Timing Question

[diablo250]

I started my valve adjustment today and saw no sign of a 2T mark through the inspection hole. I did see a smudge of paint which I assume is the timing mark. I looked down the right cylinder and it was at the top of the stroke.
Anyway, everything is pretty much complete, but I have a couple of issues:
I have all my new shims installed, the buckets in, and the cam caps all tightened-but not torqued yet. The lines marked IN and EX on the cam sprockets are flat with the cylinder head, and I have two small paint dots on the sprockets lined up next to each other in the middle. I haven't counted the chain links yet. If something is wrong, can I diagnose it manually before actually cranking the engine with the starter, or is it just crank quickly and hope it doesn't go bang? What happens if my timing mark is off on the crank but the cams are timed correctly in relation to one another?

[Momaru]

AFAIK, if you've got the cams, chain (right # of links between) and pistons aligned properly, you *should* be good to go (those are the three things I checked and haven't had issues the two times I've done valves on mine). You could turn the engine over via socket to the crankshaft, with the plugs loose/out (make sure the tensioner is installed), before buttoning up to see that everything's moving properly, but I don't know how diagnostic it'll be. I would recommend double- and triple-checking your new valve measurements once the caps are re-torqued, as well as the chain links and cam sprocket alignment with the cylinder head. Lots easier to check things that are done to ensure they're done right before they're covered up. Also suggest putting the spark plug gaskets on the head instead of the cover, as Vex suggested in the DIY... found out the hard way why you should do that.

The engraved 2T mark should be immediately inboard (towards the clutch) of the white paint dot on the flywheel. Mine was just about impossible to see as the metal 'tooth' hanging down from the inspection port obscured it and it was hard to angle the light right to illuminate the engraving. There was also a 1T mark that was equally hard to see.

I'm no pro, but in theory if your cams are synched with one another but off from the piston, your whole compression-firing-exhaust sequence will be off. If it's close (within a couple degrees of rotation), you may not notice it. If it's far out of synch I'm pretty sure you'll know it almost immediately once you crank up, if it starts at all. I'm not 100% on this whole paragraph, but that's the way it seems to work, having taken the whole shebang apart (and successfully reassembled).

[diablo250]

My cams are each oriented 180 degrees from the ones pictured here. My small dots are lined up on the inside, and the bigger ones are outside. Is this correct, or am I 180* off? How do I know when I'm on the compression or exhaust stroke since the timing cover mark passes twice?

[Momaru]

180* from that pic looks about right to me. Here's a shot of my cam orientation from the last valve job I did before putting in the tensioner. The lines with dots are level with the cylinder head

DSC04934.jpg

Also, if you haven't seen it, here's a link to Vex's DIY on valve adjustments, and another one to valve adjustments written by long-time ninjette owner and new member to the forum, 'Doc'.

That said, do you have the factory service manual? If so, there's a picture of the cam alignment on reassembly at 2T(top of pg 5-18) that has always worked for me. If you don't have an FSM, shoot me a PM.

As trivia, if you left the cams aligned as they are in the pic you provided, you'd be right on for 1T, if you wanted to do it that way instead.


As for whether on the intake or exhaust stroke with the camshaft, consensus (or at least past posters and my experience) say it doesn't matter. Our bikes (supposedly) work on a 'wasted spark' method where both plugs fire every time, whether the piston just compressed or exhausted. True gurus please correct me if this is wrong, but if it is, someone else needs correcting too. (Ref: previously discussed in posts 25-29, Vex's Valve adjustment DIY linked above)

[Momaru]

Hope this helps, I'm off to get 4 hours of sleep before work. Will check back when I wake up.

[Momaru]

But before I go...

Here's a pic of the 2T mark, circled in red. It's bloody near invisible, but I promise it's there in the pic (which will enlarge if you click on it). Have a lot of people reporting it's not there, but mine was just a PitA to see. Wondering if mine is 'standard' and people aren't looking hard enough or if there was a batch (or maybe a bunch of them) that didn't have the piston timing marks on the alternator (which I just discovered is actually a stator and the metal disc you see through the sight-hole with the timing marks on it is the rotor). Mind letting me know if yours is indeed missing or just hard to find? Thanks!


DSC04795a.jpg

[diablo250]

Thanks for all the great advice Paul. I slept on it last night, then this morning cross checked, double checked, triple checked, quadruple checked all my measurements and specs. The bike started on the first try

[diablo250]

It seems that the engine doesn't make it to the 11k mark quite as fast right now...my roommate says that it's getting warm here in socal so I may need to jet leaner. Is this the case that other riders have had in warm weather? I rode for 20 miles keeping revs under 8k and then gradually spooled up the engine. If I happened to be off by 1 tooth on the crank would the bike feel amost right, or would it just die altogether?

[Momaru]

Makes sense. As the temp rises, density drops and thus O2 content in the air drops a bit. Hence there's less O2 in the same volume of air your engine is getting, which leads to a slightly richer combustion mix. Leaner jetting might help a bit with that.

I'm honestly not sure on being one tooth off. There's supposedly a fine balance between the piston motion and valve motion, but I've never messed with adjusting that, sorry. My guess would be that the bike would feel 'close but not quite right' in the event of being a tooth or two off. My cam chain tensioner was loose for a while, which can cause (amongst other things) skipping of teeth, effectively de-synching the pistons and valves. My impression was that it's certainly not good, but not catastrophic. Again, open to correction by anyone that knows better.