850 Mk3 Primary Drain Plug

Mart UK

Mart UK

VIP MEMBER
Joined
Mar 11, 2021
Messages
1,188
Country flag
This question may be "how long is a piece of string"!

The drain plug hole in my primary cover has been helicoiled at some point. The helicoil is loose and starts to spin just as the plug gets to the nipping up stage. I've prevented a leak by using a thin smear of Wellseal on the plug and washer faces. I may get away with it at the coming oil change, but would like to replace the helicoil.

Is it possible to get the old one out and just replace with the new one? If so, does anyone have a view on what the size/spec of the helicoil is likely to be!? It is using the standard drain plug.
 
Mart UK said:
Is it possible to get the old one out and just replace with the new one?
Click to expand...

If the Helicoil is turning with the drain plug then the case thread must be stripped so replacing the Helicoil with an identical one is going to do the same.
Mart UK said:
If so, does anyone have a view on what the size/spec of the helicoil is likely to be!? It is using the standard drain plug.
Click to expand...

The standard thread is 1/4" UNF. Item 13;
andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk
 
Go for a solid repair type such as a Timesert, these have a bigger OD so a loose helicoil size will not be a problem.
 
Or Big-Sert.

++ BIG-SERT Oversized thread repair kits ++ thread repair kits for oversized holes, previously repaired threads oversized holes

stripped out threads, damaged threads, blown out sparkplugs, stripped thread, stripped out theads, helicoils, ford sparkplug repair, repair ford sparkplugs blew out with time-sert, thread repair problems, spark plug ford blown, blew out ford sparkplug, stripped theads, threads stripped out...
www.timesert.com
"BIG-SERT® OVERSIZED THREAD REPAIR KITS AND INSERTS

Used for threads which have been previously repaired and failed.

These kits will repair holes that were repaired by helicoil, perma-coil,
uni-coil, recoil or any other simular coil style insert that has failed."
 
When I bought my Norton back in 76 my dealer said that as I (or anyone else) adjusts the primary chain the transmission rocks back. When it rocks back the level hole will get lower. He said to look in the filler hole and make sure the kickstart return spring is half covered. Simple and easy.
 
L.A.B. said:
Easier/cheaper to just tap it oversize.
Click to expand...
I did wonder about that, I have a range of taps. I just wondered how well a wider hole will seal at the face, I guess no different to the big sert...
 
N0rt0nelectr@ said:
When I bought my Norton back in 76 my dealer said that as I (or anyone else) adjusts the primary chain the transmission rocks back. When it rocks back the level hole will get lower. He said to look in the filler hole and make sure the kickstart return spring is half covered. Simple and easy.
Click to expand...
I think you're replying to the gearbox level plug thread? đź‘Ť
 
Mart UK said:
I did wonder about that, I have a range of taps. I just wondered how well a wider hole will seal at the face, I guess no different to the big sert...
Click to expand...

You could drill and re-tap it slightly off-centre from the original hole and extend the flat face area inwards.
 
Yes, that would be a good solution. I don't have a pillar drill / clamps to hold it properly for that. I'm out at a Christmas dinner with riding mates tonight. I will see if any have the right set up.

Thanks.
 
I've never used the MK111 drain screw ever , after all you are likely going to take off the cover to do work or cleanings . I could see the need for an oil flush using it . It protrudes too much and can hit the L .H . pipe. I reversed the screw to avoid this , putting the head inside the outer cover with a good copper washer. Another option would be to aluminum weld up the hole forever. Likely not what you wanted to hear .
Enjoy.
 
You must log in or register to reply here.
Back
Top