What to check next?

[Strika]

My last ride was cut short with the 1200 dropping back to a 900!! I have since replaced the plugs and drained the float bowls with the problem remaining. It starts and idles fine, but as soon as I ask some throttle load of it, it collapses onto three. The offending cylinder is #1, as the header pipe is touchable when the others are hot. I want to use carb removal as the last option and would like to check the spark first. So, for all you guys who are good with the smoke in the boxes, what is the next electrical check?? The coils and leads are more easily accessible than the Carbs, so I would like to check they are working OK before I go pulling off the carbs. If I have to pull off the carbs, I might stick one a jet kit in it like the Woose did with his. It seemed to clean up the delivery even with a std pipe???????????????

signed
Don't let the smoke out of the box!

[Stereo]

Have you done the old "pull the spark plug out and see if it sparks" trick? Just pull the plug out, hold the end against the frame and then turn the wheel one rotation while the key is on... you should see a visible spark.. If'n you get no spark replace the lead that goes to the coil.... and try again...

[Stereo]

Someone correct me if I am wrong, but if the plug is sparking but not getting fuel it should be dry, if it not sparking but getting fuel it would be wet (if you have run the bike on 3 cylinders recently).

[Stereo]

Sticking in a jet kit wont affect performance... the idea behind a jet kit is to give you adjustable needles... which allows you to make the mixture richer or drier... so by default if you set them up as "factory" it wont affect it at all... However, dynajet have a chart somewhere with their "recommended" settings which should offer some improvement with a standard exhaust.

[Strika]

Sticking in a jet kit wont affect performance... the idea behind a jet kit is to give you adjustable needles... which allows you to make the mixture richer or drier... so by default if you set them up as "factory" it wont affect it at all... However, dynajet have a chart somewhere with their "recommended" settings which should offer some improvement with a standard exhaust.

Yeah I get that bit well and truly thanks mate. It's just the smoke in the boxes I struggle with. Motors, carbs, gearboxes, suspension and brakes are all quite acceptable to my mental processor, but throw in electricity and it overloads and shuts down on me??????


As for spark, it must be getting some spark as the header warms up, just not very much. I am away in Canberra and then Sydders for a day and Gosford till Friday next week, so I can't do much till I get back, but just wanted a simple check for the coils. It has spark I have already checked this with the new spark plugs when I installed them. But, it's loaded that casues the issue. Is it possible to swap the coils from one side to the other or are they unique? Surely you can just unplug em and replug them into the other HT leads????? Or am I being simplistic???

[Frank]

What Sterio said , but if your not getting spark then swap over the leads to a differnt coil, if it starts to spark I would then look at the coil or the supply to the coil as being the problem, then you can swap the coils around to see if the problem travels to another cylinder, it should narrow it down to the coil or lead or supply to the coil. It'll be easy to swap out if it's the coil ot the lead.
If it the supply to the coil, check all the connectors and plugs on the wiring loom. If you still haven't found it get an auto sparky to have a look at unless you enjoy chasing wiring through the main loom looking for broken wires or dodgy earths.

You should be able to see if it's a weak spark campoared to another cylinder as well.

[Benno]

From what you've described Marty, I'd take a stab and say it's either a dud coil, or you have a lead that's breaking down (which I've had happen before.) Just as Frank has said, swap with another coil and test. If that fails, I'd go out and buy a new set of leads and whack them on. As I said, I've had an instance in which something would idle ok, but as soon as you gave it some throttle, the lead would break down and fail to fire. I've also had the same happen with plugs themselves, where they break down and start sending the zap over the outside of the spark plug instead of through the middle creating a spark. But if you've change the plug and it's doing the same thing, then you've eliminated that

[MickLC]

I have to agree, if you want to make sure whether it's to do with the electrickery or not, the easiest would be to check for spark and confirm whether the plug is wet. You could also try swapping around the coils to see if the problem moves with it.

Still kind of sounds like a carb problem to me though, but then my point of reference is dicking around with 33-year-old Mikuni round slides, so I don't know that I can help too much

[Stereo]

Is it possible to swap the coils from one side to the other or are they unique? Surely you can just unplug em and replug them into the other HT leads????? Or am I being simplistic???

You cant just swap leads.... the cylinders are all timed.... so it fires for example cylinder 1, 3, 2, 4.... etc.... if you swap the leads the engine wont run because the cylinders are firing in the wrong order.... I think it would also fuck your engine if do it for too long, but dont quote me on that, I tried to get mine running for a full 5 mins before I realised they were in the wrong order and the engine was fine

[MickLC]

Do the ZRX's have coil-overs or two coils doing two plugs each?

[Stereo]

Do the ZRX's have coil-overs or two coils doing two plugs each?

Thats a question for the ZRX owners club http://www.zrxocboard.com/board/

[Strika]

Is it possible to swap the coils from one side to the other or are they unique? Surely you can just unplug em and replug them into the other HT leads????? Or am I being simplistic???

You cant just swap leads.... the cylinders are all timed.... so it fires for example cylinder 1, 3, 2, 4.... etc.... if you swap the leads the engine wont run because the cylinders are firing in the wrong order.... I think it would also fuck your engine if do it for too long, but dont quote me on that, I tried to get mine running for a full 5 mins before I realised they were in the wrong order and the engine was fine

Mate, maybe I have come across more of an idiot than I intended. I realise each lead must go to the correct cylinder. But I was sure this was routed from the CDI through the coils. So was asking if the coils could be swapped to the other side to eliminate the coil being the issue before a carb strip. ie provided I connect the correct wires from the CDI to the coil. I realise if I just swapped em without changing the CDI Wires it wouldn't run. But are the coils unique to each side was what I was more asking??? It's just that getting the Carbs on and off a Rex is not the nicest job ya wanna do, unless you do it 30 times a day and are well practiced. Otherwise it's along, slow, fiddly process and often frustrating process. There isn't a lot of room down there. Draining the float bowls was frustrating enough!!! So I am just trying to eliminate issues as I go and the coils sit right under the tank and are easily accessible. As are the CDI wires and the plug leads..relatively. So was thinking that if I swap over the coils and the prob changes to another cylinder, then I have my answer. While I will check the HT leads, it is a rare thing that they would go on an 8 year old 40k bike. But As I said, I will check them at some point to eliminate that as a cause.

To answer your ? MickC, the rex has two seperate coils, not individual coils for each cylinder like later stuff.

[Strika]

I have to agree, if you want to make sure whether it's to do with the electrickery or not, the easiest would be to check for spark and confirm whether the plug is wet. You could also try swapping around the coils to see if the problem moves with it.

Still kind of sounds like a carb problem to me though, but then my point of reference is dicking around with 33-year-old Mikuni round slides, so I don't know that I can help too much

This is now my prime suspect too Mick. I am just rying to eliminate everything else along the way to removing the carbs!!!!!

I suspect once I pul them off and give them a good clean the whole thing will return to normal service. I just really don't want to!!!

[MickLC]

...To answer your ? MickC, the rex has two seperate coils, not individual coils for each cylinder like later stuff.

Well it's not the coil then otherwise it would take both of the plugs out.

[Six Addict]

ahh gentlemen we have a thinker here