Thanks everyone :thumbsup: That silver is kinda hard to photo, It has a different (I think better) look in person. I was pretty relieved it came out alright, this was my first time doing a single stage paint with metallic in it and I was kinda sweating it. It actually laid down and covered thinner than some of the solid colors I have been spraying from the same brand/paint line (Nason Fulthane).
Re guarding the Diaphragm Carbs, as capgun said they were used till early 1971, These were specific to Slanted engine applications only which began when Fox corporation introduced the angled engine plate design on their 1969 bike lineup.....Everyone quickly jumped on the bandwagon for 1970. In 1971 they created the slanted intakes so the bowl carbs could be used and they got phased out. I am not sure why the change was made at that time, from what I can tell a choke lever and air cleaner placement dilemma may have played a part in it, they had the same problem with standard horizontals and bowl carbs at the same time and made a revision during 1970 on those to better accept Header type systems that were becoming the norm.
There were only 2 versions of this carb that I can find, one for the H30/H35 and one for the HS40 and again their soul purpose was for the slanted application so you wont find them setup like this on anything else. Looking at Tecumseh service carburetor lists, they never offered a suitable replacement for it either. These mini bike/cycle specific carbs look virtually identical externally so you want to look at and decipher the stamped numbers found on the intake side flange of the carb body to know which one you are working on.
The H30/H35 part number is
631595, the stamp number on that body will start with
379
The HS40 is part number
631588, the stamp number on its body will start with
356
One rather unique thing that makes them stand out over most others and easier to spot is the choke lever and detent, Rather than the common spring rod detent it is a stainless sort of clip looking bracket that screws into the body, the lever is pretty standard but it has a flat spot on the upper shaft to help lock the shutter in the open position.
This is a 631588 version I just completed for a 1969 HS40 that I am currently finishing up:
Here is that carbs body from above in comparison to the H30/35 631595 version on the engine I just did:
As you can see, your really cant tell them apart externally, so it is important to refer to the stamped numbers on the flange. Only other difference I see (and I dont know if you can depend on that) is the cast number on the left (needle) side just in front of the air cleaner base mount lug which you may be able to make out in the one photo above. the H30/35 had a
21 cast in where the HS40 has a
22
I had intended to do an actual comparison build thread of the 2 carbs but that didnt work out and I needed to get the H35 finished and out of my way. Hopefully the shots I took though as I rebuilt the HS40 version the other day may help show what I did find as differences between the 2 carbs.
Key difference i found between the 2 that you will spot is under the diaphragm. above the carb body has been gutted as far as you can take it (all welch plugs and needle assembly removed)
I found the H30/35 to have welch plugs covering both the High and low speed circuits, where the HS it was covering only the High speed circuit and the low was just left open. On the H30/35 they drilled a passage connecting the 2 reservoirs where the HS did not have the passage drilled
I put this cleaning needle across on the HS body about where that passage was drilled on the H30/35:
the passage was small and angle drilled but in about that same line. OEM tecumseh rebuild kits for these cover an array of versions, so there are more parts than needed, So don't go plugging holes just because the welch plug is in the kit, If that passage is not drilled you will take the low speed circuit directly out of the picture if you plug that port up. Low speed is the one to the left of center with nothing in it but a tiny hole, High speed is the centered one with the non serviceable brass check ball assy in it.
Parts listings show that both carbs use all the same rebuild and bolt on parts, I dont see anything else visually different between the 2 bodies other than the port passage, I did forget to measure the bore on the H30/35 though :doah: The HS40 version I got about 11mm at the choke point. Thats a little smaller than the stock HS bowl carbs, but dont let that fool you. When they are cleaned correctly, worn out parts like the throttle shaft replaced, getting clean fuel supply, and on a decently tuned engine they run pretty dam good.
Thanks
