[cyrusb]

Has anyone tached out their classic at 60 mph (indicated) ? Looking for a ballpark figure, stock (17t) sprocket. Thanks.

[fredgold52]

I wanted to bump this back up - I'm interested in knowing what RPM's we are turning at various speeds too.  I know this is sort of a lazy engine and that's one of the reasons I like it so well.  But still, RPM's would be nice to know.

[cyrusb]

I cant believe no ones done it yet! I guess I'll have to dig up an old dwell meter or the like. Haven't seen any of those old tuneup tools in 20 years. I'm going to take a guess at 3800 and hope I'm wrong.

[Foggy_Auggie]

Transmission ratio in 5th gear.

Sprocket ratio = rear sprocket / front sprocket

Engine rotation / km = trans ratio * sprocket ratio * wheel rotation / km

Engine rpm = engine rotation / km * bike speed / 60

One mile = 1.609 km

Wheel rotation travel found by using a string to measure the distance traveled in one rear tire rotation.  Can be performed on the center stand with a helper.  Measure in inches - convert to millimeters - convert to three decimal points of meters.
(example only:  wheel travels 65.25 inches in one rotation - this equals 1658 mm = 1.658 meters).

[baird4444]

                                       FOUND IT!
Below is a post from "DWM" Dave was the builder of Hanuman in the members
rides. What he didn't know he figured out and shared.   - Mike
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I wanted to know my RPMs at different speeds, so got this little tach;
http://www.tinytach.com/tinytach/gasoline.php
Not bad for $37 US, being digital, it's useless for shifting. but, if you need
a
tach to shift a
RE, you're stone deaf, and yer butt has gone to sleep. Also has a 2 second lag.

Anyway, here are speeds/RPMs, with a 19T countershaft sprocket on the five
speed.
(XT- extrapolated.interpolated)

50MPH-2870 RPM
55MPH XT - 3146 RPM
60 MPH - 3450 RPM
65 MPH XT- -3737 RPM
70 MPH - 4025 RPM
75MPH XT - 4312 RPM
80MPH - 4600 RPM
85MPH XT- 4887 RPM
Theoretical;
90 MPH XT - 5175 RPM
MAX RPM-5500 - 95MPH

The speeds above are from a GPS corrected speedo, and I think they're pretty
tight
numbers.
I don't think the bike would do 95 MPH if you pushed it off the Sinny Arbor
Bridge, but it
touches 85 with my 220 lb on board, so I think a lighter rider would see 90.
(535cc, 8.5:1. 34mm Mikuni, short Brit exhaust, K&N)
More importantly, it means my "75 MPH all day, 80 to pass only," are usable
limits. I just
can't see that motor objecting to 4300 RPM. It sure sounds relaxed.
Below are extrapolated numbers for 19 and 18 tooth sprockets;
18T (19/18ths of above RPM)
50MPH-3029 RPM
60MPH-3642 RPM
70MPH-4249 RPM
80MPH-4855 RPM

17T (stock, 19/17ths of 19T readings)
50MPH-3207 RPM
60MPH-3855 RPM
70MPH-4498 RPM
80MPH-5141 RPM

BTW, I installed the black bar-end mirrors from CMW on "Lady Triumphantes", the
$15
ones, and they have been fine. Of course, the Trumpet vibrates a bit less.
Best,
DWM

[jdrouin]

Wow! Cyrusb's guess of 3800 rpm on a 17T countershaft sprocket is pretty much dead on, balls accurate.

Jeff

[cyrusb]

Thanks baird444, I printed that out. I had a feeling the revs were in the high 3000's but didn't think my guess was that close!

[Bankerdanny]

dead on, balls accurate?

[luoma]

Appreciate the info. My bike has a 19-tooth also. It feels pretty tight at 75, but I guess it's not.

[jdrouin]

dead on, balls accurate?

That's Marisa Tomei's line in My Cousin Vinny. She's the daughter of a mechanic who clinches the mystery of an armed robbery at the end of a lost-cause trial.

http://www.youtube.com/watch?v=DhL5exi_avE

Jeff

[LotusSevenMan]

I have never seen that film Jeff but I liked the clip!!!! 

[jdrouin]

Actually, I sent the wrong one. It's in this clip, from about 1:15 to 2:15. For some reason I thought the line was repeated later as a clincher in the trial, but it wasn't. The technical humor is good in this one too, as well as certain other... ahem... aspects.

http://www.youtube.com/watch?v=M-ZyxRNCTuc

Jeff

[LotusSevenMan]

The  new clip is "Dead on, balls accurate" !!!! 

[cyrusb]

Its an industry term!

[LotusSevenMan]

Maybe I'd better not ask which 'industry' if it turns out to be the worlds oldest profession   

[jimsE]

baird4444,
Thanks for the link to "tinytach".  I guess REs have one spark for each revolution(wasted spark on the exhaust stroke).  Right?
Thanks,  Jim

[baird4444]

I think that is correct but don't quote me. I never bothered remembering that one cause I didn't plan on ever getting the tach.
                                                              - Mike

[birdmove]

   I'm going to bet that the Bullet does not spark on every stroke. Why? Because if they did,then when you used the method of parking the bike with the piston at TDC on compression stroke, said method wouldn't work.You apply the compression release, and turn key on.Ease the kick start over till you see the ampmeter needle go to the far left, then a bit more till it comes back to the right. If this thing fired a spark on every revolution, then this method would not find TDC on compression stroke--but just TDC period.
    Someone smarter then me tell me if I'm right or wrong please.

    jon

[cyrusb]

The ratio of crank to  cams and distributor is 2:1.  Dist turns half engine speed.

[Trapper]

I have an xls spreadsheet calulator for this. With a 17t sprocket, I get 4200 rpm for 65mph, 3800 for 60.

[Bankerdanny]

dead on, balls accurate?

That's Marisa Tomei's line in My Cousin Vinny. She's the daughter of a mechanic who clinches the mystery of an armed robbery at the end of a lost-cause trial.

http://www.youtube.com/watch?v=DhL5exi_avE

Jeff

Ah, my friend, I got the reference. I was hoping you would give me the follow up: "It's an industry term."

[jdrouin]

Ah, my friend, I got the reference. I was hoping you would give me the follow up: "It's an industry term."

Alas, my own memory of the sketch was not up to par!

Jeff

[Bankerdanny]

Shame on you, neglecting the classics