mufflér exploded

while riding yesterday he started making loud, strange sounds all of a sudden. rode home gingerly. after checking the exhaust valves, pipe nuts, and pipe muffler connections i could find nothing amiss. did a compression check and the loud side is about 5 pounds less than the other. wifey noticed i was perturbed at dinner heh,heh. all thru thanksgiving dinner i was rehearsing pulling the head. about an hour ago i was cleaning up my shop area and dropped a wrench. landed behind the bike and as i was bending over to retrieve it i saw that the loud muffler had that spaceship looking baffle gone. i'm sure it laying in the road somewhere.

so now i either buy a new set or take the buck rogers thingy out of the good muffler. now i'll be running w\léss back pressure and will presumably have to retune thecarbs. aNy of you guys run decibels w\o the internals. how's it working. thanx,rick

Im running straight through reverse cones (no baffle) with single 34 mikuni, 27.5 inter 240 main jets (will drop main to 230)
Runs great and sounds even better, especally when your on the gas> :mrgreen:
JUG

rgrigutis wrote;

spaceship looking baffle gone

Click to expand...

In my experience, any baffle will stifle the power you get from a Commando. If you can't see right through it, you will be sapping power. In the early 1980s I bought some pattern reverse cones, which had an immediate effect of reducing the power available from the motor.

An original type reverse cone should have a circular tube right through that you can see through from one end to the other, but with three rows of cusps arranged in straight lines at 180* towards the end of the silencer, apparently to deflect some of the noise/airflow into the packing that is behind this pipe in the space made by the conical shape........does that make sense?

So if you have baffles, I personally would change them as a pair if you can afford it, but make sure you get the "original" type.

I'm not sure about jetting, but would use the standard settings for your machine as a starting point.

I just thought, if you are talking about a "black cap" type silencer for a MK3 or MK2a, then disregard the above, as they are different to reverse cones and do come with baffles .

tei'se are the dunstall megaphone knockoffs. there's a plate rivetted to the end and inside the muffler, the baffle. this is what came off. i had just installed some jrc carbs and am trying to find the right pilot jet. last swap i was backfiring on decel which was probably what blew the baffle off. reckon i'll remove the baffle out of the good muffler, see how he sounds, and try to tune from there. otherwise it'sa new set anyway. i live on a ridge overlooking the ohio valley. there'steep twisty roads winding thru the deep hollows seeming to amplify sounds and echoing them. wifey said she can always hear me a long way off. even her untrained ear can pick out the norton from the other bikes. should be interesting to see what he sounds like with what'`ll amount to straight pipes

I ran original Dunstalls in the in the 70's for a while. The baffles on 2 sets came loose and rattled badly. When I had my engine hopped up by TC, he put on a set of custom megaphone mufflers. I like the look and sound. Took apart my Dunstalls and used the perforated baffle in the the new megaphones. I still have a section of Dunstall baffle to use again if I ever need it,
http://www.britcycle.com/Products/712Z639.htm
Bill G

ell i wrestled the baffle out of the good one and lit him up. great sounds but the backfire is really, really bad on deceléeration. sputters a couple seconds at wot and then if i back off a tad it REALLY comes on. plug chopped wot and they were gray. mid range is anemic.. seems like the motor is trying to catch up with carb. i like the sound of the open pipes but if i can't lick the backfire and the rest of it i'll have to spring for a new set. have a great weekend, rick

The original peashooters on my 69S had the baffles plus a block right about where the widest part of the muffler was. Got a set of Hookers 2 into 1 and they backfired, less backpressure. Got a set of roadsters silencers without the block and they backfired too. Can't wait to get it back together with the new Wassal peashooters with the baffles but no block and am sure they will backfire too, I think it is just a matter of setting up the carb right. My 930's came with a 240 main jet and the needle in the middle position.

Dave
69S

yeah i just recently mounted 2 new jrc carbs and had them going reasonably well when the muffler went to hell. the guys at jrc can hopefully talk me thru the jetting or at least get me started on the right path. is it possible to run straight pipes w\o backfiring?

I would think so. I have had some tell me that their bikes did not have the block, so they must have been set up correctly for baffled only silencers.

I hope so too.

Dave
69S

i have an old, used set of xtra peashooters that came w/ my 2a project. they were filthy but a scrub w/ kerosine got most of the crap off. they are not the black cap, at least there's no black cap on them now. there's a baffle w/ a dime size hole in it a short way from the end. i know there are several variants of the peashooter. there are no markings at all on these. any way tp positively identify them? i know a pic would be appropriate but wifies got the cam and out of town. meanwhile i'm going to get a couple of larger main jets to see if that helps wot w/ hollowed megaphones. then xperiment w/ clip position for mid throttle sluggishness. w/ cold weather approaching i don't feel bad about him being laid up 'til i can figure it out.

The backfiring on the overrun is usually due to air leaks in the downpipes allowing any unburned fuel to ignite.
I read somewhere that it was the 'Rocker' thing to drill the downpipes with a small hole to achieve the...'er... 'desired' effect!
Triumphs with push-in (& fall-out) downpipes are good at this too... :roll: