Can someone with direct experience tell me if I can run 20cc domes and pump gas, or am I required to mix race fuel? If you have done this, or if you tried and ended up with detonation, please let me know.

Details - stock porting, T-5's, pro-flow kit, boyesens (that's it for now).

Thanks.

 

I have been running 20cc domes in my banshee for over a year with 93 octane pump gas with no problems. I believe that Pro Design recommends race fuel for 19cc and below.

 

Thanks.

Have you run a compression check? If so, what is your elevation and compression readings.

I am skeptical of the chart tha pro-design puts out and wanted some verification.

 

VITE is RITE... I run a Trixxhead, and they say that 20cc domes are the last size you can use and still keep running pump gas. I would recomend 93 or 94 octain though.

 

Could you post that chart I'm looking for Compression listings for 20cc domes but a list for all would be good. A phone number for pro design would help if someone has that.

Thanks

 

The chart is in the rocky mountain atv catalog. It's the same thing I saw in another thread on this subject. The problem is, I don't trust the numbers. Theres a 6 psi difference in between each dome size and elevation starting at 1000 ft and up , but at sea level there is a 12 psi difference. That's not possible. Somewhere they (Pro Design) messed up, I'm pretty sure. But an easy way to see what numbers are accurate are to ask people here that have stock porting and different dome sizes what their measured numbers are. That's what I'm after.

 

With 20cc domes I was running 150 psi with stock bore on my last reading... Of course that was 1 years worth of riding which is a lot for me. I ride almost every weekend. I live in Tulsa, Oklahoma and I'm not sure of the eleveation here.
I did a top end last week and broke the motor in that weekend. It was bored 20 over and I re-installed the 20cc domes. I will take a reading this weekend and reply with the results.


99 Banshee
+2,+1 Denton A-Arms
+2 Durablue Axle
TCS Zero Preload Shocks Front/Back
FMF Fatty Mid-Range Pipes
Cool Head with 20cc Domes
Pro Design Timing Plate Advanced +3

 

Here are some numbers SandmanBlue. This is at 5000 ft. with Pro Design 19 domes and stock porting. Found out the hard way that I need to run race gas with these domes. In CO the pump gas is only 91 octane.
With .040 stock piston compression was 140psi. after break in. With Vito's .080 piston at installation compression was 130psi. After breakin compression was 150psi. One month later compression is 155psi. The Vito's has a higher dome that increases the compression.

 

Well my Banshee is .060 over with 20cc domes around 1000 above sea level @180-170 psi. So I guess thats about right. Now I just have to work out my carb problems.

Thanks

 

you go stricktly by your compression. if you live above sea level you can use below a 20cc dome on pump gas. i have a stock banshee with pipes reeds and no air box. i live at 3200 feet. i run 19cc domes with no problem on 91 octane. i went from 112 lbs of compression to 139. i have friends here that actually run the 18cc domes with no problem. check around where you live or call Kt performance, kim muchmore knows his stuff and he told me the 19cc would be fine.