Author Topic: CB750 starter motor failing -- now w/pics (Read 15342 times)

brandEn · « **on:** January 20, 2012, 07:02:50 PM »

Does anyone know what the symptoms of a failing starter motor could be? It seems to me either it works or it doesn't. I have replaced my starter clutch, rebuilt my starter solenoid, and have a fresh battery but my bike still has a hard time cranking over. The starter seems to be disengaging when I crank it over especially when it cold. My carbs are synced perfect, ignition is new and working great, timing is correct. Could the starter itself be the culprit?

MoMo · « **Reply #1 on:** January 20, 2012, 07:07:02 PM »

brandEn, have you made sure the cables are good and all contacts are clean? Slow cranking could be symptomatic of a faulty starter. Could be as simple as disassembling and cleaning-ran across that once...Larry

brandEn · « **Reply #2 on:** January 20, 2012, 07:11:41 PM »

All my cables and contacts are new. I replaced them all during my rebuild. Its not slow cranking the starter just seems to slip or disengage. Seems like the starter clutch but like I said the springs, caps, and rollers were just replaced. I am pretty sure its not spinning on the shaft either but hell maybe I am wrong. I was wondering if maybe the brushes or something else is on its way out.

mrrch · « **Reply #3 on:** January 20, 2012, 07:15:07 PM »

The only place it is possible to slip is the starter clutch, sometimes the hub where the rollers engage on wears out.

brandEn · « **Reply #4 on:** January 20, 2012, 07:42:30 PM »

hmmm, that would be the starting gear then and those are not available new. Wonder if this could be the prob.

scottly · « **Reply #5 on:** January 20, 2012, 08:31:28 PM »

Make sure the alternator rotor is not spinning on the end of the crank; it happened to me before.

brandEn · « **Reply #6 on:** January 20, 2012, 08:33:43 PM »

How did you verify it was doing that and what was the fix?

scottly · « **Reply #7 on:** January 20, 2012, 08:49:27 PM »

You might try putting a mark on the bolt and the rotor hub, then after the problem happens, pull the alternator cover and see if they are still aligned. When it happened to me, it was obvious. As far as fixing it, inspect the taper on the end of the crank, and inside the rotor hub. If it looks scored, you may be able to lap the fit with valve lapping compound. You might also be able to fix it by simply tightening the rotor bolt more, with an air impact wrench, or using a thin coating of blue lock-tite on the taper. If the starter gear is worn enough to slip, the wear should be visible, or at least measurable.

Terry in Australia · « **Reply #8 on:** January 20, 2012, 09:13:52 PM »

I think starter motors failing on F2/3's must be fairly common, the one on mine drove me mad, I replaced the starter clutch with a new one, replaced the 3 countersunk screws with new heavy duty items, and it still made horrible graunching noises and I had this "tick tick tick" noise while riding that I couldn't explain, plus the starter motor seemed to be running slow, particularly when hot.

I swapped the carbs out for a set of reconditioned ones, and while I was at it I replaced the starter motor with a known good one from a K2, and it was a revelation! The bike started quicker, stopped making "graunching" noises, stopped going "tick tick tick", it was a pleasure to ride again! Cheers, Terry.

brandEn · « **Reply #9 on:** January 20, 2012, 09:16:48 PM »

interesting. Maybe I should throw a starter and starter gear at it and see what happens. Sucks I just had my carbs off and reinstalled them last week.

tweakin · « **Reply #10 on:** January 21, 2012, 06:33:28 AM »

I put a new starter in my 915 build since my F2 starter had the same symptoms.

http://nationsautoelectric.com/Honda.html

I also tried all the fixes with nothing working before the new starter.

andy750 · « **Reply #11 on:** January 21, 2012, 08:18:28 AM »

Quote from: tweakin on January 21, 2012, 06:33:28 AM

I put a new starter in my 915 build since my F2 starter had the same symptoms.

http://nationsautoelectric.com/Honda.html

I also tried all the fixes with nothing working before the new starter.

How easy was it to install the starter? You need to take off the alternator cover right? Anything else need replacing while doing this apart from alt. gasket if it needs to come off. Thats a good price!

Thanks
Andy

tweakin · « **Reply #12 on:** January 21, 2012, 03:52:42 PM »

andy- I think replacing the starter is pretty easy and straight forward. Just a new alt gasket, remove the cam chain adjuster for access. The hardest part for me is wiggling out the old starter and sliding in the new starter, because of the tight fitment.

Quote from: andy750 on January 21, 2012, 08:18:28 AM

Quote from: tweakin on January 21, 2012, 06:33:28 AM
I put a new starter in my 915 build since my F2 starter had the same symptoms.

http://nationsautoelectric.com/Honda.html

I also tried all the fixes with nothing working before the new starter.

How easy was it to install the starter? You need to take off the alternator cover right? Anything else need replacing while doing this apart from alt. gasket if it needs to come off. Thats a good price!

Thanks
Andy

MRieck · « **Reply #13 on:** January 21, 2012, 04:13:24 PM »

I have had this problem (the starter "kicking out"). I replaced the starter, rotor, starter gear, Sprag clutch pieces with low mileage, late model parts and have had no problems since. Ever.Make sure that rotor bolt is tight!! I also replace the battery to solenoid cable wit one from an FJ1200

brandEn · « **Reply #14 on:** January 21, 2012, 04:29:11 PM »

New starter on order. I am confident the rotor bolt is tight I made sure of that the first time around troubleshooting this problem. I will try the starter and see how that goes. Mike whats the point of a FJ1200 solenoid cable?

brandEn · « **Reply #15 on:** January 21, 2012, 05:48:21 PM »

Quote from: andy750 on January 21, 2012, 08:18:28 AM

Quote from: tweakin on January 21, 2012, 06:33:28 AM
I put a new starter in my 915 build since my F2 starter had the same symptoms.

http://nationsautoelectric.com/Honda.html

I also tried all the fixes with nothing working before the new starter.

How easy was it to install the starter? You need to take off the alternator cover right? Anything else need replacing while doing this apart from alt. gasket if it needs to come off. Thats a good price!

Thanks
Andy

I just removed my starter. I had to remove the cam chain tensioner and the shifter cover only. Use the 2 10mm bolts that hold it in place and screw them into the empty holes for the cover and it lifted right out. Just had to use a mallet to tap the starter out of its home. Be prepared for oil to drain from the shifter cover.

MRieck · « **Reply #16 on:** January 21, 2012, 06:31:20 PM »

Quote from: brandEn on January 21, 2012, 04:29:11 PM

New starter on order. I am confident the rotor bolt is tight I made sure of that the first time around troubleshooting this problem. I will try the starter and see how that goes. Mike whats the point of a FJ1200 solenoid cable?

It is a heavier cable and fits well. I tried it because I had an extra one hanging around. Here is another big point......what ignition are you using? I have found with high compression engines you need a Dyna 2000 just to retard the ignition enough (20 degrees) when starting. That is a big difference.

brandEn · « **Reply #17 on:** January 21, 2012, 06:51:12 PM »

Using a Dyna 2000.

brandEn · « **Reply #18 on:** January 21, 2012, 07:15:35 PM »

I took my starter apart to see whats going on. Its pretty dirty and the brushes are pretty worn. Other than that no other visible damage.

Danno · « **Reply #19 on:** January 21, 2012, 09:53:23 PM »

try taking a knife blade along the coms (slots on the side of the rotor) to clean the carbon out of them and check the bushings to make sure it is not hitting the magnets

MRieck · « **Reply #20 on:** January 22, 2012, 05:40:04 AM »

Quote from: brandEn on January 21, 2012, 06:51:12 PM

Using a Dyna 2000.

good

Jerry Rxman Griffin aka MuthaF'er · « **Reply #21 on:** January 22, 2012, 09:48:24 AM »

One thing I noticed as I was checking parts from different engines was uneven wear on the "bushing" on the starter clutch gear that the clutch rollers engage to. Does this description make sense? If you have that "issue" all you have to do to see this is to run your fingers around the "bushing" and you will feel the irregularities. ie no longer perfectly round, kinda like indentions. Can't say this may be part of a problem though. I do intend on mixing and matching with the better parts when the time comes.

andy750 · « **Reply #22 on:** January 22, 2012, 11:57:57 AM »

Thanks guys for the feedback on replacing the starter. Give us an update when you run with the new starter to see if it was in fact the issue.

good luck
Andy

Danno · « **Reply #23 on:** January 28, 2012, 05:30:52 PM »

jerry is right like I said check the bushings

brandEn · « **Reply #24 on:** February 03, 2012, 08:08:20 AM »

I got my rebuilt starter installed yesterday and I haven't had a failure yet. So far its started strong everytime including two cold starts

. So I will consider the starter the fix for my issue. "If" I have any more failures I will be sure to update this thread for any future forum searchers.... Thanks to all that helped.

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Author Topic: CB750 starter motor failing -- now w/pics (Read 15342 times)