new guy

[joe46ho]

Steve, That tank is Very rare, not that the motorcycle itself isnt. If I where you I would keep it, restore it, its a piece of history (family history as well it sounds like)
As far as jets, Guzzino is a perfectly legitimate business to order from, but does he have your jet size ? As far as I know, all the jets he sells are "blanks" which is fine... But I can make the same thing on the lathe in about 5 minutes (all his jets are is a piece of 5/16" brass hex bar, cut down and threaded on one end) you still have to drill/ream the jets to size, and if they are true "undrilled blanks" as the website says you would need to put a 3mm counterbore in them also before drilling the orifice (1.2mm in your case)... You dont happen to know a machinist do you ? even a hobby machinist could make you a handful of blank jets for a few bucks worth of brass and a little time. You could have them make you 5 or 6 in different sizes to help you get it dialed in...Everyone is going to tell you "get rid of that dellorto ss1 as fast as you can" but it will detract value from the motorcycle I can promise you that, and if you are patient you can make it run like it did when it was new (assuming there isnt anything else wrong with it) and also keep in mind when i say "new" i mean 1960's new, I think some people are just too used to riding modern motorcycles, with transistorized ignition, complex carbs, fuel injection, etc... My dad had a 350 desmo mark 3 american model (now my brother's) almost exactly like yours (minus the twin filler tank) and he always tells stories of riding it to work every warm day. So obviously these motorcycles where not that unreliable, or unrideable.

heres a couple things i hope we can clarify, which carb is on the 350 now ? reading your post im not sure if you mean you are trying to find parts to fix the ss1, and in the meantime are having trouble with the vhb not working properly or if you where having trouble with the ss1 before the jet broke ? or maybe both ? By the way, vhb parts are much easier to find for what its worth... If you are so inclined I would recommend you carefully disassemble the entire carb, and inspect everything for wear, as has already been mentioned, the slides wear, the needles, the needle jets, as well as other parts. If you are unsure if a part is damaged (its usually very obvious) try to post some good up close pictures of it. I have seen some slides wear paper thin, and nearly get holes in them. I have quite a few nos ss1 parts. most of which came from Ian Gowanloch in Australia (italsparesducati)
is his ebay id. He has a lot more than whats on ebay, or on his own website. You might be able to get any ss1 part you need from him but you will have to either call, or send a request. Either way the first step would be to clean and inspect every part thoroughly.

One last note... the standard factory size main jet for your carb was most likely a 115, not that a 120 isnt perfect but there is no way to know without testing/tuning it. thats another advantage of getting a few different sizes. Even in the factory manual a 120/122/128/130 are all listed as optional sizes...

Joe

[Magman]

The 350 has the SSI. It has had the rough running and wont idle problem since I have gotten the bike running. I took the carb apart to clean and inspect and the carb is in real good shape. I broke the main jet reinstalling it. I noticed when I took the carb off that the rubber mainfold extension was broke in half.This obviously was a big problem. Maybe most of the problem. Another issue is all of the parts that go into the choke housing of the SSI are missing so based on your last note of this causing running problems then I suppose this is the other part of the problem. So, I decided with a broken main jet and a broken rubber manifold I would take the VBH 29mm off of the 450 and try that since it was also a 29mm to see if it would fit the 350. The bolt pattern and manifold are the same so I decided to disassemble, clean and inspect the VBH. Upon reassembly I broke the choke jet right across the cross drilled holes where it is extremely weak. There were a few threads remaining so I reinstaled the choke jet and installed the VBH on the 350 anxious to try it out. It started first kick. It idled like a dream. It responded to throttle so i took it for a ride. It went several blocks and quit twice, each time harder to start. Finally it would start and immediately die so i pushed it home. The next day it started and died and repeated the pattern of dieing immediately. Thats the status as of today. I need to get some parts. I am anxious to see if the SSI performs ok with a new rubber, main jet and what ever parts I need for the choke hole..what ever parts those are. If I dont have any luck finding the parts in a reasonable time for a reasonable price I may buy the Mikuni 28mm round slide and go riding. I am a little stressed out over the 2 hole tank for milling around the patch now. I will put it away and find another tank. I have a chrome scrambler tank that was on the bike but it is rusted through the seams on the bottom both sides of the back so I dont think it would hold up to epoxy lining very long. It has the blue paint Ducati wings so eventually I will put the wings on the 2 holer.

Anybody got a line on a usable tank? ..and the SSI choke parts. What a great group of folks!

thanks
Magman

[joe46ho]

Guzzino has the choke parts as well. but again I dont buy them there... I bought about 50 cable ferrules and cable adjusters from domiracer when they where still around, for pennies on the dollar, and the pistons are a breeze to make on the lathe. the springs can be bought from mcmaster-carr and other industrial suppliers, and the last item the "cap" is usually not missing, but i have some nos ones, and these can also be made out of brass easily (what I prefer, or steel, or aluminum). I have more time than money right now, if you have more money than time then guzzino is the quick answer but the choke parts alone will cost you over $80 with shipping...
Joe

Here is a pic of what guzzino sells.

[machten]

I keep hearing how "difficult" the SS1 29 is for starting, idle and running on this forum. When I got my 68 250 desmo twin filler it had a (wrong) VHB 29 on it. I was lucky enough to get a good condition throated SS129 to replace the VHB, fitted a new slide and some new jets, learned a new starting regime, and I have to say, the SS1 is brilliant. Much bettter than the VHB at the top end with the air slide open. It will start first kick 95% of the time and idle happily after about 1 minute from cold.

My experience is that they can be made to work very well with a little bit of setup effort.

Kev

[amartina75]

either of the carbs you have should be able to make you bikes run perfectly well. I'm not sure why people refer to puting a Mikuni on a Duc as some kind of magic bullet that will solve all of your problems.
I'm also not sure why you would want a Jap carb on your Italian machine. If you could set up a mikuni to put on your Duc for $50 I would say go ahead and try it, but you cant, unless you have a whole stash of mikuni parts already. you are not going to find a mikuni that is set up to run on your Duc out of the box. you could order one from Sudco and have them set it up for you but that would probably cost you $200 all together and you would still have to adapt it to mount it to your Duc. the Dellortos you have were made for the bike you have, all you should have to do is make sure they are clean and in good repair, and set them up according to the factory settings(you can find that info in the tech section of motoscrubs) you will likely have to buy some parts, but you will most likely have to buy mikuni parts as well if you wanted to try one on your bike.
i recently took the SSI27D off of my 250 scrambler and replaced it with a VHB27AD and it runs perfectly well, pretty much the same as it did with the SSI on it but it does have a more consistant idle now. when i stop at a light now i dont have to listen to the idle and think ("is it going to die on me, it sounds like its gonna die, i better blip the throttle", LOL)
my SSI probably could use a new slide, i replaced pretty much everything but that, and you can't expect a carb with worn parts to perform like one with new parts.
one thing you should be aware of that you might not realize is the "choke" you have refered to on your SSI carb might be backwards to what you are used to. when the choke slide is in the up position it is "off" since this position then puts tension on the cable and the spring under load it seems counter intuitive. when the plunger is down it is "on" and blocking a passage way, increasing fuel.
so if you want to save some money you can just plug the choke tube and not use it at all, most people argue that it does nothing anyway, and was never meant to aid in cold starting.

good luck with getting you bikes running,
my 2cents,... my Yamaha R5 runs great with mikunis on it but I'm not putting them on my Ducatis

[machten]

one thing you should be aware of that you might not realize is the "choke" you have refered to on your SSI carb might be backwards to what you are used to. when the choke slide is in the up position it is "off" since this position then puts tension on the cable and the spring under load it seems counter intuitive. when the plunger is down it is "on" and blocking a passage way, increasing fuel.
so if you want to save some money you can just plug the choke tube and not use it at all, most people argue that it does nothing anyway, and was never meant to aid in cold starting.

Sort of. I think the way it works is that by putting tension on the cable actually leans the mixture by lifting the the plunger allowing a vaccum reduction across the main jet by sacrificing some vacuum by virtue of the air slot in the carb body. It is not starting facility, in fact, quite the opposite. It is intended to be used when you are giving it a bit of a hammering. If you're going run the SS1, I'd get it working if you want to go past 6000 rpm. To enjoy what these little gems can do, you'll want that.

I think that;s the theory anyway, but I'm happy to stand corrected. I do know that I wont get my 250 past 6500 without the air slide "on". After that, it's all the way up to as close to red line I'm prepared to take it (with the wind and down hill!)

Kev

[amartina75]

the Dellorto SSI manual on the tech page states that "A correct carburation at high speed must be obtained at completely opened air valve."
and reading the rest of the manual and other posts on this forum is a true test in "reading comprehension"
there seems to be debate on how exactly it works, if at all.
if the carb should be tuned with the slide fully open then that is the "off" position and I was mearly trying to make sure that Magman knew that.

[machten]

the Dellorto SSI manual on the tech page states that "A correct carburation at high speed must be obtained at completely opened air valve."
and reading the rest of the manual and other posts on this forum is a true test in "reading comprehension"
there seems to be debate on how exactly it works, if at all.
if the carb should be tuned with the slide fully open then that is the "off" position and I was mearly trying to make sure that Magman knew that.

My experience is that the air slide position doesnt make a damn of difference until you are predominately on the main jet, which aligns with "A correct carburation at high speed must be obtained at completely opened air valve." . That's consistent with with my experience to get past 6500 rpm.

if the carb should be tuned with the slide fully open then that is the "off" position and I was mearly trying to make sure that Magman knew that

The silde fully open is in the "on" position, the same position as a choke would be (tension on the cable). I don't have the document, but I'd assume that the tuning referred to is just for tuning a main jet or the running bike itself (by moving the lever and thereby changing the mixture) for high speed.

Kev

[Jordan]

As SSI is Dell'Orto's version of the Amal TT carburettor, the info here may help understanding of both:
https://www.dropbox.com/s/krtf1i83khqid ... Tuning.pdf

Jordan

[DanM]

You may want to check the gas cap venting. If it is plugged, it can cause the starting and then quitting problem you're experiencing.