Do I need a balence pipe ?

[Grewth]

I've just bought a complete (used) genuine exhaust system from a 650 Special.
It's in amazingly good condition considering that it's probably over 40 years old, the chrome is presentable, and the cans don't rattle when you shake them.
The only "fault" is that the balence pipe has been cut off, and each stub has been crushed flat in a vise, and then welded.
Probably done me a big favour TBH.
I'm just wondering if this mod has shaved ANYTHING from the performance ?
I mean if I fabricated a new balence pipe and welded it in, would I actually gain anything except maybe a slight reduction in noise ?
And some extra weight and complication
Would torque or fuel economy be improved at all ?
I'm just curious

 

[nj1639]

As long as those welds are good you should be ahead of the game.
One carb, one cylinder and one exhaust per side sure helps in tuning and troubleshooting.

 

[Grewth]

Not pretty but effective.
I think I'd have cut 'em off square and welded on a capping plate, but obviously this was quicker and less effort

 

[Raymond]

The conversion might not be pretty but it's out of sight?

On my Kawasaki W800, I replaced the original exhaust system with Motad stainless. Big K in their wisdom had the headers, balance pipe and silencers all welded up as one awkward fabrication. Thankfully, the Motad doesn't have a balance pipe.

Not only have not missed it, there's no noticeable difference in performance but taking off separate sides is loads easier than struggling with the joined-up original.

 

[xjwmx]

The purpose is probably to give an effectively more open exhaust since each cyl uses both mufflers. But I've noticed you can have some pretty severe problems (or changes) going on with XS650s and sensorially not notice much of a change...

 

[Max Midnight]

Have a read of this which gives all sorts of information about how the deighn of the exhaust cam impact on the engines characteristics. NB there are also other articles that tell you stuff you didn't know you needed to know!
Whilst it doesn't specifically mention balance pipes what I do take from it is that any change in cross sectional area will have an effect on engine characteristics influenced by the exhaust.
Given the low state of tune any differences whether they be positive or negative are unlikely to effect the running of the motor significantly and IMO unlikely to affect performance to any great degree.

 

[Jim]

These bikes were built to a (low) price point... that was done by questionable quality in some areas.
The crossover tube costs in engineering dollars and more importantly... in production dollars (yen?).
Rest assured Yamaha wouldn't have added the crossover (and cost) if the gains weren't worth the extra production costs.
The crossover helped with midrange "grunt." It was slight, but the bean counters deemed it good enough to justify.

That said... no, you didn't lose much.

 

[Grewth]

Thanks for all the above guys !
When I'm rested and my head is clear, I attempt to mentally digest all that stuff from EPI.
TBH I only bought the complete system to get a decent set of double skinned Special type header pipes, I was really expecting the cans to be on the "crusty" side.
As in sufficiently rotted as to eject their innards once pressed into service.
They ain't, they're actually really solid, as if they've only been used for a short time.
So, having aquired a solid original factory set up, I'm tempted to restore the balence pipe just to see what difference it makes.
Of course joining the two halves together with a traditional split/push over joint would be a total PITA to align properly.
So I was thinking of maybe a short length of silicone turbo hose.
Would that cope OK with the temparature ?

 

[fredintoon]

I've just bought a complete (used) genuine exhaust system from a 650 Special.
It's in amazingly good condition considering that it's probably over 40 years old, the chrome is presentable, and the cans don't rattle when you shake them.
The only "fault" is that the balence pipe has been cut off, and each stub has been crushed flat in a vise, and then welded.
Probably done me a big favour TBH.
I'm just wondering if this mod has shaved ANYTHING from the performance ?
I mean if I fabricated a new balence pipe and welded it in, would I actually gain anything except maybe a slight reduction in noise ?
And some extra weight and complication
Would torque or fuel economy be improved at all ?
I'm just curious

Hi Grewth,
the XS650 stock exhaust is kinda strangulated and the balance pipe lets each cylinder use both muffler systems for better exhaust gas flow.
Removing the balance pipe stops that from happening so that each cylinder can only use one exhaust system instead of both.
I reckon you'll never notice any noise or performance difference with or without the balance pipe when riding normally.
If you want your XS650 to sound like a bike instead of a lawnmower, try shoving a length of rebar up each muffler and pounding
on it with a BFH to pop the interior pipe cap off.

 

[toglhot]

Balance pipes can help in the performance, similar to two into ones, porting, single carb conversions, longer inlet tracts, velocity stacks and so on, but so slight so as not to be noticeable by themselves. Put these minor mods all together and you may notice a difference. The biggest difference they make is the noise, the intake rush, change in exhaust note and so on give you a feeling of better performance, but really, only a dyno could tell you the real story.

 

[Grewth]

Hi Grewth,
the XS650 stock exhaust is kinda strangulated and the balance pipe lets each cylinder use both muffler systems for better exhaust gas flow.
Removing the balance pipe stops that from happening so that each cylinder can only use one exhaust system instead of both.
I reckon you'll never notice any noise or performance difference with or without the balance pipe when riding normally.
If you want your XS650 to sound like a bike instead of a lawnmower, try shoving a length of rebar up each muffler and pounding
on it with a BFH to pop the interior pipe cap off.

I only really bought the things in the expectation that I'd have to junk the rotted out standard cans, and clamp modern silencers onto the headers.
Actually having the factory system intact (well almost) is something of a novelty, as I've never owned such a thing before.
I can remember buying a XS650E back in 1987, and the original silencers were just a bag of rust, the ends blew off as soon as I started it.
If I want loud I've got a replica system bought from Halco Tuning about 17 years ago.
I believe that Tony Hall had them made specially by Brituro exhausts, Birmingham.
You got correct (650 Special) type headers (single skin) and replica silencers which had a glass pack absorption tube inside, like a Norton peashooter.
I'd buy another set tomorrow if I could, but alas, Tony Hall has passed, and while Brituro are still trading, I think their factory closed a while back.
They don't sell XS650 pipes any more, just systems for British bikes, which I suspect are actually made in the far east.