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Allan G, Gordon Gray, kommando, NickL
Total Likes: 14
Original Post (Thread Starter)
by Bustednukel
After battling the plug to get it out by shaving a drag link and grinding the plug to a size to fit the drag link, and ordering a Whitworth socket set from AB Tools in Stoke (very nice set with unbelievable price including U.S. shipping), and studying the qualities of the hardness of the flywheel bolt with an eye to heat it up since it's possibly red loctited in there since the factory did it that way and you might need new flywheels or EDM (electrical discharge machining) or other means to remove it if you mess it up, and after removing the flywheel bolt with reasonable force with no heat, and attempting to use a 3/8 18 TPI pipe plug to grab the sludge tube only to discover it rotates freely and pulled it out with my pinky, and noting that the sludge was not all choked up and just soft carbon, then I thought clean it all up and get a new plug.

The plug was about 2 threads deep and both of these 2 threads are almost ok, but not quite. So, the right size tapered tap should clean them up nicely. Maybe sellers who have the plug might list the thread size, ya think! ? One seller mentioned CEI thread for the plug .So, started looking up CEI thread sizes and taps. Also, BSC taps since they are the same right? Looked at some you tube videos on pulling the trap hoping one might mention that cleaning up the threads could be done with a certain size tap but struck out on that one. Then I found a vendor who sells the tap for Trumpets: 7/8" 20 TPI. The threaded hole for the plug is about .830 and about right for a 7/8 tap. So, before I go screwing things up after all this, thought I'd ask the BSA Britbike community to confirm.

Also, can CEI thread be cleaned up with SAE taps or dies? I didn't think so. Is the vendor who mentioned CEI thread for the plug off base? Is SAE 7/8" 20 tpi the way to go? CEI thread for this application prior to a certain year and after that SAE?

Also, one youtube guy said only use the OEM style plug since the hex drive ones do not weigh the same and will mess up the left right balance. Made me think does he really think the OEM style mfrs are weighing the plug, and pulled sludge trap on rebuild and all the new stuff weighs the same, but watch out for the plug? LOL

Thanks for your replies and thanks for being nice. I apologize for the long whine but hey it was fun!!!
Liked Replies
by DMadigan
BSF means British Standard Fine which for 7/8" is 11 TPI. There could be a Parallel Thread of Whitworth Form for 7/8"-20 TPI but it is not a standard just as for Unified threads you can make 20 TPI in any diameter.
2 members like this
by gavin eisler
gavin eisler
I am not sure if you need a full size tap, a 3/8 BSF tap is 20 tpi, if you just need to clean up the start threads it would do .

You dont even need a lathe, just a bit of perstince, a bit like an internal thread file.
2 members like this
by John Healy
John Healy
I hope the person who loctites a sludge tube plug is the one that has to remove it.
2 members like this
by John Healy
John Healy
Where I come from if a drop is good, more is better. We are a society of the larger hammer. Now in nearly 60 years of doing this I have never seen, or heard, of a sludge tube plug causing a problem using a single punch mark. Being one of those guys who others turn to when they face what they feel is a problem I have seen plenty of plugs that require extra ordinary creative solutions to remove. Using a thread sealant and a single punch mark on the face of the plug into the mark left on the face of the crankshaft cheek will retain the plug safely.

On rare occasions the plug will not seal the cavity. Pump some oil into the end of the crankshaft to check to see if any oil leaks out the plug.

Save your blue loctite for the alternator, and transmission mainshaft nuts. I Belong to a group of mechanics who believe you should have a License to buy Loctite. It’s short comings have been exposed when they changed the formula. To make it work it was required to use a primer on oily, non-reactive metals and coatings (plating). Using Red Loctite on plated hardware and it barely worked. No need to get the nut to 400-450F to get it to release.

We were saved by not reading the technical data. Every one believed the primer was just a cleaner. It contained a missing compound the allowed the Loctite to set-up when used in oily, plated or non-reactive metals. We were lulled into thinking we could work with the stuff. On occasions it would work and you would find out what 400-450F really meant.

With the the new formula you might as well have brazed the nut. No primer required. While in the old days an oily no reactive or plated surface would not let the Loctite to work very well. No such problem with the new Loctite.
1 member likes this
by Tridentman
For taps and dies I always use:
a) British Tools and Fasteners in NYS for US source.
b) If BT&F dont have it then Tracy Tools in UK.
1 member likes this
by Bustednukel
Wow, one could really screw up on thread sizes!

Tridentman, thanks for the input on a U.S. supplier, British Tools and fasteners in NY State. They have a very good information breakdown for the uninitiated on Imperial thread sizes like myself. Seems BSF 7/8" 20 TPI is not catalogued there. Also, It seems that thread size is not catalogued anywhere I have looked so far. Found Tracey Tools in the U.K. a day or so ago and thought I hit pay dirt with their BSC 7/8" 20 TPI carbon steel tap for about 12 quid plus ship to U.S. Tracey had no BSF 7/8" 20 TPI taps.

Little D, tried and died on all 3 of the sites looking for BSF 7/8" 20 TPI. U.S. sources are much appreciated So far it seems a tap that size will be hard to find but thanks!

CBS, Complete British Spares, in Lancaster, CA USA had a 7/8" 20 TPI tap for 70 U.S.and described online as fitting the BSA/Triumph 650 and 750 but no thread type described. I emailed CBS inquiring about the thread specification and received a prompt reply that the thread type is UNEF. UNEF 7/8" 20 TPI is a catalogued thread type.
1 member likes this
by Mark Z
Mark Z
Hi Bill, glad to hear you're finally meeting with success in finding a tap. (FWIW, it's Classic British Spares.) That's a big boy, so I'm not shocked by the price.

I'm skeptical that the hex socket plug would make a significant difference in crank balance. Are you planning to have the crank balanced? If so, they could use whichever new plug you source. I think the hex socket plug is a good idea *IF* you think you'll ever have to remove it again.
1 member likes this
by Bustednukel
Hey, MARK!!! yes, of course it has to be balanced. If not then all that work and it shakes and can't rev. This is all on your 71 A65 FS motor that you sold me. I know you had that Trumpet out by now, hold it down to 90. On the plug affecting balance, nothing a little flywheel cut wouldn't correct, Rather use the oem style with the right size thread. I am guessing that some of the plug removal problems are due to mismatched thread.
Drive safe!
1 member likes this
by Allan G
Allan G
One thing I hate to see on a crank is multiple punch marks from trying to lock the sludge trap plug. One nice thing about the modern hex plugs is you can punch the plug so that it fills the existing punch hole which are often drilled clean.

John Healy did a great article on sludge plugs.
1 member likes this
by John Healy
John Healy
was that yours, John?

1 member likes this
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