LCGB Forums

Hi,
I've been running my GP200 on a Jetex 22mm carb fitted with Dellorto jets and a quality remote foam air filter for a few years now.
It's a great standard'ish motor, based on an Indian base unit with the bearings, crank and internals uprated to the better quality Italian / aftermarket options.
Running an Indian big bore clubman exhaust. ( Standard Indian GP200 gearbox ).

Its a great scooter but just lacks a bit of top end speed, tops out at about 50mph max.
It's jetted well and the plug is spot on, its reliable and good to ride, its done about 3000 miles since build a few years ago.

Would I gain anything by swapping to one of the quality Dellorto replica 22mm carbs available, swapping in the jets from the Jetex body ?
Or
Would I need to update the carb and manifold to a larger option - maybe a 25mm option ?

No rush to change a half decent set up, would just like a bit more at the top end speed so that it cruises at 50 ish rather than tops out.

My other Scooter has a bigger, 30mm more modern carb, runs well and is that bit quicker.... its does drink a bit of fuel ..... and it might be a touch large for a 185cc so I'm just trying to weigh up the options.

Any thoughts or experience of the quality 22mm carb or slightly bigger options on a reasonably standard motor ?
Thanks - jr

I had a Delortto 18 on my 175 and swapped for a Scootopia 22, to be honest I can’t remember it making much of a difference. Maybe look at a better pipe BGM, X-box etc as this will have a bigger influence on performance and a modern Delortto phbl 25 or PHBH 26.

JR
I have standard SIl 200 engine with 22mm Jetex and Scootopia clubman (all in an API series 2), does 65 mph top speed and bobs along nicely at 55mph. I still have it fitted to the original air box and paper filter. Get circa 65 miles to the tank - standard tank 8.1L.

You might want to look at exhaust options - or maybe take it for a dyno test to see why it is lacking in top end speed.

35mpg! Flippin heck.

Thanks guys !

Appreciate your feedback - I think I need to investigate why its down on speed, as it should be quicker with its current set up.
The electronic ignition seems to be bob on, but it might just need another fresh view of the set up as it - maybe its down to set up ?

I'd prefer to stick with the reliability I have rather than start a fresh with a bigger carb.

Will work on the options
jr

Hi,
I've ordered a Scootopia 42mm clubman exhaust....
It's a good quality exhaust and it seems to suit my other scooter well, so I'm going to try another exhaust as a first option.
I know the Indian big bore is well respected, but it's quite a rough and ready option. It's given good service, but it might be worth trying an exhaust swap before I get any dyno testing done. I want to stay with the standard look, so this one is the option to start with I guess ?

The Scootopia clubman does look better and its far easier to fit and work around in the longer term too.
Might need to update the main jet, but will check the plug before make any changes.

Let's see how it plays out
jr

Hi,
The new exhaust fitted a treat and the scooter runs really well. Great through the gears and is way better than the old Indian big bore.

My only issue is that it runs great until I get to about 50-55mph in top. ( speedo is running a bit slow, but about 50 odd is tops at the minute ).
It hits a "stop" and wide open the it starts to bog, roll off ever so slightly all fine again, but it hits a block in top at 50 ish.
I'm running a 22mm jetex with a foam remote filter, from memory its a 132 main jet, plug is nice and clean, brown and generally about spot on.

Before I condemn the jetex and go for maybe a 25mm or 26mm more modern carb.... is it worth upping the main jet on the present carb ?
Fuel flow looks fine, I've a fast flow fuel tap fitted. Just a thought... is it running out of fuel at the higher revs and would a slightly larger jet help ?
It's not expensive to try another jet, but its pointless if the only fix for a bit more top end speed is a bigger, modern carb.

Any feedback or experience into set ups would be cool - Thanks guys

132 main Jet there’s ur problem
Far too big 118-122 is the norm for a standard setup
Dellorto 25 phbl would be a waste of money as ur not gonna get much extra bang for buck.

ULC Soulagent wrote:132 main Jet there’s ur problem
Far too big 118-122 is the norm for a standard setup
Dellorto 25 phbl would be a waste of money as ur not gonna get much extra bang for buck.

Thanks for the feedback - I'll try a smaller main jet and give things a go - appreciate the input.
Cheers - jr

Roey99 wrote:

ULC Soulagent wrote:132 main Jet there’s ur problem
Far too big 118-122 is the norm for a standard setup
Dellorto 25 phbl would be a waste of money as ur not gonna get much extra bang for buck.

Thanks for the feedback - I'll try a smaller main jet and give things a go - appreciate the input.
Cheers - jr

It might just be that your poor performance is related to lousy compression and nothing to do with the carb or exhaust? Check this out first before spending money.

Hi,
I tried a smaller jet and the results were rough running, popping and generally not revving through the range.
So I swapped back to a larger jet and it running really well, pulling nicely through the range.
It has a remote foam filter as well as the clubman exhaust, so it will pull a bit more air through than a standard filter and filter box.

It's only done about 3000 miles and was carefully run in, it's an Indian cast iron barrel and a matched piston. Compression is good.
I know the speedo is a bit slow, so I think it's topping out in the mid 50mph's.
Checked all the electrical connections from the plug back, all good. Fresh plug and good fresh fuel. Starts first kick and ticks over nicely.

I might swap over another CDI just to rule that out, but its a low miles Ducati CDI, so hoping it's ok.

Might just have to ride slow and enjoy the view
jr

Fast n Furious wrote:

Roey99 wrote:

ULC Soulagent wrote:132 main Jet there’s ur problem
Far too big 118-122 is the norm for a standard setup
Dellorto 25 phbl would be a waste of money as ur not gonna get much extra bang for buck.

Thanks for the feedback - I'll try a smaller main jet and give things a go - appreciate the input.
Cheers - jr

It might just be that your poor performance is related to lousy compression and nothing to do with the carb or exhaust? Check this out first before spending money.

Hi, - Thought I'd double check the compression. It feels ok.... but I'm getting aprox 75psi on the standard Indian head and piston 200cc assembly.
Checked my SR175 kitted scoot and that's around 100 psi
The 200cc has done about 3000 miles, and has built to standard top end spec.
Is it a bit low from maybe worn rings ?
jr

75 psi is low. Closer to 100 psi is a tighter engine.
It may just need a set of rings.

Hi,
New rings fitted and all back together.
All up and running again - will run it in over the next few hundred miles and start to enjoy a bit more cruising speed as the miles go on

I've dropped the main jet back to 125 (as its running a remote foam filter), initial check showed a nice tan coloured plug - only done about 20 miles, so I'll keep an eye on it.

I'll check the compression later when it's all cooled down ( last pre-rings check was cold ) and I'll compare the readings. It does feel a lot better to ride already.

Thanks for your help guys.

jr

It's hard to say compression is good just from feel. You can tell if it's suddenly changed, but it's difficult to quantify properly unless you measure.

What's your squish like?

I just did a rebuild for someone and the base gasket was 2mm thick plus a thick 0.7mm head gasket. The result was about 3mm squish. I rebuilt with 1mm base and no head gasket. It feels like it's been tuned by comparison to before.

The bowl volume can be excessive too, but that's another story.

CHRIS in MARGATE wrote:75 psi is low. Closer to 100 psi is a tighter engine.

Not necessarily.
Because you are measuring pressure after the exhaust port has closed, you have to take exhaust port timing and other things into consideration when measuring static compression. On some engines 75psi would be ok.
If you measure and record your "post run in" pressure, then do it again at every major service interval, you can use these figures to work out the state and rate of the rings /piston / bore wear. which can be very useful for riders that do loads of miles every year.

I record my results after a rebuild and that is my benchmark that I can compare against at a later date.