Author Topic: Dellorto PHM 40 pump adjust  (Read 122 times)

Offline leroy_can

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Dellorto PHM 40 pump adjust
« on: April 01, 2021, 08:08:24 PM »
  I know this has been covered many times but I just did my first adjustment ever which was necessitated when I found one pump not working and installed a new set of diaphragms. I used new rubber coupling sleeves from MG cycle to mount the carbs which were extremely tough to get on and didn't wish to disturb them while trying to accurately set the pump volume. Some say 6cc per 20 strokes and some say 8cc. Last night I watched  youtube video where some guy showed in the same Ducati manual one place where they said 4cc and another where they said 8cc. Mostly I wanted to come up with as accurate a measuring method as I could and match them up. Once matched up if I felt it was too much or too little I could then just adjust them equal amounts.
    Nothing new so far and when I show what I did maybe I'll learn it's been done before. I knew I would have to do several measurements to know where I was and didn't like my choices of how to do it so I came up with this solution. The spray nozzles have a flat side to index them so the hole points inward at the slide. I studied the way it worked and decided I could take a chance to mill a flat on the opposite side and then have them spray out the rear where it could be collected in a cup. Worst case would be scrapping a pair of nozzles but I have other bikes on standby so took a chance. It worked perfectly and of course when I completed my settings I simple removed the nozzles and rotated them back to the original forward spraying position.  As well when I was doing the L.H. carb I removed the R.H. diaphragm and vice versa so the opposite carb wasn't spraying. Considering it took 20 full pumps for each test and most were done twice to confirm readings it was a lot of twist grip action 6-8 repetitions per side and every time you put a diaphragm back in it takes another 20 strokes to get it pumping properly. Easily 500+ full rotations of the throttle. With all that repeat testing it was sure good not to try to do it with a rag in the opposite carb to catch the unwanted fuel. Plus you just need a white lab coat and you get to look like a scientist with your beaker and burette.
   In the end I went with a 4cc per 20 strokes setting which took 3-1/2 turns out on the left and 3 turns out on the right. To me that looked like a healthy spray and after a good ride I don't think I will do any more adjustments. It's a small thing to photograph but it should show what I did if you look closely.





 
« Last Edit: April 01, 2021, 08:13:07 PM by leroy_can »
1973 XLCH cafe Shovester #1
1973 XLCH cafe Shovester #2
1971 Homemade cafe '08 XB12S motor 71 CH frame
2002 Buell M2 Cyclone
1987 LMIV SE 1400 conversion in progress

Offline Antietam Classic Cycle

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Re: Dellorto PHM 40 pump adjust
« Reply #1 on: April 01, 2021, 08:39:16 PM »
Interesting post. Your procedure might come in handy when a customer's Le Mans arrives next week.
Charlie
http://www.AntietamClassicCycle.com
'69 V700
'69 Ambassador
'71 Ambassador
'73 Eldorado
'74 850-T
'76 Convert
'77 Morini 3 1/2 Strada
'81 Ducati 500SL Pantah
'82 V50 III

Offline leroy_can

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Re: Dellorto PHM 40 pump adjust
« Reply #2 on: April 01, 2021, 09:10:00 PM »
  Thanks the mod to the nozzles was quick once I made the choice to go ahead. You would know much better than me if this could be done on other Dellortos besides PHMs
1973 XLCH cafe Shovester #1
1973 XLCH cafe Shovester #2
1971 Homemade cafe '08 XB12S motor 71 CH frame
2002 Buell M2 Cyclone
1987 LMIV SE 1400 conversion in progress

Offline Antietam Classic Cycle

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Re: Dellorto PHM 40 pump adjust
« Reply #3 on: April 01, 2021, 09:46:56 PM »
  Thanks the mod to the nozzles was quick once I made the choice to go ahead. You would know much better than me if this could be done on other Dellortos besides PHMs

PHFs as well.
Charlie
http://www.AntietamClassicCycle.com
'69 V700
'69 Ambassador
'71 Ambassador
'73 Eldorado
'74 850-T
'76 Convert
'77 Morini 3 1/2 Strada
'81 Ducati 500SL Pantah
'82 V50 III

Wildgoose Chase Moto Guzzi

Re: Dellorto PHM 40 pump adjust
« Reply #3 on: April 01, 2021, 09:46:56 PM »

 

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