Can only crank the engine a part of the way

[lettuceman44]

Hello everyone,

I have a 1982 GS450L, and when I bought it the motorcycle ran.
Cleaned the carbs, replaced gaskets, fixed up the electrical, and I was finally ready to start her up.

Pressed the starter button, engine would crank. It never started but would crank. I pressed the starter button a few more times, and the engine would crank. I pressed it again, except because I'm an idiot I pressed on the starter button for too long. After that, the starter wouldn't crank the engine anymore.

If I go to hand crank it, I couldn't do it. I tried cranking it backwards, and it moved....until it hit a spot where you couldn't do it anymore. I was then able to crank if forward again, but only up to a certain point.

So essentially I can crank it forward and back in a small range of motion, until I hit massive resistance.

I looked through the spark plug holes, and I can see the pistons moving, so it doesn't seem to be seized.

Ideas for causes?
What should I look for in fixing this. Nothing seems out of place, and I don't think I dropped anything (although I guess the only way to know for sure is to open it up).

edit: I forgot to mention that I checked the gears in the crank case on both sides, and nothing popped out or anything.

 

[Nessism]

Did you remove the cam chain tensioner or mess with it? Have you adjusted the valves yet? Reason for asking is it seems like the cams are out of timing and a valve or two is now bent.

I'd pull the valve cover and check the cam timing. Also check the valve clearances at the same time. If you find a valve with a bunch of clearance it's because it's bent.

 

[lettuceman44]

Did you remove the cam chain tensioner or mess with it? Have you adjusted the valves yet? Reason for asking is it seems like the cams are out of timing and a valve or two is now bent.

I'd pull the valve cover and check the cam timing. Also check the valve clearances at the same time. If you find a valve with a bunch of clearance it's because it's bent.

Nope, I haven't touched any of that stuff.

I did just check the timing, it seems off. On the ignition timer, the T isn't directly underneath the line. If I have the 2 pointing straight up on the intake cam, the mark at the ignition timer is in-between the R and what looks to be another I.

I'll check the valves, thanks for that tip.


Oh, and in case it matters, I've been doing all this with the engine in neutral.

edit: I won't have my feeler gauges for a few days -_-

Should I fix the timing and try again, or should I just be patient and wait until I can check the clearances.

After typing that out maybe I should just wait to check the clearances.

 

[TxGSrider]

Will it turn by hand with the spark plugs removed? If so, are either of the plugs really wet (like maybe the carbs flooded and hydrolocked one of the cylinders)?

 

[tom203]

"...I go to hand crank it, I couldn't do it. I tried cranking it backwards"

does this mean you turned engine backwards (opposite its normal rotation)?

 

[lettuceman44]

"...I go to hand crank it, I couldn't do it. I tried cranking it backwards"

does this mean you turned engine backwards (opposite its normal rotation)?

Yea, I cranked it counter clockwise.

 

[lettuceman44]

Will it turn by hand with the spark plugs removed? If so, are either of the plugs really wet (like maybe the carbs flooded and hydrolocked one of the cylinders)?

Everything I posted was with the spark plugs removed.

When I took them out, they weren't wet at all.

 

[TxGSrider]

Everything I posted was with the spark plugs removed.

When I took them out, they weren't wet at all.

Ok, then I really don't have any ideas. It does kinda sound like it jumped time. I suppose about the only other thing I would check before I pulled the head, would be to remove the starter itself from the motor just to be sure it wasn't somehow bound up.

 

[Nessism]

Sears sells feeler gauges. You don't strictly need metric.

The way to check timing is to align the 1-4 T mark on the crank and then look at the exhaust cam 1 mark. Your service manual details what to do.

 

[lettuceman44]

Sears sells feeler gauges. You don't strictly need metric.

The way to check timing is to align the 1-4 T mark on the crank and then look at the exhaust cam 1 mark. Your service manual details what to do.

That's what I get for not reading closely.

Yea, the 1 mark points below the gasket surface. It might not be within the 1-2mm range, but its not too far out, so I wouldn't think timing would be the issue.

 

[Nessism]

1-2 mm off should be okay. Next, count the pins between the cams and compare to the spec in your manual to see if the intake cam is also good.

 

[lettuceman44]

I meant it looks passed 2mm. Like 3 or 4 mm.
I already checked the pins as well, 18.

So I did a bit more investigative work. I did find a .025 mm feeler gauge, so I decided to check the valves out. Didn't fit in any of them with the cam lobe pointing straight up. Looks like all four shims need replacing, but I cannot do that until I get more feeler gauges, which I have. I just have to wait for the person to come back with them

I also noticed that the "stopping point" is when the left and right piston is all the way to the top. So I can turn the engine counter clockwise until the right piston makes it to the top, and I can't crank anymore, and I can crank it clockwise until the left piston is all the way to the top, and I can't crank anymore.

Looking through the spark plug hole, I think the valve(or whatever I'm looking at, not exactly sure) is hitting the top of the piston?

So I was following the right piston. This is the sequence of events starting from the first stop point.

Ignition Timer has the T lined up with the engine marking. Seems it is at TDC. I look through the plug hole, I can see the piston very close to the top. Seems to be touching what I guess is the valve.

Start cranking the engine forward.

Piston moves down, back up, down again, until I can't move anymore.

The other piston is now at the very top.


I don't know if any of this is useful, but trying to share as much info as possible

 

[dantodd]

These engines are interference engines. That means that if the running is off the valves and poisons collide. That is what it sounds like is happening. At least one of the valves are not fully closed when the piston reaches TDC. Usually the first time this happens when the engine is running or the starter us engaged there is damage done. Either the valve seen gets bent, the piston gets holed, or both. At this point you probably need to pull the head to get any further information.

 

[lettuceman44]

GUYS I FIGURED SOMETHING OUT.

You are indeed right that I will need to pull the head. I took off the camshafts, and peered down into the engine, and guess what I find. Something black is stuck to the bottom gear. Looks rubbery.

I wonder if it is one of the end cap rubber half moon things......

So looks like I need to take the head off and clear that out. Can check the valves at the same time then and hope for no damage.

Gonna save taking off the head for tomorrow.

 

[dantodd]

With any luck it only chewed up the half moon and the valves haven't been bent,

 

[Nessism]

I'd try to fish that thing out before pulling the head.

 

[dantodd]

I'd try to fish that thing out before pulling the head.

If you get it out check the cam timing while manually turning the dank before you hit the srarter. The cam gears could have slipped because of the jam. Move forward carefully from here.

 

[lettuceman44]

Since I took the camshafts off I'll have to retime it anyways, which honestly makes me feel better because I trust myself more than the previous owner

I have no idea how to fish it out with tools in hand. I guess I'll try to rig something up. Need to find a nice rigid long apparatus.

Is the reason for fishing it out first is to potentially save time by not having to take the head off?

If the valves are bent, will it keep the engine from turning? I don't want to risk more damage. Is it safe to crank the engine once I fish that piece out?

 

[Nessism]

Pretty sure the valves are not bent. If they were you would have a bunch of valve clearance because the valve wouldn't seat.

 

[lettuceman44]

Pretty sure the valves are not bent. If they were you would have a bunch of valve clearance because the valve wouldn't seat.

Good point haha. Thanks for the help, let me try to fish that bugger out.