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GP Suspension

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

GP Suspension

Postby LambrettaMarky » Sun Nov 10, 2024 7:59 pm

Looking to get new shocks and am wondering if there's much to chose between BGM or Protech?

Also - is it advised to increase the rear ride height by installing a 310mm shock?

Cheers.
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Re: GP Suspension

Postby Adam_Winstone » Sun Nov 10, 2024 10:19 pm

Watch out for longer shocks causing frame to carb / manifold clearance issues. Many engine configurations cause issue, which is why you can find lots of info online about eccentric / offset engine bolt cones. Fitting a long shock just makes this potential problem worse.
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Re: GP Suspension

Postby gizmo » Mon Nov 11, 2024 8:42 am

The BGM rear shock is adjustable anyway so you can experiment with height
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Re: GP Suspension

Postby LambrettaMarky » Mon Nov 11, 2024 10:27 am

Adam_Winstone wrote:Watch out for longer shocks causing frame to carb / manifold clearance issues. Many engine configurations cause issue, which is why you can find lots of info online about eccentric / offset engine bolt cones. Fitting a long shock just makes this potential problem worse.


Noted - Thanks for the tip Adam
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Re: GP Suspension

Postby LambrettaMarky » Mon Nov 11, 2024 10:29 am

gizmo wrote:The BGM rear shock is adjustable anyway so you can experiment with height


Both the BGM & Pro Tech are adjustable for pre-load/sag, but I didn't think they had an adjustable ride height?

I'll give Pro Tech a call.

Thx.
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Re: GP Suspension

Postby gizmo » Mon Nov 11, 2024 11:11 am

LambrettaMarky wrote:
gizmo wrote:The BGM rear shock is adjustable anyway so you can experiment with height


Both the BGM & Pro Tech are adjustable for pre-load/sag, but I didn't think they had an adjustable ride height?

I'll give Pro Tech a call.

Thx.
. The BGM one is adjustable from 300-310 mm in height
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Re: GP Suspension

Postby LambrettaMarky » Mon Nov 11, 2024 11:17 am

Spoken to the very helpful folks @ protech and will go pick up the new suspension in the next week or so.

Made to order plus I'll get to see the workshop too which is always interesting.
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Re: GP Suspension

Postby LambrettaMarky » Mon Nov 11, 2024 11:25 am

gizmo wrote:
LambrettaMarky wrote:
gizmo wrote:The BGM rear shock is adjustable anyway so you can experiment with height


Both the BGM & Pro Tech are adjustable for pre-load/sag, but I didn't think they had an adjustable ride height?

I'll give Pro Tech a call.

Thx.
. The BGM one is adjustable from 300-310 mm in height


Decided against the increase in ride height to just remove the clearance issue potential as I've fitted a 30mm carb and who knows what next. I just want decent suspension for road riding.

Appreciate the info' - thank you.
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Re: GP Suspension

Postby Storkfoot » Mon Nov 11, 2024 2:21 pm

I have had to have 2 Protech/ Chiselspeed ones rebuilt due to seals leaking. Whilst one was being rebuilt I had it altered to be S3 length from S2. The whole shock had to be dismantled and a new rod fitted.

On my S2, I have the Rob Gray/ bgm adjustable ride height shock absorber. I really like this shock, albeit only done around a thousand miles on it so far. More expensive than the Protech/ Chiselspeed ones.
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Re: GP Suspension

Postby LambrettaMarky » Tue Nov 12, 2024 10:59 am

I was swayed a little by the fact protech are down the road (ish) from my folks, so I can go collect my suspension & save a few bob plus get a cuppa with my folks..

Good to support our local economies too, even if I will collect them on my BMW!!
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Re: GP Suspension

Postby LambrettaMarky » Wed Nov 13, 2024 6:14 pm

Had a fun day today. 286 mile round trip on the GS down to see Tim @ protech. Sunshine, dry roads & it's mid November.

This is what's inside the rear shock and while I was there, got a quick look around their compact unit. The quality of the engineering is excellent as is the attention given to each & every unit build.

Imageprotech inners by KTM Marky, on Flickr

I made off with the suspension for my GP and a heap of stickers:

Imageprotech goodies by KTM Marky, on Flickr

Will repost back on the suspension, but it just has to be an improvement on India's finest!
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Re: GP Suspension

Postby jonoy » Wed Nov 13, 2024 8:40 pm

LambrettaMarky wrote:Had a fun day today. 286 mile round trip on the GS down to see Tim @ protech. Sunshine, dry roads & it's mid November.

This is what's inside the rear shock and while I was there, got a quick look around their compact unit. The quality of the engineering is excellent as is the attention given to each & every unit build.

Imageprotech inners by KTM Marky, on Flickr

I made off with the suspension for my GP and a heap of stickers:

Imageprotech goodies by KTM Marky, on Flickr

Will repost back on the suspension, but it just has to be an improvement on India's finest!


If you have an innocenti inboard disc brake the front kickstart side damper doesn’t fit.
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Re: GP Suspension

Postby LambrettaMarky » Thu Nov 14, 2024 9:44 am

SIL GP 200 - Is that the same fitment?
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Re: GP Suspension

Postby nsaints » Thu Nov 14, 2024 11:44 am

I read innocenti inboard disc brake as any internal disc brake made to Innocenti's design. So this includes after market copies (maybe?)
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Re: GP Suspension

Postby jonoy » Thu Nov 14, 2024 11:47 am

LambrettaMarky wrote:SIL GP 200 - Is that the same fitment?


Will be ok if it’s a front drum
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Re: GP Suspension

Postby LambrettaMarky » Thu Nov 14, 2024 11:51 am

Mine is inboard disc. Will have another look in a bit as I just need to open up the forks little to accept the wheel so need a jack or similar. Must have moved slightly during the new internals going in.
Last edited by LambrettaMarky on Thu Nov 14, 2024 11:58 am, edited 1 time in total.
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Re: GP Suspension

Postby Storkfoot » Thu Nov 14, 2024 11:55 am

Mark, as an aside to whether these dampers are too wide to fit, how do you have your dampers attached? Are mounts welded top and bottom?
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Re: GP Suspension

Postby LambrettaMarky » Thu Nov 14, 2024 12:01 pm

Storkfoot wrote:Mark, as an aside to whether these dampers are too wide to fit, how do you have your dampers attached? Are mounts welded top and bottom?


Yes Paul. I have the top bracket in place and the bracket for the lower mount attaches to the spindle/disc link. It had dampers on before, just that they were a bit rubbish.

The protech units are handed too courtesy of their offset mounts.
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Re: GP Suspension

Postby Storkfoot » Thu Nov 14, 2024 12:38 pm

LambrettaMarky wrote:
Storkfoot wrote:Mark, as an aside to whether these dampers are too wide to fit, how do you have your dampers attached? Are mounts welded top and bottom?


Yes Paul. I have the top bracket in place and the bracket for the lower mount attaches to the spindle/disc link. It had dampers on before, just that they were a bit rubbish.

The protech units are handed too courtesy of their offset mounts.


Those Indian bottom brackets are made of cheese. I had a set once. One snapped on me going up a steep hill towards Tan Hill. I am not alone. This has happened to many scooterists.

I suggest that, whilst you have your forks out, get a set of fork links with damper mounts welded on. Presuming that the links you have are Indian rather than Italian or Spanish, do not get mounts welded on. Indian fork links tend to warp when welded. Again, this happened to me. It took me months to realise though. I couldn’t get my head around why my front tyre was wearing out on one side. It was because, every time I braked, the warped fork link was causing the front hub to go to one side.
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Re: GP Suspension

Postby LambrettaMarky » Thu Nov 14, 2024 2:14 pm

Yikes Paul..

The links felt reasonably quality to me when I had them out & in hand although I didn't realise there was another casting with mount too. It's all new to me, so I'm learning & I guess you mean these: https://www.lambretta.co.uk/product_inf ... cts_id=761 - I will keep these in mind, thank you.

So my forks are reassembled & back in now and I've just trial fitted the Protech shocks which indeed do not fit with everything as it is.

No Problems - Only Solutions here at APE (Aldridge Precision Engineering).

I have turned down the spindle nuts to 8mm wide & removed 6mm from each end of the spindle itself which now sits flush with the nut complete with spring washer and plain washer installed on top of the lower damper link. The dampers themselves have offset mounts & the lower bush mount is also offset with a counterbore to locate on the damper mount, so nicely thought out.
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