Sight window or cam markings

[tlartist]

Need something clarified by the group. I have been going by the cam marking more than the site window when doing valve adjustments. I was at a tech stoc where it seemed the cam markings were maybe just a half link off from the tdc in the window. So which do you go by and does this even make a difference?

 

[Scooter]

Re: Site window or cam markings

My last valve check I simply lined up the cam markers and didn't bother with making sure the TDC pointer was exactly lined up. Didn't measure any significant differences doing it this way than the previous measurement 19K miles previous when I did it by the book.

Anal types might disagree...

I think the next time I'm in there I'm going to measure one valve and then see how far I can rotate the crank before the measurement changes by .001". (Don't hold your breath waiting for this since I don't plan on going back in there again until next year)

 

[GitSum]

Re: Site window or cam markings

It doesn't make a difference - Personally, I prefer the index lines on the cam sprockets because they are easier to see.

You are actually measuring the clearances between the "heel" of the cam and the valve lifter. The heel, (technically called the base circle), is the lowest point on the cam and as you can see by this drawing, is quite a large area:

To put it into perspective, here is a pic of the #1 cylinder of my ST1300 brought up to Top Dead Center in preparation to measure the clearances. Note the location of the lobe on the intake and exhaust cams

 

[dduelin]

Re: Site window or cam markings

Both. I use a little mirror but of course I'm sure you do too.

 

[tlartist]

Re: Site window or cam markings

Thanks for the info. I will check next time as well to see if the difference matters. I was just going by the lines before because as others stated they are just easier to see. Just wanted to make sure I was doing it ok.
Posted via Mobile Device

 

[Pete in PA]

Re: Site window or cam markings

I've never used ANY marks. Put bike on center stand in top gear, rotate engine with rear wheel until high spot on cam lobe points away from the valves I'm going to check. Now if I'm Removing cams I use all the marks.

 

[old fard]

GitSum and Pete in PA are right. The base circle of a camshaft lobe that is properly ground leaves considerable leeway on either side of your checking point. As long as the point of the lobe is pointing between 11:00 and 1:00 relative to the bucket you are fine. I would bet that there is little base circle runout on the Honda camshaft.

 

[tlartist]

There sure are some smart people on this site! Thanks folks.

 

[Byron]

Here is something else to consider. The timing mark inside the engine is being driven by the timing chain and over time chains stretch. The timing marks on the cam sprockets are fixed and will not deviate there position in relation to the edge of the head. If I'm just checking clearance then I use the cam sprocket marks for the reason they are easier to see and use. If I need to make an adjustment then I make sure the inner timing mark is aligned before disassembly/assembly.

I may have missed it but I've not seen a note about when the timing chains are supposed to be replaced. I've also noticed slight differences in timing mark and cam sprocket marks but there is usually nothing you can do when they are only 1/2 tooth or less off.