Wed Feb 24, 2016 5:30 am

Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
 
Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
Wed Feb 24, 2016 5:30 am linkquote
I cracked my engine last night and discovered that my standard crankshaft needs to be replaced.

I am running the Polini 177 setup with a Cosa clutch and a 24mm carb.

What alternatives to a standard crankshaft would you guys suggest, now that the engine is open and everything is possible? Cut crank? Bigger Carb? Or go Reed?

Last edited by aklimo on Wed Feb 24, 2016 9:01 pm; edited 1 time in total
Wed Feb 24, 2016 5:44 am

Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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Location: That bushfire place
 
Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 4097
Location: That bushfire place
Wed Feb 24, 2016 5:44 am linkquote
What motor?
What other mods?
Need many more details...
What are you trying to acheive ?
What type of riding do you do?
What id your budget?
Wed Feb 24, 2016 5:56 am

Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
 
Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
Wed Feb 24, 2016 5:56 am linkquote
Its a PX125 motor with a 177cc Polini kit. Cosa2 clutch, 24mm carb. Its currently in a '68 Sprint but I am transferring it into a '59 VNA with 8inch tires.
Trying to get some more RPM and power out of it to compensate for the smaller tires.
Budget is (as usual) limited. Was thinking of the Racing Crankshaft by MAZZUCCHELLI.
Riding is more touring.
Wed Feb 24, 2016 6:00 am

Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
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Location: That bushfire place
 
Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 4097
Location: That bushfire place
Wed Feb 24, 2016 6:00 am linkquote
Cool.

I like the Mazza cranks & so far have not destroyed any.
Check out the SeriePro version.

Does that mean you are going from 10" to 8"?
If so you will need a new primary.
Do you know which gearbox is in it?

Is it running the Polini or Worb5 piston?

How extensive is the porting?

What pipe?

Photos?

Have a read here, there may be a few tips.
modify VBC 2-port - Pissed n Broke
Wed Feb 24, 2016 8:00 am

Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
 
Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
Wed Feb 24, 2016 8:00 am linkquote
Yes, going from 10" to 8".

I think its a standard 125 gear box. 4th gear has 36 teeth.

Its running a Polini piston and no porting has been done.

I got the SIT Sport pipe for it.



Wed Feb 24, 2016 2:50 pm

Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 4097
Location: That bushfire place
 
Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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Location: That bushfire place
Wed Feb 24, 2016 2:50 pm linkquote
here is what happens when you change wheel size ONLY.

While motor is apart, its a great time to count all the teeth on each gear, then we can work on ratios


current gearing w 3.50 x 10


current gearing with 3.50 x 8

Wed Feb 24, 2016 8:36 pm

Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
 
Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
Wed Feb 24, 2016 8:36 pm linkquote
So I counted the gears and it looks as follows:

Primary: 21/68

First: 12/58
Second: 12/42
Third: 17/38
Fourth: 21/36

I ran the Gearing Calculator with those on 10" wheels and ended up with 113km/h @ 8000RPM

I changed the clutch ratio to 23/68 and the fourth to 21/35 and ended up at 114km/h @ 8000RPM with 8" wheels.

Does that setup make sense? Can I simply swap the 21 clutch cog for a 23? And same with the 35 teeth 4th gear? Would you even go less teeth on the 4th?


Current Setup with 10" wheels


8 inch wheels, 23 teeth clutch cog, 35 teeth 4th gear


8 inch wheels, 23 teeth clutch cog, 34 teeth 4th gear

Wed Feb 24, 2016 9:16 pm

Molto Verboso
Joined: 15 Nov 2008
Posts: 1899
Location: Seattle
 
Molto Verboso
Joined: 15 Nov 2008
Posts: 1899
Location: Seattle
Wed Feb 24, 2016 9:16 pm linkquote
Re: Crankshaft / gearing ideas for Polini 177 PX125 on 8&quo
aklimo wrote:
I cracked my engine last night and discovered that my standard crankshaft needs to be replaced.

I am running the Polini 177 setup with a Cosa clutch and a 24mm carb.

What alternatives to a standard crankshaft would you guys suggest, now that the engine is open and everything is possible? Cut crank? Bigger Carb? Or go Reed?
well, first i'd ask what kind of bike you want to have when you are finished.
Wed Feb 24, 2016 9:29 pm

Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 4097
Location: That bushfire place
 
Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 4097
Location: That bushfire place
Wed Feb 24, 2016 9:29 pm linkquote
Looking good,
I'll have a look tonight if I get time... I've got a Carb to rebuild & need to get ready for a Rally/Long Ride this weekend so have a HEAP to do tonight.

"Riding is more touring."

Then you will need to be able to go 100kmh/60mph at a low/mid-rev range, & chug along happily all day at that revs/speed.
So calulate at 5500rpm, & see what speed you can come up with in 3rd/4th close together

NOTE: 8000rpm is a MAX rev, not all motors can do this happily
I also check about 3500 (or 4000)-5500-7500 for low-mid-high revs... with 8000 as 'bonus-revs', as there is bugger all chance it will survive at that sort of revs all day.

NOTE: You mention 12/42 in your box, but the calculator shows 13/42.
may pay to re-check.
Also, consider a longer 2nd, as it will have about the same 'gap' as 3rd to 4th

Last edited by SubEtherBASS on Wed Feb 24, 2016 10:36 pm; edited 2 times in total
Wed Feb 24, 2016 10:03 pm

Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
 
Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
Wed Feb 24, 2016 10:03 pm linkquote
Re: Crankshaft / gearing ideas for Polini 177 PX125 on 8&
rob hodge wrote:
aklimo wrote:
I cracked my engine last night and discovered that my standard crankshaft needs to be replaced.

I am running the Polini 177 setup with a Cosa clutch and a 24mm carb.

What alternatives to a standard crankshaft would you guys suggest, now that the engine is open and everything is possible? Cut crank? Bigger Carb? Or go Reed?
well, first i'd ask what kind of bike you want to have when you are finished.
I had this engine in a Sprint and was happy with the performance. I am moving the engine into a VNA with 8inch wheels and want to maintain the same top speed and performance with the smaller wheels.

Now that the standard crank needs to be replaced I am thinking on adding a performance crank, but am thinking about the gearing to maintain the same speed as before.
Thu Feb 25, 2016 4:08 am

Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1754
Location: UK (South East)
 
Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1754
Location: UK (South East)
Thu Feb 25, 2016 4:08 am linkquote
I use 23/68 in my DR177 motor. It uses a late PX150 EFL box, same as a PX200. I'm on 10" wheels and it's a good match for the power that I make. With 8s you will have pretty short gearing combined with a fairly powerful kit. As you see with the gearing calculator, you'll be at 8000 RPM in 4th gear if you want to do 70MPH. Over a sustained distance (touring), this will not be a comfortable ride IMO. If you want a sporty touring setup, I would consider at least 23/65 from a PX200, or even the new Malossi upgear kits for Cosa clutches (23/64 or 24/63).

If you do go 23/68, you cannot use the stock Piaggio 23T with the 67/68 primary. I bought the special DRT 23T for this reason.
Thu Feb 25, 2016 5:03 am

Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 4097
Location: That bushfire place
 
Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 4097
Location: That bushfire place
Thu Feb 25, 2016 5:03 am linkquote
I never considered that the Cosa uses a different primary.
Hmmm, i never researched their options, BUT it all starts with getting the right primary.
Thu Feb 25, 2016 5:27 am

Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1754
Location: UK (South East)
 
Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1754
Location: UK (South East)
Thu Feb 25, 2016 5:27 am linkquote
SEB, primary cog is good to go, but the Piaggio 23T Cosa clutch gear will not mate with 67 and 68T primaries. You need the DRT 23T if you want to upgear a 67/68 (PX125/150/VBC etc.) beyond 22T clutch.
Thu Feb 25, 2016 8:33 am

Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
 
Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
Thu Feb 25, 2016 8:33 am linkquote
swa45 wrote:
I use 23/68 in my DR177 motor. It uses a late PX150 EFL box, same as a PX200. I'm on 10" wheels and it's a good match for the power that I make. With 8s you will have pretty short gearing combined with a fairly powerful kit. As you see with the gearing calculator, you'll be at 8000 RPM in 4th gear if you want to do 70MPH. Over a sustained distance (touring), this will not be a comfortable ride IMO. If you want a sporty touring setup, I would consider at least 23/65 from a PX200, or even the new Malossi upgear kits for Cosa clutches (23/64 or 24/63).

If you do go 23/68, you cannot use the stock Piaggio 23T with the 67/68 primary. I bought the special DRT 23T for this reason.
Can I just replace my current primary with the 65 teeth primary gear from the PX200 or do I have to replace the whole tree?
And could I use the stock 23 teeth Piaggio clutch cog after that?
Do you think I should go taller with the 4th after that?
Fri Feb 26, 2016 12:34 am

Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1754
Location: UK (South East)
 
Molto Verboso
One or two fun scoots....nothing too precious
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Posts: 1754
Location: UK (South East)
Fri Feb 26, 2016 12:34 am linkquote
I thought you could put the 65T primary on a P125 tree, but I discovered otherwise three weeks ago when trying to do exactly that on a 125 TS motor, which is like a very early P125 engine, but with some nuances. It's definitely possibly with the later PX150 engines, which have the same gearbox as a PX200, apart from primary and clutch, and I'd like to think the same is true for late PX125 gearboxes.

Whatever, there's a lot more work to change the primary, so you may want to think 23/68, which is the best you'll get without ripping the motor apart.

What year/type is your 125 motor? Your original post states that it's PX125, which to me means the later EFL type.
Sat Feb 27, 2016 7:50 pm

Molto Verboso
Joined: 15 Nov 2008
Posts: 1899
Location: Seattle
 
Molto Verboso
Joined: 15 Nov 2008
Posts: 1899
Location: Seattle
Sat Feb 27, 2016 7:50 pm linkquote
Re: Crankshaft / gearing ideas for Polini 177 PX125 on 8&
aklimo wrote:
rob hodge wrote:
aklimo wrote:
I cracked my engine last night and discovered that my standard crankshaft needs to be replaced.

I am running the Polini 177 setup with a Cosa clutch and a 24mm carb.

What alternatives to a standard crankshaft would you guys suggest, now that the engine is open and everything is possible? Cut crank? Bigger Carb? Or go Reed?
well, first i'd ask what kind of bike you want to have when you are finished.
I had this engine in a Sprint and was happy with the performance. I am moving the engine into a VNA with 8inch wheels and want to maintain the same top speed and performance with the smaller wheels.

Now that the standard crank needs to be replaced I am thinking on adding a performance crank, but am thinking about the gearing to maintain the same speed as before.
If all you want to do is achive similar roadspeed to stock late 150 road speed but on 8's, you will pretty much need to swap both the cush gear and the clutch drive year.

you have pretty much two options; staying with the 68 tooth primary really isn't an option.

from that point, you need to decide if you want the optuon to go higher, or to cheap out.

the cheaper route is to go to a p200 65-tooth gear based setup. you'd need to go to a DRT 24 cog and the stock 65 tooth helical. setup.

this is slightly cheaper, but limits your upgrade path. it's the highest you can go without swapping the primary again.

here is the comparison: open them in windows side-by-side and compare.

stock:
http://www.scooterhelp.com/cgi-bin/vespa.gear.calc.pl?04_mph_kph=MPH&00_primary=21/68&02_gearbox=6&03_tire=54

using the 24/65 combo:

http://www.scooterhelp.com/cgi-bin/vespa.gear.calc.pl?04_mph_kph=MPH&00_primary=24/65&02_gearbox=6&03_tire=46

the better option is to go to the DRT 62 straight cut gear.

you'd want the 23/62 setup. this leaves you with the option of 2 additional 4% bumps later by just swapping the clutch. here's that setup charted:

23/62

http://www.scooterhelp.com/cgi-bin/vespa.gear.calc.pl?04_mph_kph=MPH&00_primary=23/62&02_gearbox=6&03_tire=46

24/62

http://www.scooterhelp.com/cgi-bin/vespa.gear.calc.pl?04_mph_kph=MPH&00_primary=24/62&02_gearbox=6&03_tire=46

25/62

in all honesty, with a 177 and a 24 carb, i'd probably bump to the 24/62. this can be done without even dropping the crank once the 62 tooth gear is in the engine.

as for crank, if you want it racier, go with a cut crank. if you like the power delivery, stay standard. if you want more than a little racier, or a full race setup, cut your own. the norrie kerr manual is a good start to learning the geometry needed.
Sun Feb 28, 2016 7:35 am

bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
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Location: So Cal
 
bodgemaster
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Joined: 26 Sep 2013
Posts: 6106
Location: So Cal
Sun Feb 28, 2016 7:35 am linkquote
Good info rob. I'm considering a long stroke for our Super project. What do you say? Worth the extra cheese? Any downsides?

http://www.sip-scootershop.com/en/products/long+stroke+crankshaft+pinasco+_46006000
Sun Feb 28, 2016 7:42 am

Molto Verboso
Joined: 15 Nov 2008
Posts: 1899
Location: Seattle
 
Molto Verboso
Joined: 15 Nov 2008
Posts: 1899
Location: Seattle
Sun Feb 28, 2016 7:42 am linkquote
SoCalGuy wrote:
Good info rob. I'm considering a long stroke for our Super project. What do you say? Worth the extra cheese? Any downsides?

http://www.sip-scootershop.com/en/products/long+stroke+crankshaft+pinasco+_46006000
honestly unless you've researched and learned about how port timings interplay and knpw how to measure and adjust them i've always kind of shied people away from them. yo ucan go next level with them but the learning curve gets steeper than just bolting on.

or, you can bolt it in and hope you get lucky.
Sun Feb 28, 2016 11:57 pm

Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 4097
Location: That bushfire place
 
Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 4097
Location: That bushfire place
Sun Feb 28, 2016 11:57 pm linkquote
SoCalGuy wrote:
Good info rob. I'm considering a long stroke for our Super project. What do you say? Worth the extra cheese? Any downsides?

http://www.sip-scootershop.com/en/products/long+stroke+crankshaft+pinasco+_46006000
Nah.
I cant remember why, but even i decided against it!
Possibly something to do with longer stroke = faster piston travel = heat = something technical about loss of ??? But gain of ???.
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