LCGB Forums

I'm trying to set up the idle on a VHSH 30 flatslide as the 60 pilot fitted as standard is far too rich and have ended up with a 37 at the moment.I've emailed Eurocarb for advice regarding the emulsion tube that is fitted before the pilot but not received a reply yet and have spoken to a well known tuner who could offer no light on the subject. The emulsifiers I have are B48 ,B62 and a CD1 but none of then seem to alter much so have removed and just run the pilot but even on a 37 I have to have the airscrew nearly all the way out but at least the motor isn't as rich as when the tubes are fitted.Anyone have any advice?

As far as emulsifiers go, on VHSB’s the choice was/is dependent upon whether the engine is piston ported or reed valve. I can only imagine that the VHSH would be similar in that respect.

I would have to check 'what’s fitted where' by checking what I have, but this response might point you in the right direction or jog a few other Forum readers into a reply....

BTW. Again, on VHSB's, there was often the need to be down in the 30's with the pilot jet.

what idle speed are you running at ? if you have set it high then the engine will be drawing fuel from the progression port emulsion tube and likely be too rich at idle
The idle circuit should consist of just the slide cutaway, air mixture screw and pilot jet, nothing else.The emulsion tube plays no part whatsoever in the idle circuit

Try setting a lower idle and then reset the air screw. As I understand the VHSH30 carb you should be screwing the air mixture screw out for a leaner mix (more air) and screwing in for a richer mix (less air)

I know nothing about your VHSH30 carb but if you have no air leaks and adjusting your pilot jet and air mixture screw mixture does not achieve the correct idle mixture then you need to look at your slide. I am sure that you can buy different slides for this carb. To lean the idle mixture you'd need to be looking at a slide with higher cutaways than the one you have fitted

Oh dear! Again...

Opinion varies regarding the emulsifier.

As has been said, some appear to believe that it has no effect & may well advocate its removal. In fact, years ago, many of us removed it on race, piston ported engines.

On the other hand, others recommend that they remain. Amongst them is Mark Broadhurst that says as much on his websites.

Indeed, it may be the case that the emulsifier may be utilised in place of the traditional pilot jet, rather than augment it.

My experience is that the default emulsifier tends to be the CD1 which may be restrictive, but that’s not to say a more appropriate emulsifier should not be utilised.

Consider its function similarish to the atomiser in the main circuit which should be just big enough to be unrestrictive with the final control left to be served by the main jet.

I hope that makes sense as I attempt to answer the question you’ve actually asked....

Thanks for the replies, the CD1 has the largest drilling compared to the B's but if any are fitted with the 37 pilot the mixture has to have the airscrew fully out otherwise the motor smokes and spits out oil from the tail pipe and eventually stalls. When riding with the throttle just open or on the overrun it 4 strokes and makes the motor snatch. It goes a lot better without the tube but I was worried that a 37 pilot is too small for a TS1 250. Coming down to a 266 atomiser has made the motor easier to ride at town speeds but I now get pinking as the motor gets into the power so I need to experiment more with needles and main jet as well as retarding the Varitronic a degree or so.A weaker slide, 55/60 would be good to try but at £60 ish not cheap especially if they make no improvement,as apparently I'm a tight c**t who likes to moan.

VHSH slides can’t be that much different to the normal numbering in Dell’Orto terminology.

They range from VHSH 30 BS & CS to VHSH 60 BS & CS so I would have expected you to be in the 40 to 45 range....

Carb came with a 50 fitted but as you know they're not as easy to alter like a PHBH or the bigger VHSA's. Tried another K needle today that has eliminated the pinking but at 44 mm on the taper its just slightly too long on the too clip so have ordered a 42 and 40 mm which hopefully may cure the 4 stroking at just open throttle.

You may manage a work-around with needles, but that’s unfortunate luck.

Most slides are easily modified from low numbers to higher (weaker) but the other way is not so.