Beta Alp 4.0

A collection of information as it arises. There's not a lot out there!

Thursday, May 01, 2008

Odd running

A correspondent with an Alp 4.0 is travelling through Spain and has complained of rough running of the engine. He feels it is something to do with ignition but can't be sure. The engine runs but at a certain rev range it's noisey. A mechanic he saw suggested that the CDI needed reprogramming. This seems a bit unlikely as it's doubtful if the ignition on this sort of machine is reprogrammable, and why should it change?

My suggestions of things to look for were:
  1. The microswitch on the carb butterfly valve - what happens if this is jammed?
  2. Open circuit plug cap - I've had this problem on other bikes and it is a pain
  3. Over-oiled airfilter causing richness
  4. Excess oil in the sump causing fouling of the air box
  5. Open drains in the airbox causing loss of vacuum
  6. Loose connectors or water throughout the circuit
  7. Foreign object in the float bowl
Other possibilities were:
  1. Improperly seated kick start lever partially engaging the ratchet
  2. Timing chain or tensioner problem
  3. Lack of tappet clearance
  4. Something, anything (sump guard, bit of fairing, luggage etc etc) vibrating
  5. Loose engine bolts
I hope I'll hear what the problem is so I can be aware of it...


At 7:32 pm, Blogger Jean-Pierre said...

On my Beta Alp 4.0 I have problem of bad running of the engine sometime to time during acceleration.
When I disconnect the microswitch on the carb butterfly valve, I don't have anymore this problem.
Do you know what is the use of this microswitch, and what happens when it is disconnected?

At 4:16 pm, Blogger Adrian said...

I believe that the switch adjusts the ignition module to reduce power in third gear. This is to reduce noise. Mine had the switch disconnected when I bought it and the socket taped into the loom. Perhaps it had never been connected?

My traveling correspondent did discover the source of the noise and rough running. His machine has an air inlet valve on the exhaust header and the pipe had rusted, upsetting the pressure on the header and most importantly, making a lot of misleading noise.


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