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Old 08-13-2008, 04:28 AM   #1 (permalink)
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TC and EVO 40mm CV carb. differences

Does anyone know if the vacuum piston (slide) and the float bowl are the same between the EVO and TC Keihin 40mm CV carbs? Other than the jets are the two 40mm carbs the same?? What about the accelerator pump capacity, & the pump nozzle internal passages. In other words does the accelerator pump deliver the same quantity of fuel for the same plunger stroke, between the 2 carbs. The only visual difference I can see is the EVO CV float bowl has a drain screw and drain hose fittng. Does anyone have access to cross reference the part numbers between the EVO and TC vacuum piston and float bowls?
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Old 08-13-2008, 10:50 AM   #2 (permalink)
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have you tried asking the dealer? they may know the answer or be able to cross reference the numbers...
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Old 08-14-2008, 02:20 PM   #3 (permalink)
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the CV slide on my 04 bike ends in -88 so I am guessing not a whole lot different. the epa has stepped in a prevented from letting the overflow out the bowl hit the ground so that is why the bowls/vent is diff.
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Old 08-14-2008, 11:44 PM   #4 (permalink)
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Quote:
Originally Posted by Tech23 View Post
Does anyone know if the vacuum piston (slide) and the float bowl are the same between the EVO and TC Keihin 40mm CV carbs? Other than the jets are the two 40mm carbs the same?? What about the accelerator pump capacity, & the pump nozzle internal passages. In other words does the accelerator pump deliver the same quantity of fuel for the same plunger stroke, between the 2 carbs. The only visual difference I can see is the EVO CV float bowl has a drain screw and drain hose fittng. Does anyone have access to cross reference the part numbers between the EVO and TC vacuum piston and float bowls?
Im sure there is minor difference....but 95 % is the same...
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Old 08-15-2008, 02:27 AM   #5 (permalink)
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Quote:
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Im sure there is minor difference....but 95 % is the same...
Steve
Thanks Steve, the slide is the same. The float bowl, because of the differences (the bowl drain) of course is a different part number. It appears that the carbs are essentially the same other than the jetting (and possibly the air bleed orifices).

The reason I wanted to know was; when I installed stage 1 on my Wide Glide, I followed the dynojet kit instructions to the letter. Which means I drilled the slide vacuum passage to 1/8" with the supplied drill bit. Well I have been reading that some Tech's prefer not to drill the vacumm passage in the slide and reuse the stock slide spring, rather than using the lighter spring in the dynojet kit. They say that under certain conditions (cold weather or low RPM) when the throttle is rolled on the slide can rise to quickly causing a lean condition and a pop back through the carb. My bike will pop back through the carb on occasion. I happen to have an EVO carb I picked up real cheap in PA at a swap meet. I thought if the slide is the same, just transplant it into my carb (along with the stock slide spring)to see if it remedies my symtom. Rather than spend money for something that may not cure the symtom. (I still am considering a Mikuni HSR 42 Easy kit). After digging through boxes to locate the EVO carb.....I disassemble the thing only to find the slide has also been drilled. I also found it had an adjustable jet needle WITH shims under the clip WTF??? Thats what you get at a swap meet.

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Old 08-15-2008, 11:50 PM   #6 (permalink)
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The EVO & TC CV diffs are also the acc pump has 2 0-rings on the TC carb
Evo have only 1

Additional bleeds IN the bowl (actually) 1 additional bleed.

Slides are the same, acc pump diaphrams are same as S&S E

I never drill to .125 any more.. Works ok, except while cruising say 2 up, & ya want to pass it just is flat on power...

I do drill em to just under .100 & that still gives ya the Zip & the roll-on ummph to pass easily !!

Best of both IMO..

IMO about dyno-jet kits thay just add too much fuel, which washes the cylinder wall oils off & causes premature wear.
Yes adjusting the needle will lean it out but then it doesn't run as good as stock did..

I have a select amount of HD needles & jets & get really good results just doing that !!! Plus great mileage as well...
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Old 08-15-2008, 11:59 PM   #7 (permalink)
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Tech23-

You don't need to disassemble a CV to tell if the slide is drilled (molested)

Just turn carb upside down & push open the slide & look at the hole behind the needle.. That's all..

That's probably why U got the Penna. CV cheep..

I do CV's & it is getting harder to find unmolested cores anymore at a decent price...

"I also found it had an adjustable jet needle WITH shims under the clip WTF???"

That could have a dyno-junk kit in it too.. They do have adj needles. So does Yost power Tubes.
Simple to tell which, the emulsion tube for dyno-junk has only 2 bleed holes each side.

Yost has many more & a tube in the center

HD emulsion tubes have many holes & regular center..
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Old 08-16-2008, 02:46 AM   #8 (permalink)
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Quote:
Originally Posted by Buddy Seat View Post
Tech23-

You don't need to disassemble a CV to tell if the slide is drilled (molested)

Just turn carb upside down & push open the slide & look at the hole behind the needle.. That's all..

That's probably why U got the Penna. CV cheep..

I do CV's & it is getting harder to find unmolested cores anymore at a decent price...

"I also found it had an adjustable jet needle WITH shims under the clip WTF???"



That could have a dyno-junk kit in it too.. They do have adj needles. So does Yost power Tubes.
Simple to tell which, the emulsion tube for dyno-junk has only 2 bleed holes each side.

Yost has many more & a tube in the center

HD emulsion tubes have many holes & regular center..
Buddy Seat....Thanks for the info. Does the info. in my post sound correct as to a possible cause of my occasional pop through the carb.? I am happy with the jetting, the bike runs fine. I am only trying to address this occasional pop symptom. Do you know what the Dealer Techs. "prefer" to do to the CV carb for stage one? Meaning the carb. changes that produce the best results.

Also...I know you say you do CV carburetors but,..... do have any experience with the Mikuni HSR 42 flat slide?

Last edited by Tech23; 10-21-2008 at 12:30 AM.
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Old 08-17-2008, 12:58 AM   #9 (permalink)
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Tech23-

Yes what you've described can happen, might just need a 1/4 turn out more on idle-mix.. Or the oem spring.

Yes the 'stealer techs' prefer to add dyno-junk kits in the carbs..
They must have one hell of a mark up on those kits, cause that's all I see them pushing.. I have a bag full of them, I remove them & fix the carbs properly..

And I still do NOT agree that the dyno-junk is the best choice for motor longevity, performance & mileage.

My experiences with Miki's is removing them...

They seem to be a good carb, just not my choice..
PS: You should NOT have to adjust air/fuel mix every time you start a mikuni bike cold...
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Old 08-17-2008, 11:41 PM   #10 (permalink)
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Miki does use the CV enrichener cable.
But Miki also has a stub hanging out for air/fuel mixture adjustments.. Ask anyone running a Miki. They seem to be always adjusting it as it warms up (EACH TIME).........

for CV tuning look here: http://www.nightrider.com/biketech/carbadjust.htm
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Old 08-18-2008, 02:23 AM   #11 (permalink)
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Quote:
Originally Posted by Buddy Seat View Post
Miki does use the CV enrichener cable.
But Miki also has a stub hanging out for air/fuel mixture adjustments.. Ask anyone running a Miki. They seem to be always adjusting it as it warms up (EACH TIME).........

for CV tuning look here: http://www.nightrider.com/biketech/carbadjust.htm

Buddy Seat, that stub is the idle speed screw on the HSR, not the mixture screw. You should NEVER adust the idle mixture while the engine is cold, on any engine or carburetor. My bike idles low when cold and idles faster when it is up to operating temperature. I leave it alone because the idle is correct when warm. When cold I take it off choke ASAP and lock down the throttle friction screw.

The nightrider CV carb modification write up recommends drilling the slide to 1/8" as I have already done.

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Last edited by Tech23; 08-18-2008 at 05:14 PM.
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Old 08-19-2008, 12:26 AM   #12 (permalink)
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As I previously stated: "My experiences with Miki's is removing them"....


OK, glad you got everything sorted out..
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Old 08-19-2008, 05:14 AM   #13 (permalink)
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Tech23, the vacuum pistons are the same from 88/06 you can buy them in the DRAG fatboook $42.00
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Old 08-19-2008, 05:26 AM   #14 (permalink)
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Buddy Seat, do you know where I can get the CV jet sizes 167.5/172.5, #44 pilot?
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Old 10-19-2008, 01:53 AM   #15 (permalink)
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Quote:
Originally Posted by Buddy Seat View Post
The EVO & TC CV diffs are also the acc pump has 2 0-rings on the TC carb
Evo have only 1

Additional bleeds IN the bowl (actually) 1 additional bleed.

Slides are the same, acc pump diaphrams are same as S&S E

I never drill to .125 any more.. Works ok, except while cruising say 2 up, & ya want to pass it just is flat on power...

I do drill em to just under .100 & that still gives ya the Zip & the roll-on ummph to pass easily !!

Best of both IMO..

IMO about dyno-jet kits thay just add too much fuel, which washes the cylinder wall oils off & causes premature wear.
Yes adjusting the needle will lean it out but then it doesn't run as good as stock did..

I have a select amount of HD needles & jets & get really good results just doing that !!! Plus great mileage as well...
Buddy seat, I dont like dyno junk kits either, but how can one
'"add too much fuel, which washes the cylinder wall oils off & causes premature wear", as you state? the fuel is ignited when the piston is basically TDC. Wives tale. OMG dont use synthetic oil, it causes "bearing skate"
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