Triumphrat

SlowPocono

I have a need for opinions about my exhaust modification. I know I'm going to be laughed at by someone and I want to avoid any "loud pipes" arguments but I really want to avoid creating any problems with my bike. I have been slowly bringing my 1979 T140E out of its' long slumber of more than a decade. My aim is not to restore the bike, just to attain a roadworthy, rideable state. After that hurdle is achieved, an attempt at a mild cafe' modification will be next. The bike is now registered and insured so there have been some shakedown rides. There are over a hundred fifty test miles on the odometer now, all of them within walking home radius.

The bike was acquired with an after market two into one system that's in good enough condition for my purposes and has an appearance that goes along with my plans. The exhaust is predictably loud. Too loud for my goal of not being annoying to other people.

The engine starts easily, idles well and seems to have adequate power at low speeds and moderate throttle openings. With a neutral throttle at road speed I experience a surging sensation that I believe is consistent with a lean mixture. Opening the throttle beyond 75% usually results in some bucking and sputtering but the bike does accelerate and eventually smoothes out. Coasting with a closed throttle results in quite a bit of popping noise from the exhaust. The plugs have a classic dark chocolate color to them but the full throttle performance is definitely improved when the enrichers are activated. I haven't installed my new tires yet so I haven't had the bike over 90mph but the engine seems unwilling to rev much faster. The MKII Amals have 210 mains, #3 cutaway slide and 2C3 needles which, I think, are the standard items. It looks to me like the previous owner didn't rejet for the modified exhaust.

I had been planning a strategy for improving the carburetion and agonizing about the undesired exhaust noise. I wondered if the bike would run better if an original equipment exhaust were fitted. I'm proud that I had the foresight to realize that if I rejetted now I'd have to do it again if I changed the exhaust.

In the old days, I had a number of bikes whose mufflers had baffles that were removable for cleaning. Those baffles never seemed to need cleaning but as an adolescent I needed the performance "improvement" and enhanced sound of running the pipes with the baffles removed. I know what those baffles looked like.

I swear I wasn't drinking when I had the idea of creating and installing a baffle system for my T140E. The first prototype is a bit of cast iron pipe and a cap ground to fit the muffler and drilled for flow.

The road test resulted in a much improved throttle response and sound level. The deceleration popping is gone. I need to do more testing and exhaust "tuning" before concluding that the modification is a success.

After all of this buildup my question is am I at risk of ruining anything by continuing with the testing?

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pookybear

Slow Pocono,

I would work out that lean mixture first as it can lead to a burned
piston or valve. I do not think if you get the bike running on a
slightly fat mixture you could do any damage while trying out your
exhaust work. When finish you can do a final jetting on the
carburators to get it dialed back in right.

Pookybear