86 K5 Revving Problems. Maybe the needle?

[18thparadox]

I have an 86 K5 that seems to keeps wanting to go when in higher rpms. The bike is somewhat of a project at the moment and has no brakes, so the engine not wanting to stop is a bit scary lol. When I got the bike it had no carb needle. The carb is a Mikuni VM40SS as far as I know, what came stock. The stock needle is a 6j6-2 which I have learned no longer exists anywhere on this planet. I had purchased a slide, needle, and cable off of ebay, which was advertised as compatible with an 86. I think it was from a 38mm carb, the slide was too small. I took the needle out and used it anyways. Pretty certain its too small for the carb, and my question is will the needle being the wrong size cause the engine to rev like that? I've read other posts of people with the same issue, and I've repaired cracks in the air box duct with silicone, and put new Boysen reeds in. I cannot find ANYTHING about the VM40SS. Any list of Mikuni carbs excludes this one, for whatever reason. I've contacted Mikuni and they pointed me to a a guy that makes vintage needles but they gave me no specs for the thing.

Can I put a different carb on this bike and what one is recommended?

I have a problem with the overflow also. Not sure if the float level is wrong, or the float valve is bad. The valve was making a clicking noise the last time I rebuilt the carb.

Any help is greatly appreciated. Thanks!

[Goat]

I personally would put a 38 or 39mm Keihin pwk carb on it. That's what the newer ones run and they are easy to find parts for and easy to tune.

Sounds like the needle is too small and letting too much fuel in and revving because of it. Could also be a spec of dirt in there somewhere like the slide and not letting it close all the way.

[Friar-Tuck]

 I agree with Goat.
Unless you are restoring the bike and have to have OEM.  Here is the Keihin web site:
  http://www.keihin-us.com/am/index.php
If you click around a bit you can find the spec's & size of the 38 and 39mm PWK's.
Measure the inlet and outlet on your Mikuni and see what options are available that will fit your boot & intake against the measurements on the keihin site.

  The 39mm PWK is the most popular with KX & CR 500's
 The 38mm carbs will have a better throttle response, and the 39mm's will give you more top end.   
  There is also a 38mm PWM available without the throttle position sensor (F.I.)
  and there are two 38mm PWK's a standard version and an Air Stryker quad vent. 
 
 I don't know anything about a Mikuni or the larger Lectron Carbs Stewart and a few of the serious H.P. guys use.
  Tuck\o/

[bob larry]

Get it running and sell it.  Buy a 89-04 .  less headaches

$0.02

[18thparadox]

Thanks for the information! I will look into the 39mm Keihin pwk carb.

The bike isnt in too bad of shape, just some stuff missing and it needs a rebuild. I've never rebuilt a motor so I'm kind of hesitant to do it. Had bolts rattling off of the thing the last time I rode it 

Was thinking about getting it into decent shape and then selling it for something newer. Or maybe a truck so I can actually haul a dirtbike around haha