750 turbo Starter clutch slipping

Wed Jul 11, 2012 7:47 pm

Gents, its been some time and I am on the bludge.
The Turbo I started around 12 months ago has been fully rebuilt and does not look too bad.
I am usually on the turo.com forum but have a problem that some of you may be able to help with.
During the rebuild I replaced the starter clutch with a new kit as the clutch had been slipping intermittently when she was on the road some 16 years ago.
Now with the rebuild complete the clutch was still slipping more often than before. I put that down to better compression.
I decided to pull the sump etc off again and get to the bottom of the problem so after inspecting the components of the clutch and secondary shaft (bearings etc) and finding nothing obviously wrong, I bought a new starter sprocket and reassembled the whole thing. First try at starting and the bastard slips at least as bad as before. Strip the thing down again and washed all parts and reassembled dry. (I was clutching at straws and thought maybe oil type was the problem) Reassembled once more and had no slipping problems at all.........until I refilled with a standard mineral based oil and now the clutch is slipping most of the time.
I am hoping some of you guys will have heard of the problem and am open to any suggestions.
Photo of (almost) completed rebuild below

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Wed Jul 11, 2012 7:57 pm

what oil did you change to, before you re-filled with mineral oil ? Why did you change to mineral oil if the starter clutch wasn't slipping with that other oil?

I have done a few starter clutches in 650/750's over the years, generally it is dirty oil that starts the problems with the rollers getting caught on tiny pieces of crap in the oil and not throwing out correctly, leading to the starter motor not working properly. Changing the oil can often sort the problem for a while, but eventually the problem returns.

The design of the starter clutch in these motors is a well-known achilles heel and there is almost nothing that can be done to fix the problem so it never comes back. Even with fully re-built clutches and all new parts - give these motors a few years and the problem will return at some point.

Thu Jul 12, 2012 6:23 am

G'day Gos.
The clutch has slipped slightly with the original oil and worse after the rebuild with semi-syn oil. In other words it has always slipped but is now real bad.
After I rebuilt the engine I filled with Penrite 15W50 Semi syn. Originally I used to run Penzoil 50. The clutch did slip occasionally with the Penzoil many years ago so during the rebuild I thought it wise to replace the clutch kit (rollers, springs and pushrods). When it was time to fire up the slipping problem was worse and with little else to go on I thought maybe the oil was a contributor. I removed the secondary shaft and clutch but could see no problems. Even did a static test in the vice but could not get the thing to slip on the bench. Seeing as there are only the two parts in contact with each other, rollers and starter sprocket, I decided to replace the sprocket. Reassembled everything and refilled with Shell Helix H3 20W50. The problem is now so bad that I have not even been able to get the clutch to "engage" long enough to start the bike.
It looks like I will be pulling it down again this weekend and checking every thing again. There must be something different between this bike and one that starts OK Gos, maybe the oil is too clean :lol:

More than likely I will find something that I have done wrong and end up looking like a drip.
Any ideas much appreciated,
Cheers, JR

Thu Jul 12, 2012 7:31 pm

Been chatting on the turbo forum and Tack has suggested that there may be some imperfection in the slots of the starter clutch housing that holds the rollers, so will be stripping the clutch out again this weekend and checking that. Hopefully we will have some success as the thing will hardly engage at all now.
I will post results as soon as available and hopefully they will be positive and help members avoid the probs I have had.

Thu Jul 12, 2012 8:16 pm

good luck with it mate, one of the most recent starter-clutch jobs I helped with was ProblemChilds 750 - Eddie Jnr. Replaced all the bits - starter clutch worked 100% from the word go. But is has already slipped a couple of times since that rebuild.......

I have to do another one soon as well :lol:

on the starter clutch on my z750 dirtbike. It slipped like a bitch to the point that I just took the starter motor off, bunged a welch-plug into the hole, and fitted up a kick-starter from a z650 ! :kuda:

when you have the bits apart again, just make sure all the springs are seated correctly and that the rollers can move without any binding. This is the best you can do until the ultimate test - pushing that button !

Sat Jul 14, 2012 7:09 am

Thanks Gos. I stripper her down again last night and had a good look at the clutch hub and it may be that it is the problem so to eliminate that I have ordered a new one, $170, but better than having to strip again, hopefully.
That will be all components that contact each other will have been replaced and if that does not work, well.........
Clutch hub and sprocket pics below.
Will let you know how it goes,
Cheers.

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