Wed Sep 21, 2022 9:14 am

Hooked
vespa 125 vnb1t
Joined: 13 Jul 2011
Posts: 382
Location: antibes , france
 
Hooked
vespa 125 vnb1t
Joined: 13 Jul 2011
Posts: 382
Location: antibes , france
Wed Sep 21, 2022 9:14 am linkquote
hi guys does anyone know about converting rotary to a reed valve , do the cylinder port timings need altering if so what would be the ideal values be ? thanks
Wed Sep 21, 2022 9:41 am

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 08 Stella (for now)
Joined: 16 Jun 2011
Posts: 6498
Location: Nashville
 
Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 08 Stella (for now)
Joined: 16 Jun 2011
Posts: 6498
Location: Nashville
Wed Sep 21, 2022 9:41 am linkquote
Port timings are going to be primarily a function of the cylinder itself, the stroke, and the exhaust. If you're only changing rotary to reed, you can probably ignore the rest of that and just re-jet your carb because it'll flow differently.
Wed Sep 21, 2022 10:08 am

Hooked
Parmakit Primavera -74, Polini Primavera -68, Stock 150 Touring -59, VMC 177 Bajaj Chetak 125 -95
Joined: 22 Jun 2022
Posts: 388
Location: Finland
 
Hooked
Parmakit Primavera -74, Polini Primavera -68, Stock 150 Touring -59, VMC 177 Bajaj Chetak 125 -95
Joined: 22 Jun 2022
Posts: 388
Location: Finland
Wed Sep 21, 2022 10:08 am linkquote
What engine are you looking to convert?
Thu Sep 22, 2022 9:47 am

Hooked
vespa 125 vnb1t
Joined: 13 Jul 2011
Posts: 382
Location: antibes , france
 
Hooked
vespa 125 vnb1t
Joined: 13 Jul 2011
Posts: 382
Location: antibes , france
Thu Sep 22, 2022 9:47 am linkquote
its already done the motor is a vnl 1 on 8" wheels with a pinasco cylinder kit 187 3port , drt reed valve kit so you can keep the si carb , the rotary valve was damaged and nobody wanted to touch it
i measured the timing degrees using this online tool http://ddog.at/stz/rechnen.php
the results are , exhaust duration 181 deg , transfer 134 deg , blow down 24 deg with a 1.5mm base packer
the engine seems under powered so looking any pointers as to why
thanks
Thu Sep 22, 2022 9:50 am

Hooked
Parmakit Primavera -74, Polini Primavera -68, Stock 150 Touring -59, VMC 177 Bajaj Chetak 125 -95
Joined: 22 Jun 2022
Posts: 388
Location: Finland
 
Hooked
Parmakit Primavera -74, Polini Primavera -68, Stock 150 Touring -59, VMC 177 Bajaj Chetak 125 -95
Joined: 22 Jun 2022
Posts: 388
Location: Finland
Thu Sep 22, 2022 9:50 am linkquote
Transfer times sound real high to me.

What exhaust are using?
Thu Sep 22, 2022 10:03 am

Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 3047
Location: Rochester, Minnesota
 
Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 3047
Location: Rochester, Minnesota
Thu Sep 22, 2022 10:03 am linkquote
What is squish measurement? If low end is lacking you could replace that 1.5mm packer with something thinner to improve low end torque.

Last edited by Christopher_55934 on Thu Sep 22, 2022 2:09 pm; edited 1 time in total
Thu Sep 22, 2022 10:34 am

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 08 Stella (for now)
Joined: 16 Jun 2011
Posts: 6498
Location: Nashville
 
Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 08 Stella (for now)
Joined: 16 Jun 2011
Posts: 6498
Location: Nashville
Thu Sep 22, 2022 10:34 am linkquote
FINYoshi wrote:
Transfer times sound real high to me.

What exhaust are using?
Yeah, they sound REALLY high. Like ten degrees or more on the transfer. If it's really built like that, it's not going to go worth a damn.
Thu Sep 22, 2022 11:02 am

Hooked
vespa 125 vnb1t
Joined: 13 Jul 2011
Posts: 382
Location: antibes , france
 
Hooked
vespa 125 vnb1t
Joined: 13 Jul 2011
Posts: 382
Location: antibes , france
Thu Sep 22, 2022 11:02 am linkquote
thanks for the replies so i've been on the calculator with the 1.5mm packer removed it puts the piston .05 above top of the cylinder the squish is 1.2mm at the moment
exhaust 176
transfer 126
blow down 25
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