FZR1000 missfire (or can you get NGK caps to suit bikes?)

**TonyB** · 23rd February 2005, 07:57

My 89 FZR1000 has an intermittent stuttering misfire from idle to 3000rpm. It’s fairly common with old FZRs, and even the YZF1000 (Thunder Ace) but the most common fault is a bad flat spot in the same range caused by worn emulsion tubes making the bike run rich- supposed to be a common fault with Mikuni CV carbs. My bike doesn’t seem to have that problem- I’ve had it on a dyno with a gas analyser and it actually runs slightly lean in the idle-3000 range. Plus the rich problem causes a flat spot, mine has a serious misfire. Normally this just isn’t an issue- I just keep it above 3k rpm, but it will be winter soon and it’s much easier to ride on very slippery roads if I can use the lower rev range. So I really need to get my finger out and sort it out.

I’m a member of the EXUP brotherhood http://p072.ezboard.com/bexupbrotherhood (very useful if you have an FZR of any sort or a YZF750/1000) and it has recently been suggested that the problem can be fixed by simply replacing the spark plug leads and caps. If it’s really that simple I’ll be relieved….and a little annoyed as I have spent a few $$ with two different shops getting this looked at (three different mechanics have told me you can’t replace the leads- not true apparently). Apparently the number 3 plug on the original EXUP engine gets wet , no ones sure why. This leads to corrosion of the plug cap, increased resistance and…stuttering misfires at low revs. I changed my plugs a few months back and definitely noticed that one of the plugs had white rust on it- think it was #3, so they could be on to something.

Anyway, my question is can you buy NGK resistor caps to suit bikes here in NZ (ie big looooong suckers with rubber seals etc) it’s been suggested that I do that rather than pay silly money for Yamaha ones.

If anyone has any further advice, I’m all ears. If you want further history I’ve got stacks of it…sigh.

**F5 Dave** · 23rd February 2005, 09:48

Hello brotherhood member

You always used to be able to buy fairly long ones. Get the bike shop to ask Darbi the NGK distributor. Might find the right p/n here

Changing the leads themselves isn’t possible I would think as they are moulded into the coil usually, but they are straight copper so unlikely to go wrong. Heard a good story about a chap who did have leads he could change & used some flash looking yellow carbon car leads. Had a misfire after that so he took it to dyno, where operator fixed the problem by putting the boring ones back on with new caps.

The caps however are very likely the cause. Try measuring the resistance. Each cap should be around 5-7k, so between 2 coils double that & a tiny amount for the coil. Take each cap off & measure it. A dud one will be 10 or 15k & it will cause a problem, or it might just be tracking through a crack to the ground.

The std ones do have the advantage of the seal, you might go see if a wrecker will sell you some & measure them. Then again he might not want to part good coils from the caps. How much are they new?

**TonyB** · 23rd February 2005, 09:57

Originally Posted by F5 Dave

Changing the leads themselves isn’t possible I would think as they are moulded into the coil usually, but they are straight copper so unlikely to go wrong. Heard a good story about a chap who did have leads he could change & used some flash looking yellow carbon car leads. Had a misfire after that so he took it to dyno, where operator fixed the problem by putting the boring ones back on with new caps.

Now this is what I'm worried about- pulling the leads out based on advice from the net only to find it really shouldn't be done, and finding I now have farked coils and a nice bill to pay. The advice came from canappa, who from memory knows his stuff. They certainly look like they aren't moulded in...
Thanks for the advice Dave, I'll try the caps first.

**vifferman** · 23rd February 2005, 10:06

Not that this is necessarily related, but like F5 Dave said, sometimes tracking through a crack can be a problem.

I had a problem with the Firestorm where it misfired sometimes, and on a really wet day it just about conked out. Then I read about another Firestorm owner who had misfiring problems and the shop found a very small crack in the plug boot, replaced the boot, and everything was sweet. So, I took my front plug boot off, looked at it, and there was a small crack in the rubber bit - looked like the boot had been pushed onto the plug cap one time and torn. Stuffed it I know how that could make a difference, as when it was on, the boot was in the plug well, and the crack was closed, and I'd sprayed heaps of moisture dispersant around it which should have kept the water out. But, I forked out some ridiculous amount ($64? or summat) for a new plug cap, and the problem disappeared.

**F5 Dave** · 23rd February 2005, 10:08

I’m going from memory on my 750, so the 1000 coils may be different (too many bikes & failing memory of which is which).

Maybe it is possible to remove the leads, but usually it is obvious that they clamp up. Either way when you wind the caps off you may need to cut 5mm off to expose some clean wire, then the lead should be fine & I can’t see any point to changing the lead. Note if they ever do get too short NGK do a cable extender.

**TonyB** · 23rd February 2005, 10:27

Cheers Guys. Just priced the caps- $51.60 each. A coil with leads is $180.35
Of course, I'm broke at the moment- so I'll try just chopping 5mm off the lead and see how that pans out. So if there's water getting down past the cap, is that on its own enough to cause a misfire?

**F5 Dave** · 23rd February 2005, 10:35

What & change the cap? I still think the cap is the problem. You used to be able to get NGK straights for, well not that much.

**TonyB** · 23rd February 2005, 10:50

OK, I'll change the cap too. Will have a ring around and see whats available.

**Posh Tourer :P** · 23rd February 2005, 11:42

I have 2 NGK caps, but thats on a bimmer, not a japper 4..... I would think you could get them though....

**R1** · 23rd February 2005, 12:01

Don at pitlane can get the long NGK's but this sounds simmilar to a problem i had on my old zxr750...i found spending the money on kawasaki ones was.... in the end the way to go, but tough call to make when ya dont have the money, good luck give me a call if ya get real stuck.

**TonyB** · 23rd February 2005, 14:22

Thanks Aaron. I rang Don and he can't get NGK caps that seal to the head, so it looks like it'll have to be the OEM part. Joy. Maybe I should steal one off that FZ1 you've got in your shed...kidding.

**XTC** · 23rd February 2005, 14:32

You could find a similar bike at a shop and take it for a test ride......... No do not do that!

**F5 Dave** · 23rd February 2005, 14:41

If it's anything like the YZF it would need to be a 'long' test ride as the carbs are well easy to get to but the sparkplugs are a bitch.

Obviously a joke though.

PS: stones like to collect in the plug tunnel area & it is a good idea to give them a blow out with compressed air if you have a compressor ($100 or something crazy from super cheap). Before I had one I used a vacuum cleaner & a peice of rad tube to suck the crud out of the hole.

Think it was easier to move the rad out of the way to get there,

by the way if you haven’t recently I HIGHLY recommend draining the coolant, removing the thermostat (which lives under the carbs) & flushing the system out with a hose both directions & put is back together (thermostat included) with new fluid.
They seem to discolour the coolant pretty quick & you don’t want to ruin the block or head or limit the cooling ability.

**TonyB** · 23rd February 2005, 15:05

There's a Thunder Ace for sale down here at the moment. Like you say though Dave, would need to be a long test ride. Not the sort of thing I'd do anyway.
I get in there by taking the tank off, airbox off and then remove the plate that the coils are on. Taking the radiator off looks a bit scary to me

I use a hose on the vacume cleaner to clean out the plug holes as well. Will have to drain the coolant sooner or later.
Thanks for all the advice.