Locked up

[Royson]

Been slowly putting my 90 1100, back together, had it running last year, but carbs were messed up, so had them rebuilt by a "pro" (quotes because rebuilder may or may not have done a competent job.)

Anyway, I finally bolted her all back together this week. Turned over fine at first, but before starting, engine locked up solid, as in: starter won't turn, and if in gear, can't turn engine over by rotating rear wheel.

First thought, maybe carbs flooded fuel into cylinders, pulled the plugs, no improvement.

Next thought, maybe starter is somehow jammed? Previous owner had bypassed the starter switch with a new wire, but I found no fault in the wire harness, so I removed the bypass wire. Will check to see if putting bypass wire back solves it.

Yes, there is oil in it, fresh. (any chance of a weird oil air bubble vapor lock up or something like that?)

A bit discouraged at the moment, so taking a few days away from bike to regain my perspective. The bike is otherwise in excellent shape, (only 6k miles) with no previous engine trouble except dirty carbs.

Will report what I find next.

[subforry]

This may seem critical but I am a little dubious about you knowing its locked up by turning the rear wheel. I doubt I could turn the engine by trying to turn the rear wheel. If the plugs were out maybe. If you sat on the bike and tried to roll it in 2nd and no go then yes something is locked up.

Not sure on motorcycles but on cars I think the starter can get fouled up can mechanically lock the engine. Maybe pull the starter and see if anything is damaged.

Also could remove the small engine cover on the right-side (where the ignition sensors are) and try turning with a wrench.

Big world of waning: Don't force anything. Maybe the timing chain slipped or broke, maybe something happened in the trans/clutch. You don't want to make a potential internal problem worse.

[Royson]

News not good

I pulled the clutch cover, and found no obvious fault with the starter, gears are engaged properly etc. With the in between gear removed, the starter spins up normally, I conclude there isn't a jam in the starter.

Put a wrench on the the main drive shaft, and found that I could rotate it 300 degrees in either direction, but then I encounter an absolute solid stop. I rotated very slowly and carefully. There is no gradual binding, the drive shaft turns freely until it reaches a solid obstacle. Putting the transmission in neutral and disengaging the clutch makes no difference. Based on this preliminary result, I conclude that the fault is not in the starter or transmission.

Next I'll look at the timing side and generator, hoping to find some obvious source of the jam.

Common sense tells me it is most likely to be somewhere in the valve train, and that is discouraging. I am a very mechanically adept person having done all sorts of basic mechanical repairs on everything from airplanes to lawn mowers, but I have never disassembled the valve train of a four cylinder four stroke engine. I just read through engine disassembly and reassembly in the Suzuki service manual. Man oh Man, lots of steps, and lots of warnings about not misaliging this or that, be careful not to misplace this or that, be sure to use this or that Suzuki approved sealant or lubricant, be sure to torque in exactly this order etc.

Of course I can turn to a professional mc mechanic, that's probably the smart thing to do, I do know a good one. I bought this bike because I needed something to keep me busy, and have enjoyed the project so far, but an engine rebuild is a much bigger challenge than I bargained for.

Here's the optimistic way to look at it. If I end up rebuilding this engine I will undoubtably learn lots of new skills, even if I screw it up. Then in the future, I'll have more tools in my mental toolbox for my current hobby of choice, motorcycle restorations.

[Dr. Acula]

Foreign Object

If you never had any problems before, I would remove the carbs and plugs, take a super bright light and see if something got dropped or sucked in. A piece of hardware or something. It could be jamming a intake valve open. The ultimate would be to geta hold of one of those micro cameras and peek inside. Maybe it could be fished out with minimum pain.

[Wild-Bill]

That does sound like a foreign object jamming up the works. Try looking in the spark plug holes while turning the engine by hand. Did something get dropped into a cylinder? Next, I'd pull the valve cover and see if the valves are all operating normally.

[Royson]

Locked up investigation

Thanks for the tips guys, I am trying to think of every possibility, it's still a true mystery, so having your help looking for clues is much appreciated.

I had rags stuck in the intake holes while the carbs were off, but took the carbs on and off multiple times while fitting them (the carb rebuilder missplaced the choke cable fitting etc.) I hadn't even thought about it, but is it possible a loose screw or washer could have fallen in the cylinder intake and gotten in the valve train? I don't think anything could have gotten in through the spark plug holes, since the engine was running before, and I hadn't removed the spark plugs in between.

This problem started out as a huge discouragement for me, but it's gradually turning into an educational puzzle. I assume the worst, something screwed up in the top end, but it will be interesting to see where the investigation leads.

I have a tiny LED inspection light, I'll see if I can spot anything through the intakes and spark plug holes.

Next, I'll pull the timing cover, don't really expect to find anything there, but it has to be eliminated as a possibility. After that, the valve cover is coming off.

I'll report my progress.

[Dr. Acula]

Save a gasket

Save a timing set cover gasket,Wild Bill is right. Pull the rocker cover and see if the valve action is correct through a rotation. I suspect you'll see a valve staying open when it shouldn't. Good Luck

[Wild-Bill]

...I don't think anything could have gotten in through the spark plug holes..

Things can get in through an open intake valve, too. It's a long shot since you'd have to get something pretty big in the cylinder to stop the piston.

Much more likely is that you've got a stuck valve. Be gentle while trying to turn the engine. A stuck valve is pretty easy to break free or even replace but if you manage to break a valve guide by bending the valve stem and then trying to move it through the guide then it's a real trick replacing the stupid thing. A machinist is going to charge you a bunch for the trouble.

[tone]

When you say putting it back together do you mean you have you stripped the engine ?
if so i'd say a valve is open due to incorrect cam timing! failing that a something has found its way into the engine as mentioned before, it could even be a small piece of rag maybe used to block inlets when engine out !

[Royson]

Locked up

I have been refurbishing the bike cosmetically, and things like fork seals and brake lines etc. I bought it running, but the carbs were gummed up, and the engine would only run with full choke. I haven't done anything to the engine, except replace the spark plugs, and have the carbs professionally cleaned.

I changed the oil and filter, put in new plugs, and reinstalled the carbs, the engine turned over normally prior to hooking up a gas supply. Then with gas it locked up almost immediately.

Beginning to think it must be a stuck valve or some other aspect of the valve train. Won't be able to dig deeper for a couple of weeks, fortunately I have other bikes that are running, I'm going on a 3 day group ride this weekend.

[scottynoface]

Or the gas tank vent is plugged

Dont know if the 1100 gas cap is vented or not.

[Wild-Bill]

A plugged up vent would keep fuel from filling up the float bowls, not keep the engine from turning at all.

Try pulling the plugs and giving the engine a crank. Based on the description you gave, I'm wondering if you're hydro-locked from leaking float valves. If the engine turns over with the plugs out and fuel sprays out of the spark plug holes then you've found your problem.

[Royson]

Latest

Couldn't be a fuel vent issue, I use a "fuel IV" in place of the tank for bench runs (a funnel to fuel line, and yes, the vac line is accounted for.)

Yesterday I had my mechanic take a quick look. The news is not good. As seen through the carb intakes, none of the intake valves move when the drive shaft is rotated. Seems that the connection between the main shaft and the camshafts is compromised. I believe the two are connected by a chain.

Will be digging deeper next week.

[subforry]

it may not be bad at all. Sounds like the timing chain is broken or off its cogs. Removed the valve cover and take a look. As long as there is no damaged caused by a valve/piston collision, then feed a new timing chain in.

[Royson]

The Mystery Deepens

Pulled the valve cover, no broken timing chain or anything else obviously amiss. The cams rotate when turning the crankshaft etc. Nothing obviously wrong with any of the valves.

Once again, the crankshaft rotates freely about 300 degrees in either direction and then encounters an absolutely solid obstacle. It is not as if it starts binding first, it turns freely, then there is a something firmly preventing further rotation.

Guess it is time to pull the generator and timing cover etc. Wondering if maybe some kind of FOD went in when I replaced the oil. Seems unlikely, but maybe there might have been some packing debris or other FOD in the oil? Hmmmm

Will report upon further investigation.