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Post by lain on Jun 8, 2015 15:51:30 GMT -5
So I have messed with everything at this point but the engine itself. No changes nomatter what I do. I reach about 45, hear this horrible sound, then see my top speed drop by 10-15 until the next day.
I've adjusted the valve gaps, carb, transmission, changed the plug, coil, and cdi, checked everything in and out but have not popped the engine open yet.
These are the concerning symptoms I have:
-Top speed 42, used to be that the speedo would get way past 50 and hit the bottom of the meter and I would still be accelerating faster past the limits of the speedo.
-45+ makes the scoot feel like there is some sort of resistance in the engine and if I lay off the throttle for a second then go back up it makes FWAOOOMP noise and jerks and slows, if I do not lay off it dies
-Compression seems low compared to an identical engine with the same exact BBK, so low that I can turn my engine by hand easily, the identical engine with all good everything has much higher compression so much that it is impossible to turn by hand
-Valves were completely dry this morning when I adjusted them, usually I find oil on the parts and a small pool in the head, but today I found it bone dry.
-I put about 20ml of engine oil on the valves and cam before reassembling, when started it burned blue smoke out the muffler for about 2 minutes
-Starting always requires revving, and after a long run will not start again for 5-20 minutes, then when starting have to wait till it start sputtering then rev it, but if I rev it before it sputters like I do when the engine is cold it will just not start for longer
-Torque seems to have lowered, I can only go uphills at about 15-20, used to be 30-40 easy
-Oil seems to burn fast on some long trips, others it does not deplete at all. I fill up about 2 times a month though
I feel I need a new topend. What do you guys gather from this?
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FFWWAOOOMP!
by: geh3333 - Jun 8, 2015 17:00:01 GMT -5
via mobile
Post by geh3333 on Jun 8, 2015 17:00:01 GMT -5
Do an oil pump test . take the valve cover off and start the scoot. If the pump is working it will pump oil to the cam and rocker arms. If it is not working , no oil will be seen flowing to the head . if the pump is shot , there is a chance the engine is almost shot at this point. This is where a oil temp gauge is so important. I bet your engine is overheating and causing the noises, and the poor performance. You would have seen the temps rise and caught it early if you had a temp gauge. These scoots should have one but I guess its up to us to install one. Very very important
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Post by JerryScript on Jun 8, 2015 17:18:47 GMT -5
Two things make the crankshaft turn over easy, bad rings, and valves out of adjustment real tight or needing laping.
Running an engine at high RPMs will weaken the valve springs over time, resulting in valve float, allowing the seats to be burnt or fouled, which causes a loss of compression.
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Post by bandito2 on Jun 8, 2015 17:46:39 GMT -5
Back in the days when I was into ultralight aviation, we used a simple CHT (cylinder head temperature) sender and gauge. The sender was a special ring with a wire attached. The ring fit under the spark plug and the wire ran to a simple dial gauge. (there were digital gauges too) These were used on 2 stroke air cooled engines, but certainly I think it would work on 4 stroke motors too. You would just need to know what the normal & excessive temperatures for your engine were.
We also used EGT (exhaust gas temperature) probes in the exhaust pipe (before the muffler) in similar fashion. When you are flying with 2 stroke power, keeping tabs on engine temps was critical. But I'm not sure how helpful having EGT info would be for scooters. CHT would be useful for an air cooled scooter though. You could stop before ruining your engine if you knew for sure that it was overheating.
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FFWWAOOOMP!
by: geh3333 - Jun 8, 2015 20:21:05 GMT -5
via mobile
lain likes this
Post by geh3333 on Jun 8, 2015 20:21:05 GMT -5
Overheating can def cause issues that would make the crank turn over easy. I'm really concerned about the dry head. I would have destroyed my engine of I did not have a temp gauge. Without a temp gauge , by the time you realize your scoot is overheating , its too late , and damage very well may have already been done.
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Post by lain on Jun 9, 2015 9:29:53 GMT -5
Would a leaky valve cause the valves to dry out? I do not have overheating issues, still able to take it for a ride and handle the valve cover right after.
Is it possible to remove the engine casing to get to the oil pump to replace it without removing the top end? If I remove the topend I'd have to get a whole new BBK because I do not feel like dealing with issues from honing and new rings and etc.
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Post by rcq92130 on Jun 9, 2015 9:55:33 GMT -5
Oil pump is on the side, not the top.
Leaking valve can lead to a burned valve, and thus more of a leaky valve. In a severe case, maybe, a leaky exhaust valve could heat up the stem and cause the valve seal to fail, but that would just be evidenced by burning oil (smoke). If your oil pump gave up the ghost it's not related in any way to valves.
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Post by lain on Jun 9, 2015 10:44:58 GMT -5
Oil pump is on the side, not the top. Leaking valve can lead to a burned valve, and thus more of a leaky valve. In a severe case, maybe, a leaky exhaust valve could heat up the stem and cause the valve seal to fail, but that would just be evidenced by burning oil (smoke). If your oil pump gave up the ghost it's not related in any way to valves. Well it smoked after putting some oil on the valves. The chain still seems lubricated, just the top end does not seem lubricated after letting it sit. I have not checked right after running because I do not want to stress the threads and strip one. Do I have to drain the oil before working on the pump? I am checking the manual now, seems it cracks open right under the flywheel basically? The manual does not say anything about oil in this part though. |
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Post by rcq92130 on Jun 9, 2015 11:38:49 GMT -5
Oil pump is on the side, not the top. Leaking valve can lead to a burned valve, and thus more of a leaky valve. In a severe case, maybe, a leaky exhaust valve could heat up the stem and cause the valve seal to fail, but that would just be evidenced by burning oil (smoke). If your oil pump gave up the ghost it's not related in any way to valves. Well it smoked after putting some oil on the valves. The chain still seems lubricated, just the top end does not seem lubricated after letting it sit. I have not checked right after running because I do not want to stress the threads and strip one. Do I have to drain the oil before working on the pump? I am checking the manual now, seems it cracks open right under the flywheel basically? The manual does not say anything about oil in this part though. Ask GEH to write up a little tutorial on this - he just did the job a few months back if I remember correctly. Your chain would be getting oil from dipping into the sump and the oil therein, not from the top end oil system. As someone (maybe GEH) suggested, pull the valve cover and turn the engine over by hand. You should see some oil seeping out from the valve carrier. If not, either blocked poil passage or faulty oil pump or no oil in the engine. |
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Post by lain on Jun 9, 2015 12:35:57 GMT -5
Well it smoked after putting some oil on the valves. The chain still seems lubricated, just the top end does not seem lubricated after letting it sit. I have not checked right after running because I do not want to stress the threads and strip one. Do I have to drain the oil before working on the pump? I am checking the manual now, seems it cracks open right under the flywheel basically? The manual does not say anything about oil in this part though. Ask GEH to write up a little tutorial on this - he just did the job a few months back if I remember correctly. Your chain would be getting oil from dipping into the sump and the oil therein, not from the top end oil system. As someone (maybe GEH) suggested, pull the valve cover and turn the engine over by hand. You should see some oil seeping out from the valve carrier. If not, either blocked poil passage or faulty oil pump or no oil in the engine. Does the oil flow up the engine rods? I do not see any other place besides the chain that the oil could come from. Page 22 of the gy6 service manual I got from this forum shows a diagram that kind of looks like it flows up the rods? But the rods are covered by the cam and nuts right? So how would that work? |
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Post by rcq92130 on Jun 9, 2015 13:09:00 GMT -5
Ask GEH to write up a little tutorial on this - he just did the job a few months back if I remember correctly. Your chain would be getting oil from dipping into the sump and the oil therein, not from the top end oil system. As someone (maybe GEH) suggested, pull the valve cover and turn the engine over by hand. You should see some oil seeping out from the valve carrier. If not, either blocked poil passage or faulty oil pump or no oil in the engine. Does the oil flow up the engine rods? I do not see any other place besides the chain that the oil could come from. Page 22 of the gy6 service manual I got from this forum shows a diagram that kind of looks like it flows up the rods? But the rods are covered by the cam and nuts right? So how would that work? AlleyOop described this very well about a year ago. 1. For the piston rings, gudgeon pin, etc.: the GY6 is a "splash system". Oil is splashed up every time the crank rotates down into the pool of oil in the sump. There is no pressure feed system for this part of the motor. This is also how the chain gets oiled 2. For the top end (valve carrier and camshaft bearings): oil is PUMPED up to the valve carrier from an oil passage in the crankcase to an opening UNDERNEATH the jug. If you look at the jug turned upside down you will see an odd crescent shaped groove. One end of this sits right over the oil passage on the surface of the crankcase. The other end is at the top/left head bolt. Oil actually travels up ALONG SIDE of that head bolt thru the jug and into the head - then into a passage within the head to the valve carrier. That is the reason why we are urged to only use silicone sealant sparingly on the paper gasket between the crankcase & the jug - excess sealant can / will be squeezed as you torque down the head bolts and might get into the little passageway along the head bolt and into the head, clogging it. Then no oil will reach the top end. That's why so many people have suggested removing the valve cover and specifically looking for oil seeping out from the valve carrier as the engine is turned. |
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Post by lain on Jun 9, 2015 13:36:49 GMT -5
Thanks that helps a lot! Looking at my old jug I can see the shape you are talking about, and I think I may have found gasket pieces in the oil that may have come off the crescent shape because the gaskets seem to overlap into the crescent shape a bit nomattter how perfectly I place them.
I am guessing my oil passage may be clogged with gaskt pieces. I remember finding gasket pieces in my oil a couple months ago but when I did not find anymore I thought it was okay.
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FFWWAOOOMP!
by: geh3333 - Jun 9, 2015 18:37:05 GMT -5
via mobile
Post by geh3333 on Jun 9, 2015 18:37:05 GMT -5
Thanks that helps a lot! Looking at my old jug I can see the shape you are talking about, and I think I may have found gasket pieces in the oil that may have come off the crescent shape because the gaskets seem to overlap into the crescent shape a bit nomattter how perfectly I place them. I am guessing my oil passage may be clogged with gaskt pieces. I remember finding gasket pieces in my oil a couple months ago but when I did not find anymore I thought it was okay. Did you test to see if the pump was working ? I doubt its clogged. If no oil is getting to the head , 9 times out of 10 the pump is bad. If you do the oil pump test , and find that is bad , let me know and I'll give you a run through on what to do to change it . |
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Post by lain on Jun 9, 2015 20:35:55 GMT -5
Thanks that helps a lot! Looking at my old jug I can see the shape you are talking about, and I think I may have found gasket pieces in the oil that may have come off the crescent shape because the gaskets seem to overlap into the crescent shape a bit nomattter how perfectly I place them. I am guessing my oil passage may be clogged with gaskt pieces. I remember finding gasket pieces in my oil a couple months ago but when I did not find anymore I thought it was okay. Did you test to see if the pump was working ? I doubt its clogged. If no oil is getting to the head , 9 times out of 10 the pump is bad. If you do the oil pump test , and find that is bad , let me know and I'll give you a run through on what to do to change it . How many turns of the flywheel should produce oil in the head? Like right away? |
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Post by lain on Jun 10, 2015 6:55:42 GMT -5
well I don't see any oil. I know how to change the pump, or I think I do, based off the manual, but like I said before I would like to know if I have to drain the oil first, the manual does not say there is any oil in the area where the pump is.
I do not want to have to find out the hard way, I have enough auto spill spots on my pavement............
So do I need to drain the oil??
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