500ft question

EricMichael

EricMichael

New member
Joined
Dec 25, 2005
Messages
543
Location
Presque Isle, ME
hey i have a question, i'm running slp's and last year I ran 153.5's on the grass for 500ft I believe the needle is at 3.5 position. I noticed it ran alittle rich still..can't remember the temps...but would it be safe to go with 150's just for 500ft? I dont want to go out there start it up and have it seize up..not sure if this is cutting hte fuel back to much or not..any help would be great. thanks
 
JUST RUN GOOD FUEL AND WATCH PLUGS. I,LL SAY YOU BE FINE AT 150,s. MY SRX IS WAY , WAY UNDER THAT FOR 500 F.T. ON GRASS. 3:16 (yammie tony)
 
Your way hugely fat on jetting. drop mains to about 145,s, lower needlesat least 1/2 but you might need fatter pilots.
 
thanks guys..soon as the season starts rolling around in good shape i'll try the 145 mains with 48.5 pilots see how she likes it ..has 47.5 pilots right now anyway so thanks for the help again
 
whoa, those are some big pilot jets

150 pilots??? LOL, I think Turk means 50......................... just a typo, unless you have a 1/4" drill bit to open them up....LOL!!!!

I would let the piston wash guide you as you go down in your jetting, it is hard to burn them down in 500ft, but not very hard at 501ft!! so be carefull, lean is mean in short runs. With your 47.5 you may be fine at 2 turns out on fuel screws with leaner mains. Your just gonna have to try it because its all dependant upon your clutching/suspension set up, how hard you load the engine.
 
this is prob a dumb question..sounds like it but checking your piston wash..wouldn't you have to tear the head off to check..seems kinda hard to look down the plug hole. lol ?
 
shortstop20 said:
If you buy a bore light or a "snake light" as they're sometimes called you can see the wash without taking the head off.
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these are a VERY good investment. that or the fiber-optic ones. will save you ALOT of time.
 
If you can,t find one I have one for $20 shipped. Haven,t used it since i went 4 smoke.
 
Leaner is not always better or faster. We have dynoed our SRX and found that it likes a little more fuel than normal to make the most power. We later applied this to the field and picked up some time and MPH. Not all motors like to run lean. Good Luck!
 
LB Racing said:
Leaner is not always better or faster. We have dynoed our SRX and found that it likes a little more fuel than normal to make the most power. We later applied this to the field and picked up some time and MPH. Not all motors like to run lean. Good Luck!
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yeah i'll just have to set some timers up and spend a week or so playing with it. I have found the viper to be crisper and quicker with leaner jets in the winter. I think the srx's like more fuel anyway but i'm not sure..I believe the viper motor produces more power with leaner jets..but again I haven't messed with jetting too much..took me all last fall to get clutching figured out lol well thanks for input
 
your fuel-power curve is gonna be largely dependant on your fuel atomization. pretty complex thing to test without a laboratory, but as a general rule of thumb, the bigger the carbs, the worse the atomization, but better flow. Higher intake charge velocities (like on the stock 33mm carbs) will need less fuel 'cause they'll atomize better and be able to use the fuel that they have more efficiently.
 
another issue to consider is the temperature of the motor, a warmed motor will need less fuel to make the same jam 'cause the warmer crankcase air/metal will 'cause better evaporation/atomization. if the motor is warmed up hot you might get away with running it leaner. but usually the yamaha's run better cold, that's my experience anyways, warm pipes and cold motor for the best runs.
 
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