Sprint Sounds Like The Usual Hot Start Issue But Isn't

Chip 1050 Sprint Fighter · Jun 2, 2024

Good day

Ive got a Sprint ST 2012.

I had this bike for 4 years now, and havent been able to figure out what the problem can be, and where to go from here.

The long and short of it, is the bike won't start after a short ride out at operating temps, or after it has been revved at operating temps(not to the limiter). The starter engages, but it hard to start and starts like the battery is dead

Here are the things that I've tested, checked and changed or fitted new parts. I have run the Haynes workshop manual up and down looking for answers.

New stator
New rectifier/regulator
New Battery with higher CCA than original
New Starter
New Wires and thicker guage than standard to and from starter

Shims are in spec as per haynes manual

Now for the long explanation:

I can have the bike idle for 10min and would be able to switch the bike off and on and be able to start it up without any issues. The fan would have swithed off 2 or 3 times, with IR temp guage the water temp is close to 100 deg c in radiator, engine casing is 80deg, starter is 38deg

When I take it out for a ride and come back after a 5 kilometer ride in the cold evening it wont start if i kill and try to start her there and then, only after about 30min of cooling it would work. Radiator is 98deg, Engine casing is 76deg and starter is at 36deg after the ride.

Today I tested her Idling again with all the previous specs and temps, switched her off and back on with no issues to start. Started her back up and revved for about a minute at different ranges. Killed her and wasnt able to start her after the revving, the same scenario as I would have if I was to take a ride out.

The only thing my head is telling me is that this might be an ECU issue, but I cant see it being that

Thank you

Aidan · Jun 10, 2024

Chip 1050 Sprint Fighter said: ↑

Good day

Ive got a Sprint ST 2012.

I had this bike for 4 years now, and havent been able to figure out what the problem can be, and where to go from here.

The long and short of it, is the bike won't start after a short ride out at operating temps, or after it has been revved at operating temps(not to the limiter). The starter engages, but it hard to start and starts like the battery is dead

Here are the things that I've tested, checked and changed or fitted new parts. I have run the Haynes workshop manual up and down looking for answers.

New stator
New rectifier/regulator
New Battery with higher CCA than original
New Starter
New Wires and thicker guage than standard to and from starter

Shims are in spec as per haynes manual

Now for the long explanation:

I can have the bike idle for 10min and would be able to switch the bike off and on and be able to start it up without any issues. The fan would have swithed off 2 or 3 times, with IR temp guage the water temp is close to 100 deg c in radiator, engine casing is 80deg, starter is 38deg

When I take it out for a ride and come back after a 5 kilometer ride in the cold evening it wont start if i kill and try to start her there and then, only after about 30min of cooling it would work. Radiator is 98deg, Engine casing is 76deg and starter is at 36deg after the ride.

Today I tested her Idling again with all the previous specs and temps, switched her off and back on with no issues to start. Started her back up and revved for about a minute at different ranges. Killed her and wasnt able to start her after the revving, the same scenario as I would have if I was to take a ride out.

The only thing my head is telling me is that this might be an ECU issue, but I cant see it being that

Thank you
Click to expand...

I have had the same problem and it has re-appeared a few times. It is the ony thing that would make me give it up. Anyway, some things i did:

1) new regulator. Apparently, it is worth getting the original re-wired ratehr thena buying a new one, but have not tried it
2) check and tighten earth connection (in a pretty inaccessible place at top of engine behind cylinders)
3) make sure power and ground to battery is the actual wire connected to the terminal (I had a connection fro DRLs and trickle charger ring connectors underneath the battery ring connector - it didn't like this. Odd).
4) stop using a trickle charger - if you are leaving it for extended periods, disconnect battery. Even if you leave connected and there is no alarm or parasitic draw, it will retain charge for ages. I have not had the problem sinc eI stopped using the trickel charger

Anyway, may help.

Chip 1050 Sprint Fighter · Jun 12, 2024

Aidan said: ↑

I have had the same problem and it has re-appeared a few times. It is the ony thing that would make me give it up. Anyway, some things i did:

1) new regulator. Apparently, it is worth getting the original re-wired ratehr thena buying a new one, but have not tried it
2) check and tighten earth connection (in a pretty inaccessible place at top of engine behind cylinders)
3) make sure power and ground to battery is the actual wire connected to the terminal (I had a connection fro DRLs and trickle charger ring connectors underneath the battery ring connector - it didn't like this. Odd).
4) stop using a trickle charger - if you are leaving it for extended periods, disconnect battery. Even if you leave connected and there is no alarm or parasitic draw, it will retain charge for ages. I have not had the problem sinc eI stopped using the trickel charger

Anyway, may help.
Click to expand...

Sorry for not putting that info in, but had the stator rewound as it was said like you hear that the original doesnt last long. Had the original one rewound with thicker wire. Apparently that works wonders.

I actuall have extra cables that run to and from the starter itself, and actually had on the previous starter fixed a earth wire directly to the brush inside the starter to ensure there wasnt any way it could be an earth issue.

I can have the bike stand for 5 days without any chargers or anything connected to it, it will fire up without hesitation. This afternoon I took her out around the corner and back, didnt let her get up to temp as an experiment. there and back was 3km's max, and she doesnt start. But i can have her idle for 20mins with the fan kicking in and out without an issue starting her after that duration. Its almost as if reving is the on and off switch for starting