The 488 and 771 do NOT have accelerator pumps right? Just different metering circuits? Have you tried the 813 with accelerator pump Scott? Would you like to try one?

Marc,

No, I have not never tried the 813

As with all things unknown, always willing to try something new !

** No .. 488 and 771 carbs don't have accelerator circuits.
( They are however the Only Carbs I race with. )

My GUESS ... is that likely an 813 is calibrated closely to the 257 allowing leaner static low needle settings, then have the accelerator circuit make up for or lessen the lean spot they have.

I bought one of the kit's Carb and spark plug, I couldnt get the carb to run right on the dyno, it kept surging and no matter what I did I couldnt stop it, needless to say I didnt water test it......

That's odd...I had good results...been a while though, will have to try it again and report back on settings I get.

Scott, I will send you a brand new one for testing. Maybe you can report back with your findings? Please Email me your shipping addy...don't know if I still have it. Will be faster than me searching through all my stuff lol.

Which carb do you like better Scott 448or771?

Bruce Carrigan wrote:
Find they both work equally well, But 488's are NLA these dayz. So all we can get now is 771's

BTW. Just tonight saw a post for 10 of the 771's for $36 each on JRCBD.
www.jrcbd.com/showthread.php?t=13151
My stock is good or I would jump on all 10

Regards,
Scott

I'm not sure why I need a clean, crisp idle. I mostly want the engine to stay running and come up from 8,000 to 15,000 rpm quickly. We had to block one of the low speed jets in the Tillison carb on our CMB 35 SAW engine so we could control both the high and low speed flow completely with the needles. We only wanted the engine to keep running for the turn around when the top end mixture was correct.

Another interesting finding on the flow bench is that the flow may increase if the butterfly is over opened slightly. It's surprising how tiny things affect the flow. Butterfly streamlining, cutting the shaft, and similar modifications help more than opening the bore.

Lohring Miller