gpz750 starting/runnimng probs

[gremlin6976]

hi all' got a gpz750 but wont start on button turns over but wont fire up will bump (after a lot of pushing) and wen running thers a huge loss ov power. wen you open it up it just starts to shudder then die
could it be the cdi? as had a simler prob on a cx and cdi was to blame
any help plz?

[lowrider]

Has it got a standard exhaust and air box?

[gremlin6976]

hi it's got a 4 into 1 exhaust and the standard air box

[lowrider]

Umm,my first thought was a open exhaust and/or K&Ns or something like that.
Have tou gone through the systems and checked them?
As in fuel is getting through in a good flow,the colour and quality of the spark.
The basics to ensure they are covered

[Grav]

It could be a coil on the way out or something really simple like a plug or two fouling. Do the easy stuff first. Clean the plugs and check the gap is right. Check them for a spark and if it's a weak one then a new set of plugs could cure it. If the filter is a foam one give that a good clean and dry it thoroughly. Also drain the carbs and check for sediment in the bowls, it's easily done with a piece of clear tubing and a clean jar. How long has the fuel been in the tank? It could be stale fuel causing it so drain it or stick a gallon of fresh fuel in to freshen up the old stuff and shake it about a bit to mix it.

What year is the GPz?

[gremlin6976]

plugs are sparking and the petrol is getting to the carbs. the power loss and shuddering wen opened up only started today on the way back from town but the starting prob has gotten worse over the last few weeks ohhh and its a 85 unitrack

[strima]

Leaking carb rubbers?

[gremlin6976]

nope there all sound

[Grav]

It sounds more like a fuel starvation problem than an electrical one, but I have known Kwak coils to fail under load.

[wodda]

I had a similar problem with my GPZ600R which turned out to be nothing more than a dodgy supressor cap. Could just be a coincidence but it happened on my mates 900 as well.

[lowrider]

Plus worth checking by feeling the exhausts pipes to see if there is one cylinder not running right,or all of them.
Might give yo a hint

[harry]

Plus worth checking by feeling the exhausts pipes to see if there is one cylinder not running right,or all of them.
Might give yo a hint

That'll be soon after starting from cold.

Health and safety mode Off. :whistle:

[gremlin6976]

just had a fart about with it n got it started after a while took it down road and power was back but then died again wont run on tickover either:mad:

[lowrider]

That'll be soon after starting from cold.

Health and safety mode Off. :whistle:
Yeah i did think about saying that but i also find a squeezy bottle full of cold water can be used instead

[devon-tony]

I use a laser/infra red thermometer :)

could be the battery, when it cranks over is it quick or labouring

the starter draws so much current that a lot of the time the ignition circuit etc wont be receiving the correct voltage when the battery gets pulled down too low, while cranking the starter

[Grav]

Yeah i did think about saying that but i also find a squeezy bottle full of cold water can be used instead

I use a damp cloth. :cool:

[brayanaustin]

It is easily done with a piece of clear tubing and clean jar. How long was the fuel in the tank? It could be gasoline former leading vacuum or bury a gallon of fuel cost to revive something old and a little shake to mix.

[j.b]

i've also had issues with coils breaking down under load, handy if you can get hold of another set to try.......or.....
if the carbs look to be working ok then i'd check your valve clearances

[mick2]

also worth trying new plugs, although they are sparking outside the engine it doesnt mean they will be working correctly under load. seen a few duff ngk's like that.

[minxy]

Losing throttle power or electrical? Is it holding charge? .... alternator?

[Grav]

seen a few duff ngk's like that.

Yep, had a few myself. It's cured with a blowtorch, burn the crap off and brush off the shite a brass brush and reset the gap. That will get you another couple of thousand miles, but once they do it the first time, you just know it's going to happen again.

[mick2]

ive had them do it from new grav. that really fucks you up as you assume they are fine and start looking elsewhere.