Modern Vespa

Went out on a run yesterday about 120 miles on way back about 10 miles from home I started to loose power bike wouldn't go over 50 miles per hr and when at traffic lights I was lucky to get 10mph someone told me if reed valve is faulty I would loose power any help would be good . I've checked plugs that are ok only just changed oil and filter

you don't have a reed valve in the intake manifold.

you probably have a variation belt shredding. open up the CVT and inspect.

Belts ok just changed it two days ago checked it this morning all was fine. Im on about breather reed valve going to air filter

that won't resut in lose of power need to look somewhere else valves or pistonrings

Yes, the reed valve just lets the crankcase breathe. If it fails, there will be a *lot* of oil in your air filter, but it wouldn't cause noticeable power loss.

Things that can cause this kind of radical power loss:
1) burnt valves - if your valves are burnt, it usually shows up gradually, sometimes backfires a lot, and is hard to start. Maybe one is stuck open, but when that happens, it will punch a hole in the piston and make an awful clattering, then quit completely after a few seconds of running.

2) clogged fuel system in some way- let's hope it's a fuel problem, then maybe the engine doesn't need a rebuild. Usually fuel problems begin with sputtering and coughing and lack of throttle response.

3) completely worn out, or maybe damaged piston/cylinder. Similar to burnt valves, but it will fill your airbox with oil as all the blow-by gasses carry your new oil into the airbox through the one-way reed valve..

Get a compression check to determine the integrity of the cylinder/valves. If the compression is OK, then look at the fuel system. You may just need your injector cleaned.

I'm hoping it's fuel I started bike last night and it rev up over 7 thousand Rev seemed a bit sluggish . Bike did dump most of oil so reed valve not doing job why do Piaggio sell a bike knowing it looses oil If it was one of us we would end up in court

What about your Air Filter?
Is it clogged where the engine can't breathe?

Keith,
Marietta, GA

I fitted a long flex pipe from crankcase Towards number plate with a air filter on it it come out under number plate but still lost oil. I've just ordered a pcv valve so hopefully this will sort oil problem out.if not back to drawing board . Piaggio should recall all bikes with this problem 😟 but it won't happen

Is the oil coming out of your breather pipe? Did you route it as high as possible to give any oil a chance to run back? Is the oil level in the engine too high or not checked exactly as the manual says? If you still have a problem after that you will need to check the engine with a compression tester in case it has piston or ring problems.

Cheers roadster. Anyone know wot compression is on these

I heard 170psi. It could be wrong, but i dont think so. The number is pretty consistent with what i've heard for similar scooter engines. So at the very least its in the ballpark.

Yes 170 psi would be about right but you may need to put a few drop of oil in to get this if the engine is cold. Also bear in mind that the engine has an automatic decompression device so it needs to be spinning fast enough to overcome that.

if you want to know if the rings are gone look with a camera use the sprakplug hole if the are broken then they have demaged the piston usely

and scratches on the lining is also an indicator

a usb endoscope they cost about 5 bucks on Aliexpress it can connect to you cellphone or laptop

Thanks all for your help bike seems to be running ok Now ish lol got engine light on but bikes runs ok I've turned light off but comes back lamda sensor so got to order a new one

Rebuilt engine but compression is only 152 psi is this ok

Depends on how you are measuring it. Are you spinning the engine fast enough to overcome the decompressor? Does it change much if you put a couple of squirts of oil in first?