83 KZ750E no power, stalls and wont start when hot

Hi guys,
Im in a process of restoring 1983 kz750, which wasnt working when i bought it.
Now its allmost done, engine rebuilt, new valves, valve clearances are correct, new plugs, cables, battery, carbs rebuilt and cleaned,new jets... basically what i saw i got fixed.

One thing that the bike has is the ignition system, which PO probably manufactured by himself.

THE PROBLEM: Bike starts all nice when cold. Once i take it for a spin, it has very low power, pretty hard to overtake anything, and after about 10mins riding it looses power alltogether to complete stop.
After that it wont start at all.

Any ideas?

Thanks in advance

When it stalls out you may want to pull one of the spark plug leads and insert a spare plug, then ground the plug against the engine and turn it over with the starter to see if you have spark. If the spark setup is homemade like you reference, that's where I would concentrate your efforts.

Thanks for the tip, will check it next time it stalls.
Do you think the ignition would also cause poor power?

Yes. The problem could be the ignition coils. A simple test is the check to see if they're getting hot. run the bike at highway speeds, then stop & feel the coils --- press hard with your fingers. they should be warm, not hot. Also, make sure the spark plug connections are good & the ignitor & pulsing coil connectors are good & clean.

Battery. The bike needs a good battery to run right. never assume a battery is good, test it. a digital multimeter is preferable for checking the voltage. I do a high beam test (engine off). after charging the battery with a good smart charger, the voltage should be at least 12.6 VDC, but a good battery will be higher. Turn on the headlight high beam (engine off). if the voltage drops below 12.2 VDC, the battery may need replacing. if it drops below 11.0 VDC, the battery is probably shot.

Never hurts to KISS it.

Next time it starts loosing power pop the gas cap to see if the tank is venting.

Bill

Thanks for the replys, the bike currently wont start at all
Battery is brand new, just 2 days old.

Im thinking of just buying the whole Dynatek set and get it over with: DS2-2, DC1 and DW200
Does anybody have experiences with this setup?

Many thanks

You should do the fuel cap test & ignition coil heat check first, then report back before buying a new ignition.
If the fuel cap isn't venting, you'll need to clean it. If the coils are shot, you can get the green Dyna 3.0 ohm coils. then if the pulsing coil goes kaput, you could get the Dyna S later. The grey 2.2 ohm are a better match for the stock ignition system, but the green work fine.

What type of battery is it & did you properly service it before installing it on the bike?
Never assume a battery is good, even if new. test it with a multimeter.
I have a Scorpion AGM battery, Ctek US 0.8 smart charger & VC97 digital multimeter.

Another thing to check is the valve clearance. doing the check is fairly straight forward. changing shims is more work, but doable.

Valves had been adjusted?

Fuel cap is OK, the whole tank has been rebuilt and no vacuum when opened.
Bike wont start at the moment so no chance of getting the coil checked
Battery is Bosch and charged with intelligent charger CTEK.
Valves adjusted with brand new shims with proper clearance.

Thanks for the input, will keep you updated, next up are new coils
J.

Just curious - what model CTEK charger are you using? Ed

Im using the CTEK XS 0.8 cool little thing, highly recommended

Thanks! Ed