What does this guy mean by this pilot jet not working with CV Carbs?

Question

Alright, I had asked you guys last night if this would work for my 1982 Honda Nighthawk 650 (CB650SC) and you all said yes:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&sspagename=STRK:MEWNX:IT&viewitem=&item=140253156861

But when I asked him, he said that it would not work because I have CV carbs. Is there a difference that I have to look for? I DO have Keihen carbs, so I'm not sure what he means. Do you think they would work?

Here is my bike on bikebandit.com:

http://www.bikebandit.com/houseofmotorcycles/honda-motorcycle-cb650sc-nighthawk-650-1982/o/m1980

Thanks again Yahoo answers!

Answer 1

No, the jets on Ebay wont work.

They are for different model Keihin Carbs

The Ebay jets are  Kehin STYLE 424-21,,,they're way too long.

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You need Style  424-26,,,,they are almost the same,,except Shorter.

Here's some info,,,,

FORGET trying to find a source that shows you Specifically which jet to use.

Almost everything you'll find is either Unclear or contradictory.

You can CONTACT  a couple places which distribute/supply Carbs & Parts and they can tell you.

Here you can see the -21 & -26 side by side.

The focal distance differennce makes them appear different sizes,,,,but LENGTH is the actual difference

http://www.sudco.com/keihin_pj.html#26

SUDCO is also the place to contact for Tech Assistance & Info.

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Another good source is

http://www.motorcyclecarbs.com/Keihin_Pi...

http://www.motorcyclecarbs.com/CARBURETO...

Note the price of that carb kit

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Here's "same" carb kit for $20 each.

Shipping for 4 to my address is $6 via USPS

Thats a very good price.

http://www.z1enterprises.com/detail.aspx...

Most places want near $20 for Just the float valve

At your bike's age,,it's an idea worth considering to go ahead and put a kit in all 4

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If you are confident in the overall condition of the carbs & want to change Just the Pilot Jets,,,

I'd suggest installing #38 instead of #35.

Or,,if You have aftermarket air filters,,,or exhaust,,,,use #40

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Original Honda Part # 99103-GY6-0350

Superceded Format to Current # 99103GY60350.

Honda also sells #38's ,,,,

"same" part number,but ending in ---0380

That jet is standard in

1982 and some '83

CB 550 SC,CB650 SC ,CB750F,CB750SC ,CB900F,,CB1000C,,,CBX1000

And,CH150 scooters

Good Luck,,hope that helps

Answer 2

CV = Constant Velocity and pilot is like a primary jet in a Q-jet (on a car). So only a couple of things comes to mind, is plugged or to lean, not enough fuel and if that is the case it is a easy fix. If it's lean go 1 or 2 sizes up for a richer fuel mixture. If plugged, just replace the one or ones that are plugged.

Answer 3

http://battlescooter.com/1.html explains old style CV or constant velocity carbs, before electronic fuel control. Its a style of carb, not a brand. his carbs are computer controlled. so hes saying this isnt the jet for the old style manually adjusted cv carb.

Answer 4

To determine if you need larger pilot jets is simple.. If your bike needs lots of choke to start, and it needs the choke to warm up properly, and when it warms up the idle is high, then you may need larger pilot jets. This is the sort of symtom than can show up when you fit an after market exhaust system.

Answer 5

Constant velocity carbs differ from throttle slide carbs in that with the latter, the throttle cable is connected directly to the throttle slide, the thing that opens up to let more air into the engine.  CV carbs have a throttle slide, but the throttle cable is instead connected to a throttle butterfly.  The big round thing on the top of CV carbs is a rubber diaphram with a spring.  The spring tries to force the throttle slide down, closing the throttle.  Meanwhile, there's a orfice connected to the low pressure area behind the butterfly that goes to the area above the rubber diaphram, pulling it up, opening the throttle.

Constant velocity comes from the fact that when you whack the throttle open on throttle slide carbs, you can drop the vacuum so much that the engine bogs down and nearly dies.  With CV carbs, the spring keeps the slide down enough that the vacuum never drops so low that the engine will bog.  Whack a CV open and the engine will accellerate without hesitation.

The pilot jet is simply the jet that control the fuel mix during idle (0-1/8 throttle opening).  The main jet controls the fuel flow at wide open throttle (3/4 to fully open) while the jet needle reduces the flow through the main jet at throttle openings in between.