Starkruzen wrote:
Neal, does the 42mm carb have this?

No.We don't have a butterfly. the 42 alsways has air flow since the slide does not shot off air flow thru the venturi as would the butterfly

The HSR carburetors are unique in that they have their own built in coasting enricher. When the slide is closed during coasting the higher than normal vacuum behind the slide can result in more fuel being pushed up through the pilot circuit and the increased velocity through the slide cutout can result in fuel being pushed up past the needle.

When the throttle is closed on the stock carburetor the needle jet and all but one (maybe 2) of the pilot ports are isolated from the high vacuum behind the throttle plate. Because the idle mixture port fuel is diluted by air the only way to richen the mixture is to cut off some of the air. At a certain high vacuum signal the enricher cuts off the air from the primary air jet to allow more fuel to flow. As far as I can tell it doesn't work during low rpm coasting which explains the burbling/popping that may still exist while coasting up to a red light or stop sign. One could modify the enricher spring so it stayed on longer but that might result in it being engaged during normal cruise.

"Would have saved ya $60!"

Thanks Curt, sharing parts has always been a real cool thing about this site, and I had actually thought about asking on here at first, especially considering the recent rash of swapping stock carbs for 42mms going on .. LOL

Anyhow, it gradually occured to me that the delicate diaphragm once installed and used for any length of time, would have stresses particular to exactly how it had been installed. So it occured to me that if I was going to replace it, I should replace it all new, and without the factor of prior stresses, possibly contrary to whatever stresses it would be under in the exact position it ended up in on my carb. This is also why I did spend the extra 30 of the 60+ total to order a new diaphragm and fresh spring, with the 30 dollar plastic cap that had broken.



Max

I know this discussion is a month old, however....changed out stock air filter with a K&N. Noticed fuel residue in housing area. Is this normal? Did rejet carb when after market pipes installed. Exhaust pipe manufacturer recommended main jet of 200. Still wondering if this could be causing this......before, it was 182.5 and remember it doing this too. Have noticed higher fuel consumption and would like to make it a bit more efficient for mpg. Any suggestions? Pipes are 2 1/2" Hard Krome Kickers.

leslie.hobgood wrote:
I know this discussion is a month old, however....changed out stock air filter with a K&N. Noticed fuel residue in housing area. Is this normal? Did rejet carb when after market pipes installed. Exhaust pipe manufacturer recommended main jet of 200. Still wondering if this could be causing this......before, it was 182.5 and remember it doing this too. Have noticed higher fuel consumption and would like to make it a bit more efficient for mpg. Any suggestions? Pipes are 2 1/2" Hard Krome Kickers.

You don't need to jet for pipes only and a K&N filter is the stock box, go back to stock jetting , remove the AIS, and tweak the pilot screw 1/8 to 1/4 turn out

Thanks. Sounds simple enough. Will try tomorrow!!

With a carb you can always get a burp of gas in to your airfilter area. I have done tons of services on different bikes and have found this on most bikes. As long as it isn't a large amount and it isn't soaking the area. You should be ok.

According to Mikuni exhaust systems without baffles, particularly long, straight open pipes, increase reversion pressure. This mainly occurs at low rpm throttle opening. Just FYI.

if i seen parts hanging out of the stock carb i would say "baby the carb broke and i need a new one its the 42mm mikuni" then for the cables i would say "well the cables look alittle worn so im gunna buy new ones while im at it you know safty first" .

Smokescreens you're Bad!
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Spydr