23 replies to this topic

[finch661]

http://www.theminifo...x...3866&st=165 <== for retro_10 project page with vizard mods

awesome project mate... loads of ideas now
still unclear on what to do with the piston though?

Edited by finch661, 19 June 2010 - 10:40 PM.

[Dave33]

I've done the spindle mod, but differently.

Mr Vizard says to slim it down, its quicker to cut the top half (thredless half) away and file it down flat. Takes 1/8th the time and give the same results. Makes the carb much perkier but you will need a new needle.

yep this is how i did it,and finish with a fine file,also make sure you loctite the butterfly screws in.
Never had any probs with idle,sounds like butterly not closing as far as should,the spindle has no effect on idle it merely supports the butterfly.
is all you got to do to piston is put a chamfer on either side,not much,the vizard book explains what angles,as long as its close it will help ,
but it wont make an awful lot of difference,
read the section a few times to fully understand whats needed,
hth
dave

Edited by Dave33, 19 June 2010 - 10:47 PM.

[finch661]

I've done the spindle mod, but differently.

Mr Vizard says to slim it down, its quicker to cut the top half (thredless half) away and file it down flat. Takes 1/8th the time and give the same results. Makes the carb much perkier but you will need a new needle.

yep this is how i did it,and finish with a fine file,also make sure you loctite the butterfly screws in.
Never had any probs with idle,sounds like butterly not closing as far as should,the spindle has no effect on idle it merely supports the butterfly.
is all you got to do to piston is put a chamfer on either side,not much,the vizard book explains what angles,as long as its close it will help ,
but it wont make an awful lot of difference,
read the section a few times to fully understand whats needed,
hth
dave

any pictures

[Petes.one]

Bear in mind that the benefit of a well skimmed spindle is really only felt at full throttle, when the butterfly is fully parallel to the air flow and doesn't itself cause a barrier.

Squaring the throat of the carb will give benefit at any throttle opening, and so will flaring the air filter side of the throat. If you are reluctant to flare the carb itself then get hold of some 6mm aluminium plate (or thicker if you can get it). Cut out a couple of pieces using a carb gasket as a template, then with the two pieces clamped together to make a 12mm thick plate use a rasp file to make a nice flare. Page 59 under ram charging in the Visard bible gives you the idea of the shape. The end result is a nice ram plate that will fit inside a cone filter. The ram plate can be highly polished too if you want to put in the time with reducing grades of wet & dry sandpaper.

Chamfering the piston's leading edge is useful where the piston still protrudes into the throat at full lift. It seems to vary between carbs. As Dave says - don't take off too much!

I've made up a few of these ram plates using a cutting plate welded to a chopped section of distributer drive of all things. It might sound odd but I run it in a drill press so it speeds up the flaring process and give a pretty clean finish. I haven't been brave enough to try it on a carb throat but it works a treat on aluminium plate.

[Pigeonto]

.
I am finding this interesting but am wondering a few questions such as the reason for doing it. Is it to avoid having to obtain a bigger carb? That would obviously gain a lot more cfm.Or does it go back to the situation of keeping the throttle size down in order to speed up the air flow. There are various figures quoted about size of carb per hp. i.e. a 44 is good for over 120hp, twin 1 1/4s at least the same, a single 1 1/4 80hp so if you arent near the cut off amount for your engine would it help.

Edited by PIGEONTO, 20 June 2010 - 08:31 AM.

[Retro_10s]

I believe it's also born through the racing scene, where you are restricted to run a control carb but are allowed to modify the internals

The CFM raise is in the region of 20-30% over the original, well worth it in my opinion. And mine certainly revs a lot easier than on a standard carb and picks up much quicker when on the motorway to overtake.

[Pigeonto]

I believe it's also born through the racing scene, where you are restricted to run a control carb but are allowed to modify the internals

The CFM raise is in the region of 20-30% over the original, well worth it in my opinion. And mine certainly revs a lot easier than on a standard carb and picks up much quicker when on the motorway to overtake.

Well you cant question results like that. Not knowing about racing I hadnt considered that aspect.
As a separate issue but related, I am getting a set of 1 1/4s ready to go on but dont have the throttle cable bracket to accept the cable where it ends at the manifold. If anyone has a picture of a fitted set it would help alot, also showing cable routing.They replace a single 44 and on first inspection the servo pipe needs to be different so if a picture showed that it would be good

[Retro_10s]

Please start a seperate topic for you question regarding the twins.

thanks.

[finch661]

i am planning on carrying out some of these mods to my twin hs2's when i finally get round to fitting them.

so i am going to file down the throttle spindle (as mentioned above), and file down the piston. any help on how to do the piston?
also how will i ensure that both have the same amount of piston sanded down (if both hs2's are done?)

thanks