bike gets hot - stops running

[don_gibb6512]

After 5 years of working on/off on my 1980 GS1100ET, I finally get it road worthy and it won't stay running more than twice around the block. Once the bike gets hot, it stops running. I let it sit for a few minutes and it starts right back up. It's strong and smooth when it does run, albeit a bit rich. Here's the history:

Bought the bike off a friend, not running. Cleaned it up, rebuilt the top end with new rings, honed cylinders, cleaned up head and valves by a machine shop. Standard size rings as both cylinders and pistons were well within spec. No leaks anywhere at this point. Compression is at 145, 140, 135, 148 (1-4). Not great but acceptable. Valves adjusted to mid point in the range. Accel coils and wires. Kerker 4-1 pipe and header with Mikuni 34mm RS Flat Slides and K&N pods. Plugs are pretty darn smoked after a couple times around the block so it's definitely running rich, but it's much smoother and stronger than the GS1000G 8-valve motor that I had been riding. I've swapped out the ignitor unit and generator assy. (pick-up coils) with known good ones off the GS1000G. Both bikes are 1980 and those part numbers are identical. Pingel fuel valve flowing a river of fuel and bowls are full when the bike shuts down. Bike always starts with the first press of the button. I've gone over the entire wiring harness and all grounds are solid and connections are clean. The only strange thing was when I took off the timing cover there was quite a bit of metal shavings collected at the bottom of the case where the generator assy. mounts. I have no idea exactly where that's coming from but it bugs me. I'm pretty much at a loss as where to look at this point. Any and all suggestions will be greatly appreciated. Thanks.

[rpickle]

Hi Don. Glad she is up and runnin'! When it dies, will it crank? Also does it have spark when it dies? Sounds like you have fuel.

Not much help. Hope you get 'er figured out.


Rick

[chef1366]

You add fuel with the choke circuit when cold. Do you need choke to start? If not I'd say you are running rich and drowning the motor when hot. Sounds like rejetting is in your future.

[MissFabulous]

If it will start after it's cooled off a bit, then it could be the CDI. It's not all that common for them to go from what I hear, but a new (used) one solved the 4 minute max running time on my 550. If yours is anywhere near where mine is, it's a PITA to get to, but can be done with some ingenuity without tipping the bike on its side as was suggested. If you end up going this route, PM me and I'll go back and figure out the sizes of the tools I used to make it work. It's just phillips head screws, but they're in no man's land on my bike anyway.

To diagnose this, I think basically you want to test for spark when the engine is still hot. If you still have spark when it's hot, then it's probably something else. Hopefully someone will elaborate better than I can. With my 550, it was the PO who diagnosed the problem and I installed the replacement part, so I don't know too much about what troubleshooting was done ahead of time, but if you search the tech forum you'll find some info that sounds similar to your condition. Here's more info on CDIs in general, but not specific to Suzukis http://www.dansmc.com/cdiignition.htm

Hope this helps and doesn't lead you off on a wild goose chase... :-\"

[gustovh]

I had an electrical connection that once it got hot opened and shut everything down, took many tries and several months to find it. Turned out to be right under the tank above the valvecover.
V

[don_gibb6512]

Thanks for all the suggestions. The bike cranks after it shuts down abruptly but won't start. I've replaced both ignitor unit (ignition module) and generator assy. (pick-up coils) with known good units so that's not it. It does need choke to start and run when it's cold. It may be an open happening in the wiring after it gets hot but I'm not sure how to find that. By the time I could get the spark plug out and test for spark after it shuts off, it would start up and run anyway so it's bound to have spark by then. That's real frustrating as I would love to be able to test for spark at that point but it cools off just enough during the time I'm fiddling with the plug wire, plug socket and not burning the skin off my hand trying to remove the plug. It just occurred to me that I could clamp a timing light on one of the wires and see if I get any light. That should tell me if it's "fire or fuel".

Would running SO rich cause the bike to just shut off like it's doing? It doesn't back fire when it starts back up which is why I didn't think I was flooding the cylinders with gas and the plugs aren't wet, just smoked like when you leave the choke on too long.

Thanks for all the suggestions and "keep 'em coming" cause I can use all the help I can get. I am SO close with this bike.

Don

ps. Rick, I should be around this weekend if you want to swing by and take a look at this bike, all put together. It's way different than the stripped down version that was on my back patio. :-D

[nabrams]

If it doesn't need any choke at all to start from stone-cold, then I'd say you've got a super-rich situation. When the bike warms significantly the mixture gets even richer. But, the fact that it's a sudden shut-down also points to the possiblility of sudden loss of ignition. So, yes, I guess putting a test light in the ignition circuit would allow you to know one way or the other.

[egent]

By the time I could get the spark plug out and test for spark after it shuts off, it would start up and run anyway so it's bound to have spark by then. That's real frustrating as I would love to be able to test for spark at that point but it cools off just enough during the time I'm fiddling with the plug wire, plug socket and not burning the skin off my hand trying to remove the plug. It just occurred to me that I could clamp a timing light on one of the wires and see if I get any light. That should tell me if it's "fire or fuel".

The other way to test it is to have a screw driver with a have plastic handle. Just pull the spark plug cap, place the screwdriver in the cap and make connection with the electrode, and then hold the screwdriver close to the engine and check for the spark. No need to pull the plug at all.

[chef1366]

Bring an extra plug. Take a pic of the spark plugs after it stalled. I bet they are rich.

[t3rmin]

I really don't see how this could be a fuel delivery issue. It's gotta be electrical. Unless perhaps a float valve was overflowing and flooding it you wouldn't see anything this dramatic from a mixture issue. You could check for an overflowing float by leaving it on prime on the centerstand for a few hours and see if anything drips.

I had a very similar issue which kicked my butt for a while with the 650. What fixed it was running a direct 12v feed from the battery to the coils, switched via a relay and the original feed. Actually I replaced the plug caps around the same time so it coulda been that as well. New NGK plug caps cheap at www.z1enterprises.com.

[don_gibb6512]

Plugs are rich alright. I'm going to try to lean out the mixture and raise the needle one position to correct for that but when this bike runs, even as rich as it is, it's smooth and strong. I'm going to test for 12v to the coils tonight, as well as all other connections in the ignition circuit. I'm also going to throw on a timing light and that should tell me if it's getting spark after it stalls.

Thanks for all the input and keep 'em coming. I appreciate every one.

[smagnusen]

I think raising the needle makes it richer?

[don_gibb6512]

I meant raise the needle clip one position. Going from 4th position to 3rd. Yes, raising the needle makes it richer. Raising the needle clip lowers the needle and hence makes it leaner. Sorry for the confusion and thanks for catching that.

[pano]

maybe you could try one of these in line ignition spark testers.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=4445

[arveejay]

Sounds like the wrong ohm coils are installed.