My 83 XC500 get a Lectron carb (pix)

Yep Surprize.
Couple of weeks back.

I cant hang on to the bars, the wind would blow off the back!! last time I got to wind the 400 out in top, as it came on the pipe in 6th I was flapping off the back like a flag!

I had to ease off before it was a pilotless drone!! (hate being old sometimes )

I also have a Maico 490. I think the reason they get to the 1st corner with such regularity is because they have such a wide tractable power band. They were the 4 stroke of today. However in a Top Speed contest I don't think they are going to catch the big KTM with its Bigger Bore shorter Stroke 14:1 Compression and small Expansion Chamber diameter.

Today I just received my No 57 issue of VMX magazine. It has what I would consider an excellent article on the Lectron Carb, both the History of the Company and the Carb, the new developments in both ownership and tech. Then they go on to do an installation and a brief test. The one thing the article is missing is a before and after Dyno Test with an Air-Fuel Meter.

wheres the 500 vid?

+1

Hi- I race vintage mx and was wondering if there available for a 1977 YZ400D that uses a 38mm Mikuni and a 1979 Can-am rotary valve 250 MX-5 that used a 32 mmm Delorto? Also what would the costs be per bike? Thanks Jon

If one where to get a Lectron Carb from the 70's or 80's how interchangeable would parts be with a current one? Are Float Bowls etc interchangeable ? If the parts do not interchange, where is the break point where they do and don't?

Lectron fitted.
Slightly shorter than stock, makes fitting easier.
very easy to start
Very crisp running so far.

Finally, I got to run the bike properly.

Test 1 was a short MX track, http://www.syringamx.co.za/. Very powerful and the bike seemed a little rough on the bottom end, which led me to go 1/4 turn leaner after the trace.

Test 2 was around the block on tar at home. Felt very crisp off the bottom. All looking good and promising.

Test 3 was on a long MX track. Now it seems worse. Get to 3rd, and pin it up the straight and it blubbers at the top, doesn't clear.
I then found a slight uphill jetting stretch, and all is fine till 3rd, then the engine just dies. As if you are out of fuel. You can back-off the throttle, and the engine comes back and runs again.


Next step is to go back to where I was, then mount a GoPro to see what the float level is doing while flat out in 3rd.

It really feels like its running out of fuel - just not sure how ?
Now if I had access to rolling road dyno........

Be careful in 6th gear. My buddy's kx250 was topped out when my son blew by the kx80 on my 86-400wrx. We clocked the kx250 at 85mph wide open. The way the 400 passed the kx250 the 400 was well over 100mph. These wr husqvarna's are very fast. Being an exdrag racer my '98 husqvarna 250wr easily ran 12 seconds in the quarter mile maybe even better.

Update:
Stripped and cleaned the float bowl, the rod hole and all the overflow lines.
All are clean.
On bolting up the bowl, it looks like it might be warped slightly, on the long edges (front and back of the carb) - possibly an optical illusion as it certainly doesn't leak fuel. There is an O-ring seated into the bowl and also a thicker rubber gasket that fits between the carb body and the bowl.

The rod is a 5-XL and the carb has the serial number 334 B4 dremelled onto it.

Latest observations:
I have narrowed down the issue - but not how to solve it..

At about 50% throttle, the Powerjet line starts to flow fuel.
Just after that, all the fuel in the bowl turns into froth. It becomes a mass of air bubbles. Looks like foam.
It seems that this amount of air in the fuel is causing the starvation and killing the motor.
It happens at standstill in the pits, and also on the jetting strip, both at about 55% throttle.

Could be pure motor vibration - apart from a dynamic balance - not sure how I will solve that. All motor mounts are tight. New stainless steel front engine mount plates to keep everything secure.

The intake manifold is the "works" style from Husqvarna-parts.
http://www.husqvarna-parts.com/catalog/item/3736880/4885100.htm

Comments and suggestions welcome.

@Moto:
Have you ever seen the carb bowl contents turn to bubbles though ?
I need to find the link between the vibration and cavitation in the bowl...