Scooterotica

What’s the cause and what’s the cure?

Normally timing too advanced or running weak (overheating)

when mine started it turned out to be the cdi packing up . only found out after a lot of playing about in rain and snow.
thought it was timing as it normally is but i was wrong as normal

If you can get hold of some of the two stroke tuning books still available, some dating back to the early 70's. This topic is covered very well, explaining squish band area relative to combustion chamber, for example 50/50 or 60/40... and how it effects power.... to design of cylinderhead such as... Off set squish heads, center squish heads, air cooled or water cooled and all using varying combustion chamber designs... Its a science in itself, but fortunately the basic principles are very easy to follow and the maths used as for compression ratio is very basic... look for "2 stroke" tuning books by authors such as.. A.G. Bell, Gordon Jennings, Roy Bacon...etc... Otherwise Google these names and you should find some info to better understand the reasons for pinking...

Undrstanding the basic principles will enable most to prevent the causes....

Fuel starvation can also be a cause, or in my recent bad experience, a 4mm hole drilled in the back of the crankcase* causing a very weak mixture.

Sometimes it can be weak mixture casued by an undersized fuel inlet valve within the carb, or even a low-flow petrol tap.

Martin







* I drilled the hole and I don't want to talk about it......

Upjetted my carb...it dont pink any more.

mate...after all the grief I had I upjetted to 125 & ragged my lammie for 70 miles with no problems at all. What works for some may not be for others...but I was getting pinking rapidly followed by a heat seize, so upjetting has worked for me.

Now it could just be paranoia as I get all sorts of rattles and noises from my scoot, but I did have trouble getting my squish down, can’t remember that I settled on but I know it was more than 1.2mm (advised at the time by AF that it was ok but as they seem to have a dubious reputation its probably worth re-checking)

Standard TS1 and Head from AF..Is it safe to run it without the head gasket? Or is there a better way to reduce the squish?

EGT sensor not showing any abnormal temperature rise and all else seems well.

Probably just my spanners rattling in the tool box or Mikuni 30mm syndrome

Cheers

All those tuning books would be useful to most but unfortunately I have the attention span of a five year old when it comes to reading anything technical.........



(awaits sarky reply from burridge01 )

I always try to build mine without a head gasket, Its somthing else that adds to what can go wrong....

1.2mm is what I try to set my squish to, but on a touring scooter sometimes having to increase the volume in the combustion chamber to keep the compression ratio below 9.5-1... but usually nearer to 9-1 on a standard type skimmed & reprofiled head

Knowledge wrote:Fuel starvation can also be a cause, or in my recent bad experience, a 4mm hole drilled in the back of the crankcase* causing a very weak mixture.

Sometimes it can be weak mixture casued by an undersized fuel inlet valve within the carb, or even a low-flow petrol tap.









* I drilled the hole and I don't want to talk about it......

Martin

:baddevil:

Martin please lets talk

What you upto m8