Down on power, feels tired & tops out at 40mph...

[dantastic]

Hi All,

Im new to the forum but have been a Vespa owner/rider for 8 years. My little px125 gets me everywhere and has been my main mode of transport for 4 years now.

My issue is above really, about 3 years ago i blew a hole in the piston which was welded back up and ran ok ever since but is very down on power. I decided this week to try and get it sorted and back to its best.

A couple of things i would like help on, will the new rings i have bought need running in, of so for how many miles? Also can anybody think of any other ways of regenerating a bit of life into it?

Thanks

Dan.

[Robjack]

Hi Dan, welcome.

You will most likely need to run it in with new rings. Treat it like it's made of eggshells for the first 50 miles then gradually increase things to no more than 3/4 throttle for the next couple of hundred. The things to avoid are labouring the engine up hills or into the wind, better to knock it down a gear and use higher revs than that. Also don't sit at the same speed/revs for long periods, variation is what it wants.

Don't put extra oil in the petrol for running in, there's enough with the autolube. Or if you don't have autolube, just use the normal amount you would use.

The more people you ask about running in, the more ways you will hear, everyone does it differently. The thing is when you feel comfortable opening it up, that's when it's run in (within reason). When you do open it up, keep your fingers over the clutch lever!

As for giving it a bit more power, the only real option is a kit. Read through the threads below, there's plenty covering it.

[dantastic]

Hi,

That was my initial plan but after having spoken to my local dealer (East mids scooter centre) who said, "no just put them on and crack on" my judgment was clouded. I think ill run them in.

Ill see how the rings go, would a new piston be worthwhile or not do you think?

[Robjack]

I'm not going to argue with the experts because I'm not one. My thinking was based on the belief that the main thing you are doing when you run an engine in is honing the rings to the cylinder. So whether it's really necessary or not, personally I would feel more comfortable running it in.

If your piston crown has been repaired in the past, I would definitely replace with a new one. It's the ideal time to do it.

[dantastic]

I get the feeling that this guy is certainly not an expert!

Is there any where you know of that sells used/cheap parts such as pistons?

[Robjack]

Scooterwarehouse, who is a member of this forum, is a well respected dealer (based in the Northwest) who might be able to help. If he doesn't see this thread I would ring him and discuss what you have said here with him. He's much more of an expert than I am.

I will send you a PM with his telephone number.

[dantastic]

Thank you ever so much for your help!

[Robjack]

New PM sent, with the right number this time.

[dantastic]

Cheers

[sbwnik]

Failing that, I can't speak highly enough of Welsh Scooter Parts, good cheap service.

Welding a piston though? I'm impressed... unless you did it yourself, it would probably have been cheaper to replace the piston than to get it welded. Did you find out what caused it to hole? If not, be ready for it doing it again (which could be related to the drop in power too)

Are you running an aftermarket exhaust? This is the usual cause of problems like this - the jetting will be too lean.

[dantastic]

Standard exhaust, to be fair it hasnt happened again in the 3 years+ ive been riding it since. Got my dad to weld it up so didnt cost a bean. Ive been chatting to a bloke off Ebay, small wheels and they will do a full piston kit for £35. That a fair ish price?

[bryno]

Pistons usually around £40, so fair enough, but personally i'd not skimp on that and be sure to get a decent quality brand not a cheap aftermarket one.

Also, be sure you get exactly the right piston for the size of barrel, really you need to get the barrel measured properly, if your piston is slightly under or over, you will have issues going forward.

You shoud get the barrel honed before you fot the piston and run it in properly, it's more important to do that with a new piston than when you just replace rings

[sbwnik]

£35?

Got a link, that's suspiciously cheap?

[dantastic]

I dont have a link but theres an ebay shop - On small wheels. Heres his msg to me on Ebay:


Dear dan_tigershagging,

Hi Dan,
standard piston for a px125 is £35, thats a full kit, piston, rings, gugeon pin, circlips, not sure at this point if we have one in stock, i will check but if not i can have one by tuesday next week.
hope this is ok.
many thanks dave @ on small wheels

- onsmallwheels

After having fitted new rings and ran them in, i have noticed no difference. Still wont do more than 45mph. Anybody got any suggestions?

[scooterwarehouse]

You don't state the mileage that your PX has done.If it has done a big mileage it may be a worn out engine that is ready for a strip and overhaul.If it is an old exhaust it might be choked and ready for replacing.Check your gear oil for any signs of petrol content.

[dantastic]

The exhaust is 3 years old but this problem has been the same since i blew the hole in the piston. Its done about 10k and is a 2000 W. I might buy a new piston from that chap on ebay and see if that works. The engine cases do have a very slight leak but never enough to leave drops on the floor but the engine cases are caked in oily gritty nastyness.

[pacelineaddict]

If the problem has existed since blowing the piston, I think this is the area you need to investigate further.

Defo go for a replacement piston, then check all areas in close proximity for damage (relating to the initial blow out), as there's a chance there'll be some form of damage/distortion/fatigue, causing the loss of power - what's the compression like... you checked it?