22cc domes +4timing

[tgbanshee]

I would do a compression test just to be safe. If you're below 160psi, which you probably will be, you will be fine on pump gas. If you're above 165psi, I would say at least a 50/50 mix is mandatory. I thought I was going to be able to run pump gas when I put my motor back together with 21cc domes, a 4 mil stroker, .020 overbore, and fresh pistons at sea level but my compression turned out to be way higher than I expected. I sat there scratching my head wondering why my brand new Matco gauge read 180psi in each cylinder. Borrowed a friends gauge and got the same thing. Gave Jeff @ F.A.S.T. a call and he said it was because I was running a spacer plate under the jugs for the stroker which increased the case volume, my sea level elevation, and no porting. Bumped my timing back to +2 from +4, mix 50/50 93 pump/VP C12, and haven't had any problems in almost a year of riding. Definitely try and borrow a compression tester if you don't have one and measure your compression if you want to be 100% sure you're ok to run pump gas. It is unlikely but you happen to be over 165psi, you will at least know you should be running part race gas and this could save you from some costly repairs in the future.

Edited January 13, 2009 by tgbanshee

[Snopczynski]

Sea Level 1000' 2000' 3000' 4000' 5000'

18cc 197 178 171 170 165 145

19cc 183 167 160 158 152 137

20cc 169 156 149 146 140 129

21cc 156 145 138 134 128 121

stock 130 125 118 112 106 100

 

If the motor is completely stock, this is what it should be. 22cc is stock.

[R/C Hippie]

Sea Level 1000' 2000' 3000' 4000' 5000'

18cc 197 178 171 170 165 145

19cc 183 167 160 158 152 137

20cc 169 156 149 146 140 129

21cc 156 145 138 134 128 121

stock 130 125 118 112 106 100

 

If the motor is completely stock, this is what it should be. 22cc is stock.

I thawt stock was 24cc ok thanks guys

[Snopczynski]

I think stock is like 22.5 or 22.75 cc if I remember right. If it was 24cc, then noss would probably list a 22cc and a 23cc dome, dont ya think?

[csrmel]

22cc is NOT stock. i don't know what exactly stock is, i have heard 23.5 thrown around before though.

 

i had a BRAND new banshee just broken in with a nice tight motor, had only a few hours on it. after break in, it had 133psi compression on both cylinders. i change to cool head with 22cc domes, it went up to 149psi. this is on a new motor, just broken in, no carbon deposits, no base gasket thickness problems etc. brand new factory motor in a brand new factory banshee.

 

 

 

plus i checked my compression tester against my air compressor, they both read exactly the same if i hook up the tester to the compressor. the compressor gauge read 120psi, the tester read 120.

 

p.s all my compression testings are at sea level.

 

i was able to run all day every day with 22c's and +4 on 91 octane at sea level. never had a problem, even after minutes of full throttle 6th gear drifting.

[Snopczynski]

22cc is NOT stock. i don't know what exactly stock is, i have heard 23.5 thrown around before though.

 

i had a BRAND new banshee just broken in with a nice tight motor, had only a few hours on it. after break in, it had 133psi compression on both cylinders. i change to cool head with 22cc domes, it went up to 149psi. this is on a new motor, just broken in, no carbon deposits, no base gasket thickness problems etc. brand new factory motor in a brand new factory banshee.

 

 

 

plus i checked my compression tester against my air compressor, they both read exactly the same if i hook up the tester to the compressor. the compressor gauge read 120psi, the tester read 120.

 

p.s all my compression testings are at sea level.

 

i was able to run all day every day with 22c's and +4 on 91 octane at sea level. never had a problem, even after minutes of full throttle 6th gear drifting.

 

Usually after a motor is broken in the compression will drop a little psi. Im pretty sure the cc of a stock head is in between 22cc and 23cc. It makes sense if you do the math. Each 1cc drop in size is about 13-14 psi. so 22.75cc's would put you at about 130-133 stock psi. Completely stock, my motor (not broken in) with 21cc domes was 145 psi on a certified MAC compression tester.

[csrmel]

ok, whatever the stock cc is, i know its not 22.000cc's.

if it's 22.75, or 23, etc . well,ok. but its not 22.

 

 

why would a motor LOSE compression after its broken in? my brand new banshee came to me with about 125psi after i started it for the first time and warmed it up for 5 minutes. afters i broke it in, it went up almost 10psi on each cylinder.

Edited January 14, 2009 by csrmel

[Snopczynski]

No, that means your intial compression was 135 psi then. You always check compression after running the bike, never cold because the motor is not fully seated when cold.

 

I dont know why it goes down, I dont remeber what dave told me happens.

[Flying_ij]

K...after reading all the post........Im stuck between 22cc domes and 21cc....my bike has FMF pipes....+4 timing.....k&N...I plain on running 91 octane.....but...I will be buying a Coolhead in the next week or two.........so.....what would I buy?...22 or the 21 domes.....I'd like to have the same cc's as taking .010 off the stock head...and I am at sea level......any help would be COOL! :biggrin: