Peugeot with I.E. dies on downhill and at traffic light

[GrumpyUnk]

Two things can cause premature ring wear, off the top of my head. Running too hot can cause the rings to lose their tension and not push outward against the cylinder wall. Both power reduction and oil consumption increase would be symptoms. Possibly hard starting due to lowered compression. The second would be air cleaner failure allowing instrusion of dust & dirt via the intake. That can cause the rings to wear prematurely. Third would be rings that have not had their end-gap checked during installation. When the engine gets to normal temperature, the rings expand and close their end gap. If not checked and adjusted as needed, they can close the gap to zero and cause all sorts of problems. Finally, running for miles at WOT and at top speed without any breaks can cause wear due to possible minimal oil and lack of vacuum to pull oil up onto the upper cylinder wall. More or less. It does not hurt to close the throttle once in a while to produce engine vacuum and give the rings a few seconds of suction more than normal(close to none with WOT) to pull somee oil up onto the rings & cylinder wall.
The Motul is considered one of the top brands of motor oil. I doubt they produce anything that would be bad for a 139QMB.
You reference 'got this fault'... What fault is that exactly as I see no mention of it. Does the engine use oil excessively? Lose compression? Produce blue smoke when running?
What fault do you reference?
tom

[GrumpyUnk]

Can you post some pictures of the valves, especially the seating area? A pic of the seats in the head would also be useful for visual analysis.
If you are keeping the valves, do you plan on lapping them to clean the valves and seats? Or replace new valves? New head? The valve stem seals are ok if they are still a bit flexible and are tight on the stem.
tom

[jackrides]

What is your valve clearance? What are the specs? How much pull do you feel on the gauge strip when you pull it thru the valve space?

[imenom]

so i fixed my scooter, i changed piston rings, i had good compression and i was still getting missfires/ i knew i was getting bad spark but did not know how to test it, so changed steam valve rubbers, and still the same.

i cleaned my fuel tank just to know it was super clean and i did not have problem with fuel, since i moved every component i realised i can move throttle sensor to its original position because there was marking from factory on bottom of throttle body so i did, but still the same

so i tested a spark with multimeter on ampere mode, i placed spark plug on engine housing and and i used multimeter probes to touch engine housing and second one was on plus of ignition coil and i was observing how strong is a spark on spark plug and i realised there was something wrong with ignition coil. it gets plus signal from computer but minus was weak, so i used sander and sanded a bit of paint where i screw ignition coil to structure of scooter and it worked

in meantime i had 3 bad NGK spark plugs and fourth one i bought was denso u22fs, i drove scooter for 600km and is working fine, i am looking to sell it because there is no one in my city that can fix it beside me so i have had enough of this scooter (was trying to fix it for 1 and a half year)

edit: i just saw this comments

Can you post some pictures of the valves, especially the seating area? A pic of the seats in the head would also be useful for visual analysis.

If you are keeping the valves, do you plan on lapping them to clean the valves and seats? Or replace new valves? New head? The valve stem seals are ok if they are still a bit flexible and are tight on the stem.

tom

as i mentioned above i replaced old steam valves/rubber with new ones (after replacing i have seen i needed to lubricate them), after replacing them valves would move much harder, so i guess old ones were worn out, i cleaned valve seats with scotch brush until both valve seat on head and valve itself were shiny, sadly i do not have any photos/videos, i have recorded myself changing valve seats (disassembly of cylinder head) but when i realized i did not fix my problem with changing valve seats i deleted that video. This is old one where i recorded how to disassemlbe whole scooter (https://www.youtube.com/watch?v=ugVHFHupIpo&t=1240s) here you can see how cylinder head looks like 

What is your valve clearance? What are the specs? How much pull do you feel on the gauge strip when you pull it thru the valve space?

i called authorized service to help me fix this scooter and they told me that i should put valve clearence to about 0.20-0.30 mm because this engine has only one spring and is very weak so i did and engine is running perfectly fine, i did not try 0.1mm because i did not want to touch something that is already working, if seats get clogged up i will put 0.15mm valve gap next time, pull on gauge strip was pretty hard


drive.google.com/file/d/18Pgk46IH8vBQe54chMEcLzxJHdbGNg08/view?usp=sharing
here is service manual for 139QMB-J , i hope this will help someone

[snaker]

Glad the problem is solved.
I picked up on something that may help others.
I browsed the manual shown and:
Page 39 shows cam sprocket timing.
Looks like they don't use the 3 point visual marks like some do

They have 2 hashmarks that form a line offset from the camshaft center.
The diagram shows that the hashmarks should be ABOVE shaft center for proper timing

Looks to me like one position (the right one) has the marks at case edge level and 180 degrees out would have the hash marks below the case edge level

[imenom]

this is how i did set up timing on this scooter, this photo scan be seen on page 29 in user manual