Topic: bike wont start on button help needed

[CB750F2]

First I would just tighten up the units, change the plugs and try again. The ignition units may still be OK. Pat

[CB750F2]

I have searched the web but have not been able to find a diagram of the internals of the mps-200 units but I did find that it is common for them to overheat and ooze out the black sealant without actually failing. You said that you noticed the overheating when working on your bike. Leaving the ignition turned on with the bike stationary and not running may contribute to this. I would give it a go with a set of normal plugs fitted and a fully charged battery. If you still have problems measure the voltage at the battery, the coils and at black/white wire going to the mps-200 units. Take these measurements while cranking the motor. Does the 650 have a kick start? If so does it start using the kick start? Pat

[Hush]

CB650Z Don't have a kicker mores the pity.
I was jump starting my bike from a car battery before I got a decent bike battery for it and if I did not remove the cables from the car battery then those units under the seat heated up really well.
Guess something to do with the charging circuit, anyhow with new battery fitted no more heat.

Since your bike fires up quick from a bum start then maybe the starter is taking too much power and not leaving enough for the plugs to get a decent spark?

[CB750F2]

Hush, yes I believe that the voltage to the spark units is dropping too low for them to fire when the starter motor is being used - starter may be drawing more current than it should or the battery has seen better days or there is too much voltage drop in the wiring harness. Dids said that the battery volts dropped to 8v when operating the starter so on the black/white wire to the spark units there is probably 7v which may be too low for them to fire. It will be interesting to hear what Dids has to say tomorrow. Pat

[Hush]

Yeah Pat lets hope he has some joy, will be an interesting watch as I have exactly same bike and always on the lookout for possible up coming problems........Hush.

[speedy gonzalais]

Ok i seem to have found the problem or problems the spark units where f***ed beyond repair the regulator was also not working right the starter was stiff havnt stripped it yet but i belive i know what caused all this, i unwraped the harness well part of it theres 3 yellow wires running from the altenator to the regulator 2 of them had been replaced with .75mm wire im sure it should be 4-5mm and the red/white wire running from the regulator to starter relay was the same, Im just gonna use the harness off the other bike as it all looks original and i might take the altenator from the other engine as well as im sure thats prob been damaged

il let u know how it goes cheers

[speedy gonzalais]

Update: The other spark units gave up it was starting on the button but when i went for a ride it was like the timing was out it was missing and back firing but running fine on idle and would rev up in nutural no probs? My god what is going on with this machine ive even swapped the advance and retard unit, Im so close to stickin the bike in a garage and under a sheet where i cant see it!

[Hush]

Don't give up bro, when it all comes together its all gonna be worth it.
You do seem to have had a greater share of troubles than most on here.
I think sometimes it would be a lot easier if we all lived a lot closer and could assist physically rather than just on this forum.
Swapping the loom should have cured your problem, rethink your path, sounds definately like a coil problem, "revs fine at idle but when pressure applied bike missfires"!

[CB750F2]

Dids, I am not sure where you are at or what you have done. from your last post I take it that the original spark units were faulty and after you replaced the spark units and repaired the wiring loom the bike now starts with the starter motor - is this correct? So,now the bike starts OK but misses and carrys on when riding? Was the missing happening when you had the other spark units and were push starting the bike? Are the replacement spark units new and the same brand and model? Pat

[speedy gonzalais]

the bike was running fine before, she would rev up to 9000 easily when riding but now im lucky to get her upto 4500rpm when riding, she revs upto 9000 from idle in nutural but not on the road, the spark units are off the spares bike another 650z she starts on the button now, ive changed the regulator spark units wiring harness and spark plugs back to the old dr8es, recharged the battery, like i mentioned earlier there was a couple of important wires that had been replaced with the wrong size wire it was more like speaker wire. Ive found a shop thats actualy got some original spark units in old stock new ones so il be down there tomorow, also the altenator is coming off im changing it for the other one ive tested this one and im not sure if it working right at one point my multi meter was reading 135v.

[CB750F2]

Ok seems you have fixed the starting problem so you are progressing - you beauty! So the only thing that you have done that may be causing the current problem is that the spark units have been changed. As long as you haven't disturbed the pulse generators then your timing should not have changed but I would check it just the same. To do this I think thay you will need a timing light. Check it at idle and at 3500 rpm. Are you sure that your original spark units are faulty? Just because they have been getting hot doesn't neceassarily mean that they are faulty. If you are unsure try swapping one at a time - you have nothing to loose. Pat

[speedy gonzalais]

ok is it normal for the altenator to kick out 135v?

[CB750F2]

Normally no. However, if you ran the motor with the red/white wire disconnected at the starter solenoid there will be no feedback voltage to the regulator so the voltage regulator will not regulate and the voltage from the alternator will rise as the revs increase. I hope that you haven't damaged your rectifier which in your bike is part of the regulator. In the 750 the regulator and rectifier are separate. Pat

[speedy gonzalais]

na i was testing the voltage strait from the altenator before the regulator any way its all done now got brand new spark units bike starts fine i get 13v on the battery at idle and 14v at 2500rpm

thanks for the help every one