Carb choice?

[wrecklessrobbie]

I am running a Rapido 200 classic
With 42mm clubman, LI 150 box 15 46 sprockets. Indian webs crankshaft with new big end fitted. Running at 4%mixture.
At present it has a jettex 26mm carb.
I am spending more time bumping, cleaning the spark plug, stands, cdis than actually riding it.
When it does run i get about 56mph and a tank of fuel does about 50 miles. Its no pleasure at all riding it. I am never sure if it will start or if i will get home.
So i am going to change the carb and its booked in for a dyno session at chiselspeed.
Any suggestions on carb choice.
They have advised the polini 24mm evolution or a 25mm dellorto.
It was suggested i could go up with the carb to 28 or 30 but would need to change exhaust.
My musings at the moment are to stick with the 42 clubman. I am not sure if the crankshaft would cope with a bigger exhaust and carb. Or am i mistaken on that.
Is anyone using the polini 24mm carb? Any feedback opinions on it.

Thank you
Robbie

[coaster]

28 PHBH would be fine with your clubman but you do need to do something about your gearing, try a 16 toth front sprocket, dyno session is a good idea

[Cav]

30mm Dell'orto with a 42mm Clubman on a 200 block is a well proven combo. Might be a bit old school but it's tried and tested. Wont do a lot for your top speed, but acceleration and general drive will be much better. Agree with Coaster that you should look at your gearing. Maybe try 17/48 (82 pitch)

[Warkton Tornado No.1]

Well, you did ask! No offence to previous commenters.....

If the crank has been assembled well, that should be fine.

The exhaust will be OKeh if you fit a large enough bleed. Over 200 cc engines that need to breath also need to exhale. You ought to be able to fit a 25 mm tailpipe to prove that. If it's a tad loud but proved the point, a silencer can be added. You may even go on to modify the Clubman further by adding a cone @ the back, but you should use shallow, longer cone angles to make the engine work in a better rev range than the stumpy 'reverse cone Clubman' so much loved by neighbour's.....

Personally, I like the Rapido, despite the slagging ithe kit received from a dealer that many of you seem extremely loyal to. It is adaptable & tough in the event of a sieze.

Select a carb that is better suited to a two stroke. That does not mean the PH range. I like Dell'Orto's but not a four stroke carb modified for use on a two stroke. If you feel safer following the crowd & must stay with Dell'Orto, then the VHS range are good. Even the old VHB's are better fitted with PH atomisers & needles than the PH's they come out of.

Having used a plethora of carbs over the years, & having anything from 30 - 39 mm bores to hand from Dell'Orto to Keihin, I even have two stroke Amal MK1's (with manifolds) just for Old Time's sake. I also have SH's for use in a museum one day.

I am not too concerned with the current fashion of going small on the venturi as long as an air filter of some description is fitted. I haven't yet worked on an even mildly tuned Lambretta down to 150 cc where a bog standard or modified air box & bellows will cope. They strangle the engine, which overheats as the result. Dire!

An adequately sized air filter preferably with a MAHOOSIVE elbow/plenum will improve fuel consumption no end, stop the engine wearing out & keep the left leg of your flares clean.

Get yourself an OKO/KOSO/Stage6 PWK 30 mm carb. Or a cheap Chinese bootleg if you are prepared to blueprint it, or know somebody that can.

I first fettled a PWK 34 mm which was fitted to an almost standard 200. Even I thought it too big @ first, but got involved to help a very old mate. IMHO, they are a revelation. They are cheap, tune easily, are very responsive, don't flood with an air filter when hot (try that with your PH's unless an escape hole is drilled. Rather defeats the point, eh Dan?) & are cheap. Did I mention they are cheap?

[Warkton Tornado No.1]

I meant to say with the above that you should get your top end sorted as a priority, then worry about the gearing later.

Get it pumping as it should & you'll soon know whether the overall ratio is wrong & derive some pleasure in needing to change.

A word of advice. Six platers of the ScootRS & CamLam type work bloody well if fitted well with good top pressure plates & springs that do not get coilbound. With ATF, naturally....

[Cav]

I run Dell'Orto at the moment but I've also tried a 30mm PWK flatslide ages ago, bought from ScootRs before they disappeared. Fitted to a Jet 200 it was truly amazing. Ultra responsive when opening and closing throttle and the pick up was instantaneous. Even better was it ran perfectly straight out of the box. I've also used a Mikuni which was very reliable and spares readily available.