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General Category => General Discussion => Topic started by: SED on October 09, 2016, 11:45:28 AM

Title: Changing USA V65 PHBH carb jetting advice
Post by: SED on October 09, 2016, 11:45:28 AM

Need a machinists advice...

1984 V65SP with USA jetting has a long brass sleeve that retains a short, top hat style, needle jet with some sort of plunger accelerator pump under it.  (The accelerator pump is missing on these.)


(http://thumb.ibb.co/chvHqa/DSCN3203mod.jpg) (http://ibb.co/chvHqa)


I could retrofit the correct Euro needle jet (below in the photo) except that the carb body is not threaded for it.  A 7mm x 0.75 thread pitch tap is available, but the question is - should I do it???  Potential pitfalls are that I tap too deeply messing up the height of the needle jet or that I cannot get the two needle jets to exactly the same height.  Also wonder if I can get the threads strait enough, or if there needs to be some perfect distance around the top of the needle jet where it projects into the throat. 

According to Guzziology the original top hat needle jets are too lean and recommends drilling them with a #36 drill bit which seems unlikely to get the precision needed. 

I'm no machinist, but can do careful work.  Should I do it?
Thanks,
Shawn

Title: Re: Changing USA V65 PHBH carb jetting advice
Post by: SED on October 09, 2016, 12:31:46 PM

BTW - you can tell if a V65 has the USA style carbs by the float bowl retainer. 
A deep aluminum nut will have the goofy USA style jetting.

(http://thumb.ibb.co/nfOgGF/DSCN3206.jpg) (http://ibb.co/nfOgGF)


A brass or chrome bolt head indicates the Euro style jetting that appears in the parts books.

(http://thumb.ibb.co/kq2K3v/DSCN3205.jpg) (http://ibb.co/kq2K3v)

Title: Re: Changing USA V65 PHBH carb jetting advice
Post by: Antietam Classic Cycle on October 09, 2016, 05:12:45 PM

Quote from: SED on October 09, 2016, 11:45:28 AM

1984 V65SP with USA jetting has a long brass sleeve that retains a short, top hat style, needle jet with some sort of plunger accelerator pump under it.  (The accelerator pump is missing on these.)

According to Guzziology the original top hat needle jets are too lean and recommends drilling them with a #36 drill bit which seems unlikely to get the precision needed. 

What you're calling a "needle jet" is commonly referred to as an atomizer. The "sleeve" is the pump body. The same parts are used in Guzzi Dellorto VHBs.

Title: Re: Changing USA V65 PHBH carb jetting advice
Post by: SED on October 09, 2016, 09:02:40 PM

Thanks Charlie!  probably using Amal lingo for needle jet. 

Any opinion on trying to cut threads in the carb body?