GS1100L 4 valve rebuild vendors and thoughts on my investigation

[prichmon]

Over the past week I broke out my old 1980 GS1100L chain 4 valve to finally get it running right. I bought the bike and let it sit for 2-3 years in the garage as a nostalgia purchase. My 1st bike was a 1979 gs1000l.

Mods:
dyna S ignition system with NGK plug wires and plugs.
Cams say R1 on them so I assume they are early Gixxer/gsxf.
V/Hines megaphone with silencer no packing.

It had a nagging stutter when rolling on the throttle until it built enough rpm to be on the main. The bike seemed to also backfire when I slowly raised the the rpm a little to 2000-2500.

I cleaned the carbs with a new ultrasonic cleaner. I started adding fuel at idle and by raising the needle. Symptoms got better but didn't go away. The bike started, idled and revved much better.
I decided to pull compression: 150, 90, 100, 125. I added oil to 2,3 = 125, 150
My theory for the lower compression on 2,3 was maybe they had open valves over the 2-3 year period and the bike needs ran to reseat the rings.

Next i pulled the valve cover to check for any tight valves for a compression leak. All the valve were real loose 5-10 thousands gap while the engine was still pretty warm. I'll set the proper valve lash tomorrow.

I checked the timing. timing was ~5* advanced when I put it to stock it seemed to run worse. So I put it back.

I could see the crank walking in and out when I revved at the timing cover area. I checked runout spec which is .004". I don't think I would notice that amount.

Am I correct in assuming the backfiring is from the low compression on cylinder 2,3?
I don't know how the bike is supposed to sound or run with the different cams? Should it have a higher idle, compression and/or timing?
If there is corrosion in the cylinders I need to ride it too clean it up and retest. Otherwise the engine is just plain wore out and it needs at least the op end rebuilt.
If the crank walk is as bad as I saw the crank needs rebuilt too which means a complete engine rebuild.
Is it possible the thrust bearing is the only failure in the bottom?

Best case:
rebuilt head
rings
gaskets
rebuilt crank
GS750 2 valve oil pump gears

Could someone give their thoughts on my observations?
What are the costs to rebuild a 16 valve head and crank?
Gaskets, rings and the small bits are available from several sellers. Who sells the crank bearings and such? Suzuki only? Are the GS Sages going to Motion or other bearing houses to get bearings?

Are there any knowledgeable GS engine people in the in the columbus or cinci Ohio area?

Thanks

RR

[fastbysuzuki]

There’s a lot going on there, I am not familiar with the 1100 as for the cams you are assuming they are not standard ( someone that has a 1100 may or not verify) the compression difference is beyond the usual limits they may get better with use ( only time will tell) if you can see the crank floating then it’s likely more than 004”
have you taken note of the jet sizes to see if they are standard or not?
Is the bike fitted with pods or standard air box?
you really need some sort of base line before changing anything.
As for gaskets I would only use Suzuki head and base and try to keep away from Athenia ( just my personal choice)

[GregT]

The crank is located sideways by one ball bearing which is at one end. Memory says ignition side but I could be wrong. Last one I replaced was bought over the counter from a local bearing supplier. It's an engine out and split job to replace it.

[prichmon]

There’s a lot going on there, I am not familiar with the 1100 as for the cams you are assuming they are not standard ( someone that has a 1100 may or not verify) the compression difference is beyond the usual limits they may get better with use ( only time will tell) if you can see the crank floating then it’s likely more than 004”
have you taken note of the jet sizes to see if they are standard or not?
Is the bike fitted with pods or standard air box?
you really need some sort of base line before changing anything.
As for gaskets I would only use Suzuki head and base and try to keep away from Athenia ( just my personal choice)

I've seen several 2 valve cams but only a few 4 valve sets. The last 4 valves were ~15 years ago. These cams are not the typical egg shape.

The bike has UNI pod filters with a jet kit. I will have to open the carbs back up to look at the jet #s. I know they aren't stock. I believe it is a 6 sigma kit.

Gaskets I've used cruizinimage, vezrah and suzuki when I've been able to get them. Suzuki is my 1st choice. When working on my gs450 they weren't available in the states.

Thanks for the replies guys!

RR

[Nessism]

The running problems are likely related to the jetting.

I wouldn't worry about the compression until you ride the bike a bunch more. Perform an Italian Tuneup!

If those are actually aftermarket cams, then they may well run more lash than stock.

[prichmon]

The cams have r1 on both and measure about 34.4mm top to bottom of lobe. I believe they are later gsxr or gsxf cams.... maybe not.???

Could you define an " Italian tuneup"?

On the further inspection i dont think the crank is the actual the problem. I checked the timing crank end tonight. The movement looks like play between the magnet dyna s rotor and the retaining bolt. I'm going to contact dyna to find out how much play is recommended.

I'm going to pack the megaphone silencer to save what's left of my hearing.

I'm going to buy fresh plugs to get a clean read. When I pulled them 2 was pretty black and 3 was wet. I've since adjusted float levels and made sure the needle valves were sealing by doing bench testing

thanks all!!!

RR

[Nessism]

https://en.wikipedia.org/wiki/Italian_tuneup

And for the sake of motorcyclists everywhere, put a real muffler on your bike. There is nothing worse than an some knucklehead running a mufflerless bike, annoying everyone within a mile, and generating hate for ALL bikers, even those with stock pipes.

[prichmon]

Found out what an Italian tuneup is.

Thanks!!!