Bike Carbs/ Iva Emissions

[Guest alexpink]

Having failed IVA on emissions running twin Weber 40 dcoes, I'm looking at changing to bike carbs for better throttle response/mpg/tuning and preparing for potential upgrades in the future. They seem to make a decent sound, and while I like the twin Webers they just don't seem as good as bike carbs. I'd ideally get one of the danST sets (possibly R1) and can probably sell my carb setup jetted for a pinto with manifold and linkagefor the same price as a set of bike carbs with manifold.

I've read all the previous posts about bike carbs, however I have a couple of questions:

How well do they fit under the bonnet of an S7 with the danST manifold? Do they tilt upwards or would the trumpets point horizontally?

How easy are they to balance and set up(must be easier than dcoes)?

Are emissions much better with bike carbs on average? I need to achieve <4.5% CO and 1200 ppm for the emissions test.

Is there anywhere recommended to set up bike carbs near me and will they run on a pinto with standard distributor? CV47 postcode

 

On a side note, does anyone have a tool to change the valve stem oil seals without taking the head off? I think these are definitely part of the problem and need doing anyway.

Thanks,

Alex

[HAWKNORTH]

I can answer some of your questions. I swapped twin Weber 45s for R1 bike carbs for my 3A and got more for the Webers on e-bay than I paid for the R1s. Mine are on a Bogg brothers manifold and the trumpets do stick up at an angle and I had to enlarge the air intake hole in the side of the bonnet. Once they are set up they stay set up unlike the Webers that seem to need fiddling with on a regular basis. Thats the main reason I swapped. MPG is about the same. Performance is about the same, perhaps a little better. I have improved the smoothness through the rev range recently by connecting the vacuum advance pipework which involved getting four Ali branches welded to the manifold. This is all using the standard pointless type Dizzy. I don't know about the emissions as mine is on a Q plate and has the advantage of being visual only for emissions.

[cb750]

Have you had the webers set up properly on a rolling road? Once set up there should be no reason other than wear that should cause them to drift out of tune. You will still need to get the bike carbs set up on a rolling road to get the best out of them otherwise it's guess work.

 

As regards fit under the bonnet, it depends on the carbs you use whether they tilt up or not. Most need tilting up to copy the original angle that they were fitted to on the bike. Mine are fireblade carbs and tilt up on a bogg bros manifold, no need to cut the bonnet. I need to get the car on a rolling road as they are driving me mad to get them set up correctly with a misfire occurring as it comes off the slow speed circuits on to the needle and main jets. Have tried 2 sizes of jet at the moment.

[Guest alexpink]

Thanks for the information chaps. I've just fixed one of the oil leaks (with the magical power of helicoil) and upon investigation I'm fairly sure that most of the valve stem oil seals have disintegrated... Just learning things as I go....

Going to change them asap and see what happens then; the carbs are balanced and running properly and have been jetted properly for a 2.0 pinto, but I'll still need to take it to a RR for a proper set up unless I can sort out getting some bike carbs soonish. Either that or stick with what I've got, check the emissions at the local MOT centre and try to squeeze through with the webers