Sherpa 199b Bing Carb?

[old trials fanatic]

Now i know there has been a bit of talk on here about different carbs etc. Well my 199b has a Mk2 amal fitted instead of the std Bing and as i am trying to get it sorted with a view to using it in twinshock trials then i was wondering about the carb.

Rang Bultaco UK today and asked about the bing they show on their website but they havent got any in and have to order from Germany plus were not sure of the price but said it would be more than on the website.

So what do i do ? Anybody had any experience of using alternative carbs on 340 Bultacos?

Dont mind spending money but havent got a lot left after the James build so need to spend it wisely.

To my mind the options are:-

1. Stick with the Amal Mk2 = easily available not too expensive etc.

2. Bite the bullet and get a new Bing.

3. Keep an eye on e bay and buy a second hand Bing and refurbish it. But what model Bing do i look for?

4. Fit a Dellorto, Mikuni, TK etc etc but what jets to use??

I would sort of like to stay original as the Bultaco will never be as competitive as the Majestys Fantics et al but i just love riding it So i am tempted to go the Bing route but i am open to suggestions.

Cant afford to spend money needlessly though and not sure what second hand Bings are like for wear plus IKBA about Bings so not sure of the model or choke size, slide, jets etc etc.

Runs ok on the Amal very soft power delivery but cant help thinking it might be better with a Bing or other carb fitted.

What does the panel think?

[woody]

I'd probably wait and see how the bike runs on the Amal first before moving to try another carb. As far as I understand it, the 340 does have a softer power delivery than the earlier 325 bikes. I have tried both Nick Shields and David Braithwaite's 340s recently and both have soft delivery, one has a Mikuni, the other the Bing. One was a tad cleaner off the bottom but may be due to set up rather than carb type.

Personally, I wouldn't entertain the idea of a used Bing as it may be worn out but how do you tell. If it is and you don't know you could spend an age trying to get it to run right thinking the set up isn't right when it never actually will as it is worn out.

If it runs too soft on the Amal there are other ways to quicken the power delivery. Get a second hand clutch weight and skim some weight off it (no idea how much though) and fit a 250 ignition flywheel (they're lighter) which will enable the motor to pick up quicker. Both should be available cheaply and it is something that isn't permanent if it's not what you want, just refit the originals.

Re-packing the exhaust can also make a difference to the motor's performance and smoothness. I once split and repacked the middle and rear silencers on a 325 slimline and that motor, which is completely standard is still so smooth and torquey to this day. A pig of a job but worth it in view of the way it goes.

[peterb]

Hi there,

I have a 325 based Sherpa, I tried a few different carbs and find that the best performance is with a Keihin 28mm flat slide as fitted to a Raga 300, uses the standard needle (well, ok then, a GJH - slightly different), jets and slide except I made up a 1.0mm bore main jet - must use an inline filter as this carb has no internal filtering. This carb provides great response and improved top end revs.

Next best was a 26mm DellOrto straight from a Gas Gas 250/280/300 except for a change to a 95 main jet - have set up quite a few Bultacos here with this carb, 250s and 325's - great performance but not quite as bril as the Keihin.

I also repacked the middle silencer on a 77 325 which was a bit of a job but improved response, never wanted to do it again though!

Bye, PeterB.

[jaylael]

Peter, with all due respect I have had terrible luck with flat slide carbs on non reed engines. Piston port engines do not run well with flat slide carbs in my experience. I fiddled around for ages trying different jets and adjustments on a 1978 Maico 250 and a mikuni flat slide carb. Went to a round slide mikuni to get the bike to run well at anything other than wide open throttle. Just my thoughts on it, but I'll be glad to be convinced otherwise. Maybe it were an anomaly.

[peterb]

Hi Jay,

I should add that my Sherpa is based on a 1976 model Alpina on second oversize and running a 64mm stroke for an approx capacity of 352cc, I have made a PRO reed valve block fit in and this works fine with the Keihin flat slide. I have not tried the flat slide without the reed block. Have done some minor porting work to increase the transfer port area by almost 50% in the crankcase mouth and matching cylinder transfer inlet, have not adjusted the cylinder port timing - the 325 Bultaco port timing is quite close to a Gas Gas 330/321 save for the transfer swept area being about 50% greater on the GG. Also working on a mod to fit a Kokusan digital ignition system to the Bultaco, not so straight forward!

I guess that I should try the flat slide with the reed block removed, when I get time.

Bye, PeterB.

[greeves]

Hi OTF: I can have a 28 Bing for you ready when you come to Robregordo. You can also use a DellOrto PHBH it works very good in the 340.

[woody]

Greeves, is that the full model number of the Dellorto?

Also, is it a type that is fitted to current bikes such as GasGas, Sherco etc. What size is it?

[jaylael]

That Bul sounds incredibly trick! Must run really good I imagine. I'd be interested to hear if your flatslide can work well w/o a reed. I had no luck. I theorize it was because the flat slide has less vacum area under the slide to lift the fuel at low vacum levels, such as just off idle. This Maico ran like absolute crap. Let us know how it goes. JL

[old trials fanatic]

Hi OTF: I can have a 28 Bing for you ready when you come to Robregordo. You can also use a DellOrto PHBH it works very good in the 340.

Thanks Greeves i will take you up on that. Think i had better not bring too many cloathes as i have a feeling my luggage will be full of Bultaco bits.

Edited April 16, 2007 by Old trials fanatic