Unusual engine problem- oil magically disappears

Hi guys,
I am kind of stumped here and would like a little direction on where to start since I'm strapped for time and space to work on this thing. I have a 82 XJ750 Maxim.

I got my bike with 14k on it, cleaned the carbs, had it professionally tuned since I don't have the tools, and rode it around for a couple years. Last year I noticed that there would be an odd sound from the left side- I didn't think it sounded quite like detonation but it's hard to tell because it would only happen at speed and when it was under very slight acceleration. There was only a tiny point slightly above neutral throttle where it would happen, anywhere else was fine.

I replaced the pilot jets one size up thinking that it might just be ever so slightly lean, didn't really make a difference. Rode it around a lot and everything was great. This year, after doing all the basic maintenance and starting it up, there is a pronounced clunking on the left hand side, and it's extremely low on power, wants to die without throttle. There were particles on the magnetic plug but no big shavings or anything. The clunk is definitely mechanical though.

Here's the strange part, I put in the right amount of oil and rode it around the block, and it was almost a quart low. Added more using the sight glass, rode around the block, at the bottom of the sight glass again. It's not leaking. It's not smoking. Where is my oil going? How many places could that much oil even go?

I don't know if a ring disintegrated or what, but would it make more sense to try to figure out what's going on here and save this engine, or just try to find a junkyard engine without YICS that fits the frame? Would a 750X or 900X or something bolt up? Any kind of direction you can offer would be awesome. If I had the time and space I'd just rip it completely apart and figure it out that way but it's in my friend's garage right now so I'd like to limit my time taking up his whole garage with bike parts.

 

For starters, how are you checking the oil?

It sounds to me like you're not waiting long enough after shutting off the motor, and are probably overfilling it in the process.

The oil needs to be checked with the bike on the CENTERSTAND, and after being shut off for at least 10 minutes. If you run it, shut it off and immediately look, you'll see NO OIL. That's normal. On the sidestand, you'll see NO OIL. That's normal too.

When the "professional tuneup" was done, did anybody adjust the valve clearances? Or give you the "they don't need it because the miles are so low" line? Your ticking and loss of power may be a stuck/sticking valve.

And it makes a heck of a lot more sense to calmly diagnose this motor than it does to run off and buy a new set of "unknowns."

 

It's a pretty solid sounding clunk rather than a tick but I will definitely check the valves- that's easy enough to do. I will drain the oil and refill it properly, you are absolutely right that I was being stupid about that. My other bike is a XR650R and you have to check the oil within 15 seconds of turning it off, so I just wasn't thinking about what I was doing.

Thanks a ton for the sanity check- the XR to motard project has been going poorly and I'm just sick of looking at nonworking bikes right now. Everyone who likes project vehicles has probably gotten to that point once or twice.

 

When you said "rode it around for a couple of years",
did you have the valves adj in that time-or for
that matter any of the reg maint issues addressed?

 

Welcome to the site !!
You'll get tons more advise if you post-up your compression numbers and a pic of your plugs, labeled 1-4

Pronounced clunking on left side?? could it be tranny related??

 

Did not adjust valves, did everything else like driveline, frame seals and lube, fork seals and oil, brakes, oil, carb cleans, etc. I took it apart and sandblasted the frame and covered it with truck bed liner too. I'm pretty attached to it for that reason.

I checked and the exhaust valves are slightly out of spec- .004 for a range of .006 to .008 is the worst. This would not cause a clunking sound, right? I would have thought rod knock but that wouldn't make it run poorly too.

Plugs all look normal and I do not, unfortunately, have a compression tester.

 

You can get a compression tested from Harbor Freight for about $20... assuming there's a HF not too far from you. O'reilly auto parts seems to carry a similar line-up of tools to HF... at similar prices too.

 

For starters, your .004 exhaust valve is not slightly out of spec, it's horribly tight.

Valve clearance specs are metric. Exhaust is .16mm~.20mm. The American equivalents are actually not quite spec, .006"=.152mm, which is already too tight. (The primary concern is the tight side of the spec, as they get tighter when they wear.)

So you have a valve that's measuring .10mm (.004") that's supposed to be at .16mm MINIMUM. That's a tight valve.

-Get a metric feeler gauge; K-D Tools' 2274 is widely available: http://www.amazon.com/Tools-2274-Metric ... B000COBUQM

-Check ALL the valve clearances, and get them in spec.

-AutoZone will loan a compression tester if you don't want to invest in one; but get the valves in spec first, then do a compression test.

Stop guessing, it does no good.

What you're doing (or may have already done) is simply riding this bike into the ground. STOP, get some of the required maintenance items dealt with, and hope it's not too late.

Your clunk could have a number of causes; but in order to properly diagnose the motor, you've got to bring the thing into spec.

 

Ok I'll bite,
WHAT is a "frame seal"? and why would you "lube" the frame?

NO-a tight valve will not make any sound-But you will bend a valve.

Your best bet from this point on is to READ EVERYTHING on the site
reguarding proper maint, ifyou want your bike to last.

 

Sorry, it was late and my sentences are convoluted. Swingarm seals, and various points on the frame where things go through like brake pedal as well as the bearings for the trees. (Head bearings on a bicycle, is that still the same term on a motorcycle?)

The only reason I did not check valves is the bike shop people were quite insistent I did not need to do it before 20000 miles. I did not know at the time they are all completely stupid at all the shops- I learned that over the last few months when people kept arguing with me about what parts can and can't go on my bike and told me things like I need to chuck the chainguard on my XR in the garbage and put the chain on "really really tight"

 

A stuck valve can cause one heck of a racket.

A sticky valve that is being hit by the piston will make an even worse racket.

A badly burnt exhaust valve will create an odd sound that sounds mechanical but isn't.

A broken valve spring will make a bit of a racket, and because these bikes have dual valve springs, won't immediately reveal itself during a clearance check.

A loose cam chain will make a bit of a racket.

All of which are why I posted the "checklist" that I did. At this point the only logical course of action is to get everything in spec, and run compression tests. Then we'd have a really good clue as to what type of damage/how bad, etc., has been done to this motor.

Hopefully it's just valve related and not a holed or otherwise damaged piston.

 

For future reference: Valve clearances were to have been checked at 3000 miles; then every 5000 miles thereafter.

Every 5000 miles. It's not a "one-time" proposition by any stretch, and can work out to two or three tiimes a season if you ride a lot; but it still can't be ignored. So they did give you the "it doesn't need it yet" line. They may owe you a valve job.

 

Alright, I will get the right tools and some shims and report back what I find out. Anything else cheap and easy I should take a look at now while I'm at it?

I don't really understand why people would make a big deal of not wanting to check the valves- that took no time at all. Possibly they don't take the plugs out first so it's hard to turn by hand or something?

 

They're afraid of it because the owners' manual said to take it to the dealer. Or maybe because of the perceived difficulty; it beats me. Fear of the unknown, maybe.

The guys that worked on the bike claimed to know what they were doing; why didn't they want to do it? They knew darn well it was necessary, the 20K line was just BS.

Don't buy shims until you know what's in there, you won't know what you need.

You might want to replace the valve cover gasket AND the "donuts" on the bolts so it doesn't leak on you. Those donuts are what push the cover down, the bolts are limited by the stop collars on them.

 

SacMC I did the valve shim check/replacement and it was pretty easy. There is a great 'How To" on here done by BigFitz as well. Follow it and it should be pretty easy. The shim bucket tool gives some people problems but once again if you follow the how to you may not have many real issues. I found it easy to use...

 

I just got done responding to another thread where a member admitted he hadn't checked his clearances yet because it's such a "daunting task."

I don't know what else I can do. A video would be an hour and a half long, and I don't have the production capability. I have three XJs, valve adjustments are just part of the maintenance schedule, like adjusting the chain or replacing spark plugs. On the airheads, ya gotta do it every 5000 miles and if you actually RIDE your XJ you had better learn how, or burn some valves.

EVERY 5K. Learn it. What choice do you have?

 

Honestly it is pretty easy using your 'How To'. I have never done anything like this ever. I used to work on lawn mower motors when I was a teenager, but that is about it. All in all I think the "daunting task" is a cop out. Seriously, without the how to it would have been hard, but with it, I don't think it could be any easier, unless you came to their place to do it for them...

I will go out on a limb and say that replacing a burned out valve is a lot harder than checking and replacing shims every 5K...

 

Thanks, truly.

Now try explaining that to "Mr. Denial" here; he just pretends like it's gonna go away or has nothing to do with his problem. http://xjbikes.com/Forums/viewtopic/p=2 ... tml#294216

Maybe you can talk him out of hurting his motor with only 9K on it...

 

Check out my little addition to the thread you referenced.

 

Could be that alot of the "modern" bikes go that far - my FJR has the INITIAL check at 26,000 miles :lol:

 

so I just had a thought ( maybe a scary one )
if I check and/or change every 5000 miles what happens after I'm on the smallest shims possible?
(I wish I hadn't thought about that) I'm at a 260 now

 

I wonder how long it takes to come to that? These bikes have been known to go 50-60k without a rehab, right? <edited out some dumbness!>

 

I've wondered that myself after looking at the charts.

 

Oh heck -
you just chuck that shim in a planing mill at the local machine shop, deck 0.05 MM, then break the sharp edge you just created, de-gauss it and re-harden it, and you're golden !



Seriously - what DO we do ??

 

If you are at the Smallest Shim Possible, ...

You are at the LIMIT for the VALVE, ... Not Shims!

Either you need the Valve and Seat Refaced, ... or

You might need BOTH a Valve and Seat.

You certainly cannot have a Shim machined to a thickness less than the Thinnest Shim design engineered.

A fractured Shim might result.

 

Which would then lead to a catastrophic failure.....OF YOUR WALLET!!! 8O

 

I don't think they would actually ever wear down to that point.

As the valves "bed in" they don't really change as drastically as they do when new. When I got my '83, it was untouched at 7100 miles. All 8 were tight. After putting them in spec, and putting 5200 miles on them, only one had changed enough to be out of spec. A couple of the others had tightened slightly, some had stayed the same.

My '81 has almost 27K miles on it. The last time I checked its valves, 5000 miles after the previous time, none of them had tightened enough to go out of spec.

The "rate of change" slows drastically over the miles; but you do still need to check them every 5000 miles.

 

I found your disappeard oil, leaking out of my motor! Grrrr must have somehow mangled my valve gasket the other day... New one ordered.

 

Hold the phone.

Where was it leaking? At the "half moons?"

I discovered a "caveat" to valve cover re-use on YICS motors; haven't had a chance to get the pics done and the tech bulletin up. Mine started leaking after the fourth re-use, right at the half-moons. A couple small dabs of strategically applied RTV solved it.

 

It looks like the half moons and some place up front. Though it is leaking bad. I just PM'ed you about it. this would be the second reuse for me. I have ordered a new gasket to be safe.

 

Maybe you picked up a virus from this thread and accidentally transferred it to your bike! :roll: :roll: