TR2/3/3A Choke setting tips?

[HighAltitudeTR3]

Why is this cruxing me?! Seems my choke is in need of adjustment, and I know it’s not hard, but I get everything all wonky when I do it. My cable isn’t the right length or my screw isn’t set right or but I would say the most troubling setting is the needle set dealy mabob won’t sit right. I tried new springs, they don’t seem to pull enough to get everything to return properly, but they are new from Moss...

Thanks!!

 

[TR3driver]

Get new springs to go inside the jet bearing. While you're at it, replace the cork glands with the Orings from Moss.

While the jet is out, polish the surface to a high gloss. Any brass polish will do, or even just ordinary white toothpaste and your fingers.

Your chokes should work much easier after that.

Also check PH for how the linkage goes together. It doesn't look right, but putting the clevis off to one side at the front (instead of straddling the lever) really does work better.

 

[HighAltitudeTR3]

Thanks Randall, I’ve done 3/4 of those, I’m going to polish the jet, that actually makes sense that is where it’s binding.

While I’m at it... I think I’m going to replace the outer cork gasket (the one above the nut that holds the idle adjustment nut) with a rubber o-ring, I can’t get a good seal with the cork. Have you done this? I’ve gone through 2 sets of the cork gaskets and they just don’t cut it.

 

[sp53]

Getting a stock choke correct is a challenge at least the first time. I am not sure what you mean by the needle deal maybe a Moss part number would be better for me because of all the little stuff. Is that the long clevis with the nut on the end? You can leave all the slack of choke cable under the dash. The end part where the cable hooks up is critical, But again you can set the end up with the bolt and pin and let what inner cable you have run long and put the pin through the hole as an assembled unit last. The clamp that holds the outer sheath would be hooked up next. Some fiddling will be needed to get both jets coming down the same. But again you can leave the back clevis pin cotter key off and take the clevis in and out as you fiddle with that rod.

One critical thing to look for not totally related to the choke is the length of the spring where the cork glands seals are. People sometime stretch that spring thinking that will help with the seal of the assembly, but what it does is hold the jet out from completely returning home. I actually owe that one to Randall. I fought that one for days. One more thing sometimes the SU kit parts are superior to the piece meal stuff and that Joe guy back East has a ton of knowledge and often the best price on quality parts.

 

[Alfred E. Neuman]

I'll second Joe Curto's expertise on all things SU. When I had my TR3, I got the throttle shaft rebush stuff from him. Super helpful and his videos made it a breeze. Wouldn't hesitate to recommend him for any carb work.

 

[HighAltitudeTR3]

Ok, a lot of good feed back. I just spent a few hours tinkering and I thought it would be beneficial to list what I did. (with correct part names!)

so my problem was in a couple spots - first my jet Head was 1/3 open and sticking. When I would release the choke it would not snap back to zero. The choke cable was not extended from the cable housing enough, but with the sticking jet, it didn’t matter. The jet connecting rod was not properly set. Finally the float chamber attachment bolt (the one that basically cradles the jet) was misaligned.

Firstly, I removed the entire jet adjustment assembly and began polishing each piece in order to stop the sticking. For the record I think it was sticking because of age and wear and also because the float chamber adjustment nut was misaligned. For the jet itself, I chucked up the clevis pin attachment very loosely in my drill. Then I took a piece of 600 gr wet sandpaper and polished it to brand new (ps... I tried toothpaste, I didn’t clean it completely off the jet at first and the toothpaste ended up turning in to almost rubber when it mixed with the gas. Obviously, I got too ahead of myself. But neat chemical reaction. Anyway...). I took a different piece of 600 gr wet sandpaper and rolled it up and chucked that in to my drill and polished the inside of the float chamber attachment (jet cradler nut) as well as the bottom half jet bearing; the jet touches this and the jet cradler nut. i cleaned up the rest of the jet adjustment assembly and put it back in the carb. I really think it’s worth pointing out that the jet adjustment assembly is best to put in with the suction chamber assembly, jet lever (brass piece that connects the jet to the choke cable), the jet lever link (connects the choke cable housing to the carburetor), and the connecting rod that connects to the choke rocker lever removed and out of the way. Basically have a clear shot from the bottom to install the jet assembly.

Now I was told again and again that you need to line up the needle with the jet and you get a nice metallic clunk from the suction piston. I had done that, piece of cake. I did not know that the jet had to move just as easy. I guess it sounds silly that I didn’t check it, but I didn’t realize the mechanics of it until I saw it functioning perfectlyg. (Now it’s obvious). Once everything moved as it should with the screws tightened down i started pieceing the carb back together. The other adjustments were obvious - adjust the connecting rod so the jets open and close equally. Choke cable needed probably 3/4 of an inch more slack, I would guess there is about and inch and a half of cable at the end. I adjusted this several times. Basically until the could pull the choke cable in and out several times and got the same result. Added some oil to the dash pot and tuned the carb as usual.

Anyway, I’m putting this up because while there was some great info here, there is not a lot of info available in general about setting the choke up properly. I hope this helps someone down the road. Feel free to continue to add any tips here.

Thanks!!

 

[sp53]

Glad to hear you are wrapping your mind around the carbs; they really are a simple and clever design. I always appreciated how there is basically no friction when the adjustments are correct. Like the piston does not touch anything really; it does sit flat on the body when stopped--the click, but when working it is floating. The dash pot is essentially a vacuum seal bathed in oil for stabilization plus you can change the oil for different climates. Back in the day automatic transmission fluid is what the cool kids used. I use 20 weight, and it probably does not matter too much unless the climate is extreme or you are racing Mad Max.

Anyways, so how many clicks does your choke make before it bottoms out and do you need to twist the knob to the right to have the choke release? My choke basically has 2 clicks the second click is where I pull it for winter starting and the first is for cool summer or when the engine has cooled down. I think of the choke as a fuel enricher (embezzled that one from John) and the gas pedal as an access for more air. (No accelerator pumps on a SU) I also will sometimes when the temperature is not too cold or hot and starting is in question,just pull the choke out about ¾ of an inch turned to the right and let it go back in-- just to let some gas in as I have the gas pedal open for a blast of air.

 

[TR3driver]

FWIW the jet shouldn't actually touch the hole on the adjustment nut. Should be just a bit of clearance there, so the sides of the jet only ride in the glands. So there's really no need polish it (although it certainly won't hurt).

The original jets came nicely polished, but many replacements are supplied rough and need to be polished.