Hi guys, just a quick question, what difference would dropping from a 35 pilot jet to a 30 make?

its a 250 by the way. Idle thoughts really,but would be interested in your thoughts.

Cheers.

Edited March 21, 201016 yr by jordi

I find that a richer pilot works better. My wife has a new 250 and I put a 38 pilot and a 114 main in it, seems to be really good. Every Gasser I've had in recent years seems to be better after I put in a richer pilot and lean out the main just a bit. I am assuming you have a Pro.

depends on the carb. The PHBL will run like a very smooth 200 off the bottom with a real lean pilot. The power is very muted - you can here it as well. IMO, the PHBL has a very inefficient pilot ciruit and needs a rich setting. That said- they are about as simple and trouble free as they get. I find I can run a very lean (in comparison) pilot in the VHST and not lose power while still smoothing out the very bottom.

Wheres your fuel screw (turns out) now?

Don't take any notice of what is said if its in the us their fuel is alot different.

Shercos came with 36 way back and they went better with 33 on the dellorto. Think my 250 in o7 had a 34?

a smaller pilot jet will mean a cleaner bottom end instant pull .the pilot screw only really affects tick over revs.

Is ther something to "switch off " the pilot jet/airway after tickover?

Nigel is right - different gas will effect the jetting -as will air temp and pressure, oil ratio's, engine condition, over oiling air filters ... ect... Thats why its important to understand the way to properly set them up and also to just experiment and try it for yourself. The avg sea level bike in the USA uses a 38 pilot, the UK seems to go 34 -35 range. 30 is probably too lean even with UK gas, but easy enough to try. You may love it. FWIW: The pilot jet and fuel screw effect both the pilot and progression circuit and has a major effect on power to 1/8 turn throttle openings and tapers off till 1/4 turn. The progression circuit also effects the mixture with throttle chops (engine can go too lean if not rich enough fuel screw setting is used) You CAN use the fuel screw setting as a rough gauge for pilot jet sizing. Too far out - needs a bigger pilot. To far in, need a smaller.

Here some good bathroom reading.

http://www.thisoldtractor.com/gtbender/mg_...a_guide_1.1.pdf

http://www.thisoldtractor.com/gtbender/mg_...orto_manual.pdf

To Chewy, The pilot jet is always feeding fuel.

easy way to turn of pilot jet.turn of fuel.but engine wont run very well

Nigel is right - different gas will effect the jetting -as will air temp and pressure, oil ratio's, engine condition, over oiling air filters ... ect... Thats why its important to understand the way to properly set them up and also to just experiment and try it for yourself. The avg sea level bike in the USA uses a 38 pilot, the UK seems to go 34 -35 range. 30 is probably too lean even with UK gas, but easy enough to try. You may love it. FWIW: The pilot jet and fuel screw effect both the pilot and progression circuit and has a major effect on power to 1/8 turn throttle openings and tapers off till 1/4 turn. The progression circuit also effects the mixture with throttle chops (engine can go too lean if not rich enough fuel screw setting is used) You CAN use the fuel screw setting as a rough gauge for pilot jet sizing. Too far out - needs a bigger pilot. To far in, need a smaller.

Here some good bathroom reading.

http://www.thisoldtractor.com/gtbender/mg_...a_guide_1.1.pdf

http://www.thisoldtractor.com/gtbender/mg_...orto_manual.pdf

Just what I've been looking for for many years now. Cheers. This should get pinned somewhere.

I didn't look at your location. There has to be a difference in the fuel or something, that's why I feel the need to rejet all the Euro bikes to make em run good for me here. I am in the USA at about 1100ft above sea level.

Edited March 23, 201016 yr by GasGasMi

I didn't look at your location. There has to be a difference in the fuel or something, that's why I feel the need to rejet all the Euro bikes to make em run good for me here. I am in the USA at about 1100ft above sea level.

Yah - we have to do the same. For years, I thought they just jetted them rich for "break in", but found out there are big differences in the fuel - including the price. Evidentally the stock jetting is good to go over there.

Ok, little bit more info. Have been running a 33, but the air srcew has to be 3 & 1/2 turns out.

Ok, little bit more info. Have been running a 33, but the air srcew has to be 3 & 1/2 turns out.

Try a 30?