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Thread: Firing order of Harley V Twin??
06-29-2005, 09:32 PM #1
In any V twin the pistons act like they are gong up and down in usinon (almost)
If I was going to work out the firing order, I would fire one of the cylinders on each revolution, that way I would have a power stroke every time around.
Sometimes the Harleys sound like they are firing both cylinders in sequence on one revolution and then both cylinders exhaust on the next revolution.
The four stroke V twin would work either way.
Does Harley do it both ways, for instance on different model engines?
Some sound different to me.
I have quite a bit of internal combustion engine experience, but absolutely none with Harley-Davidson.
06-29-2005, 09:35 PM #2
The firing order is 1-2!
The reason Harley's sound that way,and reun so rough, is they are not a 90 degree V and the cylinders fire at some screwy interval as a result.
It's a lousy design but don't tell Pauly....
06-29-2005, 09:37 PM #3
Yet another guy who doesn't know what he is talking about. The firing order is 2-1 Greg. [img]tongue.gif[/img]
06-29-2005, 09:39 PM #4
Sure - on the European Harleys!
06-29-2005, 09:49 PM #5
The traditional Harley engine fires very close to each other ,that basically makes it a huge 1 cylinder.That is also why they need the massive flywheel to keep things turning when it gets spinning.Great for low rpm torque and lousey for horsepower,but since they are built to drive on streets and not 1/4 mile tracks they do the job they were intended to do.
06-29-2005, 09:56 PM #6
It is 2-1. 405° from rear to front, then 315° from front to rear. There were a few experiments with flat trackers to make them fire 45° apart (called 'twingles') but all production bikes fire as above. It's the cam and exhaust that makes them sound different for the most part.
On edit: I forgot, it really is 1-2, but the rear cylinder is cylinder #1. At least that's what HD puts in their training manuals.
06-29-2005, 10:03 PM #7
It's 1-2, front cylinder fires, 315 degrees later rear cylinder fires, 405 degrees later front cylinder fires. John Deere two cylinders are more uneven firing. Number one fires, 180 degrees later number 2 fires, 540 degrees later number 1 fires again.
06-29-2005, 10:06 PM #8
Strictly speaking, if you are talking about which cylinder gets spark first, the answer is both. Modern Harleys with electronic ignition fire both plugs at the same time. It's just that one cylinder is on it's power stroke with a full intake charge, the other is not. A true firing order is only a factor if single fire ignition has been installed.
06-29-2005, 10:08 PM #9
06-29-2005, 10:13 PM #10
Does anyone here ride?
06-29-2005, 10:13 PM #11
Harley's sound like that because the cylinders share a common crank rod journal
06-29-2005, 10:21 PM #12
The note of a Harley, Ducati, Vincent etc. are the music to the ears of anyone involved in motorcycles over the past years. Nowadays, I can not discern anything due to all the clones running about. It is barely worth looking left to right to see what is going by. Years ago you could tell by the off cant beat just what was comming around the corner. If you want something firing 180 180 you need an upright twin. A multi is so smooth you only hear a buzz. The only thing that truely confused me was a Duke. I was riding this thing and it was so smooth I could not tell where they hid the rithym.
06-29-2005, 10:27 PM #13
I have an old Lincoln welder powered by a Wisconsin twin. Both cylinders fire in unison.
I thought it was strange until I listened to it for awhile.
06-29-2005, 10:52 PM #14
06-29-2005, 10:57 PM #15
Traytopjohnny "Does anyone ride"I used to have a 114 ci stroked Shovel.Delcron cases,axtell barrells,super G carb,ss Internals,single fire,dual plugged head........4speed 3inch open primary belt,chrome moly raked,stretched frame.And for the big guys KICK only.That was before I turned human and sold the bike to build a 30x100 foot pole barn.I still kept an old 1/4 mile vega to scare the crap out of me every now and then.
06-29-2005, 11:08 PM #16
As others here have said already most Harleys fire both plugs at the same time. The rods are both connected to a single crank pin sandwiched between two flywheels. One rod is forked at the crank (female)and the other has a male end.
They are pretty duarable considering the design. I have a built stroker Shovelhead in a FLH thats been pretty fun to ride.
06-29-2005, 11:35 PM #17
I've been riding for 39 years now. I got my first Harley, a 45" UL, when I was 15. Firbikrhd1 has it right when he said HD V-twins fire both cylinders at the same time with one piston on the compression stroke and the other is considered a wasted spark on the exhaust stroke. I'm think that the first twins produced in 1909 had this dual fire system, but I don't know this for sure. HD started using traditional breaker point ignition systems in 1936. The oldest one I ever owned was a 1939 61`" EL and it had the traditional dual fire points system. After market single fire systems are available which allow independent timing and firing of the two cylinders. The advantage of single fire systems is that they allow the motor to run a little smoother in the lower rpm ranges. Unless you are running a high performance bike you probalbly won't tell much difference above 2800rpm. I don't know much about the newer fuel injected systems, but I would suppose that they are a single fire system.
06-29-2005, 11:45 PM #18
HD had a dual point dual coil single fire contact breaker shortly before my 65FLH, but no one liked to fiddle with it, so most removed it and the factory discontinued it.
06-29-2005, 11:47 PM #19
A Wisconsin side by side twin, pistons go up and down together. Spark together, but one is on power stroke, one is on exhaust stroke. Look at the valve movement. 4 strokes every 2 revs. A spark every rev makes for a flame licker. --Doozer
06-29-2005, 11:51 PM #20
Donnie, is that a 65? I had one, if I remember right, the first year of electric start and the last year of the panhead. My first Harley was a 1950, a el 61?