Bike Carbs Or Stick With Webers?

[richardm6994]

Hi,

 

I'm new to this forum, but I'm certain old school when it comes to RH's. I'm running a 2.1 pinto which I built from new components approx 6 years ago as a seperate project after I'd finished the exmo. There isn't much that hasn't been done to the engine.......big valves with bronze guides, ported, Kent FR32 cam, combustion chambers equalised, bottom end balanced etc...etc...

 

I realise that the money I've spent on this engine, I could have bought a duratech or a V8........ but being honest because the expense has been in little chuncks of money over the years it doesn't hit the pocket quite as hard!

 

Okay, back to my question.........I'm in the process of installing a megajolt system and I'm being told by people that I should ditch the twin Weber 48 set-up I'm currently running and install a set of bike carbs?

 

I'm sure I could sell the 48's and get enough money to buy a bike-carb set up so this isn't about cost, it's more about wether or not it's worth the effort???

[Guest Alan_builder]

Hi Richard,

 

I am not sure where you have been reading, but what you have posted is .......

 

I am an injection man, so both options you quote are alien to to me. But ...

The power out of any engine depends on its ability to burn an optimized air fuel mixture, the quantity of the optimised air fuel mixture is determined by the suck of the engine and the restriction of air fuel mixing device.

So a pair of twin choke webers should be as good as a quad set of bike carbs, that is if the choke size is the same and all the other bits are equal. However the biggest point is either must be set up for optimum. As an Injection man that is done for me by the electronics and not left to chance by a preset system.

 

In truth injection wont produce more power than carbs on the day the carbs were set up, but the injection system will always have more power the following days until the carbs are reset.

 

Are you sure those telling you to change just don't want your webers?

[knights_templar]

Hi

 

would agree with Alan_builder.

 

stick with what you have or go FI

 

Regards

[richardm6994]

Thank you for your replys. I agree about the fuel mixtures being correct etc... but what I've been told about bike carbs is that you get better throttle response etc....

 

My gut feeling is to stick with what I've got, however why do bike carbs seem to becoming ever more popular given there isn't really any cost advantage?

[Guest jasonmorris]

Hahahaha here we go again bike carbs versus Webers. Do a search of previous posts for loads of information on this subject.

 

By the way, My engine is a very similar spec to yours. I swapped to bike carbs years ago and haven't looked back since.

 

Rgds,

 

Jason

[richardm6994]

hey jason, what differences did you find?

[steve in stockport]

Bike carbs and webers do the same job, neither will provide more power on a like for like choke size, bike carbs may give you smoother tickover, better pick up, perhaps more mpg and stay in tune longer.

If you're going to change and money isn't an issue then the next step for you is fuel injected throttle bodies and 3d mappable ECU

[Guest mower man]

Having a foot in both camps i.e I A.run aWeber 38 dgas and am happy with it ,but like the idea of both bike carbs ,weber twincarb set ups and injection I think it.s down to depth of pocket and the type of use the thing gets.Many will say that the DGAS is crap I get a regular 30 mpg and as much perf as I want ,Bike carbs are impressive in both response and power , Webers look correct and sound nice,give good power but lack a little on economy, Injection on a pinto ,if it was throttle bodies and an ecu set up yes but the price stops me !. As to the op set up , its probably great for track days but unless choked back to 38 's max twin 48 dcoes will feed a rover v8 so to me it's over carb'ed ,but if you like it stick with it as I 've said before on here I doubt this will make the choice any easier ,it's the ramblings of a limited finance old schoolhoodie mower man [mick]

[speedtripledan]

My pinto was efi untill i converted to bike carbs power gain over efi was approx 12bhp better responce nicer .. to drive and they are still running strong several yrs later with the ocasional balance.

[Snapperpaul]

48's are for a very high reving very long duration caned Pinto.

If set up properly with 38 mm venturies you should be ok but bike carbs will be much better at idle, lo and mid range with better pickup and fuel economy.

[Guest jasonmorris]

Hi Richard.

 

The bike carbs seem much smoother in the lower rev range, with a faster pick-up from very low revs. As for economy, I find that they're not much better than weber`s but that`s probably due to my heavy right foot .

 

I am currently looking to upgrade to either megajolt or bestek ignition and a wilder Kent RL31 or GTS2 cam which should see me past the 180bhp mark. After fitting these I have been informed that the bike carbs will come into their own because they have much smoother pick-up while off cam.

 

I went for the ZX9R carbs (the later ones have tps for megajolt already fitted), and they have 39mm chokes as standard. I won them for £30 on the Bay and enlisted Bogg Brothers to clean and jet them and mount them on one of their ally manifolds. One little thing to be wary of if you do get a Boggs Manifold is that they are made from 6mm ally which can warp under high temperatures (this happened to mine) causing water to leak out of the water jacket and into either number two or number three cylinder. A quick fix was to use plenty of gasket goo when fitting as many people don't even use a gasket for the inlet manifold.

 

In four years they have never gone out of tune and have never needed tweaking during rolling road set-up. In fact the only thing that has gone wrong was one of the rubber diaphragms came unseated causing the engine to run on only three cylinders. Again it was a simple quick fix of remove carb top, remove diaphragm, slight bit of grease to create a seal and fit back together. Worked perfectly ever since.

 

If you need any further info just ask, there are loads of us on here with bike carbs and I know that many have made their own very good cost effective manifolds that work perfectly.

 

Rgds,

 

Jason

[richardm6994]

hi Jason.

 

Many thanks for your response. The twin 48s have been choked to 40 so I guess bike carbs choked to 39 will be very similar in engine power, but with the advantage of the faster pick up which is what others have been telling me.

 

Thanks again for the advice

[Guest jasonmorris]

You'll have to excuse my lack of technical knowledge, but from what others have said, I gather that bike carbs have variable venturi whereas webers have fixed venturi. I think it is this fact that gives you faster, smoother throttle response from lower down the rev range, especially if using a high lift cam in a tuned motor as you are.

 

Jason