LCGB Forums

Whilst dismantling my fork links, I removed the lower telescopic damper studs. I say removed, the nearside stud snapped off. I've tried to use a stud extractor, with no joy. Can any one tell me what size and thread pitch the stud is, so that I can attempt to re-tap it. Many thanks

When you say "re-tap it", have you drilled the broken stud out? Hopefully someone will confirm but I think the thread will be M6 x 1mm

Colin

If you mean the thread that screws into the fork link on the stud, then it will be 7mm.
The sizes are stated on the MB website here
https://www.lambrettaspares.com/spares/ ... p0047.html

coaster wrote:When you say "re-tap it", have you drilled the broken stud out? Hopefully someone will confirm but I think the thread will be M6 x 1mm

Colin

I am at the stage of the next size drill will be the tapping size. This is why I need to know.

Have you tried some heat and an easi-out on it?

Tap Drill size is 6mm tap size is M7x1mm pitch. Ive managed to drill out a few and clean up the thread.

On some I've had to out to M8x1.25mm and used a remade damper stud.

coaster wrote:Have you tried some heat and an easi-out on it?

I've heated it until the link has turned blue (hope this has not affected the structure) soaked in plus gas. Tried increasing sizes of extractors and felt sure they would snap off, last option is to drill and re tap. Thanks for the idea though. UV

Captain Pugwash wrote:Tap Drill size is 6mm tap size is M7x1mm pitch. Ive managed to drill out a few and clean up the thread.

On some I've had to out to M8x1.25mm and used a remade damper stud.

I'm only hoping I've been accurate enough with the drilling. Been looking online for 7mm taps, not a great choice and prices wildly various. Do you think I will get away with using a first taper and plug, or will I need a second taper?

Egee wrote:

Captain Pugwash wrote:Tap Drill size is 6mm tap size is M7x1mm pitch. Ive managed to drill out a few and clean up the thread.

On some I've had to out to M8x1.25mm and used a remade damper stud.

I'm only hoping I've been accurate enough with the drilling. Been looking online for 7mm taps, not a great choice and prices wildly various. Do you think I will get away with using a first taper and plug, or will I need a second taper?

i would say you should get away with a second tap as that's what I use, the links are drilled and tapped deeper than the stud and you are only chasing the original thread not cutting a new thread.
If it's drilled accurately most of the old stud thread just falls away.

M7 x 1.0 taps are available & they're not that expensive.

I should still have an M7 x 1.0 Helicoil kit. Tap & inserts. Could be that you post it for me to fix if you recquire an insert.

So, that can be a back up plan rather than tap to M8 x 1.25.

Warkton Tornado No.1 wrote:M7 x 1.0 taps are available & they're not that expensive.

I should still have an M7 x 1.0 Helicoil kit. Tap & inserts. Could be that you post it for me to fix if you recquire an insert.

So, that can be a back up plan rather than tap to M8 x 1.25.

Thanks for the offer. I'll see if I can get hold of a 7mm x 1mm tap and hope the drilling has been accurate. Never fitted a helicoil, although heard a lot about them.

One further tip.

Probably as much for the aesthetic, although I convinced myself otherwise, I've modified links over the years to enable the stud to be eliminated completely.

What I've done, is to tap out the standard M7 x 1.0 holes with a Helicoil tap for M6 size.

(What that does, is create a hole of the same pitch but slightly larger diameter. In actual fact, an M6 Helicoil tap is something like M7.422)

Then I selected & wound in the appropriate M6 Helicoil so that the bottom damper lug can be fitted using a High Tensile (Grade 8.8 minimum) M6 Cap Head Socket Screw with a small spacer to take up the role of the 11 mm hexagon part of the original stud fitting. I use a piece of round stainless steel bar with an M6 clearance hole central.

What this does enable, is not only the use of a strong fastener (albeit M6 both ends of the damper as opposed to M7 x M6) but also allows the damper bottom fixing to be undone & swung out of the way quickly, in the event of a tyre change whilst racing. You don't have to hoik the bottom of the damper out under any strain as it doesn't have to be come of the stud before it can be swung. I have never broken a Lambretta damper bottom fixing stud personally, but I've seen quite a few that have broken.

This system has been in use for nearly 40 years, without any failure.

Warkton Tornado No.1 wrote:One further tip.

Probably as much for the aesthetic, although I convinced myself otherwise, I've modified links over the years to enable the stud to be eliminated completely.

What I've done, is to tap out the standard M7 x 1.0 holes with a Helicoil tap for M6 size.

(What that does, is create a hole of the same pitch but slightly larger diameter. In actual fact, an M6 Helicoil tap is something like M7.422)

Then I selected & wound in the appropriate M6 Helicoil so that the bottom damper lug can be fitted using a High Tensile (Grade 8.8 minimum) M6 Cap Head Socket Screw with a small spacer to take up the role of the 11 mm hexagon part of the original stud fitting. I use a piece of round stainless steel bar with an M6 clearance hole central.

What this does enable, is not only the use of a strong fastener (albeit M6 both ends of the damper as opposed to M7 x M6) but also allows the damper bottom fixing to be undone & swung out of the way quickly, in the event of a tyre change whilst racing. You don't have to hoik the bottom of the damper out under any strain as it doesn't have to be come of the stud before it can be swung. I have never broken a Lambretta damper bottom fixing stud personally, but I've seen quite a few that have broken.

This system has been in use for nearly 40 years, without any failure.

I've often thought that it was a poor design of fastening for the front damper, why it wasn't made with similar stud fixing for the top damper trunnion. Then the whole assembly could be slid off instead of straining the rubbers. Another aside, do you have any preference to the type of damper? It was an original thin Italian damper, but I've seen various designs on retail sites.

Personally, I still use standard Lambretta type dampers on the road & track but would say that due to other factors, have not been competitive since 2013. If I return, it will be with what I have now, unless convinced otherwise. If I had cash to splash, I’d probably buy BGM, though. My rear damper is BGM.

My 24 year old son, who would be the last person in the World to blindly follow my beliefs, has tried briefly Targas & BGM. I don't believe he found any improvement over his Serveta dampers. Last year, he raced in Group Four with (kindly received) part sponsorship that was to include preparation of his own bike. It was to have been only initially with an old engine fitted with a Rapido barrel. The Mugello (or even better Rapido) upgrade never did get fitted, not due to his lack of commitment or effort, so he raced the whole season on an engine that would have last been competitive in 2008.

With an engine nowhere near the ‘state of the art’ competitive Group Four bikes out there, he was fifth in the championship, only a few points behind the leaders. In my own opinion, that is some testament not only to the size of his testicles but also his chassis.

He no longer races.

Warkton Tornado No.1 wrote:Personally, I still use standard Lambretta type dampers on the road & track but would say that due to other factors, have not been competitive since 2013. If I return, it will be with what I have now, unless convinced otherwise. If I had cash to splash, I’d probably buy BGM, though. My rear damper is BGM.

My 24 year old son, who would be the last person in the World to blindly follow my beliefs, has tried briefly Targas & BGM. I don't believe he found any improvement over his Serveta dampers. Last year, he raced in Group Four with (kindly received) part sponsorship that was to include preparation of his own bike. It was to have been only initially with an old engine fitted with a Rapido barrel. The Mugello (or even better Rapido) upgrade never did get fitted, not due to his lack of commitment or effort, so he raced the whole season on an engine that would have last been competitive in 2008.

With an engine nowhere near the ‘state of the art’ competitive Group Four bikes out there, he was fifth in the championship, only a few points behind the leaders. In my own opinion, that is some testament not only to the size of his testicles but also his chassis.

He no longer races.

I never ceased to be amazed what these little Italian runabouts can achieve. Thanks for sharing your experiences.