Playing with a Dellorto SSI

[DBDBrian]

Got a few miles under the wheels of the 200 SS , fitted with a Dellorto SSI 27 A, so now able to employ some higher working rev's . It ran quite well at light load up to around 5000 rpm, but appeared to be a tad on the rich side, once through this point, at larger throttle openings it cleaned up but still seemed to be rich. Removed the 108 (Listed) main jet and fitted a 104, seemed to make a slight improvement but still not right, dropped the needle one notch from the middle position, which again made a slight further improvement but still not totally happy off load.
The book spec list a No 8 slide, but I had fitted a 7 as this was all I had at hand.
Not wanting to alter the No 7 as that course of action being a one way trip. But unfortunately I was unable to locate a new No 8 ? So resorted to making one, quite a few hours later I had one in my hand. Installed it with the needle returned to the centre position (as spec) vast improvement but still a tad fluffy off load. Dropped the needle one notch, good result. Then did a full throttle run at just over 7000 rpm, plug check indicated maybe a bit on the weak side, refitted the 108 main jet and the plug looked about right after another test run.
Test rides were only about three miles, so need to get in a few miles of normal riding now to see how things go.
As Jordan mentioned in a previous post, the SS carb certainly looks the business, (and it was fitted as original equipment on the 200 SS), but yes it's basically a racing instrument, not too far removed from the Amal GP on my Goldie, which are just about acceptable for road use once sorted, but as opposed to the Amal GP, the SSI Dellorto does have the luxury of a slide prop.

PS.
Not having a 104 jet, I modified the standard jet by shortening , drilling and tapping a 5 x .75 thread, then fitting a later type Dellorto jet, which fortunately a mate has a good selection of.
These being readily available, and far less expensive when experimenting to determine the required size.
I'm also running a remote float chamber, which lends itself for easy fine tuning of the fuel level, it's set at the recommended datum point on the carb at the moment.

[Duccout]

Hi Brian,

Very interesting and you are right, the SSI carb does look the business! It takes me back many, many years to when I was riding velocettes, and GP and TT carbs were at the top for bragging rights. I lived in Walthamstow and one day in passing popped into Vic Camp's tiny shop, where I saw Italian exotica bedorned with giant Dell'Orto SSI carbs; man they looked like they were doing 100 mph standing still. Ducati always loved their big carbs - didn't the 450 racer have a 42mm instrument?

Colin

[DBDBrian]

Hi Colin
Not sure as to the size of the carb on the 450, yes it was certainly large, but as you say, what else would you expect, it being a Ducati.
I sometimes wonder if I suffer from some sort of malady, as I can't help myself when it comes to large carburetters with open bellmouths and big front drum brakes, perhaps I need help!

[Jordan]

The SSI main jets look suspiciously like Amal types.
Any chance they would fit?

[blethermaskite]

I had an ex Ducati ssi 29 on my Aermacchi 250 and if my memory serves me right I was using Amal main jets in it, I can't remember if I bodged the conversion myself or if I inherited it with the carb....whatever It worked fine and gave me an endless supply of main jets to play with at minimal cost.
Cheers,
George

[DBDBrian]

Just checked an Amal GP Jet, 1/4" X 26 TPI Most likely BSF or could be BSCy.

Dellorto SSI Jet 6 X .1 MM

It would be an option to make a brass adaptor with a male 6 x 1 thread and F/ male 5 x .75 to accommodate the later type Dellorto jet, if a spare SSI jet was not available.

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