Tight Timing Chain

GrouchyOle'Man · 10-14-2017, 04:25 PM

Hello, On my 150cc GY6 after installing new chain guides (but not the tensioner) I find that my chain once installed on the CAM sprocket is SO tight, that the cam cannot even rest on its bearing journal on the end opposite the sprocket. I have had the cylinder off and the head off numerous times. Videos I have seen show substantial SLACK in the timing chain allowing one to easily correctly time the engine. I tried it with the cylinder and head dowels placed correctly and the 2 long head bolts in place and snugged up. There is some slack, but not enough. Has anyone else experienced this?

crawford · 10-15-2017, 11:10 AM

Did you check old parts with new? There really shouldn't be a big difference between old and new it really sounds like there is a wrong part to me to be that tight.

GrouchyOle'Man · 10-15-2017, 02:56 PM

Hi Crawford, I suspected a timing issue with this engine as it was not drawing fuel out of the carburetor; so it had a no-start condition. I have installed a few new parts, but no new engine parts. Today I found a blue link on the timing chain that would not rotate as easily as all the other links and was kinked. I straightened it out. I do not know if the chain was ever tampered with. Everything is as I found it except the cylinder base gasket and head gasket which I replaced since I had the top end of the motor off. They were identical to the ones they replaced. Even after straightening out the blue link, the same situation exists. The inside cam bearing is above the journal it rides on about 1/2". Also, I cannot properly set the cam in correct timing position. It is always off by one tooth. Either side of the sprocket, I get the same result. Off one tooth and camshaft not seating. So, the only parts to compare OLD to NEW are the 2 gaskets and chain guides. I may opt for counting the links in the chain to see if one was previously removed to facilitate tightening up the chain. I do not know yet if a new chain will fix this. The gear on the crank the chain rides on is suspect also. I fear it is quite worn. This scoot has over 11K miles on it according to the odometer.
Again, this is with the automatic chain tensioner NOT installed. The old timing chain guides had some damage to them and I replaced them. I initially thought a piece of plastic off the bottom of the lower guide was stuck in the timing chain gear on the crankshaft, then I found the kink in the blue link. At any rate, the chain seems to be too short to properly reinstall.
So after trying to assemble the top of this engine numerous times without success; I guess my next step is to count the number of chain links in my timing chain and compare it to a new one. I just counted 45 links and the chain is about 11" long. I have seen new ones for sale that are exactly that size.

crawford · 10-18-2017, 12:06 PM

My question before you has any body been in it before did you get it this way ?

Roscoe · 10-18-2017, 04:23 PM

Something isn't right. Is the chain seated on the crankshaft gear?

GrouchyOle'Man · 10-18-2017, 06:57 PM

Hello crawford, Yes, the scooter had a previous owner. It just quit running in the rain one day this summer. My Grandson was riding it.

Hi Roscoe, Yes, absolutely something was not right. The chain had a slight kink in it. Keeping the chain on the crank gear has proved to be quite a challenge. The kink in the chain could have been from when it possibly jumped time a couple months ago. I sprayed lube on it and let it soak overnight and today it was less stiff and I was finally able to assemble the top end of the engine. I also timed it and adjusted the valves again. There is a very slight gap where the timing chain rides on the teeth of the cam gear. Hopefully she will not jump time, but we will see. If it does, it is going to need a new crank gear and/or timing chain. I am going to install the fuel system and let you guys know what happens.

crawford · 10-20-2017, 12:41 AM

It really sounds like you need to count the links on old one and see if you could get another. I believe you will be doing it again maybe stuck and will be walking it back no fun. Do it right the first time you chain is bad and it will fail just trying to save you extra time redoing the job again.

GrouchyOle'Man · 10-21-2017, 07:29 PM

Crawford Lubing the chain helped. I was able to install it with the cam and rockers, etc. Now though...and this is odd...the exhaust valve KEEPS coming out of adjustment; not the Intake but the exhaust. It stays open a small amount sometimes when the Intake valve is opening. Also, after assembled engine does not start. Just to let you know the adjuster and lock nut are in good condition and are not stripped. I do not overtighten the locknut when I set it.

crawford · 10-21-2017, 10:33 PM

Try squirting some spray lube on valve stem while you open and keep closing valve even if you need to tape valve closed keep doing it you most likely find valve start moving freely again you may have built up carbon inside of valve guide.

GrouchyOle'Man · 10-22-2017, 09:59 AM

Hi Crawford The valve moved freely through the guide when I reassembled it and seemed like it was not sticking when I put it back in the HEAD as I had removed the cylinder head and cleaned the carbon out. You may be right about carbon in the guide though. I did not pay that a lot of attention. We had run some fuel additive in the gas and there was not much carbon on the head or piston. Trying to start the engine with Gunk Carb/Choke Cleaner aerosol spray had broken up even more carbon. It has all been removed. I have adjusted the exhaust valve when the Intake valve is open on the Intake stroke, and adjusted it when the Piston is at TDC. Once I try to start the engine with the electric start, the clearance closes up and the lock nut and set screw for the exhaust valve become very, very tight...even tighter than I had tightened it. That results in the valve being partially open. I do NOT overtighten it when I set it. I know better.
The engine STILL does not fire up or start. I may check the flywheel key today, even though I had set the timing initially with the head off the engine so I could see the piston, not just gauge it. I pulled the head to inspect the condition of the valves and springs and to clean the carbon.

crawford · 10-22-2017, 11:44 AM

could valve be a site bent just enough to hang up? when apart did you try moving valve up and down with no sticking?

GrouchyOle'Man · 10-22-2017, 04:50 PM

Crawford I love your questions. If the exhaust valve IS bent, it is very, very slight. Yes, I moved the valve up and down in the guide several times while the head was off. I noticed nothing wrong then; but you make a good point. Fooled with it today. The timing key on the flywheel was fine, the Intake valve was fine. Compression seems to be fine (between 160 and 170)...but that doggone exhaust valve still is losing its' clearance. I find when I adjust the valve clearance really wide, it seems to stay where I put it, but if I adjust it where it is supposed to be, it gets super tight and the valve is in the opening stage. I do NOT know exactly how much it is open, but it is not right at any rate. The engine still is not starting as I found the engine was NOT pulling enough vacuum to pull fuel OUT of the fuel tank through the vacuum operated petcock. I moved air back and forth through it and I think it is OK now.
The engine WILL run however as I had it running on carb cleaner for about 8-12 seconds a couple weeks ago.

Roscoe · 10-22-2017, 08:59 PM

what I'd probably do,.... run it a few minutes by spraying carb cleaner in into the carb. Or gas from a squeeze bottle, ... or a temp gas tank gravity feed to the carb (like from an old mower)... or plug the vacuum from the manifold and use a different vacuum source to cause the petcock to stay open. I'm thinking you need to run this thing a while and let it loosen up or break so you can ID the problem and fix it.
Stay after it, we'll get it going or find the reason why it won't.

Roscoe · 10-22-2017, 09:04 PM

Part II ... duh, I just realized if it's a GY6 150 the tank will gravity feed by running a gas line from the tank directly to the carb... you can bypass the petcock ... if it's like the one I have. You can also take the air cleaner hose off and hand choke it to start and partially hand choke it to keep it running, by putting your hand over the intake of the carb.

GrouchyOle'Man · 10-23-2017, 08:50 AM

Hi Roscoe I certainly appreciate the input. This engine has me a little frustrated because it defies just about all I do to it. I was mistakenly told that the CAM STOPPER PLATE on the Rocker assembly was a possible compression release mechanism. A forum member who was very good and does not appear to be around on here anymore (Alleyoop) had stated in a much earlier thread that it's purpose was to keep the engine from running backwards. I have altered it and now may need to reinstall a standard one.

10-23-2017, 08:50 AM	#15
GrouchyOle'Man Join Date: Sep 2017 Location: NE Central Florida Posts: 37	Hi Roscoe I certainly appreciate the input. This engine has me a little frustrated because it defies just about all I do to it. I was mistakenly told that the CAM STOPPER PLATE on the Rocker assembly was a possible compression release mechanism. A forum member who was very good and does not appear to be around on here anymore (Alleyoop) had stated in a much earlier thread that it's purpose was to keep the engine from running backwards. I have altered it and now may need to reinstall a standard one. Last edited by GrouchyOle'Man; 04-01-2018 at 10:49 AM.
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10-15-2017, 11:10 AM	#2
crawford Join Date: Jun 2015 Location: Dandridge,tn 37725 Posts: 57	Did you check old parts with new? There really shouldn't be a big difference between old and new it really sounds like there is a wrong part to me to be that tight.
	0

10-18-2017, 12:06 PM	#4
crawford Join Date: Jun 2015 Location: Dandridge,tn 37725 Posts: 57	My question before you has any body been in it before did you get it this way ?
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10-18-2017, 06:57 PM	#6
GrouchyOle'Man Join Date: Sep 2017 Location: NE Central Florida Posts: 37	Hello crawford, Yes, the scooter had a previous owner. It just quit running in the rain one day this summer. My Grandson was riding it. Hi Roscoe, Yes, absolutely something was not right. The chain had a slight kink in it. Keeping the chain on the crank gear has proved to be quite a challenge. The kink in the chain could have been from when it possibly jumped time a couple months ago. I sprayed lube on it and let it soak overnight and today it was less stiff and I was finally able to assemble the top end of the engine. I also timed it and adjusted the valves again. There is a very slight gap where the timing chain rides on the teeth of the cam gear. Hopefully she will not jump time, but we will see. If it does, it is going to need a new crank gear and/or timing chain. I am going to install the fuel system and let you guys know what happens.
	0

10-20-2017, 12:41 AM	#7
crawford Join Date: Jun 2015 Location: Dandridge,tn 37725 Posts: 57	It really sounds like you need to count the links on old one and see if you could get another. I believe you will be doing it again maybe stuck and will be walking it back no fun. Do it right the first time you chain is bad and it will fail just trying to save you extra time redoing the job again.
	0

10-21-2017, 07:29 PM	#8
GrouchyOle'Man Join Date: Sep 2017 Location: NE Central Florida Posts: 37	Crawford Lubing the chain helped. I was able to install it with the cam and rockers, etc. Now though...and this is odd...the exhaust valve KEEPS coming out of adjustment; not the Intake but the exhaust. It stays open a small amount sometimes when the Intake valve is opening. Also, after assembled engine does not start. Just to let you know the adjuster and lock nut are in good condition and are not stripped. I do not overtighten the locknut when I set it.
	0

10-21-2017, 10:33 PM	#9
crawford Join Date: Jun 2015 Location: Dandridge,tn 37725 Posts: 57	Try squirting some spray lube on valve stem while you open and keep closing valve even if you need to tape valve closed keep doing it you most likely find valve start moving freely again you may have built up carbon inside of valve guide.
	0

10-22-2017, 09:59 AM	#10
GrouchyOle'Man Join Date: Sep 2017 Location: NE Central Florida Posts: 37	Hi Crawford The valve moved freely through the guide when I reassembled it and seemed like it was not sticking when I put it back in the HEAD as I had removed the cylinder head and cleaned the carbon out. You may be right about carbon in the guide though. I did not pay that a lot of attention. We had run some fuel additive in the gas and there was not much carbon on the head or piston. Trying to start the engine with Gunk Carb/Choke Cleaner aerosol spray had broken up even more carbon. It has all been removed. I have adjusted the exhaust valve when the Intake valve is open on the Intake stroke, and adjusted it when the Piston is at TDC. Once I try to start the engine with the electric start, the clearance closes up and the lock nut and set screw for the exhaust valve become very, very tight...even tighter than I had tightened it. That results in the valve being partially open. I do NOT overtighten it when I set it. I know better. The engine STILL does not fire up or start. I may check the flywheel key today, even though I had set the timing initially with the head off the engine so I could see the piston, not just gauge it. I pulled the head to inspect the condition of the valves and springs and to clean the carbon.
	0

10-22-2017, 11:44 AM	#11
crawford Join Date: Jun 2015 Location: Dandridge,tn 37725 Posts: 57	could valve be a site bent just enough to hang up? when apart did you try moving valve up and down with no sticking?
	0

10-22-2017, 04:50 PM	#12
GrouchyOle'Man Join Date: Sep 2017 Location: NE Central Florida Posts: 37	Crawford I love your questions. If the exhaust valve IS bent, it is very, very slight. Yes, I moved the valve up and down in the guide several times while the head was off. I noticed nothing wrong then; but you make a good point. Fooled with it today. The timing key on the flywheel was fine, the Intake valve was fine. Compression seems to be fine (between 160 and 170)...but that doggone exhaust valve still is losing its' clearance. I find when I adjust the valve clearance really wide, it seems to stay where I put it, but if I adjust it where it is supposed to be, it gets super tight and the valve is in the opening stage. I do NOT know exactly how much it is open, but it is not right at any rate. The engine still is not starting as I found the engine was NOT pulling enough vacuum to pull fuel OUT of the fuel tank through the vacuum operated petcock. I moved air back and forth through it and I think it is OK now. The engine WILL run however as I had it running on carb cleaner for about 8-12 seconds a couple weeks ago.
	0

10-22-2017, 08:59 PM	#13
Roscoe Join Date: Nov 2016 Location: N. of Texas and S. of Kansas Posts: 252	what I'd probably do,.... run it a few minutes by spraying carb cleaner in into the carb. Or gas from a squeeze bottle, ... or a temp gas tank gravity feed to the carb (like from an old mower)... or plug the vacuum from the manifold and use a different vacuum source to cause the petcock to stay open. I'm thinking you need to run this thing a while and let it loosen up or break so you can ID the problem and fix it. Stay after it, we'll get it going or find the reason why it won't.
	0

10-22-2017, 09:04 PM	#14
Roscoe Join Date: Nov 2016 Location: N. of Texas and S. of Kansas Posts: 252	Part II ... duh, I just realized if it's a GY6 150 the tank will gravity feed by running a gas line from the tank directly to the carb... you can bypass the petcock ... if it's like the one I have. You can also take the air cleaner hose off and hand choke it to start and partially hand choke it to keep it running, by putting your hand over the intake of the carb.
	0