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G'day everybody! After a bare crankcase rebuild of my '81 100RS and running him in with standard carbs, I decided to convert to Dellortos. A number of reasons really..........(1)I love the Dellorto carbs and have had more bikes with them on than not. (Laverdas, Guzzis, R90S) They are a pretty straight forward device and work well. (2) I wanted to see if I was up to the task of re building an old set of PHM38's and getting them to work on my 100RS. The tasks was pretty involved, what with removal of the original intake stubs ( that didn't want to come out!!) and replacement with the longer 90S stubs. (that didn't want to go in!!!) Freezing the replacement stubs saw them screwing into the 100RS heads with no dramas and tightening them(carefully) with some stilsons. As I couldn't figure out how to run a twin cable twist grip setup (like the 90S) I ran a standard single cable to splitter to the dellorto cables. This results in a really long cable run but it all tucks in behind the RS fairing very neatly.
(3) I wanted to see for myself if the Dellortos have any performance edge over the Bings. I've read about every thread posted about this conversion prior to setting out..........some folks reckon yes.....some reckon no.
Well, the conversion is complete and the bike is running well. After a weekend of gentle cruizing and a few hard runs, plug chops tell me that the motor doesn't seem to mind the change. There is one issue that I am uncomfortable with though and that is that I'm getting an inordinate amount of white/greyish smoke at idle. The smoke doesn't smell oilly and prior to the carb change the motor was smokeless; new guides, valves, good rings and bores, etc. Would the idle circuit be contributing here and would a change of jetting be required or just adjustment with the Idle mixture screw? I started with the 90S settings of 1-1.5 turns from seated and I've experimented with more turns out (leaning the mixture.yes?) but getting a balance between idle mixture and idle speed (I'm aiming at about 1100 rpm) and no smoke is tricky!!
I think I'll perservere.........The throttle response is really good and I've set the accelerator jets to be pumping less than 'a full squirt'....hey it really pulls!!!.....
Any comments on the smoke issue? has anyone any similar experiences?? Thanks, Hools.

White smoke is coolant leaking into the cylinder.









Wait....

Major Softie wrote:White smoke is coolant leaking into the cylinder.

Is that AIR leaking into the cylinder Major?

edit quotes-dwerbil

hools100RS wrote:

Major Softie wrote:White smoke is coolant leaking into the cylinder.
Is that AIR leaking into the cylinder Major?

The Major was making a funny. I know because I gave out a slight titter after I read it.



Ken

Ken in Oklahoma wrote:

hools100RS wrote:

Major Softie wrote:White smoke is coolant leaking into the cylinder.
Is that AIR leaking into the cylinder Major?

The Major was making a funny. I know because I gave out a slight titter after I read it.



Ken

I thought he was serious and checked all the radiator hose connections on my R90S 'cos I get white smoke too...

Windshield-cleaning fluid also makes white smoke.
Check your power brake booster, too.

seriously (! why spoil a good thing?)
White smoke usually means oil burning from somewhere. (crankcase recirc??)
1100 rpm for idle sounds a little bit high too, although that wasn't the original issue. At 1100, you are not only "on" the idle circuit, I think, but have another jet in use.

Not a lot of experience with Dels, so for what it's worth –

The "mixture" screw is, in fact, an air screw –
so you would be correct in that "turning it out" leans the mix.
Position of the throttle slide will also affect idle mixture.
Air-screw at 1-1/2 turns out is the usual place to begin tuning,
Idle-speed at 1 turn from just touching slide, i.e. the slide is almost closed.

More than a turn in either direction from the preliminary tuning spec
generically suggests that something in the idle system is not "correct".

1,100 - 1.200 RPM is typical for tuning / idle.

Dels seem to be pretty sensitive about float height –
Incorrect float height can make idle tuning a frustrating if not impossible task.

Exhaust smoke is a typical sign of a rich condition –
The result of incorrect float level, mix & speed adjustments, or too large an idle jet.

Goes without saying –
Successful tuning will depend upon clean and properly functioning carb bodies, passages, and jets ...

DanielMc wrote:
I thought he was serious and checked all the radiator hose connections on my R90S 'cos I get white smoke too...

So, now I can't figure out if that would take forever, or no time at all...

Jean wrote: White smoke usually means oil burning from somewhere. (crankcase recirc??)

Being more serious (just a little), white smoke genuinely is caused by coolant. The colors being: white = coolant(steam); black = fuel; blue = oil. So, usually when someone says "white" smoke with an aircooled engine, we would assume it's really what we would call the "blue" smoke of oil burning. The problem is, it sounds like hools is saying that this smoking was not happening during the break-in with the original carbs, and only began when the Dells were put on. While someone could mistake blue smoke for white, it's hard to imagine mistaking black smoke for white, so it is very hard to imagine exactly what is going on here.

Is it possible that another change was made at the same time as the carbs that you have not mentioned?

Actually, I've seen white "smoke" coming out of an Airhead... after a friend put water contaminated gas in his R75/5. It ran like crap, and what I thought was smoke rapidly dissipated. Then I realized it was steam I was seeing...

That's how I read it...until the Dels were installed, ther was no sign of white/blue smoke. If the dels were running rich, the plugs ought to tell it, and if really rich, the "smoke" would be black upon acceleration.
Yes, Tim, I've see that same thing...got some water-contaminated gas on the way to Huntsville about 3 years ago...It DOES "smoke" white, and the engine doesn''t run very well, either.