TS1, Avanti ex box, VHSH30, kytronik curve c, boyesen reeds,

[Adam_Winstone]

Was the ignition the same for the other dyno runs or was it fitted later? I ask this as too much retard shouldn't start to be an issue until running very low or if retarding too early. If you look at Cambridge Lambrettas setup recommendations for their kitted bikes with Varitronic advance/retard, they often suggest that kits with expansions start at 19 dbtdc and retard to considerably less... perhaps less than 15 degrees at higher RPM. This makes me think that your situation could be that it is retarding too far too soon, rather than simply too far (rate vs. starting point), which is why some retard profiles better suit different motor/pipe specs (e.g. Agusto 6000, 7000, 8000 units).

Adam

[hendy]

Adam,

I've got c curve with 22degrees starting point which means that at 5000 it's at 21deg and starts retarding. It's at 14deg by 7800. At 6000, it's around 16deg.

I'm not convinced that's the problem, but I'm removing it just to try. I did intend to have a go today but I couldn't find the number plate!

[hendy]

Adam,

I've got c curve with 22degrees starting point which means that at 5000 it's at 21deg and starts retarding. It's at 14deg by 7800. At 6000, it's around 16deg.

I'm not convinced that's the problem, but I'm removing it just to try. I did intend to have a go today but I couldn't find the number plate!

[hendy]

I should have pointed out that the peak is around 6500.

Also, the first run was with less retard but comes in earlier. Curve a which starts retarding at 4000 from 21 to 16 at 6000.

[Adam_Winstone]

Peak at around 6500...? I'm surprised by it being at such low RPM, even with a touring tune. My old touring tune TS1 was detuned from standard but (base of cylinder machined to reduce transfer timing) still had best power between 7500-8000. When trying pipes with lower RPM range I simply found that they cut a TS1 short, before they reach the revs that most TS1s perform best at.

Were you running this same ignition when it was making better power with an expansion?

[hendy]

Peak at around 6500...? I'm surprised by it being at such low RPM, even with a touring tune. My old touring tune TS1 was detuned from standard but (base of cylinder machined to reduce transfer timing) still had best power between 7500-8000. When trying pipes with lower RPM range I simply found that they cut a TS1 short, before they reach the revs that most TS1s perform best at.

Were you running this same ignition when it was making better power with an expansion?

Yes, same ignition but I really can't remember which curve it was.

It's a touring tune, but not especially tame. 186 exhaust, 126 transfer. Only very slightly below standard TS1 timings.

[Adam_Winstone]

^... similar to the timings that mine ran.

[Bufficus]

This may be of interest?

I have a TS1 253 with EX Box, VHSH and Augusto 7000. Similar port timing to those mentioned above. (64x71 5mm added to top of barrel)

I used to have it paired to a Franspeed Race which made 28BHP and 21ft/lb. (4.8 final drive)

I changed to the EX Box and lost 7 horses and 5 torques.

But, it pulls lovely with an AF 5 speed with final drive of 4.44

I have the Augusto set up so that it's at 18 degrees @ 6000rpm retarding further to 15 degrees @ 8500.

[hendy]

This may be of interest?

I have a TS1 253 with EX Box, VHSH and Augusto 7000. Similar port timing to those mentioned above. (64x71 5mm added to top of barrel)

I used to have it paired to a Franspeed Race which made 28BHP and 21ft/lb. (4.8 final drive)

I changed to the EX Box and lost 7 horses and 5 torques.

But, it pulls lovely with an AF 5 speed with final drive of 4.44

I have the Augusto set up so that it's at 18 degrees @ 6000rpm retarding further to 15 degrees @ 8500.

That is interesting; you're getting about 21bhp. I'd expect mine to make around that with your capacity advantage giving you about 10% on top.

I've been busy lately so haven't touched it, but next weekend I'll be setting it up with 19 degrees fixed. No dyno, just seat of the pants comparison.