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CV CARB PROBLEMS

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Jamesville
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CV CARB PROBLEMS

#1

Post by Jamesville » Thu Jan 18, 2018 9:12 pm

Hi Guys

i have some CV problems and was hoping some of you guys might have some ideas....

I have a completely original looking 1947 Knucklehead but the engine is a 74’ S&S Knuckle. I got sick of the S&S carb and this week installed a CV (I always loved them).

After I installed the CV, it started ok, it idled ok and ran good at the top of the gears, but as I left idle it missed fired badly out of the carb until I got to higher revs.

I pressured tested everything and all was good. I replaced all the rubber inside the carb, i changed the 45 pilot to a 48 and 180 main jet. Things improved a lot but were far from perfect, it was still missing, just not as bad.

I wanted to go up to a 50 pilot but the store was out, so I went with a 52. Now the bike starts great, idles great, takes off great and runs through the gears great. The only problem I have now is when the bike is running in too lower revs in 2nd, 3rd and 4th gears it misses out the carb slightly. And the higher the gear the worse it is.

My questions are…

Do you think a 52 pilot and 180 main is an ok setup? Since I went up to a 52 pilot jet should I go up in main jet?

The weather here in Denmark is very cold, its 33f. Could this be effecting the carb?

Do you have any ideas why it could be missing in low revs?

Thank you in advance for any advice, it’s very appreciated.



nmaineron
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Re: CV CARB PROBLEMS

#2

Post by nmaineron » Fri Jan 19, 2018 12:17 am

Where is your low speed mixture screw at? Turn it out and the way that you explain it you could probably go a 1/2 turn to start with.

Larry
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Re: CV CARB PROBLEMS

#3

Post by Larry » Fri Jan 19, 2018 1:49 am

My experience with a CV on a UL suggests that they don't like cold weather.

1950Panhead
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Re: CV CARB PROBLEMS

#4

Post by 1950Panhead » Fri Jan 19, 2018 1:51 am

After I installed the CV, it started ok, it idled ok and ran good at the top of the gears, but as I left idle it missed fired badly out of the carb until I got to higher revs.
To lean, increase jet size or turn crew to richen.

mark59
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Re: CV CARB PROBLEMS

#5

Post by mark59 » Fri Jan 19, 2018 2:49 am

run a CV on my 39UL flathead, i have found a lighter spring and a very slightly larger port in the slide help time the slide reaction/lift to my port velocity. the spring found in the CV jet kits is what i use. i run a fuel air meter and can see my mixture in real time, great tool for fine tuning and peace of mind.

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