PX 125 Bogging down problem

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paul d
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Posts: 303
Joined: Thu Jun 30, 2011 10:00 am
Main scooter: T5 172 Tv 240
Location: Galway Ireland
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Sun Nov 15, 2020 4:03 am

I meant to say if it creeps forward when in gear!

parky
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Joined: Tue Jan 26, 2010 10:41 pm
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Sun Nov 29, 2020 4:16 pm

Thanks for the advice on the gear change, adjustment has made a big improvement. Also I have now completed a couple of plug chops and the colour of the plug does appear to be a bit on the lean side. I have adjusted the mixture screw a bit further out but still seems lean. When I adjust the screw too far out then the scoot runs terrible but it is now running fine but still a bit lean is there something else I can do to get the colour of the plug to a nice shade of brown?

paul d
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Posts: 303
Joined: Thu Jun 30, 2011 10:00 am
Main scooter: T5 172 Tv 240
Location: Galway Ireland
Contact:

Tue Dec 01, 2020 1:00 am

Have you changed anything on the scooter like a non standard exhaust? I can't remember what the main jet is for a px125. If your scooter is standard then the standard main will be perfect. If you've changed the exhaust then the main jet has to be raised. Is there any oil leaking from the head? You can check by lying on the ground and looking under the cylinder cowling for an oil weep or just take off the cylinder cowl and check. Any air leak will lean off your engine. I'm sure it's something simple.

parky
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Joined: Tue Jan 26, 2010 10:41 pm
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Thu Dec 03, 2020 5:28 pm

Thanks for advice , gear change now much better. Plug chops now completed but seems to be running very lean. Have taken the mixture screw out a few turns at a time as far as I dare but still seems lean.
Is there anything else I should be doing to get it running richer?

paul d
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Posts: 303
Joined: Thu Jun 30, 2011 10:00 am
Main scooter: T5 172 Tv 240
Location: Galway Ireland
Contact:

Thu Dec 03, 2020 9:19 pm

First thing I'd do is check the main jet. Carb lid off, air filter off, it's under the biggest brass screw as seen when you look down on the carb. It's a push fit into a brass tube with alot of holes. lt'll become obvious when you undo the largest screw. I'd look up the main jet size for a standard px125. Maybe it's 96 or 98? I can't remember. If the jet fitted is correct then your lean looking plug is most likely caused by an air leak somewhere. Oil leaks might point you in the right direction. Oil coming out under the fan or head or under the carb box means there's an air leak in one of those places and you'll need to fit either a new gasket or seal to fix the problem. Where the fuel hose enters the carb there's a filter. Undo the single small nut holding the cap to check. If dirty, clean it. Dirt in the petrol tank can cause lean running too. with a torch check it out. Any crud inside should be removed. Do an oil change (sae30). If the oil has a strong smell of petrol or there's only a small amount of it left then most lightly your clutchside oil seal needs to be replaced and it's causing you to run lean. On the top of the clutch cover on the wheel side of the engine there's a breather. If the engine runs different when this breather is taped up or is removed and replaced with a bolt then the seal needs to be replaced. That seal is the biggest job but easily do able if you have to. Best of luck with it!

parky
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Posts: 39
Joined: Tue Jan 26, 2010 10:41 pm
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Fri Dec 18, 2020 3:13 pm

Thanks for all the advice scoot is now running ok. I have tried a couple of plug chops but it does seem to running a bit on the lean side. I have tried adjusting the mixture screw but without much success is there anything else I can do to try and get that elusive nice brown colour on the plug?

paul d
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Posts: 303
Joined: Thu Jun 30, 2011 10:00 am
Main scooter: T5 172 Tv 240
Location: Galway Ireland
Contact:

Sun Dec 20, 2020 12:52 am

Correct way is to follow everything I've said previously which will solve the cause. If you've no time just put in a bigger main jet. Go up one or two from whatever number is fitted already. If you don't have a bigger jet, run the bike with a dash of choke all the time. A small bit, don't push the choke fully in. It'll kill the plug eventually so always carry a spare but for sure it'll run richer! Nothing mentioned in this post will fix the cause but will allow the engine to carry on fine with whatever the underlying cause is. If the plug has any hint of brown, isn't white and the bike is standard, I'd just live with it..........and keep a hand on the clutch lever!

parky
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Posts: 39
Joined: Tue Jan 26, 2010 10:41 pm
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Mon Dec 21, 2020 3:23 pm

Thanks for all the advice, will get Christmas over and then get stuck into all the checks mentioned above. cheers,

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