TOPIC:

I'm building up a Z1000J for Historic road racing, the cut off date for this class is December 31st 1980 and even though Z1000J's were an 81 model they qualify as they were made and sold in Nov./Dec. 1980, any mods to the bike have to be of the period. Capacity limit is 1300cc so I was intending to resleeve the block and run 1260cc pistons and use 33mm Mikuni smooth bores I have, I was intending to use a dyna 2000 ignition but some stuff I read about Eddie Lawson's Z1000J he won the AMA superbike championship on had twin plug head using KX80 ignition parts. At a recent practise day I noticed a rider using a Z900 based engine running a twin plug head. I was wondering wether twin plugging the head is a really worth while mod as some of the quicker bikes still run single plugs per cylinder Any thoughts?

What does dual-plugging the head do, anyway? I know it's a common mod for perfomance z-bikes, but I'm unclear on the purpose.

The dual plug head will help the burn in a high compression [high piston dome]motor.

Eddie's bike ran a modified KX80 magnito setup for the ignition. No battery was required.

Call Muzzy's for details on the setup.

Personally, I feel you'd be better off with 33CRS Kehin carbs on the bike if you're going 1260cc.

Thanks for the explanation, Larry

I believe it reduces the chance of detination and allows you to run less ignition advance, 2 valve motors have to run the plug offset to one side, 4 valve motors like GSX1100's have their plug located centrally in the combustion chamber. Zepher 1100's had twin plug heads but I've read that was mainly for emission reasons.

Your probably right about using Keihin CR 33's as that's what most guys use as they're still available new, some use 35 CR's for faster tracks like Phillip Island where they run MotoGP and WSB races, I guess that gives away I'm from Australia. There are some very quick bikes running Mikuni 33's and I'll start off with mainly them cause I already have a set.

Post edited by: Russ, at: 2006/11/19 11:06

im gonna run a dual plug head on my 1385 motor mostly because i want to make sure it fires everything when its under boost.im mounting all my ectronics under seat where battery box used to be so the extra coils wont cause any clearance issues for me,now as long as nobody notices theres only 4 plug wires coming off that dummied up magneto:P

Where do you get a magneto conversion for a Z1? I have a friend, and now, possibly, myself a road racer. that altenator cover is going to get scraped for sure!

ive got a couple older bruce hahns im going to dummy one up to look functional but im actually using a dyna2000 for the ignition.the mag runs off end of crank where points cover goes so there is actually more parts in the open.

The piston pushing into the combustion chamber can mask the flame front travelling from the spark plug to the other side of the chamber. A second plug fires the unburnt mixture that gets masked by the piston crown. The advantages are a more efficient engine giving better fuel mileage, more power and less emmissions.

Fossil wrote:

The piston pushing into the combustion chamber can mask the flame front travelling from the spark plug to the other side of the chamber. A second plug fires the unburnt mixture that gets masked by the piston crown. The advantages are a more efficient engine giving better fuel mileage, more power and less emmissions.

I have no expirience with this, but does this(very crude) pic look right? I based it on your description

blue= unburned, red= burning
Scott

Post edited by: 77KZ650, at: 2006/11/19 19:56

The picture is pretty close to the idea, but squish areas are missing. Another factor to take into consideration is igniting the compressed charge.