crsracing Posted August 21, 2011 Report Share Posted August 21, 2011 Ok guys here it is , im new to the site and couldnt find anything on this topic and need some help . I bought a banshee that was run on 50/50 av gas . And i want to switch it back to pump gas just because its alot more practical for me to use pump gas . Av gas is hard to get where i live . So lets start with whats done to the bike . It has 4 mil crank with cub cylinders , cool head (not sure of dome size ) 35 mm carbs dune port and polish and +9 advantaced timing ( i think) . Like i said i bought the bike already done so not real sure about some things but was all done right beautiful bike hauls ass lol. Anyways my questions is how do i convert it back to pump gas ???? I was told change the domes to like 20cc and set timing back to +4 and i should be good to go ???? any help on this would be great thanks. Quote Link to comment Share on other sites More sharing options...
CFH87 Posted August 21, 2011 Report Share Posted August 21, 2011 Depends on location and elevation... Quote Link to comment Share on other sites More sharing options...
fastquad02blaster Posted August 21, 2011 Report Share Posted August 21, 2011 I think you would be in the ballpark with the 20cc domes and plus4 timing. You will have to ride it easy untill you find out for sure but you should be pretty close with that setup. You might get away with 19ccs. Ive heard of guys on here running 19s on 93 octane. You would just have to do an accurate compression test to figure it out. Quote Link to comment Share on other sites More sharing options...
crsracing Posted August 21, 2011 Author Report Share Posted August 21, 2011 Well I live in Nova Scotia Canada im roughly 90 feet above sea level ( 28 meter ) What should my compression be at for pump gas ? ......you say i will have to check it to figure it out . just wondering where it should be at ....Thanks . Quote Link to comment Share on other sites More sharing options...
Pasi S. Posted August 21, 2011 Report Share Posted August 21, 2011 My friend has a 421CUB at sea level. Andy from M&M told to use 22cc noss domes for pump gas. The stock plate is modded to +4. Quote Link to comment Share on other sites More sharing options...
252wheelieking Posted March 31, 2012 Report Share Posted March 31, 2012 Im currently in the same situation & would like to know a positive answer to this. I am at sea level with 22cc cub domes & wanted to know where my compression should range & a safe timing to run with these domes? Thanks Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted March 31, 2012 Report Share Posted March 31, 2012 Get yourselves a compression tester! You need to figure out your dynamic compression ratio. If your static compression is below 155psi and you are at +4 or below on your timing its generally pretty safe to run high octane pump gas like 91 or 93, whatever you can get where you are. That close to sea level I would go with a 21 or 22cc dome and start with your timing at +4 or lower. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted March 31, 2012 Report Share Posted March 31, 2012 Get yourselves a compression tester! You need to figure out your dynamic compression ratio. If your static compression is below 155psi and you are at +4 or below on your timing its generally pretty safe to run high octane pump gas like 91 or 93, whatever you can get where you are. That close to sea level I would go with a 21 or 22cc dome and start with your timing at +4 or lower. exactly. while cranking PSI gives you an idea of what you need if you have known parts, you cannot just say at XXXpsi or whatever you need to run race gas. you need to take into account the dome design. a stock head at 160psi has a different octane than most off the shelf domes at 160psi. also the CC of the dome usualy doesnt take into account the squish area OR squish. Quote Link to comment Share on other sites More sharing options...
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