Engine overhaul. More or less?

A couple months ago I blew up my primary chain guide, resulting in my 650H getting stuck in first. (of course, it had to happen right before riding season). I picked the pieces out the hole under the gear shift cover, but I'm nervous now of getting stranded. (or having to ride home in 1st). (or exploding my engine (and getting stranded)). (i like parentheses).


anyways, i have a couple Q's before i start tearing into my motor.

my bike has ~22k miles. compression (dry) is 98-100-98-95. however, this is at ~7600-7800 feet above sea level. im wondering if these numbers are good? I think they're way too low, given my mileage, even at my altitude. does altitude even make a difference? maybe someone has an equation or a chart having to do with baro. pressure? at least they're all roughly the same...
I checked the valve clearances last winter and i need to replace/swap every shim 1 or 2 sizes thinner. could this cause lower compression?

Do you think that i should I plan on honing the cylinders, and lapping the valves? this is probably the only/last time ill have this engine apart, but i do want to hold on to this bike for a long time....
Will i need new rings if i hone 'em? does lapping the valves require removing the springs? should i plan on new valve stem seals?

Can i access the starter chain guide w/o disassembling the jugs/head? I seem to be turning up conflicting info on this...

should i consider replacing the starter chain and/or cam chain/sprockets? cam chain guides?

what special tools are required for splitting the cases on my XJ? Ive split a bunch of YZ cases, but i h'ain't never taken apart no valves. From what I gather, I'll need some kind of suction cup? Why? Can't I ghetto-rig something up? A special tool for to hold the valve springs?
I got a bolt that i can use to pull the alternator rotor. I have my ways to hold the engine/clutch/rotor/pickup magnet disk for to loosen or tighten them...
do i need a special tool for the middle gear? which reminds me: I have gear oil leaking onto my back tire; I wanna replace all the oil seals and o-rings having to do with the final drive. Will i need to worry about proper gear lash? my haynes manual says something like "you wont have to maintain your final drive, just check/change the oil periodically". ugg.
Will i need some kind of puller to pull the cases apart? the yz's cases are left-right, not top-bottom, so i needed a puller to get the main bearings pulled out of the case halves. Will the xj's bearings put up a fight? or can i just lift the top half away?

Should i get new main bearings? big end bearings? any bearings for the transmission shafts? Im gonna order chacal's HCP5462 Aftermarket COMPLETE ENGINE REBUILD GASKET KIT-- which i assume doesnt include any oil seals? i guess ill contact him on that one. what other oil seals are prob. gonna need replacing? so far i got--crankshaft end oil seals, and shift shaft oil seal...

and o my god, as if this couldnt get any more expensive, my clutch is starting to slip now and then. grrrr. any info here would be appreciated. (i admit i havent done my homework on XJ clutches).

Ideally, I would like to have all the parts ordered and ready for minimum XJ down-time... I dont think thats gonna happen, though, especially if I go for the cylinder hone and/or rod bearings.

anyways. any constructive input is welcome/wanted/appreciated.
Thanks in advance.

 

Those numbers seem low but consistent . Something does not sound right 22k you shouldn't have had any chain snap. Try putting a drop or 2 oil in each cyl see if its rings or valves. If your planning on keeping it for a long time. I would get it bored and new pistons just to be on the safe side timing chain I dont believe thats the chain your talking about. Check the oil pump if any pieces got in it it will be toast also. Are you sure thats original miles on it? If anything . I am not sure how tight the valves were before replacing the shims you might have burnt some valves . Your question on valves being looser with the new shims effecting compression you should actually have more the valves are closing sooner. But first do a wet test on compression if the numbers don't change valves if they do rings

 

Thanks for the reply.

sorry i wasnt too clear: just the plastic/rubber chain guide failed.
here:

http://xjbikes.com/Forums/viewtopic/t=2 ... guide.html

im gonna get to the wet test tomorrowish.

 

Pillow when you did compression test did you hold the throttle wide open and yes valve clearance will affect the compression test big time. The amount of money you will spend to go through the engine well you can buy another bike cheaper. To replace the chain guide you have to split the case

 

yes

which way? im leaning toward cutlass's reasoning that they'll read higher

Thanks, i'm well aware.

 

I cant think of a single way that valves being out of adjustment would raise compression

 

The altitude will affect your compression readings. The gage you are using reads in psig meaning pounds per square inch gage, or pressure above ambient, at sea level. The air is less dense at altitude so the same swept volume of air contains less molecules therefore less pressure. The mixture will need to be adjusted accordingly (leaner).

I'll be willing to bet if you repeat the test at sea level the pressures will come up. Can you put the bike on a trailer and take it down the hill?

As suggested, do a dry test first, then a wet test with a little oil in each one. Throttle wide open, fully charged battery.

 

They wouldn't. But they would lower it.

Couple of real basic things to consider:

-You don't need to pull apart the top end at all to replace the primary chain guide. You can go in from the bottom and make the repair. Yes, you have to split the cases, but top end disassembly isn't needed.

-Things like main and rod bearings will be either impossible to find or very expensive. Rings and pistons can be had, not super expensive but at 22K probably not necessary, depending on the condition of the cylinders.

-Your low compression could be nothing more than way out of spec valves, which you already know you have. I would put the valves in spec and test again before making your teardown decisions.

-The "suction cup" tool you're referring to is for holding the valves for lapping; they cost under $10. Lapping the valves does involve removing the valve springs, and you should plan on new valve stem seals.

-Your clutch starting to slip isn't unexpected at all at 22K miles it's due.

Your questions seem to indicate you don't have a service manual. GET ONE before attempting this type of major sugery, there are quite a few pitfalls in this process.

 

"Will i need new rings if i hone 'em? does lapping the valves require removing the springs? should i plan on new valve stem seals?"
you should, yes, they come with chacal's kit

"Can i access the starter chain guide w/o disassembling the jugs/head? I seem to be turning up conflicting info on this..."
probably not

"should i consider replacing the starter chain and/or cam chain/sprockets? cam chain guides?"
guides yes, sprocket and chain, no ($$ ka-ching $$)

"Can't I ghetto-rig something up? A special tool for to hold the valve springs?"
the springs have to come out, no holding them, a short piece of tubing that fits tight on the valve stem and chucked in a drill will spin the valves to lap them

"do i need a special tool for the middle gear?"
a hand impact driver to take out the staked torx screws holding the middle gear bearing retainers

"Will i need some kind of puller to pull the cases apart?"
no

"Will the xj's bearings put up a fight? or can i just lift the top half away?"
no, yes

"Should i get new main bearings? big end bearings? any bearings for the transmission shafts?"
if they were good before they should still be good

whew, thats a lot of questions

 

or do like the cool kids and put a piece of fuel line on the stem end and pull the valve while spinning (like kindergartener making a clay snake).
some fine grit residue wiped up from around the bench or surface grinder added to some oil is lapping compound.

 

thanks all.
I checked the compression on my little moped and got about 95-100 psi. I think that for this operation, I'm gonna just order the seals and stuff i need for just the bottom, and leave the top alone for now. except the shims. well assuming it can be done. check it:

me:
"Can i access the starter chain guide w/o disassembling the jugs/head? I seem to be turning up conflicting info on this..."

bigfitz52:
"-You don't need to pull apart the top end at all to replace the primary chain guide. You can go in from the bottom and make the repair. Yes, you have to split the cases, but top end disassembly isn't needed."

Polock:
"probably not"

lol so i guess ill find out...

One more nagging Q: I would still like to know if i need to worry about gear lash when i get to the final drive leak. or if any special tools are required. Thank You!

P.S. I definitaly have my mixtures figured out for my altitude, and i do have a manual. thanks for watching my back!

 

I can't think of any reason you can't do primary chain guide without pulling the jugs/pistons.

You WILL need to pull the head to lap the valves, so then you are pretty much tearing it apart.

TECHNICALLY, you should replace the rings, and valve stem seals.....BUT that's a LOT of $$.....I feel that if the rings are in spec and the cylinder walls are clean, just hone and put them back together. They will need to be "re-seated" and the used rings won't seat up as nice as a new set but you'll save a lot of $
Valve stem seals>> I've done it both ways, but with the 20-valve X engine, even $6 each the seals are $120 for a set...call me cheap but if they aren't leaking now due to age, the 22K miles are no-where near worn out. I believe with some creativity and the right tool you could actually replace the valve seals without pulling the head. On the other hand you are only looking at (8) so it's less than $50 probably.
There is a great write up for breaking in a rebuild motorcycle engine. If you baby it too much, you can glaze the cylinder walls. Beat the snot out of it and they won't seat right and you'll ruin the rings. I'll try to find it.

Go nuts and spend the $5 at Napa for proper valve lapping compound. I actually used a cordless drill to lap the last one I did. Slow speed, back and forth rotation and keep lifting the drill to let the compound back under the valve until you have a satin finish across the entire face with no pits. If they are even remotely burnt, take them to a shop for proper grinding.

 

my mistake pillow, so far you get that guide from the bottom

 

You can take care of the guide without pulling the head/cylinders. You will have to split the lower case.
Done this twice now.

 

Update on my progress.
I have the engine all disassembled. I took the head to an engine machinist to check out a broken and half-fixed and rebroken exhaust stud. (DARN IT, PO) He said it probably wouldn't be worth the cost to repair it; I could pick up a new head for less. Still thinking what I wanna do on that one. Perhaps the brazing rod trick like this: http://www.youtube.com/watch?v=do2zYHwp78Y (go to 0:50).
He did however give me a good quote for to clean/blast my head, jugs, and cases (which i was dreading). they're there now in his boiling in his vat of EPA-approved solvent.

Here is why you dont want to ride much after picking out the shift-inhibiting chain guide chunks:


I had the machinist look at it. He says it can be reused, just get it smooth. He works mostly on FJ engines used and abused in "legends car" racing. says they're what keep him in buisness. So i guess i trust him, and ill just sand it with some 1500 grit and mic it to be sure it's not to whacked.
I put maybe 800-1200 miles on since the chain guide failure, but this looks like more wear than that to me. Dunno if the intrusive particle came from the guide or somewhere else...


anyways, more pics:

chain guide. notice the bolt which ended up playing the part of chain guide:


PO strikes again:


Gotta get me a brass brush:


Valve spring compressor:


andrewlong's mess ain't got nothin on mine: