Technical 500 vs. 650 muffler

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Technical 500 vs. 650 muffler

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Will the 500 stock muffler fit a 650 engine? I see the retailers sell them as separate part numbers, which leads me to believe they aren't interchangeable. Has anyone tried?

If I have to buy a 126 muffler, is there any reason to get a 'sport' muffler other than it is louder? Will it eek out another 1/5th horsepower? :)

Anyone have recommendations on mufflers? Fit, sound, performance, longevity?
 
I have the twin exhaust which I'm told adds another 2bhp. Doesn't sound much but when you're only working with 13bhp to begin with, I'll take it.

Tim
 
The exhausts are slightly different---stick to the correct one for the model. When you do fit the exhaust, if you have the sump off I would recommend you carry out the small Abarth mod (which we did at Radbourne Racing). Remove the 2 top exhaust bracket mounting studs in the crank-case, tap them all the way through, screw in a machine screw FROM THE INSIDE--with a flat washer, lock washer, loc-tite and do them up VERY tight. This takes the load off the stud thread. Use a PLAIN nut and a PLAIN lock-nut to secure the top of the exhaust mounting brackets---do NOT use any form of locking-nuts because when you tighten them down on to the screw they can 'catch' on the screw and actually back it off and loosen it.
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So, the stock 500 muffler does fit. I see the difference now, though. The tube ID of the 500 muffler and the 500 exhaust elbow castings are smaller than those of the 650 motor. I have it mounted but will end up buying a proper 126 muffler anyway. No sense choking the exhaust down just to reuse this old muffler.

Another problem I see is the heater vent tube is so close to the exhaust pipe I can't get the rubber hose on it! I assume the proper 126 muffler has some clearance there.

Mark P.
 
Under 'nothing is easy', I ordered a twin-pipe 650 exhaust and it showed up last night on my doorstep. Installing it went well until I bolted up the exhaust flanges and noticed the #1 pipe was hitting hard up against the engine bay's tray that mounts the heat shield. It also sits pretty far off of the 500 brackets I kept from the old engine.

So, the muffler doesn't fit the ENGINE or the CAR. The seller says this is common and I need to modify the engine bay and get 500R brackets. Do the 500R brackets move the muffler away from the engine this far? He also suggested alternative muffler designs which avoid the tray by both pipes entering the back side of the muffler, but I would still need the 500R brackets. This looks like the distributor would be very close to the pipe, and they would be unequal length (for whatever that matters.)

Anyone with a 500 running the 650 engine out there? Can you tell me how you solved this? What muffler do you have, what brackets? Pictures would help!
 

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Hi Marcus, I have exactly the same problem as yourself, I have a 71, 500L with a 650cc 126 engine fitted. It had a sports exhaust on it from when I bought it 20 months ago, it was very loud and after a run of 5 miles or so there would be a loud backfire on switch off, (hence her name Poppy). While on a run at our Christmas party rally last weekend, one POP was louder than usual and No. 1 pipe fractured. I was given a spare 500 engine with the car so yesterday I fitted the exhaust from that to the car, although it fit OK it is now deafeningly quiet and I haven't tried a run out in it yet to see if it has affected performance adversely. I think once our last rally is over next weekend I will be looking for another sports exhaust and after your experiences I will try and buy one complete with brackets, or take further advice before buying. I am now worried in case she loses her POP and I have to re-name her. I would be grateful if you could keep us updated on your experiences, Eric
 
Will the 500 stock muffler fit a 650 engine? I see the retailers sell them as separate part numbers, which leads me to believe they aren't interchangeable. Has anyone tried?

If I have to buy a 126 muffler, is there any reason to get a 'sport' muffler other than it is louder? Will it eek out another 1/5th horsepower? :)

Anyone have recommendations on mufflers? Fit, sound, performance, longevity?

Hi Marcus

Here's the set up that went into my 1972 500L. Needed to make slight adjustments to the heater duct routing to make it fit without fouling but apart from that it went right in no problem. The exhaust does have a crisper note to it and it is louder, but that is fine with me. It looks just right. As I mentioned in an earlier post there has been some thumping when driving over rough roads that I narrowed down to the exhaust bumping the heat shield A little bit of manipulation to the shield sorted that out. Hope you get the system squared away to you taste.

Cheers
Hugh Jarce
 

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  • 594cc with syncro box and 126 sports exhaust.pdf
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Hi Marcus;
You need to match the exhaust brackets with the engine/exhaust assembly---e.g. 500 brackets on a 500 engine, 126 brackets on a 126 engine/exhaust assembly. It is normal for some 'adjusting' of the engine bay side-deck so that it clears the exhaust. if you can 'tweak' a heat shield to fit, so much the better as it does reduce the heat coming up to the distributor.
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