Valves got louder then BAM!

[bleeble]

So I was cruising down the freeway a couple days ago when I noticed the bike started losing power (like it was running out of gas). Then the valves started to get noticeably louder. Finally, I feel a thud and the engine dies. I immediately pulled the clutch and hit the kill switch. On the side of the road, I thought I could smell a little bit of burning oil (which, for all I know, could be perfectly normal for my bike). I gave the starter button a quick tap and the engine didn't turn at all. At this point I pretty much assumed the worse and figured my motorcycling days were over because I sure don't have enough money to fix holed pistons. I figured a best-case scenario would be bent valves because those aren't too expensive.

After much calling, begging, and waiting, I eventually got the bike home, put it in the garage, and left it because I was too depressed to mess with it. I had some motivation and pulled off the valve cover today. The timing chain seems fine; it doesn't look like it skipped a tooth or anything. So I tried turning the crankshaft with a wrench... no dice. Next, even though I know I'm not supposed to, I turned it backwards. It moved smoothly. Turn it forward again... Now it's not stuck? After that I must have turned the engine 100 times and, aside from a little bit of hesitance on the first couple turns, everything seems fine.

Now I'm just confused. Things that make an engine go "thud" don't just go away... at least that's what I thought. My dad suggested checking the compression on the cylinders to see if the valves are sealing (maybe one hit a piston). I'm going to go get my hands on a compression gauge and do that as soon as I'm done with this post. I'm just wondering what may have caused this and what kind of horribly expensive things are likely to be damaged because of it (crankshaft? There's one for my bike on ebay ending in 2.5 hours ).

As always, your wisdom is appreciated.

[80GS750]

hmmm thats interesting.....

i would pull the side cover off the left side and check on the cogs in the stator area...

i was thinking spun main bearing until you said you turned it back and then it turned ok after that.....

something stopped the engine abruptly.. i wouldnt do too much to it until you can figure it out for sure..

if you bent a valve or broke something off, messing with it could make it worse...

i would pull the oil pan and look for chunks or metal shavings, that will be a good indicator of what happened.

[Nessism]

Do all the valves and buckets look okay? Shims all in place?

Not sure what to suggest but I agree with your statement that "Things that make an engine go "thud" don't just go away". Compression check wouldn't hurt but based on what you stated, I'd suspect something fairly serious. 80GS750's suggestion to pull the sump cover is a good one. Have a peak inside.

Good luck.

[80GS750]

are you hearing any grinding or weird noises when you turn it over???

if so , then stop!!! see if you can hear where it was coming from... with minimal turnage... and then troubleshoot that area of the engine...

the last thing you wanna do is cause more damage.. and it can be fairly easy to do with older engines and tight tolerances....

[bleeble]

are you hearing any grinding or weird noises when you turn it over???

if so , then stop!!! see if you can hear where it was coming from... with minimal turnage... and then troubleshoot that area of the engine...

the last thing you wanna do is cause more damage.. and it can be fairly easy to do with older engines and tight tolerances....

That's the interesting thing... I don't hear or feel anything abnormal when I turn the crankshaft. And, just for clarification, I'm not trying to turn it over with the starter or anything like that. I figured that's probably the worst thing I could do right now.

I was actually planning to drop the oil pan to replace a leaky gasket and check the strainer, so I'll probably do that when I have time this week.

Do all the valves and buckets look okay? Shim all in place?

Not sure what to suggest but I agree with your statement that "Things that make an engine go "thud" don't just go away". Compression check wouldn't hurt but based on what you stated, I'd suspect something fairly serious. 80GS750's suggestion to pull the sump cover is a good one. Have a peak inside.

Good luck.

I don't have shims and I'm not sure what buckets are, but nothing looked wrong or out-of-place when I took the valve cover off.

Unfortunately the compression gauge in my garage is useless, so hopefully I have time to pick one up tomorrow. Any ideas on what might have caused the loss of power? I was just driving at a steady 70mph when this started happening.

[80GS750]

hmm thats a tough one

something went wrong somewhere... i would be real careful till you find out what it is

[bleeble]

Well, I just improvised a compression tester... my finger.

Apparently, there is very little or no compression on cylinder two. Now I just have to figure out why. Whether it's a valve, piston, or something else, it looks like I'm going to have to pull the head, right?

[80GS750]

i would pull the head off and take a good look at it....

replace a few gaskets while your at it...

[tkent02]

Before you pull the head...

Look in the spark plug hole, any holes or damage in the piston tops, or marks from hitting valves will be visible.

Pop the valve cover off, watch the valve parts go up and down as you turn it over...anything unusual there?

Sounds like you chunked something all right. Which is really odd just driving along the highway.

[bleeble]

Interesting timing, I was just checking that. Looks like the piston in cylinder #2 isn't moving at all... It's stuck at the top of the compression stroke.

I guess that would explain the sudden halt then freeing-up of the engine. I guess I have a broken rod. Maybe the piston pin, but I'm not holding my breath. I'll consider myself very lucky if I didn't score the inside of the cylinder.

[duaneage]

The cap might have come off the connecting rod. I'd venture to say it's toast. Might be cheaper to source another engine because the crank is probably finished and rather than spend all that money and time rebuilding it you could just swap it with another one and use the old one for parts.

[80GS750]

oh man that sucks....

if the rod broke, where is the rest of it.... dangling on the crank? scoring up your sleeve? in chunks in the bottom?

i would tear it down, maybe rebuild, maybe part it out.....

that sucks man

[bleeble]

So I just finished pulling off the head. I don't see any obvious damage. I tried pushing piston 2 down a bit and turning the crank. Now it doesn't come up at all. Good thing I just scored a crank and connecting rods for $10 on ebay.

I'm having trouble getting the cylinder off. I've tried pounding "gently" with a rubber mallet. I've tried pounding mercilessly too, but that didn't work either. I think someone may have used a liquid gasket/sealer because I see a bit of white stuff oozing around the edges. Any suggestions on getting it off?

Now that I think about it, I'm probably just going to part this out and use the money to get my KZ900 running. 8-[




























Of course I'll be getting another GS down the line because we all know how awesome they are! Maybe a 550 next time... or maybe I'll go bigger and get an 850.

[duaneage]

Offer it up here on the GSR in one piece, someone probably has a bike with a great engine that looks like bad weather. The machine looks pretty good, it would be a shame to take it apart.

[TheCafeKid]

WHo knows, I may be interested depending on what you are asking. I have a 16v motor with a torched top end. Pistons look ok, would be a quick swap. Then again, if YOU were interesting in the lower, i would be interested in selling it. Youd need your top end, provided it was ok, might be able to use the jugs off this one. and youd need a couple of the pieces off your bottom end, like the clutch basket and such. But it would be pretty easy to do.