Exhaust pipes for 74 Commando== Any Suggestions???

Hello another question--I have a 74 850 commando that I would like to put new pipes on. What is the best brand of pipes to use and where do I get them. Should I get them with the crossover or not. I have heard the crossover can improve the horsepower a touch and that it helps to keep the pipes from vibrating off and damaging the exhaust threads in the heads. I want good flanges with he3avier metal than the cheapie knockoffs. Should I use 1-1/2 or 1-3/8 inch pipes??? I have heard that the MKIII pipes that use the split inserts and conical do not allow the exhaust nut to catch as much thread as the crush washer flange type??? I want it loud and proud and I intend to use strait thru pipes on it. I want good chrome and do not mind paying for it. Does anyone have any pros or cons??? Thanks for any suggestions.

From what i've heard the crossover pipes are more trouble than they're worth. They were only introduced as a sound control measure so you don't really get a performance benefit, but a lot of the crossovers don't fit quite right which can then cause them to crack the pipes at the flanges.
As for brands, I can vouch for Wassell pipes. Good chrome and look beautiful, especially their smooth peashooters, but mine seem to discolor pretty easily. Could just be i haven't completely sorted out my carbs yet though... :? If you have some real estate to sell, you could use the money to buy some Viking pipes which are supposedly top of the line.
FYI, if you do decide to get 1.5" pipes you won't be able to use MKIII exhaust nuts though. Their flanges are thinner so between that and the reduced number of threads on those nuts, the pipes won't even touch the squash gasket when tightened as far as they'll go. Plus since the pipes are bigger the collets will no longer fit between them and the nuts, meaning you need to use lockrings instead and pretty much voiding the only benefit you get from those style nuts.

Mark Cigainero said:

I have heard that the MKIII pipes that use the split inserts and conical do not allow the exhaust nut to catch as much thread as the crush washer flange type???

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If that is actually true, then the difference I think, would be minimal, judging by how far my own Mk3 exhaust nuts screw in?

Scheffy.G said:

if you do decide to get 1.5" pipes you won't be able to use MKIII exhaust nuts though.

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All 850 (Mk 1, 2, & 3) exhaust nuts are the same, as far as I am aware (part 063988)?

I think a small gain in performance can be realized with a X-over pipe, owing to its exhaust scavenging feature. My 1977 XLCR had a "siamese" exhaust that reportedly scavenged a 1-2 hp gain. And you can buy "fancy" X-overs for Corvette exhaust systems that are reportedly good for a marginal increase in hp.

Having said all that, I don't have a X-over on my MK3, but given the chance, I'd give one a try.

Jason

Scheffy I'm Confused??

Hey scheffy. Would you mind if I called you to ask a few questions??? Thanks but Where do I get the wassel pipes from here in Texas and how much??? Are they non crossover?? What diameter are they?? Why do you seem to suggest that I use MKIII nuts on my 74 MKII and what is the difference between the MKII & MKIII exhaust nuts??

I had the stock cross over system on my MKIII with Dunstall Decibel silencers. I couldn't stand to look at the rusty cross over and ugly Dunstall silencers so I went with a standard, stainless Pea Shooter set up from Epco. I can't report on performance since the bike is in pieces but I certainly will when the bike is back together and running in a couple of months. What I wouldn't give for a time machine or at least a fast forward button.

You're right LAB, my mistake. I meant the 850 style nuts when I said the MKIII nuts. All 850 nuts are the same. Good comparison of the two: http://www.oldbritts.com/16_063988.html. So Mark, you probably already have the 850 style - no difference between MKII and MKIII nuts. Sorry for the confusion. I just needed the 750 style because there’s not enough thread on the 850s to seat the pipe flange against the exhaust gasket on my pipes.
You can get Wassells in either 1 3/8” or 1 ½” non-crossover. Commando Specialties has both systems. Located in the northeast I think but they’ll ship anywhere.

I have the Wassells myself, and like them reasonably well.

They do not have a crossover, and I use 750-style exhaust nuts (longer thread depth) with them - had to, as the OEM collets wouldn't fit the Wassell head pipes.

Put anti-seize on them and torque to ~65 lbs-feet, then retighten to the same torque spec, hot, after the first few runs, and occasionally thereafter. No worries.

Just line 'em up when installing so your kickstarter doesn't hit the right one. Left to their own devices, they may conflict, but if you hold them in place while tightening bolts, you can fix it so they stay out of the way.

That last bit about holding them in place while tightening is something the typical installer doesn't think of 'till immediately after the first kick-start attempt!

Yup, that's when I learned that particular piece of wisdom, Paul. This is one of those "don't ask me how I know" tips!

I use RGM supplied 11/2" bore front pipes with matching peashooter silencers on both my 850 and 750 Combat. They work well and look good and durable. Do not use balanced down pipes as more trouble than they are worth and whatever you are told they were only fitted to reduce levels for noise testing. On my 850 I have a single 34mm carb kit and is without doubt the best mod with the exhausts I have ever done on any of my Commandos