One Dakota.... XS1 fix, restore labor of love SoDak

[NP2650]

I'm sure everyone has had one of those days in the shop. Started on re-assembly of the top end. Using Jim's excellent step by step thread in the Tech section so I don't forget any thing. Got the pistons in the cylinders, cylinders down on the studs, and pins set in the rods.

I then lowered the cylinders down onto the top of the case. It didn't go down quite all the way to sit flat on the gasket. I figured it was just hung up a bit on the alignment dowels, so I gave it a couple of taps with the rubber hammer. No go. Hmmmm. Seems to be rocking a bit front to back. Looked down between the cylinders and damn. The top of the center cam chain guide, which is essentially an aluminum block, is hitting a protruding ridge on the side of the cylinder casting, preventing the cylinders from setting down all the way. I pulled out the old guide that I replaced and sure enough there was a gouge in the top in that same location. Maybe Yamaha didn't notice the interference and just torqued it down. I didn't want to take the chance of either damaging something or it not sealing well at the bottom. So, everything came back apart. I removed metal with a die grinder a bit at a time, and kept checking until I had sufficient clearance and the cylinders sat down fully on the gasket.

Then back to where I started. Nothing like having to assemble the pistons and cylinders twice in one day. I guess practice makes perfect.

 

[NP2650]

Second mystery of the day. Re-installed the cylinder head and went to install the cam. OK, so notch goes on the left of the engine and punch mark on the right. Wait, where's the punch mark? There's no marks at all on the right side. Then I notice that the notch and punch mark are both on the same side! I did verify that the notch is on the correct side, so I installed the cam with the notch and punch mark on the left. I guess it really doesn't matter which side the punch mark is on. Just another early bike oddity.

 

[NP2650]

Made a bit more progress. Got the top end buttoned up. Set the valve lash today, will bench set point gap and timing tomorrow. I haven't mentioned this before, but top end was off sometime in the past; one of the head bolt holes in the cylinders has a helicoil in it. Everything else inside looked pretty good. Just ordered some new case cover bolts on Amazon. I want to get the right cover in place, add some oil, and spin it a few times to make sure oil is getting to the top end. Yeah, got to install the oil feed tube as well. Darned if I could find the copper washer, so new one is coming tomorrow as well.

 

[NP2650]

Houston, we have a problem. I set the point gap, then went to bench set the timing using my ohm meter. For the right side points, if I turn the points plate totally clockwise, I can still only get the points to open at TDC. Can't get them back to the correct retarded position.

Did I somehow get the cam one tooth off? I followed Jim's excellent Top End build up thread. One thing I did notice is that the cam chain was fairly loose (it was new and I checked the link count). I'm wondering if when I installed the cam tensioner later, it tightened the chain enough to move the cam out of alignment. Though moving it a whole tooth off seems like a lot. What am I missing? Any ideas would be appreciated.

 

[Its been a long time]

@NP2650 I had a similar issue. Here's a post about a very simple way to check camshaft timing. If you're one tooth out, it's very obvious on this check.

https://www.xs650.com/threads/camsh...ed-one-crankshaft-tooth-out.66347/post-838935

 

[NP2650]

I don't have a degree wheel, so can't do that check right away. In that thread, however, 5twins suggests looking at the pin on the advance end of the cam. With the engine at TDC, that pin is aligned straight up. I'm assuming that's correct(?)

 

[Jim]

I followed Jim's excellent Top End build up thread. One thing I did notice is that the cam chain was fairly loose (it was new and I checked the link count). I'm wondering if when I installed the cam tensioner later, it tightened the chain enough to move the cam out of alignment.

Thanks...
Highly unlikely the tensioner moved it a tooth or so. Try this...

Set the timing plate so it's centered, then take the right points and adjust the gap until it fires at the timing mark. Then turn the crank until the points are at the widest gap, measure that and let us know what it is.

 

[Its been a long time]

I don't have a degree wheel, so can't do that check right away. In that thread, however, 5twins suggests looking at the pin on the advance end of the cam. With the engine at TDC, that pin is aligned straight up. I'm assuming that's correct(?)

You don't need a degree wheel. Use the advanced timing mark like I suggested.

For sure you can do as 5T suggests should you choose.

 

[Jim]

Looking at that, I'm about 99% confident you got the cam timed correctly. That's about as confident you can get without actually being there.

 

[Jim]

 

[NP2650]

ires at the timing mark. Then turn the crank until the points are at the widest gap, measure that and let us know what it is.

.021

 

[NP2650]

You don't need a degree wheel. Use the advanced timing mark like I suggested.

This is an early bike, so is it 36 degrees or 47 degrees for valve opening? Trying to track that down in the manuals I have.

Just found it 47 degrees, so would be hard to use the advanced timing mark as a reference. Thanks for a great suggestion though.

 

[Jim]

.021

Cool. That's a little wider than the book calls for (.016")... but it'll work just fine like that. Or, you could close it down slightly and readjust the timing plate. Just keep going back and forth 'till you find a happy medium before you run out of timing plate adjustment

A wider points gap will shorten the dwell on the coil ever so slightly.... 10-15° or so. Unless you plan on running that engine at redline most of the time (racing), you'll never know it.

Other than that, you'll never know your gap's a little too big.

 

[Jim]

'K.... disregard what I just said about dwell... I'm backwards.
A wider gap will increase the dwell slightly. Not by much though. I still wouldn't be afraid to run a slightly big gap on the points.

Not sure where my heads at today. Bigger gap means it opens earlier and closes later... thereby shortening the time the coil charges.... less dwell. Right the first time... fuck me....

 

[Jim]

Also, have you checked the advance mechanism to make sure it snaps back to full retard?

 

[NP2650]

Thanks for all the tips and support guys. Advance mechanism is working as it should. I think I'll play with the point gap a bit and see what works best.

 

[Jim]

Btw, I corrected myself, yet again in #194 above. A bigger gap will shorten the dwell. I was right the first time, then some idiot got inside my head.
Must not second guess myself quiet so much.

 

[NP2650]

Update. I was able to set the points gap at .016, the upper end, and get the timing set correctly for both cylinders.