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hard starting GS750E

  • Thread starter Thread starter robpreston
  • Start date Start date
R

robpreston

Guest
my 1980 GS750E is a real pain to get started.
It seems that it starts on only 1 or maybe 2 cylinders, then after a few seconds, the others kick in.
Don't know if something is blocking fuel flow somewhere, or if there is a different problem causing this.
It also runs ok on the pilot jets, but falls flat till it gets to about 3300 rpm then takes off like a rocket.
Any suggestions.
It has a 4to1 header, and pod filters running 142 main jets.
Thanks
Rob
 
Hard starting is quite often caused by mis-adjusted valves, especially if they are tight.

How long has it been since they were adjusted?

Since you also seem to be having carburetion problems, might as well TOTALLY clean (dip) them and treat them to some new o-rings as well.

.
 
robpreston said:
my 1980 GS750E is a real pain to get started.
It seems that it starts on only 1 or maybe 2 cylinders, then after a few seconds, the others kick in.
Don't know if something is blocking fuel flow somewhere, or if there is a different problem causing this.
It also runs ok on the pilot jets, but falls flat till it gets to about 3300 rpm then takes off like a rocket.
Any suggestions.
It has a 4to1 header, and pod filters running 142 main jets.
Thanks
Rob
Click to expand...

Those are WAYYYYYYY to big mains! Good lord man.

First of all, you need a DynoJet kit to run pods on CV carbs. The only reason it's running now is because you're shoving so mch gas down its throat. The mains are so big the needle isn't even a factor. Buy a kit. The bike will run much better, especially after you adjust the valves and clean the carbs.
 
main jets

main jets

The stock jets are supposed to be 112.5 on this bike.
When I got it, would barely start at all.
Took the carbs apart cleaned everything, and started changing jets a few steps at a time until it seemed to run ok. The final step was at 142.
Didn't go any higher. When looking at the plugs after running the bike, they aren't dark at all as if it were running rich.
If it wouldn't run well with smaller jets, I assumed we were on the right track with the 142s.
Where should I start.
Thanks
 
Your needle won't adjust, so you need the Dyna jet kit, if only for the needle. The reason you are good on pilot and then taking off later is because your mid-throttle jetting is knackered.

With your jetting all over the place, checking the plugs after riding will tell you nothing. You are probably lean at mid throttle and rich at WOT. By the time you stop riding, any rich signs picked up at WOT might burn off.

Get that needle changed, do some plug chops, and work it out from there.

Good luck.
 
While the jet kit recommended above should clearly help with the upper RPM range, it may not have much effect on the starting issue. For that:

When were the carbs rebuilt? Are the pilot jets clear? Are the starter jet tubes in the float bowls clear? Are the pockets and fuel passage in the float bowl for the starter jet tubes clear?

For a very good guide to CV carb tuning see this website: http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html
 
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