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 .
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-
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Not easy to see, but there are 'Tide Marks' in the bore where the water level line is eroded into the Bore wall-
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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-
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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-
DSC00906.JPG 98.39KB 7 downloads The finished Mandrel-
DSC00909.JPG 42.59KB 6 downloads ....and the new plate machined and just needs removing and de burring-
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The first attempt showed the plate was just 0.003" under Bore size-
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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'-
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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-
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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.