instead black metal E-clips.

This is the third and hopefully final attempt at rebuilding these carbs and I think I will wait till there are O-rings on my workbench before cracking them open yet again. If I have to stop in the middle it's going to make it that much harder to remember where I was when I start again.
 
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