[rabarone63]

Hi all, I have a 1973 646 with a VD 75 Carb on it. The top of the carb is fairly warped and leaks, I've replaced the gasket with no improvement. Is there an after market replacement carb? Or can I use a later model carb? Ebay has New Carburetor Carb For ONAN NOS B48G B48M P216G P218G P220G Replace 146-0496 146-0414 146-0479. It looks like it might work but not sure about the throttle linkage. Any help would be greatly appreciated.

 

[metalguy]

Mine hasthe same issue. I ended up sealing around the top with a gas resistant sealant. Worked pretty well. I had thought of going with a different cab for this very reason. That, and it is super vague as to how to adjust it. -------Metalguy

 

[sdunt]

If you can find them there was a carb adapter that would mount a Nikki carb on a cck. Since the adapters are like hens teeth I made my own, but have not got it installed on the running engine.

It also requires modified air filter.

 

[rabarone63]

Thanks for the replay, do you have a part for the NikKi Carb?

 

[rabarone63]

Part number?

 

[rabarone63]

Thanks, I did the same and its working ok but would still like to try a new carb.

 

[sdunt]

Parts Needed: from: https://www.mytractorforum.com/threads/ccka-carburetor-upgrade.243896/

1 Nikki 6100 Series Carb
2 Onan 154-1977 adapters (available from Onan parts and Boomer)

2 154-0733 Gaskets (Nikki to to adapter)
1 141-0078 Gasket (adapter to CCKA manifold)
2 countersink head bolts (1/4-20) for mounting to manifold 1.5" long although you will
probably have to shorten them.
To mount the Nikki you need 2 adapters, one stacked on top of the other. If you try to
use only one, the carb will hit the points box (see picture).
Step 1: Countersink the non threaded holes on one of the adapters.
Step 2: Mount both adapters to the Nikki using 2 gaskets and the 2 bolts.

OR.. If you're able to machine things:
I used a 1" thick chunk of aluminum bar stock and drilled 2 different 'bolt circles" in to it.

The CCK Carb (VD) flange is a 1.825" bolt pattern and uses 1/4 - 20 bolts

Nikki (146-0496) Carb flange is 2.357" bolt pattern with 5/16 - 18 bolts

Adapter needs to be 1" thick with Center bore minimum of 1.065" (the butterfly of the Nikki swings down into the throat.)

The alignment of the 2 different sets of holes are 30 Degrees apart.
(I have a DRO on my milling machine that will do Bolt Circle spacing for me. So I just punched in the dimensions and it laid out where to drill.)

The 2.357" bolt circle holes were drilled at -15 degrees & +165 degrees as through holes for 5/16" bolts. Because I used 5/16"-18 x 1 Cap head screws to attach the adapter to Nikki carb, These holes were counter bored at 0.500" diam & 0.325" deep


Then the 1.825" Bolt circle holes were drilled at +15 Degrees & +195 degrees sized to be tapped 1/4" - 20

(and yes you need to cut some of those angles on the block so it will clear the points box)

Air filter mounts are #10-32 bolts on 2.20" C to C spacing.
Working out the Circumscribed circle of an equilateral triangle = 2.54" bolt Circle. Drill 3 - 3/16" diameter holes on 2.54" bolt pattern, 1st @ 90 Degrees, last at 330 Degrees. (sorry don't have in my notes how much you have to open up the plate to make it fit)



I put an o'ring around the neck of the Nikki and it seals the air cleaner to the Carb.

Choke bracket made from 3/4" wide flat - 2 3/4" long
drill 2 - 3/16 clearance holes 1.0" on Center in section narrowed to 1/2" for 1 1/4" long

 

[metalguy]

This is awesome. I just happen to have an Onan from my 446 that is worn out, but the carb assembly I just rebuilt last year, and worked perfect. I'll make an adapter, and use that. The water jet will make very short work of it. -----Metalguy

 

[sdunt]

Sure old Buddy.. Rub it in.. the Water Jet...

The water jet will make very short work of it. -----Metalguy

Back here in the stone age I still have to use a metal cutting bandsaw and a manually operated milling machine.. Which for me is a lot of fun.. I spend too much time in front of a computer to spend time creating the part layout in CAD and then sending that to the machine and just watching it work.

'Course would be really nice to have access to a CNC water jet cutting system.. You are lucky. Please post pictures of your creation..

 

[metalguy]

Ok, I will piggyback on your measurements, and get it done. The software for it makes bolt patterns easy, and offsets too. I can even have it "drill" the holes to tap drill size, so I can even be lazy that way. I can even cut my gaskets with it while I am at it. ------Metalguy

 

[rabarone63]

Thank you, very helpful. I may try to machine one.

 

[metalguy]

I made my adapter, but made it for the carb off my old 16 hp Onan from my 1973 446 (B43?). anyway, it works, and is 1" thick, but the stock air filter housing for this carb now has the hood resting on it. I may have to mod it to fit, but I'll have to see what can be done for that. Works well on the CCK-A. -----Metalguy

 

[sdunt]

Pictures??

Did you use the Air filter from the CCK and the VD carb? the one that clamps on? Or did you use the air filter from the B series?

For the clamp on filter to work you have to modify it and cut out the center so you can bolt it down directly to the carb:

My measurements make that the same height of the existing VD-65 with the clamp on filter. Of course on my stock 1973 646 with the Mesh hood, the hood sits right on top of the air filter orginally.

I made my adapter, but made it for the carb off my old 16 hp Onan from my 1973 446 (B43?). anyway, it works, and is 1" thick, but the stock air filter housing for this carb now has the hood resting on it. I may have to mod it to fit, but I'll have to see what can be done for that. Works well on the CCK-A. -----Metalguy

 

[sdunt]

To Finish off documenting this.. Since I got the NEW short block installed and putting the Nikki carb on it was part of that process:

Governor Linkage, pretty straight forward:

On the right in black is the points box for a CCKa. The aluminum right to the left of it is the adapter block so you can get to the low speed mixture screw right over the points box now. (Nikki's - at least this one does not have a high speed adjustment screw.)

The round silver thing on the extreme left with hose is the crankcase vent and hose to the air filter.

Re used the original governor rod, just adjusted length. I did use the rod end clip you see in the photo from a 446 I scrapped, because the clip used on CCKa with a VD Carb, comes top down on the rof, instead of bottom up.. I have also seen these governor rods with cotter pins in them. So there are options.

Other side or carb setup with choke control setup:

Home made bracket for the choke described above. This particular 3rd party carb had a 90 elbow on the fuel input, so I had to take that out, drill and tap it 1/4 NPT and put a straight fuel nipple in it.

New CCK runs very well with this new carb.

My experience only, you mileage may vary.