Motorcycle Repair: 1990 CBR1000F wont start on starter motor, poor conductivity, solenoid starter

Question
Mark
Thank you for your reply
I have the same problem when I connect a battery directly to the starter motor i.e. no electrics or solenoid involved. The problem exists when I use a good car battery, so I know it is not a bad battery.
I have already replaced both starter motor and starter clutch. I suppose since both of these were second hand either could be faulty. The voltage across the starter motor coils is within guides from the Haynes manual.
Given the prices of new starter motors (£495) and starter clutches (£195) I am reluctent to buy these and find they have still not fixed the problem.
Thanks
Greg Kirkness
greg.kirkness@gmail.com
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The text above is a follow-up to ...

-----Question-----
Greetings
Recently my CBR1000F has been failing to start on the starter motor. It starts fine with a bump start, and runs 100% once started.
I have put new plugs in, and also replaced the starter with another one I got from a wrecker.
When I hit the starter switch, the motor turns over slowly, not fast enough to generate spark. With all four plugs out the motor spins fast enough for spark. The voltage across the starter terminals falls to 8v when engaged. I have also put in another starter clutch from another engine.
It almost seems that their is something binding internally within the engine, causing the slow turnover. This is further supported by the bike starting sometimes when cold, but failing to start when hot immediately after turn off. Maybe heat expansion of something contributing?
Do you have any thoughts?
Sincerely
Greg K
-----Answer-----
Hi Greg,

Other things to check that come to mind are starter solenoid, starter button, and starting circuit conductors/connectors.

Inspect all for corrosion, loose connections, dirt/grime, and other evidence of poor conductivity.

Inspect starter solenoid for evidence of pitted or burned contacts.

Check starter motor brushes for excessive wear.

FYI... I return tech files by email. There was no email address with your question as requested and explained in my instructions. See sample tech files below. If you want others, reply with an email addy.

Respectfully,
Mark Shively



Starter Solenoid Testing & Repairing 101
By Mark Shively

Check the Starter Solenoid by isolating it from other components (disconnect small electrical wire). Check the primary winding by connecting a VOM (multimeter, Ohm meter, or continuity tester) to the small, 12 VDC wire. You should have continuity or little resistance (if any) when connecting meter test leads to the single wire and its metal body (ground) with engine off.

The larger terminals on the solenoid are tested by listening for the "click" sound when starter button is pressed while starting engine. What’s happening when you hear the click is the solenoid is an electro-magnet. When the starter button is depressed, battery voltage through the small wire creates a magnet effect inside the solenoid. This attracts the high current contact (a spring loaded T-shaped contact inside the solenoid) to travel upwards and connect with the two large exterior terminals on top of solenoid (heavy cable leads 10 gauge wire). When this connection is completed, current flows to the starter motor for starting engine.

Another bench testing method is to connect the solenoid's small 12 VDC lead to a 12 VDC battery source while grounding the solenoid body. Watch, feel, and listen for the solenoid "click and jump" when voltage is applied. This test verifies total solenoid performance.

High current contacts may become pitted or burned by arcing. This is normal wear. In severe cases, pitted and burned contacts may cause starting problems. The solenoid may be disassembled, inspected, and repaired, though internal parts are not sold separately. Disassembly requires de-soldering and re-soldering of the small wire from the solenoid cap, and bending metal retainer tabs before cap removal is possible. Once separated and opened, clean and file the contacts to restore performance. There are only a few parts to the solenoid; cap, body, T-contact, and contact return spring (not counting primary wire).

I prefer to use dielectric grease on electrical connections such as multi-connectors and bullet type connectors. Dielectric grease helps to prevent shorting due to rain and washing. It also helps to prevent formation of corrosion.  

Answer
Hi Greg,

I would need to inspect the parts to know if the parts are in good condition.

It's possible that you received used parts that need attention.

You're doing well by investgating the problem and not just buying new parts in hopes of repairing the problems. Always verify parts are defective before replaing parts.

I'll send tech files to your email addy.

Respectfully,
Mark Shively