Scooterotica

What percentage should i be looking for when putting my vespa on the dyno?? Im only asking this question as the person dynoing my scooter on friday hasnt done many scooters

Keep it rich for an air cooled motor.I think optimum is 13. something to 1 but better to be around the 11 to 1 ratio (air to fuel)That's what my cast 225 Lamby was set at and has been fine. Try a PM to Diablo ,he may tell you better.

If hes used to dynoing 4 stroke liquid cooled bikes I would guess he's used to setting them with an AFR of 14 or thereabouts.
Can't speak for others but here we try and set as much of the graph at 12.
Its nice when the whole graphs tracks nicely along 12 mark but this isn't always possible and lots of things seem to effect the fueling graph. Try and achieve as much of the graph at 12 and make sure he does part throttle openings as well.
Remember that the engine isn't under any load so back up any dyno work with road testing.

Thanks !

Nice one Al.. you are the first person I know of... who posts with an inertia dyno, who understands it ,and says so .... Listen up people.


You cant set an motor up properly by afr on an inertia dyno.You cant replicate runs or load the motor.. You need a very good operator who understands heat to look at whats what and adjust accordingly. Alan knows the score.

tony wrote:Nice one Al.. you are the first person I know of... who posts with an inertia dyno, who understands it ,and says so .... Listen up people.

Goodness me Antony, if i was a shy sensitive type i might take that personally, fortunately i'm neither shy nor sensitive.....lol.

ssteam177.......this thread will help you also: http://scooterotica.org/forum/viewtopic ... 86&start=0

Quote from link:

" At mid range to top end 12.7:1 is a theoretical minimum safe benchmark for two strokes, but we richen some right upto 11:1....it all depends what the customer wants, safety/performance etc, condition of machine, and what is the spec....24 degrees ign/16 degrees ign, alloy ported race tune, cast iron stage 4 touring tune, Clubman/JL4, Mikuni 35mm/Delly 24mm, squish/comp ratio, is it a cut down with 11 stone solo rider, or is it a full bodied tourer that goes everywhere two's up with luggage etc, etc.

Plus at tickover and low revs (1000rpm-3000rpm) the scooter needs to be leaner than 12.7 to allow crisp tickover and take off, but once revs start to climb, A/F needs to take a nice curve towards the richer safe spots, but anything leaner than 12.7:1 at the mid-max revs section starts to worry me and i look for adjustments according to the variables outlined above. "

Oops sorry Dan
Can I add to my orginal post "and Dan" !
All good stuff . Wonder when people will start using eddy current brakes in the scooter world? Won't be long?

Our portable dyno uses an eddy current brake. We are looking to see whether it can be mounted to our static dyno as it uses the same software.
Unfortunately when we were using it we didn't have an AFR meter so can't compare data but hopefully sometime next year it will be possible.
One of the downsides at least with ours is that it was very unkind to tyres as one poor chap found out when we ran it at the first surrey scooter services open day. His Michelin S1 had loads of mini rubber volcanos erupting all over the place.
One of the big benifits of loaded dynos over inertia dynos is they will show up issues with timing,compression or insufficient cooling-its very rare I'll hear a bike pinking on our inertia dyno. Often this only shows up with a road test after jetting. A lot of scoots come in over rich which is masking problems that have probably always been there. My little test track usually picks these up though

Nice one mister Diablo..

I don't want to throw a spanner in because I know you blokes do the dyno thing as a business; what is your opinion on the right way round?

I'm very lucky to have a friend who I regard as the best scooter builder there is who can ride mine under load and different conditions, for 20 mins and set it up perfectly because of his many many years experience. I simply can't do it because I don't have the ear/feel etc, I just hang on.

The question then is and in which order:

1. Get a mate like mine
2. Dyno
3. both of the above, dyno first, mate first.

I only ask this because you hear of such and such saying I went to this dyno and it seized up on the way home etc etc.