Checking Cylinder Compression

Oil rings are more than one piece.

 

The Top Ring is Compression
1 X 4
The 2nd Ring is "Wiper"
1 X 4
The Oil Scavenge Rings are 3-Piece each.
Upper and Lower Band
Waverly Ring
Bands
2 X 4
Waverly Ring
1 X 4

4+4+4+8 = 20 Pcs.

 

Hopefully, you're just researching. DO NOT buy any parts yet, especially rings, until we know exactly what you'll need.

The responses are correct, the top two rings are solid (although subtly different shapes) and the lower ring is the "oil ring" which is a 3-piece affair.

Please stay away from eBay for rings unless you find NOS, after all this effort you don't want to install some POS parts to save $20 or $30. And don't buy ANYTHING (except maybe head and base gaskets) until we get this figured out.

 

Ummm is anyone else scratching their head and thinking "Why has this engine with 18k ml been stripped down"? Or is it just me?

No offence intended, but I can't see any real reason why when the compression tests started coming back OK that A recommendation wasn't made to put it back together and try running it, then re-testing compression... Might have saved stripping it down, especially when it's low mileage and been running fine prior to recent shim work that may have stuck a valve.

Just my 5c

 

becuase he has no compression.

you didn't read the whole thread.

 

Funny... I could have sworn the last time he posted the compression test results for all 4 cylinders they were... 190, 135, 125, 125.

Looks like compression to me.

 

I have been following this thread for a few days and I tend to agree with Alive. No offence towards any of the suggestions by others but I would have started by going back and looking at what started all of this (ie - valve adjustment). One thing that I have learned in nearly 30 years of engineering experience is that, the simplest explanation for a problem is usually the correct one. Don't forget, this all started after the valves where adjusted not before. When all else fails, go back to where you started (the valves). Since you've got it apart, go ahead and make sure everything is within spec but if you don't find anything, get some new gaskets, put it back together and recheck the valves.

Regarding the compression: the last check revealed it was higher than the others with oil added. If the same amount of oil was added to all the cylinders then #1 shouldn't be higher than the rest unless something else is going on... carry on.

 

Also give it a good port and polish

 

Close. The bike had been running funky, although he'd ridden it for two seasons. He did a valve adjustment, and discovered some seriously tight valves. After fixing that, and at the advice of this forum, he did a compression test.

The motor was pushing really decent numbers on 3 cylinders, and one was so low it shouldn't have been firing. Then he did a "wet" test, and that same cylinder jumped 40psi+ OVER spec, while all the others gave expected readings.

The tests were repeated to confirm the results. Found some interesting "evidence" on teardown, follow the links to his PhotoBucket gallery.

You've been inside a motor or two; take a look. This one's a bit perplexing; to save some typing read back through the thread. I'm suspecting either "PO tracks" or a near piston failure. We've got an experienced 2-stroke guy onboard (more seizures and piston failures there) and we'd certainly be interested in your opinion as well. The #2 ring is so tight in its groove that he can't get the smallest feeler in, and the cylinder walls have some interesting patterns on them.

 

You are right... It's certainly not black and white....

I would have run it up again one last time prior to pulling it to bits.

I briefly flicked through the photos and no 1 was not running right, but these motors are known for being reliable... In saying that, there is always an exception to the rule.

Interested to see how it goes once back together.

I'll read through again... I skipped a couple of pages

 

Hindsight is always 20-20, and he's learning (quickly, I might add.)

Take a look at his PhotoBucket links, you'll see what I'm talking about, and thanks.

 

Let me try again... The compression was low after adjustment, some carbon or other debris was holding the valve open. He then adds oil and the debris is dislodged now causing the valve to properly seat. The valve is still too tight so his compression numbers rise to an abnormally high number. Moellear states heavy oil at exhaust header and carbon build up. Could be a rich condition from a possible exhaust valve not seating properly causing incomplete combustion (ie carbon build-up). Seems feasible to me what say you?

RickCoMatic had a good suggestion on page two of this thread: "You can take a Head off the Bike and "Level-it" up-side-down, fill the Combustion Chambers with Rubbing Alcohol and look for Bubbles or a Leak to detect a Burned Valve". Have you tried that?

 

i have not. just pour the alcohol on top the valves in this shaped bowl area? i would think that it would drain down the plug hole. but sitting in the house when the head is in the detached garage makes me cringe thinking about walking in the freezing cold is just not right so I could be wrong...also, the alcohol won't harm anything i hope, correct?



P.S. I got this cosmetically a little cleaner, ready for a new gasket, and the tachometer housing on the head is refurbished with correct rubber. That Kroil stuff REALLY works. I was amazed

 

One other point... There is an excellent adventure story on ADVrider about a bunch of young east coast guys that took some 30 to 35 year old bikes on a cross country trip to California and back. On the way to Kansas, the TX 500 started running very badly with low compression. The TX is notorious for developing a crack in the head so they assumed that's what it was so they were going to scrap the bike. The mechanic of the bunch developed a hunch just before they gave up on it. He surmised correctly that one of the valves wasn't seating properly. He scraped off the debris and they continued on for another 6500 miles in 30 days. An inspirational read!

http://www.advrider.com/forums/showthread.php?t=366117

 

Put the plugs back in and tighten them before testing.

 

duh!

ski84.. i've read the ENTIRE story a year or so ago when I became a member on ADV!!! it was truly quite an experience, just from the literature the same aged guys as myself did that. upon graduation from college in May I was thinking about doing something like this too.. but now we're getting way off topic and I'm gonna re-read their section about fixing the valve in a strangers shed.

on topic: with the compression #'s across the other three cylinders, would anyone suggest replacing all rings? it seems borderline whether or not the pistons would need new rings across the board. suppose i don't have to think too hard about it now Fitz, just wondering and will make purchases after determining a solution. one step at a time

 

improperly seated valves won't cause his compression to go up when he does a wet test. by putting oil into the cylinder. that's a sign of rings.

doesn't alcohol vaporize?

you do have to fill up the whole chamber so you can test the entire valve seating.

if you only do one cylinder. then you've gone from one dead cylinder being worse then 3 to haveing one cylinder run better then the 3.

the smart thing would be to do all 4. if things don't look good then you'll be kicking yourself in the arse for not doing a thorough job. youi'll have to take it apart again. and buy all new gaskets AGAIN.

i know fitz is concentrating on one cylinder. to find out why. but only doing 25% of the motor isn't worth it.

 

You're supposed to get a metric spark plug for the spark plug hole.

 

I suggest you do and my point is, don't assume the worst!

 

TOOTHPASTE! hilarious. for more details see link

 

forget the Rubbing Alcohol just lap the valves and be done, in the process your going to check the valve springs and the valve stems
and put on new stem seals and clean that carbon from the exhaust ports then clean the head and cylinder mating surfaces like a operating room floor, the block and bottom of the jugs too
your not halfway done don't think about putting it back together yet

 

Exactly.

But that's the course he's on, and although we've been trying to figure out #1 (which sounds so far like it may need to get a new piston) replacing all 4 cylinders' rings is indeed the only way to do it 100% right.

Plus everything you just listed for the head.

 

http://www.restoreusa.com/Engine_Restorer.html

 

No way. That stuff is for cars; there aren't that many 10K rpm automotive motors out there, except maybe in racing.

 

That's why you need two cans ...

 

so by lapping the valves, I'd probably need to replace all shims then too? this is getting mighty expensive..

 

You shouldn't remove enough material to need new shims if they were in spec correctly to start with. Too tight to begin with then you might.

 

Relax. You just shimmed the valves, and the lapping process won't remove enough material to make a difference.

Further, your bike has such low mileage, that the valves shouldn't require much lapping at all.

Have you had a chance to pull the suspect piston, scrub it clean, and inspect it with a magnifying glass yet?

 

yes I pulled it off this afternoon and will scrub it clean after finishing this post. pics on photobucket link again . the theory that maybe PO placed a different piston in cannot be correct. pictures show that it is in fact a Yamaha piston for my bike 4H700. on the same picture you can see "094" is this the production # of that particular piston? now whether or not the other three match this piston, idk. everything seemed to be in good shape with nothing out of the normal, from my point of view. i will admit: i didn't get a magnifying glass out but will take another glance at it soon.

snapped a view pictures of the connecting rod just to show nothing seems to be out of place there as well. on the flip side, concerning the head, I am getting it cleaned up for when a new gasket is ready to be in place. do normal auto stores carry the valve spring compressor and rod/suction cup to spin valves in place for lapping? i'm hesitant to do the valve job primarily because this problem deals with rings/pistons via wet compression results. i wouldn't mind doing it but with my mileage it shouldn't matter either. then again,, i do have it torn apart this far lol.

 

Re: Piston replacement--- sure it can. It could have come from another 550, off eBay, and not been properly fitted.

You need to get it scrubbed clean and examine for cracks developing on the underside, or in the ring lands; they aren't always easy to see/apparent which is why the magnifying glass.

Re: valve spring compressor: That's generally a "borrow" from someplace like AutoZone; and they MAY have the correct type. You can't use the "paddle" type, it needs to be the barrel type, with a relatively small diameter, long "barrel."

The suction cup tools are super cheap; I bought a "set" (two tools, each with a different size cup on the ends, giving you 4 different sized cups) for under $10 some years back, they're still that cheap. They probably have those to loan, too.

Why bother with the valves? They were all at least somewhat tight, so it's worth a look at the seats, and a quick lap to "freshen" them if nothing else. Valve stem seals are cheap, easy to replace and yours are a quarter century old with 18K miles on them. And you have the head off already. NOT doing the valve "service" just wouldn't make any sense; especially if you get it all back together and discover that at least part of the carbon in the one cylinder was from a bad valve stem seal. Just not worth it.

Plus, lapping valves is fun, it really is (well I think so anyway.)

NOTE: VALVE SPRINGS HAVE TO GO TOGETHER, AND IN THE HEAD, IN A CERTAIN ORIENTATION, direction of spring-coil wind wise. I didn't see it in the Haynes; so be very careful on disassembly, and I'll get you the page from the factory book.

 

so here's the piston cleaned with hot water and scotchbrite pads. it shows no defaults and dad agrees. sorry for the big picture, i wasn't sure how to resize the picture in my photobucket album



at this point, what other step would you fellas recommend besides purchasing all new rings, slightly hone the cylinder jugs, and tear apart the head & lap the valves? put it back together after that with new gaskets, test the compression and hope like h*ll its back to normal? reminder; heading back to school tomorrow so I won't be wrenching on it much anymore. when I do I'll prepare myself and others

 

Wow, you've done lot of work, being patient and working one step at a time so KUDO's to you for that.

Has anyone been able to answer the $24,000.00 question yet?

Definitively, what caused the compression to jump from well below spec to 190PSIG with the addition of less then an ounce of oil?

Without knowing that, most would agree that it's a bit dicey to reassemble. I know that there have been several theories brought forward. I suppose if the bore is truly round and correctly tapered, new rings and slugs are going to make it run well. I think at this point, I'd pull another piston, remove the rings and run it up and down the #1 bore and see what it reveals.

I know that Fitz is telling you the right thing when he suggests valve lapping while you're inside the engine but I also understand that you may want to pass on that step since you need to get it running and your time is now limited by school and you'd probably rather not task your Dad with having to do it(I'm sure Dad appreciates it). Maybe you'll hear that while it's best to do it since your in there, you can probably skip it and still be alright.



Good luck in school...boy you had a long break!!

jeff

 

So I'm home for a long weekend. Big day today; I honed the cylinder jugs, got the valve springs out and will lap 'em in the morning. Already emailed chacal for help but wanted some other opinions. Obviously I am ready and prepared to order all new rings but should there be any other preliminary measurements before doing so?

Bringing this long thread back after reading all of it over tonight. Wanted to ask a few of you also, given the condition of my piston in the above picture, I don't want to change/purchase a new one. Nothing looks out of normal and there are no cracks. Am I missing any other steps from the last time I asked?

 

If there is any question if the piston being cracked spend a few bucks and take all 4 to a machine shop. Have them magnifluxed, here in Texas it costs about 35 bucks and that will reveal any cracks. They can also check it for out of round at the same time. I havent worked on many motorcycles but have built several 400hp plus small blocks and know if your rebuilding a motor dont assume anything get it checked. Its cheaper in the long run.

 

thanks hardlucktx. I'll give it some thought since I discovered the napa machine shop does engine rebuilds in the back of the store. talked to the guy yesterday about valve lapping, seems really nice.

last time I'm asking. Will I need final measurements before I order standard rings? Its a friday and dad can borrow an ID micrometer from work if necessary. Tomorrow shop closes obviously. I wanted to order everything by the end of the weekend... Also, chacal must me on vacation cause I still haven't received a message from him which is kind of surprising

 

I would re-measure the cylinders after honing, yes, but just to confirm that everything is still within spec. I'm pretty sure you'll find it is.

If I remember correctly that piston was DEAD TIGHT in either its upper or second ring land clearances (clearance between the ring and the groove it's in.) That being the case, I would REPLACE that one piston; don't chance it.

Send chacal an email to the "info at XJ4Ever.com" address.

 

Yes you need to measure the bore before you order rings

 

Any updates on this?

 

thanks for asking Ravenz.. I purchased everything (new rings on all four cyclinders, a new piston just so I know its back to stock, and respective gaskets). My father was busy at the time so I asked kindly to get my mothers' and brothers' assistance to guide the new rings/piston thru the cylinder jugs.

it wasn't easy and some blood was shed due to pinching the rings while lowering the jugs back on. once I got it over the pistons, I was relieved. Put the head back on, camshafts in their respective correct location I hope in order to avoid timing issues, and checked the valve clearances. Everything seemed to be in spec so I covered it all up. My engine is now rebuilt practically so it BETTER be providing better compression by this riding season. all this work will be wasted if it never solved my problem (which was never solved in the first place, only theories were logical).

This was a mighty expensive job with a lot of time involved but most importantly, I feel I gained a lot of mechanical experience and respect to automobiles. As a young guy, I'm still in college and in my thermodynamics class yesterday we were actually discussing lean/rich gas mixtures. without the support & help from all you I would have never been this knowledgeable in the mechanics of an automobile. this really is like the closest/next thing to facebook in my opinion. thanks all for your support and once I go back home for easter break, I hope to have the bike fired up for a nice test ride. all that is left is putting the rebuilt carbs back on and a new set of spark wires (one was damaged upon removing it from the plug :x )

 

Wow, I just read that whole thread and have to say that it was a real pleasure!@ Like reading a really cool short story, I must really be enjoying all this more than I thought. Lots of great info and knowledge in this thread, thanks to everyone that contributed, you are true "bikers" based on my understanding of the word!

Mac

 

I am NOT a "biker" I'm a lifelong vintage motorcycle enthusiast.

moellar you did "gap" the new rings before installation, right? And orient the end gaps as specified by the book on reassembly?

Did you end up lapping the valves? Yourself?

(Just checking your work.)

 

Rather than starting a new thread, I'll try asking my questions here first.

Compression Test:
A - Do I need gas in a bike to do the test?
B - If I KNOW the carbs need to be done (my 2nd parts bike), can I still do the test anyways and get some "initial" numbers?

 

No. And you unplug your TCI so you get no spark.

You'll get accurate numbers as long as the throttle blades open to wide open throttle.

All you need working properly is a battery, starter and compression tester.

 

A- NO.
B- Carbs HAVE NOTHING to do with a compression test (other than get in the way, which is why you have to hold the throttles open.)

VALVE CLEARANCES can affect a compression test, but only if really out of spec.

All you're doing with a compression test is evaluating the basic "air pump" that is comprised of the crankshaft, rods, pistons, rings, cylinders, and cylinder head/valves. You're testing its ability to create compression.

You unplug the TCI to keep it from self-destructing trying to fire spark plugs that aren't there/aren't grounded.

All you need is a compression tester and the ability to spin the motor. You could do a test on a motor that is out of a bike, with NO carbs, if you could spin it.

Make sense?

 

iwingameover and bigfitz52

Thanks.

I need to charge my 2nd bike's battery. Maybe I'll test tomorrow.

I might as well check my 1st bike as well

 

Not a bad idea to do every season, or every other season, just to keep track of how the motor's doing.

 

long story short, its RUNNING! fired it up yesterday and by last night I was able to take it around the country block. boy it was nice! whew was it smoking too lol! all the excess oil from my hands and inside the cylinders/rings plus all new gaskets were getting hot for the first time. by now it stopped smoking and i'm just taking it easy on the rpms to let the rings seat properly

yep. wound up doing everything myself. the valve lapping was easy part..getting the rings and pistons back thru the jugs took 3 of us though. I'm just glad its all done and I've learned a lot about the mechanics of the bike too. worht the experience

few questions.. I never adjusted the cam chain (should mine be manual or automatic?) when it was removed. there is not a lot of sound from the chain but once in a while I think I can hear the chain. need to do anything with it?

also, the carbies are giving slight issues as suspected. they were completly rebuilt (throttle shaft seals, carb dip, the whole nine yards) and now I've got the pilot mixture scews nearly 3 turns out. how can i get the idle to run without choke at all? turn the screws out more or less? just so I know: turning the screws out makes it richer and turning the screws in makes it leaner right? or is it backwards..

thanks to all those who helped me out way back in december/january with the disassemble process. i am fortunate to have all your help folks and hope to return the knowledge to other members on here

 

WOOHOO! That is good news indeed.

-Even more important than "watching the revs" is not lugging the motor; make sure you keep it spinning happily.

-Does your camchain adjuster have a bolt with a locknut sticking out the side of it? If so, it's not automatic.

-You're going to need to vacuum sync the carbs to get it running 100%. I forgot-- is this a YICS motor? If so, you'll need to block the YICS for the vac sync.

Out is richer, in is leaner, as you thought; but fiddling with the mixture screws won't get it idling. Gotta get it sync'ed.

First though: How did you set the float levels?

 

You can get the mix screw set near perfect with a "Color Tune" tool.
Mine is 14mm. Let me know if you need more info on this.

 

yeah, its def manual tensioner then. no YICS motor, and i used Gamaru's bench sync with the paperclip. it was successful for me a year or so ago. the floats were set wet only. I tried to booger around doing it dry but felt it was a waste of my time. did all four carbs simul with clear tube. adjusted one of 'em and got them to be level across the rack at or near the washer and screw for the bowls. should be good there.

i got one of these from a former XJ member from Toledo. nice guy and he got it from chacal. just gotta sit down and learn how to use it. isn't an iterative process? do something, then colortune, do something, then colortune... what is that "something"? sorry for not taking the time to research I'm just happy the engine runs lol