GT200 - facts and figures

[Covboy]

I'm considering a GT200 kit.

What bhp/ torque can I expect with a 42mm clubman, 30mm dellorto?

Cheers.


On another but similar subject would it be worthwhile members sharing Dyno graphs and set up details so we can see what's achievable with different kits etc?..

[burnside]

I've got a BGM clubman on mine and although I haven't had it dyno'd Richard Taylor told me I should expect around 19bhp from that set up. All I know is that it's got bags of torque, pulls really well and can comfortably cruise at 60-65 with plenty left for over taking....which are more important 'facts' than a dyno graph imo

[Lambretta Sash]

On my Gt 200 60 x 110, 30phbh with Rm clubman 19.61 hp 13.89 tq which was ok but lacked the punch i was after, but as dyno graph in scootering feature.
Fitted evo pipe modified, TT end can 21.78 hp 18.98 tq with more power low down than clubman and pulls alot better.
Dyno graphs are handy if you can read them properly, and very good tool for development work

[Train driver]

My GT kit, 60mm crank, 30mm phbh, V3 bgm clubman

[Covboy]

Thank you

[Warkton Tornado No.1]

I’ve been impressed with these kits ever since I took a brief test ride on a 186 some time ago.

Perhaps this is stating the obvious, but I think any potential owners would need to consider the point in incorporating a Clubman type exhaust.

Whilst there is currently a tendency to go that route for reasons of looking retro/original & ease of ride with many other set-ups, there appears to be no great point in the case of the GT kits.

Incorporating a Clubman type exhaust into something already ‘torquey’ is not going to make it more ‘torquey’ whereas an exhaust ‘made for purpose’ will.

Just check the results posted & you’ll see what I mean, but, I believe that those savvy with the Gran Turismo concept are well aware of this fact....

[Covboy]

That's what I was also hoping to understand-

I've got a Casa S2 42mm clubman already....I've also just acquired a JL expansion.....the main reason for sticking with the clubman is to avoid cutting my running boards....but if the gains in torque are suitably beneficial when fitting an expansion type exhaust, then I would consider it.
From 12/13lb (Train Driver) -19lb (Lambretta Sash) is a good difference.

Any other figures from similar set ups would be useful as comparisons..

[jonw]

Don't know whether this is relevant but here's my standard GT 186, 30PHBH (open), PM25EV expansion and Varitronic...

[Warkton Tornado No.1]

Post by Covboy » Thu Nov 10, 2016 1:31 pm

That's what I was also hoping to understand-

I've got a Casa S2 42mm clubman already....I've also just acquired a JL expansion.....the main reason for sticking with the clubman is to avoid cutting my running boards....but if the gains in torque are suitably beneficial when fitting an expansion type exhaust, then I would consider it.
From 12/13lb (Train Driver) -19lb (Lambretta Sash) is a good difference.

Any other figures from similar set ups would be useful as comparisons..

If something needs modification, then the expansion chamber would be my choice if possible.

Usually, if it’s a case of rerouting the tailpipe/muffler, a sprung slip joint can be incorporated for the conversion. That allows the exhaust to be ‘converted’ back again to SIII set-up.

[Lambretta Sash]

I did try with Rm clubman but found itl a bit long winded tbh, put pipe on changed gearing and happy

[johnnyXS]

Personally I am going to fit a suitably jetted 26mm PBHP to my small block Indian 200cc. but thats just a simple stage 4 block which is probably not as high performance as the GT200 you are using.
I think your idea of sharing jetting setups and dyno readouts is an excellent one. Scooterotica have something similar .

EDITED to remove off-topic text ............apologies

[dscscotty]

I wish that a 30 PHBH Carb hadn't become a standard 'must-have' size.
Everything that I have read about matching a 30mm venturi with a stage 1-4 200cc engine and clubman exhaust screams that it is too big to develop good road power and run reliably

Well myself and plenty of others have used this formula for many, many years with great success, sometimes the theory is often put into question by the practical!

[Adam_Winstone]

^... 28-30mm PHBH carbs are not the 'must have' so much as people use them because they've been found to work pretty well, are reasonably cheap and reasonably easy to set up. The fact that they are common also means that they are easy to find jetting suggestions for, which goes a long way to helping most people come up with a configuration that is reliable enough for road/rally use.

Whilst you might not need a 30mm for a reed motor that runs 360 degrees inlet timing, a 28-30mm PHBH will work very well on a 175-240cc piston port motor (less than half the time to get the inlet charge in... sub 180 degrees). Indeed, it was not uncommon to find 28-30mm PHBH carbs being used on 150s a few years ago either!

Basically, PHBH carbs work pretty well on Lambretta engines, which might explain why they were listed as an 'off the shelf' accessory by TWO-FOUR Accessories.

Adam

PS - My standard TV175 barrel, LI150 gearing, RS Clubman and remote filter iron 175 motor was very nice to ride and at least one kitted T5 rider assumed that it was a tuned 200+ motor when we ended up riding to IOW together over a decade ago

[johnnyXS]

EDITED to remove off-topic text ............apologies

[dscscotty]

Are you suggesting that Mark Broadhurst is all theory and no practical experience ?

Er no I'm not, and having known Mark for many yrs he'll understand were I'm coming from, with regards to understanding the requirements from motors with specific intended use such as touring,commuting, racing etc. I agree totally which is why each rebuild I undertake takes into account the needs/requirements of the user and factors such as port timings , compression,ign timing , pipe, carb etc are all taken into consideration.
I've got a 38mm Dellorto which this morning will be mated to it's manifold and bolted to a 67mm bore mugello cylinder, al let you know how it goes!

[johnnyXS]

scotty not looking to argue with anyone . I simply voiced my personal opinion but I see now that I was adding nothing useful to Covboys thread so I'm editing it out.
EDITED to remove off-topic text ............apologies

[Adam_Winstone]

"I've got a 38mm Dellorto which this morning will be mated to it's manifold", what manifold and from where?

I ask as it 'boils my p***' (not a phrase that I like but it seems very fitting here!) as I've bought too many manifolds over the years that were so much smaller internally than the carb venturi that it was specifically bought for. The worst example was for a min. 36mm carb which, after specifically questioning if it was min. 36mm internally, arrived and measured just under 30mm dia. and was so thin walled that it couldn't be increased beyond 32mm!!!! When challenged, the very big and widely respected dealer said that they send them all out like that (commonly supplied for the 35mm TMX or 34mm VHSB) but that I'd need a stepped rubber to suit the reduction to manifold size... WTF?! Talk about not understanding the issue of fitting a 36mm carb to a sub 30mm manifold

The above is just one example of many manifolds that I've paid good money for but not been able to use for the application it was purchased for!

Thankfully, MB get it and I've not had issue with the manifolds that I've bought from MBD, however, these are not cheap (worth it though) so I'd be interested to see what else might be out there that actually serves the purpose correctly.

Ta

Adam