Loctite 28654 Thread Repair

[Colin Wilks]

Helping my son fix up an old Aprilia Pegaso motor bike so this is not directly relevant to Sevens, but may be interesting nonetheless.
The steel M18 x 1.5 sump plug has slowly removed all the threads in the aluminium sump of the bike over the last twenty seven years.
I am happy with helicoils, but the location of the hole makes lining up the tap and driving it in perpendicular to the sealing surface pretty challenging. There is no load on the plug other than that needed to seal the copper crush washer, recommended torque is 20 ft/lbs.
I am considering buying Loctite 26854 "Form a Thread" which is a two pack product designed to reconstitute stripped threads in situ, using the male thread to mould it against the stripped hole. The plug is drilled for wire, so I will be wiring it after installation, which means "giving it a nip for luck" is unnecessary, although of course this is exactly what all the previous owners have done over the years.
Has anybody on the forum any experience of using this product please?

[Chris KC]

Sorry, I've no experience of the product Colin - it may be terrific.
The thought of losing the sump plug on a motorbike at speed though does not appeal. 

For my money, if there was room available, I'd look at tapping oversize: 13/16 BSW/ BSF, 1/2" BSPP or 7/8 UNC all use a tapping drill around 18mm.

Helicoil by all means but I'd take care to seal it in place.

I realise tapping it may be a challenge. Last time I had to do something like that I held the tap vertically in a pillar drill chuck and clamped the workpiece up at the correct angle on the drill table, then rotated the tap in by hand. Keeps it nice and true. Sorry if teaching to suck eggs.

[Stuart Giles]

Agree with Chris, there's not only the risk of wrecking the motor if the plug drops out, but getting oil on the back tyre at speed could lead to a catastrophe. I have done a M18 to 1/2" BSP sump plug repair on Sue's Fiat Giardinera. The tapping drill for 1/2" BSP is a shade over 18mm at 23/32" but you don't need to have the drill bit in any kind of machine if you're tight for space:



Neither do you need to use a tap wrench if there's no room for one:



You can get a 1/2" BSP flanged Brass plug from Screwfix or your local plumbers merchant for less than a couple of quid. And lockwire it of course.

[circeonya@hotmail.com]

When I removed the dynamo housing to get at the front block to crankcase nut I discovered the thread for the long bolt going into the crankcase was stripped. Because it would be almost impossible to helicoil without swarf getting into the crankcase I decided to try the Locktite option. As the thread had been stripped for some time and the joint was not leaking I reasoned I might be able to gett away with only light torque on the bolt. The Loctite Thread Repair is not available in OZ. So I obtained some Locktite LB8801 Silicone Lubricant and JB Weld (not the quick set version) then set about experimenting with a nut with the thread drilled out and a bolt. I found I could produce a reasonable thread in the nut and tested it to destruction. It took nothing like real thread torque but because there was no leak with a stripped crankcase thread before I might be able to get away with this type of solution. I used Permatex Seal a Gasket on the joint and ressembled only using fairly light torque on the offending bolt. To date all is well. I would certainly give it a go with a sump plug and in your case you still have some of the original thread available.

[Colin Reed]

Hi All,

Regarding Lockwiring Any one doing this TAKE a Good Look At Stuarts Last photo as this is the correct way the bottom wire on the brass plug is in tension so will not undo

Colin
 NZ

[Colin Wilks]

Thanks for the feedback. The lack of any endorsements has confirmed my view that the Loctite stuff is unlikely to do the business in such a relatively large and oily through hole.

There is no decent reference surface against which to judge the angle of the drill and tap for helicoiling so we've settled on this, which should provide a permanent fix if the thread is straight. 

https://www.ebay.co.uk/itm/OIL-SUMP-GEAR...890.l49292

More expensive than a brass plug from Screwfix, but not given that I don't have the tooling to hand to drill and tap for BSP.

[Steve Jones]

I think I've got the kit for tapping BSP, Colin. Happy to lend if it helps. If so, give me a call.

Steve

[Colin Wilks]

Cheers Steve, but the boy has already spent his money, so we'd better make use of it!

[A G Wood]

If you've got access to a lathe, Colin its well worth turning a guide bush for the tap [similar idea to a drill guide] and try to seat it on the washer face to help keep the tap square. There looks to be a lot of lead on that eBay tap so you mightn't have to do any drilling.  Also, further to Stuart's tap turner it's also possible to drill out a suitable sized nut and press it onto the squared end/silver solder it onto the squared end and use a socket which makes it slightly easier to get everything square, especially if you can get a tee-handle on there.

[Colin Wilks]

Good thought. I made up a guide bush out of 2" round aluminium when drilling the Seven block for helicoils. I could make a tube up to do the same thing for this tap, but the sealing surface is only a few mm across and surrounded by random bits of crankcase casting. The attraction of this solution is that I should be able to start the tap without drilling first and just eyeball the thread of the tap to keep things straight.