[dtwl]

Hi all,

I've got a 1985 FXRT that seems to have a hard time starting when the motor is hot and I'm hoping to get some ideas on what the cause is before I start ordering a bunch of parts I don't need.

Symptoms:
When the motor is at operating temperature, the starter has a hard time turning over the motor. This gets progressively worse on subsequent starting attempts unless the bike is run long enough to charge the battery back up. The bike turns over fine when the motor is cold.

Here's a video of the problem:

http://imgur.com/a/Y9PXa3e

What I know:

• The battery is brand new, less than 5 months old. It has 270 CCA which seems like it should be plenty to turn over a stock-ish evo.
• I've tested the charging system and it's working. The regulator is brand new and a multimeter shows 14 - 14.5 V going into the battery when the motor is at 2000 rpm.
• The motor definitely had work done to it, but I don't know what. The bike had adjustable pushrods and non-stock valves when I replaced a head gasket over the summer, but it doesn't feel crazy powerful. It could be higher than stock compression, but I have no evidence to support this and there are no compression releases anywhere that I can see.

My Question:
Is this my starter giving out or do I need a battery with more cranking power? Both? Neither? And whatever the solution is, why is it happening so I can more successfully troubleshoot this in the future.

Thanks!

 

[dtwl]

Thanks for the pointers, everyone. I've had the battery load tested at the local auto parts store and it came back as a good battery. I also did a voltage drop down test per my service manual and things are a little murkier there. The voltage drop going from the relay into the solenoid is 0.09-0.13V, but going from the solenoid into the starter is 1.0 - 1.3V. The starter ground circuit drop is 0.09-0.13V. Additionally, since someone suggested trying a higher CCA battery I swapped in the 320 CCA battery from my Dyna and the problem doesn't manifest with this battery. I tried 10 start attempts and the starter turned the motor over just fine and the bike started each time.

The naive conclusion here might be that I need a 300+ CCA battery, but the voltage drop down test I did suggests that the solenoid isn't performing as well as it should. Did the bigger battery just paper over the real problem?

 

[dtwl]

Got busy with holidays and stuff but I wanted to check back in here. I cleaned all the connections really well and tested at the solenoid terminal. Voltage drop was better than before but still too high, around 0.5V. I've got a rebuild kit from J&P cycles and I'll see how it does after rebuilding the solenoid.