Domesize Cheetah Cub 421 Germany

[Philipp91]

Hi Guys,
I'm from Germany and I'm just building a 421 cub banshee.
Daily street driven.

To the engine:
- 421 Cheetah Cub
- hot rods crankshaft +4 115mm
- 2x mikuni tm 35mm

Now my question:

I want to drive 98 octane (super plus gas).
200 meters above sea level.
Which domes, psi and squeeze edge should I drive?

 

 

 

 

[trickedcarbine]

Hi Guys,

I'm from Germany and I'm just building a 421 cub banshee.

Daily street driven.

 

To the engine:

- 421 Cheetah Cub

- hot rods crankshaft +4 115mm

- 2x mikuni tm 35mm

 

Now my question:

 

I want to drive 98 octane (super plus gas).

200 meters above sea level.

Which domes, psi and squeeze edge should I drive?

 

 

There is a slight difference in the way Euro fuel is rated then fuel is rated here in America. That said your premium is actually about like ours regardless of the difference in number. https://www.google.com/amp/s/amp.reddit.com/r/explainlikeimfive/comments/1iedtv/eli5_why_does_american_fuel_have_less_octane_than/?client=safari

If it were me, I'd want it nice and reliable since you said it's gonna be on the street. I'd choose to have a set of 24cc domes made. Definitely order them from someone reputable that has built that same motor many times. It will pay off in the long run. I'd imagine they would set Squish up fairly conservatively and be between .050 - .055 clearance.

[J-Madd]

Does anyone run 23 cc on pump gas? That's what I'm going to try.

[ClaudeMachining]

I will tell you something about comp, for what ever reasons, all guys here in Quebec are running at least 1cc less to have the same comp as you yankees.

 

I'm running 23cc at 300' and it give me only 135psi and i'm on a low port setup.

 

I know it may look dumb, but that's my observation.

[J-Madd]

Good to know Claude. I'm 300' ASL also. And it's a low port (serval).

[ClaudeMachining]

Good to know Claude. I'm 300' ASL also. And it's a low port (serval).

Then i think 23cc is a good start.

 

When we did my engine, Bill was not sure about 23 or 24cc. We didnt want to be over 150psi on 91-93 octane. So i told him to send me both 24 and 23cc.

 

23cc gave me 135psi. I will order 22 and 21cc this winter to try stuff next summer.

[Pasi S.]

test

[Pasi S.]

I´d say that your 98 is close to our 98 here in Finland. My friend has a 421CUB.

His domes are custom cut 23cc domes. (Andy at M&M ATV)
​Our pump gas is 93.7 R+M/2 or higher.