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reduction sleeve

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reduction sleeve

Postby robert gilchrist » Tue Aug 12, 2014 9:35 pm

hi, whats the best way to replace/take off a dellorto reduction sleeve?
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Re: reduction sleeve

Postby Dimitrios_231 » Thu Aug 14, 2014 1:13 pm

Try to cut some slots perimetrical without damaging the carb and then break it.
You need to do this to release the pressure of the sleeve.
A small flat bladed screwdriver will help to break it.
I've never managed to remove one as one piece,especially if it is a well used original one.
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Re: reduction sleeve

Postby robert gilchrist » Sat Aug 16, 2014 5:29 pm

With a very sharp thin blade knife I did what you said, cutting on the lines, then with the screwdriver broke a bit off, then the rest, took ages, but got there in the end, cheers for your help
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Re: reduction sleeve

Postby AndyVee » Wed Oct 17, 2018 9:00 am

Can I ask a basic question on Reduction Sleeves ? Like what are they for ?
I have an old Delorto Carb MA18BS5 I want to rebuild but it has no sleeve in it at present and everything sems to fit and work fine without it. Are they used to help seal connections, or reduce size to fit certain manifolds or reduce inlet size etc ?

I guess Im just asking do I need one or can ignore :?: :?:
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Re: reduction sleeve

Postby rossclark » Wed Oct 17, 2018 8:24 pm

The carb body is very soft alloy and doesn't take a lot of abuse or wear. The plastic sleeve is probably designed for two purposes

1. To prevent metal to metal contact on the manifold and wear on the carb body. The plastic should be the sacrificial part but often it has become hard and the manifold actually wears resulting in both needing replaced.
2. To provide the seal between the carb body and the manifold. The slits in each shouldn't be aligned, so that when they clamp tightens down they don't draw air.

I did mine recently, because mine was worn and the carb was rotating on the manifold causing the throttle cable to effectively shortening the cable and causing high revving issues. Getting the old one out isn't the hard part, as others have said you can break it up in situ and on some carbs if you take the slide out and look down the bore you can see a small rebate that will allow you to get a small narrow punch on the back of the sleeve and gently knock it out. You have to have accepted that you're not getting it out in one piece.

While I had it out I ran a hacksaw blade down the slots in the body as they were quite compressed.

To get it back in I had to warm the carb body and soften the new bush in hot water and then, using the jaws of my workmate gently wind it in. The plastic bush distorted quite a bit before eventually popping in straight just after the point where I thought I'd wrecked it :o :o
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Re: reduction sleeve

Postby Knowledge » Thu Oct 18, 2018 12:33 pm

I would add an air of caution here, as often the plastic bush will wear out the manifold, rather than the other way around. I agree it sounds implausible for the metal manifold to wear more than the plastic bush, but it is not uncommon.

Before you start to replace your plastic bush, have a really good look at your manifold and check for wear.
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