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Carb theory/tuning?

Posted: Tue Nov 24, 2009 4:04 pm
by ryrypizza
Does anyone know of literature regarding the CVK32 carbs, or would anyone be willing to give me a breakdown of the functions of the carb. I mean, I'm not a total idiot when it comes to carbs...but I would like to know more.

Other then gaining knowledge, I do need to solve why my left carb is popping when I slow down. I have the idle screws matched as far as I can see, and the idle mix set to standard 1.5 turns, I've tried more/less turns on the mix screw and that doesn't help. The compliance fittings seem to be in good shape as well.

So if any ural-pro's would like to share some insight it'd be greatly appreciated.

Posted: Tue Nov 24, 2009 4:24 pm
by ickie
get a twinmax, the screws settings you read about only get you close, a twinmax will synk the carbs and get you dead on.

here is the carb breakdown/info you requested
http://myural.com/keihin_32cvk_disassembly.htm

Posted: Tue Nov 24, 2009 4:58 pm
by ryrypizza
Yeah I've thought about getting the twinmax, maybe when I get some spare money.

I went through the carb dis-assembly on the site a few months ago so they should be in good shape.

Posted: Tue Nov 24, 2009 5:05 pm
by ickie
Everyone has a different opinion on this, but my CVK32 carbs drove me nuts in 2002 and I bought 2 K-68 carbs and have never looked back. This year I replaced the old k-68's carbs with 2 new k-68's.
I still use a twinmax to dial them in.
:shock: NO MORE LEAKING COMPLIANCE FITTINGS!! :lol:

Posted: Tue Nov 24, 2009 7:46 pm
by berger
Here is an excellent link that will tell you almost everything you need to know about the carb, albeit a 40MM.

http://www.gadgetjq.com/keihin_carb.htm

If you don't have a lot of money to play with jetting, I would get yourself 1 to 4, 2mm stainless washers and insert them (max two each side) under the needle jet on your carb. This mod made a huge improvement with popping on decelerating on my bike, even before I made my airbox mod. Just remember, when you take the diaphragm out, let it sit for a while to air out, as it can be hard to re-install while saturated with gas.

Do a search on needle shim and see what you find.

Posted: Wed Nov 25, 2009 6:22 am
by nemec
don´t have money? use this! :)
I have the same and it work.
http://www.motoguzziclub.co.uk/tech/how ... ometer.asp
Image

than I ordered colortune plug on ebay - it seems good - it is 14mm version - this is good site about it + videos -
http://www.gadgetjq.com/ctune.htm

and finally - I think here you can find good hints for tuning/setting your carb - CV carb tuning procedures -
http://www.factorypro.com/tech_tuning_p ... gines.html

and Harley forum about cv carbs -
http://www.hdtalking.com/fuel_and_carb_related_issues/

and here is russian video of synchronization -


and here is some bmw with "oil" manometr -

Posted: Wed Nov 25, 2009 11:57 am
by JohnBG
Here's a manual and exploded view diagram I found on the CVK carbs.

Posted: Wed Nov 25, 2009 11:59 am
by JohnBG
Sometimes the "popping" on decceleration can be casued by other things such an exhaust leak.

Posted: Wed Nov 25, 2009 12:47 pm
by BillyG
Agree with Johnny...if all is in order with the carbs...then (1) look at the "J" pipes coming off the head. On the 2002 engine, they are a press fit, if they are loose and sucking air on deceleration...you'll get a pop, pop. (2) Check the union nut at the J-pipe/muffler junction, if loose you'll get the same.

Loosen hanger clamp on J-pipe (need to remove cylinder bar on left side) and tap pipe in with a hammer/mallet at the apex of the 90 bend to seat. If you so desire you may, remove pipe and slather each end with red RTV sealant (both pipe/cylinder boss and muffler) and then tap the pipe in.

Just grab the J-pipe when cold and see if you can move/rattle it. If so, do the above. If not, you don't have the carbs set up correctly or have a problem in the innards of the offending carb.

The idle mixture screw (forward and underneath the carb.) only affects the first 1/4 of throttle...so if you are coming off throttle when popping occurs...you problem is not with the idle circuit.

Last, never trust the advice given by a guy wearing latex gloves in a maintenance video. :P

Posted: Wed Nov 25, 2009 1:58 pm
by JohnBG
Also check your valve tappet clearances. An overly tight exahust valve may exhibit the same symptom.

Posted: Wed Nov 25, 2009 10:25 pm
by ryrypizza
Wow, thanks for all the input! I have quite a bit of reading and tinkering to do now.

Thanks!

Posted: Sat Nov 28, 2009 4:50 pm
by Overkill
nemec wrote:don´t have money? use this! :)
I have the same and it work.
http://www.motoguzziclub.co.uk/tech/how ... ometer.asp
Image

than I ordered colortune plug on ebay - it seems good - it is 14mm version - this is good site about it + videos -
http://www.gadgetjq.com/ctune.htm

and finally - I think here you can find good hints for tuning/setting your carb - CV carb tuning procedures -
http://www.factorypro.com/tech_tuning_p ... gines.html

and Harley forum about cv carbs -
http://www.hdtalking.com/fuel_and_carb_related_issues/

and here is russian video of synchronization -


and here is some bmw with "oil" manometr -
I made one like this but put motor oil in it. My thinking being that if things got a bit out of hand I would rather have oil sucked into engine than water. :moto: The advice I got suggested using a yard stick and filling tubing with oil to about the 27 inch level. :fart:

Posted: Sat Dec 05, 2009 8:53 pm
by isldtime
nemec wrote:don´t have money? use this! :)
I have the same and it work.
http://www.motoguzziclub.co.uk/tech/how ... ometer.asp
Image

than I ordered colortune plug on ebay - it seems good - it is 14mm version - this is good site about it + videos -
http://www.gadgetjq.com/ctune.htm

and finally - I think here you can find good hints for tuning/setting your carb - CV carb tuning procedures -
http://www.factorypro.com/tech_tuning_p ... gines.html

and Harley forum about cv carbs -
http://www.hdtalking.com/fuel_and_carb_related_issues/

and here is russian video of synchronization -


and here is some bmw with "oil" manometr -
Built That Manometer last weekend but used Marvel Mystery Oil as the fluid. Finally got a chance to use it today after riding home from work.
Now I thought I had the carbs fairly well set until I started it up,damnear sucked the oil into the rt. carb.
Got it all balanced nice.
Note: both idle screw and cable adjustments are VERY sensitive so only go a tiny bit at a time.
It is much smoother now and will do a cold start check tomorrow.
I still need to re-jet so this was just practice!

Posted: Sat Dec 05, 2009 10:43 pm
by BillyG
Re-jetting does not require resync'ing.

Posted: Sat Dec 05, 2009 10:59 pm
by isldtime
BillyG wrote:Re-jetting does not require resync'ing.

Yea, I know,but just got to go thru the steps.
I'm That nutty....