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1988 fz 600 misfire/elec probs

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billy_27
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Joined: 27 Feb 2009
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PostPosted: 17:36 - 31 Oct 2011    Post subject: 1988 fz 600 misfire/elec probs Reply with quote
myyamaha 1988 fz 600 as decided to be a pain in the arse.firstly its decided to bang and pop on over run and it feels to be firing on 3 cylinders and then back to 4 cylinders.secondly it just dies on me every now and again which can be tricky when over taking cars. basically i stop turn the ignition off/on till neutral light comes on then she fires up.this sounds like a electrical problem? maybe earthing issue possibly. any advice please Very Happy
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Kickstart
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Joined: 04 Feb 2002
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PostPosted: 17:40 - 31 Oct 2011    Post subject: Reply with quote
Hi

Not much info there, but it almost sounds like 2 problems.

Ignition off and on does sound like some electrical problem which is somehow being reset when the ignition is turned off (possibly even a dodgy ignition switch).

However most things in the electrics will affect either 2 or all 4 cylinders (2 coils, each controlling 2 cylinders, firing for both cylinders at once, one of which is a wasted spark each time).

First thing I would check would be the spark plugs.

All the best

Keith
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billy_27
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PostPosted: 17:54 - 31 Oct 2011    Post subject: Reply with quote
Kickstart wrote:
Hi

Not much info there, but it almost sounds like 2 problems.

Ignition off and on does sound like some electrical problem which is somehow being reset when the ignition is turned off (possibly even a dodgy ignition switch).

However most things in the electrics will affect either 2 or all 4 cylinders (2 coils, each controlling 2 cylinders, firing for both cylinders at once, one of which is a wasted spark each time).

First thing I would check would be the spark plugs.

All the best

Keith
hi if all plugs are sparking when i check them tommorrow does this mean the coils are fine or can one still stop working when the bike is on the road running prop.hope this makes sense?
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P.addy
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Joined: 14 Feb 2008
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PostPosted: 18:12 - 31 Oct 2011    Post subject: Reply with quote
They could stop running properly under load.

When did you last change the spark plugs?
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billy_27
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PostPosted: 18:27 - 31 Oct 2011    Post subject: Reply with quote
##Paddy## wrote:
They could stop running properly under load.

When did you last change the spark plugs?
i bet they aint done a 1000 miles
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 19:21 - 31 Oct 2011    Post subject: Reply with quote
billy_27 wrote:
hi if all plugs are sparking when i check them tommorrow does this mean the coils are fine or can one still stop working when the bike is on the road running prop.hope this makes sense?


Not 100%, but a good chance. One can stop, but I would expect that to affect 2 cylinders.

If you can trigger the problem find out what cylinder(s) it is happening on (spit on the exhausts and see which fizzes away the slowest), then swap the coils over (presume possible on the FZ600) and see if that changes the cylinder with the problem.

As an aside, when were the valves last adjusted?

All the best

Keith
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billy_27
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PostPosted: 20:56 - 31 Oct 2011    Post subject: Reply with quote
Kickstart wrote:
billy_27 wrote:
hi if all plugs are sparking when i check them tommorrow does this mean the coils are fine or can one still stop working when the bike is on the road running prop.hope this makes sense?


Not 100%, but a good chance. One can stop, but I would expect that to affect 2 cylinders.

If you can trigger the problem find out what cylinder(s) it is happening on (spit on the exhausts and see which fizzes away the slowest), then swap the coils over (presume possible on the FZ600) and see if that changes the cylinder with the problem.

As an aside, when were the valves last adjusted? cheers 4 the advice il spit away tommorrow Very Happy as for the valves ive no idea. im willing to have ago at certain things as for the valves thats out of my league but i know a man who can Very Happy

All the best

Keith
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temeluchus
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PostPosted: 23:23 - 31 Oct 2011    Post subject: Reply with quote
as keith says, if it is only a problem with one cylinder it is more likely to be a carburettor of mechanical issue.

first thing to do when you identify the offending cylinder, before farting around with the coils, is drain the float bowl in case water has gotten in there. Then check the spark plug cap-take it off the end of the lead and check the lead hasnt rotted. If it has you can cut it back a little until you find fresh copper.
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billy_27
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Joined: 27 Feb 2009
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PostPosted: 12:30 - 03 Nov 2011    Post subject: Reply with quote
Temeluchus wrote:
as keith says, if it is only a problem with one cylinder it is more likely to be a carburettor of mechanical issue.

first thing to do when you identify the offending cylinder, before farting around with the coils, is drain the float bowl in case water has gotten in there. Then check the spark plug cap-take it off the end of the lead and check the lead hasnt rotted. If it has you can cut it back a little until you find fresh copper.
hi checked the carb 4 fuel and there fine also took the end of each ht leads and re did them. bike still not right Sad the bike flys through the rev range but still bangs and pop on over run also been told it throws flames out Very Happy. bike is lumpy on tick over so need 2 blip the throttle 2 stop it stalling. i like to have ago at things but it needs looking at properly. cheers for the advice the 3 of u gave much appreciated Very Happy
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Snorty
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Joined: 13 Oct 2010
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PostPosted: 13:00 - 03 Nov 2011    Post subject: Reply with quote
billy_27 wrote:
Temeluchus wrote:
as keith says, if it is only a problem with one cylinder it is more likely to be a carburettor of mechanical issue.

first thing to do when you identify the offending cylinder, before farting around with the coils, is drain the float bowl in case water has gotten in there. Then check the spark plug cap-take it off the end of the lead and check the lead hasnt rotted. If it has you can cut it back a little until you find fresh copper.
hi checked the carb 4 fuel and there fine also took the end of each ht leads and re did them. bike still not right Sad the bike flys through the rev range but still bangs and pop on over run also been told it throws flames out Very Happy. bike is lumpy on tick over so need 2 blip the throttle 2 stop it stalling. i like to have ago at things but it needs looking at properly. cheers for the advice the 3 of u gave much appreciated Very Happy


Aye, nice big blue flame Razz
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jjdugen
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Joined: 03 Jun 2011
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PostPosted: 13:12 - 03 Nov 2011    Post subject: Reply with quote
Carb flooding. Trouble with this model and other Yams is that the carb is so steeply downdrafted that a flooding float lets fuel straight into the engine. Typical, dont know why but Yam carbs seem more prone to float needles sticking or leaking.
Always makes me smile to see the overflowpipes way above the float chamber, the engine would have to be full of petrol before they would do their job.
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billy_27
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Joined: 27 Feb 2009
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PostPosted: 16:12 - 03 Nov 2011    Post subject: Reply with quote
jjdugen wrote:
Carb flooding. Trouble with this model and other Yams is that the carb is so steeply downdrafted that a flooding float lets fuel straight into the engine. Typical, dont know why but Yam carbs seem more prone to float needles sticking or leaking.
Always makes me smile to see the overflowpipes way above the float chamber, the engine would have to be full of petrol before they would do their job.
.actually temeluchus suggested due to the age of the carbs i should buy a overhaul kit for the carbs. just today ive bought a new fuel tap kit cos its leaking from the tap and to be honest its been doing that on and off. were would the best place b to buy the new carb internals plus are the carbs the same as the old xj models?
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 17:21 - 03 Nov 2011    Post subject: Reply with quote
Hi

From memory one difference between the XJ and FZ setups was that the FZ got smaller carbs as there wasn't enough space to fit the XJ engine and carbs into the FZ400 frame.

All the best

Keith
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billy_27
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PostPosted: 19:59 - 03 Nov 2011    Post subject: Reply with quote
Kickstart wrote:
Hi

From memory one difference between the XJ and FZ setups was that the FZ got smaller carbs as there wasn't enough space to fit the XJ engine and carbs into the FZ400 frame.

All the best

Keith
they should of made the carbs smaller cos getting the air box back on is a complete nightmare talk about tight fit
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