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Discussion Starter · #1 ·
I have a 1978 Yamaha XS750. Since it is nice out I have decided to take it for a ride. It reminded me of the issue I was having. The starter motor, when I press the start button, doesn't quite crank it fast enough to start when it is cold. I end up having to use the start to prime it then kick start it. It kick starts right away on the first or second kick. After it has warmed up, the push button starter starts it with not much issue. (Yes, the battery is charged and good).

My question is would cleaning the starter gears do anything and can I clean the starter motor and make any difference? Or, is it just what it is?

Thank you.
 

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If your starter motor is like the one on my '70 CB450, it has a gear train at the business end. and fresh grease may improve things. That said, when I start with the electric start in the cold, I use one of those clip-on booster batteries, and it spins up really fast. If it doesn't fire quickly enough with that, I'll get out the jumper cables to a non-running car battery, so I can crank it for more than 10 seconds at a shot. Over 30 seconds, and you have to let the starter rest a while.
 

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Cleaning the starter motor out would be a good thing as it's likely had 44 years of crud built up inside .
Alongside that , be sure to disconnect all electrical connections and clean them to a bare metal shine . Then reconnect them being sure they are scratch tight . That includes all ground points .
 

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Note that the parts diagram doesn't show if there are any gears inside the motor, just those that drive the sprag clutch. It doesn't even show the brushes or other parts inside, treating the motor like a 'black box'. My motor looks like that, and has a sun-and-star reduction gear inside the output end. Yours may also, but looking at the diagram for the motor itself, it may not: https://www.partzilla.com/catalog/yamaha/motorcycle/1978/xs750e/starting-motor If it does, they are inside the unmarked housing at the output.

Clean connections are important, especially the battery cables. I have a battery CCA tester, and on a lark, connected the ground lead to the engine case, instead of the battery negative. The test showed an over 20% drop in CCA measured, compared to directly across the battery. So, I disconnected the heavy ground lead at the frame/transmission and cleaned it thoroughly with contact cleaner. After that, there was still a small decrease in the measurement, and cranking speeds went up quite a bit.
 

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Discussion Starter · #7 ·
That you for the tips. I would bet it is a dirty connection. Everything is original except a few things I've replaced. The issue seems to have gotten worse over time. I'll give all the grounds a cleaning this weekend and see the results. If still not better than I'll take the starter off and give it a good cleaning.
 

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Yes to the reduction gears up inside the nose casting, it is shaped for it and the double shaft ends showing there indicate another short shaft inside the nose, needed if those gears are there.

OP you should know if the motor is original it will likely be full of all kinds of filth inside it.
 

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Discussion Starter · #9 ·
It has been a long time but felt like I should give the conclusion in case someone else comes looking.

It was the battery 🤦‍♂️. The battery held charge but just wasn't giving enough push. A couple months or so later, the battery didn't hold charge anymore. I replaced the battery and it starts right up with no issues what so ever. I did find that I used too big of idle jet and was running a little rich. So, that is a positive at least.

In conclusion, check the battery if you have the same issue as me.
 
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