V-Twin 2 and 4 plugs

[glwilson]

I saw that too Kris.

Those guys were really surprised to see a hemi in that old bike.

[ringadingh]

Originally Posted by Netnorske

I watched a show last week where they were restoring a 1950's single cylinder Matchless Motorcycle for a guy. When they took it apart, they found it had a hemisherical piston that provided a lot of power....ala Mopar! Wonder why today's designs don't incorporate that feature?

Its hard to locate the sparkplug in the centre top of the head because of the overhead camshafts that are in the way on the Vulcan engines.

[snarleybill08]

hemi heads are by far not the ultmate head configuration. combustion chamber, and piston crown shape has become so hightech that many things come into play when designing combustion chambers. things like port angle, valve size, no. of valves, bore to stroke ratio, cam timing, and even alotted space for the engine. true hemi heads like harley and the old crysler hemis are archaic in design compared to the heads on the new crotch rockets and formula cars. most of the dual overhead cam engines have a lowprofile hemi design because of the valve angle. as was stated, dual plugs are often used to correct a combustion deficiency due to a design flaw that is there cuz there was no other choice. it could be the cause of pinging on the nomad, because it has faster combustion due to two separate flame fronts.

[blowndodge]

Absolutely Bill. I've been trying to explain this earlier. The older style of "Hemi" head are antiquated to say the least.

[Sin City Stan]

Originally Posted by dennis49

shoulda bought a Hemi.

Should'a bought a 1700. One plug a cylinder. Dead center. It's gonna suck when it comes time to change them.

[trosco]

Well Stan, I just swaped out (at 42,000 miles) my first set of plugs on the Nomad. I gaped the originals every 12,000 miles and really did not need to replace them but a local auto parts place had them on sale for $1.99 each so why not. I used a squirt of oil on the threads each time I gaped them so they spun right out. Checked the gap on the new ones and only one need adjustment then the drop of oil on the threads and spun them in. $8 and ten minutes time is all it cost me!

[Sin City Stan]

Originally Posted by trosco

Well Stan, I just swaped out (at 42,000 miles) my first set of plugs on the Nomad. I gaped the originals every 12,000 miles and really did not need to replace them but a local auto parts place had them on sale for $1.99 each so why not. I used a squirt of oil on the threads each time I gaped them so they spun right out. Checked the gap on the new ones and only one need adjustment then the drop of oil on the threads and spun them in. $8 and ten minutes time is all it cost me!

My point exactly. With the plugs are on the side of the cylinder gapping and replacement are a snap. When they're under the tank it's a different story.

[ponch]

Originally Posted by Blowndodge "Darksider"

twin spark plugs end up being used on engines who's head design and valve angle are poorly designed. Twin plugs allow a more complete burn because of this design...

show me a big bore diameter engine that runs two plugs and it will be a low power engine.

Nomads are over square meaning the bore is larger than the stroke of the motor. Our bore diameters are the same as a 110 cu in Screamin' Eagle.

Technically our Nomads could have easily been set up to run like a M109 Suk.... big bore shorter stroke more RPM's.

After seening all the low RPM strong torquing V-Twins out there I'm at a loss why the Nomad is a big bore V-twin...

My bike has two spark plugs per cylinder and it's not too shabby at 110 HP for 1170CCs... 101mm bore, 73mm stroke, 12:1 compression ratio. To answer your last question, longevity.

[ponch]

Originally Posted by trosco

Well Stan, I just swaped out (at 42,000 miles) my first set of plugs on the Nomad. I gaped the originals every 12,000 miles and really did not need to replace them but a local auto parts place had them on sale for $1.99 each so why not. I used a squirt of oil on the threads each time I gaped them so they spun right out. Checked the gap on the new ones and only one need adjustment then the drop of oil on the threads and spun them in. $8 and ten minutes time is all it cost me!

Shoot, get iridium plugs and you'd never have to change them again.

[blowndodge]

Originally Posted by ponch

My bike has two spark plugs per cylinder and it's not too shabby at 110 HP for 1170CCs... 101mm bore, 73mm stroke, 12:1 compression ratio. To answer your last question, longevity.

BMW boxer twins went to the twin plug set up sometime after 2002 when they were still 1150 cc because of the lean surge condition many owners reported that couldn't be tuned out of the motor.

[glwilson]

Originally Posted by ponch

My bike has two spark plugs per cylinder and it's not too shabby at 110 HP for 1170CCs... 101mm bore, 73mm stroke, 12:1 compression ratio. To answer your last question, longevity.

Porcupine!!!!!

[ponch]

Originally Posted by Blowndodge "Darksider"

BMW boxer twins went to the twin plug set up sometime after 2002 when they were still 1150 cc because of the lean surge condition many owners reported that couldn't be tuned out of the motor.

For the 1150 that was true. The 1200 is a bit different of an engine. My guess would be high compression and a large bore would have something to do with it. Funny thing is, one plug is in the center and the other is on the side. 2010-2011, they put the cams over the valves and use hemispherical shims. I think they are the limit for an air/oir cooled boxer and next year they are coming out with a water cooled version that has throttle by wire and a wet clutch. Bore is supposed to be the same, 2mm longer stroke, with power being about 125 and torque around 90. Should be a fun bike and even better suited to authority duty.

[ponch]

Originally Posted by glwilson

Porcupine!!!!!

Totally.

[ponch]

Originally Posted by glwilson

Porcupine!!!!!

When I tire of it I will come back to a V-Twin. ;)

[blowndodge]

I'm looking forward to the water-cooled boxer twin..