Passing Gear?

[IanDMacDonald]

Okay, okay. I'll go-out late tonight, or early tomorrow morning and post my bike doing 70 mph. I cannot recall what rpm it is @ 70 mph. I do know that around 5k it is close to 80 mph, give or take a mile or two. I've noticed that the tune of the carbs directly affect that speed range. U say it doesn't? I disagree. Running the carbs with a 137.5 main jet, and richer, I was @ 5200 rpm for 80 mph. Now, back to a 140 Main, I don't think I have to push the bike that hard.

Btw, no helmet Todd? Loo, jk.

[motoman]

Okay, okay. I'll go-out late tonight, or early tomorrow morning and post my bike doing 70 mph. I cannot recall what rpm it is @ 70 mph. I do know that around 5k it is close to 80 mph, give or take a mile or two. I've noticed that the tune of the carbs directly affect that speed range. U say it doesn't? I disagree. Running the carbs with a 137.5 main jet, and richer, I was @ 5200 rpm for 80 mph. Now, back to a 140 Main, I don't think I have to push the bike that hard.

Btw, no helmet Todd? Loo, jk.

My in fiftg gear Venturer isspot-on 5 K at 80mph.......and yes Ian main jetting WILL affect top speed in in a particular gear........it's called carb bell velocity........more fuel it takes more air also.

[trbig]

I can see having more power, but "X" rpm with everything directly driven and in gear, with whatever jetting you have, should equal the same. Equal rpm, no matter what you've done with the carbs should equal same speeds?

No helmet... Meh.I know there's a risk, but while I still have hair, sometimes it's nice to feel the wind in it on the way to work.

[motoman]

I can see having more power, but "X" rpm with everything directly driven and in gear, with whatever jetting you have, should equal the same. Equal rpm, no matter what you've done with the carbs should equal same speeds?

No helmet... Meh.I know there's a risk, but while I still have hair, sometimes it's nice to feel the wind in it on the way to work.

Unfortunately not true Tod. Increased carb bell velocity increases air flow which draws more fuel up thru straw tubes. If carbs have the increased main jetting which pulls the lsrger fuel flow.........to a point of not being overfueled, rpm speed IS increased andmatched with increased fuel induction. Think blowing across topof straw with full fuel flow as opposed to lesser fuel flow, That's how ALL sidedreft carbs work.

[IanDMacDonald]

https://youtu.be/p0o5jOJH_1w

Nothing exciting. The first view of the gauges shows a higher reading, as I did not realize I did not shift into 5th. Looks like 4600/4700 rpm @ 70 mph.

[Roncoach70]

Thank you all I drained out the Mobil 1, adjusted the clutch, put on Auto Zone 20W50 and as usual you guys have me grinning from ear to rear. Thanks, stay tuned I'm sure I will do something stupid in the near future. What a beautiful day for riding in upstate New York today. Stay safe everyone.
Ron

[Bonz]

Just a clarification... RPM at a given road speed in a specific gear is fixed and will not change based on carb tune! There is no "question mark ???" to it!

Put the helmet on, and call the "less than long" bus!

[red bandit]

Just came from a short ride. About 4 years ago I checked my speedometer with GPS. When the speedometer said 65 GPS said 60 and 100 vs 94 respectively. So today, no video because I don't have anything that well take a video. Anyway, when the speedo said 75 (which should be 70) my tach said 3600 in 5th, standard with 750/850 FD, 17" rear wheel. And I can hit 100+ in 3rd. Don't know why I have lower RPM's than most. YMMV.

[motoman]

Thank you all I drained out the Mobil 1, adjusted the clutch, put on Auto Zone 20W50 and as usual you guys have me grinning from ear to rear. Thanks, stay tuned I'm sure I will do something stupid in the near future. What a beautiful day for riding in upstate New York today. Stay safe everyone.
Ron

Good to hear the suggestions worked for ya'.

[trbig]

Unfortunately not true Tod. Increased carb bell velocity increases air flow which draws more fuel up thru straw tubes. If carbs have the increased main jetting which pulls the lsrger fuel flow.........to a point of not being overfueled, rpm speed IS increased andmatched with increased fuel induction. Think blowing across topof straw with full fuel flow as opposed to lesser fuel flow, That's how ALL sidedreft carbs work.

Big straws, little straws,more fuel, less fuel, shouldn't matter. Everything is connected by chains and gears. You can't turn something in the assembly faster without it affecting the output unless the clutch is slipping. RPM at a given speed can't change, no matter how efficient or inefficient the carbs are doing their job.

Put the helmet on, and call the "less than long" bus!

Ain't it cool we live somewhere we have a choice? I wear one ALMOST all the time.

[Bigfoot]

Just came from a short ride. About 4 years ago I checked my speedometer with GPS. When the speedometer said 65 GPS said 60 and 100 vs 94 respectively. So today, no video because I don't have anything that well take a video. Anyway, when the speedo said 75 (which should be 70) my tach said 3600 in 5th, standard with 750/850 FD, 17" rear wheel. And I can hit 100+ in 3rd. Don't know why I have lower RPM's than most. YMMV.

The reason you have lower RPM's that everyone else is because most people that have done the final drive mod are doing it on a special or xj with a 16" rear wheel.

I am going to go give it a shot on my bike as well even though it seems that some opinions around here cannot be changed even if you prove it over and over. I as well have hit 100 in third, didn't realize there were people out there that didn't think it was possible. Stock final drive on a standard.

[Bonz]

TR, too funny! I was referring to the fact that a fixed gear system can't change rpm based on carburetion(!) and if guys continued to debate that it does, was going to "give them a helmet and put them on the short bus". Purely coincidental about your helmet stuff!

CZ has the FD swap on his 80G, what rpm are you turning at highway speeds, CZ?

[red bandit]

[QUOTE=Bigfoot;472947]The reason you have lower RPM's that everyone else is because most people that have done the final drive mod are doing it on a special or xj with a 16" rear wheel.

Yes I know that but I was talking about other standard's with my set up: standard, 750/850 FD, 17" rear wheel.

I'm not trying to start anything or say anyone is wrong. I am merely saying what mine does/is.

[Bigfoot]

Right, and the numbers being thrown around here are mostly comparing stock Standard with modded special or xj tach readings at specific RPM's. So of course your modded standard with the 17" wheel would not match up to any of them.

[trbig]

Just came from a short ride. About 4 years ago I checked my speedometer with GPS. When the speedometer said 65 GPS said 60 and 100 vs 94 respectively. So today, no video because I don't have anything that well take a video. Anyway, when the speedo said 75 (which should be 70) my tach said 3600 in 5th, standard with 750/850 FD, 17" rear wheel. And I can hit 100+ in 3rd. Don't know why I have lower RPM's than most. YMMV.

With a 400 rpm reduction from a 17" tire, along with an 800 reduction from the final drive, you're right in the ballpark with your numbers.