gino01
2nd Class Ticket
Posts: 17 
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Post by gino01 on Feb 19, 2017 13:53:52 GMT
Hi
need a bit of advice on my 85 px125,it runs well,pulls through the gears fine but runs out of puff at 45mph
at top end and only there you can here it pinking
I have done a compression test and it,s at 100psi done this several times and always same.done mixture new lead and plug,cleaned carb and all fine,although I ain't sure what size jets should be in the carb?it feels like it wants to give more but holds back
thanks in advance
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Post by pxguru on Feb 19, 2017 16:32:12 GMT
It should be quite a bit faster than that. 100psi compression is not great but should still go faster. If it starts good, rides fine and goes otherwise well, then there is not much wrong.
Have you ever tried a different exhaust pipe? It could easily be partially blocked, which would do exactly this, if it is quite an old one.
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gino01
2nd Class Ticket
Posts: 17
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Post by gino01 on Feb 19, 2017 17:24:06 GMT
Hi
Exhaust is standard but new,just the pinking at top end is causing concern?
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Post by bryno on Feb 19, 2017 18:20:57 GMT
Has it run better than this in the past?
Have you done any work on the engine recently?
Pinking probably means your timing is a bit out, but always helpful to take a step back to when it ran ok and work from there
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gino01
2nd Class Ticket
Posts: 17
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Post by gino01 on Feb 19, 2017 19:36:00 GMT
Always run like this since I got it,newbie mistake I just ran it up and down the road and it was fine,speedo in kph didn't,t help ha ha
I will check timing and take it from there.piston head etc all clean and fine.will check stator and see if it has moved a tad
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Post by pxguru on Feb 20, 2017 7:03:35 GMT
Have you ever had it running on a different exhaust? Just because it is new doesn't mean its any good.
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Post by bryno on Feb 20, 2017 11:04:31 GMT
I'd certainly do all the basic checks first, timing, plug gap, air filter and check if it has the correct jets fitted for the spec (see scooterhelp.com for the spec)
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gino01
2nd Class Ticket
Posts: 17
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Post by gino01 on Feb 20, 2017 20:32:21 GMT
Thanks for the help,exhaust I have swapped for one off my other px and still same.i,m going to take the jets off and swap them round and see if that makes a difference,after timing check as that's the last two things I can think of?
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Post by pxguru on Feb 21, 2017 6:41:04 GMT
Still something wrong with it for sure, a standard 125 should always manage 55mph on the speedo and maybe even 65mph on the speedo........on a really good day.
Have you taken the cylinder head off and cleaned off all the carbon? Sometimes there is quite a build up in the exhaust port. Take a picture of the top of the piston (before and after cleaning) and we can see how bad the pinking is and if it is the jetting.
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gino01
2nd Class Ticket
Posts: 17
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Post by gino01 on Mar 12, 2017 20:13:46 GMT
Well thought before I got the tools out today I would make most of the bit of sunshine we get and take the scoot for a blast.
Two miles up the road got backfire and power loss,engine still running but only 30 max and rough but no backfire,until I turned my lights off and then got 35!!!
However if I indicate or put an electrical load on it just pops and backfires and slows down even more.problem is it got dark just as I got home so would I be right in thinking stator fault or that it has moved at least,scoot still running on tick over fine no issues until under load
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Post by pxguru on Mar 13, 2017 4:30:40 GMT
I think you are getting close to your original loss of speed problem now.
I would have the flywheel off, have a look then stab around with a multi-meter. As far as I know the spark power and lights power are reasonably separate but if there is some short circuit going on at the stator, then they might not be so separate anymore.
The only time I ever see proper backfiring is when the woodruff key has sheared and then the timing is way out(on a tuned high rpm engine the woodruff key is a service item!).
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gino01
2nd Class Ticket
Posts: 17
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Post by gino01 on Apr 11, 2017 13:49:20 GMT
Quick thank you for the help guys,stripped stator and found every wire bare corroded and falling to bits,early type stator,put a new one on and presto"'pinking gone runs well.
Better top end but still going to remove head and have a look,reckon it will need decoking.
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Post by mijapxman on Apr 12, 2017 12:36:16 GMT
Had a PX in to fix early 1990s, kept on shearing woodruff keys, the guy was tearing his ( short hair) out!
A quick lap with grinding paste on flywheel boss/crank cured it. Turns out he was using a new ( to him)
flywheel and it was a bad match.
Ride safe😀
Jim 😉
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gino01
2nd Class Ticket
Posts: 17
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Post by gino01 on Apr 12, 2017 13:27:41 GMT
Did wonder if they would be a perfect fit,at Scarborough at weekend so should be able to pick one up there.for diagnostic purposes it has eliminated the pinking etc
Took head off yesterday and piston was a cookie dough colour as well as the head and plug so I,m quiet happy with that?slight play in piston left to right but I,m guessing there should be due the rings?no scoring or coking up though
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