'bom-bom-bom' or 'babom-babom-babom' / Firing order of XZ550

[martijn]

Hi all,

Just wanted to know if anyone out there knows the firing order (firing cycle) of a stock '83 XZ550?

With firing order I mean how far apart the cyclinders fire (in degrees).

Example: The pre '96 yamaha TDM 850 used a 360 degree firing order (giving a 'bom-bom-bom' sound).
The later TDM's apply a 270 degree firing order, much like ducati's, which give a more 'babom-babom-babom' sound (and smoother running, better traction they say).

How's this for the XZ550? When I listen my mind tells me it's 'babom', but it could just as well be 'bom' ??

(a search revealed a post on 'torque monster', very interisting, but not the hard data I was looking for)

[Lucky]

I'm not great at this stuff, but I know the cyls are set 70 degrees apart & the TCI system is wasted spark so it fires every revolution

so 290?

[martijn]

That could very well be !

I was just reading http://mcresourcesusa.com/info2-TN270.html where they say:
"What gives the V-twin its "thumping" exhaust note? The Harley V-twin has a 45° angle between the cylinders and uses a common journal for both connecting rods.  The single journal means the firing order has to be 315°."

The XZ has a common journal as well, so I think your're right: "babom" (@ 290 degrees) it is!

[The Prophet of Doom]

XZ550 Firing Order

[YellowJacket!]

I saw the title of this thread and thought of the "Black Eyed Peas".  8D

David

[Lucky]

Roro, where did you get that chart?

[The Prophet of Doom]

It's off the XZ550 Service Guide (Oct 1981) for European Market - I sent you a copy to include on the CD

[Lucky]

Ok, I thought it looked familar, lol

[YellowJacket!]

That might explain why my tach on my electronic gauges acts wonky.  I have it hooked up to the sensor wire that feeds the stock tach but my RPM's on the gauges read only intermittently.  I think I may need to go back to the manual and figure out which multipliers (not sure of the term but it allows me to select how many sparks/cyls etc) to use to get a continuous reading.

David

[The Prophet of Doom]

If you are counting revs, then keep in mind that for every 4 strokes the crank rotates twice.  I'm fairly sure they spark on the in-between strokes also (wasted spark),  although not shown in the diagram that way.

If I'm right there is probably no reason that martijn couldn't rotate his overhead cam 180 degrees to get both cyls firing 70 degrees apart.  Then it would sound and shake more like a Harley. 

[auto]

Sorry,I've had a few beers.I want to go for a ride on my XZ tomorrow.Do you think I 'll be OK with my firing order

[Re-Vision]

Yamaha shop had my bike firing both cylinders on the same revolution and it would barely do fifty-five MPH.   I still dislike those bastards.   BDC

[inanecathode]

http://www.youtube.com/inanecathode#p/u/13/NuKmlMsEfJY

Like that.

[fret not]

Vision fires both cylinders each rotation of the crank, that is why they call it "wasted spark".  The timing is set and there is no adjustment unless you alter the mounting of the pluse/trigger coils or the key shears between the crank and flywheel.

[Rikugun]

inane - Love that TT500, that's one nice thumper!

[inanecathode]

inane - Love that TT500, that's one nice thumper!

Yeah, i love it. It just, works. Burns oil like nothin when its cold but it just kicks ass offroad. I've done some seriously un-wise things with it and it comes out of it just fine, still thump-thump-thumping away. Different tank on it now, stock is a 1.2 gallon mx deal, now its got a 3.2 gallon clarke tank, exhaust is actually attached to the bike, side covers, proper air filter, and if i need the space two huge dewalt boxes that hold up to 6 gallons of milk weight wise and half a dresser of clothes size wise ;) Looked forever for that exact bike (500 four stroke) and i got one ;D

The rd on the other hand, i love it to death and i just wish it would function but it just recently seized AGAIN (third time in a season and a half) this time because one of the oil injector lines came off (im not going to premix, screw that) and i didnt notice until it stuck. Then, just about an hour ago, i go outside for something and i find the rd blown off the side stand and over onto the vision, breaking the rd mirror and curling the brake lever over.

[Rikugun]

The larger tank seems like a usefull upgrade to something as thirsty for gas as it is for oil!  :) Love the exhaust note too btw. Didn't Stallone leave town on the on/off road version in "First Blood"? Of course with 2-stroke sounds dubbed in.  >:(
I read elsewhere regarding your RD top end woes - sorry to hear about that. Other than the oil line mishap what do you think caused the prior siezed pistons?

[inanecathode]

The larger tank seems like a usefull upgrade to something as thirsty for gas as it is for oil!  :) Love the exhaust note too btw. Didn't Stallone leave town on the on/off road version in "First Blood"? Of course with 2-stroke sounds dubbed in.  >:(
I read elsewhere regarding your RD top end woes - sorry to hear about that. Other than the oil line mishap what do you think caused the prior siezed pistons?

Well the very first time im not sure, i bought it with a RH piston slappy noise. I took the jugs to an automotive shop and had them bore it, then got some wiseco pistons. I put it together and its slappy right out of the box, i take the jugs back and they say that 'it looks like you ran it out of oil'. Oil injectors work fine, pump is fine, oil is fine, wtf right. The ports were hardly chamfered, the shiny spots from bedded rings were uneven, and it had looked like it was honed with a rock on a stick. The shop wouldnt own up to anything so that put me up a creek, bad experience i suppose.  So back together it goes and off i ride into the distance piston slapping all the way. The new top end was already knackered when i had, legitimately, this time ran it out of oil. Real hard right hand turn (scraping peggage) and the oil light flashes on for a second, seconds later, pherp, seized. Starts back up again alright and off i go to find another set of pistons, slapping even worse off into the sunset.

The second top end, i had boxed up the cylinders and sent them off to scott clough racing (guy who does just two stroke work, lots of performance stuff). He shortly emailed me back and told me to check the rods and see if they're bent, which they werent, because the cylinder bores are friggen crooked. About .004 off to the right each one. I was also told the hone job was atrocious, the ports were camfered totally wrong, and it was a wonder it lasted as long as it did. So, he does em up right and i end up with pro-x pistons.

It ran like a damn champ up until it recently took a crap again, not a single weird noise, nothin. Purring along like a psychotic sewing machine. Awesome gas mileage and great power (mutually exclusive of course). I'm debating whether to spring for some go-fast parts or not. The impulsive side of me wants to put fiber reeds in it, get a mild porting done, mill the head a couple thousandths, and sell a kidney for some nice chambers. The thinking side of me says all that go fast means jack if i've got pogo sticks for suspension and a thousand other projects to get to.

PS The tt's exhaust note is due mostly to having a supercrapp header, mid pipe, and a supercrapp silencer off of a 750 vulcan (way, WAY too big for the application but it acts like a giant resonator).