air/fuel screw?
- Thread starter mattstang
- Start date
the screw adjusts the amount of air added to the pilot jet circut, turning it in reduces that amount, and turning it out adds more air
on a stock carb, there is rarely any need to change the pilot jet, the stock 32.5 is all that carb can flow at or just off ilde
and the airscrew should be under 2 turns out, to give it the highest idle and rev cleanly
if your under 1 turn out you prolly have a cloged pilot , fuel flow problem,
over 2 turns out = possible air leak, dirty filter
on a stock carb, there is rarely any need to change the pilot jet, the stock 32.5 is all that carb can flow at or just off ilde
and the airscrew should be under 2 turns out, to give it the highest idle and rev cleanly
if your under 1 turn out you prolly have a cloged pilot , fuel flow problem,
over 2 turns out = possible air leak, dirty filter
i just put a new filter in and took the airbox lid off i have the stock piolet and a 310 main mild port and polish , lrd pipe, vf3, and running 100 LL FUEL and it is slugish of the bottom , pulls extreamly hard threw the mid and on the top it seems to slug out alittle especially around 5th and 6ix gear on the top end it kindof fall on its face but threw out the whole power band it dosent bog or hicup or stutter like if it was to rich and when i i went from the 300 to the 310 i didnt feel a differance in the top end but the bottom end it seem to slug more i really havent messed with the air/fuel screw yet so wich way do yo guys think it should be turned
you'll just need to play with it, set your idle slightly higher than you normally run, then start turnin the airscrew till you it idles the highest, then stab the throttle quickly, if it revs cleanly, thats the best setting to start, take note as to how many turns out that is, under 2 or even 2 1/2 is fine, but more than likely you'll be closer to 1 turn out, then take a small screwdriver riding with you, and try 1/8 turns one way, then the other, it will tell you where it likes that airscrew set at
Good news and bad news...
The LRD pipe will leave you feeling a little sluggish down low. The right bend pipes are for top end which means they neglect the bottom end somewhat.
The good news is, you have some carb knowledge here to help... the first step is understand how the air screw works.
The pilot jet pulls fuel past the slide (mainly during high vacuum times like when the engine is idling and when the engine is slowing down off of high RPM). The air needle acts on the vacuum applied to the circuit which is supplied fuel by that jet by bleeding fresh air over top of it past the slide.
The farther "out" the needle is, the less vacuum is applied to pilot jet and the less fuel is drawn through that jet. The farther "in" the needle is, the more fuel is drawn through the jet.
The air or pilot needle is only effective during heavy deceleration (letting the engine brake the quad) and idle periods when the vacuum is high and the fuel consumption is low.
There is a fine tutorial in the "engine" section under the sticky "most useful posts: everything you need to know about blaster engines" which explains the tuning of the air needle. I will recap that procedure just for giggles...
You get a close enough pilot jet installed that the engine will idle first off.
Start the quad and warm it up (a few good laps around the yard is sufficient).
Accelerate the idle to just above a normal idle or "fast idle".
Adjust the air screw until you achieve the highest possible idle speed (reducing the set point on the idle screw as needed to keep the engine at a fast idle).
You then judge the size of the pilot jet by the number of turns the air needle is out from a light seat. If the needle is less than 1 turn out from a light seat, the pilot jet is too small (too much vacuum needed to draw fuel through too small an orifice)
If the air screw is more than 2.5 turns from a light seat then the pilot jet is too large...
The LRD pipe will leave you feeling a little sluggish down low. The right bend pipes are for top end which means they neglect the bottom end somewhat.
The good news is, you have some carb knowledge here to help... the first step is understand how the air screw works.
The pilot jet pulls fuel past the slide (mainly during high vacuum times like when the engine is idling and when the engine is slowing down off of high RPM). The air needle acts on the vacuum applied to the circuit which is supplied fuel by that jet by bleeding fresh air over top of it past the slide.
The farther "out" the needle is, the less vacuum is applied to pilot jet and the less fuel is drawn through that jet. The farther "in" the needle is, the more fuel is drawn through the jet.
The air or pilot needle is only effective during heavy deceleration (letting the engine brake the quad) and idle periods when the vacuum is high and the fuel consumption is low.
There is a fine tutorial in the "engine" section under the sticky "most useful posts: everything you need to know about blaster engines" which explains the tuning of the air needle. I will recap that procedure just for giggles...
You get a close enough pilot jet installed that the engine will idle first off.
Start the quad and warm it up (a few good laps around the yard is sufficient).
Accelerate the idle to just above a normal idle or "fast idle".
Adjust the air screw until you achieve the highest possible idle speed (reducing the set point on the idle screw as needed to keep the engine at a fast idle).
You then judge the size of the pilot jet by the number of turns the air needle is out from a light seat. If the needle is less than 1 turn out from a light seat, the pilot jet is too small (too much vacuum needed to draw fuel through too small an orifice)
If the air screw is more than 2.5 turns from a light seat then the pilot jet is too large...
thats what i was thinking with the lrd being slugish of the botom when i first got the pipe i put it on all stock blaster and jetted the main to a 280 the top end was fine and the bottom was slugish then i read that artical on the pipe shot out where they ran a 290 main and endedup droping the piolet to a30 so i tryed just putting the 30 in with my 280 and it riped threw out the whole power band i got alot more testing to do in the morning but im shure ill figure it out i always do
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