Smokey idle.....Dellorto folly?!!!!!

[Major Softie]

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.

Since water injection is supposed to de-carbon combustion chambers, I wonder if water-contaminated fuel is actually good for your bike - at least in that way.

[Jean]

THAT sort of water injection cost me about 10 mpg, so I'd say: NO. The gains from de-carb are offset by the poor milage.
Carbon out...carbon in. You might say, the carbon was changed. Wouldn't want any OLD carbon in there.

[hools100RS]

Thanks for your replies. Jean, you were right in assuming that I wasn't getting any smoke prior to the DELs so we'll assume that the difference is in the carbs. Thanks Vanzen, I'll keep trying with adjustments of the idle mixture and idle speed to get a happy medium. I've checked float heights, they seem OK. It's a niggling 'problem' that I'd like to sort out but the bike idles nicely within its current setup and revs cleanly, with no hesitation or flat spots. 'Seat of the pants' tells me that there is definately more urge and the throttle response is really crisp. Don't know how the fuel consumption will be effected, but I'm not stressed. I'll drain the tank and start with fuel from another supplier to rule out possible water contamination, but the bike's running too cleanly to think it may be an issue. I do run a 'valve saver' (forgot to mention that!!) come upper cylinder lube (very small amount) and wondered if that might contribute to smoking as the fuel level approaches reserve? Surely it wouldn't be more concentrated in the bottom of the tank? I'd have assumed that it was fully dissolved. Emptying the tank might eliminate that as a cause as well. Thanks all! Hools.

[mattcfish]

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 ...

Well....... Actually the mixture screws on PHM 38's are fuel screws not air. In makes it lean and out makes it rich. The screws would be ahead of the butterfly if they were air screws. Some Dels are set up this way, not the R90S PHM's. Trust me, I know.Yes, set them at 1 1/2 turns out. Yes, set the idle speed screws at 1 turn out. A good way to test if your idle circut is functioning correctly is to screw one mixture screw in all the way while it's idleing. That the cylinder should stop firing if the slides are set at 1 turn. If it doesn't, check that your choke is closing off all the way. Float level must be precise. The most accurate way to set the floats is to remove the carbs, stand them on end so that the pivot side of the float is on the bottom. Measure the distance from the bottom of the float to the the carb body. Must be between 17.5 and 18.5 mm. If they are off even a little you will know.

[Armaguidon13]

you haven't made an oil change at the same time ? Could be an oil problem, too light oil for example.

[Rob Frankham]

Then I realized it was steam I was seeing...

On a point of order...

Steam is invisible... what you were seeing is water vapour...

Being a nit picking smartass is so much fun sometimes

Rob

[Deleted User 62]

Then I realized it was steam I was seeing...

On a point of order...

Steam is invisible... what you were seeing is water vapour...

Being a nit picking smartass is so much fun sometimes

Rob

Actually, your only partly right. Your definition is #1 in Websters Dictionary, but #3 states: "the mist formed when the gas or vapor from boiling water condenses in the air."

[hools100RS]

Hey !!!! Are you guys taking the piss or what?!!!!! Actually, draining the tank, winding in the mixture screws just under half a turn (and resetting the idle speed!!) has cleaned him up!!!! I'm thinking I had a residue of upper cylinder lube, lurking in the bottom of the tank.........dunno! Anyway the carbs are working well and there is definately a performance increase.....unbelievers just don't know, don't understand, don't care or have dead nerve endings in the seat of their pants!!!! Increased fuel consumption (slight....3-4 MPG, average riding) is a trade off I'm prepared to accept.
VROOM!!!!!. hools.