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Post by swampthing on Jul 11, 2017 13:09:10 GMT -5
Hey everyone, I'm seeking some advice on a scooter im working on, a friend of mine recently purchased not running. Hey I work at a shop right? great... Anyways I'm a small engine and equipment tech for a John Deere dealer but ive never dabbled in powersports equipment so I knew nothing about these until now. Its manufactured by ZHEJTANG TATZHOU WANGYE Power Co. What I guess is the model number printed on the rear cowling over the tire is MC-12-150. The Engine seems to be a GY6 150cc engine. He purchased it for little or nothing which still may not have been a great deal because I feel like this is in need of more repair than he thought. According to him the scooter has been sitting unused for 2-3 years! He was under the impression that maybe it just needed a simple carb cleaning like many small engines that were shoved aside to collect dust. It reeked of old gas of course, I also noticed the engine crankcase was full of a very runny gas oil mix. so first things first I cleaned the entire fuel system including disassembling and hot tanking the carb. Put it back together with fresh fuel, spark plug, oil, and I cleaned the air filter which was heavily saturated with oil and it ran great when throttled but would not idle and hard to start unless throttled. When it began to heat up it would also emit a large amount of blue smoke from the muffler. So before fine tuning it I decided to make a small test drive to see if the oil would clear out thinking maybe because of the way overfilled crankcase that oil had made its way into the exhaust. It never would clear out and gets worse as you ride it. I check the dipstick and see it is def consuming engine oil. I removed the muffler and tipped it on end and did not getting oil pouring out. My friend assures me its probably trapped in there and will burn out so he has me replace the carb to fix the idle which did nothing. I researched on the internet and have seen that adjusting the valves can correct no idle/hard start conditions if they are too tight not allowing valves to close which they had no valve lash at all, and that helped it idle a little better but it still will cut off. I adjusted both around .0003"-.0004". Despite what he says and does not know, I'm thinking the engine has been damaged somehow and possibly the piston rings/valve seals are shot. I compression tested the engine and got around 120-130 psi. I also performed a leakdown test and it passed showing low cylinder leakage. Everything seems ok to my knowledge but I'm no scooter man, so am I missing something here or do I possibly have internal damage based off what I've told you? I appreciate everyone's input and effort to help me, thank you.
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Post by tortoise on Jul 11, 2017 14:36:45 GMT -5
MC-12-150 . . possibly the piston rings/valve seals are shot Speculating a GY6-B engine . . cylinder stud spacing is different from typical GY6 engine.
Concur there may be a piston ring blow-by issue.
Might also verify that a deficient vacuum fuel petcock diaphragm is not allowing fuel to bypass the carb.
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Post by dollartwentyfive on Jul 11, 2017 17:48:32 GMT -5
worn valve guides will cause the engine to burn oil as will defective piston rings.
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Post by toddmaples on Jul 11, 2017 19:26:56 GMT -5
MC-12-150 . . possibly the piston rings/valve seals are shot Speculating a GY6-B engine . . cylinder stud spacing is different from typical GY6 engine.
Concur there may be a piston ring blow-by issue.
Might also verify that a deficient vacuum fuel petcock diaphragm is not allowing fuel to bypass the carb.
May be overfilled if checking oil on sidestand or centerstand. I always check mine as the bike is ridden, both tires on ground, straight vertical. Did you do the leakcheck with the engine hot? Worn valve seats can seal at colder temps and open up at higher temps, allowng oil from the top end into cylinder... |
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Post by rockynv on Jul 12, 2017 9:07:54 GMT -5
Before you go too crazy ensure that the purge tube is empty and the sponge where it vents into the air cleaner housing is clean and not plugged solid. A GY6 can blow a lot of oil into the purge tube if the valves are even slightly tight and on an engine that may have been abused the adjustment that was recently done could have settled in and the gaps closed up already so you may need to check them again. Valve gaps can require a monthly adjustment on a GY6 if you ride it daily. If the purge tube from the head has been capped or plugged so its no longer venting this could also increase oil consumption due to pressure build up in the crank case.
On some bikes where excess oil is being blown through the purge tube to be drawn into the carb some will take a metal cased fuel filter and use it to make a high mounted catch can attached to the frame of the bike so the oil will drip back into the head when the engine is turned off rather than get ingested through the carb.
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New Rider
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Post by 99kinetic on Jul 12, 2017 11:21:56 GMT -5
Hello, I'm seeking help myself.
I can't seem to locate the engine number on My 1999 kinetic.
Any assistance will be appreciated.
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New Rider
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Post by swampthing on Jul 12, 2017 13:00:08 GMT -5
rockynv thank you I'm definitely wanting to rule out any exterior problems before assuming its engine, as far as the crankcase breather goes I see what youre taking about. Off the valve cover is a hose that leads to the airbox which is where I originally found a large amount of oil buildup. However, there is no sponge inside the airbox, instead there is a chrome metal tube bolted to the head and it expells gases through a port in the valve cover and out an external vent with a sponge inside. It all seems to be unobstructed except for the passage within the cylinder head. I ran a piece of wire as far as I could through this passage and then tried to blow air though it thinking I could hear this air from the crankcase but it literally almost completely holds air, I can hear a faint whistle from inside but that's it, shouldn't there be more of a flow through there that should allow it to breathe better? Is it possibly plugged somewhere inside the crankcase?
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Post by toddmaples on Jul 12, 2017 15:29:12 GMT -5
rockynv thank you I'm definitely wanting to rule out any exterior problems before assuming its engine, as far as the crankcase breather goes I see what youre taking about. Off the valve cover is a hose that leads to the airbox which is where I originally found a large amount of oil buildup. However, there is no sponge inside the airbox, instead there is a chrome metal tube bolted to the head and it expells gases through a port in the valve cover and out an external vent with a sponge inside. It all seems to be unobstructed except for the passage within the cylinder head. I ran a piece of wire as far as I could through this passage and then tried to blow air though it thinking I could hear this air from the crankcase but it literally almost completely holds air, I can hear a faint whistle from inside but that's it, shouldn't there be more of a flow through there that should allow it to breathe better? Is it possibly plugged somewhere inside the crankcase? If youre crankcase isnt venting properly it will be very difficult to get it to take oil with a funnel. Put funnel in filler neck tightly, and pour about 1/4 quart into funnel, if it doesnt immediatly drain into crankcase, then you have a venting issue... Easiest way to tell i've found so far... If it doesnt take oil immediatly, remove hose from top of valve cover and see if that helps, if it does then the vent problem is in the hose. Note this procedure only works with scoots without a pcv valve attached to case vent hose. Also note DO NOT OVERFILL ON OIL. Check levels as the bike is ridden(both tires on ground, bike vertical not leaned), not on centerstand or sidestand. Edit: remove hose from airbox and see if this helps relieve the issue, if it does then extend this hose to somewhere up high on the frame, and be good to go. Venting crankcase gasses back into the intake will gum up carbs, valves, etc. I always vent to atmosphere via a catchcan on my rides, but the catchcan really is optional. |
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Post by pistonguy on Jul 13, 2017 20:49:52 GMT -5
Speculating a GY6-B engine . . cylinder stud spacing is different from typical GY6 engine.
Concur there may be a piston ring blow-by issue.
Might also verify that a deficient vacuum fuel petcock diaphragm is not allowing fuel to bypass the carb.
May be overfilled if checking oil on sidestand or centerstand. I always check mine as the bike is ridden, both tires on ground, straight vertical. Did you do the leakcheck with the engine hot? Worn valve seats can seal at colder temps and open up at higher temps, allowng oil from the top end into cylinder... If my Valve Seat is Clapped Out How Does that Let Oil Into Cylinder as you state? |
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Post by chewbaca on Jul 14, 2017 13:26:05 GMT -5
Perhaps he meant valve seals. A leaking valve seal will as you know do just that. Admit oil to the intake or exhaust that is.
And a bad seal will not hurt compression.
But the runny oil sure sounds like rings.
Well new seals valves and rings will probably run a wapping $15
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Post by toddmaples on Jul 15, 2017 0:40:55 GMT -5
Perhaps he meant valve seals. A leaking valve seal will as you know do just that. Admit oil to the intake or exhaust that is. And a bad seal will not hurt compression. But the runny oil sure sounds like rings. Well new seals valves and rings will probably run a wapping $15 Yeah meant valve seals. Not the angled faces but the seals around the shaft portion that protrude thru the head... Im not very savvy when it comes to the technicalities of the head. |
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Post by cyborg55 on Jul 16, 2017 21:24:39 GMT -5
Valve stem seals are bad,, good compression,,, so rings are okie dokie
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Post by pistonguy on Jul 17, 2017 9:10:18 GMT -5
Valve Seals Wont Wait for the Engine to get warm or Hot to Puke oil, Missing or Junk Valve Seals Normally Show up as Smoke when you Wack to wfo then throttle chop off. Vacuum Sucks the Oil right past the seal.
Also Overlooking, He indicates its Hard to Start unless Throttled, then She Smoke when up to Temp, Classic Clapped Out Top End.
Yes the Second and The Oil Ring itself do control the oil but the Piston must keep the rings Square while traveling up and down the bore.
So ya a Ring Job Most likely will bring back some life but that life is very short lived when its paired with a Clapped out Piston and Cylinder Bore. Going this route you Must measure your Piston to Cylinder Clearance then run a Dingle Berry Hone to Break the old Cylinder glaze.
Most Don't Possess those tools at home or the experience to properly use them.
Unless you must get to work or wife to the hospital throwing a ring in ended a long time ago.
There are couple few ways the Ring is Junk, Trash going thru the Motor and Heat. If its the most common Trash going thru the motor, just think the Top Ring is Stainless, So if trash junked out the ring imagine what that Trash did to a Aluminum Piston and Iron Bore?
These parts are so cheap so why do all that? $75. for a Brand New Complete Cylinder Head and a Brand New 58.5 or 61mm bbk complete with Gaskets, Piston,Rings,Clips and pin. Bamm! Done!
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