Author Topic: Clearing blocked carbs  (Read 221 times)

0 Members and 1 Guest are viewing this topic.

Offline martin1957

  • Forum member
  • Port Hacker
  • Posts: 1255
  • Age: 63
  • Location: Gillingham, Kent
Clearing blocked carbs
« on: July 07, 2021, 11:32:48 AM »
I have had a KH400 stood for 4 years with fuel in the tank and carbs.

I have taken the carbs off and cleaned them with ultrasonic and carb cleaner.

They are Mikuni VM24 and have a pressed in brass air bleed jet from the bell mouth to the main jet emulsion tube, and an angled drilling from the idle jet orifice to the engine inlet. There are no brass balls involved.

Both these holes were blocked. I have some stiff steel banjo strings that are 0.35mm diameter and these were too flexible to press into the jet and clear the blockages.

I bought a set of 20 tiny drills an a hand pin chuck. The drills range down to 0.3mm diameter. The 0.3mm went straight through and I was able to clear the holes after with the wire. I think the holes are about 0.4mm so there is no drilling of metal.

With a torch and eyeglass you can now see light through the jets.


These drills are highly recommended - I have the link if needed.

Not sure if these carb features are on RD carbs. I have smaller Yamahas, and they are not.
Retired Widowed Electronic Test Engineer (Avionics), Age 63, Owned P50, PC50, SS50z, YAS1, YDS7, RD350B till 1978, then KH400 from 2009 onwards. Have a fully restored YAS1 on the road, and an AT3. And now a Suzuki T125 Stinger to get fired up, with another Stinger in boxes....

Offline 5port

  • Club Member
  • Port Hacker
  • Posts: 9734
Re: Clearing blocked carbs
« Reply #1 on: July 07, 2021, 03:44:46 PM »
Good to hear that Martin! 
I had a bit of a look and I see KH400 listed with VM26, not VM24?  Also, no detail on the Air jet size.  Carb stamp KH4.

Does that make sense?  I found the details in "Carburetor Tuning - 3cyl.com".

Cheers

5port
5port

Offline martin1957

  • Forum member
  • Port Hacker
  • Posts: 1255
  • Age: 63
  • Location: Gillingham, Kent
Re: Clearing blocked carbs
« Reply #2 on: July 07, 2021, 05:31:46 PM »
Yes, its VM26.

The parts I am clearing are either fine drillings in the body alloy, or pressed in brass jets with no numbers. You cant remove them...

Ive never had carbs so stubbornly blocked before. I boiled them as well.........

I have checked airways in other carb before with Syringes full of water.

I have Mikuni downdrafts on my stingers (T125 Suzuki). These were the first downdrafts Mikuni ever made. Quite unusual......

Anyway, the KH should be firing up next week, weather permitting.
Retired Widowed Electronic Test Engineer (Avionics), Age 63, Owned P50, PC50, SS50z, YAS1, YDS7, RD350B till 1978, then KH400 from 2009 onwards. Have a fully restored YAS1 on the road, and an AT3. And now a Suzuki T125 Stinger to get fired up, with another Stinger in boxes....

Offline 5port

  • Club Member
  • Port Hacker
  • Posts: 9734
Re: Clearing blocked carbs
« Reply #3 on: July 07, 2021, 07:02:58 PM »
Yes, its VM26.

The parts I am clearing are either fine drillings in the body alloy, or pressed in brass jets with no numbers. You cant remove them...

Ive never had carbs so stubbornly blocked before. I boiled them as well.........

I have checked airways in other carb before with Syringes full of water.

I have Mikuni downdrafts on my stingers (T125 Suzuki). These were the first downdrafts Mikuni ever made. Quite unusual......

Anyway, the KH should be firing up next week, weather permitting.

Yes, sounds good!  :)  The VM26 on the KH400 is probably much like the VM28 on the RD, just a bespoke Kawasaki version.  The two features you describe of the Air corrector and the Pilot jet with the angled orifice are very similar, although the opening to the Air corrector was sealed at the front with a large brass ball and fed from a pipe to the airbox on 250/350/400's starting with the 250/350 521/522 models in 1975.
The Air corrector jets themselves are pressed-in and the size is given in RD specifications.  Also, that angled Orifice is very prone to blocking and partial blocking. It is worth making certain that it is clear.  The hard deposits can be corrosion or calcified dust.  It can be quite hard.
Cheers

5port 
5port