Dellorto flaw

[Deleted member 12676]

you're absolutely right but the Dellorto doesn't have a traditional slide. It is just a flat wall in front of the jet column. I thought that raising the intake side of a traditional slide leans the mixture though. I have used that trick for fine tuning the idle circuit but I don't remember the details or which motorcycle I did it to.

 

[Fabian]

All the more reason to make the switch to a diaphragm carburettor.

I haven't looked back after fitting mine !!!

 

[Ludwig II]

I remember those carbs, they were used on a lot of Italian moped engines in the 70s and 80s. They're 2 position devices, idling and flat out.

 

[Fabian]

You must be thinking of a different carburettor.

Do a Google search for "Walbro Style Carburettor for Rock Solid Engines Reed Valve Intake"

 

[roughrider]

The two sections of metal that should be mating perfectly to disallow air leaks are thick enough to not change with heat. ... After correcting the air leak the Dellorto should be fine for most people though. I am aiming at absolute maximum performance from mine though.

Thanks for that. I'm gonna run the stock NT carb for a while. Then I'll swap the Dellorto clone and mess with the tuning. If I get an improvement, it's all good. I'm not looking for max power, just smooth, predictable power curve.

 

[roughrider]

All the more reason to make the switch to a diaphragm carburettor.

I do not doubt you my friend, but those carbs cost as much as a whole new engine! Yow! if you know of a deal, well, do tell!

 

[Fabian]

You get what you pay for, and in this case it's billet components and CNC work from start to finish, and the components work as designed, i.e. they work to perfection !!!

 

[Fabian]

Been there and done that and after testing the genuine Dellorto, the clone Delorto and the standard NT carburettor, i went back to the standard NT carburettor, before installing a diaphragm carburettor and everything became rainbows and sunny fields after that !!!

The laws of physics determine how much air you can move through a 14mm hole and the NT works just as good as any of the other carburettors,once it is set up and jetted properly; in fact the NT works just as good as a diaphragm carburettor with the same size 14mm venturi, with the exception that the diaphragm carburettor is easily adjusted for air/fuel ratio with a simple twist of a screw, not to mention that it does not leak "at all", be it air or fuel.
Once the mixtures have been set, they stay set, unless atmospheric conditions change, and even so, it's a 2 second adjustment to bring the air/fuel ratio back in line with changed atmospheric conditions.

Next to the SBP shift kit and the Jaguar CDI and the Rock Solid Engines reed valve intake, the Rock Solid Engines diaphragm carburettor kit is the best thing since sliced bread.

 

[lazylightning@mail.r]

Trying to perfect my race engine I found it almost impossible to get the jetting right. It seemed like there was a small air leak. I pressure tested the crankcase and there were no seal or base gasket leaks. My intake and reed valve were tested to be leak free. I messed with how the Dellorto carb mounts on the reed valve and finally got that perfect. But still the problem persisted. Then I took an investigative look at the Dellorto carb and found an air leak path designed into it! Taking the carb off and putting the slide in place and shining a light into the carb I could see light between the front of the slide and the carb. Air comes in over the slide from the air filter (and also from where the throttle cable connects to the top of the carb), goes past the front of the slide, and then gets into the air/fuel passageway through that small space between the slide and the carb. I can't believe they designed it that way. The design should be that the slide slightly scrapes the carb to seal and prevent any major leak. So now I have a Mikuni 18mm carb on order and until then I will put JBWeld on the slide and sandpaper it down till it just barely touches the carb. That should allow me to finish testing on a new pipe design.
I will probably have to let the machine shop lathe a new aluminum piece to replace the manifold piece of the Rock Solid reed valve to match the carb. Once I get the carb I can tell you all the inner diameter of its clamp so you'll know what size to tell Rock Solid to make the manifold on the reed valve you're ordering.

BUMMER! %-D I got the Dellorto =-(((

 

[Deleted member 12676]

Let me know how bad it is. Can you see much light coming thru that slit?