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About to check valves and I am stumped at TDC marks on my bike

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Hello CRF gurus!

Well, its time for me to check the valve clearances on my 07 CRF250r.  This is the first time I have check valves on a 4Stroke, so please be patient with my questions.  

Note:  I just got down riding my bike for 2 days in North Florida, and it started just fine, ran just fine for both days....so I am not experiencing any staring issues or running issue, except with the backfiring that is going on when off throttle.  

I started to disassemble the bike to check the valves and when trying to put the bike into TDC, I noticed a few things that looked odd.  After taking some pics, I noticed there are 2 gears on the crank side that have notches in them.  One is closer to the viewing window and one is further back.  When the furthest one back is lined up with the notch on the case, the timing and cam marks line up much better (see second set of pics below).  

So, which notch am I suppose to use to find TDC?  Also, if the timing marks are off a bit when the cam wheel notches are parallel to the case, is that ok, or should I adjust?  If so, how?

When the notches are lined up on the crankside (closest to the viewing hole), the lobes are no where near pointing towards the rear of the bike.  

I then went to line up the timing marks, the notches on the cam gear line up much better but still a little off, but the crank notches are no where visible in the window.  

What should I do, adjust, etc?  Any help, suggestion, tips would be great!  I want to take the time to make any changes now while I have the oil out of the bike and checking the valves.

With Crank notches aligned:

CRANK

Cam Shaft

Timing

Cam Wheel Marks

With Cam and Timing Notches aligned (close) to case:

CRANK

Cam Shaft

Timing

Cam Wheel Marks

Thanks!

 

 

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I'm not sure this helps your situation...but I don't think you're on the compression stroke. Usually, the cam lobes should be at about 2 o'clock facing the rear of the bike.

Someone can correct me if I'm wrong.

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46 minutes ago, tvalliere220 said:

use the outer point on the right side inspection cover.

Ok...so to clarify...use the dot on the outer gear?  As in the pic that shows the notch lining up with the case?  Also, should I adjust the cam wheel by a tooth so the marks are parallel to the case when I re-assemble?  

Also....how do you get 2 o'clock when facing the rear?  What position would be considered 12 o'clock?  Directly parallel to the case and straight back to the back?

 

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46 minutes ago, TPA-MX said:

 

Also....how do you get 2 o'clock when facing the rear?  What position would be considered 12 o'clock?  Directly parallel to the case and straight back to the back?

 

This is what I'm talking about. As you can see in the pic...just about every vid/pic tutorial I've seen about checking clearances...the cam lobes are facing the rear of the bike at about 2 o'clock when it's at TDC on the compression stroke. Yours looks like it's at 7 o'clock where you insert the feeler gauge. Again...I'm not 100% on this...someone can correct if it's bad info.

 

lobes.jpg

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Actually looking at your pic again...your lobes look correct. The pic was a little deceiveing and tricked my eye a bit. Carry on...

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Your setup is way off judging by your pics. You have to line up the marks on the right side (to get tdc, as shown here), then install your cam and cam chain and get it installed so that the cam gear marks are lined up with the top of the cylinder head (like shown in your pic here), then make sure your crank marks on the right side are still lined up, get down eye level to get a good view with one eye. After its all installed and cam chain tensioner installed/putting tension on the chain, all those marks need to line up in both pics I mentioned, and cam lobes facing the rear. I'm pretty sure the owners manual has these instructions also. If you are 1 or 2 teeth off, your valves will hit your piston!

Edited by tom02cr250
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10 hours ago, tom02cr250 said:

Your setup is way off judging by your pics. You have to line up the marks on the right side (to get tdc, as shown here), then install your cam and cam chain and get it installed so that the cam gear marks are lined up with the top of the cylinder head (like shown in your pic here), then make sure your crank marks on the right side are still lined up, get down eye level to get a good view with one eye. After its all installed and cam chain tensioner installed/putting tension on the chain, all those marks need to line up in both pics I mentioned, and cam lobes facing the rear. I'm pretty sure the owners manual has these instructions also. If you are 1 or 2 teeth off, your valves will hit your piston!

Thank you Tom02!  If the bike is way off, how would it run, start, etc?  

Regarding the right side, I align the crank gear mark on the inner gear (smallest one that is closest to the nut and washer that is holding it on the the rod) correct?  I sweat that I see 2 different notches on 2 different gears when looking in the hole at eye level.

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I was wondering the same thing.. Yes a bunch of us have explained it, the 1 dot on the outer gear closest to the crank Allen bolt, that dot has to line up with the mark on the right crankcase cover, and at the same time the cam gear marks have to line up/be parallel to the top of the cylinder head, they should line up within line 1 mm, if they are off more like by a 1/4" then the chain would be off 1 tooth. 

Judging by your post and the pics, all your timing marks were not lining up at the same time. 

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2 hours ago, tom02cr250 said:

I was wondering the same thing.. Yes a bunch of us have explained it, the 1 dot on the outer gear closest to the crank Allen bolt, that dot has to line up with the mark on the right crankcase cover, and at the same time the cam gear marks have to line up/be parallel to the top of the cylinder head, they should line up within line 1 mm, if they are off more like by a 1/4" then the chain would be off 1 tooth. 

Judging by your post and the pics, all your timing marks were not lining up at the same time. 

Tom,

Thanks!  So, the alignment is way off.  I am just REALLY confused on how the bike would start and run, pretty well I might add.  

I just checked all the valves, they all needed to be adjusted.  the Right intake was super low, hence the backfiring I was experiencing when off the throttle.  To clarify the re-assembly, I need to adjust everything in this order:

  1. Turn the primary gear to where i THINK the engine is at TDC.  Currently when the primary gear is aligned with the notch on the case, the lobes are either pointing almost straight up or pressing down on the valves.  I will get the engine so that the lobes are pointing up?  I think that the exhaust lobe might just be starting to engage the rocker.  Does this sound good?
  2. Once this is done, re-align the cam and wheel so that the notches on the cam gear are parallel with the case.  Also the lobes will be pointing back, and slightly up
  3. Does the timing marks matter during this process?

Cheers and thanks everyone.

Edited by TPA-MX

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Man you are really struggling to comprehend this haha. First you get the engine at TDC using the crank marks on the right as I explained already. Then release the tension on the cam chain and unbolt your cam, then remove the cam chain from the cam gear and rotate the cam so that the lobes are pointing towards the rear and line up the cam gear timing marks and you have to put the chain on so that the cam gear timing marks are parallel at the top of the cylinder head, this can be difficult to get right just keep trying. Then you put your cam back together/bolted up and make sure all your timing marks are lined up correctly before bolting/torqueing down the cam,  get down and check your crank right side mark. Then you check your valve clearances. Your valve clearances won't be right unless your timing marks are all lined up correctly then you can figure out if you need to adjust your valve shims.

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I don't know how your bike ran lol,  and must have been backfiring because your timing was way out of whack. When it's at top dead center and everything is right there will be no pressure  on the valves and you'll have valve clearance or at least you should unless your valves are bad. Insert your feeler gauges from the rear under the intake cam lobes. Release the tensioner so there is tension on the chain after bolting down the cam and make sure all the timing marks are still lined up good.

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If youre having issues getting it timed again try using the marks on the flywheel to get to tdc rather than the gear on the right. Its much easier to see and there is a lot less difference in the position of the cam when its off just a hair.
Also rather than installing the chain tensioner to see if its still lined up, just use a dowel or something to press on the chain. Thats if you dont have one of those little tools to lock the tensioner in place, I just use a screwdriver and remove it.

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1 hour ago, tom02cr250 said:

Man you are really struggling to comprehend this haha. First you get the engine at TDC using the crank marks on the right as I explained already. Then release the tension on the cam chain and unbolt your cam, then remove the cam chain from the cam gear and rotate the cam so that the lobes are pointing towards the rear and line up the cam gear timing marks and you have to put the chain on so that the cam gear timing marks are parallel at the top of the cylinder head, this can be difficult to get right just keep trying. Then you put your cam back together/bolted up and make sure all your timing marks are lined up correctly before bolting/torqueing down the cam,  get down and check your crank right side mark. Then you check your valve clearances. Your valve clearances won't be right unless your timing marks are all lined up correctly then you can figure out if you need to adjust your valve shims.

Yea, that is sort of what I as trying to say.  Thanks for the patience.  That all makes sense now...

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Tom,

One last question on the steps you provided.  When I get the primary gear notch lined up on the right side, and then adjust the cam/wheel so the at the lobes and wheel marks are in the correct position, what if the timing marks on the flywheel are not showing through the hold on the left side of the engine?  

Thanks!

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The timing marks on the left side are supposed to line up when the timing marks on the right side line up, both ways are a way to find top dead center. I've never used them marks on the left I know you have to use one of the two marks on the left I can't remember which one. But if your mark on the right doesn't line up when your mark on the left does then that is weird. Take your spark plug out and put a screwdriver or something down there on top of your piston to find top dead center (when the screwdriver is at the highest point)  and then see if the right side Mark is where it should be or if the left side Mark is correct. 

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7 minutes ago, tom02cr250 said:

The timing marks on the left side are supposed to line up when the timing marks on the right side line up, both ways are a way to find top dead center. I've never used them marks on the left I know you have to use one of the two marks on the left I can't remember which one. But if your mark on the right doesn't line up when your mark on the left does then that is weird. Take your spark plug out and put a screwdriver or something down there on top of your piston to find top dead center (when the screwdriver is at the highest point)  and then see if the right side Mark is where it should be or if the left side Mark is correct. 

Yea, that is what was really confusing me.  I can get the timing marks on the flywheel, marks on the cam wheel and the cam lobes to all align, but the notch on the primary gear (right side) is not visible.  When I adjust the primary gear on the right side so the notch is visible, then the lobes are pointed almost straight up, the cam wheel marks are at a 2 and 7 o'clock position (not parallel) and the timing marks on the fly wheel are not visible.  

Is is possible that the primary gear was just put on incorrectly?  Because I can get 3 out of the 4 to align but not the primary gear notch.

I am going to do the screw driver trick for sure....I just need to find something that will fit down in the spark plug tube to get it out.

Edited by TPA-MX

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