Battery straight to starter?

agunn

agunn

Active Member
Hey guys! I'm unsure if my cb750 is in running order or even making compression. Kick starter is locked in the upright position!! :/

I can roll the bike back a forth without a problem and have even had the head off to see the valves move..

Someone told me to try and hit it with a car battery straight to the starter?? Is this safe? Have you guys tried it? Is there a better way?



The guy who owned it said that it ran before he sent it to the shop to get a head bolt retapped. The starter button itself only worked every so often (guessing he had a bad button or something in the wiring) and would only kick start it.

Help!
 
Battery straight to starter?

First thing I'd do is ensure its not seized, take the plugs out, put it in gear and see if the engine turns over, if it does then you can continue on.
This will prove that the kick starter is jammed and not the engine. Then I'd look at the electric start, check the button by bypassing it, also check the relay. It's a very simple circuit
Connecting a car battery is no problem assuming you have a 12v system. However until you can get some of the basics sorted (like get it cranking) it won't help.

Cheers
 
Battery straight to starter?

singkiwi said:
First thing I'd do is ensure its not seized, take the plugs out, put it in gear and see if the engine turns over, if it does then you can continue on.
Click to expand...

Do I look down the spark plug hole to see this?? Do I pull the clutch in?
 
+1 on ( singkiwi's ) Advice


Pull the plugs, put the bike in gear, do not pulling the clutch, And roll the bike. If the Pistons move up and down that means it is not seized and like stated above only the kicker is seized.
 
The reason you take the plugs out is to eliminate the compression that would build up when trying to turn the engine over by hand and make it easier, as well as give you an opportunity to peek inside with a flashlight.

You can do this with the bike on a center stand or jack - put the bike in gear and use the rear wheel to turn the engine over (put it in 5th gear if you can).

The fact you've seen the valves move suggests you've already rolled the bike while in gear. Also, how did you remove the valve cover (or do you mean the tappet covers - the 8 little round access covers)? The valve cover itself cannot be removed with the engine in the frame on the CB750 sadly.

With regard to connecting the battery directly to the starter - first, make sure whatever battery you use is grounded to the bike frame or engine. Doing this is just bypassing the starter solenoid. There are no fuses between the battery and the starter motor. The starter button just sends a low amperage 12v signal to the solenoid, which is an electromagnetic switch. It then connects the thick gauge wire from the positive terminal of the battery to the starter motor. The starter draws a lot of amps from the battery requiring the thicker wire, and it would fry any switch it went through smaller than the solenoid.

It's fine to do this, but only if the engine is turning over freely, the valves are adjusted properly, the timing is good, you've installed fresh properly gapped plugs and you have fuel and air coming through the carbs properly.

Without all that, there's zero point in trying to fire up the engine.
 
Battery straight to starter?

Just n update- I got real sick last night but this has been on my mind and I couldn't resist getting enough strength to take the plugs out and look to see if the piston moved.

Good news!! They moved without any hiccups..

Can I ASSUME that it is a kick starter issue??


Thanks again for all of your help!! I've done everything to a 70's Honda 10x's over but have yet to mess with motors. I just can't muster up enough courage to trust myself working on motors haha
 
Could be - might be that it hasn't been used in 30 years and is just gummed up.

I never hesitate to tell people with SOHC4 Honda's to sign up at the SOHC4 forums - http://forums.sohc4.net/ - you might find some specific knowledge there about a locked up kickstarter.

It's an awesome forum dedicated to these Hondas and was my first online motorcycle forum to be a part of. It inspired me to fire up DO THE TON 6 years ago for the more general cafe racer etc. scene. My first bikes were the 750, 500 and 550 4 cylinder Hondas.
 
Oh - and I'm assuming it's a SOHC4 CB750 - what year is it?
 
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