New member 1979 GS1000: introduction, pics, and leaky cylinders!

[ecirmo]

Hello new friends!

I am the proud new owner of this orange beauty. It was not running when I got it last September, and over the past few months I have found this forum to be extremely helpful in getting it running. I spent a fair amount of time lurking the forum, checking the new member resources (Paul Musser's vm carb rebuild manual was a true gift), BikeCliff.com, the stator papers, etc.

Here's what it looks like:


Here's what I've done:

• Carb rebuild and cleaning, all new o-rings and gaskets, but all other parts original
• Intake boot o-rings
• Dyna S ignition
• Dyna coils
• Dyna wires
• Spark plugs
• Brake pads
• Caliper rebuild (front and back)
• Front brake light switch fixed
• Speedo/tach lights
• Valve gap check (all passed)
• Valve cover gasket
• Battery
• Gas, oil, brake fluid

...and it runs great! Charges the battery well, and no electrical issues. One of the most fulfilling experiences I've had.

And now, on to my main point: compression and the potential need for a top end rebuild
Today I had a compression check done, which revealed cylinder 1 to reach 150 psi and hold steady, while cylinders 2, 3, and 4 reached from 100-120psi, but lost pressure in just a few seconds. We didn't have the right compressor fitting to use the leak down tester, but I am thinking that it might be time to plan a top-end rebuild (rings, valve cleaning(?), cylinder honing, other crap). Observations:

• The piston heads are pretty nasty.
• Lots of carbon on the new plugs. Running rich for sure, leaned it out today (mikuni smoothbore carbs, reduced the fuel screws to 1 turn out and reset the air screws to high idle, to the best of my ability. Very difficult to see an rpm difference in cylinders 2 and 3)

Question is, can I do this without taking the whole motor out? Because of work space, removing the whole motor would be difficult for me to manage, even with help. I'm a reasonably mechanically adept person, but this is definitely beyond anything I've done before. Am I better off paying a professional?

I'm a pragmatist, and don't expect it to run like it did when it came from the factory, nor do I care about it looking like it has never seen the road...the patina is nice and I love it. I'm mainly concerned about doing this properly, because this bike is very special to me and deserves to not just be working, but working in top form (or close).

I would very much appreciate your perspective and advice on getting this engine cleaned and rebuilt (or doing it myself).

Cheers
(will gladly post more pics as requested)

 

[Guest]

Those are crappy compression numbers for sure. I'm surprised you said the bike runs great with numbers like that. As for rebuilding the top end, for sure you can do it with the engine in the bike, and the best person to do this work is yourself. If you've done all the listed work yourself a top end rebuild will be no harder. Make sure you have the shop manual, you'll need someone that can hone the cylinders for you (unless you buy a hone and do it yourself). Make sure you buy all OEM suzuki gaskets, too many of the aftermarket ones leak. Are you sure that compression test was done properly? great looking bike by the way, all kinds of cool go fast parts of the day. What do you have in the 29mm smoothbores for main jets and pilot jets? what do you have for an airbox setup? I've got a 78' 1000 with the 29mm smoothbores, goes like a bat out of hell

 

[ecirmo]

Thanks! That is great news to hear. The airbox is stock, by the way. And the listed work was indeed done by me, with the aid of this forum, manuals, and general tinkering. The period-correct mods were one of the things that attracted me to it. The foam grips, rear sets, 4 into 1, and oil cooler I think really suit it.


Regarding it running great, it turns right over and runs very reliably for long distances. I really just had no basis for comparison, i.e. I don't know what the bike would feel like with bad compression vs good compression. I'm pretty sure we did the compression test right, but it certainly is worth running again with different equipment to verify our results.

Thanks for the tips. Honing is in the plan, and thankfully I know some experienced folks willing to work for beer. Any favorite tips for doing rings and cleaning the piston heads? I've never gone this far into an engine before and it's uncharted territory for me. I'm a bit worried about cocking up the cam chain and getting the pistons cleaned and the rings fitted within tight tolerances. Will the require special measuring equipment?

 

[steve murdoch]

The tech archives on this site are fantastic, indeed.
Looks like a Rickman half-fairing. It suits the era.

 

[tkent02]

If the bike sat for a long time and if it hasn't been ridden at least several thousand miles, give it a chance. A lot of times the compression will come out better and better the more you ride it. I have bought a lot of dead bikes that have sat for years, they mostly do this. Do the maintenance and ride them, they will get better. If I had your compression numbers and it ran OK I'd just ride it a few months and see how it does. If the pistons are covered with carbon tune the carbs better and ride the heck out of it, they will come clean.

Unless you just like taking things apart, then go for it.

 

[dorkburger]

Cool looking bike. Welcome and good luck with it.

 

[ecirmo]

Are there any opinions out there regarding OEM Suzuki parts (head/base gaskets, valve seals, rings) vs the parts on dynoman.com? While not oem, he describes the parts he has listed there as potentially better than stock. Multi-layer steel gaskets and pure viton seals and whatnot.

Edit:
gaskets --- http://dynomanperformance.com/engine/gaskets-cometic.html#gs1000
valve seals --- http://dynomanperformance.com/engine/cam-followers.html#gs1000

 

[Guest]

You have a link for dynoman.com? I typed that into my browser and it said "the domain may be for sale" and offered optional sites.

 

[GSXR7ED]

Welcome,

That's quite the write up for an intro thread. You've genuinely utilized the resources provided--good job.

You've got plans and plenty of people here will have lots of feedback...

Ed

 

[Nessism]

Running rich for sure, leaned it out today (mikuni smoothbore carbs, reduced the fuel screws to 1 turn out and reset the air screws to high idle, to the best of my ability.

Smoothbore VM carbs don't use a fuel screw. You sure those carbs are smoothbores, or are they stock VM Mikuni's?

Regardless of above, I'd ride the bike until you see some significant running symptoms of problems. Poor idle, burning oil, something. As Tom says the compression may come up. How many miles on the engine anyway?

 

[Big T]

I see that a carb sync is missing from your list

The leak down numbers indicate stuck rings, as mentioned above. Give Buck a buzz and see how long it was sitting

I don't think you have smoothbore carbs. I looked it over outside The One and I should remember that detail.

Run it hard and see what happens. How's the oil consumption?

The Cometic gaskets are good, Vesrah not so much

 

[ecirmo]

I see that a carb sync is missing from your list

The leak down numbers indicate stuck rings, as mentioned above. Give Buck a buzz and see how long it was sitting

I don't think you have smoothbore carbs. I looked it over outside The One and I should remember that detail.

Run it hard and see what happens. How's the oil consumption?

The Cometic gaskets are good, Vesrah not so much

53k on the clock, and a carb sync was done by bridge city cycles back in November. Bike was sitting about two years before Buck got it. Oil consumption is moderate I'd say and there is a very slow leak from one spot in the oil pan, I add a splash every couple weeks if I'm riding a lot. Glad to hear about the gaskets, Cometic base and head on the way.

I've been riding it hard and often and for long distances, a little over 3000 miles since I got in running last October. Would it take longer than that to start seeing compression improvement? I think I'm going to do a rebuild regardless, because it seems like compression is being lost somewhere along the line, and if something in there needs attention, I may as well dive in and install new rings, get the valves all cleaned up and seated nicely, replace gaskets, and in general get everything cleaned and spruced up. It'll be nice to know it's all been replaced, plus it sounds like a fun learning experience.

The carb id has been an enigma for me. When I started tearing them down, I was under the impression that they were the Mikuni VM26SS, which is also what the 79 and 80 GS1000 service manual lists. The o-ring set I used from cycleorings.com was for the vm26, and everything fit perfectly. Then I started googling pictures of the vm26, and they didn't really match what I had.

The main difference was that my carbs don't have a choke lever on the side, but a cable that goes up to below the instrument cluster. Also, the idle adjustment screw is underneath the bowls instead of on top. Most pictures I can find of the vm26 show it at the top.

Regardless, here's what I have:

Sorry the pic isn't more zoomed in.

 

[Big T]

Those are the VM 26

The ones you found pictures of are for the 750/850, which has the idle screw on top. The choke lever was on the side thru 78, in 79 all of the bikes had the choke up top

I would think 3,000 would be enough miles

Have you put anything in the cylinders to free up the rings? Marvel Mystery Oil is a favorite here

You're in SW, right? Maybe we should get together and take a look at it

 

[ecirmo]

Yep, I'm just down the hill from OHSU. It'd be great to get together and have you take a look.

And no, haven't put anything in the cylinders yet.

 

[Big T]

I'm in S Beaverton

I don't think the weather will cooperate this weekend

Keep in touch

 

[ecirmo]

New Development: got the thing torn apart and started cleaning the cylinder head domes, and noticed what appeared to be some significant wear:


Is this salvageable? I'm was going to take the head and valves in to be lapped, but if this head is shot than it's not worth it. Thoughts?

 

[Nessism]

Can't tell from that photo.

How about taking some more photos and uploading them on photobucket? Then if you link the

 

[Big T]

Ed, I believe this is classic "nobody ever adjusted these valves for 20,000 miles" result
Ethan, you might try lapping that one and see whether there's a good seat under there. More pics of the valves and head, please

 

[tkent02]

Ed, I believe this is classic "nobody ever adjusted these valves for 20,000 miles" result

If that was the case the valve would be burnt. What do the valves look like?

 

[ecirmo]

I'll work on the photobucket thing. In the meantime, here are a few more of the domes and the worst valves:

https://drive.google.com/open?id=0B-IMdmfv0aPjcFlZdW5sQ1hCelE
https://drive.google.com/open?id=0B-IMdmfv0aPjT25hOVlHQWI4dGc
https://drive.google.com/open?id=0B-IMdmfv0aPjZmFzN3c5Z0Y2U3M
https://drive.google.com/open?id=0B-IMdmfv0aPjeFRUWlQwQ3VFRGc
https://drive.google.com/open?id=0B-IMdmfv0aPjNU5vRjdSVlNndVk
https://drive.google.com/open?id=0B-IMdmfv0aPjeVRfcG5fZkpfSUU

These aren't cleaned up yet, but they definitely are pitted and gouged/scored in various places in thee seal area around the domes. In some cases the edge of the dome appears rounded off a bit.

Everything else has looked great so far. The pistons are quite good, only superficial carbon on the face, all rings free and very little carbon on the sides. The cylinder walls look like mirrors. Sigh, should I start trolling ebay for a new cylinder head?