Induction Port Timing
Post Reply    Forum -> Not-So-Modern
Author Message
Molto Verboso
2005 PX150 In a Love-Hate Relationship with a 2-Stroke Vespa Since 2007
Joined: 01 Sep 2007
Posts: 1743

Mon May 19, 2014 11:37 am quote
Has anyone measured the induction port timing with a degree wheel for a 150 or know what it is, i.e, opens at (x) BTDC and closes at (y) whatever?

I've looked in the forums and on the net and can't find it.

Thanks
Hooked
Old douglas ..smallie with polini 115..super with nasco 177
Joined: 07 Nov 2013
Posts: 498
Location: New Zealand
Mon May 19, 2014 4:08 pm quote
Ive got the numbers at home so ill check tonite...if you cant wait then its Easy enough to look down the carb hole to the crank and with a degree disc on the flywheel Find TDC and then zero the disc .Ps I heavily modified a 150 super crank....and after doing the research cut 11mm off the leading face using a standard hack saw and then cleaning it via a dremmel..ie opened intake earlier and polished/rounded all the surfaces
Huge effect with an old DR 177 barrel and GS piston with 4thou clearance and a 24 delly with sip road pipe..122 main... 140/160 BE3 and a 4.0 slide to richen the midrange
Molto Verboso
2005 PX150 In a Love-Hate Relationship with a 2-Stroke Vespa Since 2007
Joined: 01 Sep 2007
Posts: 1743

Mon May 19, 2014 6:23 pm quote
I've measured mine which has been slightly modified by an unknown amount and it opens at 117deg BTDC and closes at 46 ATDC. I was wondering how close to stock that still is.
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6414
Location: Victoria, Australia
Mon May 19, 2014 7:08 pm quote
Excuse me for butting in to your thread Jim!
Bluecati wrote:
...and a 4.0 slide to richen the midrange
Bluecati, did you try the 3 different slides? Was there much noticeable difference between them?
Molto Verboso
Joined: 15 Nov 2008
Posts: 1894
Location: Seattle
Tue May 20, 2014 10:07 am quote
pdxjim wrote:
I've measured mine which has been slightly modified by an unknown amount and it opens at 117deg BTDC and closes at 46 ATDC. I was wondering how close to stock that still is.
I have a few stoxk written down at home i think.

Although i have to ask- do you have a copyh of the norrie4 ker manual? If you want to play with inlet timings it's worth reading.
Molto Verboso
2005 PX150 In a Love-Hate Relationship with a 2-Stroke Vespa Since 2007
Joined: 01 Sep 2007
Posts: 1743

Tue May 20, 2014 10:27 am quote
I'm sorry, it probably would've helped if I'd said why I was asking in the first place.

I do have that manual for my own education and have looked through it, though I'm not interested in tuning.

What I was hoping to determine was whether my slightly mod'd inlet port is compatible with a stock top-end or would there be problems? I can't tell from the Kerr book or not. I'm thinking maybe not, but only someone experienced with tuning would know.
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6414
Location: Victoria, Australia
Tue May 20, 2014 1:52 pm quote
Put up a pic and we can compare it.
Molto Verboso
Joined: 15 Nov 2008
Posts: 1894
Location: Seattle
Tue May 20, 2014 1:53 pm quote
pdxjim wrote:
I'm sorry, it probably would've helped if I'd said why I was asking in the first place.

I do have that manual for my own education and have looked through it, though I'm not interested in tuning.

What I was hoping to determine was whether my slightly mod'd inlet port is compatible with a stock top-end or would there be problems? I can't tell from the Kerr book or not. I'm thinking maybe not, but only someone experienced with tuning would know.
Well that's another question. If you are at 163 ish degrees open, that's very conservative, and virtually stock. Road tunes on stock top ends call for around 170-185 degfrees. Kits can go as high as 220-230, alt6hough more is not necissarily better.

It's all in the norrie kerr book, including a ballpark for stock. Reread that chapter.,
Molto Verboso
2005 PX150 In a Love-Hate Relationship with a 2-Stroke Vespa Since 2007
Joined: 01 Sep 2007
Posts: 1743

Tue May 20, 2014 2:41 pm quote
According to the book, it appears I'd have to do my own port-mapping and inlet timings to determine it for sure and I don't even have the stock top yet.

Sigh, I was hoping that someone had the quick answer. I agree it's not much off and is probably fine.
Molto Verboso
Joined: 15 Nov 2008
Posts: 1894
Location: Seattle
Tue May 20, 2014 3:06 pm quote
pdxjim wrote:
According to the book, it appears I'd have to do my own port-mapping and inlet timings to determine it for sure and I don't even have the stock top yet.

Sigh, I was hoping that someone had the quick answer. I agree it's not much off and is probably fine.
I gave you the quick answer.
Molto Verboso
2005 PX150 In a Love-Hate Relationship with a 2-Stroke Vespa Since 2007
Joined: 01 Sep 2007
Posts: 1743

Tue May 20, 2014 3:19 pm quote
Thank you. I'll reread.
Hooked
Old douglas ..smallie with polini 115..super with nasco 177
Joined: 07 Nov 2013
Posts: 498
Location: New Zealand
Tue May 20, 2014 7:07 pm quote
Just did NZ milli meglia scooter challenge with the 4.0 slid
Nah ..couldn't find my numbers for the port timings of a stock super (and Im a hoarder so it bothers me)
It should take you only ten minutes...
As to the 4.0 slide....I went with this to richen up the midrange. I had a couple of siezes on a cast iron pinasco 177.....and during the run period I was mostly in the midrange...and seizing regular and quickly
I just recently did the "1000 mile in 4 days" scooter challenge here in NZ.....ie 1500kms.....400kms takes 8 to 9 hours in the saddle per day. Every single road condition was experienced and I had no seizes at all...this includes thrashing.at WOT..racing other scoots....riding hard up hill into wind
Another scoot with the same top end,pipe ,carb and jets but with a NORMAL slide was seizing every hour or so.
I now swear by the 4.0...especially for touring

I went straight to the 4.0 and didn't test any others. It was noticeably stronger (more power,)in the midrange..kind of like when the air fuel mix is too rich but WITHOUT the associated bog of an over rich engine

seems they got around emission laws by leaning the midrange via cutaways in the slide.

If you have seized lately..consider the midrange jetting....not just bigger mains
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6414
Location: Victoria, Australia
Tue May 20, 2014 8:23 pm quote
pdxjim wrote:
Sigh, I was hoping that someone had the quick answer. I agree it's not much off and is probably fine.
If you put up a picture then we can compare it. If it's not noticeably different from a stock pad, then it's not going to make a real difference. Come on Jim, I know you have it pieces!
Bluecati wrote:
If you have seized lately..consider the midrange jetting....not just bigger mains
I ride a tuned Vespa. Of course I've seized lately!
Sounds like a plan, I'll put it on my list. Cheers.
Hooked
78 P200 05 PX150
Joined: 06 Jul 2010
Posts: 214
Location: Fort Collins, CO
Wed May 21, 2014 7:54 am quote
Hot Rod Al made me a crank for my kitted P200. He cut the opening and closing sides of the web. My measurements were:

Intake Opening - 115deg BTDC
Intake Closing - 61deg ATDC
Intake Duration - 176deg

The intake area of the cases were cleaned up but I didn't change the opening length in the case. P200 Performance Build-Up (Page 2)

Chuck
Land of 10,000 Scoots Rally   Vespa Wasp Pin Badges   AF1 Racing Vespa Austin
Post Reply    Forum -> Not-So-Modern
[ Time: 0.2433s ][ Queries: 24 (0.0460s) ][ Debug on ]