Hi Everyone New Here! -- Can't Find TDC -- TURNS OVER / NO START

[polishpipes10]

Hi everyone,

I am new here and I am having a major problem finding TDC on my Super 8 150cc 2009. Any help or suggestions at all would be greatly appreciated.

Thank you

[scooterfan]

You can just have a close look at the camshaft sprocket. It will have two small holes and two big holes between the center and outer edge of the sprocket.
When the piston is at TDC, the two smaller holes will be in line with the top of the cylinder head.

While the two smaller holes are in line with the cylinder head, you also need to have a good look at the position of the camshaft lobes. If the piston is at TDC, both camshaft lobes will be facing towards the REAR of the engine.

It the lobes are facing towards the front of the engine, it means the piston is NOT at TDC, and the crankshaft needs to be turned another 360 degrees - until the two smaller holes at the sprocket will be in line with the upper level of the cylinder head again.
Or, if you are a bit unsure about using the camshaft lobes as pointers:
- if the two smaller holes are in line with the upper level of the cylinder head, you can have a look at the timing marks at the Flywheel. If the piston is at TDC, the timing mark at the flywheel will be in line with the timing mark on the engine casing. If the timing mark on the flywheel does not line up with the timing mark on the casing - it means the engine needs to be turned another 360 degrees, until the two smaller holes at the camshaft sprocket gets in line with the upper level of the cylinder head again.  The piston will then be at TDC, and the timing marks on the flywheel and engine casing will line up with each other.

You can also have a look at the video below . Don't worry if your scooter is not the same model as the scooter on the video. These scooter engines are similar to the GY6 engine copies, and the timing marks at the camshaft sprockets, flywheel, and engine casings are exactly the same.



P.S. (There is no need to remove the carburetor - the video is just to show the holes at the camshaft sprockets, as well as the timing marks on the camshaft pulley and engine casing.)

[Stig / Major Tom]

Also, if all is confusing - with the sprocket holes aligned, as above - you must be able to feel movement up & down when you take hold of the rocker arms. If no movement...do not proceed, you are not at TDC....rotate engine again, align sprocket holes, feel again for movement

Stig

[scooterfan]

Also, if all is confusing - with the sprocket holes aligned, as above - you must be able to feel movement up & down when you take hold of the rocker arms. If no movement...do not proceed, you are not at TDC....rotate engine again, align sprocket holes, feel again for movement

Stig

Problem with that is that if the current valve clearance gaps are too small, there might be no play (no movement) at the rocker arms while the piston is indeed at TDC position.
Therefore it should be better not to use rocker arm movement as guideline.

I forgot to mention - when the engine gets turned to line up everything, the engine always needs to be turned clockwise (facing the cooling fan / flywheel side of the engine).
The reason being - if the engine gets turned anti-clockwise the chain slack at the “tensioner-shoe side” of the chain will prevent the timing marks from lining up 100% correctly.

[Stig / Major Tom]

Problem with that is that if the current valve clearance gaps are too small, there might be no play (no movement) at the rocker arms while the piston is indeed at TDC position.
Therefore it should be better not to use rocker arm movement as guideline.

Point taken - but my final test before I proceed with loosening any lock nut is to test for rocker arm movement.
In 52 years of setting the valve lash on air cooled engines I have never found intake and exhaust valves to both be without movement when at TDC.
It is not the first step in the procedure - but it is always my final "proof".
Stig

[polishpipes10]

You can just have a close look at the camshaft sprocket. It will have two small holes and two big holes between the center and outer edge of the sprocket.
When the piston is at TDC, the two smaller holes will be in line with the top of the cylinder head.

While the two smaller holes are in line with the cylinder head, you also need to have a good look at the position of the camshaft lobes. If the piston is at TDC, both camshaft lobes will be facing towards the REAR of the engine.

It the lobes are facing towards the front of the engine, it means the piston is NOT at TDC, and the crankshaft needs to be turned another 360 degrees - until the two smaller holes at the sprocket will be in line with the upper level of the cylinder head again.
Or, if you are a bit unsure about using the camshaft lobes as pointers:
- if the two smaller holes are in line with the upper level of the cylinder head, you can have a look at the timing marks at the Flywheel. If the piston is at TDC, the timing mark at the flywheel will be in line with the timing mark on the engine casing. If the timing mark on the flywheel does not line up with the timing mark on the casing - it means the engine needs to be turned another 360 degrees, until the two smaller holes at the camshaft sprocket gets in line with the upper level of the cylinder head again.  The piston will then be at TDC, and the timing marks on the flywheel and engine casing will line up with each other.

You can also have a look at the video below . Don't worry if your scooter is not the same model as the scooter on the video. These scooter engines are similar to the GY6 engine copies, and the timing marks at the camshaft sprockets, flywheel, and engine casings are exactly the same.



P.S. (There is no need to remove the carburetor - the video is just to show the holes at the camshaft sprockets, as well as the timing marks on the camshaft pulley and engine casing.)

Thank you for the video link it was very helpful, however, my flywheel with the markings T and F are clearly visible. The problem I am having is I cannot find for the life of me the mark I am supposed to be lining the T up with. I have seen at least 4 different articles telling me 4 different places it should line up with, none of which have worked. One said to line it up in the center of the "V" on the casing. Another shows me an area on the casing that does not exist on mine. You get the point. I would like to avoid having to pull apart and reassemble everything each time I need to check if the mark is indeed lined up with the casing. I have been troubleshooting this for over a week now with no transportation and have missed work because of this. It is very late here, but I will attach a pic tomorrow of my flywheel and the casing that I have (which doesn't seem to match ANY other casing I have found in my research). Hopefully this is something really simple and I will been able to get this thing to turn over again and be on my way, but as of tonight, After lining up the marks on the camshaft and making sure the larger hole is away from engine (up), along with trying to find this mystery mark on the casing near the flywheel, all I get is the sound you get when you turn the key and try and start but it just keeps trying to start but justs keeps rolling the camshaft and the flywheel with no actual turn over of the motor starting. THIS HAS BECOME SO FRUSTRATING! I AM READY TO THROW IT OFF A BRIDGE! JK!!

So another quick question, if the timing is off, is that a reason why the engine will not actually start up? or could I have the timing right and maybe something else is causing the problem? Also when removing the cylinder head earlier this week, (which is the entire reason I began this repair because spark plug hole is stripped beyond repair) I notice a piece of a VERY strong magnet fall out of somewhere. Any idea what that might be and could that be causing my problem as well by any chance.

Thank you so much for your replies and I look forward to your next response.

Allan

[scooterfan]

Thank you for the video link it was very helpful, however, my flywheel with the markings T and F are clearly visible. The problem I am having is I cannot find for the life of me the mark I am supposed to be lining the T up with. I have seen at least 4 different articles telling me 4 different places it should line up with, none of which have worked. One said to line it up in the center of the "V" on the casing. Another shows me an area on the casing that does not exist on mine. You get the point. I would like to avoid having to pull apart and reassemble everything each time I need to check if the mark is indeed lined up with the casing. I have been troubleshooting this for over a week now with no transportation and have missed work because of this. It is very late here, but I will attach a pic tomorrow of my flywheel and the casing that I have (which doesn't seem to match ANY other casing I have found in my research). Hopefully this is something really simple and I will been able to get this thing to turn over again and be on my way, but as of tonight, After lining up the marks on the camshaft and making sure the larger hole is away from engine (up), along with trying to find this mystery mark on the casing near the flywheel, all I get is the sound you get when you turn the key and try and start but it just keeps trying to start but justs keeps rolling the camshaft and the flywheel with no actual turn over of the motor starting. THIS HAS BECOME SO FRUSTRATING! I AM READY TO THROW IT OFF A BRIDGE! JK!!

So another quick question, if the timing is off, is that a reason why the engine will not actually start up? or could I have the timing right and maybe something else is causing the problem? Also when removing the cylinder head earlier this week, (which is the entire reason I began this repair because spark plug hole is stripped beyond repair) I notice a piece of a VERY strong magnet fall out of somewhere. Any idea what that might be and could that be causing my problem as well by any chance.

Thank you so much for your replies and I look forward to your next response.

Allan

Sorry to hear about your misfortune.

Firstly, I only now realize that the cylinder head has been removed, the Camshaft and camshaft have been removed, and the timing chain has been separated from the camshaft sprocket.

In short - in cases like this there is no "short cut" to line everything up correctly. As a "starting point", unfortunately you need to  find that "missing" aligning mark somewhere at the casing, or wherever it might be. Otherwise you can easily be running in circles for a long period.

Rather ignore my initial suggestion to have a close look at the position of the cam lobes, because that's just an easy way to check whether the piston is at TDC when all timing marks have been lined up correctly PREVIOUSLY.

In this case the engines timing could easily be WAY off - simply because the timing marks at the crankshaft Pulley and engine Casing (or wherever) have not be lined up correctly initially. If fact - your engine's timing could easily be off as far as 180 degrees at the camshaft , while the pulley is indeed at TDC.

So the answer is yes, in your case incorrect timing is most probably the reason why the scooter doesn't start.

Unfortunately I never worked on a scooter like yours - so I have no idea where the alignment mark you're looking for is suppose to be. Hopefully somebody else will be able to help ?  Also forward some close photos, it might give us an idea.

I have no idea where the magnet was coming from. A close photo might help to point us in the right direction as well.

Good luck, I hope to see some photos soon.

[Stig / Major Tom]

If your scoot agrees with photos 2 and 3 - you are at TDC. (unless some one has been there before you, and really screwed things up)
If you can see as in photo #1 - that's a bonus! the 'line' and the 'T' will be next to the 'V' in the engine case. Often, really hard to see even with flash light.

OK, this will get you able to do a valve clearance check....but, sadly I think you have more issues than the valves. You might need to start looking for other transportation!
I hope I am wrong. Truly. I know what it's like to be without transportation.

Also, there is no magnet in a scooter cylinder head cover. If it fell out of the cylinder head cover when you removed it - it was likely ingested by the engine. Perhaps it fell 'off of' the cylinder head exterior?
Is it a small barrel shaped magnet - possibly come adrift from an oil drain plug?

Stig

[scooterfan]

Just to explain my previous post - in the last paragraph of polishpipe10's previous post, he mentioned that the cylinder head has been removed from the engine.
Now, on an engine with overhead camshaft there is now way  how any given cylinder head can be removed, without removing the timing chain from the camshaft sprocket.
Which means (in this case)  the timing chain was hooked back on the camshaft during re-assembling (after the cylinder head was back in place) . Therefore the camshaft sprocket has most probably not been hooked to the chain correctly .

@ polishpipe10
I think the 3rd photo (above, "must feel up and down movement") should not be used to determine whether the piston is at TDC  or not - simply because the correct timing marks have clearly not been used to hook the  camshaft sprocket back on the chain during re-assembling.  Chances are very good that you will not find any movement anyway.






 

[polishpipes10]

If your scoot agrees with photos 2 and 3 - you are at TDC. (unless some one has been there before you, and really screwed things up)
If you can see as in photo #1 - that's a bonus! the 'line' and the 'T' will be next to the 'V' in the engine case. Often, really hard to see even with flash light.

OK, this will get you able to do a valve clearance check....but, sadly I think you have more issues than the valves. You might need to start looking for other transportation!
I hope I am wrong. Truly. I know what it's like to be without transportation.

Also, there is no magnet in a scooter cylinder head cover. If it fell out of the cylinder head cover when you removed it - it was likely ingested by the engine. Perhaps it fell 'off of' the cylinder head exterior?
Is it a small barrel shaped magnet - possibly come adrift from an oil drain plug?

Stig

Good morning, here are the pics of what I see if I align the T onto the V on the casing. Looks Like it's correct to me, or am I wrong?

One thing I did notice however is that the rocker heads have zero play. They will not move at all?

Another question I have is, is putting the exhaust pipe back on a necessity when trying to see if it will start? Cause I have NOT been doing that because it is such a pain my a**! I just assumed that if it did start without exhaust pipe it would just be hella loud. Is that causing any trouble by not putting it back on before trying to start?

Also I attached the piece of magnet that I found. I'm pretty sure it did not fall out of the case. It looks to me as if it might be one of the magnets from the inside of the flywheel perhaps. Would that make it not start if one of those fell off?

Thanks again for taking time out to help me with this annoying and time consuming problem. I greatly appreciate your knowledge and expertise.

[scooterfan]

Good morning, here are the pics of what I see if I align the T onto the V on the casing. Looks Like it's correct to me, or am I wrong?

One thing I did notice however is that the rocker heads have zero play. They will not move at all?

Another question I have is, is putting the exhaust pipe back on a necessity when trying to see if it will start? Cause I have NOT been doing that because it is such a pain my a**! I just assumed that if it did start without exhaust pipe it would just be hella loud. Is that causing any trouble by not putting it back on before trying to start?

Also I attached the piece of magnet that I found. I'm pretty sure it did not fall out of the case. It looks to me as if it might be one of the magnets from the inside of the flywheel perhaps. Would that make it not start if one of those fell off?

Thanks again for taking time out to help me with this annoying and time consuming problem. I greatly appreciate your knowledge and expertise.

Don't worry, I think your first two photos are a good indication that you will be able to get the engine running soon.


1.  Firstly, The ""V" at the casing on your photo looks like the correct mark when the piston would be at TDC position.


2. Secondly, the two smaller holes at the camshaft Sprocket (2nd photo) is lining up with the upper level of the cylinder head, but there is a MAJOR problem - the big hole at the camshaft sprocket is not visible, and is currently located at the opposite side of where it is suppose to be seen while the "T" mark is at the position,  indicated at your 1st photo.

To my mind this means chances are about 100% that the  scooter's timing is 180 degrees off at the moment. This obviously happened when the Camshaft has been put back in place after the cylinder head has been removed.
Don't feel bad about this, I've made the same mistakes, and only learned the hard way.

This is what I would do:

1. Make sure the "T" mark at the pulley is in line with the "V" at the casing (like indicated at your 1st photo).

2. Loosen and remove the Crankshaft- and crankshaft Sprocket-combination completely, and turn the crankshaft 180 degrees, until the big hole at the crankshaft Sprocket is located at a 90 degree posission with the upper level of the cylinder head.  (Remember to keep an eye on the "T" and "V" aligning marks (point 1 above) at the same time - because those marks need to line up correctly when the big hole at the Camshaft pulley is clearly visable, and located at a 90 degree position with the upper level at the cylinder head).

Sorry about the weird description - my first language is not English.

Don't worry about the exhaust - when everything has been lined up correctly, the engine should fire up perfectly without an exhaust.

The only thing that worries me, is the loose magnet. I have no idea where it came from. Maybe you should rather contact a dealer, and try to talk to one of their mechanics ?








 


 

[polishpipes10]

 OK, cool yes I see how that would be a major problem so I am going to go and do that now and I’ll get back to you and tell you what my results are thank you again .

[CROSSBOLT]

Hang on a second! Cam turns at one-half speed of crank, right? Turn the crank one more revolution and the holes in the cam gear should be right, right? Confirm this before doing anything else, please.

[scooterfan]

Hang on a second! Cam turns at one-half speed of crank, right? Turn the crank one more revolution and the holes in the cam gear should be right, right? Confirm this before doing anything else, please.

100 % correct. That’s the exact reason why I advised him to turn the crankshaft only 180 degrees, and NOT 360 degrees.  (Should he turn the Crank Shaft 360 degrees while the “T” and “V” marks line up, the Crank Shaft would end up at the very same, INCORRECT position)

@polishpipes10

I almost forgot - while you are lining up everything correctly, I think it would make sense to hook the scooter’s battery to a battery charger in the meanwhile. Due to all the engine cranking while you were trying to start the engine, the battery Voltage might be too low to start the engine at this stage. The reason being - if your scooter has a DC CDI and the Power supply to the CDI is less than about 9.5 Volt at this stage, the engine could easily not start, simply because the power supply to the CDI would be too low to create a spark at the spark plug, and to start the engine.

[CROSSBOLT]

Gotcha, scooterfan!  No, not "a gotcha!" but I roger what you are saying! That is, I think I understand.....crank revolves once (360 deg), cam revolves 1/2. Yep. That's right. The "T" shows up every revolution of the crank but the cam makes only a half-turn. So if he were to turn his crank one more turn from his picture, then his cam ought to look like Stig's except not as shiny! (Nobody's cam is as shiny as Stig's!)

I agree about charging the battery while we do all this!