GSX400ZR Impulse 3 & 4 not firing

[mosschops13]

Hi Guys,

I'm sorry if this is in the wrong section, there doesn't seem to be a dedicated area for this bike. However, the engine and carbs etc are pretty much identical to the Bandit so I am hoping someone can help.

This bike was running well last year, but on pulling out of winter storage (wife's bike and a fair weather rider) it was ropey on tickover. It has now progressed to the following:

1 - Good firing
2 - Good firing
3 - sometimes fires
4 - dead as a doornail

What have we done already?

Compression test - smack on the money and even across all bores.
Tappet gaps - identical across inlet and exhaust valves
Perished carb to tank vacuum tube replaced
Plugs and HT leads replaced
Coils read correct resistance across primary and secondary coils
Good spark from all four plugs
Carbs removed, thoroughly cleaned and O rings replaced and carbs refitted
Fresh fuel before carbs tested after cleaning.

If the dead bores were 1 & 3 or 2 & 4 this would be relatively easy - coil. However the misfire is spread across both coils. The only common thing I can see from the wiring diagrams is the pickup sensor and igniter box. I cant see it being the pickup as 1 & 2 are fine.

I am pulling my hair out and desperately need advice, even my very competent mechanic is baffled!

Anyone in the Poole area got access to the Suzuki Igniter Box test kit? If you are within 100 miles of Poole I am willing to bring it to you just to prove the damn thing!

Thanks

Mosschops13

[Variablevalves suck]

Hi Moss,
Carnt be the cdi as they run wasted spark and so if it fires on 1 it will fire on 4 with good spark plugs. If its the pick up sensor the sparks will be yellow and not sharp/blue and the resistance is 90 to 120 ohms. I'd put all my money on the pilot system within the carbs, i'd reccheck this and make sure the pilot screws are set up correctly with o'ring, washer, spring and screw is this order.

[mosschops13]

Thanks for taking the time to answer.

As it turns out you weren't too far off the mark. The diaphragms, whilst intact and no leaks were baggy and weak, therefore shutting off the fuel. 4 new diaphragms and it lives!

Regards

Greg

[Variablevalves suck]

Nice to hear you got it going.