TOPIC:

Hi
I am a new member but have had Z1300's for nearly 20 years now. a few years ago my black 81 had a couple of valves changed ( cam chain tensioner problems) and shortly after that it gave a backfire and is unreadable. I have pulled the carbies apart and cleaned everything and just started it after two years but the problem still remains, I am very frustrated as I dearly love the old girl and would like to have here going again. when it runs it won't accelerate past idle and when idling bangs and carries on with puffing and snorting

there are not too many experts over here in Western Australia and I really don't want to push her to the back of the garage for another interminable period, any help would be appreciated
regards
Jim

ps I also have a green 80 model but that a long term project

Hi Jim welcome to the forum.
Sounds like a very good description of crossed plug leads. I know it sounds like a simple solution but all of us have made some crazy stuff ups at times. Also check that the ignition triggers are connected to the right set of coils, it's one of those things that can happen after major surgery and you look right past it because it is such a simple thing.

.....Just clarifying....The bike never ran right after the valve work ?....if the previous suggestion checks out good go back and recheck cam timing and do a compression test on all of your cylinders to verify that they are in spec. hopefully plug wires,or primary coil wires are amiss.

I'm with Lucien here. Go back and check the timing. You could have jumped a tooth on the timing chain again if the tensioner back off.

A quick check for the timing of the spark (to confirm that the ignitors and coils are wired properly) is to pull the sparkplugs and then hook up plugs to the leads of 1-2-3 . Lay the plugs on the valve covers for ground and then turn on the ignition and turn the engine over on the starter. You should see the plugs fir 1-3-2, 1-3-2 or better (easier to watch for ) 3-2-1, 3-2-1. Your brain will like to watch for 3-2-1 better than 1-3-2, 1-3-2. It all the same thing.

Since it's not run for a couple of years, you should shine a light down the bores and look for rust on the liners. Knowing that there's always valves open during the rotation of the crank, there's an opportunity for atmosphere to flow in and out of the engine through the exhaust pipe and carburetors. Fluctuations in the outdoor temperature will cause the engine to breathe and with air comes humidity. You don't want to fire up an engine with rusty bores period.

Another thing you should check is the water pump drive shaft chain which is also the drive chain for the timing advancer. It's another chain drive with a tensioner. Nobody ever talks about it (wonder why?)

If you have reasonable compression and spark firing at the right time, then you next need to look at the carbs.Even if it runs shitty on idle and you start to open up the throttle and it backfires and dies usually points to no fuel on transition between idle and main jets.

My money though is going on a timing issue. it ran, then backfired then died. Either the ignition timing jumped (water pump drive chain) or the cam timing jumped.

The term backfiring is often misused. Backfiring happens when the explosion backfires out the carbs which can only happen when the sparkplug fires when the intake valve is open. some people refer to an explosion out the exhaust pipe as a backfire when in fact it's not a backfire. It usually happens when a spark plug is dead and raw gas is pushed out into the exhaust pipe and then another cylinder which just pushed out it's still burning exhaust ignites the raw mixture in the exhaust pipe causing an explosion.

Anyway, hope some of these thoughts help. good luck with your problem. Keep us in the loop.

Kawboy