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Carb size on 399cc 81mm bore esr cylinder 77 stroke

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diesel53

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Discussion starter · #1 ·
Some specs, going to be ridden at sea level:

cr ignition plus 8 timing
trx11 pipe
81mm x77mm stroke, drag port, 44mm intake.

So I only have a 39mm carb at the moment, and I know its not enough. Im concerned it will cause issues. Any tips for jetting until I can get it bored to a 42.5??

Thinking of starting at a 180 main, 55 slow and middle position on the needle.
 
#2 ·
I have a motor really close to what you have. I too tried exactly what your trying, and it seemed like the thing had restrictor plate on it. It was fast but nothing like it should've been. ESR told me with the pwk that I have to start with 195mj. It wasnt even close, I ended up all the way down to a 165 or 170(cant remember for sure).
Shortly after I switched to 44mm Lectron, I had hell with it at first, but I got plenty of help from this forum. Now it screams.
 
#4 ·
diesel53 said:
Some specs, going to be ridden at sea level:

cr ignition plus 8 timing
trx11 pipe
81mm x77mm stroke, drag port, 44mm intake.

So I only have a 39mm carb at the moment, and I know its not enough. Im concerned it will cause issues. Any tips for jetting until I can get it bored to a 42.5??

Thinking of starting at a 180 main, 55 slow and middle position on the needle.
Click to expand...
81mm bore? how far can these 370 esr cylinders be bored out to thats a fair amount already isn't it, i wouldn't of thought you'd seize it with a slightly to small carb aslong as the jetting is rich enough.
 
#5 ·
On my 370 on gas I ran a 40.5 and I belive my main was a 165 or 168 I too went to a 44 lectron and then to a 48 lectron. What a diff on the big end once you go to a lectron. They pull like freight trains
 
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#9 ·
Yes they are easy to tune period. Gas or alky.
 
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#10 ·
Lectron all the way. Give Packard a call and he will fix you up.
 
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#11 ·
44 has been gone awhile I ran the 48 hv for 2 years then I upgraded to my puma
 
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#12 · (Edited)
diesel53 said:
Some specs, going to be ridden at sea level:

cr ignition plus 8 timing
trx11 pipe
81mm x77mm stroke, drag port, 44mm intake.

So I only have a 39mm carb at the moment, and I know its not enough. Im concerned it will cause issues. Any tips for jetting until I can get it bored to a 42.5??

Thinking of starting at a 180 main, 55 slow and middle position on the needle.
Click to expand...
You really only can bore a Keihin to 40.50MM measured at the slide center line:) Jetting a 39MM to start: 182 to 188 Main, 52 to 55 Pilot, DGH, CEL or CEJ needle on 3rd clip, 1 1/2 turns out on AS. Plug Chops to determine fina jet sizes.

Go with a 44MM or 48MM Lectron if top end power is what you are looking for.

Carlos
 
Discussion starter · #18 ·
oh no, much more lol... I know its messed up. Probably 10mm below the floor. Motor will be sent to Tapia racing soon. Im done with ESR.

Bike ran moderately but not well. Not sure what symptoms that would create though. Powerrange was at the botttom end with a non existant top end.
 
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diesel53
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