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Nevyn Kawa
26-05-07, 08:08 PM
What causes a backfire? is it flooding? should I be re-checking the spark?

In trying to start the bike (1980 Z750 E1), charged the battery to the max and simply tryed it both with and without choke just trying to get a decent kick. (I get enough out of the starter to get a few turns out of it)

long story short she gave a three inch flame and a bang that scared the $%#% out of me (especially as she is in an enclosed garage)

I assume I am getting too much fuel through? I have spark, I only recently removed and cleaned the throttle valve assembly and diaphram, did I do something wrong?

bear in mine I have got it (grudgingly) started half dozen times over last month. last time fired her up and rode round yard, have had starter and clutch cable problems so that was couple weeks ago.

wheelbarrow
26-05-07, 08:23 PM
Hiya Nevyn Kawa.
Sounds like you just flooded it and it could have bounced back of a compression stroke.
If you havenít started it for a while you will probably need more than a few turns out of the starter.
Got access to a good hill? Make sure you got a helmet if itís on the road.
Let us know how you go.

Nevyn Kawa
26-05-07, 08:43 PM
Hiya Nevyn Kawa.
Sounds like you just flooded it and it could have bounced back of a compression stroke.
If you havenít started it for a while you will probably need more than a few turns out of the starter.
Got access to a good hill? Make sure you got a helmet if itís on the road.
Let us know how you go.

don't have a hill but will have a few blokes around next weekend :D :D

if it is backfiring with the starter though, won't it do the same with a roll start? maybe the fuel isn't turning off properly.

wheelbarrow
26-05-07, 08:49 PM
Not if it's bounced back of a compression stroke instead of spining over that one more turn before it kicks and starts.

I could be way out, but always worth tring to clutch start if your batteries not winding it over fast enough.

Nevyn Kawa
26-05-07, 08:59 PM
True, will play and report later.

unless anyone thinks of something else.

planezrx
26-05-07, 09:59 PM
I don't suppose that a little pool of fuel forms anywhere near the bike while its been sitting there, or whilst you are attempting to start it?

Cheers,
Pete

Nevyn Kawa
26-05-07, 11:15 PM
I don't suppose that a little pool of fuel forms anywhere near the bike while its been sitting there, or whilst you are attempting to start it?

Cheers,
Pete

I don't think so. I say "think" because there is a slow oil leak and therefore I have permanently absorbing rag underneath.

however I think I know where your heading and I have been thinking similar. I haven't checked it yet but I think the diaphram in the fuel tap is stuffed. explains the flooding (backfire) explains why it started so well last time (had only just filled up tank)

To that end I have clamped the fuel lines (just hope that doesn't damage the lines)

Nevyn Kawa
29-05-07, 08:31 PM
Bloody fantastic!!

Roll start (took a few pushes) but yes she started.

Took it for strap, ten fifteen minutes. is going to need a bit of a tune up, it's got real go when you open it up but is poping and coughing a bit at low rev's. am guessing it's running too rich, I think just one Cylinder is out.

will play around and try and figure out which one is missing, could be just timing or something.

Nevyn Kawa
29-05-07, 09:24 PM
OK unlikely to be timing as timing is auto.

Fault section says low battery is likely to cause misfiring, this also makes sense to me as to why it ran so well at higher rev's. my assumption being is that the alternator is kicking in at high rev's and making up for a battery that has sat for too long.

Surprised though as it seemed to hold charge pretty well while trying to start. maybe just run down....

wheelbarrow
29-05-07, 10:04 PM
Is it starting with the started motor ok now? If so your batteries holding some sort of charge.
If you turn the lights on high beam at idle and give it a rev and see if the head light gets brighter in the dark so you can see it better, this will tell you the alternators charging fine.

Nevyn Kawa
29-05-07, 10:23 PM
Is it starting with the started motor ok now? If so your batteries holding some sort of charge.
Yes and no, still having the same problem with the starter chutch not staying engaged, difference being is I only shut her off a couple of hours ago. kicked over with only one turn, second attempt.


If you turn the lights on high beam at idle and give it a rev and see if the head light gets brighter in the dark so you can see it better, this will tell you the alternators charging fine.

Didn't notice that, either way (also wasn't looking for it) had no reason to thing alternator not working, was assuming for reason already mentioned that it was working. I didn't go far enough to make it give any difference to the battery.

Am pretty certain that the fuel tap needs replacing, fired it up and hour ago without turning on the fuel tap...... wreckers here I come :)

wheelbarrow
29-05-07, 10:26 PM
Good luck buddy.

Let us know how you go.

planezrx
03-06-07, 02:21 PM
Am pretty certain that the fuel tap needs replacing, fired it up and hour ago without turning on the fuel tap...... wreckers here I come :)

The bike will run on the fuel in the float bowls for a little while. Mine ran for 15 seconds with the tank removed from the bike! Don't just assume that because it ran with the fuel turned off that the tap is stuffed. Let it run for a few minutes (if it will) and then you can assume the tap is faulty. Better still... Disconnect the fuel line and turn the tap on and off. (I'm assuming here that it is not a vaccuum tap??)

My opinion is that you've got some bad fuel in the carbs and that they need a thorough clean out and the fuel thrown away.

Cheers,
Pete

MIKER
03-06-07, 02:35 PM
^^
good advice "pete" .. ;)