DeLLorto UA16S to UA19S conversion

J

Joe51

#1
#1
Thought I would throw this out there for thought. I have aquired a UA19S carb along with (2) UA16S carbs. My plan is to convert the two 16's to 19's.
I have had may conversations with DeLLorto folks in the UK. It appears that the carb body mold was the same. All internals were the same. Just need to get some dimensions comparing both and machining the 16's to 19 specs. I have access to state of the art machining.
My question: Has anyone tried this? Any feedback would be appreciated.
Regards,
Joe51
 
ATKRIDER

ATKRIDER

New Member
#2
#2
I have both as well. To be honest the 16 is more than capable of supplying say a hot rod 5HP and like you said the body IS the same. Why bother trying to bore it 3mm-just curious. The Bings I run on my 80cc 2-strokers are 17mm and they are more than adequate. A bigger carb would do no more than aggravate me trying to get it jetted to run properly throughout the entire RPM range and 2 strokes tend to be much finickier than a 4 stroke. If there is one thing I have learned is that when it comes to carburetors-"Bigger isn't always better". Since you have both than just jet them exactly the same and try them both. I would be curious to hear your results. :thumbsup:
 
J

Joe51

#3
#3
Thanks for the feedback. When I took both the 19 and 16's apart, jets and atomizers wer the same number. Only the 19 has that adjustable high speed set up that Rupp used. The folks in the UK told me it would not get the same performance of a 19. Just going by what they told me. I picked up the 16's real cheap so I am going to mess with it in the tool room. Just to see.
Regards,
 
ATKRIDER

ATKRIDER

New Member
#4
#4
Either carb WILL need the adjustable main. Even the stock jetted 16 is too fat without being able to tweek the main down. Been there. The hardest part is probably going to find those adjustable mains and the odd 19 float bowl. I know they are out there-just pricey.
 
J

Joe51

#6
#6
Hello,
I never pursued it to the end, but still have the carbs. It is doable in my opinion. Inside the bore of the carb is a brass bushing that has to be removed before boring. Then replaced afterwards. I have confirmed this step. That works. My guess, if chucked in a mill or lathe and a reamer of the right size is used it would be a quick process. I can send you a bare 16 carb if you want to try it.
Regards,
Joe
 
C

cfh

Well-Known Member
#7
#7
I put a Dellorto ub22s2 on my MTD with an HS50 motor. It works great! i think i got lucky though as i didn't have to re-jet the Dellorto, it worked as i got it. No high speed adjustment jet either (nor is it needed on this one.)

 
delray

delray

Well-Known Member
#8
#8
ok joe,sounds like a easy process to modifly one of them for the bore size. also a question for you. what other size carbs can be modified like that? can the 17 and 18 get the same treatment. also on the main jet can any of the dellorto carbs get change over to a adjustable main.
for example a factory 22 for a rupp H50 motor. I know very little about these carb's . never done the research on them....yet.
thanks....
 
R

ruppking

Active Member
#12
#12
delray said:
thanks for that info. can you specify what parts need to be change over and can we post any good diagrams of the parts...:thumbsup:
Click to expand...
Here are the parts needed to convert a "U" series Dellorto carb to an adjustable high speed jet:
• #17651 DELLORTO HI SPEED JET SCREW UA19S
• #17652 DELLORTO HI SPEED JET HOUSING UA19S
• #17653 DELLORTO HEX NUT FOR HI SPEED JET HOUSING UA19S
• #17654 DELLORTO JET #68 - UA19S
• #18177 DELLORTO O-RING FOR HI SPEED JET HOUSING UA19S
• #18474 DELLORTO JET #38, UA19S
• #18475 DELLORTO ATOMIZER #260 - UA19S
Your carb may have some of these parts, so check the numbers stamped on the jets or atomizer.
The 0 degree float bowl is also used. It is hard to find and can be expensive to buy.
These parts are currently available at BWMS, with the exception of the float bowl.
 
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C

cfh

Well-Known Member
#15
#15
Thanks!
i re-ordered the list to follow the diagram better, and added reference numbers as shown in the picture above. And added links to buy at Black Widow MS.

• #17651 DELLORTO HI SPEED JET SCREW UA19S - #39 above $10.00 #17651
• #17653 DELLORTO HEX NUT FOR HI SPEED JET HOUSING UA19S - #38 above $2.50 #17653
• #18177 DELLORTO O-RING FOR HI SPEED JET HOUSING UA19S - #37 above $1.00 #18177
• #17652 DELLORTO HI SPEED JET HOUSING UA19S - #36 above $40.00 #17652
• #17654 DELLORTO JET #68 - UA19S - #35 above $15.00 #17654
• #18475 DELLORTO ATOMIZER #260 - UA19S - #33 above $26.00 #18475
• #18474 DELLORTO JET #38, UA19S - #32 above $12.00 #18474

total cost for conversion... yikes... $106.50... cost without jets $80

Another alternative, at $65, is this... but i'm not sure it gives you everything...
http://www.guzzino.com/deubadmaje20.html
 
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J

Joe51

#18
#18
To all. From my measurements on NOS UA16S/UA18S & UA19S it boils down to honing the carb ID ( from air cleaner mount) to intake mount. When I say intake mount, there is a shoulder behind where the intake insert installs. Honing from the back side up to that internal shoulder should convert the above UA's that I mention. They will accept all UA19S parts for the Rupp BW. This was all I was looking at and talking with Dellorto UK on. Cannot talks about the UB series. Recently sold one of my UA19S carbs using NOS parts I have had or repo parts from BWMS.
Those parts were top notch in my opinion.
Hope this helps.
Joe51
 
C

cfh

Well-Known Member
#19
#19
As a follow up to this thread...

I put a Ua16s and a Ua18s on a pair of Tecumseh HS50 motors. The both worked *great* (without any jetting change.) I also have a Black Widow with a HS50 and a Ua19s carb. To be honest, you just can't tell any difference in the performance. The 16mm carb works just as well (and powerful) as the 19mm carb. In fact, i would echo what someone said above.... the jetting seems easier to deal with on the smaller 16mm carb than the 19mm dellorto (which has an adjustable high speed jet).
 
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