difference in starter solenoids?

The solenoid on one of my bikes went out last weekend. Being that I would rather replace it with a new one then an ebay 40 year old one, I ran to the local autozone and picked one up for an 86 ford bronco, the first thing I thought of with an external solenoid. This bike is also running a small 4 cell battery. With the original kawi starter solenoid that battery could crank a solid 30 seconds without dimming the headlight at all, and now this new one can barely turn it over a few times.

Chalked that one up to the small battery thats not really supposed to be used with an electric start.

On another bike I got tired of kicking this weekend, I decided to put an electric start on. Grabbed another one of the same Bronco solenoids, as this one has a new full size battery on it. Wire it all up, same result, barely a few cranks, dimming headlight, etc.

Do auto solenoids require more amps then the bikes can deliver? Or do I have something else weird going on?

Can anyone recommend a good universal solenoid that can crank these 750 twins like the OEM ones did?

Thanks.

Im running one of those on my cb750 and have never had a problem with it. Not sure what to tell ya except it sounds like a possible wiring problem.

Rick's makes universal Kawi and Honda style solenoids. Set you back thirty or forty bucks. Any bike shop can get them.

A typical bike solenoid draws 2 - 3 A when closed. A typical car solenoid draws 5 - 10. Seeing as it was designed to power a big engine (even for a car), that Bronco solenoid might draw north of 10. Those few extra amps can be all the difference between the starter spinning fast or slow and the ignition firing or not. Some bikes have enough spare juice at cranking that they'll hardly notice. Some will need all the help they can get.

Seeing as you have two bikes, it should be pretty easy to test whether each solenoid is drawing too much current by using the other bike's battery to power it.

Originally Posted by planningoncrashing

Rick's makes universal Kawi and Honda style solenoids. Set you back thirty or forty bucks. Any bike shop can get them.

A typical bike solenoid draws 2 - 3 A when closed. A typical car solenoid draws 5 - 10. Seeing as it was designed to power a big engine (even for a car), that Bronco solenoid might draw north of 10. Those few extra amps can be all the difference between the starter spinning fast or slow and the ignition firing or not. Some bikes have enough spare juice at cranking that they'll hardly notice. Some will need all the help they can get.

Seeing as you have two bikes, it should be pretty easy to test whether each solenoid is drawing too much current by using the other bike's battery to power it.

I should have mentioned, on both bikes they crank fine when hooked up to the battery charger, even with it set on a 2amp slow charge, although the smaller battery bike likes to crank on the 12a setting more.

I guess they are just slightly too big for my applications Sounds like im in the market for 2 new solenoids.

You're battery doesn't have the cranking amps necessary to turn the bike over. The solenoid is just a magnet switch that collapses and completes the circuit from power to starter. Your battery may be fully charged, but it doesn't have the amperage to get the job done. Replace your battery and your problem should go away.

Technically a solenoid is an electromagnetic relay designed for short-use, high-current applications.

A good way to test whether it's the battery or solenoid is to jam a screwdriver between the two contact posts of the relay. If the bike cranks nice and good, your solenoid sucks. If it doesn't crank well, then replace your battery and try the test again to check the solenoid.

A solenoid is a device that converts electrical energy into linear motion. Some starters have a built-in solenoid that causes them to engage, but typically the term "starter solenoid" refers to a solenoid that closes a high current switch to supply power to the starter. Some vehicles also have a starter relay (a relay itself being a specific sort of small solenoid switch), which provides power to run the starter solenoid, as some require north of 10A, and that alone requires a fairly heavy switch.

Back to the point... If the bikes crank over fine on a charger, that means you're just shy on power. Sounds like a couple of amps on the bike with the big battery, and a good few on the one with the small battery. You can either replace the solenoids with some that require less current or replace the batteries with some that provide more current. Seeing as solenoids are cheaper than batteries, it's no fun trying to fit a bigger battery in a bike, and adding amps means increasing the electrical load overall with no real benefit, I'd recommend replacing the solenoids.

Again, Rick's makes them. Thirty to forty bucks. Get them (probably a special order) at pretty much any bike shop. Everybody gets stuff through Parts Unlimited and/or WPS, and both have them.

You might look into wiring in starter relays as well, especially on the bike with the small battery. Use an SPDT relay to switch the headlight off when the starter is cranking. If you're running the headlight, that's anywhere from 3 to 5 A you're giving up that could be powering the starter.

this is what im runnin. $8 at autozone, built in solenoid.