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@l4nff avatar
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Hooked
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
 
Hooked
@l4nff avatar
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
UTC quote
Is this evidence of blow back and worn rings? Compression 105 and with oil added to cylinder 125.
Forum member supplied image with no explanatory text
Forum member supplied image with no explanatory text
Forum member supplied image with no explanatory text
Forum member supplied image with no explanatory text
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Molto Verboso
px200
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Location: london
 
Molto Verboso
px200
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Location: london
UTC quote
I may be going off at a tangent, but is the top ring upside down.
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Hooked
1952 Allstate 1955 Allstate 1958 lambretta 1965 Allstate 1968 sprint
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Location: Central california
 
Hooked
1952 Allstate 1955 Allstate 1958 lambretta 1965 Allstate 1968 sprint
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Posts: 495
Location: Central california
UTC quote
Worn rings
I think the top ring is on upside down...also don't forget to take the spring off the end of the crank. It looks like it is the main seal spring.
Looks like there could be excessive blow by, but we don't know how many miles are on the motor. Plus if the ring is on upside down that could be part of the problem. Scott
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Hooked
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
 
Hooked
@l4nff avatar
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
UTC quote
Aha, guilty. I changed the crank shaft seals and bearings 30 miles ago and all seemed well. However horrendous trying to start from warm and then all of a sudden it started running like a dog and my investigations showed a bulging fly side seal. Hence this strip down. So it was silly me who put the rings back on and clearly upside down. I have been told at the shop that low compression can mean hard warm starting. I have bought new rings which I will take care in orientation. I believe the piston and head to be original from 1972 but have no idea of mileage as it didn't come with a Speedo. Got a new cruciform and gaskets. Anything else I should check change whilst out?
@safis avatar
UTC

Ossessionato
1979 P150X, 1983 P200E, 1987 PK125XL Elestart, 1988 T5, 1995 PX200E, 2011 Yamaha Fazer 600 S2
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Ossessionato
@safis avatar
1979 P150X, 1983 P200E, 1987 PK125XL Elestart, 1988 T5, 1995 PX200E, 2011 Yamaha Fazer 600 S2
Joined: UTC
Posts: 4113
Location: Veria, Greece
UTC quote
Rings are probably fine this way. If you had them upside down, the cylinder wouldn't fit and the rings would have probably cracked. It's an old, 2 port engine. The locating pins were at the bottom of the groove. You should decarbonize and clean the grooves before installing new rings...

SIP's kit shows the same and on your photo it seems to be the case...
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Forum member supplied image with no explanatory text
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Molto Verboso
px200
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Location: london
 
Molto Verboso
px200
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UTC quote
Yes the top picture shows the locating pin at the top of the groove and the cutouts at the bottom.

Good luck with this.

Grumpy
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3:5
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UTC quote
Grumpy wrote:
Yes the top picture shows the locating pin at the top of the groove and the cutouts at the bottom.

Good luck with this.

Grumpy
That is not a pin in the top picture, it's carbon build up. The rings are on the correct way.
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Member
99 PX125e
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Location: Monmouthshire, UK
 
Member
99 PX125e
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Location: Monmouthshire, UK
UTC quote
Just tagging-on to this thread...

Does it matter which way (up or down), the rings are installed? I've just fitted a new Polini 166 (cast) kit on my 1999 PX 125 and must confess, didn't check ring orientation. Haven't started the engine yet, but the barrel slipped over the piston/rings without issue and everything turns freely and smoothly by hand.

I was just about to whip the head and barrel off and check/change, as required.

Confused.com.
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Molto Verboso
px200
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Molto Verboso
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UTC quote
My error

It looks just like the pin on mine.


Grumpy
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Hooked
piaggio hexagon
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Location: lincolnshire uk
 
Hooked
piaggio hexagon
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UTC quote
RiffRaffRetro wrote:
Just tagging-on to this thread...

Does it matter which way (up or down), the rings are installed? I've just fitted a new Polini 166 (cast) kit on my 1999 PX 125 and must confess, didn't check ring orientation. Haven't started the engine yet, but the barrel slipped over the piston/rings without issue and everything turns freely and smoothly by hand.

I was just about to whip the head and barrel off and check/change, as required.

Confused.com.
Hi, as can be seen in the photo`s in this post, the piston ring has a semi-circular cut out in the ring ends. When fitting the rings this locates around a peg in the piston ring groove. It`s purpose is to locate the ring such that the ends cannot spring into the cylinder ports.
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Member
99 PX125e
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Member
99 PX125e
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UTC quote
Got it... thanks again for the guidance.

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@l4nff avatar
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Hooked
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
 
Hooked
@l4nff avatar
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
UTC quote
Ok new seals, bearings, condenser, gaskets, plug, rings, cables and kick start rubber. Cleaned the piston, honed the barrel with a borrowed honing too. Compression didnt change, still 105 psi, this may change i think after running in. Started up and the tick over was awesome, it was perfect, revving up was spot on.started up first kick when warm which it never did . Really pleased with myself, just hope it stays that way as the miles add up. New cables going in tomoz and a bit more 2 stroke oil. I have really enjoyed what I have done and I have fingers crossed that all stays as it should. I'll post a vid tomoz of it finished.
@moto64 avatar
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Molto Verboso
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
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Location: S.Salem, NY
 
Molto Verboso
@moto64 avatar
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
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UTC quote
Good for you !
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Hooked
1952 Allstate 1955 Allstate 1958 lambretta 1965 Allstate 1968 sprint
Joined: UTC
Posts: 495
Location: Central california
 
Hooked
1952 Allstate 1955 Allstate 1958 lambretta 1965 Allstate 1968 sprint
Joined: UTC
Posts: 495
Location: Central california
UTC quote
Worn rings
Good job...have a great time riding your scooter. Next time I'm in the neighborhood will have to go riding. LOL scott from California
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@l4nff avatar
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Hooked
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
 
Hooked
@l4nff avatar
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
UTC quote
Well tried to upload a vid but to no avail. Running well and now starts from warm on the first kick. Going to wait for a better day and then take it out on a 10 mile low rev run in. Fingers crossed all stays well.
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@l4nff avatar
UTC

Hooked
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
 
Hooked
@l4nff avatar
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
UTC quote
Well im happy to say its has travelled well. I set of in 7 degrees of coldness (my usual limit is 10) in the dark. I completed 15 miles of very smooth running the engine feels super smooth and runs and ticks over lovely. I didnt over rev it and pootled along with a large smile under my balaclava. First gear is a bit far away, but think that will adjust up. Again it started from warm on the first kick with no throttle. All seems to good to be true but just maybe i have cracked it.
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Member
99 PX125e
Joined: UTC
Posts: 45
Location: Monmouthshire, UK
 
Member
99 PX125e
Joined: UTC
Posts: 45
Location: Monmouthshire, UK
UTC quote
Good to hear you've got the hard graft out of the way and enjoyed a successful first outing.

I'm in a similar position, in as much as I bought what I thought was a nice 99 PX, requiring minimal tidying-up, only to have to embark on a complete strip and rebuild (Jasil crank, Polini 166 cylinder kit, bearings, seals, o-rings, shock absorbers, tubeless rims and tyres, pads/shoes, cables, wiring - the list goes on), as it just wouldn't run smoothly - over-revving between gear changes, lumpy, under-powered and handled like a duck on ice!

I'm 98% there now (started her up yesterday... sounded promising), only the Missus got starry-eyed half way through the work and bought herself a 2014 PX that itself requires sorting!

Wish I'd stuck with the K1200 RS now!

Anyway, keep at it and hopefully, once the sunshine returns, we'll all get a chance to get some decent miles in.

Love the Lotus too, mine's a 2018 GT86.

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@l4nff avatar
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Hooked
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
 
Hooked
@l4nff avatar
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
UTC quote
I have friends close by with lambrettas and we are all in some form of repair/upkeep. Its part of owning a two stroke I suppose.

I swapped the lotus for a pram a few years ago and put the reg on a Nissan leaf, but that picture just wouldn't be the same.

GT 86, is that a Toyota?
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Member
99 PX125e
Joined: UTC
Posts: 45
Location: Monmouthshire, UK
 
Member
99 PX125e
Joined: UTC
Posts: 45
Location: Monmouthshire, UK
UTC quote
Yup, that's the one!

I guess the drama of constant maintenance and upkeep is the price we pay for going with old-school 2T power... wish I didn't have two to maintain, however!

Need to get out and ride now... roll on Summer!
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