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Bike carbs sizing


shizzl

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Does anyone know if there is a chart anywhere with flow rates/specs of various CV bike carbs?

Had a look over the hunter today, it sprung a few leaks of the slippery stuff on the way home, and also noticed that the throttle shaft on the carb has excessive play =no sealing left there bro.

Also noticed it's the original bock..

Keen to ditch the sloppy Stromberg for bike carbs. 

Would a set of CV30/32s do the trick?

 

Also any other crap to consider?

 

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rough and ready way would be to look at the likely power of your motor and choose carbs from a bike of similar power level

this is presuming you are using 1 throttle/carb per cylinder and the bike was as well.

another way would be comparing to side draft choke sizing for one throttle per cylinder

off the top of my head for a 4cyl this very roughly goes something like

32mm - 120hp

34mm - 150hp

36mm - 180hp

 

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http://danstengineering.co.uk/

Have a read on that site mate.

I'm running Keihen CVK's of a ZZR600 on my 1600 Escort. 

That's kind of the recommended bike size for that engine capacity. Guys running 2lt pintos generally use the bigger carbs off a 1000cc bike such as a R1.

PM me if you want any more info. Mine runs way better than it did on the Weber downdraft originally. Is going to be Dyno tuned tomorrow so I should have a good idea oj just how good it is after that. 

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Got 40mm R1 mikunis on my Pinto, runs pretty well, might go down a jet size/play with mixtures or find someone who knows what they're doing. 

RE: vacuum, I bought one of danst engineerings' "balance bars" and tapped into each intake runner from the manifold. So all 4 go into the balance bar, the out of each end of that I have one fitting going to vac advance and one to brake booster. Will try and find a pic. 

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I can make a vacation balance bar however it doesn't even have a booster in it anyway..

I'd say the servo shit it tits and seized up and someone removed it from the system, hence the hard pedal and shit brake feel.. 

I'll make my own aluminium manifold unless it works out cheaper to use mild steel.. I'll get it cut out and fizz on some tube.

 

The engine runs a mechanical pump, I would've thought that would run low pressure being only feeding a single stromberg.

It's experimental so if it doesn't work out I'll rebuild the stromberg I have a twin carb that as I've got a manifold just not a matching pair of carbs or linkages.

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FB_IMG_1526557561206.jpg

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Man I'd sketch out about having the float bowls sitting right above the exhaust manifold aye.. Make sure your gaskets don't leak! Making it out of alloy might prevent some heat soak from the exhaust runners too? 

I used the fuel pump from the R1 the carbs came off, is self regulating and quiet (mounted with rubber isolaters). 

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The vacuum doesn't work well at lower rpm, it makes the vac advance on the distributor pulse and sound like a noisy tappet, but after 2000rpm it either pulses fast enough or you dont hear it over engine noise. Not sure how it would work on the brake booster, but I imagine it would just take a while to replenish vacuum after pushing in the pedal with low rpm's but be fine at driving speeds

 

My setup was R1 carbs on 1800 crossflow motor. had a non-returning fuel pressure reg, malpassi something with a lift pump. Rot808's car has the standard mech pump on it I think. Just need to check for your setup. 

 

If they are CV carbs then you should make sure that the vented tubes on top of the CV diaphragms are blocked off or connected to each other. Bike engines can change RPM way faster than car motors so can cause some trouble if you slam the throttle. Also makes a funny flutter noise on accel not blocked off

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possibly useless bike carb sharns -

cbr1000f 38mm CV keihins, 1.6mm jets on 4age: i threw some M4 threaded push-fit pneumatic fittings (face sealing type) in to the manifold runners and wanged together a block with more fittings to feed the booster, assumed it acted as a balance of sorts and never had any issues.

in lieu of proper balancing gear just spent some time with a listening tube to set the throttles which made it much happier, never touched them again

also this:

On 14/02/2014 at 23:13, kpr said:

individual filters (that will fit in the space)  dont have enough surface area.   airbox  or filter that covers all 4  will work alot better.

 

i'd roll open throttles  or a 4k  before running filter socks or small pods

@Seedy Al make the sale!

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I ran no filter for years, then put some of those sock filters with springs inside on and I didn't notice any difference, I got the biggest/fanciest ones I could find though because I heard it may be a problem. Interestingly when engine was pulled down because I wanted to put a bigger cam in it, there was no indication of debris getting inside the engine/any damage after several years of running with zero care about dust

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The classic Ford article is a worthwhile read https://www.classicfordmag.co.uk/tech/tech-ultimate-guide-bike-carbs/

 

I welded up some dual port subbie ea81 heads for my brumby with R6 carbs,  I think they're 35mm. Original heads are Siamese. Life got in the way though and I still haven't put them on, it's been about five years!

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