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Discussion Starter #1
Hi all

I’m not a leary rider and tend to bob along at 60-70mph enjoying the lovely mid range. I’ve done a number of handling and performance mods and am very happy with the bike.

I understand these are not sportsters but, I was blatting along on the Bonnie yesterday and was wondering about top speed. The old girl hammers up to an indicated 90 (quite impressively actually) and then slowly gets to the ton (I eased back here as I don’t like wringing the neck of a bike), I was interested in what other 790s top out at and how they get there?

Chris



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Discussion Starter #4
I would expect it to top out at about 115 / 120 .


I think 120 might be a stretch but I can see it achieving an indicated 110, I will count the sprocket teeth and see if that’s restricting top end...


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I think 120 might be a stretch but I can see it achieving an indicated 110, I will count the sprocket teeth and see if that’s restricting top end...


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Even before I changed wheel sizes on my Thruxton the speedo was only occasionally accurate with the needle waving vaguely at speeds in excess of 80 . I now use a gps speedo . >:)
 

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Discussion Starter #7
Even before I changed wheel sizes on my Thruxton the speedo was only occasionally accurate with the needle waving vaguely at speeds in excess of 80 . I now use a gps speedo . >:)


Yep, I do doubt my speedo above 90 odd... but then again I wave vaguely above 90 with no fairing...


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choose your model

Top Speed Motorcycle.com tested the 2011 model XR1200R Sportster, and the top speed attained by the bike was 122 mph. Older versions of the Sportster don't attain this speed. The 2001 Sportster 1200 Customs have a top speed of 106.9 mph.
My bonnie now runs 8k revs but not in top. Maybe need to find that sportster!:surprise:
 

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Top Speed Motorcycle.com tested the 2011 model XR1200R Sportster, and the top speed attained by the bike was 122 mph. Older versions of the Sportster don't attain this speed. The 2001 Sportster 1200 Customs have a top speed of 106.9 mph.

My bonnie now runs 8k revs but not in top. Maybe need to find that sportster!:surprise:
Dang!
 

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Sounds fairly realistic actually...


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I've run five bikes at Bonneville Salt Flats four times and only one time have I been able to get a certified top speed to match the Gearing Commander. I'm willing to concede the Bonneville Salt Flats surface and elevation make it difficult because on asphalt at sea level the bikes perform better. The tradeoff is at Bonneville you get three miles to run wide open and that is tough to find on public highways.

I had a 2003 T100 790 and later a 2009 865cc Thruxton. The stock Thruxton ran 125.1mph at Bonneville which was the only match I've ever gotten with gearing Commander. I thought my stock 790cc felt stronger than my stock Thruxton but I never did a top speed on it.

However with the proper gearing and enough road I bet it would run at least 120 mph. Those 790cc were sweet.
 

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Discussion Starter #13
I've run five bikes at Bonneville Salt Flats four times and only one time have I been able to get a certified top speed to match the Gearing Commander. I'm willing to concede the Bonneville Salt Flats surface and elevation make it difficult because on asphalt at sea level the bikes perform better. The tradeoff is at Bonneville you get three miles to run wide open and that is tough to find on public highways.

I had a 2003 T100 790 and later a 2009 865cc Thruxton. The stock Thruxton ran 125.1mph at Bonneville which was the only match I've ever gotten with gearing Commander. I thought my stock 790cc felt stronger than my stock Thruxton but I never did a top speed on it.

However with the proper gearing and enough road I bet it would run at least 120 mph. Those 790cc were sweet.


That’s some solid data, thanks mate!


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I had a 2003 Bonneville T100 790, now a 2015 T100 865. The 2015 feels stronger to me. The 790 was buzzy and working at 70 mph, the 865 seems to enjoy higher speeds.
 

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I had a 2003 Bonneville T100 790, now a 2015 T100 865. The 2015 feels stronger to me. The 790 was buzzy and working at 70 mph, the 865 seems to enjoy higher speeds.
I didn't dyno the 2003 T100 but I remember the claimed horsepower as 61 but I dd dyno my 2009 at 54,79.

I'm pretty sure your 2015 had more power than my 2009. I do remember weighing both and the 790 was about 30 pounds lighter than my 865.
 

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Discussion Starter #16
I didn't dyno the 2003 T100 but I remember the claimed horsepower as 61 but I dd dyno my 2009 at 54,79.



I'm pretty sure your 2015 had more power than my 2009. I do remember weighing both and the 790 was about 30 pounds lighter than my 865.


Yeah claimed power is at the crank whereas you will (I assume) measure start the wheel.

I’m fairly sure mine is making a little bit more then that now (and is missing a few heavy bits). The modifications I’ve done are the same as the ones on one of TTPs test bike and that was had a curve producing around 70bhp at the wheel with a significant gain in torque from 3500 onwards.. mine is a little lean at the moment but will get 142 jets as soon as I get around to it.. then a balance the carbs and leave it alone ...

I’d like to run mine on a dyno and find out how much power she makes but I doubt I will..


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Discussion Starter #17
Ok, I’ve fitted the larger jets and balanced the carbs.

Bike has baffle out, bell mouth fitted, performance filter, TTP coil TTP igniter (mapped), iridium plugs, 143 mains, 1 shim on needle and standard (probably) pilots with mixture screws at 2 1/2 out.

I have found that it is very (very) responsive through to about 80-90 mph where the fuelling then goes awry and the bike seems to loose power at full throttle, but if the throttle is feathered it will pick up again slightly. In the lower ratios this is almost unnoticeable as the bike buries the needle into what was the red line.

I am more then happy with the performance from 0-80 and really that’s all I’ll ever need but I’d still rather it was spot on..

I would appreciate some advice on the fuelling at the top end?

Chris





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What exhaust mods do you have? Do you have stock gearing, larger front sprocket or taller rear tire? If so it should get to 100 mph quicker in forth gear than fifth gear. Also, I agree with @Back2-2 on the too much main jet.
 
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