Converting Right to Left PHM40

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GeoffW
Mariana
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Converting Right to Left PHM40

Post by GeoffW » Sun Apr 14, 2013 4:45 am

Just wondering if anyone here is aware of what is involved in converting a PHM40A/D to PHM40A/S? I'm planning to restore these carbs and figured I might as well convert one to a leftie while I'm at it, that way I end up with a restored matching pair. Any experience with conversion out there?

Cheers,

Geoff

rwhc80
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Re: Converting Right to Left PHM40

Post by rwhc80 » Sun Apr 14, 2013 3:22 pm

Jeez Geoff,

At the risk of me looking like a Dill for the second time, just a little confused. Do you currently have 2 PHM 40 A/D's and want to make one of them an A/S ?? ( Oh, and I did read the heading this time Ha Ha !!)

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Rick
I have desmo disease, I just hope they never find a cure !!!

wdietz186
888
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Re: Converting Right to Left PHM40

Post by wdietz186 » Sun Apr 14, 2013 3:37 pm

My carbs are buried at the moment but if memory serves I think all that would be required is to drill and tap the existing bosses on the carb bodies. The hole for the mixture adjuster might be a problem if you don't get the diameter right and the depth would have to the same as the orig. hole. Plugs for the old holes would be easy to make. Or find the other person in the world with two lefties and swap them.

GeoffW
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Re: Converting Right to Left PHM40

Post by GeoffW » Sun Apr 14, 2013 3:47 pm

Hi Rick, yes I might have been a bit unclear - I have two AD (right side) carbies and I want to make one of them an AS (leftie)

Geoff

GeoffW
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Re: Converting Right to Left PHM40

Post by GeoffW » Sun Apr 14, 2013 3:51 pm

I reckon you're right about drilling the holes, hole depth and diameter will be the key, thanks for the reply. I'll see if I can find a carby wizard locally or take it to my machinist mate.

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Steve Foster
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Re: Converting Right to Left PHM40

Post by Steve Foster » Mon Apr 15, 2013 12:32 am

I'm just imagining the confusion that will ensue when someone who knows about these things sees a carb with AD on it where there should be one with AS ....
1974 Ducati 750 GT

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Re: Converting Right to Left PHM40

Post by BevHevSteve » Mon Apr 15, 2013 6:59 am

So, you want to put PHM 40's on a 750 GT? Probably not the wisest of choices there.. I'd say PHF 36 is the biggest you should go.
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Re: Converting Right to Left PHM40

Post by GeoffW » Mon Apr 15, 2013 1:28 pm

Hi Steve and thanks for your comments, perhaps I should have mentioned this '750GT' was converted to a replica of the '74 supersport model. The motor was rebuilt with new big end, sport pistons and currently has Darmah heads with 32mm pumpers. I'm restoring the 40mm carbs so that I have the option of whacking them on later - but to be honest I'll probably keep them aside for a while since the smaller carbs give the bike tractability for pleasurable riding. If I ever sell the bike I'd put the 40s on it then, or a more original matched pair if I stumble across them.
Last edited by GeoffW on Mon Apr 15, 2013 1:52 pm, edited 1 time in total.

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Re: Converting Right to Left PHM40

Post by BevHevSteve » Mon Apr 15, 2013 1:37 pm

you will need to change the intake manifold as well as the throttle cables when switching from PHF to PHM carbies - FYI
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Re: Converting Right to Left PHM40

Post by GeoffW » Mon Apr 15, 2013 1:44 pm

Re: conversion - Steve, when putting the PHM40s on, does it necessitate head mods such as widening the stud spacing and opening up the ports or are there 'bolt on' 40mm manifolds for Darmah heads still available? I seem to remember talk of alternative ways of going about the 40mm conversion but it's over 20 years since I had a bevel twin...and I'm a little foggy!

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Re: Converting Right to Left PHM40

Post by BevHevSteve » Mon Apr 15, 2013 2:06 pm

it is very difficult to find narrow spacing intakes with the right OD for PHM.....
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Re: Converting Right to Left PHM40

Post by GeoffW » Mon Apr 15, 2013 2:46 pm

Thanks Steve, I'll cross that bridge when I come to it.

Cheerio,

Geoff

wdietz186
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Re: Converting Right to Left PHM40

Post by wdietz186 » Mon Apr 15, 2013 5:04 pm

The 32mm are really more than big enough for normal riding especially if it is still a 750. Even on a hi comp 900 the 40mm were on the edge of usefulness unless it was on a race track.

garryc
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Re: Converting Right to Left PHM40

Post by garryc » Mon Apr 15, 2013 5:14 pm

Pretty sure the 40 mm inlet manifolds that were on my narrow inlet Darmah have just had the locating holes slotted to fit .
I can take a pic and send if interested.
I took the 40's off and put 32's on.
won't be until next week as all efforts are towards Bevels and Bullshit ride this weekend

GeoffW
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Re: Converting Right to Left PHM40

Post by GeoffW » Tue Apr 16, 2013 2:02 am

Bill, thanks for comments - I recall my Darmah used to pull really nicely with just 32mm carbs, so you've confirmed what I think I'll do i.e. just ride the bloody thing as it is and save the 40s for when I sell it or when my wife sells it after I die or get too old to know what the heck that green & silver motorcycle is doing back there in the shed! Actually it would be a lovely thing to leave my son when I grow too old to ride.

Garry, I'd certainly be interested in seeing pics of the slotted manifolds. One question (for anyone) - where the ports at the gasket on the 32mm Darmah heads the same size as the 40mm Darmah heads?

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