race gas or pump?

[ryskie22]

i have had mixed input on fuel and on how to check the compression, i have 19cc domes in a prodesign cool head on a 350 with a hotrod crank, advanced 4 degrees, 33 keihn pwk carbs jetted at 165 mains and 48 pilots, also the tops of the jugs were surfaced due to imprefections, now my queston is that should i be running straight 110 or 50/50 mix with pump or straight pump gas? ive checked compression many different ways, i really dont know what the proper way is but here it goes, i first kicked the shit out of it and it never got over 155,now if i check one cylinder while the other is running it has 180 to185 idleing of course, and the cylinders are even and this is a fresh topend. so what is the proper way is it that i cant kick it fast enough? from the info ive found this should have 180, oh and i am at sea leval to 500 feet, thanks for everyones help on this its been a question ive had for a long time.

[TeamRealtreeHD]

Turn the bike off....

 

Screw the tester threads into the spark plug hole with the other plug still in.

 

Hold the throttle wide open and kick like hell... when it stops, take the reading. Do the same for the other cylinder.

 

Sounds like 155 PSI is a little low for that setup... that would probably run on pump 93-94 octane without problems.

 

Test it again with the above instructions... see what you get.

 

But the general rule is 150 PSI and above is the race gas pressures. You could most likely get away with pump gas, but I would mix 110 and 93 half and half (50/50) to be safe. We don't know for sure what your compression is right now. Do it again and report back.

 

But you should be higher than 155 for sure

 

I have 190 PSI and I run 105 octane (116/93 mixed 50/50) without problems.

 

Good luck

Edited August 19, 2008 by TeamRealtreeHD

[ryskie22]

Turn the bike off....

 

Screw the tester threads into the spark plug hole with the other plug still in.

 

Hold the throttle wide open and kick like hell... when it stops, take the reading. Do the same for the other cylinder.

 

Sounds like 155 PSI is a little low for that setup... that would probably run on pump 93-94 octane without problems.

 

Test it again with the above instructions... see what you get.

 

But the general rule is 150 PSI and above is the race gas pressures. You could most likely get away with pump gas, but I would mix 110 and 93 half and half (50/50) to be safe. We don't know for sure what your compression is right now. Do it again and report back.

 

But you should be higher than 155 for sure

 

I have 190 PSI and I run 105 octane (116/93 mixed 50/50) without problems.

 

Good luck

i have tried it with the throttle wide open and it makes no difference!

[ryskie22]

sorry about all the other posts guys dont know what the hell happend

[TeamRealtreeHD]

Now that I am looking at the mods again, that is most likely where the compression should be. 155-160 sounds right on. Your elevation was not stated though. That makes a difference with pressure and such on stuff.

 

I would mix 110/93 50/50 with 155 PSI. But you can most likely get away with pump.

 

I think xXBlessedWithDeathXx runs 19cc domes and +4 timing. He has 34mm Keihins on his, and is bored .060 over with CPI inframe drag pipes. He is running pods too. He runs pump gas no prolems either... so you should be able to get away with it.

 

We are at 1200-1300 feet above sea level. I don't know his compression numbers, but they aren't low. His bike runs hard... really hard.

 

But me personally I would mix 50/50. But most wouldn't if they didn't have to. Either decision won't hurt the bike.