Rapido classic 225, Dyno run...

[J1MS]

Was hoping to get a run on Sean's Dyno, but when we tried to book there were no spaces to fit us in.... So its going to Reedspeeds tomorrow...
I want to see the power curve and the air fuel ratio through the rev range... not really bothered about peak power figures as I'm only expecting around 14 HP maximum as its just a standard 225 Classic but blended running a reamed out 22mm Jettex and 48mm Clubman...
The main reason I'm taking it is to see how far off the jetting is, as its hard to dial in a reamed out 22 as there not too adjustable... I have only modified the Atomiser slightly from standard and fitted a 48 pilot jet & 128 main jet but apart from that its a standard off the shelf Rapido, but the cylinder head has been reworked to give a 50% squish, running at 9-1 with 1.1mm clearance... The engine has now covered 3000 miles and is on its 3rd set of rings so a dyno should give some good feed back...
Its a shame I couldn't get a slot on Scooterotica's own dyno as it would have been good to meet Sean.... Maybe next time..

I Hope to post the results tomorrow... all being well and the motor doesn't explode :shocking: ... It feels a little revy for a 225 & the dyno should show what it can or cant rev to... I think it should rev past 8000 in top gear & I think peak power is around 6500rpm... but Tomorrow will tell..

[J1MS]

Dyno run today... No big surprises it was about where I thought it would be 14+ bhp and around 8000 revs in top...

The jetting was pretty much ok just a little rich at the top end, so the 128 mainjet was changed down to a 125...


A third gear run after down jetting, showed 14.7bhp... which is pretty much all I would have expect as believe it or not the bore to piston clearance after only 3000 miles is staring to wear a little this was checked on the last change of rings..

When the barrel was newer and the bore tighter the scooter had a little more pull and reved a little cleaner, topping 70+ on the SatNav pulling 7500 revs on the rev counter...

Looking to reline the barrel and fit a jap piston some time soon... Maybe a KDX or TS250 piston...

But as I said the barrel is totally standard Inlet and Exhaust are blended to the barrel 22mm jetex reamed and a 48 clubman GP 200 Italian gearing 19x46 sprockets... The scooter still pulls upwards of 70 mph on the road it would never without a downhill stretch and tail wind hit the speed it did on the dyno... But I thought I* would show the result of a near s tandard setup with relatively low compression for a Kit barrel..

[tony]

Hi ,mate.. how are you?
Good to see an honest dyno run tbh!
I see you havent got a afr scale..? Jerry is a top guy but does his dyno have a load device?

[sean brady scooters]

a bigger carb/better pipe.......tuned a bit.......and set up with gearing to suit...........
i,m sure these should be able to produce at least 18/20 torque...........

[tony]

Mikey, the lad who races/works at Kegra has a 205 version with good figures. It has a 3000 rpm powerband hence why he was staying with stuart day down the straights at Lydden.
They have loads of potential.

[J1MS]

No Tony, I dont think it has a loading application, it just spins up a heavy drum, like most dynos... Fuel air ratio hasn't been printed off & I never noticed till I got home... the jetting was pretty much right which I thought it was I will put the third gear run up tomorrow before and after mainjet change...

Wanted a base line really, for when I reline and fit a better piston... but thought I would share what it was and its limitations... Its actually not a bad engine to ride, not fast but steady speed and fairly cheap for what it is.... if it didnt eat piston rings so quickly..

[tony]

pm

[sean brady scooters]

i,m looking forward to having the opportunity to tune one of these kits/set ups...................
knowing that with the right bits and bobs these could and should work so much better...........
after all ,the average of 14 torque from a 250 is pretty dismal...................

[J1MS]

i,m looking forward to having the opportunity to tune one of these kits/set ups...................
knowing that with the right bits and bobs these could and should work so much better...........
after all ,the average of 14 torque from a 250 is pretty dismal...................

Its a 225, with nearer to 5 thou piston clearance when it last got new rings, which now is probably over 5 thou clearance... thats maybe where some of the torque figure has gone...

But you are certainly right about the potential... A high comp head, better tolerances, a more wear resistant bore, a decent piston with quality wire rings, an exhaust port timing a little over 180 degree and nearer to 70 percent width, larger inlet area both width and timing, a little work on the transfers and case, a good carb and expansion tailored to suit... It would possibly increase torque considerably and up the bhp to probably double...and still keep a decent power band...

[Mel K]

a bigger carb/better pipe.......tuned a bit.......and set up with gearing to suit...........
i,m sure these should be able to produce at least 18/20 torque...........

I'm sure it would too and after 30 odd years of building and tuning Lambretta engines J1MS knows this too. But I think as J1MS stated he "wanted to show the result of a near standard set-up"