81 GS1100 E Starting Problems

[steves]

I have a 1981 GS1100 E. Carbs have been torn apart and cleaned. When cold, the bike won't start. You can sit and spin the starter, and nothing happens.

If I shoot some gas into the airbox, it fires right up.

Fuel screws are 2 turns out.

Anybody have any ideas? I'm thinking I may just shove the bike into the corner of my shed until spring time if I can't figure this out soon...

[49er]

Check that your chokes are operating correctly. If they are, then you may be due for a top end rebuild.
What mileage has the bike done? Does the engine idle evenly and pull ok through the revs? If not check the valve clearances. After that, do a compression check, when the engine is hot and with the throttle wide open. Compression should be in the range of 128-175psi. Anything around 100psi is too low.

[Dave8338]

Once you get it started, does it continue to stay running? Have you checked the choke circuit to make sure all is well there? Petcock been tested and flows well? How long has the bike been sitting?

[steves]

Check that your chokes are operating correctly. If they are, then you may be due for a top end rebuild.
What mileage has the bike done? Does the engine idle evenly and pull ok through the revs? If not check the valve clearances. After that, do a compression check, when the engine is hot and with the throttle wide open. Compression should be in the range of 128-175psi. Anything around 100psi is too low.

I need to investigate doing the valve clearances, a friends dad has been doing some of the work for me and I just brought the bike back Friday.

I did rebuild the petcock, however it isn't flowing fuel on prime, but does flow correctly on vacuum. Used an alternative fuel source to remove the petcock from the bike.

[steves]

Also, the odo has about 30k on it, but I'm not sure if that's accurate or not.

It sat for about 15 years until I found it in a garage.

[KEITH KRAUSE]

I'll assume the carbs are clean and no possible intake leaks. All the basic tuning needs to be correct. Compression, valves, spark/timing, fuel/air flow verified, mixture screws set for highest rpm, etc.
As part of any carb cleaning/rebuild, the throttle plates must be bench synched as close as possible in preparation for the vacuum synch. Have you synched?

[chef1366]

You need to prime the bowls by using the Prime on the petcock.

Edit: Went back and read the opening of your post DOH
It runs after you get it started with a shot of gas. For more than a few minutes?
If no read above post. If yes I'd agree that your choke rods (jets) are clogged. Thay are the brass tubes that go into your float bowl.

[Road_Clam]

I have a 1981 GS1100 E. Carbs have been torn apart and cleaned. When cold, the bike won't start. You can sit and spin the starter, and nothing happens.

If I shoot some gas into the airbox, it fires right up.

Fuel screws are 2 turns out.

Anybody have any ideas? I'm thinking I may just shove the bike into the corner of my shed until spring time if I can't figure this out soon...

Your choke passage ways are clogged with debris. You need a major carb cleaning.

[steves]

I just checked with my friends dad, he said that he adjusted the valve clearances to within spec, and had every part of the carb disassembled that he could find.

Yes, the carbs were vac-synched with a Morgan Cabtune.

The bike runs reasonably once it's started. It's just getting it to turn over cold that's the problem.

[chef1366]

The choke circuit is clogged.

[steves]

Whelp I'll check the choke again I guess....

[bwringer]

I'm thinking I may just shove the bike into the corner of my shed until spring time if I can't figure this out soon...

Nooooooo! That's how motorcycles die...

Hey, has anyone mentioned the choke circuit? :razz:



Seriously, if you do decide to set it aside for a while, put Sta-Bil in the gas and drain the float bowls so the carbs don't gum up any worse.

[steves]

Well, currently the bowls are dry, and I'll drain the tank if it comes to it. This isn't my first project bike, last winter I rebuilt a '96 katana for my girlfriend. Nothing about this one seems to make sense. We replaced the rectifier (being the only thing we could tell was really wrong with the bike) first, and the more it's been out on the road, the better it seems to feel.

I just can't justify putting new rubber on the bike if I can't be certain it's going to run.....

I really really really doubt that it's the choke circuit. The guy who was working on it for me supplements his retirement income nicely with a word of mouth business restoring old BMWs. He may not be an expert on the old 'zukis but he knows a thing or two.

For a minute pretend that the choke circuit is clean as could be... what would the next step be? I can't guarantee that it's clean, but I know that he replaced some rubber, and at least two of the jets....

What else would cause the bike to only start with fuel in the airbox?

[49er]

Low compression, blocked idle jets, or could there be a gremlin in there somewhere?

[txironhead]

This may be out in left field, but it happened to a friend of mine...could the choke cable be broken or need adjustment? Can you verify that the choke is fully engaging when you pull the knob? My friend's bike wouldn't start in the cold and we worked on it for a while before I noticed that when he pulled the choke the slide barely moved. A $15 cable and he was back on the road.

It's the small things that give us the most trouble.....