jordi Posted March 21, 2010 Report Share Posted March 21, 2010 (edited) 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, 2010 by jordi Quote Link to comment Share on other sites More sharing options...
gasgasmi Posted March 22, 2010 Report Share Posted March 22, 2010 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. Quote Link to comment Share on other sites More sharing options...
laser1 Posted March 22, 2010 Report Share Posted March 22, 2010 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? Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted March 22, 2010 Report Share Posted March 22, 2010 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? Quote Link to comment Share on other sites More sharing options...
max1956bikes Posted March 22, 2010 Report Share Posted March 22, 2010 a smaller pilot jet will mean a cleaner bottom end instant pull .the pilot screw only really affects tick over revs. Quote Link to comment Share on other sites More sharing options...
chewy Posted March 22, 2010 Report Share Posted March 22, 2010 Is ther something to "switch off " the pilot jet/airway after tickover? Quote Link to comment Share on other sites More sharing options...
laser1 Posted March 22, 2010 Report Share Posted March 22, 2010 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 Quote Link to comment Share on other sites More sharing options...
lineaway Posted March 22, 2010 Report Share Posted March 22, 2010 To Chewy, The pilot jet is always feeding fuel. Quote Link to comment Share on other sites More sharing options...
max1956bikes Posted March 22, 2010 Report Share Posted March 22, 2010 easy way to turn of pilot jet.turn of fuel.but engine wont run very well Quote Link to comment Share on other sites More sharing options...
bigfoot Posted March 22, 2010 Report Share Posted March 22, 2010 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. Quote Link to comment Share on other sites More sharing options...
gasgasmi Posted March 23, 2010 Report Share Posted March 23, 2010 (edited) 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, 2010 by GasGasMi Quote Link to comment Share on other sites More sharing options...
laser1 Posted March 23, 2010 Report Share Posted March 23, 2010 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. Quote Link to comment Share on other sites More sharing options...
jordi Posted March 23, 2010 Author Report Share Posted March 23, 2010 Ok, little bit more info. Have been running a 33, but the air srcew has to be 3 & 1/2 turns out. Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted March 23, 2010 Report Share Posted March 23, 2010 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? Quote Link to comment Share on other sites More sharing options...
jordi Posted March 23, 2010 Author Report Share Posted March 23, 2010 Quote Link to comment Share on other sites More sharing options...
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