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Carburetor Pilot air Screw Adjustment
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Carburetor Pilot air Screw Adjustment
Haynes manual at page 81 writes for Pilot air Screw Adjustment:
With the engine in working temperature ,
1. Set the Pilot air Screw to it's standard position 1 5/8 turns out.
2. Set the idle speed to 1700 +-100 rpm ,( i do not know how to do this),
and what is the lowest reliable idle speed?
3. Then turn the pilot 1/4 turn in or out until the most even idling is obtained.
On my bike, the cold-to-hot engine rpm are different, if I lower idle when the engine is hot when it's cold it goes out.
I must try to have a smooth idle or idle with the highest rpm?
How do you set up the mix?
Or it would be better to visit a workshop for exhaust gas control?
With the engine in working temperature ,
1. Set the Pilot air Screw to it's standard position 1 5/8 turns out.
2. Set the idle speed to 1700 +-100 rpm ,( i do not know how to do this),
and what is the lowest reliable idle speed?
3. Then turn the pilot 1/4 turn in or out until the most even idling is obtained.
On my bike, the cold-to-hot engine rpm are different, if I lower idle when the engine is hot when it's cold it goes out.
I must try to have a smooth idle or idle with the highest rpm?
How do you set up the mix?
Or it would be better to visit a workshop for exhaust gas control?
Duckrider- Posts : 253
Join date : 2014-06-08
Age : 64
Location : Athens
Re: Carburetor Pilot air Screw Adjustment
Best to ignore the 1700 rpm, just get engine to working temp, then set to a fast idle speed and then adjust the mixture screw to give the best tick over, then adjust throttle stop screw to give the normal idle speed. No need for visit a workshop for exhaust gas control
JohnW- Posts : 1383
Join date : 2011-10-29
Re: Carburetor Pilot air Screw Adjustment
And what did you mean saying : <<to give the best tick over>> ?
And saying << set to a fast idle speed >> how fast? Because after a few turns of the throttle stop screw
the rear wheal starts to run.
When I set my Honda Transalp XL650V2 carburetors, I set the pilot screw in the standard three turns out.
Then I screwed until the rpm started to fall, and I noticed the position of the screw.
Then I unscrew the pilot screw until the rpm start again to fall and I notice the turns of the screw again.
The right position was in the middle of the turns I had noted.
Is it possible to do the same here?
Duckrider- Posts : 253
Join date : 2014-06-08
Age : 64
Location : Athens
Re: Carburetor Pilot air Screw Adjustment
Yes fast idle speed then then procedure you say. The back wheel should not turn if its its out of gear. This adjustment should not be made with it in gear.
JohnW- Posts : 1383
Join date : 2011-10-29
Re: Carburetor Pilot air Screw Adjustment
I must say that I did not have a pilot screw number 12.5 but 15, I bought it from Yamaha and is the screw that was placed on the models T80 from 1983 to 1986.
After 1986 both models T50 and T80 have 12.5.
My carb is a VM14SH from T50 witn main jet 85 , the same jet as T80 has at the VM16SH.
So, I tried to make some adjustments.
I first raised the idle from its screw, ι turned the screw about half a turn screwing.
Then I screwed the pilot screw completely, while careful not to over-tighten and destroy it.
When I screwed it in completely the engine turned out.
I unscrewed the screw two full turns and then screwing and unscrewing slowly and carefully, measuring the turns I noticed that from the 1 1/2 turns to the 2 turns idling rose significantly, so I left it in the middle, now is about 1 3/4 turns.
I will use it for some time and after i will give a look at sparkplug.
After 1986 both models T50 and T80 have 12.5.
My carb is a VM14SH from T50 witn main jet 85 , the same jet as T80 has at the VM16SH.
So, I tried to make some adjustments.
I first raised the idle from its screw, ι turned the screw about half a turn screwing.
Then I screwed the pilot screw completely, while careful not to over-tighten and destroy it.
When I screwed it in completely the engine turned out.
I unscrewed the screw two full turns and then screwing and unscrewing slowly and carefully, measuring the turns I noticed that from the 1 1/2 turns to the 2 turns idling rose significantly, so I left it in the middle, now is about 1 3/4 turns.
I will use it for some time and after i will give a look at sparkplug.
Duckrider- Posts : 253
Join date : 2014-06-08
Age : 64
Location : Athens
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