Starter Clutch Replaced 5k miles ago - slipping

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Starter Clutch Replaced 5k miles ago - slipping

Postby ZZ1ZR » 10 Dec 2018, 22:55

I have a 1991 750 C1. Rebuilt the engine in 2011, fitted original starter clutch as couldn't find anything wrong with it. Engine wouldn't turn over properly. Fitted repair kit, same result. Fitted new starter clutch, problem went away. Now, 5k miles later, the starter motor just spins over, won't turn the engine. I assumed it was something to do with the idler gear. No its the starter clutch. By hand it feels fine but you can see that the starter clutch springs are severely weakened.

I am thinking about a new set of springs but after the first experience I'm not so sure. Anyone with experience?

Cheers

Lindsay
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Re: Starter Clutch Replaced 5k miles ago - slipping

Postby hugojose » 11 Dec 2018, 11:22

I changed starter clutch several years ago, but thus far, it has never failed. Yes, I agree that changing just springs and rollers is too often not enough, however the fact you are having troubles again after a new starting clutch is puzzling, assuming everything was put together the proper way. Also when my starter clutch was bad, it would only fail occasionally , not always.

In the old KZrider forum, dealing with even older Kawasaki fours, there is talk about switching to the starter clutch from the ZR-7, which was the latest KZ750-4 in North America. From what I understand it has changes making more reliable and it should fit on the Zeph 750, however, don't remember if they mentioned the secondary shaft also has to be changed.

Later on I may go back see if I can add some more.
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Re: Starter Clutch Replaced 5k miles ago - slipping

Postby Freddy » 11 Dec 2018, 12:49

ZZ1ZR wrote:I have a 1991 750 C1. Rebuilt the engine in 2011, fitted original starter clutch as couldn't find anything wrong with it. Engine wouldn't turn over properly. Fitted repair kit, same result. Fitted new starter clutch, problem went away. Now, 5k miles later, the starter motor just spins over, won't turn the engine. I assumed it was something to do with the idler gear. No its the starter clutch. By hand it feels fine but you can see that the starter clutch springs are severely weakened.

I am thinking about a new set of springs but after the first experience I'm not so sure. Anyone with experience?

Cheers

Lindsay


If your using a semi or full synthetic engine oil, dump it out and use a 100% mineral motorcycle oil and see what happens.
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Re: Starter Clutch Replaced 5k miles ago - slipping

Postby DaftRusty » 11 Dec 2018, 20:04

I have done the zr-7 sprag clutch swap and I highly recommend that if you have to dig into your motor to fix the old clutch then you should do the swap as well. I found the used zr-7 parts cheaper than I could buy the rebuild kit and new starter sprocket for. You can use your current secondary shaft and all you need is the sprag clutch itself and the zr-7 specific washer/spacer in order to make it work. I could go into much greater detail, but this post on kzrider pretty much lays it all out.
https://kzrider.com/forum/2-engine/6076 ... art#790865

Hope this helps.
1991 zr550
Factory Pro stage 1 jet kit
zx550 pistons and cams
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Re: Starter Clutch Replaced 5k miles ago - slipping

Postby Freddy » 12 Dec 2018, 06:48

DaftRusty wrote:I have done the zr-7 sprag clutch swap and I highly recommend that if you have to dig into your motor to fix the old clutch then you should do the swap as well. I found the used zr-7 parts cheaper than I could buy the rebuild kit and new starter sprocket for. You can use your current secondary shaft and all you need is the sprag clutch itself and the zr-7 specific washer/spacer in order to make it work. I could go into much greater detail, but this post on kzrider pretty much lays it all out.
https://kzrider.com/forum/2-engine/6076 ... art#790865

Hope this helps.


Note what the first post in the KZrider forum thread says about synthetic oil. Mine was working perfectly at 100,000 kilometers ..... and immediately started to give trouble as soon as I switched to fully synthetic oil. So did the drive clutch.

Running semi-synthetic oil with all new OEM parts (complete clutch assembly and gear/hub) I've had no trouble whatsoever in the 65,000 kilometers since the job was done.

While I have no factual basis, I believe it was the introduction of synthetic oils into the market in late 1990's that necessitated Kawasaki redesigning both the drive and starter clutches. The D1 Zephyr has the same drive clutch as a ZR7. But it still needs heavier aftermarket clutch springs not to slip with semi synthetic oil when pressed hard. So does the ZR7.
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Re: Starter Clutch Replaced 5k miles ago - slipping

Postby DaftRusty » 12 Dec 2018, 15:21

Freddy wrote:Note what the first post in the KZrider forum thread says about synthetic oil. Mine was working perfectly at 100,000 kilometers ..... and immediately started to give trouble as soon as I switched to fully synthetic oil. So did the drive clutch.

Running semi-synthetic oil with all new OEM parts (complete clutch assembly and gear/hub) I've had no trouble whatsoever in the 65,000 kilometers since the job was done.

While I have no factual basis, I believe it was the introduction of synthetic oils into the market in late 1990's that necessitated Kawasaki redesigning both the drive and starter clutches. The D1 Zephyr has the same drive clutch as a ZR7. But it still needs heavier aftermarket clutch springs not to slip with semi synthetic oil when pressed hard. So does the ZR7.



The original poster of this thread never mentioned or admitted to using synthetic, so that is why I did not mention it. I am aware of the issues with running synthetic or any oils with anti-friction modifiers in a wet clutch engine that was not designed for synthetic use, so that is why I do not. I will not mention what I use for fear of being dragged into the dreaded oil debate.
The original poster does mention they suspected the idler gear but dismissed it. Problem is that the contact surface of the idler gear may "look good", but in fact may be worn and have chatter marks to the point the roller clutch cannot lock onto it properly and no matter how many times someone replaces the rollers and springs, the clutch will never operate properly for any length of time.
My idler gear also showed wear and I then found it was no longer available from Kawasaki at any price, so that is what led me to investigate using the zr-7 starter clutch. Just a new zr-7 idler gear is $82+shipping, so I bought a used zr-7 starter clutch assembly for a fraction of the price.
So I am just offering up empirical evidence that swapping over to a superior version of a starter clutch is cheap, easy and entirely worth the effort as it will permanently fix the issue.
Attachments
StarterClutchGearComparision.jpg
Comparison of good vs bad
1991 zr550
Factory Pro stage 1 jet kit
zx550 pistons and cams
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Re: Starter Clutch Replaced 5k miles ago - slipping

Postby Freddy » 12 Dec 2018, 23:43

DaftRusty wrote:The original poster of this thread never mentioned or admitted to using synthetic, so that is why I did not mention it.


Sure about that .......'cut and paste' from the very first post in the thread

The Zephyr, ZR7 bikes took the kz650/z650 engine & transmission and slowly improved it over 2 decades.
One z650 weak point is the starter clutch. People change rollers, springs, but it appears that the most common issue are several things.

1. Low cranking battery
2. Synthetic oil or oil additives
3. Weak springs
4. DENTS IN THE ROLLER RAMPS


Using synthetic oil and starter clutch problems in older bikes is a well documented problem e.g. http://forums.sohc4.net/index.php?topic=130534.0

There can be no cheaper/simpler possible fix to a problematic starter clutch in an engine designed prior to lower friction synthetic oils coming onto the market than reverting back to full mineral oil and see what happens. Over the years I've made this same suggestion to a number of owners of various make/model bikes, and every time it has fixed the problem.

I'm not disputing the ZR7 may be a superior clutch design. But as the original Zephyr design worked flawlessly in my bike for 100,000 kilometers till I stuck in synthetic, and the replacement has now got 65,000 kilometers on it running semi-synthetic oil, my point is the original design can't be all that bad if more traditional oils are utilised.

P.S. And the reason I replaced the starter clutch at 100,000 kilometers instead of simply stop using full synthetic oil and see how much longer it would work without a problem on more traditional oils was because I didn't recognize immediately the connection between the change in oil type and starter clutch problem. That realization occurred after I'd already replaced the clutch.

As the OP has fitted a brand new complete clutch assembly and hub only 5000 milers ago (if I have it correct) there has to be a reason why this proven design is not working.
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Re: Starter Clutch Replaced 5k miles ago - slipping

Postby DaftRusty » 13 Dec 2018, 00:38

ZZ1ZR wrote:I have a 1991 750 C1. Rebuilt the engine in 2011, fitted original starter clutch as couldn't find anything wrong with it. Engine wouldn't turn over properly. Fitted repair kit, same result. Fitted new starter clutch, problem went away. Now, 5k miles later, the starter motor just spins over, won't turn the engine. I assumed it was something to do with the idler gear. No its the starter clutch. By hand it feels fine but you can see that the starter clutch springs are severely weakened.

I am thinking about a new set of springs but after the first experience I'm not so sure. Anyone with experience?

Cheers

Lindsay



This original post Freddy....this one....posted by ZZ1R asking for help.

Freddy wrote:As the OP has fitted a brand new complete clutch assembly and hub only 5000 milers ago (if I have it correct) there has to be a reason why this proven design is not working.

He only mentions replacing the starter clutch, not the idler gear. I have read dozens and dozens of posts on multiple sites regarding the problem of replacing the springs, rollers or even the clutch itself does not permanently fix the issue unless a brand new idler gear is also installed. And new idler gears are no longer available unless found by chance on an auction site.
1991 zr550
Factory Pro stage 1 jet kit
zx550 pistons and cams
DaftRusty
 
Posts: 24
Joined: 07 Sep 2017, 19:31

Re: Starter Clutch Replaced 5k miles ago - slipping

Postby Freddy » 13 Dec 2018, 02:48

DaftRusty wrote:
ZZ1ZR wrote:He only mentions replacing the starter clutch, not the idler gear. I have read dozens and dozens of posts on multiple sites regarding the problem of replacing the springs, rollers or even the clutch itself does not permanently fix the issue unless a brand new idler gear is also installed. And new idler gears are no longer available unless found by chance on an auction site.


When I did mine at 1000,000 kilometers I fitted a complete new clutch assembly, which I'd bought in advance of stripping the bike down. I didn't have a new idler gear so while the old one was quite heavily 'rutted' back in it went. I ordered a new idler gear, and stuck it in the parts bin. With just the new clutch assembly it worked flawlessly.

It stayed that way for perhaps another 20,000 kilometers till when I was overhauling the gearbox. As you have to remove the secondary shaft to get at the gearbox I took the opportunity to replace the idler gear at that time.

Point being, in my case just the new clutch hub with a heavily used idler gear completely remedied the problem. There was no visible wear of the old rolls in the clutch assembly, and the spring were fine. I doubt the springs actually do much other than cause the rollers to move forward and make contact with the hub. All pressure is due to a 'wedge effect'. So the only place I see that was causing my problem was wear in the grooves of the clutch hub. This I believe reduces the angle of purchase and 'wedge' pressure. So I'm not surprised that repair kits don't work. I think the principal problem is wear in the clutch hub itself. This problem becomes compounded by 'slipperier' synthetic oils. And because 'fully synthetic oil' is such a vague description of what the product actually is i.e. class4, class5, % of ester actually in the blend) results may vary significantly by brand and product.

Regarding the idler gear hub being chopped up a bit (with mine working fine). What is likely to allow the rolls in a new hub to wedge and grip the best. A perfectly smooth polished hub, or a roughened slightly grooved one? It seems to me a slightly chewed up idler gear surface should improve grip by the rollers in a good clutch hub, not make it less.
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Re: Starter Clutch Replaced 5k miles ago - slipping

Postby ZZ1ZR » 14 Dec 2018, 12:16

Some interesting replies guys, thank you. Just to clarify I did not replace the driven gear/hub. I think it must have been unavailable at the time, the hub is rutted. Also I use Mobil 1 semi synthetic which probably hasn’t helped. I think a ZR7 starter clutch sounds like a good idea.
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