Guys,
When an electrical problem accur it's for me a trial and error to find the cause. In the past when installing a radio in my car often the fuses were blown
Nowadays internet helps me a lot.
Before i go to the experts, i hope you guys can help me to find the cause and also advice (to learn).

For a couple of years i had no (electrical) problems, but last year two trackdays ended in a DNS with my track TT1.
See: https://youtu.be/okg1_zeFUfg (don't mention the rev. counter, i know ).
From cold, the bike starts good and runs great. But after the warmup lap (appr. 5 km) suddenly the motor runs very bad and bangs when revving. it looks like it's the back cilinder. Then, if you wait for 2 min., everything looks normal again with starting and revving, but only for a short moment.
I don't know why and what the problem is. Is it an alternator - r/r - ignition issue?

Some facts:
750 Sport engine
Ignitech ignition (TCIP4 + coils + pickups)
Ducati race alternator 1 phase
Shindengen sh579b-11 rectifier (3 phase)

Some tests:
Battery voltage when idle and when revving: constant 14,3V
Resistance r/r and alternator: 0.1-0.2 Ohm
Tested the regulator with the diode setting. One yellow wire connected to the stator and one not connected showed a 630-630, one connected to the stator 595, a little ∆. A problem?
I also tested an 1 phase original Ducati (18W) alternator, but less AC than the race alternator.
Ground looks ok.

Main question is what the problem can be. Some say it's the rectifier, when the engine gets warm, to much current and then fails with consequenses for the ignition. I'm not an expert, but i don't get that. How is that possible?

To learn:
- is it ok to connect a 1 phase alternator to a 3 phase r/r?
- what's the best setup for a trackbike? A 3-phase alternator and 3 phase r/r? Maybe a total loss system?
- any experience with the Shindengen mosfet or SH847 rectifier ? (should be much better (performance and less heat) than the "old" rectifiers),
- if testing total loss, should i dissassemble the alternator or is it ok to be mounted, but not connected?

Thanks for your help and advice!

William

Hello! Are you sure it's the current ?, It would look like a petrol tap that doesn't have enough flow.
or a problem with the flow inside the float chamber.
It was just to make sure it's not another problem

I also wonder what the battery reads after the bike has gone around the track a few times and then stopped running. Did it drop something way below your initial reading? Say, down to 11V after starting ar 13V? If so then that might be evidence of a charging problem. I did have that problem with the TT1/F1 this past year, but solved that by going to the ST2 small alternator after I got back home. It was not corrected by just sitting for a few minutes at the track. Posted some info on that in one of the technical sections a short while back.

The three-yellow and two-yellow shindig regulators seem to work with just about anything, even the old alternators. Huit used the 3-wire with a 2-alternator and cut off the third yellow. I have left them dangling. I look at them as bullet-proof. And if it was working before.....

I did not understand some of your measurements (just different from what I look for now), and you did not say what kind of battery you use. And out of curiosity, what carbs are you using?

The quick recovery does sound like fuel starvation in a way. Had that on my first stock F1 one time way out in the country. And a couple of times at a track, for very small reasons like bubbles still in a newly-installed fuel line, or trying to run with one of those 900ss vents in the line. I guess a float could get stuck in the up position. Did you open the fuel cap to see if it fired up and ran right after it stopped? Did you bang on the carbs?

Finally, are you sprint racing, or endurance, or doing track days? I know a quite a few who wanted to go just a little faster and went to total loss systems; no alternators and no starters. Then they found they could not complete a track day that way. Just another pain really. Try to solve your problem first, and then decide if something entirely different is “better”. You will not have that nagging question sticking in your mind —- what was that?

If it is electrical you have asked one of the most difficult of questions to solve from a distance. I know having done that. I wish you good luck.


MikeV

How is the tank vented?

Guys,
Thanks. Interesting!
The carbs are 39VHSB racing dell'orto’s with 3,5 gram floaters. They looked fine and slide well.
The tank is vented on top with a hose. Checked it.
Battery is a Yuasa ytx14bs (new).

Mike, yes, it's detonating at the rear carb.
First i'll concentrate on checking the carb, then the electrics.

William

Hello William


........... are the valves closing properly ?

Ok, i checked the carbs and floaters and contacted MikeV.

There is something strange with the floaterarms. They are more bent than new ones. See pics. The front is the new one.
Also the floaters are 3,5 gr. Too light?
That means the needle valve will close earlier....lack of petrol?

So, got some parts from Germany, 4,5 gr floaters, new arms and gaskets, cleaned the carbs and fitted the new parts.

Hopefully that's the problem...

William

When you start the bike, you have to make sure that the problem arises, get a small bottle of petrol with a very small hole, and manually grease the carburetion, you will immediately realize if the problem is petrol.
empty the trays and see if the working cylinder has the usual quantity in cc of the one which is not working

I checked in with William, and news about the bike started out good, but ended bad for William. The bike ran fine. But William high-sided, broke a LOT of bones, and spent some serious time in the hospital. His recovery will take a while. The Harris TT will probably be better sooner than him.

To a good and speedy recovery, William.

We all wish the same for you William! Lou