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Old February 12th, 2017, 12:09 AM   #1
Bluberryrain
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Cam not sitting flush when timing?

Hi there!

Today, I decided to dive in and check my valves, and adjust as necessary. Good thing I did so, because the exhaust valves were out of spec.

So, I got everything taken apart without issue, measured the shims, did the math, and went and got new shims. I got them installed with the lifters.

However, now- when I go to put the cam back in, and attach the chain, the cam doesn't seem to sit flush when the timing marks on the cam gears are aligned. It feels like a teeter-totter, if you push on the end opposite the cam gear, the cam gear lifts a little bit out of the journal. It also appears that this is happening because of the lobes on cylinder two is resting on one of the lifters.

When I took the bike apart, I made sure that the engine was set at 2T through the viewing window & the timing marks on the gears were aligned. The viewing window shows that the engine is still set at 2T. Since the intake clearances were within spec, I did NOT remove the intake cam or cap. I took the bolts out of it, but did not remove the cap or cam, so it's been in the same spot. I'm simply trying to re-align the exhaust cam with it by the timing marks. Here are some pictures:

Here you can see that the engine is set to 2T:



Here you can see that the timing is aligned:



Here you can see that the cam is off kilter when the timing is aligned:



Here you can see that this is likely due to the lobe resting on the lifter:



And finally, here you can see when the timing marks are mis-aligned one tooth, the cam does not sit off kliter, and does not teeter totter:



So, my fellow ninjette riders, what have I done? How does one go about resolving this? Do I have to remove the intake cap and cam, and realign them together? Any help ya'll can give me would be much appreciated. I did plenty of research on this before starting, and also have the service manual, but I'm still sitting here scratching my head.
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Old February 12th, 2017, 12:16 AM   #2
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Not sure why the pictures won't embed- maybe because they are too big. If you right click on them, and choose "Open in new tab" they will load, or you can view the whole album here:

http://imgur.com/a/nTkR6
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Old February 12th, 2017, 06:44 AM   #3
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You are fighting the forces of the valve's springs.

Align the sprockets first.
Rotate cam shaft until all the cams are away from the buckets.
Put some grease in the journals and bolt them down in the indicated sequence and torque.
Rotate everything and verify alignment of sprockets.
Verify gaps between cams and buckets.
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Old February 12th, 2017, 09:48 AM   #4
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Just some advice about this

Line everything up then turn the engine back 15 deg . Bolt down the caps without Any spring tension . Then rotate the engine back. Do this with the tentioner out and just use your finger to push in the tension on the chain guide.

This is very important when taking things apart. That cocking action on the cam can brake the end of the cam.
This is done without the plugs in place. So you will not feel any resistance as you turn the engine back and forth. The final check is done with the the tensioner in place and after cranking the engine around twice in the normal direction.

And always set the exhaust cam first then take up the cam chain slack and do the intake cam last . It is OK to carefully rotate the engine back or forth as long as you hold the tention on the cam chain with your finger.
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Old February 12th, 2017, 01:15 PM   #5
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Thanks for the advice guys! You two are always so helpful around here!

I'll do this, and report back
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Old February 12th, 2017, 03:15 PM   #6
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Quote:
Originally Posted by Racer x View Post
Just some advice about this

Line everything up then turn the engine back 15 deg . Bolt down the caps without Any spring tension . Then rotate the engine back. Do this with the tentioner out and just use your finger to push in the tension on the chain guide.

This is very important when taking things apart. That cocking action on the cam can brake the end of the cam.
This is done without the plugs in place. So you will not feel any resistance as you turn the engine back and forth. The final check is done with the the tensioner in place and after cranking the engine around twice in the normal direction.

And always set the exhaust cam first then take up the cam chain slack and do the intake cam last . It is OK to carefully rotate the engine back or forth as long as you hold the tension on the cam chain with your finger.

I held the tension down on the cam chain, and turned the engine counter-clockwise a few degrees. However, this just causes the intake cam to fight against the valve pressure instead.
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Old February 12th, 2017, 03:28 PM   #7
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So,

Should I turn the engine back so that the exhaust cam sits flush against the caps, and bolt it down without valve pressure, turn the engine forward to 2T (in which the cam lobes will push down on the buckets), and bolt down the intake without valve pressure? And then install the tensioner, check the clearance, etc.
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Old February 12th, 2017, 04:28 PM   #8
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Quote:
Originally Posted by Bluberryrain View Post
So,

Should I turn the engine back so that the exhaust cam sits flush against the caps, and bolt it down without valve pressure, turn the engine forward to 2T (in which the cam lobes will push down on the buckets), and bolt down the intake without valve pressure? And then install the tensioner, check the clearance, etc.
The crankshaft turns two times while the cam shafts rotate once.
The 2T mark only indicates that cylinder 2 is at top dead center.

There is a rotational position of the crankshaft (within 720 degrees of rotation) for which none of the cam lobes force the valves open by pressing on the valve.
If both spark plugs have been removed, there is no resistance from compression to easily find that spot.

I see no reason to have the cam tensioner removed during this operation, except for previously cleaning and lubricating the tensioner's mechanism, but I may be wrong.



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Old February 12th, 2017, 04:37 PM   #9
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Quote:
Originally Posted by Motofool View Post
The crankshaft turns two times while the cam shafts rotate once.
The 2T mark only indicates that cylinder 2 is at top dead center.

There is a rotational position of the crankshaft (within 720 degrees of rotation) for which none of the cam lobes force the valves open by pressing on the valve.
If both spark plugs have been removed, there is no resistance from compression to easily find that spot.

I see no reason to have the cam tensioner removed during this operation, except for previously cleaning and lubricating the tensioner's mechanism, but I may be wrong.



Thanks, Hernan. Looking at your first attachment, my cam gears are in the opposite position. The line with EX & IN are facing each other on the inside, and my exhaust is up instead of down, and vice versa with the intake.

So, I should be able to turn the crank around until the cams look like the picture, and everything should fit- I think. Even if this isn't the case, as long as I start with the timing lining up, I can rotate the crank until both cams fit within that above-mentioned rotational position.
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File Type: jpg Screen Shot 2017-02-12 at 4.34.23 PM.jpg (83.1 KB, 13 views)
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Old February 12th, 2017, 05:16 PM   #10
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Originally Posted by Bluberryrain View Post
......... So, I should be able to turn the crank around until the cams look like the picture, and everything should fit- I think. Even if this isn't the case, as long as I start with the timing lining up, I can rotate the crank until both cams fit within that above-mentioned rotational position.
Cylinder #2 is the cylinder on your right when you normally sit on the bike.
Normal rotation of the crankshaft is counter-clockwise when looking at the engine from the left (generator/chain sprocket) side.

The 2T mark (which is solidly linked to the crankshaft) indicates that piston #2 is at the top position with IN and EX valves perfectly closed (which means end of the compression stroke and beginning of the work stroke).

For that to be true (an the timing of the valves to be correct), all the EX and IN cam lobes for that cylinder should be pointing up and away from each other).
For higher precision, the lines marked on the cam sprockets should align with the edge of the cylinder's head.

Same should happen for cylinder #1 (left one).

For more clarity, please read this:
http://www.cyclepedia.com/ninja-250-...lve-clearance/
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Old February 12th, 2017, 09:10 PM   #11
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Quote:
Originally Posted by Motofool View Post
Cylinder #2 is the cylinder on your right when you normally sit on the bike.
Normal rotation of the crankshaft is counter-clockwise when looking at the engine from the left (generator/chain sprocket) side.

The 2T mark (which is solidly linked to the crankshaft) indicates that piston #2 is at the top position with IN and EX valves perfectly closed (which means end of the compression stroke and beginning of the work stroke).

For that to be true (an the timing of the valves to be correct), all the EX and IN cam lobes for that cylinder should be pointing up and away from each other).
For higher precision, the lines marked on the cam sprockets should align with the edge of the cylinder's head.

Same should happen for cylinder #1 (left one).

For more clarity, please read this:
http://www.cyclepedia.com/ninja-250-...lve-clearance/

Right, so with the understanding that the crankshaft will hit 2T twice per revolution, I cycled the crankshaft to the second 2T while holding tension on the chain, and there was no more teeter tottering, (I could have also just left the crankshaft where it was, taken the cams out and rotated them 180 degrees) and I managed to get the lines on the cam sprockets lined up with the cylinder head.

However, the cam lobes for exhaust cylinder 1 were sitting on top of the bucket. So, I rotated the engine a little bit, until the lobes were sitting flat on the bucket, put the caps on and bolted everything down. Then, I turned the engine back to 2T again.

Quote:
The 2T mark (which is solidly linked to the crankshaft) indicates that piston #2 is at the top position with IN and EX valves perfectly closed (which means end of the compression stroke and beginning of the work stroke).

For that to be true (an the timing of the valves to be correct), all the EX and IN cam lobes for that cylinder should be pointing up and away from each other).
With the engine at 2T, cylinder 2's EX & IN valves are perfectly closed, as the cam lobes are facing away from each-other, in the same way you'd check the clearance. Exhaust valve buckets are starting to get pushed down on cylinder 1.

Is this thing timed? Seems like it to me anyways.
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Old February 12th, 2017, 09:43 PM   #12
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........Is this thing timed? Seems like it to me anyways.
I believe it is.
Timing of both cylinders is 90 degrees out of phase, with cylinder #1 leading.

Congratulations !!!





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Old February 13th, 2017, 07:05 PM   #13
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I believe it is.
Timing of both cylinders is 90 degrees out of phase, with cylinder #1 leading.

Congratulations !!!





Yeahhh!! Thank you for all your help, Hernan!! Got it all bolted back together.

Hopefully this thread will help someone else out in the future.

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Old February 13th, 2017, 07:15 PM   #14
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Yeahhh!! Thank you for all your help, Hernan!! Got it all bolted back together.

Hopefully this thread will help someone else out in the future.

You are welcome, Nick

I would rotate the crankshaft by hand several times just to make sure that valves are not hitting the top of the pistons, as well as double check the gap or clearance of the valves.

Glad that you have learned some new tricks and have felt the satisfaction of working in your machine.

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Old February 13th, 2017, 08:01 PM   #15
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That cocking action on the cam can brake the end of the cam.
werd. had this happen.

Quote:
Originally Posted by Racer x View Post
And always set the exhaust cam first then take up the cam chain slack and do the intake cam last . It is OK to carefully rotate the engine back or forth as long as you hold the tention on the cam chain with your finger.
HELPFUL HINTS

I tend to use a small dab of paint on the chain and sprocket to easily align things upon reassembly. From there, I still count the links, and rotate the engine twice to double check, but the paint does make this go faster.

Also, My method of setting the exhaust cam easily comes with the use of a tiny screwdriver placing pressure on the chain in between the head and the chain/sprocket. In this manner, I can keep the chain from jumping once tension is applied via the cam tensioner.....THAT STUPID CHAIN IS ALWAYS JUMPING ON ME!!!
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Old February 13th, 2017, 08:04 PM   #16
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Originally Posted by Bluberryrain View Post
Thanks, Hernan. Looking at your first attachment, my cam gears are in the opposite position. The line with EX & IN are facing each other on the inside, and my exhaust is up instead of down, and vice versa with the intake.

So, I should be able to turn the crank around until the cams look like the picture, and everything should fit- I think. Even if this isn't the case, as long as I start with the timing lining up, I can rotate the crank until both cams fit within that above-mentioned rotational position.
you need to flip both cams 180 degrees and make sure the 2T mark is aligned with the protrusion in the cover from that pic of your engine.
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Old February 17th, 2017, 04:29 PM   #17
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You are welcome, Nick

I would rotate the crankshaft by hand several times just to make sure that valves are not hitting the top of the pistons, as well as double check the gap or clearance of the valves.

Glad that you have learned some new tricks and have felt the satisfaction of working in your machine.

Just wanted to close the loop here for all- I got everything bolted back on and checked the clearances, all exhausts are at .29 mm (most of them were less than .16). Took the bike for it's first ride today as it was somewhat nice outside (around 50 degrees F)........

and the bike ran GREAT. I have 14k miles on the bike, and I bought it with 9k. Previous owner was a young kid who did ****-all for maintenance. The bike wouldn't start when it was cold without full choke, and the choke had to remain open until the bike was completely warm. Taking off from the stop had to rev up, etc.

Now, the bike starts up with full choke, and you can immediately turn the choke off and ride. Idling is nice and smooth, take offs are smooth, and dare I say- some power seems to be restored.

Seriously guys, take the time to do your valve adjustments. It may look like a complete hassle, and an arduous task - but it's really not that bad. Not to mention you've got an amazing community of people here to provide support.
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Old February 17th, 2017, 08:13 PM   #18
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.........and the bike ran GREAT...........
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