HarleyTechTalk

I had a good friend call me to ask if I had any thoughts on what could cause fuel to leak profusely from the overflow tube from the carb on his 1986 Sportster.   He said he has a carb kit ordered and is a very competent mechanic with his own business.  After some discussion I suggested if the petcock shut off properly it was most likely the needle valve contaminated from corn residue.  He pulled the breather and later showed me it was also leaking above the carb bore and dripping into the throat from the front breather mating surface.  It's all fresh gas but may be a little late.  He's going to drop the float bowl and service / clean the valve and check the float.

Is there anything any of the resident Sportster gurus can tell me that may have been a regular occurrence (other than the needle and float cleanup) with the symptoms I have described?  I would like to help him out if the cleaning isn't successful.

Those are the obvious culprits, leaking float or needle and seat.

Of the Sportsters that I have owned...the only times that I had a Gas leak like that was because of the Petcock seeing better days, and not completely shutting off the Fuel.
Repair, or more so Replacement of the Petcock remedied that.
Besides doing the Float Bowl and Needle Clean-up...I would take the entire Carb apart and start from scratch.
Is that the Original Carb?

Agreed on the petcock, it certainly shouldn't continue to leak if the petcock is off.

Yes all original and appears to be unmolested. The petcock is functioning properly.  When opened the fuel flows freely out the overflow hose at the lower front of the engine.  Also now confirmed dripping from the top / front of the carb into the throat.

that vintage ....  I remember something about the needle and seat being a problem .... 

I'll need to look at the SBs to refresh the memory

something about 'if the needle is 3 sided then it needs to be replaced with a 4 sided one'   .......

I would put more faith in a new needle & seat. The material (viton?) gets hard and develops wear patterns that can be uneven and leak. I had a 1987 XL and I also remember something about 3 sided/4 sided float needles.

Thanks folks.  I ran this by my buddy.  The kit did come with a new needle that actually looked different. Unfortunately it was too long as in it drastically changed the float level.  His response was to clean the needle seat and retry it.  That seemed to have cleared up the overflow hose discharge (but he didn't leave it sit for any length of time to test duration).  Now there is a leak from the accelerator pump plate he is chasing.  I did mention to him that there was a known touchy O-ring behind the block and he was disassembling it as we spoke on the phone. 

The carb is cast with Harley Davidson on it.  It turns out it has all the signs of a butcher being into it with a dull Philips screw driver.  There's a chance the kit he received is wrong too. If no joy he will call the dealer and confirm the kit also.

FSG, if you do remember the SB ID I would be interested in reading it and sharing it with him.

A new/used cv carb would fill the bill.....

Here's an update and hopefully a lasting resolution.  The accelerator pump appears to have been as a result of the notorious O-ring behind the plate issue. The float bowel was removed, the new longer one was installed and the float readjusted for it.  Both the pump and overflow leak seems non existent now. 

My buddy also confirmed the old needle was 3 sided and the new longer one was 4.  I expect the new replacement needle being longer and having 4 sides is less apt to cock and hang up in the barrel, therefore working better. 

Thanks to all that took time to respond and contribute.

Quote from: FSG on June 26, 2023, 11:35:21 PMthat vintage ....  I remember something about the needle and seat being a problem .... 

I'll need to look at the SBs to refresh the memory

something about 'if the needle is 3 sided then it needs to be replaced with a 4 sided one'   .......

Service Bulletin M-1029, December 18, 1992

1990 And 1991 Big Twin Models Carburetor Fuel Inlet Valve Inspection/Repair

 Carburetor Fuel Inlet Valve Kit also mentions 3-sided valves should not be used in CV carburetors.

The "butchered" phillips screw heads are common, even if the best fitting screwdriver is used on those carbs. The screws are made from some strange alloy of metal and butter! Years ago I bought little boxes of the various sized screws and washers from McMaster-Carr. I got them in stainless steel with "Allen" heads. Spent an hour or so sorting them into bagged kits. Since then I have just pitched the phillips screws and used my kits when servicing Keihin carbs.

QuoteFSG, if you do remember the SB ID

Frisco hit the numbers 

-J01099 CARBURETOR FUEL INLET VALVE KIT  2013-11-01

-J01099 CARBURETOR FUEL INLET VALVE KIT  REV. 9-1-91




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Quote from: SP33DY on June 27, 2023, 02:03:49 PMThe "butchered" phillips screw heads are common, even if the best fitting screwdriver is used on those carbs. The screws are made from some strange alloy of metal and butter! Years ago I bought little boxes of the various sized screws and washers from McMaster-Carr. I got them in stainless steel with "Allen" heads. Spent an hour or so sorting them into bagged kits. Since then I have just pitched the phillips screws and used my kits when servicing Keihin carbs.

The stock carb screws has a dot on the head, telltaling it is a JIS screw, requiring a special JIS screwdriver.

Quote from: Hossamania on June 27, 2023, 09:10:39 AMA new/used cv carb would fill the bill.....

And a few more parts like intake manifold, choke cable w/bracket, air cleaner setup and throttle cables 😊

Quote from: xlfan on June 29, 2023, 02:32:31 AM

Quote from: Hossamania on June 27, 2023, 09:10:39 AMA new/used cv carb would fill the bill.....

And a few more parts like intake manifold, choke cable w/bracket, air cleaner setup and throttle cables 😊

CV conversion. The best upgrade available, bar none.
John