Please need help, very disappointed.

[JVROOM]

Diagnosis, reply from,Stoltzee

Yes, you're right, not very bright of me to say not running well, or inconsistent, whatever without any information the the basic issue, is I can't quite seem to get the idle set right. Clone Dellorto carb. On the right side of the carburetor, there are two adjustments, one looks like standard idle adjustment needle with the spring. The other looks like a brass jet, with a O-ring seal. Screwing it out of the carburetor it has a brass needle and on it and it's about a half-inch long. Adjusting those both affect the idle. It's possible I damaged the O-ring around the brass needle and it's sucking air I don't know. When I get the idle adjusted pretty good and run a bit, the next time I come to a stop she dies? So I just end up with the idle running kind of high, and I'm wondering if this is related to break-in of the motor, vacuum leak at the jet or something else. Still trying to make it run, while waiting for a carb. from Rocksolid, which looks like it may be a while. And I think I have excessive vibration. I'm learning this stuff slowly, are any shops around here, that so these motors etc., and have only seen one other one on the road. So this forum is my only source of information, and I appreciate all the help that I have had, sincerely, John

 

[Fabian]

It will be worth the wait. The reed valve intake is like a shining billet jewel. I would expect the reed valve to diaphragm carburettor adapter block to be no less perfectly designed and machined.

For what seems like an eternity, we've desperately been waiting for an after market manufacturer to bring out a Walbro style 'twin needle" carburettor, with it's ease of tuning and dependable carburation, but even so, this system is just a stop gap measure until Rock Solid Engines releases their electronic fuel injection kit, but from what i understand, it could be over a year away.

Having said that, a diaphragm carburettor is the closest thing to fuel injection that's currently available at a reasonable price, however, i'm prepared to pay Rock Solid Engines any amount of money to get my hands on an electronic fuel injection & ignition kit, with a laptop interface.

 

[Fabian]

I tried the Dellorto clone (jetted correctly) and found it to give no real improvement over a properly jetted NT carburettor. Not only that, the Dellorto clone never had a good seal between float bowl and carburettor body; which caused it to leak fuel.
As it didn't give any real power improvement over the standard carburettor, i never bothered with it after switching back to the NT. I gave the Dellorto clone to my next door neighbour to mess around with. From what i understand, it's still sitting in a dusty drawer somewhere in his shed.

 

[JVROOM]

Can't wait for the Walbro Carb.

Excited about a new Walbro carb. Does it have a cable for the choke or is that just lever operated at the carburetor? And wondering about the fit? I found that sweet Reed valve kit a piece of cake to install. I only had to slightly modify one top airfin on the engine barrel. The clone Dellorto fit well without any interference with clutch cable parts etc. Wondering how the new Walbro carbs will fit? In the meantime, maybe I'll just put the original NT carburetor back on. It has never even had fuel through it, at 850 feet above sea level, thinking about a 78 jet? This forum is the only place I have for gathering the golden nuggets of information I receive, and I am very thankful, John

 

[Fabian]

The only real problem area of the NT carburettor and any of the compression fit carburettors, like a genuine Dellorto or Dellorto clone, is that they are susceptible to air leaks where the compression clamp fits onto the intake tube or the tubular clamping point on the reed valve intake.
It's the slots which allow the curved plates to compress against the intake tube to leak a lot of air, causing huge headaches if not properly sealed with an o-ring method.

This problem can be easily fixed on the Nt carburettor by placing two o-rings inside the rear of the carburettor throat (where the clamp is located) and resting up against the step inside the throat.
You will need to gently press the carburettor against the intake tube or Rock Solid Engines reed valve intake to make a good seal between the carburettor and the intake tube.

 

[JVROOM]

Thank you for that information, makes a lot of sense, I'll get some O-rings do that. Sounds like that is why am having trouble with setting the idle speed, vacuum leak. Love these little Golden Nuggets of information, John .

 

[Fabian]

The diameter of the o-ring material you need to use is about 1.5mm thick, which is about the same height as the step inside the NT carburettor throat.

 

[Fabian]

The only issue with the o-ring method is that (ideally) you'll need 3 hands to fit the carburettor: one hand to press the carburettor against the intake tube or reed valve intake; one hand to tighten the screw and one hand to stop the nut turning as the screw is tightened.

The moment you release pressure from the carburettor, it will want to push away from the o-rings, potentially leaving an air gap.
That said, you can cheat by gently tightening the clamp so there is some friction on the intake tube, allowing the carburettor to stay in place as you release hand pressure.