Dyno testing of my 501 engined 3 1/2
Posted: 29 Apr 2018 09:50
I've seen discussions of the exhausts, carbs, airboxes, etc. to get 501 engined 3 1/2's to behave. I've owned my 501 engine since it's youth in a 501 New York. NLM fitted it with their S/S 2-2 clone exhausts and standard airbox (with filters) into a 3 1/2 K1 frame about a decade ago and 2 years ago I replaced the exhausts with a tweaked set of the standard Excalibur exhaust system and have ridden it to Italy and back, to Cadwell and back, etc. perhaps 5,000+ miles in it's current guise.
Earlier this week I took it to PDQ in Taplow, Berkshire to check the power output and jetting. We found it ran best with the 120 mains I'd been using. We tried 130's, 125's and 115's. With the larger mains the fuelling was better (closer to the 13:1 the tester reckoned was ideal) but power dropped. With the 115's power was marginally down but he reckoned that was perhaps down to the heat of the bike at the end of the testing runs (of about 85 minutes overall). We settled on the 120's to protect the engine.
Peak torque is at just over 5000 rpm (5,230) at 31.38 ft-lbs
Peak power is at 7000 rpm (7,010) at 35.88 hp
He recommends I fit either a lambda sensor to both downpipes or a 1/8 bsp take off (as used by Aprilla's apparently) in the U bend so he could get a more accurate fuel/air reading (which was a problem throughout the test at the end of the Excalibur exhausts).
BTW the bike does an indicated 170+ kph quite easily and pulls extremely well with few fuelling problems. I seldom see 180 kph, it's maxed out at 170+.
In terms of general riding, It's a bit grumpy off idle. It's very pleasant otherwise, and I use the bike for everything from long distance (250+ mile runs) to commuting into C. London as well as shorter rides. Fuel consumption is in the mid 50's MPG perhaps up to 60+ MPG at times. It cruises very happily (where the law allows, etc) at an indicated 145 kmh. I do have a Givi clear handlebar fairing fitted and ride with Tomaselli adjustable clip-ons.
I hope this helps others. I'll test my 3 1/2 at some point, once I get it back together after it lost the rear head insert and the 2-1 downpipe got mangled.
Earlier this week I took it to PDQ in Taplow, Berkshire to check the power output and jetting. We found it ran best with the 120 mains I'd been using. We tried 130's, 125's and 115's. With the larger mains the fuelling was better (closer to the 13:1 the tester reckoned was ideal) but power dropped. With the 115's power was marginally down but he reckoned that was perhaps down to the heat of the bike at the end of the testing runs (of about 85 minutes overall). We settled on the 120's to protect the engine.
Peak torque is at just over 5000 rpm (5,230) at 31.38 ft-lbs
Peak power is at 7000 rpm (7,010) at 35.88 hp
He recommends I fit either a lambda sensor to both downpipes or a 1/8 bsp take off (as used by Aprilla's apparently) in the U bend so he could get a more accurate fuel/air reading (which was a problem throughout the test at the end of the Excalibur exhausts).
BTW the bike does an indicated 170+ kph quite easily and pulls extremely well with few fuelling problems. I seldom see 180 kph, it's maxed out at 170+.
In terms of general riding, It's a bit grumpy off idle. It's very pleasant otherwise, and I use the bike for everything from long distance (250+ mile runs) to commuting into C. London as well as shorter rides. Fuel consumption is in the mid 50's MPG perhaps up to 60+ MPG at times. It cruises very happily (where the law allows, etc) at an indicated 145 kmh. I do have a Givi clear handlebar fairing fitted and ride with Tomaselli adjustable clip-ons.
I hope this helps others. I'll test my 3 1/2 at some point, once I get it back together after it lost the rear head insert and the 2-1 downpipe got mangled.