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CV40 Jetting / 100 HP

16K views 13 replies 11 participants last post by  1955 bones 
#1 ·
Hi.... I would appreciate your opinions regarding rejetting my cv40 carb. I have a 99 low rider.. with andrews 37b cams, V + H Strait shots, Crane HI4tc fireball ignition, Screamin eagle 10.25 to 1 pistons in a 95 in build. Ported heads and intake. (Before the heads and intake and the 10.25 to 1 - 95 in build it dynoed at 79.8 hp). I expect to pull around a 100 hp now. I opened up the carb and someone has already fiddled with the idle mixture screw and has it 1.75 turns out. It still has the 42 slow jet and a 175 main jet in it. The altitude here is 1800 feet. So here are 3 questions.... 1) with that build which 2 jet sizes do you think would be the best starting point for tuning the carb.... 2) should I drill the vacuum port hole larger in the slide or not... seemed like a divided issue... 3) and what total jet sizes do you think I should purchase to be able to tune this carb. I got a feeling a 45, 48 slow and a 195, 200 main... maybe also a 190 or a 205; either? There is no place around here to get this dynoed and 3 bux a jet is cheap... I dont mind the time spent. All input is appreciated. regards Mefff
 
#2 ·
To use that build, I think you need a bigger carb. That stock CV is not big enough to flow enough to give you what you want. Get a bigger CV or a Mikuni, Or an S&S, if you want all your power.
 
#3 ·
I'd try the 195 main, 48 slow, and then readjust your idle mix needle and idle. Check your plugs, go from there. I would not suggest drilling the slide, it may allow the slide to open too quickly, causing a lean condition. speaking of which...a 42 and 175 seems VERY lean...what kind of milage are you getting?

I don't think you'll gain 20 hp from this though...20 hp is a rather large jump to expect from just carb adjustments. Are you experiancing any backfires, or decel popping?
 
#4 ·
Too small a carb for the engine and mods. Try a Mikuni 42.
 
#5 ·
mefff said:
Hi.... I would appreciate your opinions regarding rejetting my cv40 carb. I have a 99 low rider.. with andrews 37b cams, V + H Strait shots, Crane HI4tc fireball ignition, Screamin eagle 10.25 to 1 pistons in a 95 in build. Ported heads and intake. (Before the heads and intake and the 10.25 to 1 - 95 in build it dynoed at 79.8 hp). I expect to pull around a 100 hp now. I opened up the carb and someone has already fiddled with the idle mixture screw and has it 1.75 turns out. It still has the 42 slow jet and a 175 main jet in it. The altitude here is 1800 feet. So here are 3 questions.... 1) with that build which 2 jet sizes do you think would be the best starting point for tuning the carb.... 2) should I drill the vacuum port hole larger in the slide or not... seemed like a divided issue... 3) and what total jet sizes do you think I should purchase to be able to tune this carb. I got a feeling a 45, 48 slow and a 195, 200 main... maybe also a 190 or a 205; either? There is no place around here to get this dynoed and 3 bux a jet is cheap... I dont mind the time spent. All input is appreciated. regards Mefff
I agree with others. You need a 42 to take advantage of that build. If you can't afford to change carb right now then i'd go with a 50 slow and 200 main in the one you've got.
 
#7 · (Edited)
this guy is at 1,800 ft. elevation. A 40 cv will support 100/100.
A 50 slow is too rich , especailly at 1,800 ft. He might end up at a 200 main with the stock emulsifier tube. the stock 190 main is really too rich for a stock 88" motor at sea level....so for his build at 1,800 ft it's gonna be close.

course everything I just said could be wrong........
 
#8 · (Edited)
Also keep in mind that a stock 99 CV came with a 42 slow jet.(At least the FLT's did and I would assume the Dyna's did too) The slow circuit was changed on the CV carbs in 2000. A 45 or 46 would be plenty big enough. I would think you need to shim the stock needle if that's what is in it.
 
#9 ·
Jets....

Thanks to all for your replys... I have been away as I also drive trains as well as my bike. And no I dont expect to get 100 hp from the jet work alone.... smile. The 79.8 hp was before the 95" bore 10.25 comp pistons and the ported heads and manifold. I have to check to see if this thing is dynojetted this afternoon and go over all your replys.... Thanks Syclone... but heres a question in the mean time. If it is dynojetted.... would it be better to just change the slow and main jets for the dynojet setup or go completely back to a stock setup and jet from there? Another point is: in the Clymer FXD TC88 Service manual it said all models from 99 to 03 are 45 slow 190 main unless they missed early 99's. I am inclined to think this is dynojetted account the 175 main and as for burning lean or popping.... nope... it ran perfect at the 79.8 hp as long as you always ran premium. It screamed to topend with no hesitation as good as 80 hp I would expect. It just is a little slow compared to my brothers 03 fxdl that is a stroked 103 s&s at 126 hp. I dont want to stroke it and spit the cases and go to a 103.... I just want a 100 or so hp. I met a guy on here a year ago... Identical setup except he was EFI and had a diff ign module. He got a hundred and figured I might get 102... anyway.. Thanks again and Ill fill in any answers after I go over my bike today. Mefff
 
#10 ·
100/109 here with 40 CV.
48 pilot, Drag specialties needle from Kehin kit, lets say it's bout one step richer than the N65C, and a 200 main.
AFR goes from 13.9-14 at up to about 1/4 and levels to 13.5 wide open on dyno. Great response, and mileage.
95" 10 to 1, Mackie heads, E pipe, DTT.
Hope that helps.
See classified.

Al
 
#11 ·
Yes it is dynojetted...

I finally got around to looking and yes it is dynojetted.... 1 hole on both sides in the tube v.s. 3 holes. Explains the 42 and 175. So here is my question again... Please review the reply I received below to see what you think. Should I attempt to tune this with dynojet mains and slows which are readily accessible or simply go back to a stock cv40 tube; spring and jets to start? Looks like the member below couldnt do it even with a dyno.
Thanks again ... Mefff

Roadster_G
Premium Member Join Date: Aug 2002
Location: Vacaville, California
Posts: 74

carb
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I have a 98" with 37G cams, head work and so forth. I had a cv 44 with the dynojet stuff and the tuner couldn't get the low end lean enough so we ended up using the CV 40 on a temporary basis. We used a 50 slow with the stock needle shimmed with 2 washers. The main was only a 190 I believe. This was on a dyno with a very good tuner, I pullled 92 hp with 106 tq. By looking at the sheet, it was obvious that I ran out of carb higher up. However, it behaved very nicely below 5000 rpm. I have since put the 44 on and have taken out all the dynojet stuff out of the 44, that would be the lighter slide spring, emulsion tube and main jet, went back to the stock starting point. I believe I found my missing hp.

My point is that you can use the cv 40, but you are way lean right now. I think that you could use a 48 slow and see how it behaves, then start shimming the needle or go fatter if needed. The main would probably be fine with a 190 or so. Yeah, a mikuni would probably be better, but you don't have to spend $$ much right now.
 
#13 ·
Yes it is dynojetted...

I finally got around to looking and yes it is dynojetted.... 1 hole on both sides in the tube v.s. 3 holes. Explains the 42 and 175. So here is my question again... Please review the reply I received below to see what you think. Should I attempt to tune this with dynojet mains and slows which are readily accessible or simply go back to a stock cv40 tube; spring and jets to start? Looks like the member below couldnt do it even with a dyno.
Thanks again ... Mefff

Roadster_G
Premium Member Join Date: Aug 2002
Location: Vacaville, California
Posts: 74

carb
---------------------------------------------------

I have a 98" with 37G cams, head work and so forth. I had a cv 44 with the dynojet stuff and the tuner couldn't get the low end lean enough so we ended up using the CV 40 on a temporary basis. We used a 50 slow with the stock needle shimmed with 2 washers. The main was only a 190 I believe. This was on a dyno with a very good tuner, I pullled 92 hp with 106 tq. By looking at the sheet, it was obvious that I ran out of carb higher up. However, it behaved very nicely below 5000 rpm. I have since put the 44 on and have taken out all the dynojet stuff out of the 44, that would be the lighter slide spring, emulsion tube and main jet, went back to the stock starting point. I believe I found my missing hp.

My point is that you can use the cv 40, but you are way lean right now. I think that you could use a 48 slow and see how it behaves, then start shimming the needle or go fatter if needed. The main would probably be fine with a 190 or so. Yeah, a mikuni would probably be better, but you don't have to spend $$ much right now.
what jets you using in your 44 now after taking out all dynojet things
 
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