Finding TDC?

[Schoolbusbob]

I'm planning on upgrading the stock cam chain tensioner to an APE fixed unit. It has been ordered but after seeing some of the installation videos I'm thinking the engine might need to be at T.D.C. to install.
Question: Does any one know where to find the timing marks? I don't want to pull the spark plugs.
THANKS, BobL.

[antonn]

r/h engine cover, remove inspection plug and turn motor over to align the two dots, tdc

[markjenn]

Originally Posted by antonn

r/h engine cover, remove inspection plug and turn motor over to align the two dots, tdc

A picture might help you out.



BTW, when you say "get motor to TDC" on a 4-cyl bike, keep in mind that all the pistons aren't at TDC simultaneously. On a conventional-crank (non-crossplane) inline-four like the S1000RR, the 1-4 pistons are at TDC when the 2-3 pistons are at BDC and vice-versa. The marks above, when they are aligned, put the 1-4 pistons at TDC.

It also may matter which TDC you're talking about - the TDC between the compression and power stroke when both valves are closed or the TDC between the exhaust and intake strokes where the exhaust valve is just closing the the intake valve is opening. For valve clearance checks, you want the first TDC, not the second.

I honestly don't know whether when you align these marks on the S1000RR whether this determines which TDC on 1-4 you're at, but I doubt it matters anyway. I bet it will all be very clear when you get the part.

- Mark

[bananaman]

Getting tdc with plugs in may be difficult with compression?

[MasterTommy NL]

TDC doesn't matter.

What matters is that you remove your valve train cover so you can check the engine timing after swapping the cam chain tensioner out. Modern supersports like these have very agressive cam lobes. Which sometimes results the cam chain skipping one or more teeth on the camshaft sprocket if the chain is untensioned (by removing the tensioner). Combine that with the fact that if the chain jumps 2 or more teeth, the pistons hit the valves and you instantly f*ck up your valves if you even TRY to start it.

Please play it safe and check the engine timing BEFORE starting the engine. In my years in the BMW workshop i've seen at least 1 F800S engine and 1 S1000RR engine blown because of people who (against my advice) just swap out the cam chain tensioner like it's a set of brake pads.

Oh, and i also wonder why you would like to replace the cam chain tensioner? BMW doesn't use (except on the scooters) spring loaded tensioners like the japanese do, but hydraulic tensioners. And as opposed to spring loaded tensioners which tend to get noisy, hydraulic ones almost never fail.

[MasterTommy NL]

Originally Posted by bananaman

Getting tdc with plugs in may be difficult with compression?

It's possible if you turn the crank slowly. But that's not the main concern (see my first post). Just make sure you turn the crank clockwise.

[MasterTommy NL]

Originally Posted by markjenn

A picture might help you out.



BTW, when you say "get motor to TDC" on a 4-cyl bike, keep in mind that all the pistons aren't at TDC simultaneously. On a conventional-crank (non-crossplane) inline-four like the S1000RR, the 1-4 pistons are at TDC when the 2-3 pistons are at BDC and vice-versa. The marks above, when they are aligned, put the 1-4 pistons at TDC.

It also may matter which TDC you're talking about - the TDC between the compression and power stroke when both valves are closed or the TDC between the exhaust and intake strokes where the exhaust valve is just closing the the intake valve is opening. For valve clearance checks, you want the first TDC, not the second.

I honestly don't know whether when you align these marks on the S1000RR whether this determines which TDC on 1-4 you're at, but I doubt it matters anyway. I bet it will all be very clear when you get the part.

- Mark

True!

However, the markings on the set of gears you see in the repair manual image only line up once every 6 crankshaft revolutions (or once every 3 camshaft revolutions). The small gear change is made there so they could keep the camshaft gears small to reduce stress and wear, and because the gearing on that marked set is uneven this also means it reduces wear. By making the gear ratio uneven, the cam chain doesnt hit the same teeth on the sprockets every # of revolutions, which makes the whole thing wear more evenly.

[markjenn]

Originally Posted by MasterTommy NL

However, the markings on the set of gears you see in the repair manual image only line up once every 6 crankshaft revolutions (or once every 3 camshaft revolutions). The small gear change is made there so they could keep the camshaft gears small to reduce stress and wear, and because the gearing on that marked set is uneven this also means it reduces wear. By making the gear ratio uneven, the cam chain doesnt hit the same teeth on the sprockets every # of revolutions, which makes the whole thing wear more evenly.

Thanks for clarification. I was reading the shop manual process for valve clearance checks and noticed that they said only to line up the marks and then check #1 without the normal check one makes to see if the valves are both closed so you have the right TDC. I thought that meant that those index marks only line up when 1 is TDC between compression and power. Very clever.

While we have the experts in this thread, what are we seeing with respect to cam chain wear and clearances at that first 18K check?

Normally, I like doing valve clearance checks myself, but there are a couple of special fixtures and this is the first motor I've worked on which has a check for valve timing. So I'm thinking of just leaving it to the dealer. (I tend to be mistrustful of whether dealers actually do the work given that a "clearances are fine" clean bill of health is essentially unverifiable.)

- Mark

[MasterTommy NL]

Originally Posted by markjenn

Thanks for clarification. I was reading the shop manual process for valve clearance checks and noticed that they said only to line up the marks and then check #1 without the normal check one makes to see if the valves are both closed so you have the right TDC. I thought that meant that those index marks only line up when 1 is TDC between compression and power. Very clever.

While we have the experts in this thread, what are we seeing with respect to cam chain wear and clearances at that first 18K check?

Normally, I like doing valve clearance checks myself, but there are a couple of special fixtures and this is the first motor I've worked on which has a check for valve timing. So I'm thinking of just leaving it to the dealer. (I tend to be mistrustful of whether dealers actually do the work given that a "clearances are fine" clean bill of health is essentially unverifiable.)

- Mark

When you are checking the valve clearance, you need the little BMW special toolkit. It consists of the following:

- A small threaded pin which is used to fix the engine in TDC (cyl 1)

- A calibre with two sides. Side A is used to check the camshaft timing at the 18K service. When side A doesn't slide on de camshafts, side B is used to re-align the camshafts to fixed angles (i believe 1.6 degrees for the intake camshaft and 1.7 degrees for the exhaust camshaft).

- A substitute cam chain tensioner which needs to be fitted before you adjust the camshaft timing .

- A small round tool with a standard issue ratchet socket on the other side, which is used to rotate the camshafts along the sprocket.

- And finally, not included in the BMW kit, a torque wrench (or more like a torque screwdriver) with a range of 0-5 Nm. The substitute cam chain tensioner used during the adjustment of the camshaft timing needs to be torqued to exactly 1.2 Nm.

If you are performing the 18K service yourself, remember that besides checking the valve clearance, you also have to check the camshaft timing. If the camshaft timing is within spec, all you need is the threaded pin to block the crank in the prescribed position, and the calibre to check the timing. If the timing is out of spec, you need the whole set of tools.

Replacement of the timing chain (and the timing chain sprockets of course) is only necessary when the camshaft timing is out of spec, and also out of the adjustment range of the sprockets.

This job is doable, but don't spare money on the tools, you really need them to perform this job accurately. We are talking about .1 degrees here. Also, double check every step you make, and read every step in the manual twice before you proceed to the next step. The tech in this engine is about as precise as it gets. F*ck ups are easily made, and also easily avoidable.