Carb Pumps

Carb Pump Gas squitters> Holley, Rochester and Carter carbs on North American V8's yes - Have no idea how it works on Carbed Motorcycle engines ;o)
 
chrisk said:
Not much, it?s all been posted before. Interesting none the less.

Cam is right, the factory was probably forced into using the available carbs, as to not have an old set of PHF?s on a ?modern? bike. Fashion.
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Don't blame me. I haven't commented on this thread until now.

Cheers,
Cam
 
Using FCRs on my SFQ - disconnected them from them as well - using it as a starting 'choke', via a thumb lever on the bars.

I reckon Vince's recent post about stump jumping on a trials or general dirt bike highlights the real benefit of pumps. Any of you triple owners planning on stump jumping?  :-*
 
Dellortoman said:
Don't blame me. I haven't commented on this thread until now.

Cheers,
Cam
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Well, you're right now.

I meant Paul.
Dell'Orto didn't only have Laverda to supply.

Fashion.
I don't know how I made such a blatent mistake, Pauls French accent is much stronger than yours Cam. ::)
 
I have posted my Delordo accelerator pump in a Husky way to many times, its in the search on this site. There is my Kehan flatslide accelerator pump story there as well. These gadgets have a purpose, they might not be needed a lot on Laverdas but they do have a use in a lot of circumstances..
 
I think Woody's was closer to a Bunny Hop, just a bit to much speed probably. Tony Bou would have made it look easy.
https://www.rideapart.com/articles/404688/toni-bou-trials-champion-video-home/
 
Tony Bou?s bike has probably got fuel injection, so he can't count unless he has pumper EFI.
Ah, the things you find out when you do some research on a topic. I never knew Honda owned Montesa.
https://www.motorsportsuniverse.com/blog/motor-sports-news/2019/11/honda-announces-toni-bou-designed-2020-montesa-cota-trial-bikes
Pumps on my Keihin FCRs are also just for cold starting, not connected to the throttle. It is an interesting subject, as Dellorto were pretty much the only maker of bike carburettors who fitted them until very late in the carb game, but they were common on car carburettors iirc.
 
Tippie said:
Pumps on my Keihin FCRs are also just for cold starting, not connected to the throttle.
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Do you have a separate control lever and cable to operate the pump?
Dunno about FCRs, but separating the accelerator pump from the throttle and operating it independently would take a bit of doing on a Dellorto.

Seems a bit redundant for starting anyway when there's already a choke (or enricher jet) on 99% of carbies.
 
No choke/enricher system on FCRs, there is a little plunger on the rhs of the carb float bowl for the acc pump. On mine now it is linked between the float bowls so I just give it a squirt and it does both, previously I had one unlinked on each but Quentin swapped me. As Dells have the fantastic enricher system they don't need anything else for cold starting, although there are still people who insist on giving a few squirts before starting it on the choke, like the bloke in India in that thread.
 
The main thing that Brettoni told me was that.....on hard down changing to navigate a slow corner, perhaps three or even four down changes would result in so much squirt that on exiting the corner and applying power, the motor would stutter as the float level had dropped and the gravity fuel supply had not caught up, in the wet could even be very nasty.

He also said that the "ramp" was a nuisance when racing as it cause an unwanted "resistance" and "snatch" and prevents the very closest of delicate throttle control, and by the way, have you ever twisted the throttle of his own (very different sounding) SFC???, silk, pure silk with a rotational force of about 6 grams.

CEM



 
Holy macaroni, he is doing well giving it that much of a twist for downchanges. I always blip for down changes racing but it needs just a fraction of throttle, wouldn't come anywhere near the pump ramps. I agree with the throttle resistance though, a great benefit. My FCRs are also featherlight, but also the Dells on the street bike without pump levers but cut down springs and QA throttle, nylon lined Venhill cables is also very good. On triples everything has just that bit more to work so even more benefit.
 
CLEMTOG said:
The main thing that Brettoni told me was that.....on hard down changing to navigate a slow corner, perhaps three or even four down changes would result in so much squirt that on exiting the corner and applying power, the motor would stutter as the float level had dropped and the gravity fuel supply had not caught up, in the wet could even be very nasty.

He also said that the "ramp" was a nuisance when racing as it cause an unwanted "resistance" and "snatch" and prevents the very closest of delicate throttle control, and by the way, have you ever twisted the throttle of his own (very different sounding) SFC???, silk, pure silk with a rotational force of about 6 grams.

CEM
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No way Clem.  A myth, easily refuted with a bit of basic maths.

The pumps are typically set to around 5ccm? per 20(!) full pump actuations., that's 0.25ccm? for each full pull.  Float bowl holds around 35-40(?)ccm?, could easily be more.  A quick blip may squirt around 0.1-0.2 ccm?, that's less than 1ccm? in total with 4 blips.  If that makes a difference in float level, you definitely have another problem...

I do understand the resistance and snatch in the throttle, the reason I first did away with mine.

piet
 
ah yes but, this is Brettonni we are talking about, have you ever been close up to the trackside when he is racing (not much later parading) and entering a slow corner, words do not describe, you might even wonder why the thing didn't blow up, never mind last 24 hours, and he was known to be very light on gearboxes and the most economical fuel wise, which just doesn't add up and beggars belief.
CLEM
 
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