I have a 78 FLH I just completed a top end rebuild on. It starts fine but after a few minutes it starts to cut out and then stops and I am unable to restart it until it sets for awhile. I thought at first it was a fuel problem so I checked the fuel filter to make sure it wasn't clogged (I put a new one in when I did the rebuild.) and I tore appart the S&S carb to clean it. Both seem fine. Next I replaced the coil thinking it was breaking down when the bike heated up but it didn't make a difference. The spark plugs are new and the spark plug wires are in good shape. I have a body rebuild kit for the carb I'm going to install and will try re-adjusting it. Any thoughts or ideas would be welcome. Thanks.

 

Pretty broad range on this but you mentioned you could not start it until it sat for a bit....like it needs to cool down? Off the top I am thinking an electrical component (coil/alternator/stator/switch?) is heating up or maybe a wire is shorting out once the bike gets up to operating temps.

Early 78s had 3 circuit breakers, think that went up to 4 in the second half of the run. If you think it might be electrical I would take off the dash cover run it until it quits, let it cool down and listen for the familiar 'click' of the breaker resetting itself.

Another thought... have you checked to make sure the float level is set right?

 

Thanks for the reply. The bike ran before I did the rebuild and I didn't touch the carb so I'm guessing the float is set right. When I rebuild the carb I'll check to make sure. I don't here the breakers resetting so I don't think it's one of them. I replaced the coil thinking it might be the problem ut wasn't. I bought this bike in July and did the top end because the previous owner never rode the bike for eight years and it was leaking oil every where. Other than that it ran fine. Thanks again for the iput.

 

Might sound dumb, but these old bikes are funny about everything working together to run correctly... Have you re-adjusted your valves to make sure they are not to tight? You might think they are right on but when the motor heats up, they're not completely closing causing the hesitation and dying. Also make sure to do the 3 heat cycle re-torquing of your heads / cylinders while you're at it.

 

Check to make sure you have spark when it dies. I'm not sure what you have for an ignition, but if it's electronic your trigger in the nosecone could be giving you trouble. Start it up and let it run until it dies. Pull off a plug wire and put a spark plug in it, and crank it over. If you have spark, it's prolly a fuel issue. If no spark, check with a test light to see if you have +12 volts coming in to the coil. If not, you may have a problem with a circuit breaker tripping, bad wiring, etc. If you have +12 volts to the coil, put your test light on the other end of the coil and crank it over. It should flash on and off as the engine cranks. If it lights and stays lit, you have a problem with your trigger for the ignition, whether it be points, electronic, etc. When I say trigger, it may be either the crank trigger or the module on an electronic. I wouldn't bother with the valves at this time, if you had them set too tight it wouldn't start at all. When the engine heats up, the cylinders grow and the valve lash gets looser, not tighter.

 

Thanks for the inputs. I replacing the coil and started the bike up. Once again it ran for a few minutes then shut down. I let it set for a while but this time was unable to restart it. Pulled the plugs and tried to crank it over but did not see any spark. Going to try putting the old coil back on and see what happens.

 

didnt read all the posts,but are you sure you dont have a circut breaker poping? when it shuts off,listen for a "dink" in about 30 seconds,or just let it sit for about 5 min. and see if it starts & dies again,if it dose,you got a short smeplace
kirby
vee twin racing

 

If you have a test light, follow the instructs that I posted and post back the results. If you don't have a test light, go to the nearest auto parts store and buy one, it'll save you from replacing good components thinking they are bad in the future also. Once you post the results, we can help you get it fixed.

 

The bike has an electric and kick start. No electronic modules, just the three breakers. As stated earlier, It would start then sputter and shut down after a few minutes. It would run long enough to ride it around the block. If I let it set it would start again and repeat the same process. I changed the coil and it did the same thing but now I can't get it to restart at all. Pulled the plugs and saw I wasn't getting any spark. Checked the wiring and found the wires to the coil were swapped. Connected them the correct way and the bike still has no spark. Will pick up a tester tonight and see what I have then post the results. Also, none of the breakers are tripping. I appreciate all of the input.

 

Are you running points or electronic ignition.