SpeedRacer88 Posted August 8, 2011 Author Report Share Posted August 8, 2011 I agree with the +4 to start, then work your way up. Mine was put on the dyno and ran best at +7 and we went all the way to +11. Did you open the motor up or did someone else? I am just wondering what was going on in there to blow it. hole in the left piston both spark plugs ghost white i opened it myself it got to be jetting right? i mean i dropped almost 4000 feet in altitude. i should have known to check it but i was to busy showing off to all my old high school buddies Quote Link to comment Share on other sites More sharing options...
SpeedRacer88 Posted August 8, 2011 Author Report Share Posted August 8, 2011 Hard to believe that a rm250 is kicking your ass is it all worked up? he said its ported and piped phathead high compression head(cool head) and a modded timing plate Quote Link to comment Share on other sites More sharing options...
beebs Posted August 8, 2011 Report Share Posted August 8, 2011 Did you have fresh fuel in when it blew? Quote Link to comment Share on other sites More sharing options...
SpeedRacer88 Posted August 8, 2011 Author Report Share Posted August 8, 2011 yes it was completely empty when i started it we all got our fuel from the same spot Quote Link to comment Share on other sites More sharing options...
SpeedRacer88 Posted August 8, 2011 Author Report Share Posted August 8, 2011 what is the general rule for jetting when dropping elevation? i dont want to pay for jetting but it looks like i will have to because i dont wanna mess it up again Quote Link to comment Share on other sites More sharing options...
SpeedRacer88 Posted August 8, 2011 Author Report Share Posted August 8, 2011 Anyone? Quote Link to comment Share on other sites More sharing options...
beebs Posted August 8, 2011 Report Share Posted August 8, 2011 If you go to the Exhaust and Jetting Forum, on the second page you will see "421 Cub jetting" there is good info there along with many other's in that area. Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted August 8, 2011 Report Share Posted August 8, 2011 I told you exactly what jetting to run in the first post I made. That's not a guess. That's what you need to run. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted August 8, 2011 Report Share Posted August 8, 2011 General rule of thumb I've used is 1-2 main sizes richer for every 1000 feet you go down in elevation. That being said...if you put a hole in a piston and both plugs were white, you had signs before it melted down that you missed. Quote Link to comment Share on other sites More sharing options...
SpeedRacer88 Posted August 8, 2011 Author Report Share Posted August 8, 2011 I told you exactly what jetting to run in the first post I made. That's not a guess. That's what you need to run. i understand that and i really appreciate the help seriously i do but im already richer than that.... and its jetted for higher elevation and it ran perfect. im 100% sure it was way too lean once i got to sea level i can show you pics if needed i decided to take it to the shop for jetting anyway... but on another note is there anything i can do for a lilttle more edge before i do? Quote Link to comment Share on other sites More sharing options...
SpeedRacer88 Posted August 8, 2011 Author Report Share Posted August 8, 2011 General rule of thumb I've used is 1-2 main sizes richer for every 1000 feet you go down in elevation. That being said...if you put a hole in a piston and both plugs were white, you had signs before it melted down that you missed. your right there were plenty of signs but me being the competitive dumbass i am all i could here was "take that slow shit off the trailer" i been kicking myself for the last 2 days Quote Link to comment Share on other sites More sharing options...
dajogejr Posted August 8, 2011 Report Share Posted August 8, 2011 Ok...let's go another route. What is your cranking compression AND your UCCR for that motor. 17 cc domes might be ok for 4000 foot...they won't last long at sea level. Air leak or wrong domes if you gave it that much fuel and it still melted down. Quote Link to comment Share on other sites More sharing options...
SpeedRacer88 Posted August 8, 2011 Author Report Share Posted August 8, 2011 I had 24 cc pump gas domes but got 165 psi domes for Avgas now idk the rest it's play ported by hjr the timing was at 3 but I ws gonna bump it Quote Link to comment Share on other sites More sharing options...
dajogejr Posted August 8, 2011 Report Share Posted August 8, 2011 You should be able to run 20cc domes cut properly and run AV gas...but to be honest, I'm not a fan of it. I'd rather run all race fuel or pump gas. Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted August 8, 2011 Report Share Posted August 8, 2011 I agree with dajogejr.. If you were that high up, jetted that rich and still blew it up, then you had another issue. The jetting specs I gave you are what needs to be in your bike. You just need to make sure you get your issues worked out. Quote Link to comment Share on other sites More sharing options...
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