The Stovebolt Site Forums The Shop Area Engine Shop Tillotson JR5

My truck has this Model JR5 Tillotson carburetor installed , supposedly a replacement. May be a replacement, but it doesn't look like one. Everything fits too well

My question is what is the purpose of the brass needle valve with tee handle shown in the bottom center of the photo? Is there a base adjustment or just open or closed?

Jim


http://i6.photobucket.com/albums/y233/zevron/Tillotson%20JR5%20Carb.jpg?t=1430944828

Hopefully Jon or Mike will say something about this carb. But my comment is, VERY cool! You didn't say what year truck you found it on. Thats a very neat find, and if/when you can't get parts for it anymore, save it for nostalgia! It wouldn't surprise me if its made better than the stock Roch B.

Ditto on the carb looking good. My swag is that carb has an adjustable main jet, which would even more cool.

I've heard of Tillotson but can't quite place it, I believe they made HiPerf carbs for HD's but my memory's foggier than usual tonight.

Good luck
Dave

Tillotson made industrial engine and outboard motor carburetors, also carbs for small engines, motorcycles, airplanes, etc. That T handle is on an adjustable main jet, and the carb was probably on some sort of commercial rig at one time. Most fleet mechanics would adjust the main jet(s) for the best performance under load, and then cut the shaft off flush with the gland nut to keep drivers from tinkering with the high speed mixture adjustments. Lots of engines have had the pistons melted out of them by drivers trying to get a bit more performance by leaning the mixture a bit and then driving full throttle for long distances.
Jerry

When I ran into a Tillotson carb on small equipment in for repair, I would always smile. Very reliable and easy to work on.
Hope that yours follows suit.
Carl

1937 Deluxe pickup factory original??
1. The carb appears original to the truck.
2. The engine is satin blue-black in color, not grey.
3. The dash/interior panel color is wrinkle dark brown, NOT bronze or beige.
4. Remnants of an odd looking ribbed rubber floor mat/covering.

I have no instructions for the use or adjustment of this carburetor. Anyone have any ideas? I presume screwing the jet in leans it out and unscrewing it enriches the fuel mixture?

No oil pressure when running. Pressure gauge bad? Only ran for 1 minute at a time.

I love that advance/retard mechanism. Found a coil, starter switch, rotor cap, and rotor at a roadside junk shop. Going back to look through more parts (all NOS in their original boxes).

Jim

Tillotson made a "J" series carb that was original equipment on Willys. They modified the "J" series into the "JR" series (the "R" meant replacement). Going from memory, there was a JR-1 through maybe JR-7. The JR series were basically "throw-away" carbs that were sold through the cut-rate mail order houses to customers too frugal to purchase a rebuilding kit for their original carb. All of the JR series were replacements.

I won't suggest that you not use it. However, some of the JR series have a cast iron throttle body, and we took several new old stock ones, and cut the cast iron throttle flanges from the rest of the unit. We could then weld two of the flanges together to make carburetor adapters. The rest of the units were trash-canned after cutting off the flanges.

To answer your question about the T (which has already been answered), yes it is an adjustable main metering jet.

EDIT: I just looked at the picture. The carb pictured is NOT a JR-5. All of the JR series were updraft carbs. Cannot tell for sure, but the pictured carb is either a DR or YR (again, the "R" meant replacement). The DR series was produced in the 1930's. I would have to pull the files, but I don't believe the YR series came out until after WWII. The DR and YR were downdrafts, the JR were updrafts.

To see a JR-5, see Ebay 291402291455
To see a YR-2, see Ebay 171722409076

Jon.

Clockwise is lean, CCW is rich. Start by gently seating the main jet full CW, (don't force it!) and back off 2-3 turns. Take a test drive. If it's short on power, go richer about 1/4 turn at a time until you get the best performance under full throttle load like up a long hill. If it stumbles and smokes black, lean it out 1/4 turn at a time. Once you've found the sweet spot, don't mess with it- - - -tighten the gland nut snug to keep the adjustment from changing and forget that it's adjustable.

If you make a major change in altitude, like from sea level to Denver CO, etc., the higher altitude needs a leaner mixture. If you're adjusted for high altitude, richen it up a little as you go downhill several hundred feet or more.
Jerry

Wow, great responses. I have no way to know if and when the carburetor was replaced. Certainly possible, and evidently the only way it could get onto the truck. It fits perfectly, and appears to be a nice carb. I will keep it as is.

Thanks guys. I do need all the help I can get.

Jim