Octane's SSI Thread

[Bevel bob]

Hi octane, I'm glad to be of help, its not a very accurate system as it also allows the slide to rock if theres any wear, I've put a couple of solder blobs on the base of the slide to hold it up as a base setting.

[machten]

Let me also add my thanks to everyone contributing and asking about this and the "Atomiser" thread.

I'm about to embark on rebuilding and fitting my SSI 29D for my 68 250 and this and earlier posts is all helping me prepare. Keep the info coming!

Kev

[machten]

After getting a bit inspired by Lex's 250 Mk3 running with it's SSI in Europe, I finally got around to taking off the VHB 29, making up some new cables and fitting the SSI yesterday. My thanks to the contributors of this thread and also this one:

http://www.motoscrubs.com/forum/viewtopic.php?f=3&t=952

They were of great assistance to me.

I set mine up with the stock settings for the '68 MK3D SSI 29D according to what I found in Mick Walker's "Ducati Singles" book:

Needle - M14
Main - 115
Pilot - 45
Slide - 60
Jet - 260

I haven't had it up above 6000 yet, but it seems to be idling fine just below 2000 and pulling fine in the surburban blocks. As it bonus, it even seems to start easily with a little tickle. Hopefully a break in the clouds will permit a little squirt down the freeway to test it some more and check out the plug.

Thanks all once again.

Kev

[machten]

Clouds broke in the afternoon and had the chance to stretch the M3D's legs a bit. It pulled well up to 7000 rpm in top gear and I left something in the bank. It seemed more responsive than the VHB carb, but that might just be a red herring impression due to newer, more slippery throttle cables. Anyway, all good so far - now ready for this year's Albany Hill Climb in three weeks time.

Kev

[Octane]

Good to hear M10!!

Mine's running reasonably well lately too. Cold starting is no issue at all with a little tickle, and correcting the timing a while back.

It does seem a liiiitle hesitant at low revs though when the engine's warm. Sometimes it'll idle well at 2500rpm after a couple of minutes of running, but on a warmer day after the bikes been running a good half hour or so, it seems to labour a bit at idle, and it's not quite as responsive in the 3-4000rpm range.
4500-7500rpm it's a ball tearer though! Always puts a smile on my face!
Maybe I need to drop the needle 1 more position?

[graeme]

Think about throttle position rather than revs and work out if its in idle, slide, needle or main jet mode as the throttle is opened.
That's the easiest way to me to get a base setting on a new carb.
A marked piece of tape on the throttle makes it easier.
Graeme

[machten]

It does seem a liiiitle hesitant at low revs though when the engine's warm. Sometimes it'll idle well at 2500rpm after a couple of minutes of running, but on a warmer day after the bikes been running a good half hour or so, it seems to labour a bit at idle

I have to say, I didn't push on with the SSI install because the VHB seemed pretty good and I'd read many reports about idling issues with the SSI. With another few hundred km of city riding, I can say that I am delighted with the SSI's manners. As some context, this SSI is in very good shape, with pretty much no slide thoat wear, new slide, jets, atomiser and needle. I don't know how many RPM it idles on without incident, but I'd guess 200 RPM below the 2000 RPM stopper on the white face veglia tacho. I am using the original stock silentium exhaust setup - not a megaphone and an open bellmouth.

and it's not quite as responsive in the 3-4000rpm range.

Other going through first gear and a part of second, I don't run my MK3D at those revs. 3-4000 is where it seems to really dislike things - not due to carburation, but rattling of top end on the desmo cam and springs. Is that a harmonic thing? At about 4300, top end silence descends and the cam starts to cut in. It's all smooth upwards from there. It reminds me very much of my old Kawasaki Mach III 500 hitting the power band, but much (!) more subtle.

One thing I don't understand (despite having read on this forum and Brit Bike forums) about the "air slide", is that mine seems to have absolutely zero effect whilst running. Maybe it's been plugged up internally, I don't know. Given the bike is running fine now, it isn't plugged up externally and is cabled as it should be, what should I expect when I use the "choke" lever. (And I know it's not a choke!!!)

Kev

[Octane]

Think about throttle position rather than revs and work out if its in idle, slide, needle or main jet mode as the throttle is opened.
That's the easiest way to me to get a base setting on a new carb.
A marked piece of tape on the throttle makes it easier.
Graeme

Thanks Graeme, I should have known this
Seems to be happening around 0 - 1/3 throttle. Basically at the throttle level you need to maintain a steady speed on flat ground.
Perhaps I need to go for a throttle slide with a slightly lower cutaway. It's not a major issue, and it's perfectly rideable, but I'm a bit of a worry wort and I tend to think the worst when the bike starts hesitating A perfect tune = peace of mind.

As some context, this SSI is in very good shape, with pretty much no slide thoat wear, new slide, jets, atomiser and needle. I don't know how many RPM it idles on without incident, but I'd guess 200 RPM below the 2000 RPM stopper on the white face veglia tacho. I am using the original stock silentium exhaust setup - not a megaphone and an open bellmouth.

At about 4300, top end silence descends and the cam starts to cut in. It's all smooth upwards from there. It reminds me very much of my old Kawasaki Mach III 500 hitting the power band, but much (!) more subtle.

One thing I don't understand (despite having read on this forum and Brit Bike forums) about the "air slide", is that mine seems to have absolutely zero effect whilst running. Maybe it's been plugged up internally, I don't know. Given the bike is running fine now, it isn't plugged up externally and is cabled as it should be, what should I expect when I use the "choke" lever. (And I know it's not a choke!!!)

Kev

Yeah my slide has some very minor wear on the sides. Nothing extreme. I'm running a megaphone on it at the moment. Also same here, at around 4500 the bike just comes alive and pull hard all the way to the red.

Also, my air slide is set up as per factory, and it has no negligible effect on my bike either.

[machten]

I discovered an interesting (to me, anyway) phenomenom today. As you can see from the earlier posts, I'm an SSI newby. I'd noticed in the last week when stopped at traffic lights that sometimes the 250 M3D would idle at different revs to others. I'd placed it on the stand at home to listen to it, even for up to 5 minutes and it was always consistently idling at the same revs - a nice even tickover. I was thinking that I might have a sticking float or something.

While stopped at a red light today coming home from work, it occurred to me to test something, and sure enough, it was right and reproducable every time. If I lean the 250 to left, revs increase, if I lean it to the right, revs drop off. The difference in revs I was experiencing was dependant on which leg I had on the ground - it seems to be that sensitive. This might be no news to the experienced, and I don't know if it is "normal", but it was a bit of revelation to me.

Kev

[Octane]

Yeah I've heard that the float angle can have a big effect, so this makes sense to me, although I hadn't personally noticed it before. Next time I ride mine I'll try the same experiment and report back.