Dell'Orto throttle slides

[rogerd]

I am in the process of refurbishing a 77 3Cl.

The carb settings are someway of standard with 115 mains, AB265 needle jets and 55 pilots. But but the needles are K12 and the slides 50/1

As a starting point thought it seems sensible to revert to standard - the jets and needles are relatively inexpensive to replace and probably best changed anyway. But not the throttle slides How much difference is there between a 50/1 throttle slide and the recommended 60/2?

 

[sfcpiet]

The 50 and 60 denote slide cutaway, ie 50=5mm, 60=6mm.  The 50 slide will enrichen the mixture at small throttle openings, up to about 1/4-1/3 from closed.  This a range you will frequently be using on the road, ggod idea to get that right.  You could try the 50 slides, over-fuelling may result in poor throttle response and constantly fouled plugs.

Revert to stock 1000 set-up, K1 needles with new AB265 needle jets.

piet

 

[rogerd]

Sorry - I forgot to mention the accelerator pump levers have been removed at some point.

 

[sfcpiet]

I ran Dellortos without pumps for many years on my 3C, very high-strung engine though.  My RGS has pump volume reduced to the bare minimum, still quite happy with performance (and comsumption ).

Pump removal reduces throttle effort ernormously.  The number after the / denotes pump actuation ramp.

Pump has no great effect when opening throttle slowly, slide cutaway does.  Pump should not be used to disguise slide/throttle shortcomings.

piet

 

[phil37]

I've often modified slide cutaways/backdrops to a larger (or smaller) number. To make a 50 into a 60 - I have used a half round file of as near to the slide diameter as possible to take 1mm evenly off the cutaway. I hold the slide in a vice between two pieces of wood scalloped out to hold slide firmly without damaging it. Not everyone's idea of how to do it - you do this at your own risk - but has always worked for me - especially on a 600 monty that had all its low end problems cured by making "55" slides!  I now take the easy way out and use my milling machine when I have to do this job. To make a 60 into a 50 the backdrop can be turned off by 1mm in a lathe - never filed it off - but could be done if your skills are good!
  Years ago Slaters threw out loads of "50" slides into their skip when the Jaramas came over with all the US spec setups - guess who had a wonderful "Dumpster Dive" that week!! - Regards - Phil

 

[Haggis]

I also fanny around with slide cutaways, a good tip to get them all the same is to use a flat surface and slide a drill bit (of the appropriate diameter) under the cutaway, as a comparitor.

You dont have to be 50 or 60, if 52.75 happens to be right for your bike - then it is right.

I use a flat surface and drag the slide over wet'n'dry, as opposed to the hand file Phil uses.

 

[rogerd]

MAJOR IMPROVEMENT!
New needles,needle jets and 120 mains. I've left the slides as they are for the time being.

Starts perfectly, idles easily and pulls way better. (As far as i can tell pre MOT, so only a short jaunt round the block).
Mot booked for tomorrow....