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Post by usmcdoc on Nov 6, 2011 9:14:16 GMT -5
Tx....I did the valve adjust as per the first link.....turning clockwise only.....in fact it is marked with an arrow on the flywheel. But I still get the exhaust valve to stay open about 1/3 revolution while the intake valve is open....which does not seem normal to me. Also I am curious that if the rings are worn...would the blow by increase crank pressure or blow oil into the head and force oil out vent hose? Oil leak only happens while driving(under a load) if I hold it at 6,000 rpm on the center stand for 5 mins...all I get are gaseous vapors from the vent hose. Driving test and on the center stand testing is done with vent hose removed from airbox. Lastly.......the air coming from the vent hose is not a faint *puff*....it feels almost like it is coming from an air compressor nozzle. I would assume you should maybe feel a slight puff of air.....not something that feels that strong....since the cylinder head/valve cover and engine are a sealed system.
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Post by stepthrutuner on Nov 6, 2011 18:48:29 GMT -5
When the engine is under load a lot more pressure is in the cylinder due to the piston resisting being moved and blowby will increase to a large extent if the rings can't stop it
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Post by stepthrutuner on Nov 6, 2011 20:58:21 GMT -5
Heck, I'd go up to as big as I could w/o having to trim the cases. Don't know what that is.... probably close to 180cc. My advise would be to go on out to 150cc at least. You'll love yourself for it.
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Post by speedy1125 on Nov 6, 2011 21:05:41 GMT -5
Heck, I'd go up to as big as I could w/o having to trim the cases. Don't know what that is.... probably close to 180cc. My advise would be to go on out to 150cc at least. You'll love yourself for it. right on id build that sucker as big as i could go. Enviromoto has bore kits for the gy6 125s and 150s. if your motor has the same stroke as a 150 then it most likely is the same bottom end as a 125/150 with a tiny jug and a bigger jug should go right on unless the case is smaller where the cylinder sleeve slides in. get a measurement on the cylinder sleeve for us. |
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Post by 90GTVert on Nov 6, 2011 22:05:50 GMT -5
If you just went up to a stock 150 top end, assuming it fits, that would be a big gain and you'd have replacement parts more readily available than the big bore kits. You can't go much bigger than a 150's stock bore on the 150s anyway without case work. They might have better specs for compression and such in the 155ish cc kits though. Like they said though, really depends how this sorta one-off engine turns out to be setup.
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Post by usmcdoc on Nov 6, 2011 22:38:49 GMT -5
I am hoping it will work. Stroke should be the same as the 150 short case. The company told me it was a 125 short case with a 47 mm piston. A gy6 50 with a 47 mm comes out to only 72 cc...so in order for my 47 mm piston to be 100(97) as marked on the cylinder..... it must have a longer stroke just like the gy6 150... it uses a 743-20-30 belt...and is identical to my buddies 150 from what I see on the outside anyway.. :stumped:
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Post by speedy1125 on Nov 6, 2011 23:56:37 GMT -5
do you have a micrometer? measure the cylinder skirt on the outside. I am very interested in what size it is. it would be wild if it was a qmi/qmj gy6 150 case with a qmb cylinder. i dont think this is possible though since the connecting rod would probably hit the skirt but how are they making a 47mm jug work? verrrry interesting  |
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Post by 49ccsofdestruction on Nov 7, 2011 6:23:35 GMT -5
you better name this thing "pandora" after all this! sounds like you are on the right track. good luck
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Post by usmcdoc on Nov 7, 2011 21:04:38 GMT -5
Took a better look after tear down using digital calipers.....found the following. Piston is clean/clear with no discoloration or even a scuff mark. cyl bore is 46.69..piston diameter is 46.67. comp ring gaps in cylinder are .0015 for both. Oil ring gaps are .003 Wavy oil ring gap is greater than .030 (but they don't expand to touch cylinder?) Wrist pin is 14.84mm. Cylinder base(where it fits in engine block) measures 58.21. So all seems super tight in tolerance. Does anybody know what the cylinder base diameter for a gy6 125 is?Very curious about that. In case I upgrade I am sure that is all the bigger I can go. Anyway it appears the cylinder/ piston is not causing the high pressure oil blow by that comes out of my vent tube like a Wagner spray paint gun ::)y.
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Post by Fox on Nov 7, 2011 21:29:35 GMT -5
I'm about 99% sure the cam stopper is not to blame for the loss of oil. It takes two rotations of the cam to equal one rotation of the crank so 1/3 of a turn on the cam is about right for the valves to stay open.
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Post by usmcdoc on Nov 7, 2011 22:08:40 GMT -5
Fox...yes...but BOTH valves open at the same time...for that long? I sure can't be blow from the piston rings....the end gaps are actually tighter than what they recommend...this confusing...
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Post by Fox on Nov 7, 2011 22:32:29 GMT -5
The only way both valves can open at the same time is if the cam is twisted like a wrung out towel. It goes like this: The intake valve opens as the piston moves downward on stroke 1 sucking in fuel/air, The intake valve closes and then the piston moves upward compressing the fuel/air (stroke 2) , The piston reaches TDC and then the spark plug fires driving the piston down (stroke 3), Then the piston moves and up and the exhaust valve opens (stroke 4), the exhaust valve closes and then the cycle starts all over again. This shows a double overhead cam engine. Yours is a single OHC so the cam lobes are in different positions on the same cam rather than two separate cams.  |
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Post by usmcdoc on Nov 7, 2011 22:51:01 GMT -5
Fox....see that extra lobe(shown by arrow) next to the exhaust lobe...it rotates and is elliptical in shape and has a one way bearing in it.... It is supposed to keep the exhaust valve open if the engine tries to fire backwards...but when I rotate the engine clockwise the exhaust valve opens followed by the elliptical lobe on that piece...keeping the exhaust open almost all the way through the intake vales opening. Thinking the one way bearing in that piece has gone bad. Not sure what else to think as the rings and cylinder are even tighter that factory specs. All I know is that blowing one quart of oil in 3-4 miles...something is causing the pressure. Is the oil pump output adjustable for flow?... :beatup: Attachments:
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Post by speedy1125 on Nov 8, 2011 0:49:21 GMT -5
Is the oil pump output adjustable for flow?...  no |
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Post by usmcdoc on Nov 8, 2011 19:18:52 GMT -5
Took a better look after tear down using digital calipers.....found the following. Piston is clean/clear with no discoloration or even a scuff mark. cyl bore is 46.69..piston diameter is 46.67. comp ring gaps in cylinder are .0015 for both. Oil ring gaps are .003 Wavy oil ring gap is greater than .030 (but they don't expand to touch cylinder?) Wrist pin is 14.84mm. Cylinder base(where it fits in engine block) measures 58.21. So all seems super tight in tolerance. Does anybody know what the cylinder base diameter for a gy6 125 is?Very curious about that. In case I upgrade I am sure that is all the bigger I can go. Anyway it appears the cylinder/ piston is not causing the high pressure oil blow by that comes out of my vent tube like a Wagner spray paint gun ::)y. Ok so now that I know the vent hose is not pinched or clogged.....engine tear down shows piston cylinder and all rings all tighter that normal specs....I can rule out piston blow by. Oil level is just shy of the full mark(so not overfilled) Valves on right on are .004....so again I asked....does anybody know what would cause so much pressure that a quart of oil will blow out the vent tube within 5 miles...whether hooked to the air box or open vented to the air. Is there another crankcase vent on a gy6 that may be plugged?...Is it possible that the oil pump is malfunctioning? It is not burning oil as the plug is a nice light brown color and dry. Also I verified that the baffle is in place in the valve cover and it is not blocked. I have heard that MANY people with the 150 size gy6 engines have had this problem....somebody must have experience in this arena with them....had same thing happen. It sucks to get better gas mileage than oil mileage... :sos: |
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