www.zxrworld.co.uk

Bike is a zxr750 1991 J1

Had it started about month back, albeit using a makeshift home made tank (bit of wood with a container on it, and fuel pipe connected to spout on container ) bike run on choke and idled and revved nicely off choke too, obviously better again when i put airbox back on

So have had the tank off recently relining the inside of it and with the tank being bone dry and empty, i only stuck a fivers worth of fuel in to get it fired up, now should i stick the fuel tap to "on" or "reserve" given that a fiver isnt a huge amount of fuel and its been totally empty until today? (i think reserve is the fuel tap being rotated all the way clockwise until it stops)


Secondly, fuel has made its way into the inline fuel filter i can see it in there, although not a massive amount, but bike wouldnt fire up yet will crank. Lights and everything work and i suspect it was the battery as its on charge now and still not showing a full charge. And the crank did start to struggle after a while haha. (this was with tap set to "on" i think)

So 3 questions really

1. on or reserve with a fivers fuel from bare empty tank

2. given the bike was started a month or so back and hasnt been ridden or anything since then, and fuel has made it into the filter, would that indicate the fuel pump is ok

3. are these bikes really sensitive to any sort of drop in battery voltage/power

1. Either, £5 should fill the tank about a quarter of the way

2. Disconnect the fuel pipe to the carbs and crank the bike, this will check the fuel pump

3. If its like the 400 then yes, very much so

Yep you need a full charged battery, anything less and you'll struggle, have you checked or replaced the plugs ?

masterofinsanity wrote: ↑

Fri Aug 07, 2020 10:15 am

Yep you need a full charged battery, anything less and you'll struggle, have you checked or replaced the plugs ?

yeh bike started on full battery both choek on and off, but a mate says im running only on 2 or 3 cylinders

in regards to the plugs I have looked at the wiring diagram for the plugs and leads and have attached it so you can see. Number 4 plug from the red wire on left hand coil, is plugged into the 2nd cylinder hole according to the diagram, 2 is in 3rd hole, 3 is in the 4th etc

However on my bike im sure theyve been installed so that lead 1 is in hole 1, lead 2 in hole 2, lead 3 in hole 3

Not sure if its correct how it is now, or whether they need to be as i suspected, plug 4 in hole 2, 3 in hole 4 and so on

Basically you have 2 coils, ignore the red wires.

One coil will have a black wire going into it, you need to connect this coil to spark plugs in cylinders 1 and 4.

The other coil has a green wire going into it, you need to connect this coil to spark plugs in cylinders 2 and 3.

If you can get the bike to fire up a bit you can check to see which downpipes are hot, this will tell you how many cylinders are firing.

banner001 wrote: ↑

Sat Aug 08, 2020 4:49 pm

Basically you have 2 coils, ignore the red wires.

One coil will have a black wire going into it, you need to connect this coil to spark plugs in cylinders 1 and 4.

The other coil has a green wire going into it, you need to connect this coil to spark plugs in cylinders 2 and 3.

If you can get the bike to fire up a bit you can check to see which downpipes are hot, this will tell you how many cylinders are firing.

Thanks. Yes thats how they currently are so its correct. Had it looked at and is apparently only firing on 2 or 3 cylinders, so have bought a pair of new coils and leads. Plugs were checked and cleaned and they had spark i believe, so leads or coil(s) are gone.

Bike will start so thats a bonus. As you can tell im not the most mechanically gifted with bikes but what are the main signs of bad HT leads and/or coils

Ht leads you can see if they feel rubbery or hard, you want them to be rub ery and flexible.

Coils, you can get a multimeter and test the coils primary and secondary resistances, you can also test the plug caps the same way

As for faults, most of these components either work or they don't work, but with these components it's also possible for them to work when cold, but then break down and stop working when the components get warm

banner001 wrote: ↑

Sun Aug 09, 2020 12:43 am

Ht leads you can see if they feel rubbery or hard, you want them to be rub ery and flexible.

Coils, you can get a multimeter and test the coils primary and secondary resistances, you can also test the plug caps the same way

As for faults, most of these components either work or they don't work, but with these components it's also possible for them to work when cold, but then break down and stop working when the components get warm

Thanks for the reply. Apparently a friend of mine(mechanic) who came to help with the bike is putting it down to bad HT leads. Plugs were ok after he cleaned them, jets in carb and float bowls got a good clean and blow through; but the bike is firing on only 2 or 3 cylinders. So i have found a set of 2 coils and leads from a breaker, fully working, too. Not arrived yet though

Impresses me how people can hear an engine when a cylinder isnt running, to me i cant tell the difference!


If the HT leads are the culprit, is the engine sound going to be that much different when bike is idling normal/on choke