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Old 23-06-19, 10:53 AM   #11
Othen
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Haha, indeed. Rollie must have been mental, it would have been bloody painful being sandblasted with what the tyres were chucking up, let alone what could've happened if he'd lost it and fallen off ....

Also I never believed the Suzuki speedo legend "60mph = 2240rpm", or at least that's not crankshaft rpm. My old GT380's 6th gear was about 13mph/1000rpm, so it would've been doing 4,600rpm at 60. I can't imagine the B100P's top gear being twice as long, somehow


The speedo’s legend does seem odd, particularly as the manual says the motor makes 10 HP at 7,000RPM - I’d say 70MPH feels like near the top of that range, something like 6,000RPM. It does seem a bit odd, but that is what it says...


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Old 23-06-19, 12:53 PM   #12
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Indeed - my old B100P had the same legend on the speedo. It's not wheel RPM either. Who knows?
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Old 23-06-19, 01:15 PM   #13
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Indeed - my old B100P had the same legend on the speedo. It's not wheel RPM either. Who knows?


Ah ha, I have it in full; I found this on a US XS650 site:

Well, all Japanese motorcycle speedometers are calibrated to show 60 MPH when the cable is spinning at 2240 rpm. With a front wheel diameter of 19" the rolling distance is about 79" per revolution, or 79/12 = 6.58 feet. At 60 MPH or 1 Mile Per Minute the wheel will rotate 5280/6.58 = 802 RPM. So, you would need a speedometer drive with a 2240/802 = 1:2.79 ratio which is pretty close to your 1:2.75

... so, it is nothing to do with engine speed, it is the speedometer drive calibration.

One learns something new every day (well, not Tuesdays).


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Old 23-06-19, 01:48 PM   #14
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Indeed - my old B100P had the same legend on the speedo. It's not wheel RPM either. Who knows?


This makes more sense: my Bloop has a 2.75”x17” rear tyre, so its circumference is 71”. 60MPH is a mile per minute, so the rear wheel will rotate:
(1760*3*12)/71 = 892 times in a minute.

The gear ratios on the Bloop are (in top gear):
(3.125*1.1*2.214)=7.61 overall.

So, for every 892 rotations of the rear wheel the crankshaft rotates 892*7.61=6788 times.

6788 RPM at 60 MPH makes sense (maximum power is quoted as 10 HP at 7000 RPM)... so I’m really impressed with the Bloop reaching an indicated 70MPH yesterday (admittedly down a slight slope and after a 2 mile run up), particularly with my 6’2” 210 lb frame attached to it (and not wearing Speedos whilst impersonating Rollie Free).



PS. I cleaned the baffle according to the article Craig380 provided a week or so ago, it only took about 10 minutes with a wire brush and a propane torch to get it looking okay - maybe that accounts for the improved top speed?

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Last edited by Othen; 23-06-19 at 02:00 PM.
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Old 23-06-19, 04:54 PM   #15
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Aha, speedo mystery solved! And yes, clearing the baffle does help. The most important bit to clear is the internal diameter of the baffle, when that's as clear as possible it will run as Mr Suzuki intended ...
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Old 24-06-19, 05:01 PM   #16
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Aha, speedo mystery solved! And yes, clearing the baffle does help. The most important bit to clear is the internal diameter of the baffle, when that's as clear as possible it will run as Mr Suzuki intended ...

... that article was quite helpful - the bit about adjusting the ignition timing is much better than both the Suzuki and Haynes manuals.

I took the Bloop out for another needless errand today, a trip around town wearing shorts, tee shirt and an open face Nolan helmet... I was 17 again.


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Old 25-06-19, 06:31 AM   #17
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... that article was quite helpful - the bit about adjusting the ignition timing is much better than both the Suzuki and Haynes manuals.

I took the Bloop out for another needless errand today, a trip around town wearing shorts, tee shirt and an open face Nolan helmet... I was 17 again.
Haha

I never had a flywheel puller when I had my B100P so had to resort to doing it all through the flywheel slots
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Old 25-06-19, 06:50 AM   #18
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Haha



I never had a flywheel puller when I had my B100P so had to resort to doing it all through the flywheel slots


Eeeek! Now that would be a hard job. It is a real faff even with a puller: adjust the timing ‘a bit’ - put the flywheel back on, adjust the points through the little slot and see if it is right, if not pull it all apart and try again. We have all been spoiled by electronic ignition and forget this was the norm 40 years ago.


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Last edited by Othen; 25-06-19 at 11:53 AM.
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