Group 4 Race Engine - 2004 - 31.5HP Rapido

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paulmgreen
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ebay user ID: hgracingscooterparts
Main scooter: Lambretta Group 4 Race 200
Location: Grantham
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Wed Jan 07, 2009 12:47 am

`well pleased today..... with a little Christmas present from Replay Scooters!

I picked up my 2009 re-worked race engine this morning! My original race engine was tuned and built by Chalky White at Replay Scooters. He had built it as a ( relatively ) conservative motor, with a broad spread of power. It served me well for my return to racing after 13 years away........ it was dyno'd at 24 HP which was enough to scare me anyway!


I met Chalky at Cadwell Park, and we had quite a long chat about the motor. He had built it with the intention of racing it himself, but never really got around to it but he was delighted to see someone out on the track on one of his motors.

So...... fast forward....... Chalky has had the engine for a few weeks and has re-worked the top end. We now have a new crank fitted, with a jap con rod. The Rapido barrel has been ported some more, with somewhat larger (!) inlet and exhaust ports and transfers, a new BGM stator is now providing the sparks, and is coupled with the Agusto Advance Retard box.

I collected it this morning. I took my frame down and we re-fitted the engine and then did the exciting bit! The Dyno Run!!!!!!

I think its fair to say both of us were well pleased with the outcome...... 3rd gear power run showed an increase in power to 31.5HP, with 20 maximum torque! We have a real broad spread of power which will suit my riding style

I'll publish the dyno results and printouts in a few days when I have access to a scanner,

but in the mean time.....
7000 revs produces 25HP
7700 revs produces 30HP and peak torque (20.7)
8158 revs produced peak power 31.5HP
9000 revs is still producing 30.6 HP
9500 revs still 26HP
so as you can see a nice broad spread!

Can't wait to be helling down a straight at Mallory grinning and squealing!

~~~~~

Dyno Chart!
Image
YouTuve Vlog channel - https://www.youtube.com/channel/UCEhrgL ... vY_4Px2WTg

www.JPPLambretta.co.uk

Sponsors Replay Scooters JPPLambretta

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RinB
Posts: 321
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Main scooter: Reflections in Blue
Location: Grimsby
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Wed Jan 07, 2009 12:50 am

Wolf whisle twittwoooo Nice curves :twisted:
If its made of Metal Fettle it !!

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paulmgreen
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Posts: 589
Joined: Sun Jan 04, 2009 4:34 pm
ebay user ID: hgracingscooterparts
Main scooter: Lambretta Group 4 Race 200
Location: Grantham
Contact:

Wed Jan 07, 2009 12:56 am

Carburation blip between 6 and 7,000 revs though ......... discuss! .......
YouTuve Vlog channel - https://www.youtube.com/channel/UCEhrgL ... vY_4Px2WTg

www.JPPLambretta.co.uk

Sponsors Replay Scooters JPPLambretta

fishi
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Wed Jan 07, 2009 6:41 pm

which exhaust have you used at the dyno run ?? perhaps the exhaust is responsable for the carburation blip between 6-7000 revs

fishi

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RinB
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Main scooter: Reflections in Blue
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Wed Jan 07, 2009 9:13 pm

paulmgreen wrote:Carburation blip between 6 and 7,000 revs though ......... discuss! .......
Paul looking at this if Im reading right and your Lambda probe are calculating Air Fuel Ratio and the Lambda is a stoiciometric measurement of afr

It looks to me that as you hit the power from say 4000 rpm to 6200rpm ave AFR is 13:1 which is not bad .

But from 6200rpm 7200rpm you do have the blip down to ave AFR of 10.2:1 this dip is showing a bad enrichment.
But onces you have driven through the blip your AFR ave leans back out to 12:1 which looks good to me
and the fact that you reach your peak power here is good as it is richer then the start of the power (4000) at 13:1.
Ie. your richening at peak and not leaning off to much

So thats my prognoses hope that helped
But Im no master at the dyno Al Diablo should give better clues and may even put me right.

Smiffy
If its made of Metal Fettle it !!

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paulmgreen
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Joined: Sun Jan 04, 2009 4:34 pm
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Main scooter: Lambretta Group 4 Race 200
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Wed Jan 07, 2009 10:23 pm

cheers mate..
YouTuve Vlog channel - https://www.youtube.com/channel/UCEhrgL ... vY_4Px2WTg

www.JPPLambretta.co.uk

Sponsors Replay Scooters JPPLambretta

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