High mileage stuff

My bike is almost at 60k miles, and it's time I did something about that. I've got a few maintenance items lined up before uni starts back up in the fall:

- New head gasket (it's actually leaking at the head, not the valve cover gasket)
- New cam chain
- New cam chain guides (if necessary, I'll post pics once they're out)
- Rebuild/reset the tensioner
- New oil+filter, light carb cleaning, valve adjustment, sync, colortune, etc.

After doing a bunch of searching on the forums here, I've also learned of a few more jobs I can/should do with the head removed:

- New cam chain tunnel gasket (why is this so $$$)
- Clean/decarbonize everything
- Lap the valves, new valve stem seals

Most of these items are just straightforward replacements, but I have a few questions about procedure, mostly about lapping the valves, since I've never done that before.

- Can I rent a valve spring compressor tool from an auto store, specifically the "clamp-style" compressor that is used for our bikes? I don't really want to buy one just for this job.
- What kind of valve lapping compound(s) would you guys recommend?
- Any recommended tutorials on how to actually do this? I have a factory manual which does go over this procedure, but any practical advice from those who have done this would be appreciated.

Thanks in advance!

 

Since preventive maintenance is based on knowing when to intervene before something breaks, I'd also like to hear others' opinion on the longevity of alternator brushes and chain, oil pump chain, and any weak points in the starter system. Any of these might be a real "trip-killer" if they fail far from home, so I'm wondering what intervals are appropriate as my bike gets older.

 

The factory claimed alternator brushes needed to be replaced every 10K miles. One of my 550s is at 27K miles and the alternator brushes aren't worn to the lines yet. I may replace them simply because of age, or to be proactive at 30K or so.

In the shafties (650/750/900) the only real "Achilles' heel" is the "primary" chain guide/tensioner. It's known to disintegrate at some point and the chunks get caught in the shifter forks. The chain itself is not known for wearing out.

Cam chain and guides at 60K is probably prudent, as are valve stem seals and a quick touch-up of the valves (lapping) if the seats are in good shape.

 

Would that be the cause of the few cases I've heard of a transmission being "stuck in gear?"

 

Sure would. Do a forum search and you'll find a number of reports. When it happens, it's often possible to reach in through the access hole above the shifter mech and pluck the big hunks out so you can shift gears again. The real fix is to split the cases and replace it.

There seems to be no particular set of circumstances or conditions that cause or can prevent this; although it doesn't seem to happen as often to lower-mileage bikes. It may have to do with the number of heat cycles it went through prior to its hibernation, the number of heat cycles it subsequently gets put through when the bike gets put back in service, the condition of the oil it had in it when parked, dunno. There seems to be no real common factor except that it happens with alarming regularity.

If I ultimately decide to keep my 650 long-term, I'll pull the motor and replace the damn thing rather than have it fail halfway across the Continent somewhere. Luckily, the 550s are designed completely differently and don't suffer the affliction.

 

Is a better-quality replacement part available, or is OEM through Yamaha the only option?

 

I suspect (and fervently hope) that the currently-available replacement is made of a more modern, higher-quality plastic than the original. I would NOT recommend an NOS part.

That's a "chacal question."

 

Yeah, that would be a big investment in labor to do nothing more than "reset the fuse on your time bomb!"

 

A couple more things if the motor is all apart -
Replace shifter springs
Inspect / renew the starter clutch
Put a magnet in the sump - I place magnets on my oil filter and you should see all the crap they collect.
Gaskets at shifter and output shaft.

 

Back on-topic:

I've made these for different model engines by bending a short piced of "band-iron" into a "U" shape and using a big "C" clamp. Have not tried this on an XJ cly head, but it's worth considering for a one-shot project.

I've always bought whatever my favorite auto-supply store carried. The name "Clover" comes to mind. Generally there are 2 grades--course and fine to be used in progression. It's less important what brand you buy than it is to flush it all out with solvent and compressed air when you'te finished.

I like any cheap suction-cup tool, but a short piece of rubber tubing can be hose-clamped onto the valve stem for spinning from the "top" side of cyl head. It's important to keep lifting the valve off the seat to work fresh compound back in between--only a small amount of compound is needed, but it is quickly ejected and needs to be constantly smeared back into the joint.

When finished lapping, you need to check the seat width with some dye paste. If it exceeds maximum specs, you'll need grinding or cutting tools to relieve it above and/or below the seat.

Anybody with the skills to remove the cyl head will find lapping to be a simple job. I can't recommend a tutorial, but a web search should find a number of these.

several edits for spelling, etc.

 

This was really my main question. I checked my local auto parts stores online and all they seem to have is the Permatex Valve Grinding Compound, which doesn't indicate any kind of grit value. I thought I needed a fine grit and separate coarse grit compounds as you and many tutorials have said.

I'll have to look around at a few other parts stores if they have the correct tool to rent. I've made a few tools for working on the bike, like a manometer and the yics block off tool but I don't think I feel confident making a tool to do this.

Thanks for the advice, more Q's and pics will come when I get the engine apart.

 

I've always had two grits available, but not convinced this is absolutely critical. IIRC, even the course grit leaves a good enough finish that it could be assembled and run as-is but may take a little longer for the surfaces to burnish themselves during break-in. The fine grit would be noticeably slower at removing metal during lapping process. Maybe your parts stores are selling something in between (call it medium) that should be suitable. Permatex markets good quality, and standard valve-lapping practices prevail among 4-cycle engines, auto or cycle.

edit to add: In a recent conversation with an old-school Yamaha dealer from the '70s & '80s, he reminded me how important it it to check valve lash on these bikes after break-in of a new engine. That would apply to a fresh valve-lap job as well.

 

I definitely plan to adjust the valves after all this, as they'll probably be out of whack after the valve lapping. They are probably due for adjustment regardless.

It looks like it's time to tear it down. But before I do that, I think I'll post some pics of my bike, since I haven't done that yet!



Click for full view:

 

Of course the clearance (lash) will need to be reset during re-assembly. My point was that it's prudent to check them again at break-in intervals similiar to a new bike, because they may further seat themselves during run-time after the lapping.

 

Update:

I'm just about to remove the cams. I have the cam sprockets off and I just need to remove the cam caps. The problem is that I don't know the exact order to remove the caps/bolts to prevent any damage to the engine. The #2 intake cam lobe is currently pushing a valve open. Should I start by removing the caps further away from that lobe? I imagine that the valve spring is putting quite a lot of upward force on the cam lobe / shaft, and I don't exactly know how to handle the

The manual doesn't say anything about this--but then again the manual also states that it is not a substitute for a general mechanic's education. I guess this is just one of those knowledge gaps?

So, what order should I remove the cam caps / bolts, given which cam lobes are pressing down on a valve?

 

As general mechanic, , here is the method that will be correct most of the time.

Break each nut loose, and then start at the center, and use a criss cross pattern, loosening each nut a quarter turn. Sort of like head bolt torqueing, only in reverse.. It will take a number of times, but you don't end up causing undue stress on the cam. The same method is used for tightening/untightening the bolts on clutch plates. CZ

 

What have I done!?


This is really dirty!



The tops of the combustion chambers. The other two (not shown) are extremely similar to the ones in this pic.


The lighting is poor on this one, but if you look closely there is definitely some wear on the end of this cam lobe (exhaust #2). There are a few others that have developed wear marks like this, but this one is the worst.


I have lots of questions now!

Once I get the head (valves) disassembled, it should be pretty straightforward to clean the combustion surfaces. I welcome any cleaning tips you guys have, as I don't think I can (or should) boil the whole head in lemon juice like I did the carbs!

But what about the tops of the pistons? I'm guessing that I want to avoid getting any chemicals and especially any dirt past the pistons. I assume the best (only) way to clean the pistons would be to start by removing the cylinder jugs, correct? It wouldn't be very difficult at this point. If I do so, should I consider new piston rings? Based on how well the bike ran before the tear-down I really doubt I have any compression problems, but while I'm down into the engine this far it would seem a bit of a waste not to do this. It could develop into a lot of work and $$$ though (going by chacal's piston advice in the catalog).

Also, what should I do about the wear on the camshaft? Anyone know what could have caused this? I really don't remember it looking like this the last time I adjusted the valves (~6 months ago, and certainly less then 5k miles).

I'll post pics of the cam chain guides once I can get some better lighting (daylight).

 

Best way is media blasting it, then parts cleaner and compressed air.

If you chose not to take the engine down further, then a wire brush and a shop vac will de-carbonize the pistons. At 60k, you most likely do have compression #'s that are low side, unless the engine was worked on before you got it. You need to measure the bore to confirm it is within spec. You can do the loan a tool thing with the local autoparts store. Measure the bore, and if is to the high side of spec, them it would be wise to renew the bore, pistons, and rings. If it is well within spec, then a good honing to give the cylinders a nice crosshatching will do, but do put in new rings of the appropriate size.

It would be adviseable to take the cams to a machine shop and have the surfaces polished. The wear is likely from metal particles getting between the cams and shims. Did you use a magnetic pluck tool to remove the shims? If so, they got slightly magnetized and will attract small particles of metal.

 

A little more disassembly:



I couldn't find the right tool to rent to remove the valves, so I ended up just taking the head to my local Yamaha dealer and had them remove all the valves and springs and whatnot. $40--stings a bit, but it's cheaper than the tool. I'll probably just have them re-assemble the head after I get it all cleaned up.

Upon closer inspection of the "valve area", I found a few wear marks that are a little worrying (click the thumbs to view a larger picture):



The picture in the middle shows what seems to be the worst wear mark, it's a noticeable scratch from the top which goes down to some horizontal wear marks. No equivalent damage to the corresponding bucket, though. The only thing that I can think of that I may have done to cause this was when I was trying to adjust the valves the first time--the tool may have slipped once or twice before I got the placement right, but I don't remember which valves this was on. But that's just a guess. None of the buckets show any real damage.

Going back to the rest of the motor: some of these exhaust side studs look very corroded. Do they just need a cleaning, or should I consider replacement [of them all]? All the sheathing around some of the studs was all cracked and corroded, and I've just cleaned them all off. Do I need to replace this sheathing? I don't have anything that could heat-shrink them onto the studs.



I guess the next step is to remove the cylinder jugs and pistons and send it all off to be cleaned up at a local machine shop. I'm also going to have lots of things measured, like the cylinder walls and pistons. I really hope I don't need larger pistons/rings. I doubt I have serious compression problems, but those parts really are difficult to find! Does anyone have any experience with aftermarket piston rings?

tl;dr: Scratches in the valve area, corroded/rusty studs, going to send engine parts to a shop for cleaning/inspection.

 

I've decided to not pull the cylinders. I originally wanted to, but I'm afraid this is becoming a little more work than I'd like.

That being said, I'm trying to remove & clean the rusted studs. I got one of them loose, the one in-between the 3rd and 4th cylinders on the exhaust side, but I can't seem to get the threads through the "dowel pin" around the stud, as there is still some corrosion on the inside keeping it from getting through.

Since the part is replaceable, I tried instead to remove it, but it is really rusty, and I may have messed it up on the outside a bit trying to get some kind of tool on it.



I hope I didn't mess it up too badly. I've got it soaking in kroil, I'll probably do that overnight.

Is this a pressed-in piece, or is it supposed to just sit there? What can I do to get this out?