OP
@tailgate avatar
UTC

Hooked
"worlds 2nd fastest"74'super 150 . 79'p177x ,1983 lml 150, 2007aprilia sxv 450.
Joined: UTC
Posts: 152
Location: vancouver bc
 
Hooked
@tailgate avatar
"worlds 2nd fastest"74'super 150 . 79'p177x ,1983 lml 150, 2007aprilia sxv 450.
Joined: UTC
Posts: 152
Location: vancouver bc
UTC quote
Hi...i have a 79 p150x. With a polini 177 kit...matched ports...and 24-24g...si carb. I am going to buy a cut crank to extend intake timing.....but for 25 bucks more i can get the same crank with 60mm con rod versus the stock.57mm.....i am a good mechanic so i can put it in no problem.....my question is.....are there any p series owners out there,who have done this...and what are the drawbacks.....or should i stick with the 57mm rod......thanks...tailgate.
tips are helpfull too.example...widening exhaust port....taller gears. Etc.....is excessive heat an issue.thanks.
Forum member supplied image with no explanatory text
@ginch avatar
UTC

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
Joined: UTC
Posts: 8697
Location: Victoria, Australia
 
Veni, Vidi, Posti
@ginch avatar
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
Joined: UTC
Posts: 8697
Location: Victoria, Australia
UTC quote
Got a link to the two cranks? Not Malossi I hope?


Edit: I meant Mazuchelli not Malossi! The cheaper Mazz cranks have been getting some not so good reviews lately.
⚠️ Last edited by Ginch on UTC; edited 1 time
OP
@tailgate avatar
UTC

Hooked
"worlds 2nd fastest"74'super 150 . 79'p177x ,1983 lml 150, 2007aprilia sxv 450.
Joined: UTC
Posts: 152
Location: vancouver bc
 
Hooked
@tailgate avatar
"worlds 2nd fastest"74'super 150 . 79'p177x ,1983 lml 150, 2007aprilia sxv 450.
Joined: UTC
Posts: 152
Location: vancouver bc
UTC quote
Howdy
Its a mazuchelli long strfoke for px ....cost 165$ from esseyepee.in. Deutchland....138degree intake timing ...i think stock was 12 degrees.....but i will probably buy it....cant be anyworse than the 35 year old stock crank...thats in it now.....huh? [/i]
@sfvsr avatar
UTC

Ossessionato
a lambretta or two
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Location: San Francisco
 
Ossessionato
@sfvsr avatar
a lambretta or two
Joined: UTC
Posts: 3724
Location: San Francisco
UTC quote
I think you mean 60mm stroke and not a "60mm con rod."

When you mock it up, make sure the piston doesn't
1) bottom out on the case,
2) strike the head.

To do it properly you will need to know the port timings in degrees for your transfers and exhaust ports. Make absolutely sure these port timings are possible with the exhaust you will be running. If the port timings are not correct you will need to change them by raising or lowering the barrel. This means you can raise it with a packer or machine the bottom of the cylinder to lower the ports. With the ports correct, you can then decide what to do about the fact that your piston will most likely be sticking out the top of the cylinder so much you can't install the head. Call up Worb5 or Hot Rod Al and have a head modified.
@oopsclunkthud avatar
UTC

Banned
3:5
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Banned
@oopsclunkthud avatar
3:5
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Location: San Francisco
UTC quote
Personally I'm not a big fan of the long stroke cranks. They increase the max piston acceleration and therefor lower the RPM where the rings start to float. The crank on the largeframe vespa is about the weakest link in the design. The long stroke crank will see even higher stresses and be that much closer to failure.

I have seen them used successfully care must be taken to keep the power and RPM down to a reasonable level.
@sfvsr avatar
UTC

Ossessionato
a lambretta or two
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Posts: 3724
Location: San Francisco
 
Ossessionato
@sfvsr avatar
a lambretta or two
Joined: UTC
Posts: 3724
Location: San Francisco
UTC quote
It's sweet when the rod shoots through the bottom of the case.
@fastfrog avatar
UTC

Hooked
PX125,200, T5, SS180,TS125 and some more...
Joined: UTC
Posts: 203
Location: Paris, Taxes!
 
Hooked
@fastfrog avatar
PX125,200, T5, SS180,TS125 and some more...
Joined: UTC
Posts: 203
Location: Paris, Taxes!
UTC quote
SFvsr wrote:
It's sweet when the rod shoots through the bottom of the case.
is that a metaphor?
@sfvsr avatar
UTC

Ossessionato
a lambretta or two
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Posts: 3724
Location: San Francisco
 
Ossessionato
@sfvsr avatar
a lambretta or two
Joined: UTC
Posts: 3724
Location: San Francisco
UTC quote
fastfrog wrote:
SFvsr wrote:
It's sweet when the rod shoots through the bottom of the case.
is that a metaphor?
Euphemisms wrapped in metaphor.

I guess I could've squeezed in the phrase "finger blaster" somehow.
@vader19 avatar
UTC

Mr. Clean
P,SUPER,V90, 50 Special
Joined: UTC
Posts: 10205
Location: This is't my locker!
 
Mr. Clean
@vader19 avatar
P,SUPER,V90, 50 Special
Joined: UTC
Posts: 10205
Location: This is't my locker!
UTC quote
SFvsr wrote:
fastfrog wrote:
SFvsr wrote:
It's sweet when the rod shoots through the bottom of the case.
is that a metaphor?
Euphemisms wrapped in metaphor.

I guess I could've squeezed in the phrase "finger blaster" somehow.
Better you didn't. You moving to the woods ? Kit house?
@sfvsr avatar
UTC

Ossessionato
a lambretta or two
Joined: UTC
Posts: 3724
Location: San Francisco
 
Ossessionato
@sfvsr avatar
a lambretta or two
Joined: UTC
Posts: 3724
Location: San Francisco
UTC quote
Vader19 wrote:
You moving to the woods ? Kit house?
Building a kit home is the plan. But as a get-away from the zombies and techies buying $65 cheesburgers here in SF.
@fastfrog avatar
UTC

Hooked
PX125,200, T5, SS180,TS125 and some more...
Joined: UTC
Posts: 203
Location: Paris, Taxes!
 
Hooked
@fastfrog avatar
PX125,200, T5, SS180,TS125 and some more...
Joined: UTC
Posts: 203
Location: Paris, Taxes!
UTC quote
[quote="Vader19".. You moving to the woods ? Kit house?[/quote]

Woods or bush?

(I shoud stop froging that thread!)
@vader19 avatar
UTC

Mr. Clean
P,SUPER,V90, 50 Special
Joined: UTC
Posts: 10205
Location: This is't my locker!
 
Mr. Clean
@vader19 avatar
P,SUPER,V90, 50 Special
Joined: UTC
Posts: 10205
Location: This is't my locker!
UTC quote
To answer your question, I have 60mm stroke cranks in all three large frames. It's not necessary to go long stroke but I get more torque v a 57 (1st hand experience not hearsay)
I also like having the instant 1.5mm stroke compensation to play with (cylinder base and head gaskets to play with raise the head more torque, raise the cylinder more rev/top end). Unless you use a head with built in compensation.
OP
@tailgate avatar
UTC

Hooked
"worlds 2nd fastest"74'super 150 . 79'p177x ,1983 lml 150, 2007aprilia sxv 450.
Joined: UTC
Posts: 152
Location: vancouver bc
 
Hooked
@tailgate avatar
"worlds 2nd fastest"74'super 150 . 79'p177x ,1983 lml 150, 2007aprilia sxv 450.
Joined: UTC
Posts: 152
Location: vancouver bc
UTC quote
awsome
tips I really appreciate the advice...I think I will buy the long stroke crank and play around with the port timings....and vader thanks for the real world advice...that's what I was looking for ...and thanks to all the posters ...for helping me out...!
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