Puzzling no movement on piston when kick starting
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Enthusiast
Vespa Sprint
Joined: 28 Sep 2013
Posts: 89
Location: South Africa
Sun Nov 04, 2018 11:22 pm quote
Hi Guys,

I almost feel rather sheepish asking this question but have exhausted what the problem might be. I have a number of vespas, all different models and currently working on a Sprint 150 engine and having put it all together when I kick the engine over the piston crank doesn't move up and down. It must be something to do with the clutch, even though I don't have the clutch cable attached (no tension) it just seems to be a soft kick on the kickstart even without the cylinder head on the barrel.

Please put me out of my misery by telling me the secret to what I've done wrong.
Molto Verboso
1979 P150X, 1983 P200E, 1987 T5, 1996 PX200E, 2011 Yamaha Fazer 600 S2
Joined: 02 Aug 2015
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Location: Veria, Greece
Sun Nov 04, 2018 11:55 pm quote
Have you put in the kickstart gear?? Did it catch under the spring leaf?? I'd take out the clutch and see if the primary (cush drive) turns when you kick it. If yes, there's something wrong with the cluth. If not, you'll have to split the engine again...

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Enthusiast
Vespa Sprint
Joined: 28 Sep 2013
Posts: 89
Location: South Africa
Mon Nov 05, 2018 12:31 am quote
I can confirm I put the kickstart toothed gear back and the spring is pushing it against the Christmas tree gear stack, but what exactly is wrong with the clutch is my question?
Ossessionato
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Mon Nov 05, 2018 1:49 am quote
No idea what is currently wrong with the clutch. IF there was any separation of the clutch plates the kickstart action wouldn't transmit any force to the piston.

I know some Cosa style clutches hit the oil channel in the clutch cover. If you remove just the clutch cover and try kicking it, do you magically have piston movement?
Member
Joined: 26 Aug 2009
Posts: 6

Mon Nov 05, 2018 3:13 am quote
did you remember to put the woodruff key back in or perhaps it has sheared.
Hooked
68sprint,65super,64Allstate,55 Allstate
Joined: 20 Jul 2017
Posts: 241
Location: Central california
Mon Nov 05, 2018 7:16 am quote
no movement
SaFis has the right idea...... Is it possible to have the kick start gear on backwards??
If the woodruf key was sheared, or fell out, it most likely would still move the crank and piston due to that it is a tapered shaft. may not run but i think it would move if the clutch nut was tight. scott
Hooked
68sprint,65super,64Allstate,55 Allstate
Joined: 20 Jul 2017
Posts: 241
Location: Central california
Mon Nov 05, 2018 7:24 am quote
no movement
Not sure of the term your using "softkick" ???
if it feels like it wants to move or it is trying to move....check the keyways. scott
Banned
2:6
Joined: 11 Jan 2007
Posts: 7368
Location: San Francisco
Mon Nov 05, 2018 8:21 am quote
the kick start turns the layshaft, so right in the middle of things with clutch and crank on one side and the axle on the other.

put it in gear and press the kick starter slowly.
1. if the kick start lever moves but there is no movement of the rear wheel or the crank, then the issue is in the kick start mechanism.

2. If the rear wheel does move in the first test but the crank does not, then it has to be in the cushgear or clutch (more likely clutch).
Enthusiast
PX125E
Joined: 06 Oct 2018
Posts: 58
Location: Gravesend, Kent, UK
Mon Nov 05, 2018 3:26 pm quote
Hello. May I suggest you loosen the clutch cover so itís slack and try kicking it over. Something could be compressing the clutch internally.
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Smallframes!
Joined: 15 Apr 2015
Posts: 23
Location: Palm Beach, FL
Wed Nov 07, 2018 8:53 am quote
piston?
just throwing this out there . . .
did you forget the gudgeon / wrist pin?
Veni, Vidi, Posti
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Wed Nov 07, 2018 9:57 am quote
Re: no movement
Sjanuary wrote:
...
If the woodruf key was sheared, or fell out, it most likely would still move the crank and piston due to that it is a tapered shaft. may not run but i think it would move if the clutch nut was tight. scott
It's only the smallframe that has the clutch mounted on a taper and it has a rather small woodruff key as the tight taper does most of the work. This one is on a straight shaft, at the end of the crank, and a huge woodruff key to handle the additional load.


If the motor is still out of the bike, pull the clutch cover & watch to see what spins.
If not, put it in gear, rear wheel off the ground, spark plug out and you spin the fan wheel, what does the back wheel do?
Ossessionato
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Sat Nov 10, 2018 11:48 am quote
What happens when you put it in gear & roll it?
Enthusiast
Vespa Sprint
Joined: 28 Sep 2013
Posts: 89
Location: South Africa
Thu Jan 03, 2019 7:34 pm quote
Sorry for the late reply here on what was actually the problem that I resolved shortly after posting. It had to do with the LML Cush gear / Christmas tree gear which interlocks with the clutch being slightly different to that of a VESPA Cush gear and I had mixed these up when re-assembling the motor. Runs like a dream now
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