TN-28 carb overhaul

[obnut]

I am overhauling the carb on my tn-28. I can’t get the brass washers and leather seals out of the primer pump. I have used the suggestion made by David Poche in his fine article on servicing tn-28 carbs. The carb was quite dirty, I have used carb cleaner, alcohol, acetone, and simple green. Also tried heat and they will not budge. Does anyone have any suggestions.

[frankr]

I have a few comments concerning that otherwise excellent article. First is that heat usually is counter productive in such a situation, where you have a brass part in aluminum. The brass expands more and faster than the surrounding aluminum, which actually makes it TIGHTER. You might be better off putting it in the freezer, although I never have. See next comment.

Secondly, while I respect the idea of tapping the brass tube, personally I tap the upper packing washer with a 3/8" tap, and pull it and the tube out at the same time. That is, if the washer doesn’t spin. You can re-use the threaded washer, maybe not so with the tube. Your choice.

Lloyd is quite ill at this time. You may have a problem getting parts from him—I dunno.

[itchy]

I also just overhauled a tn28 carburetor – and had the same problem. I was able to get the top brass washer that is below
the brass tube out – but could not get the leathers or the bottom brass washer. So – I left it. I’m going to see how the primer
pump works. If it doesn’t, of course I’ll get back into it and will get it out one way or another. This was my first attempt at
this tn28 carburetor and I also had read David Poche’s fine article – and tried to follow it.

[shoestringmariner]

You might find your leather seals will swell up with fresh fuel as mine did. (though I can’t say if that lasts long)

Anyway, since Lloyd is not well (and wishing him better days ahead of course) you can get the seals here; http://www.effenaco.com/store3/viewitem … oductid=28

In addition to the freezer comment, gently heating the carb and then dropping ice shavings into the pump bore might fast shrink it.
I do similar when trying to remove shallow bolts I cant afford to break off. (heating with a torch and then quenching the head with a water bottle…works like a charm)

[Steve A W]

Try canned air that is used in cleaning computers.
Give it a shot of that and it will put a freeze on it.

Steve A W

Member of the MOB chapter.
I live in Northwest Indiana

[legendre]

Heya obnut,

quote obnut:

I am overhauling the carb on my tn-28. I can’t get the brass washers and leather seals out of the primer pump. I have used the suggestion made by David Poche in his fine article on servicing tn-28 carbs. The carb was quite dirty, I have used carb cleaner, alcohol, acetone, and simple green. Also tried heat and they will not budge. Does anyone have any suggestions.

Those thin-wall brass tubes used in the carb’s primer seal stack can be a serious beotch. I have two TD20 carbs here, and I’ve only managed to pluck the primer goods from one of them. The other, that tube just won’t move.

Heat +may+ temporarily tighten the brass part in the zinc / pot metal carb body, but that’s no problem once things are cool. Either way, you can take advantage of the differential expansion, as it might break-away some corrosion that’s gluing the parts together. But of course, wait ’till the carb is cool before you try to extract the brass item.

[jim-moffatt]

To save a lot of effort you can install a #109 o-ring under the primer spring. It forms a perfect seal between the plunger and the plunger tube.
Leave the old parts in the carb simply add the o-ring. I have done this to several motors and it works excellent.

[itchy]

After not being able to get the leathers and bottom brass washer on the first goaround, I gave up, put the motor back together
and put it in the barrel. It started on the first pull, but gas was running from everywhere on the carburetor. Took the carb off
again – got both brass washers and leathers out. Leathers appear good -might just need to get soaked up. But, believe I have
a float problem and will coat the float cork with something different than I have been using.

[obnut]

Thanks everybody for the ideas. I will give them a go and see what happens.

[shoestringmariner]

quote itchy:

gas was running from everywhere on the carburetor. But, believe I have
a float problem and will coat the float cork with something different than I have been using.

I’ve read that gas coming out from the top is a float issue and only out of the plunger bore when depressed is a leather seal issue.

[Author]

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