AFR

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lujote
Posts: 3
Joined: Mon May 17, 2010 4:42 pm
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Hi All, i have been mucking about with a O2 sensor on my new build motor;rapido classic, 71mm wiseco kdx piston, 60mm crank, LTH reedvalve, 24 mikuni tm through airbox and Ron Moss avanti exhaust.

carb setup with 20 pilot 4DH7 bottom clip and 195 main, i am getting AFR ratio of around 12-12.5 from 1/4 to 3/4 throttle and 11.5 at WOT , in 4th gear (4.7 ratio) i run out of revs @6300 am i too rich at WOT

wondered if any of the dyno boys who use this forum have any input on what i should be shooting for ? i can datalog AFR and RPM if thats a help

Cheers
Paul
OzOAP
registered user
Posts: 306
Joined: Sat Aug 01, 2009 2:11 pm
Main scooter: Vespa PTS1E
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This may be of interest...or send you to sleep

http://scooterotica.org/forum/viewtopic ... dyno+ratio
eibargum
registered user
Posts: 368
Joined: Wed Jan 07, 2009 6:38 pm
Main scooter: Vespa PX210 Polini
Contact:

I have my engine,s set up on Chiselspeeds dyno [ RB and Muggy] which uses co levels out of the pipe, to be safe Martin sets them up to give me 6% co which i believe to be 12.25-1 AFR, i have been told you can go leaner than this on alloy barrals but i air on the safe side, so you may be a bit rich at 12.5-1, aim for 12-1 then do plug chops and richen up if needed. Make sure your choke is turning off properly before you start, the choke springs in Mikunis are very weak.
lujote
Posts: 3
Joined: Mon May 17, 2010 4:42 pm
Contact:

The thread makes interesting reading! as eibargum suggests i will shoot for 12.1 and monitor the plug from there, i am going to replace the 4DH7 needle with the richer 5N13 as it was on the richest setting and a bit peaky from 1/2 to 3/4, i will post the final numbers up when finished

Paul
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