Running lean, what did I damage??

[hannibal]

I was riding on Saturday night and the bike died on me. It was the coldest weather I've ridden in (40ish degrees) and I suspect the bike was running lean. A few miles before it stopped, I heard what I thought was me running over a bolt or piece of metal. I now believe it was a lean "ping". A few miles later, I'm coasting to a red light in second gear and light throttle. As soon as I release the throttle to grab the brake, the motor immediately died and revs fell to zero. I pulled over and tried to restart it. It would try to turn but sounded like it couldn't make a full rotation. I've heard that running lean can burn a hole in a piston. I guess it could burn a valve too. I recently (less than 300 miles ago) checked valve clearances and adjusted the 3 tight ones with new shims.

I originally thought that something was hitting something inside the motor. As I type this, I'm considering an electrical problem that completely drained the battery and maybe that's why it wouldn't turn over. I did have lights after so that wouldn't make much sense.

I got her home yesterday and I'm trying to figure out where to start. I'm pretty sure I did some major damage. I'll first check the battery to see if it's electrical (that would be a good problem!). Then I'll try to turn it over by hand. If that doesn't work, I'll pull the valve cover and have a look. I doubt I'd see anything from there though. If I don't see any obvious damage, what my next step? Pull the head off?

I've never tackled anything this big, but I've said that about everything I've done on the bike until this point. If necessary, I'll pull the head, then the bottom end off the bike and carry everything inside. I think the toughest part will be dealing with the exhaust bolts. I'll start hitting them with PB Blaster today!

Any thoughts on where to begin?

[tom203]

Enough with the negative vibes! Look for easy stuff first.... Pull the stator cover and inspect the rotor/starter clutch area -then look at contact point side in case advance mechanism self destructed

[Nessism]

Unless the bike is heavily modified with pod filters and a chopped exahust it's seems doubtful that you were running lean to the point of trashing the engine.

Check for spark at the plugs and maybe perform a compression test if the spark is good. That should tell you something right away. The issue could be as simple as burned points.

[TxGSrider]

My experience with lean running four strokes is the signs of a problem will usually show up on the spark plugs. Bleach white insulator is a pretty fair way to see if an engine is running lean (provided you have some miles on the plugs). However if you see specs of grey on the insulator its usually a sign that its been running really lean and pieces of piston have started coming off. Then it gets to the real serious stuff like melted electrodes, ground straps, and broken insulator... Usually if they get there you may have a real issue... however, even then Ive seen nitrous cars that have been ran hard with all of that and the engine works fine after a plug change (I know, nitrous is a little different scenario but...).
So pull the plugs and see what you find. Maybe post up some pics of the plugs? Most of us love to haw and hem over pics of engine parts and give our opinions. lol

[tkent02]

As Chris Sorbi about his 850 pistons. Holes the size of a dime melted in each one, all caused by lean running from an air leak.

[hannibal]

Thanks for the encouragement. I'm hoping for the best, but preparing for the worst. Regardless, she will ride again.

Bike has stock 4 into 2 exhaust with K&N pods and 110 mains installed by the PO. Because it was freezing, most of the ride was second gear at 4 or 5k rpms. I've certainly worked it much harder in the past 2 weeks, including two 100+ mile trips.

I'll start with pulling the plugs and side covers off and inspecting the easy stuff. Then try to turn it over by hand. If it turns, I can try cranking it to look for spark and do a compression test.

tkent has said many times that lean can lead to holes in pistons so that was my first thought. Hoping that's not the case. Thanks guys!

[JTGS850GL]

If it wont crank over properly then start at the battery first. Don't start out by taking anything off. If the battery voltage is low then charge the battery. If the engine starts after charging then start verifying your charging system.

[hannibal]

It's not looking good. I tested the battery and saw 12.5 V. Opened the breaker/points cover and tried to turn the motor by hand. It stopped turning just before TDC on 2 and 3. Pulled the points plate for the first time. I don't see anything that looks broken.







Then I took a looked at the plugs. 1,2, and 4 look good. Number 3 is very white and I do see a tiny bit of specks on the insulator. First pic with flash, second without. Both are numbered 1 to 4 with 1 on the left.





As you can see, number 3 looks like the lean cylinder. I'm guessing it was caused by a leaky carb boot. I had the carbs off recently and assume I opened up a crack pulling them off or reinstalling them. The worse part is I've had the new boots for a week or two and was waiting for a good time to switch them out.

I'm thinking that the fact it won't turn to TDC on cylinders 2 and 3 means a piston is hitting a valve. That would mean #3 intake valve is stuck open. I'm not sure how a valve could slip into a cylinder unless the retainer broke (hot valve=hot retainer=cracked/broker retainer?). The other option would be a broken cam chain I guess. Checked everything when I put everything together in the past year and the tensioner was working correctly.

Next steps: I guess I should still look under the left side cover to see what's going on with the starter clutch area. There could be something that just happens to be stopping near TDC. I've never opened it so I had to spray the screws to loosen them (I have the Allen head screws ready to go). I'll post some pics of what I find. I think I have to drain the oil or tip the bike on its right side to do that. If nothing looks bad, then I guess I'd have to pull the valve cover and look at the cam chain. Any ideas?

One more pic from a ride 2 weekends ago for my inspiration.

[hannibal]

I got the left side cover off this morning. Comparing to the parts diagrams, everything looks good as far as I can tell. See anything funny here? I have more pics I you want to see stuff from different angles. The motor still won't turn by hand and I noticed that the flywheel behind the rotor will only turn clockwise. Is this normal?






I noticed some oil dripping off the cam chain tensioner. I'm going to open the valve cover and see what I find.

[Brendan W]

The gear behind the generator rotor is the starter clutch gear. It engages the clutch when rotating forward, anti-clock. When the motor starts the crank overtakes the clutch leaving that gear behind so it has to be free to rotate clockwise relative to the crank. Long winded way of saying it's normal.
While you are in there check that you have the correct number of washers on the intermediary gear shaft. The big silver one in the middle of the bottom pic. Most have two, one in front and one behind the gear. Some get dropped and a likely place is in behind the bottom of the flywheel. It's worth fishing in there with a magnet just in case someone left something in there.

[hannibal]

Thanks for the explanation on the starter clutch gear. One washer fell out as I pulled the cover and found the second on the dowel in the cover (you can see it in the first pic). I put it back together according to the parts diagram.

I opened the valve cover and found this.







I followed the procedure to remove the intake cam. Took off the tensioner, the idler, then the cam. The motor still wouldn't turn by hand. I couldn't find the other half of the broken bolt so I'm assuming it's down in the block preventing the cam chain from spinning. I guess I need to start reading about cam chain replacement.

Any ideas on what happened? Where should I look next? Thanks in advance for the help.

[Wingsconsin]

Ouch ...

Those pictures make me feel nauseous --

Here's hoping you get it fixed easily and quickly

[Brendan W]

Guess someone didn't apply the proper thread lock on those screws.
The missing bit could be at the bottom of the chain tunnel catching the crank sprocket, magnet might get it out.
Here's hoping the damage is light.

[hannibal]

I'm wondering if this is the cause or the effect. Not sure how both screws came out at the same time. I don't know what usually causes a cam chain to break, but maybe the sprocket screws snapped instead of the chain breaking in my case.

I'm done for the day. Back at it in the morning.

[hannibal]

Guys, I am greatly in need of advice. I've fished down in the cam chain tunnel for the other half of the broken screw. I can't find anything. In addition, I saw a small piece of black plastic (chain guide) stuck to the wall when I began fishing. Tried to pull it out and it fell down into the tunnel.

I'm at a complete loss on what to do next. I'm working outside and winter is coming. On Wednesday, I'm going out of town for a month so this is my last chance to pull the motor this winter if needed. I hope I can find these pieces once the motor is off the bike. It's so hard to see down into the tunnel with the motor on the bike. Because the motor won't turn by hand, I'm guessing the broken bits are stuck between the chain and the cup on the bottom (#5 in the parts diagram which I can't figure out how to copy and paste). If something is stuck in there, is there a way to get in there with the motor on the bike? Is it even possible to get in there once the motor's off the bike? Looking at the manual, I can't even figure out how the plastic guides are held down. Do they just slide into this cup on the bottom?

Any help is greatly appreciated.