SOB broken headers!

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Larry S

Larry S

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Went on the last ride of the season and pulled into a gas station for something to drink. While enjoying my drink I was looking over the bike when I noticed small crack in my right side silencer. Finished my drink and limped home. Near as I can see the footrest rubber failed causing the silencer to break off at the weld which caused my header to break. What a bitch!
 

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The top rubber appears intact so maybe the failed lower rubber isn't the cause but maybe a symptom after one of the other cracks - probably the silencer (IMHO)
I feel for you regardless.
 
When I looked at the pics I noticed how much things have moved once ‘free’.

It looks to me as though things may have been assembled in a way which put them under stress / tension?

Stress / tension combined with vibration is very good at breaking things !
 
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Man that sucks. I've had the same thing happen with the rubbers.
You have to be very careful how you assemble your exhaust, as FE has said, any tension or forced tightening will break it.
 
With balance pipe exhausts you need to modify the silencer mounting brackets. The balance pipes have the kick at the end soley for the black cap silencers, which mount in a slightly different position.
 
Breakage in both areas isn't uncommon, unfortunately.

Peashooter cracked

Hello, I have about a 1k miles on my peashooter, the left side cracked just ahead of the weld. Ive read a few threads about this, one was using silicone at the muffler- pipe joint and a loosely tightened clamp. They are Commando Specialties, Ive contacted them. MK3 with no cross-over pipe...
www.accessnorton.com www.accessnorton.com

Advice on 'Commando' exhaust crack

Hi All: Once again the neophyte asking for help and advice. You've never steered me wrong..... So the exhaust pipe on my '74 Commando has a crack in it along the weld of the balance pipe and across the pipe itself. I'm told this is common. Here's what I think my options are, but there may...
www.accessnorton.com www.accessnorton.com

On a different subject, I would question the need for the washer between the swingarm axle plate and the caliper plate (yellow arrow) especially if there is any trace of a gap where the green arrow is?
SOB broken headers!

There's no washer in the parts book and my Mk3 doesn't have or need a washer at that location as it would put the caliper plate and thus the caliper out of alignment with the disc.
Note that the Mk3 shock eye lower mount sleeve should be wider than the upper (see Mk3 manual section F5, however, the dimension in Fig. F14 is incorrect and should be 0.942") so in my opinion, the washer would probably be better placed between the axle plate and the non-standard shock also the same on the drive side as without additional spacer washers my apparently pre-Mk3 Hagon shocks wouldn't be parallel but would lean away from each other.

06-6489 Norton Commando MK3 Shock Absorbers - HAGON - British Motorcycle Parts Ltd

www.britishmotorcycleparts.co.nz www.britishmotorcycleparts.co.nz
"Note: Although the earlier Commando shocks can be used on MK3 models, the MK3 shocks can not be used on the earlier models as the bottom bush is wider on the MK3 models."

Madnorton said:
With balance pipe exhausts you need to modify the silencer mounting brackets. The balance pipes have the kick at the end soley for the black cap silencers, which mount in a slightly different position.
Click to expand...

Some perhaps are worse than others?
The pic. below shows the RH peashooter with balanced Toga Mk3 pipe set fitted to my Mk3 with the upper and lower AV mount nuts removed and although the weight is supported, the assembly is not being forced into alignment.

SOB broken headers!
 
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What kind of silencer?

Several years ago I bought a set of CS seamless peashooters. after a few hundred miles and then about a thousand miles to the NOCNZ rally, the inlet cuff broke off below the weld at the shoulder of the silencer. Because I was so far away, I wired it up best I could to keep it from falling off.

But since the header was vibrating loose at the end so much, the sidestand bolt wore a hole clean through the new Les Emery header. Which I also got from CS.

When I installed them, I set them all up loose and got them well aligned. At least I thought I had. There was no deformation on the rubbers.

Sigh.

YMMV, etc.

SOB broken headers!
 
L.A.B. Could you please post the part number for a pair of unbalanced headers suitable for a MK3 roadster with peashooters? Thanks.
 
Larry S said:
L.A.B. Could you please post the part number for a pair of unbalanced headers suitable for a MK3 roadster with peashooters? Thanks.
Click to expand...

Technically, there isn't a set of Mk3 unbalanced headers for peashooters as the Mk3 didn't have them, only black caps/bean cans with balanced pipes (apparently needed to prevent a loss of power when black caps are used).
As the unbalanced pipes are usually listed under the same part numbers (06-5256 & 7) and unless the supplier specifically states they are made to be used with peashooters then it would be a question for the supplier to answer.

One benefit of the available unbalanced Mk3 pipes is they allow a (slightly) greater range of adjustment at the cylinder head.
 
What are the benefits or drawbacks of balanced versus unbalanced systems?
 
WEM said:
What are the benefits or drawbacks of balanced versus unbalanced systems?
Click to expand...

It was claimed that the balanced system reduced noise, which, having used both types I'd say the balanced system is slightly quieter.
The balanced system, however, often cracks in the area of the cross pipe.
 
WEM said:
What are the benefits or drawbacks of balanced versus unbalanced systems?
Click to expand...
Reduced power vs. unbalanced.

www.accessnorton.com

Balance pipe and Dyno Hill

Even though I said I wouldn't, just had to give it a try. The pipes were off the MK3 850 for exhaust port repair, so it was easy to turn up some alloy plugs to run with the balance pipe removed. With the plugs in, so simulating regular twin exhaust, I did 4 runs on Dyno hill using the GPS for a...
www.accessnorton.com www.accessnorton.com
 
L.A.B. said:
It was claimed that the balanced system reduced noise, which, having used both types I'd say the balanced system is slightly quieter.
The balanced system, however, often cracks in the area of the cross pipe.
Click to expand...
When I changed my pipes from unbalanced to balanced on my 750 I definitely noticed a difference because I went for a ride with both set ups on the same day
I wanted to take the edge off the pea shooter's
Not sure what noise difference it would make with black caps?
 
My ‘74 Commando had a balanced system. Early in the past riding season the balance pipe cracked. To minimize downtime during the short riding season in this area, I had the cracked balance pipe cut off and the holes in the headers patched creating a makeshift unbalanced system. The bike seemed louder than I recalled it being last year but I wasn’t sure if it was my imagination or not. I don’t mind a loud bike but I don’t want to be a bad neighbour either so I think I’ll restore the balanced system. Thanks to all for the input.
 
I purchased these silencers from AN and since I have so few miles on them, I wonder if they'll send me a free replacement. It looks to me as if it broke on the weld. I'll give them a call and see what my options are.
 

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I'm up for a new set of pea shooters every time I find a set to use you guys post pics of broken mufflers from the guys I'm thinking of buying from. Please help is there anything out there that doesn't break in half.
 
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