acceleration hesitation

So when I'm riding and pull the throttle all the way it takes seconds for the engine to get to high rpms. Is it a carb issue? The throttle response is terrible. I did mess with the carbs before but this has been a problem ever since i bought it 3 months ago. Idk how to pinpoint the problem. It's a 78 kz650b

A couple of possibilities. It could be the battery. Or the ignition coils.
If the bike has the stock points ignition, you may need to do some maintenance or adjustment.

The bike needs a good, fully charged battery to run right. I would charge the battery with a good smart charger, then check it with a digital multimeter & do a high beam test. If the ignition coils are stock, they're over 30 years old --- inspect them for cracks or damage. A simple test is to ride the bike at speed, then stop & feel the coils to see if they're getting hot to the touch --- press hard with your fingers. Also, check the plug wires for cracks n stuff.

Pinpoint the problem by working out is it carbs, ignition or something else. Cean the carbs and noting the main and pilot jet sizes, fuel levels and needle position. Then synch them. With a 4-1 pipe and pods the carbs need setting up, plenty of info here about it.

If not carburation, then check the ignition, particularly strobe checking the timing and advance. Crimp connectors to coils under the tank and spark plug leads and caps should be replaced.

martin_csr wrote: A couple of possibilities. It could be the battery. Or the ignition coils.
If the bike has the stock points ignition, you may need to do some maintenance or adjustment.

The bike needs a good, fully charged battery to run right. I would charge the battery with a good smart charger, then check it with a digital multimeter & do a high beam test. If the ignition coils are stock, they're over 30 years old --- inspect them for cracks or damage. A simple test is to ride the bike at speed, then stop & feel the coils to see if they're getting hot to the touch --- press hard with your fingers. Also, check the plug wires for cracks n stuff.

I have a dyna ignition system and the battery is brand new

+1 to Tyrell: Do all of that.

I assume you have a Dyna S ignition? What coils?

I had a new battery but a badly wired signal flasher, relay, and voltage regulator from the previous owner caused it to drain very quickly.

Martin, what's the high beam test?

The high beam test is a way to load test the battery.

Engine off. Charge the battery with a smart charger & test it with a digital multimeter --- it should be 12.6+ VDC. Disconnect the charger. Turn the ignition switch to ON & turn on the headlight high beam, but don't start the bike (engine off). The voltage should drop then slow or stop. A good battery will drop to around 12.2 VDC, but ~11.85 is okay. If it drops to 11.2 or so, the battery may need replacing. If it drops to 10 VDC or thereabouts or worse, the battery is shot. The voltages are the numbers I use --- there may be a more accurate chart on the internet. The high beam test removes the surface charge & gives a better indication of the battery's deep charge or something like that. The care & feeding of your pet battery.

I talked to a Harley mechanic that knows jap carbs and he said my issue is varnish build up inside them. He said one of the jets has to be gummed up. He they are known for that issue. He said it's $300 to sync and clean them.

300 bucks sounds a bit excessive to me, don't be paying franchise main dealer money on simple air cooled machinery like this. If the carbs need upjetting then it involves a bit of trial and error, more $$$...

Your problem is most likely the carbs, but it could be elsewhere. This is where you pinpoint the problem, by working thrugh all the possibilities. All carbs varnish if stored for any length of time, motorcyles particularly sensitive with the multi carbs and tiny pilot jets etc.

You can accomplish the same carb cleaning and syncing with a $20 can of chem dip, compressed air and a 1mm wire (for bench sync). Then borrow or buy a $100 carb sync tool if you really want to go all the way.

Then you'll know what jet sizes you have, where your needles are set, etc...
Yes, it might easily take a weekend or more, but you'll know your bike.

300 bucks - was he gonna polish them as well .

Tyrell Corp wrote: 300 bucks sounds a bit excessive to me, don't be paying franchise main dealer money on simple air cooled machinery like this. If the carbs need upjetting then it involves a bit of trial and error, more $$$...

Your problem is most likely the carbs, but it could be elsewhere. This is where you pinpoint the problem, by working thrugh all the possibilities. All carbs varnish if stored for any length of time, motorcyles particularly sensitive with the multi carbs and tiny pilot jets etc.

Well I know nothing about carbs and I'm tired of dealing with this bike. He's not a Harley dealer. He's deals mostly with them tho. I'm not confident in doing anymore disassembly to this bike. Its cursed.

Buy an old bike, get your hands dirty or have very deep pockets. It costs loads more to restore an old nail than an newer bike.

My concern is $300 later you might just have another list of things to do and a bike that still won't run right. No mechanic however honest and skilled can guarantee that.