One Tooth Off?

[Calev]

Attached is a photo of the right side advancer pin while my engine is at TDC. from what I've read it looks like I am off by one tooth... darn
I've been having trouble with timing and want to check my cam chain timing before chasing other things.

Is it possible to remove the rocker cover without removing the engine from the frame? That's probably that toughest thing to do to remedy this timing. I know once the cover is off I can slip the bearing off and fix my mistake.

Thanks!

 

[Jim]

No, you can't pull the rocker box with the engine in-situ.
Is that a new cam chain in there?
Here's a pic of what one tooth off looks like. Not from the outside like you're looking at, but you can compare it to what yours looks like.
Fwiw, looks to me like a stretched cam chain.

 

[Calev]

Hi Jim, I did a top end rebuild and it has a new chain + modified cam chain guide.

I saw that photo but was didn't know if the 10deg was from red line to redline (Yellow arc) or green line to red line (Orange arc). Attached edited photo

 

[Jim]

The three lines are superimposed over the sprocket teeth which you cant see. So each line is one tooth or 10° at the cam. Red to green is 10°. Red to red would be a total of 20° (at the cam). The green is showing the correct timing, red is 10° either side of correct.

 

[Jim]

Do me a favor? Far as I know, I'm the only one running the modified chain guide, although I've sent out enough HiLoks for prolly a dozen of 'em. After you get some miles on the guide, give a status report on my mod thread you linked to above?

Guess I should prolly do that too huh?

 

[Signal]

Was fitting a head today and used the cam seal carriers to centre the cam. By chance when on the left I looked through the top screw hole in the cam seal carrier and noticed the the notch in the cam sprocket boss aligned with the top hole screw hole in the carrier with the pistons at TDC.
Not much use to you now when the top is on but another easy check to do before refitting the rocker cover.

 

[Its been a long time]

I think before doing anything more radical, a check of the inlet valve timing is worth doing. Need a dial gauge, remove an inlet valve tappet cover and the alternator cover. Takes just a few minutes to validate camshaft timing is correct or not. It's quite obvious on the fully advanced timing mark if the camshaft is timed correctly or not. I did it on mine and it was really simple to do. There's a procedure detailed in the shop manual.

 

[Wingedwheel]

Been there, done that but fortunately I caught it before the engine went in. It’s not a difficult fix but the engine has to come out. I will agree that unless the tensioner is set it could be off.

 

[Calev]

Thanks for all the responses.

Jim, I'll keep you updated about the modified guide. Embarrassed I didn't connect the dots on who the OP was the guide.

I am getting ahold of a dial indicator that will suffice. When I acquire one, I will report back. Again, thanks to everyone who responded.

Cheers

 

[Calev]

Alright, finally had some time to figure things out last night. I used this page for reference.

I found TDC on the compression stroke with the dial indicator and installed the degree wheel with a pointer at 0°. Then I moved the indicator to the intake valve and zeroed the indicator. I rotated the engine counterclockwise until I was back on a compression stroke. I watch the indicator until it moved approx. 0.002". My reading on the degree wheel was about 16° before TDC. From the reference intake valve should be opening at 36°. So, my guess was right, I am two teeth off. I double checked my readings, and it was a pretty consistent 16° BTDC.

I'm guessing when I had the engine on the table, I had bumped the pistons slightly down when installing the head. When I went to check the timing marks on the cam, the crankshaft did not have the rotor and made it was hard to tell if it had moved.

I am going to employ this trick to see if I correct this before removing the engine from the frame. But before I do, I am going to triple check the timing one last time for good measure.

 

[5twins]

I don't think that will work with a new, tight chain.

 

[Calev]

I actually had very good success last night, but with a different method.

With the engine on the bike, my plan was to get the rocker cover loose and remove the left side cam shaft bearings to get enough slack and then jump timing. I also removed the cam chain tension to give me even more slack.

With the rocker cover loose and I inserted a steel rod with the same diameter as the advancer rod into the cam shaft. Pulling/pushing up on the steel rod lifts the cam shaft bearings off the head just enough for to slide them out. Once the bearings are out, I carefully let the cam shaft sit on the head. I now have enough slack to jump the chain. I jump the chain and reinstall a single bearing in the same manner. Pulling/pushing up on the steel rod and then sliding the bearing on the cam shaft where it sits in the head.

I triple check the timing mark on the cam shaft sprocket, the dowel pin on the advancer side, and the keyway on the points side at TDC. Everything lines up and I reinstall the second bearing in a similar fashion. I snug down the rock cover with new gasket sealer and check timing with a degree wheel/indicator before torquing. This time the intake valve opens at 36°, perfect.

I stopped after this as it was late but will be finishing reassembling the head this evening.

All in all, this took me about an hour to do.

 

[Gowron650]

I actually had very good success last night, but with a different method.

With the engine on the bike, my plan was to get the rocker cover loose and remove the left side cam shaft bearings to get enough slack and then jump timing. I also removed the cam chain tension to give me even more slack.

With the rocker cover loose and I inserted a steel rod with the same diameter as the advancer rod into the cam shaft. Pulling/pushing up on the steel rod lifts the cam shaft bearings off the head just enough for to slide them out. Once the bearings are out, I carefully let the cam shaft sit on the head. I now have enough slack to jump the chain. I jump the chain and reinstall a single bearing in the same manner. Pulling/pushing up on the steel rod and then sliding the bearing on the cam shaft where it sits in the head.

I triple check the timing mark on the cam shaft sprocket, the dowel pin on the advancer side, and the keyway on the points side at TDC. Everything lines up and I reinstall the second bearing in a similar fashion. I snug down the rock cover with new gasket sealer and check timing with a degree wheel/indicator before torquing. This time the intake valve opens at 36°, perfect.

I stopped after this as it was late but will be finishing reassembling the head this evening.

All in all, this took me about an hour to do.

I think I'm in the same position with my bike. I just reassembled an 83 XS650 Heritage Special and it looks like the timing chain is one tooth off at TDC. I am wondering if I followed your method, would I be able to get enough slack with a new timing chain? Was your chain new?

Also, will this compromise the seal on the rocker cover? I had cleaned the surfaces and applied yamabond.

 

[Its been a long time]

I think I'm in the same position with my bike. I just reassembled an 83 XS650 Heritage Special and it looks like the timing chain is one tooth off at TDC. I am wondering if I followed your method, would I be able to get enough slack with a new timing chain? Was your chain new?

Also, will this compromise the seal on the rocker cover? I had cleaned the surfaces and applied yamabond.

Looking at that picture before doing much else, I think I would double check that the TDC mark is set correctly.

 

[Gowron650]

Looking at that picture before doing much else, I think I would double check that the TDC mark is set correctly.

Okay thank you. Would I do that using a dial gauge as you described above?

I also took off the camshaft end covers and see that the hole (which I think is for the advance rod dowel pin on earlier models) is slightly off from vertical.

 

[Jim]

Also, will this compromise the seal on the rocker cover? I had cleaned the surfaces and applied yamabond.

I'm curious, if you have the rocker box cover on, what are you referencing timing to in relation to the cam?
You look to be about 3-5° on the retard side of TDC. One tooth off at the cam (10°) will have you off about 20° at the crank. 36 tooth cam and 18 tooth crank sprockets.
So putting the cam timing mark correctly will have you off considerably more than your showing in your pic.

So how are you referencing the cam timing marks?

 

[Its been a long time]

Okay thank you. Would I do that using a dial gauge as you described above?

I also took off the camshaft end covers and see that the hole (which I think is for the advance rod dowel pin on earlier models) is slightly off from vertical.

I was checking inlet valve opening as a check on camshaft timing. Indirectly, by checking valve timing is correct then, yes that checks TDC.

But in your picture the timing marks don't look so far out to be timed incorrectly. I am sceptical that you have an issue with camshaft timing. I believe the TDC indicator might need adjusting. Hence me suggesting that you check and if required reset the TDC mark.

Yes, you can do it with a dial gauge but there's other methods too. You can check TDC down the spark plug hole. If you're not 100% certain how to check TDC I suggest a search, there's lots of information out there.

 

[Gowron650]

I'm curious, if you have the rocker box cover on, what are you referencing timing to in relation to the cam?
You look to be about 3-5° on the retard side of TDC. One tooth off at the cam (10°) will have you off about 20° at the crank. 36 tooth cam and 18 tooth crank sprockets.
So putting the cam timing mark correctly will have you off considerably more than your showing in your pic.

So how are you referencing the cam timing marks?

Thanks Jim. Sorry if I'm showing my ignorance here. This rebuild project is a first for me.

You're right, I don't have a view of the cam timing marks. After noticing that the timing looked off on the alternator, I took off the camshaft end covers and saw that the hole (which I think is for the advance rod dowel pin on earlier models) appears to be slightly off from vertical when at TDC. Does that hole line up with the TDC mark on the cam sprocket? It would be a huge relief to hear that the timing is not off at the cam shaft.

 

[Jim]

Take your rotor and set it at TDC... the line to the right of the "T" stamp. Then take a pic of the hole in the cam... preferably with a pin in it, but at the least a nice clear pic of where it's at in relation to vertical.
...and another pic of the rotor once it's reset.

Fwiw, the faded white paint on the TDC pointer screw is a witness mark the factory put on it after they verified correct position. Possible it's off, but unlikely.

 

[Jim]

And as was pointed out above, you can check TDC through the plug hole. Put a zip tie (or similar) down the hole and let the piston push it up to TDC. rock the rotor back and forth numerous times and you'll get a feel for where the piston stops. That's your TDC.

*** use a long zip tie... one that won't lose itself down the hole.***