Reamers for bushing throttle shaft.

[HolyHarp]

throttle body is cast iron or cast steel. I might be able to find some drill stock to turn and grind into a tool.

 

[Downunder Bob]

There is a very simple way to fix this, it's rough and ready, but it's quick and will be a lot better than what you have.

I'm assuming the carby is out of the vehicle and on the bench. First how bad is the slop in the bush and shaft, again i'm assuming it's pretty bad

Remove butterfly shaft from carby and clean it up as much as possible. in a lathe with a fine file and emery cloth, make sure it is parallel along its length. Clean out the holes in the carb body. clean with acetone or similar solvent. apply some silicone mould or die release to shaft and assemble the shaft with butterfly plate, into carb body,

If possible get a very thin section "o" ring onto the haft at the inboard section up against the butterfly plate, if not possible twist up a length of teflon tape into a fine string, wrap this around the shaft and stuff it into the hole. push it right down to the butterfly plate on both sides, this will stop the adhesive from getting right through.

Now mix up your Jb weld, bondo or whatever petroleum resistant stuff you can get. Make sure the butterfly is fully closed this will help to align the shaft in the correct position, Press the mix into the gap between shaft and hole in housing, clean off outside and let cure.

remove teflon tape from inner ends of shaft you may find an "o"ring pick useful here, Then you should be good to go. If this operation is well done the results are quite good. Not as good as a new one but a heck of a lot better than a worn one, and no special skill or tools required.

The only problem that can occur is if you haven't applied the silicone die release properly to the shaft. an alternative is to use a teflon spray that dries and then a thin smear of grease.

 

[NortonDommi]

It's a Nissan keep it Metric. Locally I can buy a set of 10 machine reamers 2 - 10 mm for NZ $60 and I've seen them cheaper. Thailand makes a LOT of tools so should be available local to you and cheap.
I regularly make bushes and shafts for carbs on old vehicles and small engines. Aluminium tube is good for bushes or bronze.
You have not said what equipment you have access too. You could do the job with a drill press and quality drill bits and have success if just making and fitting bushes. As C-bag said making a jig is the key to success. You will need a mill with a slitting saw to make a shaft though unless you are a god with small bits and a hacksaw or is the butterfly mounted in a rebate? If it is a vice and a file is all that is needed apart from a drill and tap for the screws. Are there O-rings fitted? Some carbs have them on the outboard ends of the shaft.
As a last resort from broke days living in the wop-wops Araldite or similar Epoxy works surprisingly well for building up worn shafts and can also be used to lock bushings in place if you don't have Loctite.
Also what Downunder Bob said.

 

[C-Bag]

Right now the engine dies when the clutch is disengaged and the accelerator is not pressed - it dies at idle.

I'm thinking of looking for a used carburetor at a wrecking yard.

THIS to me is the most pertinent info that should have been mentioned earlier. So if you screw the idle mixture screw all the way out, or even in and out, it doesn't matter? Can you even get to the mixture screw? Here in California it was behind a soft plug and you had to remove the carb and drill and pry out the plug. With the mixture screw you should be able to make even a car with a vac leak run. There is a lot of hoses and stuff to that can be "internal vac leaks" like a stuck PCV or Ive even seen brake boosters leak internally.

A worn throttle shaft in my experience could never wear enough to make an engine die with the mixture screw working.

To see if it was the throttle shaft my test was while running I'd spray carb cleaner on that area of the throttle shaft while running with some carb cleaner spray. If it was the throttle shaft the idle would go up and smooth out. Also are you sure the idle solenoid is working? If it isn't it won't idle no matter what you do.

 

[tq60]

First stop fussing with the carb and seek out replacement as that is best option.

Next...is that why is does not idle?

Could be many other things wonky causing this.

If it has a carb and is a "smog" engine then it likely has vacuum hoses all over it along with valves and other things that control egr (one likely cause clean this first) or timing or ???

Save the carb for last as a worn shaft can be "adjusted out" via mixture until rest is corrected.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

 

[C-Bag]

I have a question- just how tight was the throttle shaft to body when new? Who has THAT number? There is no lube, other than gasoline and dirt!
What I am saying, is this- If the shaft- to- body clearance has worn to the point it has become a detriment to driveability, then ANY reduction in that wear will improve driveability. As soon as you come off idle, what is the path of least resistance for airflow? If you make it TOO tight, that will surely affect driveability!

There are a lot of minutiae of carbs, especially as big and complicated as the QJ. As a certified smog mech at the time in the most stringent area in the US, stuff that was not a big deal elsewhere made it so cars wouldn't pass. With a leaking throttle plate it wouldn't pass the idle spec but would pass with flying colors at 2k rpm. This is stuff that the hobby mech wouldn't have any clue about without a BAR smog machine and scope.He could set the idle mix on that side of the QJ a little bit richer and compensate to smooth out the idle. And not until he had to have it smogged would he know it wouldn't pass.

You are right about the throttle shaft has to have some play in it. Probably .002-.004. The QJ TP was a poor design IMHO in that it appeared to have a generous boss on that side of the carb. But when you pull the shaft(which the ones I did were all Teflon coated) that boss was relieved 3/4's of the way and only the last like 3/16" was actually the bearing so no wonder it wore out quick! They usually had two humongous return springs that were often pulling in the same direction as the throttle cable! Born to die. And the TP was aluminum IIRC. Or pot metal. Been 30yrs.......

 

[pstemari]

... it seems that reamers usually come with a 1:50 taper. Is this the type of reamer I need?

No, those are for taper pins. You want a straight chucking reamer, probably a new one given the demands of the application.

... I guess no one makes a .309 reamer nor a 7.86 mm reamer....

Any decent industrial supply house will have reamers in 0.0005" or smaller increments. Dunno about metric sizes, but I would assume 0.01mm increments are readily available.

 

[Downunder Bob]

A quick test. Pack some thick grease or evn putty around the the carby shaft if it will idle then the worn shaft is you major problem. If it still still won't idle then you have other problems to sort out first. You may find when those problems are sorted your carby is ok.

 

[Downunder Bob]

Another quick and easy fix for a worn carby and shaft. No special tools or skills required. Can be done on the engine without removing carby.

Tools required,A light pair of metal shears or even good kitchen scissors will do. Warning do not use mums sewing scissors.
Materials required: Empty aluminium coke or beer can.

Method: disconnect carby linkages and remove linkage connections from end of shaft. Cut a few strips from side of can so that strip width is slightly less than length of hole in carby body, cut strips to length so that when wrapped around shaft you get a nice clean butt joint without overlap or gap. slide one or more strips into clearance between shaft and carb body until no more strips will fit. Reassemble linkages and you're good to go.This will keep an old carby going for quite a while.