I want to upgrade my carbs, I am on 36mm bike carbs at the moment.
im not sure wether to go down the weber route or go for bigger bike carbs.
I want to upgrade my carbs, I am on 36mm bike carbs at the moment.
im not sure wether to go down the weber route or go for bigger bike carbs.
a lot of rolling road operators will tell you that although they will make the power, differences in who bike and car engines respond to throttle openings mean they often are not great at lighter throttle openings, and linkages often loose stability when the carbs get spaced out making for poor drivability.
I considered Webers for my Zetec earlier this year. But for me it would have cost a LOT more, what with moving the battery and buying a Milton pedal box to relocate the master cylinders. Apart from that I didn't want to be getting just 20 MPG which is what I've been told I'd get with Weber 45s. I've got ZX6r carbs fitted now and get a consistent 30 mpg no matter how I drive it. So I'm happy with that. Also, I read that Webers go out of balance a lot. I don't have any experience with side draughts, but that seems to be a common complaint.
Webers do sound better though, apparently.And getting them tuned up on a rolling road should be a lot easier as some places don't like bike carbs.
I'm pretty sure its down to understanding. Bike carbs have been developed over the past 30-40 years into seriously accurate fueling devices - not as good as EFI but getting close. Side Drafts are in the stone age in comparison but easy - fixed choke & a few jets and that's it. A bike carb has constantly variable choke, jets (probably as many as a Weber) a needle - which needs to be correct for accurate mid range, slide lift springs and air vents etc.
From what has been said above I would speculate no one really sets up a bike carb combo correctly relying on a std. setting for the idle and just jetting for WOT then the drivability suffers due to lack of attention!
Here's a link comparing 45's to a set of 40mm R1 Bike carbs by Jason.
http://www.turbosport.co.uk/showthre...ty+or+port+job
I have the R1's and they are great.
Cheers
Matt
I'm debating this very quandary at the minute, so more tried and tested opinions please guys.
It's my understanding that the progression with Bike Carbs is much better due to the CV design whereas webers / dellortos rely on the various size jets to tune out any issues. Both work well if sorted properly but the bike carbs are more forgiving and easier to set up plus cheaper too if you can make the manifold yourself.
For anything up to 170hp the bike carbs are ideal but for a peak power race engine then 48 dells or webers are the way to go.
Cheers,
Matt
Good analogy above I would say, the fact is that most people buy webers off ebay , bung them on and complain that they arnt great.
An engine if set up properly will use what fuel it needs if on one type if carb it gets 30mpg and 20 on another the carbs that give 20 are not set up properly.Originally Posted by DBrown67
I considered Webers for my Zetec earlier this year. But for me it would have cost a LOT more, what with moving the battery and buying a Milton pedal box to relocate the master cylinders. Apart from that I didn't want to be getting just 20 MPG which is what I've been told I'd get with Weber 45s. I've got ZX6r carbs fitted now and get a consistent 30 mpg no matter how I drive it. So I'm happy with that. Also, I read that Webers go out of balance a lot. I don't have any experience with side draughts, but that seems to be a common complaint.
Webers do sound better though, apparently.
yup im pretty much in agreement with that, although i will add that because sidedrafts use accel pumps to richen mixture they will tend to use more fuel if the driver is a throttle blipper
My old man used to get me into trouble years ago for being a pedal pumper when pulling away with his xflow, pointless he said, your just flooding it and wasting fuel!
yup, i never understand why in race paddocks people blip throttle to warm the engine, i simply hold the revs at around 3K, makes much less noise uses less fuel and is kinder to the engine
Both will require tuning. It depends on your abilitiy or your local tuners confidance with either setup. If they are familiar with tuning bike carbs this set up can be more cost effective.
Right, so for competition use not day to day driving...
Would 42mm blackbird bike carbs be best
Or
Twin 45's
Cheers lee
Read the link I posted above to answer your question. Jason spent a lot of time flow benching the difference of a 45 vs a 40mm R1 carb.
Cheers,
Matt
old SU carbs are more or less following the same princile as bike carbs...but SU´s are much easier IMO
have you ever thought using them instead?
su's cannot be used one carb per cylinder, which is why you never find more than two on an engine or 3 if its a straight six
thats true, 1 SU is feeding 2 corrosponding cylinders (1-4, 2-3), but the working principle of SU´s is similar bike carbs.
another advantage of SU´s against webers: fuel consumption is usualy lower.
About fuel consumption an SU's. This something I must agree. If setup right they can run pretty lean compared to Webers. And drive flexible. As a matter of facts, most can't get there needle right have several lean spots but you just don't feel it.
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