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Message started by strang on 11/14/12 at 14:13:08

Title: Carb tuning - my next step?
Post by strang on 11/14/12 at 14:13:08

Have just put new jets in - 52.5 pilot, 152.5 main
Did the spacer mod - went with half spacer.

Back fire is now much less and no backfire on switch off.

But still getting small backfires on sharp descel in 2nd gear.
I am doing a lot of city riding so this happens quite a bit in response to idiot cagers ::)
Where do I go from here - less spacer or bigger pilot jet?

Title: Re: Carb tuning - my next step?
Post by justin_o_guy2 on 11/14/12 at 14:17:55

Slow down the throttle close move & see how that does ya.

Title: Re: Carb tuning - my next step?
Post by verslagen1 on 11/14/12 at 14:55:37

This is a carb, not a mapped FI squid, ya ain't gonna get it perfect.

a bf in response to an idiot cager sounds perfect to me. 8-)

what's your mpg?

Title: Re: Carb tuning - my next step?
Post by strang on 11/15/12 at 02:29:11

it's a little bit too often otherwise I'd live with it.
will calculate mpg on this next tank and get back.

Title: Re: Carb tuning - my next step?
Post by Routy on 11/15/12 at 03:30:34

Quote:
Where do I go from here - less spacer or bigger pilot jet?
----------------------------------------------------------------
You should not tune a carb to eliminate backfire. Many have, and many have failed. The air screw should be adjusted for best idle, but can sometimes be cheated one way or tother to lessen backfire.

I did a 1/2 spacer mod to correct a lean spot in the low/midrange, but it did not change BF one bit, nor did I expect it to.

The main should be adjusted to performance and "spark plug read", and not because of what someone said or read.

Under normal conditions, and no malfunctions like a leaking exhaust etc, one should be be able handle the BF by learning to control it w/ the throttle. Otherwise they quite possibly have the wrong bike.

All IMO of course.

Title: Re: Carb tuning - my next step?
Post by ToesNose on 11/15/12 at 06:11:40

Nice summation Routy, I myself enjoy a good back fire ;)

Title: Re: Carb tuning - my next step?
Post by strang on 11/15/12 at 11:36:20

The whole picture:
stock the bike wasn't really ever happy unless it had the choke on the 1st notch - otherwise it had sluggish take off/flat spot. Now it's much better (1/2 spacer mod) but is still a little bit sluggish and still takes a little bit too long to warm up - I just have a gut feeling that it wants a bit more fuel in the first 1/4 of throttle.

Title: Re: Carb tuning - my next step?
Post by Dave on 11/15/12 at 11:51:19

Carb tuning is a trial and error event....and it takes some work to get it right. Right means it will run well, accelerate and idle smoothly, and get good fuel mileage. The big single will backfire some.....even when running correctly.

It took me about 5 different combinations before I had the bogging corrected for the 1/8-1/4 throttle. The cure for mine was to take one washer of the top of the needle and only keep 2 (started out with 3), then I was able to drop my main to a 150 and my Pilot to a 50. It now runs really sweat! (Stock air cleaner, Dyna muffler).

I would suggest raising your needle the thickness of one washer and see how it runs. On mine the lean spot was gone - but it got too rich on the main and pilot and I had to drop them down from the 152.5/52.5 to the current 150/50.