GY6 - Sudden Loss of Power, Bad smell, Running lean, Carb OK By kancur (Read 7,481 times)

[kancur]

Thanks, haven't noticed it but definitely looks suspicious on the picture, will check it tomorrow and post more detailed pictures.

EDIT: Here's another picture I took, definitely doesn't seem right to me! (Adding pictures somehow works only in quick reply mode for me)

[kancur]

And about the exhaust issue: Yep, new exhaust would be great. But I see prices of around 200 euros for this exhaust. And that's way too much. That's the value of the whole scooter right now. It has an 153qmi engine, does anyone know if mounting exhaust for 152qmi or other type will be a problem? 


Here's another picture I took. It looks just like when I bought it new from china.

[czmdiver]

I don't see anything that jumps out at me unusual
Clean up that Headpipe with a simple grinder. it looks darn near as bad as mine. that like 15%+ Exhort blocked off, that has nothing to do with your problem sh will just run a tad better.
On the Clips the Opening should be final at 6 or 12 o'Clock.....


thanks for the pics, they help and Good luck

[czmdiver]

[kancur]

Thank you, new head gasket came in today.

I need some help.
Where do the paper seals go?

Is it like this?
Paper seal which is on the right of the image - between engine and cylinder
Normal gasket which is on the left - between cylinder and head with valves
The small paper one, I don't know, maybe exhaust or intake?

EDIT: I checked a few youtube videos, and haven't found any use for the paper ones. I know where the normal gasket will go, but don't know where to use that paper seal on the right.

[czmdiver]

The thinner one you call Paper is the Cylinder Base gasket that goes in-between the Bottom of the Cylinder and Top of the Motor. 
Do you have more than one base gasket? 
The Cylinder must have a base gasket in place.
The Gasket on the Left is the Head gasket, It can be identified by the Metal crushable Fire Ring. That metal ring will crush once torqued to seal the Combustion Chamber.
The small gasket is a Intake gasket may or may not be used in your application. But you Do need eight the intake insulator or use that gasket.
Don use any silicone sealer on any of those gaskets, if you must use the Permatex Copper Coat spray. a light coat on each side of the base gasket is all thats needed.
Good luck

[cyborg]

Yep

[kancur]

Hi guys, so I put it all back together. And even did a test ride. Nothing changed. (Well I did nothing so I'm glad it's still the same )

So, to sum up my recent test:

• Don't forget that this problem  happened all of a sudden during a 10 minute highway ride at 90 kph (55mph). Suddenly it lost power and I was happy I was able to get off the highway doing about 40-50 kph (25-30mph). 
  
• Air filter is not clogged or anything
  
• Timing chain is correctly set
• Valve clearances are correct
• Valves and valve seats are sealed properly
• Compression seems good (But I don't have a tester, but valves don't leak, piston rings seem OK, and rotating the flywheel creates adequate resistance in compression stroke)
• Transmission has no problems (vario OK, belt OK, clutch OK). Wheel is easy to rotate by rotating the clutch.
• Sound when running is normal, nothing unusual
• I wouldn't have noticed that it is "weak" or has not enough power when on the main stand freewheeling.
• It has no power when driving. It drives like a lazy 50 cc. Lazy acceleration and max speed of 50kph (30mph) but otherwise runs nicely without any hiccups bogging or anything.
• Spark plug after the ride was black and sooty indicating rich condition (but maybe the soot got there when idling for a few seconds after the ride)
• I have problem with idle, I can't get a nice stable idle to work. It seems to work the best when the idle screw is all the way in - which is strange (In the past I used to have idle screw about 2 revolutions out for nice idle). And auto choke works OK.

Some ideas:

• Due to the sudden developing of the problem, I don't believe the problem lies in carburetor. I checked it and everything is in order. 
• Exhaust is something which is in bad condition (at least on the outside), but I don't know of a way of testing it. I don't have a spare. But can somehow suddenly clogged exhaust cause these symptoms? The flow of air from the exhaust seems normal as usual. (measured by hand )
• Piston, valves, timing chain are all checked and are OK.
• I noticed a bad bearing on the rocker arm on the side of the timing chain. There is a tiny tiny wobble. Could this cause such BIG reduction in power? I didn't change the rocker arm yet, as I don't have one. 
• Bad fuel, I can't imagine how this would cause such problem all of a sudden. I've never had a problem with fuel anyway. 

What in general can cause an instant and long lasting reduction in power but otherwise nice and smooth running?
I'm quite lost and can't figure out the cause. Theoretically, can for example a bad CDI cause this by mistiming spark somehow? Can it somehow "delay" the spark? That's the most recent part I changed about a month ago.

Thank you for your help!

[czmdiver]

Ok at this point this really point to your muffler assy coming apart internally like mine did and has shut the motor down.
In the early days of Catalytic converters on cars I had one go south and clog, the car starts and idled just fine but wouldn't get out of its own way once i hit the go peddle

[kancur]

Thank you, is there a way to test it? Can I run the scooter without a muffler for a while or is there some risk of damage?

[rks]

"Looking at the spark plug now, it seems quite ok to me. Isn't it?"

NO.....cyborg is right....way too rich. My scooter's plug, after 12,000 miles, is pictured below.



You won't convince me that your carburetor is fine, not with a plug looking like that. Maybe you have a nest full of dead mice in your air cleaner. 

[kancur]

New test: Today I unscrewed the exhaust from the engine so it wasn't tight and so it doesn't seal properly. It definitely run better! Therefore I assume the problem really lays in the exhaust. I will try to get a new one, but finding one for gy6 153qmi is a pain in the arse. Atleast here in Slovakia.

Thank you guys, your help is tremendous , will report as soon as I buy new exhaust.

EDIT: Seems like getting a new one which fits will be a real trouble. Is there something I can do right now? Like drilling holes in the muffler...  or something ? Thanks

[czmdiver]

Mar 15, 2018 9:08:34 GMT -6 kancur said:

New test: Today I unscrewed the exhaust from the engine so it wasn't tight and so it doesn't seal properly. It definitely run better! Therefore I assume the problem really lays in the exhaust. I will try to get a new one, but finding one for gy6 153qmi is a pain in the arse. Atleast here in Slovakia.

Thank you guys, your help is tremendous , will report as soon as I buy new exhaust.

EDIT: Seems like getting a new one which fits will be a real trouble. Is there something I can do right now? Like drilling holes in the muffler...  or something ? Thanks

Ya if you have some way to punch a hole clean thru the muffler would darn near do the trick, it is heavily baffled.
Take a od measurement of the headpipe and try to local source some type of muffler, from a power equipment small tractor lawn mower type business, cut the headpipe off wear it attaches to you muffler and slip something else on..
I see from the photo the headpipe is non detachable. surf some sights and you can find just the headpipe then there will be more options to attach a muffler from there..

Slovakia
Both of my grandparents were born in Slovakia, came to US thru Ellis island,and of course my mother is very strong in eastern european food taught to her from her mother.. Fine people...

[kancur]

Thank you!

Slovakia
Wow, that is cool coincidence !

[cyborg]

Well diver beat me to the punch again,,,the problem lies in the exhaust,,,toss that thing and pony up for a new one,,,