Norge gearbox drain plug threading

[RJVB]

Got my Norge back from the long-awaited repairs needed after last summer's get-off in Barcelona yesterday. I had the 50k service done at the same time *). The usual Guzzi-specialised mechanic was on a vacation, so the work was done by
the other mechanic, who left a note that apparently the threading of the gearbox drain plug is getting weak and might have to be repaired at the next service (plug was already holding with loctite). That seems a bit quick to me, and I never heard of anything like this before. Is this plug like the engine oil drain plug on the small-blocks? And is it true that in order to do the necessary repair one has to drop a lot of things to get access? Is this a plug that should never be tightened with a torque wrench?
Apparently they also had to re-tap the threading on one of the rear bolts holding the sump fairing ... wonder if there's a pattern here (but the guy who has been doing the work until now is very meticulate and I can't imagine him over-tightening).


*) "at the same time", that's what I thought ... but not got unless the 4 extra hours billed were for something else :-/

 

[john zibell]

Rene,

You have to work hard to damage the threads in the transmission case. The plug is an M10, the same size as the engine drain plug. It doesn't need to be very tight as the sealing washer has a rubber gasket integral to the washer (there is a specific term for these but I can't remember it right now) so I use wrench art for them. You may need to drop the exhaust to gain clear access to the drain hole. If you have a helicoil installed, have the tech grease the drill to catch filings, also the tap when cutting the thread for helicoil. Then flush the case after the drilling and tapping operation for the helicoil. to get all the pieces out. The trick will be getting the part of the helicoil out that needs to be snapped off. I usually use a fine hemostat to grasp the tang, the use a small punch and hammer to break it off. Then extract the hemostat and hopefully the tang is still held.

I've found the leading cause of damaged threads is using power tools to start the fastener. This makes it easy to cross thread and really damage things. If your technician doesn't start fasteners by hand (once started power tool is OK), find a different technician.

As for the fairing I can't really comment on that. Many of the body work fasteners can be tricky and are a bit fragile.

 

[RJVB]

Thanks, John. I'll ask about the power tools - is there a chance they're used in the factory, for the initial install? I guessed the threads in the casing would be robust, so having 2 in there that are damaged seems more something that would happen on chain production than in the workshop of an experienced mechanic, no?

Well, as long as only the exhaust has to be dropped for sufficient acces, only the lower part of the fairing needs to be removed. That's perfectly doable. The dealer/owner didn't seem to see a hurry (he's undoubtedly right that with loctite there's little risk for leaks), which would leave me time to find someone has experience with Guzzi and with helicoils.

 

[john zibell]

Thanks, John. I'll ask about the power tools - is there a chance they're used in the factory, for the initial install? I guessed the threads in the casing would be robust, so having 2 in there that are damaged seems more something that would happen on chain production than in the workshop of an experienced mechanic, no?

Well, as long as only the exhaust has to be dropped for sufficient acces, only the lower part of the fairing needs to be removed. That's perfectly doable. The dealer/owner didn't seem to see a hurry (he's undoubtedly right that with loctite there's little risk for leaks), which would leave me time to find someone has experience with Guzzi and with helicoils.

More apt to have stripped thread from service work, not from factory assembly. It is possible it was screwed at the factory, but doubtful.

 

[Roblatt]

Mine was also compromised by the dealer (2006 B11). I can only get it a touch beyond finger tight. I've been using that white plumbers tape to seal it. So far it's worked well for about 20,000 km.

I know this won't last but I'm mentally blocking it for now.

Robert

 

[RJVB]

Probably bloody hard anyway to get a dealer to recognise it's their fault...

 

[Phang]

Rene,

You have to work hard to damage the threads in the transmission case. The plug is an M10, the same size as the engine drain plug. It doesn't need to be very tight as the sealing washer has a rubber gasket integral to the washer (there is a specific term for these but I can't remember it right now) so I use wrench art for them. You may need to drop the exhaust to gain clear access to the drain hole. If you have a helicoil installed, have the tech grease the drill to catch filings, also the tap when cutting the thread for helicoil. Then flush the case after the drilling and tapping operation for the helicoil. to get all the pieces out. The trick will be getting the part of the helicoil out that needs to be snapped off. I usually use a fine hemostat to grasp the tang, the use a small punch and hammer to break it off. Then extract the hemostat and hopefully the tang is still held.

I've found the leading cause of damaged threads is using power tools to start the fastener. This makes it easy to cross thread and really damage things. If your technician doesn't start fasteners by hand (once started power tool is OK), find a different technician.

As for the fairing I can't really comment on that. Many of the body work fasteners can be tricky and are a bit fragile.

Dowty sealing washer

Phang

 

[Kevin.NZ]

I was servicing a friends 07 Breva 1100 and when I started to loosen the gearbox drain plug it almost fell out. It turned out the previous service done by a Guzzi Dealer stripped the thread and it was only held in by some sort of glue, of course they never mentioned it. We got the bike to the nearest Motorcycle Dealer, Blue Wing Honda, anyway their mechanic suggested not putting in a helicoil insert. He retapped the thread slightly bigger and inserted a Honda sump bolt which has a marginally larger diameter bolt but the head is smaller, 12mm instead of 17mm. The smaller spanner size also stops the untrained hand from applying to much torque. The cost was only about $60:00 all up and took about 1.5 hrs. From memory the cat converter had to be removed. A good permanent repair.
Kevin

 

[john zibell]

I was servicing a friends 07 Breva 1100 and when I started to loosen the gearbox drain plug it almost fell out. It turned out the previous service done by a Guzzi Dealer stripped the thread and it was only held in by some sort of glue, of course they never mentioned it. We got the bike to the nearest Motorcycle Dealer, Blue Wing Honda, anyway their mechanic suggested not putting in a helicoil insert. He retapped the thread slightly bigger and inserted a Honda sump bolt which has a marginally larger diameter bolt but the head is smaller, 12mm instead of 17mm. The smaller spanner size also stops the untrained hand from applying to much torque. The cost was only about $60:00 all up and took about 1.5 hrs. From memory the cat converter had to be removed. A good permanent repair.
Kevin

Of course he didn't want to put in a helicoil. Too much work for him. Also he got to sell you a Honda part!!

 

[RJVB]

Is there any reason why this repair isn't as good as a helicoil - if indeed the case is of the quality you suggested? It sure sounds more elegant to me (a bit like crowning a tooth rather than replacing it with an implant )

 

[john zibell]

Is there any reason why this repair isn't as good as a helicoil - if indeed the case is of the quality you suggested? It sure sounds more elegant to me (a bit like crowning a tooth rather than replacing it with an implant )

If someone down the road (2nd or 3rd owner) even needs to replace a plug, it isn't the one in the parts manual. Also the quality of the casting is just fine. The problem is shops that hire gorillas to turn wrenches instead of skilled technicians.