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Jet Suggestions?

  • Thread starter Thread starter pasteurized
  • Start date Start date
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pasteurized

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Finally looks like have a line on a set of correct carbs for my bike (1977 GS750). I have ordered a new set of o-rings from Robert Barr (thanks RB). I bought a carb dip can today and s few extra cans of carb cleaner so once I get the carbs in hands I am going to tear them all apart and clean them thoroughly. My question is what jet changes should I make while everything is apart? I also have some new o-rings for the intake tubes on the way.

As is sits, the bike will have:

Pod filters (EMGO)
Completely gutted (straight thru) mufflers
All else stock

I know the mains stock are 102.5. I have a set of 110s and 115s so I can swap those in once I get the carbs and get them cleaned up. Which would you recommend? Also, should I look into changing idle circuit jets while I am in there? I just want to be able to clean up the carbs, install recommended jets and be able to mount the carbs and not have to take them off 800 times. I have a carbtune brand new in the box and ready to sync the setup once it is all set. Any other suggestions to keep in mind when I dive into this project?

Thanks!
 
My advice (for what its worth) is to set everything up as close to stock as possible and follow the excellent carb teardown and cleaning procedure detailed on this site. This will give you a good starting point and you may even find everything is right first time. If the carbs are really clean and the floats set up right, you should be able to get the motor running - the rest is down to balancing and fine tuning.
I definitely would not mess with the jets until you know they need replacing - and the best way to find out is by running it on the bike with fresh plugs.
 
Thanks for the input. I do know the jets need replacement though because the bike has always run lean above 4K rpm and with the mods it has stock jets will definately not be enough. I was hoping someone out there with a similar setup would be able to shed some light on what sized main jets I should use. Also, many have said that cold starting problems have been helped by upping the idle jets one size due to them being very lean from the factory. Can anyone confirm this? I would like to try to do these jet changes while everything is apart.

-Brad
 
Been having a bitch of a time getting my pods and pipe running right. I got no advice for ya except stick with a stock airbox and pipe! Sorry, maybe I'll have better news after the Dyno tuner gets finished.
 
Damn Jethro, that's not what I want to hear! ;-)

Honestly, if I had known the consequences I wouldn't have let my buddy rip the exhaust innards out of the mufflers because before that it was running pretty well! I still have the stock airbox but I also have the pod filters so if I am going to take the time to tune everything I might as well do it with gutted exhaust and the pods.
 
115 would be a good starting point,the needle will have to be raised try one notch if you have adjustable needles, if not go to an electronics store & buy tiny washers to fit under the circlip.
Ttry around a 3mm lift at first,this is the easy bit you don't even have to remove the carb's for needle adjustment,just take the top's off.
OK now it's down to plug chop's,checking plug colour at diff rev's.
Given the choice aim for slightly rich rather than lean, petrol is cheaper than a new motor
Any prob's just ask
 
As you seem to have been lean around 4k (needle range)maybe raise it 4-5 mm .
 
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