"Big Bore" Norton Commando mufflers

[arcticxs]

Hi all!
I just bought a stock 1977 XS, and found it way too quiet for my taste. So I went ahead and ordered a set of Norton Commando "Big Bore Peashooters" for 1 1/2" headers. These Mufflers have a louvered "straight through" baffle packed with either steel wool or mineral wool of some kind. I have also ordered new single wall headers with OD 1 1/2" (38mm) and ID 1 3/8" (35mm).

I just wonder if anyone has any experience with this, or similar setup, any jetting recommendeations etc for OEM CV carbs.

I may also replace the OEM airbox with K&Ns or MIke`s replica filters. Any recommendations/comments on this as well?

Finally, I wonder if anyone has tried K&N`s "Drycharger" filter wraps? These are supposed to keep rainwater from entering the K&N filters, which can be a problem at times, at least I`ve seen that on my -75 RD 350.

[grizld1]

The Drycharger and Snowcharger wraps are very effective, but K&N makes them for limited applications. What's worked for me is to get the wrap for a filter that's closest in size to what I'm using, then resize it by taking a tuck in the fabric and holding the tuck with a seam of weatherstrip adhesive. For tuning procedures with altered exhaust and intake, see the Carb Guide. Re. filters, the XS Performance items have a good filter medium, but the rubber in the mounting flanges is very poor stuff; IMO the extra cost of K&N's is money well spent.

[thebeaver]

Jun 8, 2010 12:52:45 GMT -5 arcticxs said:

Hi all!
I just bought a stock 1977 XS, and found it way too quiet for my taste. So I went ahead and ordered a set of Norton Commando "Big Bore Peashooters" for 1 1/2" headers. These Mufflers have a louvered "straight through" baffle packed with either steel wool or mineral wool of some kind. I have also ordered new single wall headers with OD 1 1/2" (38mm) and ID 1 3/8" (35mm).

I just wonder if anyone has any experience with this, or similar setup, any jetting recommendeations etc for OEM CV carbs.

I may also replace the OEM airbox with K&Ns or MIke`s replica filters. Any recommendations/comments on this as well?

Finally, I wonder if anyone has tried K&N`s "Drycharger" filter wraps? These are supposed to keep rainwater from entering the K&N filters, which can be a problem at times, at least I`ve seen that on my -75 RD 350.

So, another RD guy. I rode those bikes for almost 20 years before I got old and switched to the XS. It's been a good transition.
It sounds like you are putting together a sweet bike. I ride a '78 Std. Those Norton mufs sound like they will be perfect. I was looking for a set of those, but all the ones I found were very pricey (I should have just sucked it up). Instead I ordered a pair off e-bay that turned out to be cheep Emgo crap with internal baffles (quieter than my stock muffs). I am now building my own straight through glass pack pea shooters.
I ordered the 1-1/2 sigle wall headers from 650 Central (Mac brand I think). They didn't fit well at all. They are made for the later sight glass clutch cover models, and I had to do some tube bending to make 'em fit. I am running the Mike's filters, and they work great. I can't remember the jetting. I have moved twice since I re-jetted last, and I can't find my records. I think we have different carbs anyway. I have Mike's 750 kit and a Boyer ignition which also require more fuel.

[Burns]

I bought a set of straight-through pea-shooters and they look great (seams ground flat before plating) but they are for 1 3/8 OD head pipes.

I've always wanted a BSA bend in my pipes anyway, so I'm thinking of having some 1 3/8 o.d. stainless pipe bent to mount to the peashooters, with a little kick up in the rear so they will clear the rear axel bolt (which the big-mouth dunstill copies that are on it now do not).

Any thoughts? I don't think it will change the I.D. from stock much at all. And the Norton used pipes that size to flow 100 to 200 more cc's of motor.

[tomterrific]

I'm attempting to put a set of Norton Commando Peashooters on my '77 right now. These are for 1 3/8" OD. Norton pipes. I found the outside, OD. of the Peashooters to be appoximately the same as the '77 pipe, or 1 1/2".
I liked the slight added length so I used a 1 1/2" ID. connector between the pipe and muffler, slipped over both as a sleeve while the muffler and pipe are butted together. This sounds great but the pipe OD. is about 1mm larger than 1 1/2". I am using a non powered tool to expand the connector and fit over the pipe with mixed results. Take the pipe and the muffler to an independent real muffler shop and these guys will fit it up fast. A little bit of stainless pipe would be cake.

There is another deal also that I think will be the best. I've used a car muffler clamp about 2 to 3" wide that is to connect two pipes butted together. These use a thin stainless band and two bolts to draw the band very tight around the joint. I'm looking for 1 1/2" .

The mount for the muffler might be problematic. I was able to get one bolt through the stock mount and into the Peashooter but I'd like something that didn't look so half done.

One Peashooter is on but I'm not real happy with the half a$$ed mounting. I'd like to find a real solution. The one Peashooter sounds great. Quiet idle, really speaks up when the throttle is cracked but not too loud.

Tom Graham

[tomterrific]

Hi art,

You can knock the end plate off the center tube inside the stock '77 mufflers and it sounds great. They are straight through and flow well but the sound is deep rather than loud. The previous owner did mine and it appears he used a 1/2" pipe as a punch to hammer the plate off the end of the center tube. The stock mufflers sound so good this way I didn't give any real thought about replacing the mufflers until the right one rusted in half. Many comments on how good it sounded and I thought they were pure stock for the longest time.

Tom Graham

[5twins]

Arcticxs, I just happen to be running a set of '77 carbs at the moment while I'm cleaning my originals and I have mods very similar to the ones you're contemplating. I have MAC headpipes with the same dimensions as yours and the Mikes Commando mufflers. I recently changed from K&N to Uni pods and am liking them so far. If anything, they may flow even better than the K&Ns. My current jetting is 130 mains, 27.5 pilots and the needle is lowered (leaned) one step to clip position #2 (from the top).

I haven't tried mains larger than the 130s yet but I don't think the bike will take much more. This is due to the rich midrange on the '77 carb set. The Z-8 needle jet is the largest ever put in a 650. I highly doubt this carb set will take mains in the lower 140s as recommended by some places. As a comparison, my original '78 carbs run a 3 step leaner Z-2 needle jet and I can just barely run 140 mains in those.

[Burns]

Hey TT, I don't think you'll have any luck finding those wide clamps for a 1.5" o.d. pipe. I was going to go that route but could not find one that small. Went to several shops and exhausted my web searching skills with no luck.