South West Bikers | Motorcycle Forum

I'm still having problems getting cylinders 1 & 4 firing and its really pi$$ing me off

So far, I've tried switching the coils over, switching HT leads over with the coils, changing a coil with a second hand one, electrically testing the resistance in the primary and secondary windings (all ok) and testing that there is resistance in the wires leading up to the CDI box. All wires seem to be working fine.

I took the spark plugs out recently, having replaced 2 with new ones (still no joy) and the plugs in 1 & 4 seem to be a bit oily as opposed to lightly covered in carbon. Nothing major. Anyway, I gave them a clean, checked the distance for the ignitor, put them back in and still nothing in 1 & 4.

CDI boxes for H model ZXR 400's are about £50 new and rare as rocking horse poo on eBay. If it is the CDI, how do I know/test if its faulty before I buy one?

Anyone got any ideas as to what the problem might be and how I can sort it? I'm really at a loss

Very unlikely to be the cdi if its only affecting two cylinders. And as 2 and 3 are ok that rules out the pick up. You tried a compression check on the cylinders?

how many signal generator/stator pickups are there on that bike? if theres two, and you've checked everything else, maybe you have a faulty coil on one of the stators? if there's 2, each pickup would signal for one coil/pair of cylinders so might explain one pair going down yet not being affected by swapping ht/lt leads on the coils.

look for 4 wires coming out of the crank casing somewhere near the crank - one of the outer engine covers will cover the pickups. you're looking for two coil-y things with two wires coming out of each, centred around a rotor on the end of your crank.
check the resistance of each - should be the same

I would also say do a wet and dry compression check.

The CDI is only £50, if you think thats faulty just replace.

CvPiper wrote:The CDI is only £50, if you think thats faulty just replace.

That's like a weeks wages!

Ok, fair enough ;)

ringsssssssssssss, check compressions. then carbs, make sure fuels are getting through jets and so on.

Just out of curiosity, how would I conduct a compression check?

I've drained the carbs before and I'm pretty sure there's fuel getting to them. How would I know if fuel wasn't getting through?

the "oilyness" on the 2 plugs is probably just them fouled with petrol through not firing. if your rings were that badly worn you'd be burning oil and smoking a lot too.

you need a compression tester to do a compression test - just screws in to the plug hole and you turn the engine over. you normally do a "dry" test - just plug in and turn over - and a "wet" test - with some oil poured down the bores. point of the "wet" test is to establish if, if theres any loss of compression whether its in the bore (the oil will stop some of the loss around the rings) or at the top end somewhere.

be very surprised if its fuel supply to the outer two carbs stopping it running too - i'd have thought the carbs are fed with a t-piece between carbs 1+2 and 3+4 so if 2 and 3 are running then there should be fuel getting to the other two as well

^^^^ what he said. lol.

i would recoomend chcicing jets and things. if all else fails. remove the carbs and strip the bowles of. its not too hard just remember where everything goes. lol

turn it over, i'm guessing it starts and runs on two cyclinders? just?

well do that shortly, then take out your plugs that dont work, and see if there wet, sniff them, if its petrol on them then your fine on that side, if there dry, then its probably blocked jets or gummed up carb?

but you said they were oily?

have you tried heating the plug tip then putting it back in?

what happend when the plug is out and you hold it against the block (holding the rubber bit!!!!) and you turn it over? do you get a spark then??

This is why i got rid of mine, constant f**king stupid problems. Awesome bikes but electrics are shot.

I did a compression check on mine and it was shocking, only like £15 to get done at a shop if you dont have the tool.

Good luck mate

have a clean of the carbs just incase (cant do any harm) they strip down nicely and if you need to you can get the cd guides on ebay for about a quid that shows every part of the bike broken down into component parts. If it fires on 2 cylinders then I doubt you will have huge engine problems and by the sounds of it, this is more an electrical problem which is where I usually swear lots! Sounds like you have a tester so get it out and start testing everything! Check for a spark as metioned before, could just be teh head on the HT lead isnt quite screwed down properly. Best bet is to start by checking through all the wiring and making sure it's all good.

Interesting points raised by all, so thanks for the feedback.

I've done a dry test (I think?) where I'm putting the plugs in the HT leads and turning the engine over. The old man said he could see sparks but faint ones?

The dry plugs are 2 & 3. They seem to be screwed in properly but I can double check this.

I'll take the rocker cover off and see whats underneath, I've never seen one underneath before! Spoke to one guy and said there was a tube that had disconnected when he had a similar problem once, I'm guessing this is your T-piece, Chris?

Also, I'll give the carbs a clean this weekend. Can anyone recommend any carb cleaner that I can use?

And I was hoping to get a tan down the beach tomorrow too