TOPIC:

I could use some more help from all the wizards on this forum. I put this in the Carburetors category but I honestly don't know what is going on.

Problem #1 seems to be solved by putting a new (Rick's) starter on my 1979 Kz1300 A1. With the Kz cold, hot and everything in between it seems to start fine.

Problem #2. When running down the road it seems to start backfiring and running on only 4 cylinders at some random interval of time. When this happens I pull over and bring it down to an idle, rev it up a couple of times, and then take off again, with no problems. Sometimes it happens again, some times it doesn't. 

It 'feels' like carburation but I honestly don't have a clue.

Thanks in advance for any suggestions.

George 

giorgi3 wrote:

I could use some more help from all the wizards on this forum. I put this in the Carburetors category but I honestly don't know what is going on.

Problem #1 seems to be solved by putting a new (Rick's) starter on my 1979 Kz1300 A1. With the Kz cold, hot and everything in between it seems to start fine.

Problem #2. When running down the road it seems to start backfiring and running on only 4 cylinders at some random interval of time. When this happens I pull over and bring it down to an idle, rev it up a couple of times, and then take off again, with no problems. Sometimes it happens again, some times it doesn't. 

It 'feels' like carburation but I honestly don't have a clue.

Thanks in advance for any suggestions.

George 

Try to find out which cylinders fail at the same time.
1-2, 3-4 or 5-6 is a carburetion problem.
1-6, 2-5 or 3-4 is ignition/coil problem.
I had a similar problem, sometimes losing two cylinders when the engine got hot.

Thanks kawaBCN. I'm not sure how to figure that out. The problem goes away by the time I slow down so it's hard to diagnose while riding.

Some of us old guys who rode 2 strokes would find themselves running on 2 of 3 cylinders. We'd pull over and check the exhaust header pipes and find the cold one and if you rode a Kawasaki 2 stroke, they had a complete set of 3 sparkplugs as part of the tools kit.
Checking the exhaust pipes was done with a finger by  first licking your finger and then tapping a exhaust pipe, then licking your finger again and tapping another exhaust pipe. The ones that sizzled were running and the ones that didn't sizzle (running cold) got a fresh sparkplug.
So that's the "roadside test"

You describe an intermittent problem as being a backfire, but I'm thinking your actually describing a misfire. A misfire happens when a fuel mixture  doesn't ignite in the cylinder under compression and then gets expelled into the exhaust where it comes in contact with the hot exhaust pipe and then explodes in the exhaust. This is usually an indicator of a lean mixture.

A backfire happens when the mixture gets ignited in the cylinder under compression and then leaks back in to the intake and causes an explosion in the intake. This happens when the intake valve has no backlash and the intake valve is slightly open. This usually is the beginning of a problem and not an intermittent problem.

What's probably happening here is a sticking float needle causing one of the three carburetors to run out of fuel and as it does the mixture goes lean and you have a misfire. Checking the exhaust pipes and finding 2 adjacent pipes cold would indicate a lean running carburetor as KawaBCN was describing. Running off the road and reving up the bike maybe just enough to jar loose the sticking float  and or float needle free.

Thanks for the advice Kawboy. I'm not sure about licking my finger and touching it on a hot exhaust pipe  .  How hot do exhaust pipes get on average? Maybe I'll by a temperature gun. Think that might work? Amazon has a variety of these temp guns ranging from ones that goes up from -58F to 1112F to others that go up as high as 2272F.



 

I just took it for another ride. I ran the KZ up to 5k rpm in each gear. Shifting from 1st to 2nd made a pop/backfire. I didn't notice it between the rest of the gears but I'm nearly deaf so it could be happening without me hearing it. It seemed to have lots of power in each gear as I throttled up. 

I then settled in to a steady speed in 5th gear at 3.5k rpm. After a minute or two it seemed to loose power. Throttling up didn't see to have any go. I drove it a short distance home, didn't rev it up at all,  and once home I used a squirt bottle of water to test the exhaust. Cylinders 1-2 and 5-6 sizzled. Cylinders 3-4 didn't.

Suggestions?