GT550 Borg Warner starter clutch

Post your Kettle problems here and cures
User avatar
yeadon_m
Posts: 7401
Joined: Sat Jan 02, 2010 7:10 am
Location: Canterbury Kent

Re: GT550 Borg Warner starter clutch

Post by yeadon_m »

Cheers chaps, all looks worth an explore on my 550B, given my hybrid motor seems to have given up self-harming itself!
I was noodling to what extent a weak starter motor might contribute to an apparent weakness in the starter clutch one way system. My experience is usually that when I hit the button, the engine rotates once or twice but, if it doesn’t start, it then seems to kick the starter system off and I have to wait a couple of seconds until I hear a light clunk as everything comes to rest before I can have another press of the button.

Confusingly, the engine will often fire up first kick if I just treat it like a GT380!

It’s as if, when the motor fires on the starter button, it correctly overruns the one way gear, so disengaging said one way gear.
To test this idea, I reasoned that if I pulled the plug caps off so that it couldn’t fire, I’d get a proper test of the one way starter system. Lo & behold, when I did that, it cranks continuously if much more slowly than did Barry’s customer 550 that he was working on.

I’m a bit more optimistic that much of my starter difficulties are down to a weak starter motor. If the starter motor would spin the engine briskly, I think the one way system would do its job until the engine fires properly. I’ll also take care to thoroughly wash out all the starter clutch components, especially the dratted one way bearing.

Odd to think in all these years, I’ve never tried the starter button on the fully built up bike without the plug caps on. I do recall spinning the motor extensively after pulling the cylinders down so I could visually test the oil pump system. Under those lighter loads (no compression), it would spin on the starter for as long as I kept the button pressed!

Cheers,
Mike
User avatar
Alan H
Posts: 12104
Joined: Fri Aug 05, 2011 6:38 am
Location: Wombwell, Republic of South Yorkshire

Re: GT550 Borg Warner starter clutch

Post by Alan H »

Mike, if he motor fires at all, then it kicks the starter clutch out immediately, so if your motor starts really easy on kick, that may be why it does what it does on electric. Maybe the firing of the first pot over TDC isn't 'quite' enough to start the engine, but enough to kick out the starter. It might be an idea to check the voltage at the coils to see if you have a weak spark when you use the starter. Those multiplugs near the coils can have tarnished contacts after 40 odd years......
Remember that power to the coils goes from the battery +, through the fuse holder, several connectors to the ignition switch, kill switch then back to the coil multiplugs and then even more bullets to the points. It doesn't take much resistance to make the battery voltage drop to less than optimal when it gets to where it's needed.

Baz can get starter motors reconditioned, but before you do, check all connections from battery to starter motor - especially the earth to the cases - and the solenoid. A new solenoid is less than a tenner, and in fact any car solenoid should do the trick. Plenty on ebay anyway.
Proof that four strokes are over complicated
User avatar
PaulD738
Posts: 3962
Joined: Thu Sep 25, 2014 6:57 pm
Location: Warrington Cheshire

Re: GT550 Borg Warner starter clutch

Post by PaulD738 »

I’m not sure what the starter clutch looks like on the 550 but I assume it’s a sprag type. I’ve just finished rebuilding a Honda 350K4 motor which also had starter problems. On the Honda it has big rollers which bite on the crankshaft and small hollow rollers with springs inside to push the big rollers on to the crankshaft. On first inspection I couldn’t see anything amiss, the big rollers where perfect as was the crankshaft bearing surface. Looking closer the small rollers where ridged where they slide in & out of the clutch body so they didn’t fully extend or retract. There is a repair kit to replace both sets of rollers & springs which cured the problem completely.
They're rubbish them Jap bikes lad they won't last five minutes! you want to get yourself a nice Royal Enfield!
A quote from my old dad 8-)

I started out with nothing and I’ve got most of it left!
User avatar
Alan H
Posts: 12104
Joined: Fri Aug 05, 2011 6:38 am
Location: Wombwell, Republic of South Yorkshire

Re: GT550 Borg Warner starter clutch

Post by Alan H »

Similar idea to the Suzukis Paul, but different problem although it might be caused by a similar thing. lack of oil changes and possible loose parts.
Favourite cause (according to Eddie Crooks and Frank Whiteway back in 1972 was the 3 countersunk studs holding the vaguely triangular plate on at the back of the clutch. When this came loose, it allowed the rollers to misalign and 'chatter' on the centre and snag it eventually causing it to shatter.
If the studs were loctited (and they also said to gently tap the threads to flatten them in one place), the studs wouldn't become loose and there wouldn't be a problem. I followed the advice and ran my original 550J for about 4 years without issue - and the 550K I did a few years back similarly - that ran 3 years ok until sold on.
That being said, I do think that the Borg warner starters are better and have them on my A and J bikes - mainly so that I can standardise and only need one set of spares.
Comparisons below, click the pic for larger view!! :shock:
Starter clutch comparisons.jpg
Proof that four strokes are over complicated
Post Reply