GY6 150cc Timing Chain By grouchy (Read 385 times)

[grouchy]

 Hi fellow students! This is a 2014 model year Peace 150cc Scooter with 11K miles.  I suspected this engine had jumped time, as it was in a no-start condition and fuel was coming out of the air filter side of the carb. I pulled and cleaned the head. Upon reinstalling I found that the timing chain had a rough spot in it where there was a bluish colored link cover. Trying to reinstall the cam was futile as it always looked off a tooth (either side...same result) and the cam bearing stuck up in the air about 1/2" above the journal it sets on. This is the end of the cam opposite the sprocket end. I counted the links in the chain. 45 links and about 11" long. Standard steps to set the timing resulted in this. The chain seems too short and the cam will not line up with the cylinder head the way it is supposed to with the existing chain. Will a new chain fix this? Or?

[grouchy]

Hi again Students and Staff, After liberally spraying the chain with lube and letting it sit overnight, I was finally able to assemble and time the top end of this engine. I adjusted the valve clearances as well. The only new engine parts installed were a cylinder base gasket and a head gasket along with a cam chain tensioner gasket. I will let you know the outcome after I install the fuel system and attempt to fire it up!

[cyborg]

Sorry I was out for a couple days,,,,did the chain have a section of links that were stiff?

[grouchy]

Hello cyborg, Nice to meet you and thanks for the reply. Yes, the chain had one link that was stiff and did not bend very easily. I had sprayed it with WD 40 and installed it. Now...there is another problem, Once the valve clearances have been set, the setting for the exhaust seems to close up and the adjusting hardware (nut and screw) get very, very tight. I found this rotating the engine by hand. The Intake remains unchanged, but I found the exhaust was being partially open when the Intake valve was opening. What is the purpose of the spring-loaded bracket on the Rockers? Could it be part of the problem. I see the cam has a rotator with a tab on it that contacts a tab on that bracket. What is its purpose?
I have tried numerous times to set the exhaust valve, even setting it closed when the Intake Valve is open...along with the standard setting at TDC. Rotating the engine by hand it seems to stay adjusted, but when I run the electric start the exhaust valve gap closes up.  I will check the wood ruff key on the flywheel, but I initially set the timing with the head OFF and the piston at TDC at which point the flywheel timing indicator pointed very close to the T mark on the flywheel. Many say you cannot go by that and set it the way I did with the head off. What do you think?
  On another note, the engine does not start or even attempt to. 

[cyborg]

We had a few of those same conditions happen on other scooters here over the years,,,that apparatus seems to be some kind of compression release for easier starts,,,seems to do nothing but cause trouble

[grouchy]

Hi cyborg  Thank you for replying. I appreciate that. I had thought about a compression release but after reading in these and other forums for weeks and weeks, nobody has ever mentioned it. It makes sense though and I have some experience with compression release mechanisms on small Honda engines and small Briggs and Stratton engines, Wow, now things are even more complicated than before. I guess then when I find the exhaust valve slightly open, it has been designed to do that because of the ACR .(automatic compression release we will call it). OK...I get that, I just find it slightly open or beginning to open at TDC on the compression stroke,. I can turn my engine over by hand and observe the status of the valve at any point during the cycle. The idea of compression release is not new; but I agree...I think it is causing problems with my 150cc. Any advice on what I can do? If I remove the ACR bracket next to the rockers, there will be a gap there and the rockers may be wobbly then and move towards that gap? I considered doing just that today as I had the rockers off of the head, but I just reinstalled it with out removing it. What if I did remove it? Do you know if there Is there a solution to this problem, since you are the ONLY person in the forums who has ever mentioned the compression release?.And yes the ACR on those other engines is located on the camshafts also. I am pretty sure I can get this engine to run if I can get the valves to act correctly.
 Also, I wonder if the doggone ACR is letting the engine release TOO MUCH compression as mine was not properly drawing fuel from the fuel tank the way it should. I removed the tank and cleaned it out, and blew some air in and out of the petcock. I think it is OK now. 

[cyborg]

Measure the thickness of the bracket and get a hard washer and install it in its place,,or trim the arms off it and use it as a shim that'll keep the rocker arm from moving laterally on the shaft,,, as a side note there was a discussion a year or two ago about this very thing,,,the group conscience on it was that the apparatus was an anti kickback device,,,I stood by it being a compression release

[grouchy]

Hi Cyborg   Great ideas! Normally I can come up with a few on my own, sometimes simple things escape me.  Do you remember if anyone disassembled their's and if it possibly solved any valve issues they were having? I tried 2 different carbs today, a new one and the OEM one, with a direct gravity feed fuel line to them.  At first it started up and ran about a second. Then, not at all The end result was that it was pushing gas out the air filter side of the carb. I had readjusted the valve clearance on both valves before hooking up the direct fuel system.
  If you use a direct gravity fed fuel tank, do you still need to have the vacuum hose on the carb hooked to a vacuum source?.(aka the Intake Manifold) I would think you would for the diaphragm in the carb to work properly.
   So, at this point, I do not know if my problem is that ACR device, valve timing or what. I feel I may hit on the right combination sometime. It is possible I guess my timing is off about 1 tooth on the cam gear, but I explained how I set it by watching the physical location of the piston at TDC when the head was off. I can time it again if I have to. The fact that the engine is pushing gas OUT of the carb instead of sucking it in has me quite concerned.
   Quick update:  I have taken the Anti-kickback/Compression Release device out of service. Now I will see if the valves stay adjusted and/or the engine starts or just pushes fuel the wrong way out of the carb again.