TOPIC:

In my delightful first ride of the season yesterday i had not a single problem, everything was great, aside from a few little rattles, but I think I might have a problem with my starter clutch.
This morning i got out and started my bike, and after then engine started running for about a second it made sort of a grinding noise, sort of like a car when you try to start it running. I have started it a few times since without the noise, but i fear it is doing permanent damage.
As many of you know, I am not a mechanical whiz, and I wondering what you think I should be doing to fix this problem.

Some other factors that may come into play here are the temperature, which was around 33 degrees, and my starter button replacement job last fall just before putting it away. my starter button fell out broken and I had to sort of glue it back in, could this be it?
Thanks Guys,
Mike

Could be several things; from having the starter engaged while the engine is running, or some screws on the backside of the starter clutch backing out rubbing on the engine cases.

The first could be repaired by replacing the start switch or the entire right pod on the handlebar. The second by removing the left side engine case,pulling the stator magnet and inspecting the starter clutch.

What's your model and year of your bike?

Thanks for the advice, I might check into it. Doesn't seem to happen (yet) when warm, or when i start it in neutral, any ideas why this might happen?
It's a 1981 KZ750 LTD.

Hi Mike,

My 750 does the same thing. When it's cold out, she squalls like a howling cat before she starts, when she's warm or it's warmer out....nada. Had the same thing happen with my KZ400. I haven't had it get any worse over the last year so I'm going to just be gentle with in in the mornings and hope I can get a couple of more years out of it before I have to dig into the engine. Starter clutch repair is harder on the 650/750's than on the older 900's just 'cause where it's located

From what you are saying sounds like the button was held too long. When clutch starter does not grab, is usually when you first push the button, and engine does not turn. Just the screeching sound.

Once the engine fires, if starter clutch is kept engaged, it simply freewheels.

Hi Hugo,

You said: "Once the engine fires, if starter clutch is kept engaged, it simply freewheels."

I wish it was that simple. A month ago the starter clutch on my 750 Twin started groaning right after start up, only when it was cold. I traced it to some relatively minor wear marks of the starter clutch sprocket and the engagement rollers. Apparently at low engine speeds the centripetal acceleration is not enough to over come the springs that push the rollers against the sprocket. The wear marks on the sprocket and the rollers make a bunch of noise when they are forced against each other by the springs.



Once the engine quits fumbling around and spins up the centripetal acceleration forces the rollers away from the sprocket and things quiet down.

Bill R

The starter clutch is a one-way clutch. Only grabs in one direction. In the other direction it free-wheels. This is a true statement and a fact. It you take the starter motor out and push the middle gear with finger, it only moves in one direction.

When the starter motor rotates the starter clutch, it grabs against an engine that IS NOT TURNING. As soon as the engine catches, turning on its own power, it spins faster than starter clutch, so there is nothing to grab. It is not centrifugal forces that disengage, is relative speed. At this point, if the starting motor is kept engaged, it will keep turning the starter clutch, but secondary shaft(750-Four)is moving faster, so rollers don't catch. Same if you were pedaling a bicycle that is moving downhill faster than you can pedal.

If there is noise, like a bad bearing when attempting to start the bike, then rollers, springs, and/or hub are going bad in the starter clutch and should be replaced.

My starting clutch was screeching sometimes on pressing the button. Engine would not turn. After a year I got fed up, replaced the whole clutch and all noises and slipping went away for good.

MikePotter86 wrote:

Some other factors that may come into play here are the temperature, which was around 33 degrees, and my starter button replacement job last fall just before putting it away. my starter button fell out broken and I had to sort of glue it back in, could this be it?
Thanks Guys,
Mike

If there is greater resistance to the starter turning, the starter clutch is the part that takes the strain. Therefore, ALWAYS start the bike in neutral, since holding in the clutch does not entirely disengage it, especially if your oil is cold and sticky. Also, make sure your clutch adjustment on the cover is set right. If it is set to allow the clutch to remain too tight (engaged), you will have more starting resistance, and thus more strain on the starter clutch.

Your starter button has no impact on this.

I would wait for warmer weather, and see if your problem remains. If not, live with it until the starter clutch definately needs replacement. It is a pain to replace, but I have done it with the engine in the frame.

hugo wrote:

When the starter motor rotates the starter clutch, it grabs against an engine that IS NOT TURNING. As soon as the engine catches, turning on its own power, it spins faster than starter clutch, so there is nothing to grab. It is not centrifugal forces that disengage, is relative speed. At this point, if the starting motor is kept engaged, it will keep turning the starter clutch, but secondary shaft(750-Four)is moving faster, so rollers don't catch.

I'm sorry, but that is not correct. When you push the start button, the starter motor spins and drives an idler gear sitting in the top of the crankcase, the idler gear then drives the starter clutch gear sitting on a needle roller bearing on the secondary shaft.

The rollers in the starter clutch housing grabs on to the starter clutch gear and the housing rotates with the gear - this will make the crank turn as it is tied to the starter clutch housing through the primary chain.

Once the engine starts, the process is reversed. The pistons drive the crank, the crank drives the starter clutch housing through the primary chain and the starter clutch housing drives the secondary shaft - the starter clutch housing is sitting on splines on the secondary shaft and will rotate at excactly the same speed as the secondary shaft, this is what cause the rollers to be forced back, they do indeed release by centrifugal force - motion is then transferred through the secondary shaft gear to the clutch basket, transmission and so on.

However, once you release the start button, the starter, idler gear and starter clutch gear stop spinning, when the engine is running they are standing still - the purpose of the oneway is partly to prevent spinning the gears and starter motor as the rollers re-engage the starter clutch gear when you shut the engine down, partly to allow you to use the kickstart (if so equipped).

The grinding sound you hear once in a while is the rollers failing to grab on to and slipping on the starter clutch gear.

Mike - I'm having the same problem. Were you able to fix it?
I've had the starter clutch out twice. Fixed it the first time
but this time I'm stumped
Dave

I noticed the same issue is occurring with my KZ400B. Is there a fix besides replacing the starter clutch? as well is the cause a lack of lubrication (i.e. neglected oil changes)?

Hey, I am sorry but I honestly can't remember how I resolved this. It was over 7 years ago. I honestly think it just happened one or two more times in colder weather and then stopped. I inherited an older airhead the year after and sold my KZ. Still regret it. But at least it went to an eager young rider!

Good luck,
Mike