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Throttle slide needle position

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

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Ive read other messages on similar topics and Im not sure what position to adjust the slide needles to.

Ive got a 4-1 glass pack muff and ramflow (seperate cone filters) but other than that this engine is stock as a rock.

can anyone please give me a pointer on the slide needle position as there is 5 possible settings.

Also does this richen or lean the mixture of will i possibly have to rejet?

thanks peoples.

Rita
 
and I suppose it might help if I tell you its a 1978 GS750 LoL
 
Try 116 main jets, put the needle clip 1 or maybe 2 positions below the middle one, try 1 position lower first, you may also want to richen up the idle mixture.
 
I would try 2 positions richer on the needles. Lowering the needle's e-clip raises the needle. This richens the mixture.
I would try adjusting the pilot screws (underneath) out 1/2 turn more than where they were when stock. Adjust the side air screws for the highest rpm possible and re-set idle with the idle screwknob. If the pilot circuit is still lean, try putting the pilot screws back to original setting and increase the pilot jet one size up (2.5). Go up about 4 FULL sizes from what was stock on the mains.
Remove the 2 float bowl vent lines for better bowl venting.
Re- synch the carbs and get the levels as close as possible. (within 1 cm of each other)
 
How does it run now? You richen the mixture by 1) turning the screws on the side of the carb in, 2) turning the screws on the bottom of the carb out, 3) moving the clip on the needle down and 4) going up in size on the main jet. If you change any of these things you are rejetting. Lowell (lol)
 
hi guys, thanks for the replys.


Don,
After a recent long run I came home and shut the engine down at nearly full throttle, and coasted to my house, the plugs were a dry, powdery black colour. Im running on unleaded 96 ron.

the exhaust has a noticable dry black colour on the rear of the muff as well.


It is only doing 10.6 Km per litre (rotten), floats are set correctly, not leaking, air filters are clean, engine is in reasonable condition (160-165Psi even on all 4 cyls), valves set correctly.

There is a noticable flatspot at top revs (after about 7000 in 5th gear on the highway) like it runs dry of fuel, it is also jerky on the off idle throttle (cables adjusted nicely and free moving) is this to do with something called synchronisation?

Sorry, im new to servicing and have my brother helping me since he has been on bikes for 15(ish) years.

He just said the mainjet is 127.5, does this sound right?

another q: how hard is it to change the "needle" height in the butterfly slider?
How do I do this> and can it be done on bike or do I need to remove the carbs?

Thanks again for all your help, its great to have such a dedicated forum!

Rita
 
Also forgot to add that on deceleration at normal opperating temps, the exhaust lets off loud pops.

I have been told that it is a standard sign of overfueling (also shown by the consumption)

Rita
 
OK. First of all, I assumed (my fault) that your carbs jets were probably stock and you were running lean with the mod's you have.
According to your last plug read after nearly full throttle, your mains are too big. Try 120's. Without a needle circuit plug read (1/2 throttle) I can't say where to put the needle clip, but if it has stock needles, I would try the 4th position down or possibly the 4th position with a jetting spacer on top the e-clip. It's generally safer/better to jet too rich and work your way back, so I would try the 4th position without the spacer first.
If the pilot screws have possibly been moved ever, try setting them all about 1 1/2 turns out. When seating them, do it LIGHTLY. Set the side air screws like I said earlier. Then you MUST synch the carbs.
Decel' popping can be an exhaust leak or a lean condition (pilot circuit).
I have to go to work now, but if you still need help later I'll try to help tonight if I can.
Let me know.
 
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