Mechanical Timing

[Crossrodes]

OK I did the static timing but....I fully retarded the timing and found that the flywheel was half way between the full advance point and the idle timing point when the points opened.  I think I know why.

When I had the engine apart and replaced the timing chain I marked the crankshaft sprocket as advised in the Clymer manual.  However the mark was rubbed off over time (next time I'll scribe it on).  I took a guess as to the sprockets positioning, installed the chain and checked for any piston/valve interference...there was none.  I thought I was home free.  Now I'm guessing I wasn't.  So I'm thinking I will probably have to take things apart again to line up the sprockets. and re-install the chain.  I have a couple of questions....

1. In searching the message board it seems like there are marks on both sprockets used to line them up...I could only find a mark on one.  Does anyone know for sure there are marks on both sprockets on a '79?

2. The Clymer manual indicates that you have to remove the engine to change the chain.  Has anyone here ever changed the chain with the engine in the bike?  If so how difficult a job was it with the engine in the frame?

[Bob_Roller]

There are two marks, one is extremely difficult to see, if I'm not mistaken, it is the sprocket on the crankshaft, the bearing covers up a majority of the mark, I last did this 12 years ago, so my memory of the procedure may be off a bit .

You can remove the chain with the engine installed, you just have to remove the exhaust system if you have a crossover pipe at the front of the engine .

[montmil]

Mike,

I have a photo essay on timing chain replacement in the Photo Gallery that may be of some help.

http://www.suraklyn.com/r65_forum_gallery/thumbnails.php?album=35

Yes, the OEM timing "scratch mark" on the crankshaft sprocket is hidden by the crankshaft outrigger bearing. Grrr...

I made the error of not clearly marking the crank sprocket tooth with the cam sprocket's dimple before pulling the timing chain. I was anxious about getting the crank and cam gears aligned during the chain refit.
   I ended up pulling the valve covers -spark plugs out- so I could watch the rocker arms as I rotated the cam. I positioned the left side rockers at TDC and noted the cam gear's dimple was at the 12 o'clock position. The crank was then rotated to position by watching the flywheel marks line up in the timing window. This put the correct crank sprocket tooth at 6 o'clock; right on top of the cam sprocket dimple.

Even a blind hog finds an acorn now and then.

A slow hand-rotation of the engine revealed no interference. Multiple rotations all checked out. I cleaned the crank sprocket tooth and painted it white... at least it was white when I buttoned up the engine.

Next time I'm in there, I'll confirm the proper crank tooth before removing the chain.

Hope the photos are helpful.

Monte

[Crossrodes]

Thanks Bob and Monte.  Monte, looking at your list of bikes I'm guessing that this was your '81 that you worked on and Bob's was his '82.  I don't know if the '79 will have the same mark on the sprocket that yours have.  I'll check when I take it apart (waiting to borrow the alternator tool from a friend).  If it doesn't have the mark or I can't see it (I did look the first time) I'll follow the same procedure you did Monte.  Here's hoping....

[montmil]

I'd guess that there will be some type of identifying marks on the sprockets, no matter the vintage.  

Monte

[Bob_Roller]

At best, there is about 1mm of the mark showing from under the bearing .

It's quite easy to miss it .

[Crossrodes]

OK so I have the timing gears/chain exposed and I've checked the piston/valve timing visually.  Other than the fact that when my cam gear dimple is at 12 o'clock that my LEFT side piston is at TDC everything seems to be OK.  I don't think it matters which piston is at TDC when the dimple is at 12 o'clock since both cylinders fire each time the points open.  Now while the piston/valves SEEM to be at TDC I'm not convinced they are sooo...

I took a quick look at the crank sprocket and I believe there are 20 teeth on it.  So if I should retard the timing by moving the crank back by one tooth on the chain I will be retarding it by 18 degrees.   The question I have now is how many degrees does the ignition advance when fully advanced.  I looked it up and can't find it.  I think I remember 44 degrees but I could be wrong.  So does anyone know?  (my static timing check showed that my crank was about half way to the fully advanced point when it was supposed to me at the idle mark).

As I said before I don't seem to have any piston/valve interference and I'm guessing that I won't have any interference if I retard by 18 degrees.  If I do then something is wrong and I'll have to go back to square one.

Oh, Bob I got out a magnifying glass to see if I could find that timing mark on the crank sprocket and I just don't see it....maybe I don't have one or it is fully covered by the bearing.

[montmil]

As ya can't modify a post that has had add'l posts added to the thread, I need to correct the following statement:

Prior post had an error:
"I ended up pulling the valve covers -spark plugs out- so I could watch the rocker arms as I rotated the cam. I positioned the right side rockers at TDC and noted the cam gear's dimple was at the 12 o'clock position."

Should be LEFT side rockers. Left. Not beer hand. Left hand.

Monte

[Rob Valdez 79 R65]

As ya can't modify a post that has had add'l posts added to the thread, I need to correct the following statement:

Prior post had an error:
"I ended up pulling the valve covers -spark plugs out- so I could watch the rocker arms as I rotated the cam. I positioned the right side rockers at TDC and noted the cam gear's dimple was at the 12 o'clock position."

Should be LEFT side rockers. Left. Not beer hand. Left hand.

Monte

There ya go.

[Darwin_R65]

Left. Not beer hand. Left hand.  

I have a drinking problem 2 hands and only one mouth.

[Semper Gumby]

Did this years ago engine on the bike.  The information that is no where in print (came from Nathan at Boxerworks after a direct question) that the fixed block on the LH side looking aft should be set so to deflect the timing chain 1 mm.

The marks are there.  Hard to see.  

Good luck.