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Collection, Preservation and Display of Old Lawn Mowers

Briggs & Stratton small two piece Flo-Jet carb

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I’m looking for some help in my attempts to replace the emulsion tube in this carburettor.  Someone (not me, I hasten to add) has completely stripped the slot from the head of the inlet seat and has also damaged the threads in the carburettor body, presumably by using the wrong type of screwdriver. I can add a photo of the carb but I don't think this will show the actual problem.

I was thinking of drilling out the whole of the assembly and reaming the bore but am wary of damaging the remaining threads. I would have to use a hand held cordless drill which probably would result in tears.

(I recall in an old forum topic that Wristpin commented that things can get ‘interesting’ at this stage!)

Can anyone suggest a solution please?

Forums

wristpin Sun, 19/04/2020

I think that my comment referred to a similar problem with a Dellorto resulting from a similar failed attempt to remove the main jet / emulsion tube.

The BS two piece flow jet carbs do present with a similar issue . It’s a long time since I’ve tackled one but before going for the full drill out option I’d suggest the following .

Enlarge the centre hole enough to accept the smallest of a set of taper “ easyout” extractors. ( I hate the things but there are times.......) only enlarge the hole enough to accept the small easyout so as ro retain enough jet metal for it to grip without expanding it. Then pop the whole carb into a pan of boiling water and get it good and hot. Gloves on and insert the easyout and pray.

I have drilled them out but as you suggest it is a hazardous operation . The carb is difficult to hold securely and, as you observe, using a hand held drill tends to be a bit hit and miss. You may not wish to purchase a rebuild kit until you’ve extracted the old tube but having the new tube to hand does give a guide as to the size of drill that it is safe to use.

 

David Hewison Sun, 19/04/2020

Bingo! Wristpin's method worked.

For future reference if needed, I drilled out the centre hole of the emulsion tube seat with a 1/8th " hss bit.  Immersed the body in boiling water then inserted a No.2 EasyOut extractor.  Sharp tap with a hammer and the whole emulsion tube unscrewed nicely.  The heat must have broken the bond.

Unfortunately the body threads are damaged and the replacement tube will only go in about two turns so I've ordered a reamer from Briggsbits and will hopefully will be able to repair the threads sufficiently to seat the tube fully.

Thanks Wristpin and also for the additional info in Dropbox.

One final query.  I should replace the Venturi gasket but wondering how to insert it around the half-moon shaped lug on the body? Is the minute hole in the lug a fuel channel as the replacement gasket has a hole in that position? If so, what is the best way to clean it out?

Any guidance would be appreciated.

wristpin Sun, 19/04/2020

Not sure about a "reamer" to restore the threads . May be a terminology thing but my idea of a reamer would remove them!

Suggestion, take your scrap jet and carefully cut a new screwdriver slot in the top . Equally carefully cut a slot at right angles into the threaded area, just slightly deeper than the threads.. (Junior hack saw blade or Dremel slitting disc.) Then carefully screw the jet back in  - hopefully the slot will clean up the threads in the body.

I cant find a sectioned drawing to identify where that hole goes - could be a bowl vent. Will the squirty tube on an aerosol of carb cleaner not give a clue to where it goes and what it does. If that doesn't work, you could try a bit of old fashioned fuse wire.

David Hewison Sun, 19/04/2020

Thanks Wristpin.  I'll try your suggestions and post the results here.  May have an un-used 'reamer' on my hands!  (I used the terminology from the main B&S Online Store website).

wristpin Sun, 19/04/2020

I tried searching reamer on  Briggsbits and got a nil result, same for “ thread chaser” and “tap”.

Are you able to post a link to what you have ordered?

 

David Hewison Mon, 20/04/2020

Hello Wristpin.  The link is: https://shop.briggsandstratton.com/products/briggs-and-stratton-19066-reamer

It's out of stock in the US but available through Briggsbits as a special order.  I looked at the Briggs & Stratton L-Head Repair Manual and it mentions a Tap Set part 19245 however this is now obsolete.

Anyway, I've followed your earlier advice & solved the problem by re-tapping the carb body with the improvised tool so the reamer is going to be surplus to requirements. 

On the subject of the mysterious hole in the Venturi seating, I used fuse wire as you suggested and this worked.  Flushed through with carb cleaner and all good.  The hole comes out half way up the bore of the emulsion tube orifice.

Thanks for all the advice.

On a final note, a previous owner of the carburettor had sawn through the control rod to the mechanical governor and had overdone it a bit and sliced a cut in the inlet manifold.  Then sealed it with chewing gum!  Might have to revisit that area!

 

 

wristpin Mon, 20/04/2020

Gum is probably perfectly effective - just don't start chewing  on JB weld.

Good job that you didn't get your hands on that reamer it would have taken all the threads out. Its probably for over sizing valve guides.