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New life for an old #26 Kohler Carb


20 posts in this topic

ID: 1   Posted

The reasons why I decided to fix this Carb up are many really, deciding to put the progress report on here is that it may help others to understand why their Tired worn Carb is misbehaving or may require bits that aren't available anymore....so there may be hope yet if I can help and make a few bits. 

 

I see Used Carbs for sale and sell for over £50.00 (in UK) !. The buyer probably gets a Carb that is just as bad or worn as their old one and requires a full clean and gaskets anyway, so they still end up paying £80 incl postage etc for it.

 

I know not everyone is able to, or has the equipment etc. to make obsolete parts, or indeed wonder if it is really worth it?....... Maybe just go out and buy a new/used Carb that will fit and move on.....    For me, I have to take it apart and see if I can repair it, just because I am able to. 

 

I don't think a picture of a dirty, damaged and worn out Carb that is used mainly on 10 & 12hp Kohlers is necessary on here is it?, there's loads out there to see :hide: . 

I also don't need to go into the workings of it, as all that is available elsewhere e.g. Mr Miller's Tractorpulling site, although there are a few minor points I can't agree with.

 

So, here we go, and we start with a need to identify it's condition after a good clean, an inspection and then take some fairly critical measurements of some dimensions. This Carb was left outside for several years and had filled with water. It was attached to my '81'Engine that was fully rebuilt for my '74' C-120 Project.

Lots of wear and remaining evidence of rust damage to the Throttle Shaft/Plate and the Bore itself- 

 

post-3520-0-35462700-1377291874_thumb.jp

 

Not easy to see, but there are 'Tide Marks' in the bore where the water level line is eroded into the Bore wall-

 

post-3520-0-23171900-1377292145_thumb.jp

post-3520-0-53913600-1377292174_thumb.jp

 

Plan is not to re-bore this yet if it's not necessary.

 

So I need to make a new Throttle Plate and Shaft.

With the Pivot/Stop bracket removed from the old Shaft by careful filing, the bracket damage had to be straightened out. The condition of the Ball Pivot is ok (0.003" under 1/4" dia ). The old worn Banana Shaped Shaft is junk

Took the measurements to reproduce the angle of the Throttle plate when in the fully closed position. A bit of a challenge and not totally accurate, but you have to start somewhere-

 

post-3520-0-33449400-1377292834_thumb.jp

 

Armed with these Dims, I produced a mandrel that will fit in the Lathe Chuck and hold a steel plate at the correct angle while it was machined down to the Bore diameter. The mandrel is a 4.1/2 inch stub of 3/4" dia Silver Steel (Drill Rod) with a Brass Head pressed/bonded on. It was then turned down to exactly 1.0000" so I can use that dia as a reference point .

It was then bolted down on a Vertical Slide to machine the angled face. here it is with the face part machined-

post-3520-0-64980800-1377294181_thumb.jp     The finished Mandrel-

 

post-3520-0-21819000-1377294266_thumb.jp     ....and the new plate machined and just needs removing and de burring-

 

post-3520-0-40537200-1377294515_thumb.jp 

 

The first attempt showed the plate was just 0.003" under Bore size-

 

post-3520-0-72846300-1377294655_thumb.jp

 

Not bad considering I had to measure the bore using an old pair of Inside Callipers and then use a Vernier to measure the Calliper setting. 

The bore is also tapered !!. So I may run it in the Lathe and shave off a few thou to parallel and turn up another Plate to fit.   

 

Throttle Shaft was made up from 1/4" Silver Steel (Drill Rod) as it is ground exactly to 0.2500" dia. A very nice fit in the lower Carb Shaft Bush. The original Shaft is mild steel and 0.002" under size on unworn areas, so a bit of slack there to start with when new.

Used the new to me Mill/Drill for this and I like to keep a pictorial record of work holding 'Set Ups'-

post-3520-0-64683800-1377295334_thumb.jp 

 

And the partly finished shaft against the old one. note the lower Bushing end is longer, this is because I machined less length out of the shaft for the Plate. The original had more removed than needed and reduced the bearing face area (could be a standard Shaft for several size Carbs). The 'first attempt' Plate and the old one, together with a super clean  'Fuel Tight' Float-

 

post-3520-0-77463400-1377295888_thumb.jp

 

This is as far as I have got by tonight. Still have a few adjustments to make on the 'Masheeeens' and permanently fit the LED Lights to them.

Next session will be sorting out Bushings, fixing Shaft length, finishing and Plate install....maybe next week.

 

Regards.    

     

 

  

 

 

 

 

 

 

 

  

  

  

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ID: 2   Posted

great work I have made quite a few new throttle shafts and bushings  so far for my carbs have not made a throttle plates yet as I sand blast them and get the old ones  replated

awesome!!!!

 

Brian

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ID: 3   Posted

great work I have made quite a few new throttle shafts and bushings  so far for my carbs have not made a throttle plates yet as I sand blast them and get the old ones  re plated awesome!!!!. Brian

Brian, Thanks. I know about your awesome work in Stainless, but I just read your profile and seen your profession :bow-blue: .....I missed my vocation in life (also should have been in engineering), so just a hobby for me.

........................... So if I may, a question. Do you peen over the top of the Shafts to the Bracket/Stop Plates or Drill n Tap for a retaining screw ?. I'm aware Kohler used both methods.

Regards.

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ID: 4   Posted

I drill and tap for 4-40 washer and screw

I think that comes from the machinists thought that I might have to take this apart some day

 

Brian

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ID: 5   Posted

Thanks , I was hoping you'd say that.  I don't have a Plater around here anymore either, so I will 'Blue' the parts and quench in oil to give them a bit of protection.

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ID: 6   Posted

Amazing work Richard, just amazing :bow-blue: :bow-blue:  

 

So when are you going to start taking orders for carb rebuilds? :D

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ID: 7   Posted

H Ian,  Glad to see you gracing local shows with your presence and the Beast.  

Not sure I want to rebuild them. Too much work cleaning them (outside especially) before you can work on them.

May be produce parts that are either expensive to obtain in UK, or are unobtainable.

Not geared up for, or familiar with the 1/2" bore Kohlers or Walbro (except for the series 1).  But if anyone has an old small bore, a size 28 or 30 Carb they can donate, I could extend the range of parts I'm able to make.

 

Made some more progress on this one, so I'll put some more pics up later hopefully. Keep forgetting to take pics .

Regards

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ID: 8   Posted

Spent a bit of time setting up for making the Screws. Having made up a few Jigs, Decided to make 4 at a time in 2 stages. Turn down, thread and part off in the small Lathe, then set them (4) into a jig for milling the Slot in the head. Here's 2 of them finished for example-

 

post-3520-0-08213500-1377804570_thumb.jp

 

Finished the Throttle Shaft and fixed the Top Bracket to it with a screw as discussed previously. Shaft was such a good fit , that it hardly needed the top bushing fitted, but I pressed one in anyway. It also has a thin fibre washer impregnated with a smear of Copper Grease between the Bushing and the Top Bracket as an additional seal. 

 

Provided a degree of anti corrosion to the new Plate by 'Blueing' , a form of heat treatment and Oil quenching to fix a particular colour to the metal. And yes , I just had to pretty it up by doing some miniature 'Engine Turning' first.

 

All fitted and finished at the engine end of the Carb-

 

post-3520-0-48004600-1377805025_thumb.jp

 

Next job is to sort a small amount of wear in the Choke Shaft. Most of the wear is in the bores of the Carb and not on the Shaft, so I'm going to re-bore both to 5/16" and make new bushes.

The lever side will have an extended bushing to support the Shaft better, they will be fitted, then carefully drilled and tapped No 10 - 32  following the existing threaded holes so the Air Filter Body Screws don't interfere and the Choke Open 'Ball Locator' and spring can be fitted easily.

I believe the old Kohler Bushing Kit (NLA?) had 2 short bushes for each side leaving clearance for the screws and sprung ball locator

Here's the set up ready for enlarging the shaft bores-

 

post-3520-0-02463200-1377806046_thumb.jp

 

Take's a while to secure everything down and retain Shaft bore alignment with the Machine's Spindle, but all ready to go now.

 

Regards

 

 

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ID: 9   Posted

.  But if anyone has an old small bore, a size 28 or 30 Carb they can donate, I could extend the range of parts I'm able to make.

 

 

I might be able to help you out Richard, I will have a look on the rack when I get in the shack this morning.

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ID: 10   Posted

 

 

I might be able to help you out Richard, I will have a look on the rack when I get in the shack this morning.

 

Thanks Ian. 

                   I apologise to people who only know about metric sizes, but this being an American Carb on an American Engine for an American Tractor, it's only fitting that it stays Imperial in all aspects (plus the fact that most of my Tooling is Imperial due to my age and inheriting some the Tooling) 

.

The Choke end has had the treatment,  drilled out 19/64" and finish reamed 5/16" -

 

post-3520-0-17442700-1377911191_thumb.jp

 

Made up the Phosphor Bronze Bushes, pressed them in and finished as mentioned earlier. 

I reckon the extended Bushing on the Lever side should virtually eliminate wear and no chance of any dirty unfiltered air getting in -

 

post-3520-0-49682700-1377911583_thumb.jp

 

With another clean out and all the other bits like Float and Valve done, there is only the light 'Peening Over' of the Plate Screws and it's done. A virtually new Carb in all but age.

 

The new Throttle Shaft and Plate will now allow me to set the idle speed (mechanically) so that the Plate is slightly open (as it should be) to obtain the correct idle speed.

With a worn Shaft and bad Plate fit in the Bore, it means that the Plate will be closed up against the Carb bore, as the air is getting in around the Plate and the Shaft.

Add vibration to this and the wear, poor running and performance just gets worse. Also difficult to get the mixtures right.

      

I shall bolt this onto my 72 Raider 12 to set it up and it will allow me check it's Carb while it's off.

  

So I'll have 3 good Carbs tuned for 2 12 hp Engines !.  Hmmm, I may just sell one.

 

Regards

 

    

 

 

 

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ID: 11   Posted

Looking great Richard!

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ID: 12   Posted

Sorry Richard, I only have 26's no 28's or 30's.

 

That carb looks stunning, it should be in a lit display case :)

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ID: 13   Posted

wow that carb looks really good Richard...

and nice fab skils to.. :)

Btw my brother has a worn out #30 carb on his 16 hp engine.. might ship it to you for an overhaul lol

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ID: 14   Posted

Looking great Richard!

Hi mark, thanks, hope all's well.

 

Sorry Richard, I only have 26's no 28's or 30's.  That carb looks stunning, it should be in a lit display case :)

No problem Ian, only just a chance ask really. I'm sure I'll get my mitts on some one day. Ta !, happy with the way it turned out... gonna use it or sell it, not sure yet. 

 

wow that carb looks really good Richard...and nice fab skils to.. :) Btw my brother has a worn out #30 carb on his 16 hp engine.. might ship it to you for an overhaul lol

Hi Lars, Thanks , hope all is ok for you. If I can find a #30 over here, , maybe I could make the parts and send them over, could be cheaper.

I'm moving on to the next challenge now, here is an idea of the set up....... You should know this one Lars :eusa-whistle:  :hide:  :silence:

 

post-3520-0-57754100-1378065168_thumb.jp

 

And a clue..... the large 6" dia Chuck is set to hold a diameter of 1 1/2" (38mm) and a Slitting Saw  ready to do the cutting ?

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ID: 15   Posted

Bet you're setting up to cut those front rims down Richard.    :popcorn:

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ID: 16   Posted

Richard, really detailed work as usual.....

perfect compliment to your high level of detail on your tractors.

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ID: 17   Posted

Thinking of offering a wheel narrowing service now are we Richard?  :ychain::laughing-rofl::D

 

Your method of cutting wheels is a bit more scientific than my way.  :D

 

P4150142.jpg

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ID: 18   Posted

No Flies on you Guys is there :thumbs: .  Yep ,  got some trimming work to do on this one.

Ian ! , love the way your 'Lateral Thinking' comes up with a way of doing something with the tools you have around you :bow-blue: . 

Yep!, got some trimming to do on this-

 

post-3520-0-07603400-1378144463_thumb.jp

 

.............. but I shall bump the old '74 C-120 Update' thread to cover this bit ('cause the Carb's done) as these Wheels are for that Tractor.

 

 

Regards.

 

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ID: 19   Posted

Great carb rebuild.

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ID: 20   Posted

WOW !! You do really great work Richard. I am always amazed at your skills !!    :handgestures-thumbup:

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