On the road again at 40.............the bike that is

[robinc]

Ok, that makes sense gggGary, thanks. (I guess that's the answer I really wanted.....lol)
It is the only runner I have. The 78 is still in the gotta get back to it stage.

So, might as well enjoy it for awhile, keep learning, and be even better prepared at the end of the season.

Hoping swapping the advance weights might tame those hanging revs a bit. Not a big deal, but have to bring engine rpm's down in gear when coming to a stop. If I pull the clutch too early and coast to a stop, revs hang sometimes.
Was going to wait until I did the rebuild to pull the Pamco/E-advance trigger, but if swapping the weights doesn't bring any joy, might do that upgrade now and it's crossed off the list.

Thanks again guys.

 

[gggGary]

For a poor mans leak down: get the crank held at TDC (in gear, rear brake applied works) feed air in the plug hole, two part compression testers let you connect an air hose. Turn compressor dial down to zero PSI, slowly add air, listen around to see where it escapes. turn crank to TDC other cylinder, repeat.

 

[robinc]

Yes, thanks gggGary, My compression gauge isn't the complete kit as you've shown, so instead of going out and buying one (never mind buying tools though) I did something similar.

I think I posted it a few pages back when you guys then helped diagnose my problems. Engine problems that is, the rest will take you guys waaaay too long.

http://www.xs650.com/threads/on-the-road-again-at-40-the-bike-that-is.49360/page-10#post-515140

Thanks again for everything!

 

[gggGary]

What compression are you getting now? If the engine is good enough to ride with, I doubt the meatball scrub the valve seat thing is worth doing. IMHO that's a zero compression, last gasp before pulling the motor thing.

 

[robinc]

OK, that makes sense. I'll just do it up right.

Here are the last numbers I have tested 07/21/17.

Checked compression when warm:
Left 155 / 160 /160
Right 150 / 150 / 150

5twins then mentioned this, which is an excellent point.

A compression test isn't a tell-all and can be misleading. Yours read very good yet your cylinders seem to be full of oil. You may have heard that if you get a low reading, add a spoonful of oil to the cylinder. If the reading comes up, your rings are bad, no change means bad valves. The added oil seals around the rings and gives you a higher reading. That's what could be happening with yours. The oil leaking past the rings is sealing them during the compression test and giving you a false high reading.

So, makes sense to me to enjoy it for awhile longer, then do the full job and have peace of mind that all's good.

 

[5twins]

You should be able to finish the season before doing the rebuild. I ran mine 2 seasons before tearing into it. I did mine not so much for excess oil usage but more so because I was running out of timing plate adjustment and I had that loud ticking at start-up for about 30 seconds. I knew it needed some work inside. I had done topends in the past on some of my other bikes and I knew from those that even if there was nothing radically wrong inside, they benefited from cleaning all the carbon out, re-sealing the valves, and fresh gaskets.

There was a recent thread about finding a good machine shop. You should only need that if you find a re-bore is required. If you just replace rings and need a hone job, most cycle shops will do that and it doesn't cost much. Honing is a pretty quick job. You don't hone a cylinder much longer than 15 to 20 seconds. I had my 1st one done many years ago and I don't think it cost any more than $5. I'm sure it would be a bit more now but probably not too much more. But, get a price and compare it to the cost of buying the bottle brush hone yourself. The 3" size needed for the 650 can usually be had for $20 to $25. Like I said, I had my first one done but after that I started buying the hones and taught myself to do it. It's quite simple really, chuck the hone up in a drill, run it very slow (less than 1000 RPMs), and plunge it in and out of the cylinder for 10 to 20 seconds. It takes a little practice to get the "plunge" speed right so you get the nice 45° angled cross hatching, but it's not hard to get the hang of.

Determining whether the piston and bore are worn beyond spec or whether the valves leak is pretty easy for the home mechanic. Yamaha makes the piston/bore part easier by putting the original sizes on those parts. The piston is where most of the wear occurs because it's softer alloy, softer than the steel bores. Measuring just that is usually enough to draw a conclusion from. Then there's the quick but effective feeler gauge check - jamb a feeler gauge between the bore and clean, ringless piston. .004" or less is what you want to find, in which case just new rings will probably do.

Checking the valves for leaks is pretty easy using solvent and compressed air .....

 

[robinc]

Wow, more great info 5twins. Thank you. That is great news. You're making this seem easy....lol.

I have read about your compressed air leak test, kerosene is on the shopping list, can't find that old jug.

If a year ago someone had told me I would be tearing apart and rebuilding the top end of the engine on my motorcycle I would have asked them what they’ve been smokin’.
Now, the more I read about and think about this job, the more I'm getting excited about it and actually looking forward to the prospect.
Now that the time pressure is off, even more so.

Good thing I'm a packrat, I even have just the right steel work table I can set up in Papa's shop (lower level) to use for my engine bench this winter.
Knew there'd be the right job for it someday. Looks like somedays here again.

It's been a pretty amazing summer, looks like it's gonna be a pretty amazing winter too!

 

[5twins]

I pulled this A/V cart out of a dumpster at work, thinking boy would that make a great engine cart/stand, and well, it does. I added the outrigger on the side to suspend the cam chain from .....

 

[Mailman]

This is so great, I'm learning right along with you Robin. I love that roll around cart idea, that leaves your workbench free for other stuff and when you're done for the day just push it to one side.
Robin I hope you don't mind me inserting a question into your thread but you've got the hot hand right now , so to speak.
About honing, I have used this type of hone long ago, but they still sell them.

But now I hear people talking about this type and they seem to prefer it.

Is that type preferable? Also what is the recommended oil when honing?

 

[weekendrider]

Some feel the rail or bar type removes too much material and prefer the ball type.

 

[5twins]

The flex hone is preferred. The stone hone can remove material and enlarge your bore if you're not careful. The flex hose won't, unless maybe you run it for 20 minutes or something, lol. Also of note is the type of finish the two give to the cylinder walls, they differ. The flex hone gives what is called a "plateau" finish and that is better for quick ring seating. The stone hone leaves a rougher, coarser finish and rings will take longer to seat.

Typically, when cylinders are bored, they are bored close to size, then stone honed to size, then final finished with the brush hone. For a simple hone job to prepare old cylinders for new rings (no re-bore), the brush hone is all you need (and want).

 

[robinc]

Great cart 5twins. I'll have to roll to the bench, but it will be a dedicated engine bench. Will add an outrigger, great idea!

Carry on Bob, the more info here the merrier.

 

[MaxPete]

Robin: I've gotta tell you, those compression numbers are really quite OK. Here's the math (with some slight simplifications):

• Atmospheric pressure: 14.7 psia (the "a" means absolute - this is the pressure that we all experience all the time)
• XS650 compression ratio: 8.4 : 1 (which isn't particularly high - that's why our bikes don't need premium fuel)
• Cylinder pressure: approx. 14.7 x 8.4 x b = 123.4b psi where b is a coefficient with a value of about 1.2-1.4.

So.... an engine with a CR of 8.4 should have a maximum "cold" (no fuel or spark) pressure of about....148-175 psi.

In my experience, a typical engine giving compression numbers of 150-160 psi is in pretty solid condition. Oil consumption problems in an engine with that data is likely to be due to the valve guide seals rather than piston rings or to poor sealing of the valves themselves.

So, while rebuilding an engine can be fun, I seriously doubt your compression numbers will be very much higher after doing the rings. Your excess oil consumption is most likely to be the valve guide seals - and didn't Gary say he has figured out a way to change them without pulling everything apart?

Pete

 

[5twins]

They do make special honing oils but you don't need them. Even plain old 10w-30 is acceptable .....

http://www.brushresearch.com/flex-hone-instructions.php

 

[Mailman]

Thanks 5Twins! That link even had a nice little video of the tool in action.

 

[TwoManyXS1Bs]

Here's a fun read:

http://650rider.com/index.php?name=Forums&file=viewtopic&t=6061

 

[robinc]

Hey Pete, as much as I wish I could take the blue pill, I'm resigned to the fact that the red pill is the way to go. I've got over 34,000 kms. on her and no-ones been in there yet. Plus it sat for 9 years, drying out.

Here's where I'm at with this:

• Valve backs are oil contaminated, 2M diagnosed awhile back that seals at least are gone and a top end job is really what's in order.
• 2M also mentioned there are likely other things in there needing attention, only one way to find out.
• Piston tops as well are oil contaminated with baked on oil from who knows for how long. Only one best way to clean them.
• My good compression numbers could in fact be from oil leakage as 5twins has suggested. Only one way to find out.
• Discussed some of this in my thread with gggGary this morning and he didn't say the valve seal change on the bike wouldn't work but the valves need to be cleaned up and he said his meatball mechanic method in the engine is really a last ditch effort to save pulling an engine. He suggests riding it through the season and rebuilding it this winter.
• Don't know what shape the valve guides are in. Don't know if this is a legitimate concern but it is a question I have.
• Plus the other bits that can be measured and verified while in the neighborhood.
• I haven't found a lot of black bits during oil changes and we know they can come from different sources. So who knows what shape the "front" guide is in.
• I'm running out of timing plate adjustment room. I am pretty convinced my cam chain is really stretched. I used to set it to Haynes/Clymer manuals specs when I was tuning it up years ago, but can't remember how soon or long after I owned it that I really got to tuning it up right, other than just doing oil changes. Also I get a lot of cam chain ticking that lasts a lot longer than the 30 seconds that 5twins had if I set it the way it should be.
• As mentioned earlier in my thread, I swapped in the advance springs from my other bike, no joy, rpm's will still hang when decelerating. Today I swapped in the weights. Haven't had a chance to ride it yet, but still get the hanging up in my shop. Gotta be the cam chain.
• As 5twins said today, honing and new rings may be all that's required. Won't know without having a peek. And if it needs more, I want to know now, and not after putting it back together.
• This isn't an impossible job, and I have so far, and know I will continue to benefit from the help of some pretty amazing people around this place to steer me through.
• Then there's these personal thoughts. I'm going to learn a whole bunch more, which is good. I enjoy learning, in fact it's kind of a drug. I'll know so much more about how these work and how to read and maintain them better. And....I'll have the peace of mind of knowing that all's good and nothing was missed or ignored. There won't be that nagging question of "Should I have done.....?"

Boy, is this a list to convince you or me Pete? LOL

2M, gggGary and 5twins have all been helping out here and none of them have said don't do it. They know my level of shade tree mechanics abilities and they haven't said don't do it, rather they are encouraging me and giving me the advice and tools (literally pointing to them even) to accomplish this.

I'm not overwhelmed by the thought anymore and am actually looking forward to doing this, seeing whats going on in there, and getting her happy again., She deserves it.

For me, I'm going to set up an engine rebuilding bench in my basement and this will give me a nice project to work on over the winter as gggGary and 5twins say. Might even slip in some carb work.....lol.

But I can hear it now, "Can't you leave that bike alone for the winter! Now you're rebuilding a motor in the basement!" Oh boy.

If you guys think I'm wrong on any of this or have missed anything, please straighten me out.
I'm all ears and you know I appreciate all your help and advice.

"Honey, where's the baking soda?"

 

[xjwmx]

But I can hear it now, "Can't you leave that bike alone for the winter! Now you're rebuilding a motor in the basement!" Oh boy.

Is that coming from the wife?

 

[robinc]

Yup, and she still won't give me her baking soda.

 

[5twins]

With the type D cam chain tensioner on your model, you may have been setting the chain correctly only to have that setting changed, made tighter, every time you put the acorn nut back on. There's a good chance that accelerated the wear (stretch) on your cam chain.

As I've mentioned, I think every one of these can do with a topend job today. They're all 35+ years old now. If nothing else, most need the old rubber parts in there replaced, things like the valve guide seals and the front cam chain guide. Those things are routinely failing now. It's not really a mileage thing either, it's their age.