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Cold weather tuning

  • Thread starter Thread starter Anonymous
  • Start date Start date
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Anonymous

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I have just done a thorough cleanup of my 77 GS750, and rebuilt the carbs. I am trying to get them perfectly set for idle and synced now.

My real question is, at 30-40 degrees out (it's a heat wave compared to what it has been), am I just going to have to retweak everything in late spring early summer when it will be 80-90 out?

I got so tired of trying to get it perfect today, that I think I am just going to go with Earlfor's settings and leave it at that:

Pilot: 1 turn out
Air: 1 3/8 turn out
vacuum: about 23" at 2000rpm

This thing has been killing me because the plugs are sooty but I'm getting backfiring through the carbs (lean). I'm hoping the backfiring is not due to valve clearance since I have not been able to really find a valve cover gasket, and what's there now doesn't leak. It wil be my luck that the clearances will be fine but I will forever have an oil leak.
 
Do you have the air box installed??? It would run lean and back fire if you don't have it installed
 
Most bikes tend to run considerably leaner in those kind of temps, compared to 70-90 degrees. I would just try to get it to run half way decent, and worry about fine tuning it when the weather hits a reaonable temperature. (at least 65-70) I have my pilot mixture screws out 2 turns on my 850, and it still seems a tad lean.
 
"Fine tuning" on a GS? First time I've heard of it or thought about it in 17 years of GS ownership.

I take my GK to my mechanic every year in November or early December. He checks the valves and the carbs. If necessary, he balances the carbs and replaces shims. Then I ride the bike all year long after that, averaging about 12,000 miles a year, without a single thought of "fine tuning" for cold weather, hot weather, wet weather, dry weather, etc. I just ride it without a worry, and it always performs perfectly.

This past November he didn't replace a single shim, and the carbs were only slightly out of balance. The GK has 64,000 miles.

If a GS bike is tuned correctly, right from the start, it will run correctly for miles and miles.

I'm lucky to have a knowledgeable, responsible independent mechanic nearby to service the bike on the couple of things I'd rather not do.

Nick
 
Re: Cold weather tuning

MY 750, with those carb settings runs the plugs a medium brown (which is right where I want them) Sooty usually indicates rich and backfiring normally indicates lean. Considering the weather in NY, are the plugs sooting with the bike running in the garage at idle on choke, or is that reading taken at speed on the highway?
We're both at aproximately sea level, so I dont think its probable those settings are too rich. I would go with the backfiring condition and assume a lean condition first, Usually, you can identify which cylinder is backfiring. Most likely thing to cause that is a faulty induction boot "O" ring. Did you already replace the boot "O" rings? After that, I would consider lowering the vacum reading when synchronizing the carbs. (less velocity will draw less fuel and consequently, the engine will run leaner)

Earl



cherryc said:
I have just done a thorough cleanup of my 77 GS750, and rebuilt the carbs. I am trying to get them perfectly set for idle and synced now.

My real question is, at 30-40 degrees out (it's a heat wave compared to what it has been), am I just going to have to retweak everything in late spring early summer when it will be 80-90 out?

I got so tired of trying to get it perfect today, that I think I am just going to go with Earlfor's settings and leave it at that:

Pilot: 1 turn out
Air: 1 3/8 turn out
vacuum: about 23" at 2000rpm

This thing has been killing me because the plugs are sooty but I'm getting backfiring through the carbs (lean). I'm hoping the backfiring is not due to valve clearance since I have not been able to really find a valve cover gasket, and what's there now doesn't leak. It wil be my luck that the clearances will be fine but I will forever have an oil leak.
Click to expand...
 
Re: Cold weather tuning

Okay guys, thanks for the suggestions. The main problem was that I had tried to adjust the fuel screws with the carbs in place and that was a mistake. My hands were just not meant to fit into spaces like that.

On Sunday I removed the carbs and readjusted the fuel screws correctly. I think that one I had four or five turns out 8O (my big fingers "thought" that the screw was seated when it was still a few turns out). I had to go to 1 3/4 turns out on the mixture screw, but now it idles well and runs like a scalded dog. What more could I ask n :lol:
 
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