Why won't my '82 GS650 start, and how do I fix it?

[duaneage]

I read somewhere that bikes sold at altitude were re-jetted for the area. It might also need new main jets.

[Decker]

I'm back!

It's been a long time, but I am keeping my promise to get back to y'all about my GS650 and its issues with starting. Since I didn't have a garage or tools, the process really took this long.

Short version: The pilot knobs needed some adjustment, but the more major problem was that the carbs had never been thoroughly cleaned. After three months of sitting, and it had some rough starting before that, the choke had gummed entirely open, the other valves opened only with difficulty, and the jets were full of black slime.

My '81 CB900 Custom had the exact same issue: gummed open, stuck choke, jets full of crud.

I went through three cans of carb/choke cleaner, and about 9 hours of effort, but they're both running strongly. I have peripheral issues now, such as the front calipers not releasing and the rear turn signal being broken off, but those are less baffling than this was.

[Decker]

Oh, one more thing...

During this process, I had the "pleasure" of disassembling, cleaning, and reinstalling two sets of Fours.

When I first noticed my dad-in-law's opposed twin BMW, I thought it looked goofy. After pulling and reinstalling Fours on the CB900, I had a healthy respect for the accessibility of the twins. After doing the Fours on the GS650, I hope that the creator of the Fours is burning in hell.

[Big T]

During this process, I had the "pleasure" of disassembling, cleaning, and reinstalling two sets of Fours.

When I first noticed my dad-in-law's opposed twin BMW, I thought it looked goofy. After pulling and reinstalling Fours on the CB900, I had a healthy respect for the accessibility of the twins. After doing the Fours on the GS650, I hope that the creator of the Fours is burning in hell.

That's only because you've never worked on V-4!

[Steve]

That's only because you've never worked on V-4!

And it doesn't make any difference which way the V-4 is turned, either. I have had the dubious pleasure of working on my sister's Honda ST1300 (cylinders to the sides, crank in-line) and my son's Yamaha Venture Royale (transverse crank, cylinders fore-and-aft). Both are rather difficult to handle.

* last time you've adjusted the valves
... I don't exactly understand what those valves do, but I'll read up on it.

"Those valves" are the ones in the cylinder head that let the gas/air mixture into the engine, then let it out the exhaust pipes. Clearance is pitifully small to start with, and diminishes with wear to infinitessimal. Tight valves can lead to hard starting, then other problems including burned valves, which are not fun or cheap to replace.

A closely related question ... I intend to make runs between Denver (5300ft) and the west coast (0 - 1500ft) during the summer. Given the fairly rapid altitude changes (3000 foot drop in 3 days) how should I prepare for mixture changes?

For example, would rejetting for either high or low be a mistake when I went to the other place? Should I carry a screwdriver and expect to stop once each direction to adjust screws?

No need to make any changes on the road. It appears that most of your time might be at the lower elevation, so jet for there. When you go up, your mixture will richen up, and richer is safer than lean. Besides, the jets you would need to change for the most benefit would require removal and disassembly of the carb rack. Not something you would want to do on the road, let alone on a regular basis.

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