90Bansheedude Posted June 7, 2009 Report Share Posted June 7, 2009 Im ordering some parts, and want to get a few jets also, so I need some quick recommendations. (im sorry, i know everybody must be tired of jetting questions!) What would be a good number to start at when breaking in the new top end? I hate guessing on jetting while breaking in a new top end, for fear of melting my new pistons. What do you guys do for a situation like this? Guess high and then break in awhile and then to plug test? I bought the bike with blown top end (hole in one piston, front edgemelted on the other. It has stock carbs with 280s installed. My Elevation is 1600-1700, bike is Ported, K&N filter, Bills Pipes, Reeds (not sure on brand, but has large bottom reeds with 2 on top of those per side), timing (+4 maybe?, someone said to start at 0, jet, then adjust timing?), compression im not sure about (supposedly a milled head, but i dont know about that until i get my stuff and get it back together), gonna probably run 91 octane if possible, and 32:1 mix and B8ES plugs, also I may run the airbox lid because of riding around water, but the bottom of the 2 tubes in it has been cut out. Temp will be around 85 in Nebraska. What would be a safe starting number! Thanks guys! Brian =) We should start up a thread were everyone posts there mods, elevation and jetting, and sticky it, to help give people something to browse for starting points! I think it would help alot for questions like mine. If it sounds like a good idea, let me know and Ill do it! If you need a picture of the porting, i can get it. It doesn't look too massively hollowed out to me. Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted June 7, 2009 Report Share Posted June 7, 2009 (edited) Im ordering some parts, and want to get a few jets also, so I need some quick recommendations. (im sorry, i know everybody must be tired of jetting questions!) What would be a good number to start at when breaking in the new top end? I hate guessing on jetting while breaking in a new top end, for fear of melting my new pistons. What do you guys do for a situation like this? Guess high and then break in awhile and then to plug test? I bought the bike with blown top end (hole in one piston, front edgemelted on the other. It has stock carbs with 280s installed. My Elevation is 1600-1700, bike is Ported, K&N filter, Bills Pipes, Reeds (not sure on brand, but has large bottom reeds with 2 on top of those per side), timing (+4 maybe?, someone said to start at 0, jet, then adjust timing?), compression im not sure about (supposedly a milled head, but i dont know about that until i get my stuff and get it back together), gonna probably run 91 octane if possible, and 32:1 mix and B8ES plugs, also I may run the airbox lid because of riding around water, but the bottom of the 2 tubes in it has been cut out. Temp will be around 85 in Nebraska. What would be a safe starting number! Thanks guys! Brian =) We should start up a thread were everyone posts there mods, elevation and jetting, and sticky it, to help give people something to browse for starting points! I think it would help alot for questions like mine. If it sounds like a good idea, let me know and Ill do it! If you need a picture of the porting, i can get it. It doesn't look too massively hollowed out to me. i personally would start out rich @ 330-350 mains, until you can check the plug color and know exactly what the motor wants. i would also run the needles in the middle position and 27.5 pilots and air screws around 1-1/2 turns out. i would suggest finding out the comp ratio and timing advance if any, so you know exactly what octane of fuel to be running. also, there is a topic on peoples jetting in the jetting forum. the topic is called "what is everybody running for main jets?" here is the link to that topic... http://www.bansheehq.com/forums/index.php?showtopic=99361 Edited June 7, 2009 by mopar1rules Quote Link to comment Share on other sites More sharing options...
90Bansheedude Posted June 7, 2009 Author Report Share Posted June 7, 2009 i personally would start out rich @ 330-350 mains, until you can check the plug color and know exactly what the motor wants. i would also run the needles in the middle position and 27.5 pilots and air screws around 1-1/2 turns out. i would suggest finding out the comp ratio and timing advance if any, so you know exactly what octane of fuel to be running. also, there is a topic on peoples jetting in the jetting forum. the topic is called "what is everybody running for main jets?" here is the link to that topic... http://www.bansheehq.com/forums/index.php?showtopic=99361 Awesome! Great help, mopar. I appreciate it. How can you test the compression ratio? Or is knowing the compression PSI enough? I will set the timing at +4 because of what people are saying on the forum of it being a good safe number. Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted June 8, 2009 Report Share Posted June 8, 2009 you can find out the cranking PSI w/a compression gauge. IMO, its not the most accurate thing to go off of for fuel octane determinants. you need to know the total cylinder volume, w/the piston @ BDC. this will include cylinder volume in cc's + head volume + head gasket volume, if using a stock head gasket. then you take that total amount of cc volume and divide it by the trapped volume @ TDC. to find the volume @ TDC accurately, you need to use a burret and then fill the cylinder up (w/piston @ TDC) and see how many ml's/cc's of kerosene are needed to fill up to the top of the spark plug hole. subract 1.8cc for the volume of the spark plug hole and you have your trapped volume. then once you divide out the total cylinder volume by the trapped volume, you will have your comp ratio. from the comp ratio, you can then determine the octane of fuel to run. you can even use a corrected comp ratio, as that is the most useful comp ratio to go off of, as compression doesn't start until the exhaust port closes. for now, i guess, just put a comp gauge on it and just see what it pulls for cranking PSI. Quote Link to comment Share on other sites More sharing options...
90Bansheedude Posted June 8, 2009 Author Report Share Posted June 8, 2009 you can find out the cranking PSI w/a compression gauge. IMO, its not the most accurate thing to go off of for fuel octane determinants. you need to know the total cylinder volume, w/the piston @ BDC. this will include cylinder volume in cc's + head volume + head gasket volume, if using a stock head gasket. then you take that total amount of cc volume and divide it by the trapped volume @ TDC. to find the volume @ TDC accurately, you need to use a burret and then fill the cylinder up (w/piston @ TDC) and see how many ml's/cc's of kerosene are needed to fill up to the top of the spark plug hole. subract 1.8cc for the volume of the spark plug hole and you have your trapped volume. then once you divide out the total cylinder volume by the trapped volume, you will have your comp ratio. from the comp ratio, you can then determine the octane of fuel to run. you can even use a corrected comp ratio, as that is the most useful comp ratio to go off of, as compression doesn't start until the exhaust port closes. for now, i guess, just put a comp gauge on it and just see what it pulls for cranking PSI. LOL....Yeah, i think ill start with the compression gauge. Oh and by the way, the pilots are already a 30. With the 280s that are in it, i was thinking order 2 each of 300, 320, and 340 to try and get dialed in, then later order an in between if needed. Quote Link to comment Share on other sites More sharing options...
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