Camchain help

Yama

Jason
Messages
15
Reaction score
0
Points
1
Location
Reading, pa
Hello my fellow 650 lovers. I hope someone can help me with my situation. I am in the middle of an engine rebuild on my 1975 xs650b and everything was going great until I installed the camchain. I was going to re-use my old chain since the engine was rebuilt about 15 yrs ago, not by me and before I owned it, but the vertical Mark on the cam sprocket and timing mark on the rotor don't line up. The vertical mark is about one tooth either direction off. So I figure chain stretch and order new chain from mikes. Install new chain and situation is improved but mark is still not as straight up as the manual shows. My question is, since it is only slightly forward from vertical should I leave it and hope when I tighten all nuts down the new gaskets and such compress enough to bring it to vertical. My first rebuild by the way, so please forgive me if I'm being overly cautious. I just want to make certain I do it right the first time. Thank you
 
Last edited:
Thank you for you response Brian. I've seen that article and it was a help. My problem is if you draw a vertical line through the center of the engine the mark should line up with that on the camshaft sprocket, according to the manual. While the new chain is closer to that center vertical line, it still is not exactly vertical. The chain is tight running from sprocket to sprocket in te front and slack in the back at the tensioner as it should be. I left the mark in the camshaft sprocket slightly forward in hopes of compressing the new gaskets, thus bringing that mark to vertical. With new gaskets will the mark be exactly vertical or do I need to compress them to get it to that mark.
 
Don't try to eyeball the camshaft timing notch without a line to sight on. Use a pencil, small wood dowel, whatever, to hold a line in the end of the crankshaft, and pull the line up across the camshaft center. Do this with one bearing on each end of the camshaft and the cam chain adjuster installed finger tight to take the slack out of the front run of the chain. If you can't get the notch parallel to the line by moving the camshaft under the chain, you'll need to either adjust deck height or move the camshaft sprocket. Athena head gaskets are around .017" thicker than original equipment. If that's what you installed, try a Vesrah gasket; they're made to OE specs.
 
Last edited:
Yama;

You only mention one reference mark, the vertical notch on the left side (12:00 position) of the camshaft, but there is a second reference mark on the right side.

With rotor at TDC, there is a punch mark on the right side of the camshaft gear, which should be at about the 09:00 position, and it should be exactly even with the top surface of the head. If the punch mark is even with the head surface then you are in good shape.
 
I did use a gasket kit from mikes, Athena. I hadn't thought of gasket thickness, good point. Is there any way I can use the Athena kits since the mark is not that far off or am I just asking for trouble. It's just I'd hate to buy a new gasket set when I just did that, but if I must I will, you guys are the experts. The cam sprocket is fixed so I can't move that. There is only a vertical mark on this cam sprocket, no punch mark to align with top of head. Will leaving the mark just slightly forward have a significant effect on the timing. I should probably post a pic so people can see how little it is off. Thank you all for your help, I'm so frustrated by this little problem, I thought the new chain would resolve the issue.
 
You can buy just a head gasket, you don't have to buy the whole gasket set. I'm pretty sure 650Central sells them. If you are considering that, you may as well bolt the head down and see what happens. You were going to replace that gasket anyway.

You may not be looking for that dot in the proper place on the other side of the cam sprocket. It's located towards the outer edge, not in tighter like the notch. You did look on the other side, right? On the right hand side of the sprocket, the advance unit side of the cam. It's not on the same side as the notch.
 
Here's a pic that also shows the camchain timing with the engine at TDC. The yellow line shows how the slot, in the slotted disc, alines for the small pin. If you have that then you're good to go.

The punch mark or dot on the right side of the camshaft gear has to be there.
 

Attachments

  • Timing alinement at TDC.JPG
    Timing alinement at TDC.JPG
    283.6 KB · Views: 310
The notch on the cam is on the left side, on the cam itself. The dot or punch mark is on the right side of the sprocket out next to the teeth.
You can try resetting the cam chain one tooth forward or reward on the sprocket. The teeth are 10 degrees apart. So resetting the cam chain moves the cam 10 degrees. You may not get it exactly right.
Check the position with the adjuster installed and properly tensioned. Adding spacers on the 8 big headstuds and torquing the nuts to around 15 ft/lbs will help align the marks.
Leo
 
Leo, you might be aware of this, but the reader might not be. 1 tooth on the 36-tooth sprocket is 10* of camshaft rotation, yes. But the camshaft turns at 1/2 crankshaft speed, so 1 tooth at the camshaft sprocket is 20* at the crank, which is where timing of both ignition and valves is measured.
 
Yes, I'm aware of that. I also agree with it to a certian extent.
When installing a cam, if all the parts are the same as stock then the marks will line up ok. Non stock parts can and will alter the way the marks line up. So unless you time the cam with a degree wheel and dial indicator it won't be exact. Unless you move the sprocket on the cam.
Most people are not after that kind of precision. Pulling a cam sprocket off and putting it back on 2 degrees different isn't the easiest process.
Getting the cam within about 2-4 degrees and the bike will run ok.
Maybe not as perfect as it could but very close.
Now on a more performance engine the extra work of checking the cam timing can give a stronger running engine. Also altering the cam timing can move the power up or down the rpms. All this is more advanced than most people have the skills or tools to perform.
Leo
 
Right, Leo, a few degrees of error on a stock camshaft isn't a problem, but if the camshaft is visibly off the mark you may very well have more than that. The history is that 15 years ago the motor was rebuilt by a PO, so the sprocket may have been tampered with--not a strong possibility to be sure, but we see some strange stuff.
 
That's a good point, po's do strange things.
Checking to see if the sprocket is lined up on the cam shouldn't be too hard. If the dot on the sprocket is 90 degrees from the notch on the cam shouldn't be to hard to see. Set the cam on the head, use a string or straight edge to line the notch straight up. The dot should line up on the sealing surface.
With the notch cut dead center with the string and the head sealing surface cutting the dot dead center the sprocket has to be pretty close to right.
Leo
 
We all complain and love to hate these P.O.s (previous owners). I think it's about time we 'fess up and admit there's a whole new generation of I.C.O.s (IDIOT CURRENT OWNERS) we should be directing some of our ire towards, lol. My God, just throw the poor bike in a hole and bury it for crying out loud, instead of abusing and torturing the shit out of it, lol. I think we need a run of t-shirts with a 650 motor and "Just Shoot Me" written underneath.
 
Thank you all for the quick responses, it's nice to know this forum exists and the people are all of great help. I checked the sprocket again last night to make sure I didn't miss the punch mark and sure enough there is no such mark. I know it is usually there, but in this case it is not. And yes I did check the right side originally and again last night. I do believe the head gasket might be the culprit. As I have said previously, the vertical mark is really only advanced a degree or two so the extra gasket thickness could account for that. Since the cam sprocket is fixed on the shaft and I can't move it nor am I willing to have the engine machined to correct. My question is should I leave the sprocket slightly advanced as it is now or is retarded better? I didn't put the head on yet and tighten the bolts but I am assuming this will improve the marks position even more. And will the new chain stretch improve it yet again? I will post pics tonight, not only to prove there is no punch mark , but so u can see how little it is out prior to tightening. Maybe I'm being too critical , but I like to get things right. This isn't government work after all, I love this bike.
 
Here are two pictures of a Web cam 59A that is a slightly modified stock cam said to give better mid range.
First one is the left side view showing the notch.
Second is the right side view showing the punch mark at the 9:00 position and the pin hole in the near or right end for the advance unit.
If yours doesn't have the punch mark, it could be an issue as to proper timing of the gear to the cam.
Hope this helps.

PS: for sale for $50.00 + shipping
 

Attachments

  • IMG_1696.jpg
    IMG_1696.jpg
    136.8 KB · Views: 263
  • IMG_1700.jpg
    IMG_1700.jpg
    205.6 KB · Views: 247
Yama, if the punch mark isn't present you don't have an original sprocket, so the timing notch may not be telling you the truth. Also, remember what I said--any error at the cam is doubled at the crank, and there is no way humanly possible that you're going to eyeball one or two degrees.

If you're going to have error, it's better on these motors to retard the cam timing slightly. But you won't really know where you are without a degree wheel, accurate TDC location, and a dial indicator.
 
Amen....

We all complain and love to hate these P.O.s (previous owners). I think it's about time we 'fess up and admit there's a whole new generation of I.C.O.s (IDIOT CURRENT OWNERS) we should be directing some of our ire towards, lol. My God, just throw the poor bike in a hole and bury it for crying out loud, instead of abusing and torturing the shit out of it, lol. I think we need a run of t-shirts with a 650 motor and "Just Shoot Me" written underneath.
 
Griz, I apologize, I was wrong there is a punch mark after all. Did a little more work this afternoon and when I ran my finger over the right side some dirt fell out of the mark and there it was, perfect spot for a metal flake. I moved the cam sprocket back a link just to see if it was any better. If I can post pics maybe everyone can better see my predicament. Also, it is a 447 cam consistent with a 75. I hate being stuck because of such an irritating little thing, but it effects such an important thing.
 

Attachments

  • image.jpg
    image.jpg
    210.9 KB · Views: 242
Back
Top