TOPIC:

Did you also replace the gear? The surface that the rollers grab can wear and cause slippage (see image below). Ed

No,I didn’t replace that,guess I’d better strip the s clutch out again!!

So I’ve replaced the starter gear,as you said it was shiny and worn. It’s back together and I’m still having problems. I hit the starter button and it’ll turn over but then stops but I can hear the starter spinning up,I un press the starter button and when the s motor slows down it engages again and stops with a small thud.
I suppose I’ve buggered the s clutch again coz I didn’t replace the s gear.
I reset the valve clearances,they were all over the place.
I also replaced the coils as I didn’t think the spark was very big and blue. I have already done the 2 relay mod. I still havnt got a big blue spark though.

Well that sucks lotta work ...... hate to give advice like this for the fear of not being correct on the solution but maybe new rollers again (not the whole unit) to go with the new gear?? and when mine went out it started in the spring when it was in the 50s and 60s and I was using 20/50 Mobil one...... had read that a few people were using synthetic oil and blamed that on their st clutch problem so I switched to 10/40 Valvoline (not saying syn oil was the problem Ed and many others have used it for years) just saying the slightly slippery oil and thicker oil when cold "might" have been a factor

. As soon as I did the problem went away and it was fine till fall when the first 60 degree day hit then it slipped again. What I think was happening with mine was it right on the edge of going bad and the extra drag for the 20/50 in cold temps was enough to get it to slip??? Just something to think about and somewhere around here there's a thread on using a newer model 750 starter clutch with a improved design ...... I wish I would have seen this before but would be a lot of extra cost and trouble.

I replaced the whole unit, roller, springs and gear around 5 years ago and its still going strong but threads like this worry's me.

I agree,I think the oil is a factor. I swapped to 20/50 because I couldn’t get 10/40 in mineral,it was only available in semi (I know it’s mineral) and I found that semi was pissing out the valve co er and base gasket whereas mineral didn’t.
Perhaps I’d be better off using 10/40 semi,what do you use?

I switched to 10/40 Valvoline bike oil but it might have just been a band aid and might not be the solution...... search "starter gear solution-zr7s part" for the thread on the improved set up.

I did search the other day when it was first mentioned,but I thought it looks exactly the same parts. I also had a look on eboy,there was only 550 ones on the Uk site,they look th3 same too.

The only 10/40 mineral I can find is used in quad bikes,I might give it a go.

I’m using Yamalube 10/40 mineral.

Example:
www.motorspeed.no/yamaha/ymd65031-00/yamalube-m-4-10w40

Well,the good news is changing the oil to Motul atv/utv 10w/40 mineral oil has worked wonders for the starter clutch issue. I’m not getting any slippage,so far I hasten to add!.
The reason I chose the above oil is it’s proper mineral oil,opie oils,the co that sold it assured me it’s fine if that’s what I wanted to use but couldn’t understand why I wouldn’t use a semi. He obviously doesn’t own a z air cooled!
And the oil was inexpensive,I’m losing oil past the gearchange seal and constantly topping up, I am experimenting with a possible fix on that........

I’m not happy with the choke situation though,I want to be able to pull the choke full on and press the starter and have it fire right up but the choke doesn’t seem to do a lot. I know the carbs are clean,I’ve had them apart so many times. I’m wondering if altering the pilot air screws from 2 to 2.5 or 3 turns out might help?
Edit: I’ve just tried going from 2 to 3 turns-no difference,so I went to 4-no difference,then I went back to 1.5 turns out and it wouldn’t start on full choke. Once started it will tick over best on half choke,at 1.5 turns out it cuts out if I pull out to full from half.

Always a really good feelig when things turn out

Sure is fella, amazing really.
Now the choke:(

Pipes66 wrote: Sure is fella, amazing really.
Now the choke:(

I have purchase Gunson colortune on Ebay, have not been able to test it yet.

But if you think the mix screw need to be tunned, it can maybe a option for you to?