LCGB Forums

Weird one that's doing my head in....

Let me paint you a picture...

RB225 / 34mm dellorto/ Nk road rally pipe, static AF Stator @18 deg.

Running in , done 300 miles.
Scoot going well, rode the 8 miles to the mot station on Friday, going great.. starts first kick....etc
Then......
In prep for a trip to a dyno session I filled my tank up with BP 95 petrol @ 4% Rock oil as normal...rode 0.25 miles home..
Next morning, raining hard, wet weather gear on, set off to the dyno workshop. Made it about 3/4 Mile before the scoot spluttered to an abrupt stop....like running out of fuel. Not that I've ever done that... tried to start it again, normal resistance / compression.
Stay with me, just setting the scene...

So at the side of road I check the fuel is reaching the carb.

It is.

So I check for a spark. Ouch, we have a spark.
So I strip the carb and check the float chamber, blow through the jets, watched by an old man and his dog who had a GP back in the sixties. The man not the dog.

Put it all back together, egged on by the old fella ,his mutt and his stories , I kick the scooter over.. .....

Success! It roars into life, I get on, say my goodbyes and set off down the road with a smile on my face. I'm great!!!
...for 100 yards before spluttering to a stop again.
I pushed the scooter home, in the pouring rain, sweating like a glassblower on a summers day.

After a cup of tea I set about having a better look .

I strip the carb again and blow through all the jets with compressed air.
The float chamber and needle are fine, no debris at all, clean as a whistle.
Put it all back together. Did it start? No.
Check the spark again. Is there still a spark ? Yes!
I change the spark plug for a new one. Still no joy.
I check the fuel flow. 1 pint in 40 seconds. So that's fine.
I take the plug out again and it's wet with fuel so it's getting through...

Aha - it must be electrical!
I check the stator resistance values. All spot on!
A visual inspection of the stator yielded nothing.
Just in case I take the Ducatti CDI unit, HT lead and plug cap from my other scoot and fit it.
Also checked the earth wires. Fine.

Kick it over.... Nada.

So then I started thinking about the fuel... I managed to get about a mile from the point I added the petrol.. That would be about a float chambers worth + what is in the pipe. Have I got some dodgy petroL?..mmmmmmmmm.. ? That must be it ! Why didn't I think about this in the first place??? Clutching at straws now. So I drained 12 litres, swilled out the tank with fresh stuff, added a fresh litre and rock oil...kicked it over.... Zilch.

So.. I'm suspecting a dodgy intermittent stator now, even though I have a spark.

What am I missing here guys ? Is it something obvious????


Oh and the house smells of petrol now and as well as having a broken scoot I'm in the dog house.

Once you had cleaned out the tank and put just 1 litre of fuel plus oil in,did you put the fuel tap on reserve.The original problem could be caused by a blockage in the tank cap breather.

Hi Paul. Flow rate was 1 pint in 40 seconds with the cap on.

I think the stators a good call, might be worth checking the reed petals as well...........

Hi mick. I thought about the reed petals. I don't know what to look for.. Would a defective set give these symptoms?

HxPaul wrote:Once you had cleaned out the tank and put just 1 litre of fuel plus oil in,did you put the fuel tap on reserve.The original problem could be caused by a blockage in the tank cap breather.

Filler cap breather was my first thought but on releasing the cap, which I believe the OP did several times, would release the vacuum and allow the fuel to flow again enabling starting and running for about one more mile until the vacuum re-created and the scooter stopped again. This scenario didn't happen so I think we can rule that out,

Rich'

Did you disconnect the Green ignition Wire ? could be if its got wet its shorting the ignition circuit causing the issue ? just a thought

Hi Toddy - yes did that too, sorry I should have added in my summary.

I appreciate everyone's comments / Ideas - keep them coming!

I'm going to check the reed petals tonight. If OK then I guess I will change the stator. I have a Casa variatonic kit that I was saving for a future project which I can put on.

Steve

I dismantled the Manifold to check the reeds - look what I found: -

One of the reed has broken. About half of it is missing.
Hopefully this is the cause of the problem

I'll order a replacement, and let this forum know if the issue is fixed!

Covboy wrote:One of the reed has broken. About half of it is missing.
Hopefully this is the cause of the problem

I'll order a replacement, and let this forum know if the issue is fixed!

Hopefully happy days

dayum
well thats sure to be the problem .....fingers etc crossed.

Well I changed all the petals for new carbon ones.

Started first kick. Hoping it was a one of incident and not a recurring feature every 300 miles

thats great news anyway. Wonder what caused it to fail ?