Hi a quick question took the plunge and got a beautiful Road King (which replaced my Vulcan), it ran perfectly all summer (2005 custom), but when it got below 40F (Montreal...its cold already) it began sputtering and backfiring.I checked the plugs and the rear cylinder is running too rich, black sooty while the front plug is perfect, I replaced them with new ones and the same thing happened. After running about 20 minutes it clears up completely! The bike is carburetored and runs perfect except in cold weather. I plan to adjust the mixture by adding EZ flow (thumbscrew adjuster) this winter. but to your knowledge is there anything I can check or change that would make the rear cylinder run better? thanks for your expertise. Mike

 

BOYESEN TWINSHOT...simple swap, absolute killer CV40 mod, best money you'll spend!

- Machined to exact tolerances for improved performance/reliability
- Patented QUICKSHOT 3 technology for precise/consistent fuel metering (QS3 chamber completely fills with fuel, eliminating trapped air in system, for accelerated fuel delivery)
- 25% more fuel capacity plus added bleed capability allows for solid fuel delivery 100% of the time
- Dual Check Valves, new ball & spring system keeps fuel dirt from clogging system, second valve located at sprayer for immediate response of fuel spray
- "ON THE FLY" external leak jet adjuster maximizes fuel volume/duration of squirt for all conditions (turn out for hot days/high elevations - turn in to enrich for cold days/low elevations)
- Stainless plunger rod & 5% stiffer activation arm spring for consistent spray response
- Precisely angled Twin Hole Sprayer enhances fuel velocity/atomization for increased roll-on acceleration
- Removable main jet cap for quick access tuning
- Predictable, smooth, instant throttle response - similar to EFI
- Improved low end performance, quick cold starts, no more hesitation/bog/stalling/backfiring
- Boyesen Unconditional Guarantee - complete refund if not 100% satisfied

http://www.boyesen.com/twinshot-vtwin

http://www.hotbikeweb.com/tech/1004_...t/viewall.html

 

Interesting as my carbed RK runs just fine well into the 20's F with a stock CV and just some minor jetting. I have no help, sorry. Hopefully the Boyesen will solve your problem.

 

The CV is a great carb- as is- I've run than over 20 years with no need for any aftermarket add-on ( a few of which were absolute junk)

If you are SURE that you are getting proper mixture, then if the rear is sooted up perhaps you have an oiling or misfire problem

if the bike runs better when warm, check for intake leaks--- that is more likely. when the bike is running like crap, spray wd40 or even water ( narrow tube) at the manifold to head joint- if the idle picks up and smooths out- you've found the problem

make sure there is no water in the float bowl- there is a drain accessed with a screwdriver from between the cylinders- seen from the left side of the bike--- prepare to catch the draining fuel from the thin black tube.

the idle adjuster you reference is handy but does no magic the stock adjuster doesn't do with a screwdriver.

the best laid out CV carb tuning and modding info is at nightrider.com in the bike tech section.

I have set up my cv carbs ( many) using this method to great result.

MOST of the products sold for the carb are only useful to a rider who is familiar with function and tuning the circuits of the carb ...not the novice.

idle needle controls the amount of fuel added to the air at idle
low speed jet ( usually a .45) controls 1/8 to 1/4 of throttle ( idle circuit is still also adding fuel)
needle controls to about 3/4 throttle ( in conjunction with the main jet size and the other circuits are in operation as well)
Main Jet from 3/4 to full throttle-- again the low speed and idle circuits are still adding fuel to the air stream

the accel pump shoots gas at the carb throat from that little brass tube when the throttle is rapidly opened--- a few quick shots with this when starting can makes things sooty

are you using the enricher? ( it's not really a choke on these bikes)--- and giving it a couple minutes to warm up before starting off?


tailpipe smoke

white on acceleration: piston rings
white on decel: valve seals
Black--- over rich mixture---- (does this happen at all throttle settings or only some?)

if you end up opening the carb, the float bowl screws are tight and you may deform them when removing ( needle nose vise grips work to break them loose), replace with 4 mm allen heads and put some antiseize paste on the threads



Stay out from under those crumbly bridges, Mike

 

Believe that...'til ya try a TWINSHOT!

 

just the claim for compensation hot/cold turns me off the product.



( - "ON THE FLY" external leak jet adjuster maximizes fuel volume/duration of squirt for all conditions (turn out for hot days/high elevations - turn in to enrich for cold days/low elevations)

A properly operating CV carb is self adjusting for air density changes due to altitude or temperature

CV is "Constant Velocity" the air stream is keep at a constant velocity by the vertical sliding plunger

The CV is awesome, supporting motors over 100 HP--- tuning and mods require only $20 of parts and a pocket full of smarts--- no aftermarket add on will replace that

Mike

 

I was skeptical as well. Works as advertised!
Boyesen Unconditional Guarantee - complete refund if not 100% satisfied

 

many thanks for the info, I got the bike this spring and had absolutely no problems till it got cooler out, I changed the plugs and air cleaner and it ran better for a couple of weeks then the rear plug got black and sooty again. I am also changing the battery and spark plug cables but dont think they are the cause where is the enricher, how can I check it or adjust it?, thanks again

 

http://www.harley-performance.com/ha...arburetor.html