trouble jetting a CV on a 61" panhead

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henriksonne
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trouble jetting a CV on a 61" panhead

#1

Post by henriksonne » Tue May 11, 2010 10:19 pm

I have just rebuilt the engine on my 61" and installed a CV carburator on. It starts right up, it will only run with the choke 01/2 up. With no choke and warm engine it idle smoothly, but I tvist the trottle to rev it up, it dies. It doesn´t backfire out the carb. no indications of lean mixture. It seems more like the carb is drowing the engine.
it running these jets. 185/0.45 and 1.5 turns on the mixture screw

Can anyone help me which way to go on the jet sizes?

Does the CV choke add more fuel and air, or just more air?



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Re: trouble jetting a CV on a 61" panhead

#2

Post by Panacea » Wed May 12, 2010 1:45 am

Yes those jets are too big, bout right for a 84" stroker, try a couple sizes smaller. Here is a CV page...Mike http://www.johnsmotorcycleparts.com/kei ... images.htm

john HD
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Re: trouble jetting a CV on a 61" panhead

#3

Post by john HD » Wed May 12, 2010 2:01 am

leave the main alone for now and try about 3 sizes smaller on the pilot jet.

work back up from there if needed.

john

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Re: trouble jetting a CV on a 61" panhead

#4

Post by john HD » Wed May 12, 2010 2:03 am

also check for manifold leaks.

john

henriksonne
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Re: trouble jetting a CV on a 61" panhead

#5

Post by henriksonne » Wed May 12, 2010 9:13 am

thanks

I have tried to check for intake leak, but couldn´t find any, but is it likely that it´s leaky, when engine runs smoothly at idle and okay on the road with 1/2 choke. No cough or backfire, when releasing the trottle at traffic lights and roundabout.

I only have 0.42 pilot jet, so I will try that first.

Bike´s running a set of special exhaust.(paughco upsweep pipes, with Bartel perfornance mufflers), what impact will this have on the jet sizes? smaller? bigger?

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Re: trouble jetting a CV on a 61" panhead

#6

Post by john HD » Wed May 12, 2010 11:29 am

let us know how your plugs look....

john

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Re: trouble jetting a CV on a 61" panhead

#7

Post by Dave_R » Wed May 12, 2010 4:23 pm

I have a 74" Pan bored 0.060 over and I run a 45 low speed jet and a 160 Main.
Since your idle and just above is good (45 jet), then I would leave that one alone.

The main jet and needle height is most likely where the issue is, since that is what controls the above-idle to upper throttle positions.
(You can adjust the needle height by adding very thin washers under the retaining clip if your needle is a non-adjustable type).

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Re: trouble jetting a CV on a 61" panhead

#8

Post by Panacea » Thu May 13, 2010 12:19 am

The needle for an 88 sportster works well also...

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Re: trouble jetting a CV on a 61" panhead

#9

Post by Pomike » Sat May 15, 2010 11:56 pm

That carb on the CV article looks like a butterfly carb to me. Am i just going goofy, or what?
Mike

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Re: trouble jetting a CV on a 61" panhead

#10

Post by RUBONE » Sun May 16, 2010 3:50 am

C-V carbs are butterfly carbs. The C-V aspect of it is a variable venturi, basically the C-V slide opens or closes the venturi size depending on demand. The butterfly creates the demand, the engine creates the vacuum or rather negative pressure on the backside of the butterfly and on the slide. When the throttle opens the butterfly opens allowing flow past it but regulated by the position of the slide relative to the pressure drop drawing it up.
Robbie

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Re: trouble jetting a CV on a 61" panhead

#11

Post by Pomike » Sun May 16, 2010 10:04 pm

You are absolutely right. When I glanced at the pic, I thought it was one of the old butterfly Keihns H D used in the 80's.
Mike

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