timing troubles and identification help

[TwoManyXS1Bs]

Something else that doesn't look right, your cylinder honing job.

Studying the hone marks, and the vertical score lines, ask yourself "Which came first?" Looks to me like honing *over* the score lines. Like somebody honed over a previously scored cylinder.

And, not very well...

 

[kawabunga]

Upon closer inspection, the one cylinder and piston is not in good condition. Between the cam, rocker, piston/cylinder, it makes me wonder what went wrong in the bikes history. Possibly run low on oil?

Can anyone verify what size pistons I have? Are these stock size? I'm looking into getting new pistons and having the cylinders bored. Are the MikesXS pistons typically good quality? I need to know what size over to order.

This piston has a "3" and "964" stamped on it.

This piston appears to have a "1" and a "964" stamped on it. But I'm not positive, it's a little wonky.

And the bottom of the cylinder sleeves appear to have "016" on them.

Also, this is the state of my cam chain slider.

And, as 5twins pointed out, the cam chain slider was installed crooked. I measured it, the top was spaced 5mm left, 4mm right and the bottom was spaced 9mm left and 11mm right.

And the sump filter is torn.

 

[5twins]

Your pistons and bore look to be stock. The "1" and "3" numbers off to the side on your pistons aren't important. I'm not sure what they mean but you needn't be concerned with them. The important one is that 3 digit number in the center, the "964". That indicates your piston size was 74.964mm when new. The "016" stenciled on the sides of the cylinder sleeves indicates the bore size was 75.016mm when new. The new clearance spec for these is .050-.055mm. Subtract 74.964 from 75.016 and you get .052, right in the middle of the spec. That was the piston to cylinder clearance when new.

But, your clearance amount has obviously grown due to wear. You can measure, or have the parts measured, to determine their size and the amount of wear now, but if you're going to get it bored anyway, there's really no need. From the amount of scratching you've found, getting it bored is probably a good idea. Oversizes go in .25 or 1/4mm increments. Often that 1st size (+1/4mm) isn't enough to clean up the damage so you skip right over it up to a 2nd oversize (+.50mm). In fact, it's very common to do this to insure all wear and damage are removed and/or corrected.

There is a good source of cheap oversize piston kits on eBay now. Quite a few people around here have tried them and the quality is reported to be good. There is a substantial cost savings compared to Mike's. I mentioned how common it is to skip right up to 2nd oversize. This guy doesn't even sell the 1st oversize .....

https://www.ebay.com/itm/YAMAHA-XS6...S-1-/131956383746?vxp=mtr&hash=item1eb936a002

 

[kawabunga]

Thank you for the link, 5twins. I'm going to do some checking locally for cylinder boring.
This engine is turning out to be more in need of attention than I anticipated...
I really appreciate all the help and advice so far, thank you!

 

[5twins]

Well yes, just about all of these can use some topend "fixing", but some are worse than others. When I did mine, I was able to just re-ring it (along with a new cam chain and front guide of course). The pistons and bores were near the wear limit but I didn't want to spend the extra money for the parts and to have it bored. Back then, these cheap piston kits weren't available yet. I would have had to get the expensive ones from Mike's. So instead, I scored some cheap N.O.S. 1st over-size rings on eBay ($30 for 2 sets), filed the end gaps for minimum spec clearance, and went with that. I am ready to go back in and bore it now, but I got 10 years out of my "cheap" rebuild, so I'm OK with it.

The bike still runs great and has near perfect compression (145 to 150), but the head gasket is failing on me. I don't know if it's because of the aftermarket Athena gasket I used or if maybe it's just a normal 650 thing. This is the 1st and only one I've ever owned.

 

[motorbikerx]

How is it failing? Oil leaks or compression leaks.
Maybe a re torque is in order remembering to slacken each nut before applying correct torque.
And in the right order.

 

[5twins]

I've re-torqued multiple times, it hasn't helped. I tried different torque values for the 8 big nuts on top, from about 25 up to about 32, hasn't helped. I tried increasing the torque on the 2 bolts under the spark plugs by a few pounds while lessening the torque on the top 8, no help. I've resigned myself to the fact that the gasket has failed.

 

[motorbikerx]

Yes I actually answered before reading the posters name and then felt a little foolish....only a little foolish but.
Good to know you were brave enough to go to 32.
When doing mine I went to 25and then very gingerly took em up to 30 hoping with fingers and nuts crossed that I wouldnt pull a stud out or something drastic! Theres half a swing between 25 and 30 and I was very cautious.
Being a more is better sorta bloke.

 

[kawabunga]

Following up on this. First off, a shout out to everyone that provided info and guidance! The engine is back together and running pretty great for having essentially a blank canvas and no tuning or real baselines to work with. Thank you! I really appreciate it.

To sum it up... Cylinders bored .050" over, new pistons/rings, new-used cam, one new-used rocker, new cam chain, new cam chain guide, lapped valves, fresh gaskets and seals, new sump filter, new points and condenser, new advance weight springs. So far everything is going pretty well. After a few heat cycles I did a cold compression test and got 138/142, pretty stoked about that!


I do have a question though. I'm not sure if my auto advance mechanism is acting properly. The weights sometimes stick open when I manually open them. It depends on the position of the camshaft though. In some spots they stick wide open, in others, not so bad. However, when the engine is running, they seem to have no problem returning to closed position when coming down in revs.

It seemed like the advance rod was being held up by the points sticking on the points cam. I did lube the rod and cam on initial assembly, but with a standard grease. So I went and got some moly grease, tore everything apart, cleaned and regreased with moly grease. I did grease the weight pins as well. The rod does seem to move more freely after that.

So, maybe opening them manually doesn't really mean anything as long as they act appropriately when the engine is running? What are your thoughts? Does this seem normal or does something need service?

Here's a video to help illustrate.
First clip is weights sticking open.
Second clip is weights mostly returning to closed with the camshaft in a different position.
Third clip is engine running with revs to show weights open and close pretty well. Then shut with a poke to check to see if they did close, and they did.

Thanks

 

[TwoManyXS1Bs]

While running, the friction of the points followers will pull the advance shaft to a retarded position. When not running, only the return springs can pull to the retarded position, while fighting the point followers' friction. A polished points cam, with low-friction grease, can reduce that friction, allowing the mechanism to retard. But, having full advance travel while running is the important thing. The high points follower friction would be a concern to me, since it's an indication of potential early follower wear. I like mine to be slippery...

 

[gggGary]

Just working against the cam ramp will slow the springs. seen that. IMHO you do not want heavy grease in the advance rod it needs to be very light grease or maybe a bit of gear oil. The timing light is your friend, watch the timing as you gently run it up to 3000RPM and back down a few times, if the timing smoothly goes up and down without delays you are good.

 

[kawabunga]

Thanks for the feedback. I kinda figured that but wasn't sure.

The points have no miles on them, just test running on the lift.
Would it be unreasonable to hit the points cam with some steel wool to clean it up a bit? Or is that best left alone?

 

[650Skull]

you mentioned replacing the weights spring with a mikesXS replacements...............there have been reports of the springs not having the right tension. Could be a contributing factor?

 

[TwoManyXS1Bs]

A little comment on the MikesXS advance springs.

http://www.xs650.com/threads/review-of-some-parts-purchases-from-mikesxs.10849/page-6#post-526987

 

[5twins]

If you saved your original springs, maybe now that the advance and advance rod are all lubed up real good, those old springs might work fine again.

 

[kawabunga]

That sucks to hear about the inaccuracies from MikesXS. That site has most of the parts I need and now I'm not sure I should be shopping there...

I did happen to save the stock springs. Sometimes being a packrat pays off!

MikesXS advance spring on the left, stock on the right. I have no idea if these stock springs are the originals or not. The bikes odometer shows 18,700 miles.
They measure at 21.14mm and 22.21mm respectively.

A video of the two running in the engine. Not sure that there's much to see but more experienced eyes may spot something I'm not seeing.
First clip is stock springs, second clip is MikesXS springs. I tried to be slow and smooth on the first two revs, hard to replicate exactly each time. Anyone see anything interesting to note?

 

[TwoManyXS1Bs]

Your pic of the stock springs looks correct. Open coils, 90° twist of the hooks.

In your video, the stock springs appear to have a better, longer advance slope. As compared to the aftermarket springs, which appear to advance more quickly...

 

[kawabunga]

Stock springs it is then. Thanks for the help!

 

[kawabunga]

So I got myself a timing light. You guys weren’t kidding, they’re awesome! Wish I would’ve bought one sooner. Takes the uncertainty out of adjusting the points.

After adjusting with the timing with the light, I wasn’t far off prior, I’m now sitting about here. Both cylinders are to the right side of the center timing mark. Both are about the same by the advance mark. Is it worth fiddling more to get them at the center idle firing mark?

 

[gggGary]

No LOL