Drilling out the Muffler,s for more power and sound?

[XS650D]

We just got another ft off snow and have to much time to think about the bike.I was wondering if anyone has tried this with Mikes Commando pipes.
Drill small 1/8" hole thru the centre all the way thru . I find the Mufflers kind off restrictive
in sound and flow. I know a guy with same bike (77D) with the older Bubs mufflers
installed on the smaller and more restrictive head pipes.I think stock are just over an inch inside dia
than the stock Mikes tipped up at the end manifold pipes are around 1.5". The Bubs Muffs are a lot louder and
and much less restrictive than the Mikes Commandos I have. Our bikes have exact same compression numbers but his definitely has way more power from bottom to top. Are jetting is very similiar and same air intakes.
I cant help thinking that could be the reason his feels more powerful is the Commandos are to restrictive.
Has anyone tried opening them up a little and can advise results. Unfortunately Bubs no longer
makes these pipes. There is another Muff that Mikes sells the XS Performance reverse cone Megaphone
mufflers. I saw a guy last year with thease and they have much more bark than the Commandos,not sure about performance though.

 

[MaxPete]

Hi XS650D:

There are SO many variables that determine the power output of an engine - and so few of them are related to the restrictiveness of the mufflers - that unless you have a dynamometer and a lot of instrumentation, I very much doubt you could tell the difference between Mike’s and any other mufflers.

I suspect that in the process of making them louder, what you’ll mainly do is cause them to rust out faster.

 

[650Skull]

to many variables when comparing 2 of the same bikes............Carb set up, (jets, airbox/pods/uni foam filters), ignition system, coils, timing, gearing, all of these things or just one difference could make a big difference to the running.

The experts here have said and will say no 2 XS650 bikes run the same. Even when doing the jetting the 2 bikes may have to have different settings. The heads on these bikes were cast and the ports vary a hell of a lot due to casting flaws disturbing the flow of the inlet and exhaust, when people have done porting jobs some bikes have had to have the port built up to get the optimum flow and others just need to be cleaned up.

 

[650Skull]

PamcoPete posted an exercise he done on his bike to see if the different set ups with his pamco ignition and different coils would affect the efficency, (MPG), of the bike.

He done several runs over the same distance, same speed ,time of the day and same conditions, bla, bla, bla, trying to keep all the run conditions as close to the same on every one. Due to the different set ups the fuel economy went way up, (he actually went up a size on a jet after the second run), from something like 55mpg to over 60mpg, (cant remember the exact figures), due to just getting a better spark and an efficient fuel combustion. Looking at the test from a different angle and working to a mpg situation then he would have done the course a lot faster, as the bike fuel efficiency went up, if he tried keep the bike running at 55mpg on every run

 

[XS650D]

OK, anyone know a really good xs650 tuner in Ontario that knows how to machine the heads
for optimum power. can any shop handle this or do u need to be an xs650 Guru!
There is a download available on the net for $39 (from 1973 Yamaha race dept) that supposed to have
all the Mods and tuning info they learned back in the day for race and street application.
Anyone bite on that?

 

[XS650D]

Apparently, 650 central has all this info learned back in the day when they raced these 650,s and were getting
a reliable 70 hp out of them. The head design was a big part of that. I like the idea and I think the guy
is pretty knowledgable but im not sending the heads to California from Ontario ,Canada.
Last time I got shocks from them my bill ended up $300 more for Duty, Shipping,Taxes,Brokerage and exchange rate!!!
Ended up costing me over $500 CDN for 2 Progressive gas shocks. Sorry had to Rant. gotta keep
the jobs close to home now. Thank the lord for xs650 Direct (2 hrs away)

 

[650Skull]

Don't grab hold of an idea among a dozen given and run with it thinking it will be the solution..........
Head work on these bikes is contentious at the least. Forget local mechanics or machine shops unless they are old timers who work on these classic bikes for a living. Even then they may be experts on some models/makes and not others.

All and any information regarding these bikes is on here somewhere, (try Tech Menu/Search feature), and as your doing ask questions in conjunction with search's.

I'm not being specific, but not on purpose to discourage, but to help you. The knowledge and help given here is second to none, guys have come on here with no knowledge of bikes and have rebuilt engines and every mechanical and electrical part of the bike....................

Scroll down to the PDF download, and download.................this may answer a few questions regarding an exhaust for the XS650...........then again it will probably make you ask a few more questions as it should.........
http://www.650performance.com/

 

[650Skull]

If your after quality shocks look for a Canadian distributor for Ikon shokkies...........these guys bought the rights to Koni shocks after they went ou of production and any old rebuild-able Koni shocks can be rebuilt with the Ikon shocks................same parts just a different Company name

Scroll down to International distrubutors
http://www.ikonsuspension.com/

 

[5twins]

Maybe you could get your buddy to let you try his BUB mufflers on your bike? That should tell you if they're the thing making the difference.

The Commando mufflers come with a hole straight through the center of all the baffles, and an Allen bolt to plug it. I, of course, tried mine 1st without the bolt, then with. They weren't much louder without it but the tone was kinda raspy. I didn't care for it as much as with the bolt in. I really couldn't tell any difference in performance.

 

[XS650D]

I will be doing just that 5T if he will agree to it! He is using the the original Manifold pipes that came with the bike
which are pretty small Dia. He stated that the biggest difference he noticed from the stock bike was after
adding the Bub Mufflers and installing much stronger coils. ( He has points, NO electronic ignition) He did have to adjust the
jetting richer.The air muffs didn't make any diff,i ran his bike with and without any air filters at all and it ran the same Strangely ,he was probably over jetted anyway as when I pulled his plug to comp test they were black!
I have ridden many xs650,s over the years including the 2 I have owned all years 77 thru 80. Some completely unmodified and some lightly modified and His runs Dramatically better in power
and smoothness over the others, not even the same feeling bike.Maybe he got a good one! The crazy thing is his is a total
rust bucket, all original (purchased new by him). He,s had 4 brand new xs650,s over the years from early 70,s to late specials and
he stated that the 77 was definitely the best by far in smoothness and power (why he kept that one only) But I keep coming back to the changes he made that HE STATED
made a whooping diff.If u have read the old article printed by Joe Minton "Building a better twin". I know most here have read it but it clearly states
that adding the Bub Muffs and 1.5" head pipes gave an increase of 26% at 4000 rpm while also smoothing out the engine
to a "totally stock bike" tested by Jerry Branches facility ( XS GURU AT THE TIME).He did state that the pipes made the biggest diff but
the Coils,wires Iridium plugs all helped a lot. I laughed when he told me while I looked at the bike then I cracked the throttle while
standing beside the bike and u could feel the responsiveness and power, kinda got me thinking but still not expecting much when he offered
to let me ride it, Wow.Dident want my nice polished award winning bike back. First thing he said when he got off mine was that his was a lot
more powerful and smoother, that hurt,havent been rite since LOL!

 

[weaselbeak]

650 Central is a guru on our bikes. There is almost nothing he doesn't know, and he's honest. I don't know Hugh, from HHB, but he's built some nasty sprinters. My son put a big bore kit on his, and the difference was pretty impressive. There are lots of ways to go. Results will vary.

 

[XS650D]

I also was wondering about the length of my Header pipes (Mikes) with tipped up ends being 35" in Length.
They also sell a much shorter head pipe with the Commando Muffler ,length 26" . I have been reading up
on head pipe length and it will make more of a difference than the Mufflers if not the correct length for the motor
application. Based on the Minton article the optimum length is 32 or 33 inches. I am going to cut of 3" of my pipes
and see if any difference. Mikes tipped up end manifold pipes I have to insert all the way to the bend in the pipe
to fit the hanger bracket I have.There is probably 5 or 6 inches inside the Muffler.I think thats way to much and could affect
the tune. How much head pipe do u feel I need "minimum" to get the pipe to clamp to the muffler safely?