Trinity 421 cheetah jetting

[banshee421]

Working on jetting, had 145s in it burbled bad. Put 135s still a little burble but a lot better. 135s seems to lean for a 421? Any ideas on what the jetting should be?

It's a trinity 421 cheetah power valve, 18cc domes, CPI pipes, 35mm pwks. Compression is 150 each cylinder.

 

 

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[sick421]

I think u may have 35mm a/s not regular pwk , the airstrkers like the smaller main hence they are a way richer carb , the vary 10 points smaller than the pwk , for example the pwk would run a 155 main the a/ s will end up around 145 main . I have the same motor and i run a 145m 42 p , and 1 1/2 turns af with 35mm a/s , 20cc domes , drag port , matched cases , cpi inframe sb , +7 timing , 8in k&ns,

[sick421]

Oh yea and another this 150psi comp is crap for 18cc domes , another theory too is that the bigger bore motor tend to draw more full threw a smaller main jet

[WINDYCITYJOHN400]

Trinity      

 

Check your squish! There you heard it here first. Now when your top end goes all molten, you can't say I didn't warn you.

[10milmike]

With the shitty Trinity domes i bet it is .70...

[banshee421]

.055" squish. I asked a builder for custom cut domes and they said all was good at .055" I thought my first cheetah had 175 psi. I bought this quad used so not positive the details on anything but what I put into the motor. Talked with the previous owner he thought it had big bore CPIs and 36mm keihin carbs. Didn't even know they made 36mm keihin carbs?

 

 

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[10milmike]

.055" squish. I asked a builder for custom cut domes and they said all was good at .055" I thought my first cheetah had 175 psi. I bought this quad used so not positive the details on anything but what I put into the motor. Talked with the previous owner he thought it had big bore CPIs and 36mm keihin carbs. Didn't even know they made 36mm keihin carbs?

 

 

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.55 is that the same squish clearance I have. But I do not have Trinity anything in my motor. Had a great builder get all that shit out.

 

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[10milmike]

.055" squish. I asked a builder for custom cut domes and they said all was good at .055" I thought my first cheetah had 175 psi. I bought this quad used so not positive the details on anything but what I put into the motor. Talked with the previous owner he thought it had big bore CPIs and 36mm keihin carbs. Didn't even know they made 36mm keihin carbs?

 

 

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.55 is the same squish clearance I have. But I do not have Trinity anything in my motor. Had a great builder get all that shit out. When I first bought my cheetah years ago I had the same problem the owner had no idea what was done to it. Thousands of dollars later finally got it running good. I thought it ran strong before but had nothing but problems with it. Could not keep a set of reeds in it to save it's life. I was buying a set every trip. Shit was getting expensive. And the thing was detonating like no tomorrow. Live and learn.

 

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[WINDYCITYJOHN400]

.055" squish. I asked a builder for custom cut domes and they said all was good at .055" I thought my first cheetah had 175 psi. I bought this quad used so not positive the details on anything but what I put into the motor. Talked with the previous owner he thought it had big bore CPIs and 36mm keihin carbs. Didn't even know they made 36mm keihin carbs?

 

 

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You don't want to run BB CPI's on that motor. I tried that on mine......SB Shearers made 14 more HP and matching low end torque!

 

CPI's are still sitting in a corner. Too nice to sell, but I don't have anything they would work well with. So I keep them around for dyno testing....