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Post by acvw74 on Jul 13, 2018 6:59:05 GMT -5
When you pull the head...if the valve seat insn't damaged...you might be able to simply swap the valve out. It will save you a bunch of money.
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Post by GrumpyUnk on Jul 14, 2018 11:19:44 GMT -5
If the valves are bent, you could just order a set of valves, washers, retainers and valve keepers for less than $5, ballpark. If you don't feel able to disassemble & re-assemble the mechanism, watch a youtube video for hints and helps. I was able to compress the valves on re-assembly using my fingers. I guess it depends on wallet and skill depths respectively(?). If the valves were sticky, you could also get zero compression. After removing the head, you can use H2O to check for leakage if you expect to replace the head. Actually, you can use it anytime if you are willing to take things apart and dry them thoroughly. A 'hot air gun' or hair dryer will get things hot enough to evaporate any liquid left behind after testing, IMO. Remember, the cam will be synchronized properly if it is installed upside down with the piston/crankshaft at TDC. It does not know that it is upside down, as it will get there on the next revolution after being synched with the cam upright. tom
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Moat
Scoot Member
Posts: 88
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Post by Moat on Jul 15, 2018 5:08:16 GMT -5
Remember, the cam will be synchronized properly if it is installed upside down with the piston/crankshaft at TDC. The problem there is that the cam is holding the valves open slightly at that point (overlap) and therefore things are but a tooth or two away from contact/bending a valve... which is likely what happened. For safest measure, lobes should always be pointed away from the followers (downwards, towards the piston) and the adjustment screws/nuts removed while installing a head and/or setting the cam timing. Bob
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Post by GrumpyUnk on Jul 15, 2018 9:59:57 GMT -5
Not affecting the 'timing' of the valves, but affecting the valve lash. The cam still will be synchronized properly, which was the point of the post. The second point was to remind readers that the cam is ignorant, opens and closes based on its connection to the crankshaft, not the position of the cam sprocket. People had worried about installing the cam 'upside down', and the point is that upside down works exactly the same as 'rightside up'... because TDC is TDC is TDC ... no matter where the cam is. tom
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Moat
Scoot Member
Posts: 88
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Post by Moat on Jul 15, 2018 10:54:31 GMT -5
Absolutely, Tom - timing is the same either way. It's just that the less experienced wrenchers need to understand that there is indeed a "right" way during assembly, just as the manual instructs - big sprocket hole up, lobes down - as it greatly reduces the chance of bending a valve. Unfortunately, that particular detail seems to get missed time and time again, leading to just this kind of thread repeating itself.
Bob
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Post by wilyhammers on Jul 31, 2018 9:10:50 GMT -5
Sorry for the delay here - I had a ton of rain and I have to do all of my work outside.
I took the head off - yep, the valve is stuck open. Ordered a new head (it wasn't expensive) and got it going. I have trouble with idle however. It will only idle currently with the idle mixture screw WAY out (so far out it rotates with the engine and will eventually screw itself out) and the idle stopper way in as well. I have the A9 cam in.
I rechecked my valve clearance again, .004". I'll double check my TDC and cam one more time to verify I'm not a tick off. The engine does run like a beast anytime other than idle.
I'll double check vacuum, see if anything is up with air intake (I'll remove the air filter for a min and see if it improves idle). I guess I could rejet the idle but I just have a feeling a slightly mis-sized yet couldn't make it perform _quite_ this badly.
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Post by acvw74 on Jul 31, 2018 21:20:22 GMT -5
Glad you got it running, but from what you described...sounds like a vacuum leak. Make sure the intake manifold is seated well.
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Post by GrumpyUnk on Aug 1, 2018 12:12:34 GMT -5
Gotta go with acvw ... you are feeding a lot of fuel compared to a needle that is 1-1.25 turns out.
Check that the elbow has a good gasket/O-ring. They can fall off and not be noticed readily. tom
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Aug 1, 2018 13:19:35 GMT -5
Gotta go with acvw ... you are feeding a lot of fuel compared to a needle that is 1-1.25 turns out. Check that the elbow has a good gasket/O-ring. They can fall off and not be noticed readily. tom I just replaced my intake last weekend and was surprised to see a 1/2" thick spacer under it and, 2 full flange gaskets and no O-ring. Since I have no idea where to even buy these gaskets, this weekend, I am going to use some high-temp. rtv gasket sealer. This is just a standard run of the mill Chinese gy6 49cc 4T and I have never seen this type of intake set-up before. My new intake has the O-ring so I will seal the spacer sides and then install the new intake. Ever heard of one like this? That spacer is stock as the guy I got my scoot from did not do any work on the engine at all. I had no idea that would be in there either. Bill
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Post by GrumpyUnk on Aug 6, 2018 9:40:47 GMT -5
All I have seen are equipped with a ~.5" tall phenolic(bakelite?) spacer. Between the spacer and the cylinder head is a paper gasket. The plastic elbow has a groove and O-ring on the surface that meets with the upper surface of the spacer. One thing to look for is significant poor alignment of the spacer with the intake port on the head. I have seen them where it appears that 1/4 of the intake port is misaligned with the spacer. I have elongated the holes in the spacer to allow better port alignment, and then held the spacer in a 'better' aligned position while tightening the nuts onto the studs. tom
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Aug 6, 2018 13:24:19 GMT -5
Thanks. I looked up this "spacer" and they call it an "insulator" so, I suppose it is there to keep the carb./intake manifold from getting too hot. My alignments were ok but, I had to wrestle with that heat shroud to get the spacer installed correctly. I looked everywhere online to try to buy those gaskets for that spacer and no one seems to sell them alone...they want you to buy the spacer, gasket and intake, 2 of which I do not need.
Bill
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Post by GrumpyUnk on Aug 7, 2018 12:05:37 GMT -5
Get thee to a NAPA and purchase some gasket paper. Or empty the Cheerios or Saltines box, and cut one out using scissors and an X-acto knife. There's no real pressure, and cardboard should work fine. tom
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