Triumphrat

Nathan · 03-22-2007, 01:45 PM

This is spinning of from that other thread...

Did a quick search but didn't see any direct real-world performance comparisons.

The yack I hear is the 865 wins in low-end torque, but provides a negligible difference at higher rpms. Total bunk?

Anyone have this data? Butt-Dyno results even?

Cheers!

~N

sweatmachine · 03-22-2007, 01:50 PM

I say negligible difference.

kliff · 03-22-2007, 03:34 PM

Can't really speek for the 865, but what I will tell you is my 790 took me (all 270lbs) to an indicated 111mph with only a simple rear baffle removal, and needle shim addition.
Now, with better mufflers, K&N, "bellmouth" and apprpriate jetting the speedo has hit 118 severral times. All with stock gearing too. Those are probaly actual speeds of 101 and about 109....plenty good enough for me.

RedBird · 03-22-2007, 04:08 PM

I agree with the negligible difference. IMHO, the major difference is due to the difference in cam timing, not the additional cc's. One difference that I would think about (for a couple of minutes) if purchasing with a choice of 790 or 865 would be the difference in the rev limiter setting on the stock igniters--the 790 being 7400 rpm and the 865 being 8000 rpm. I also feel the major difference between the 904 BB kit and the stock engine is the higher compression pistons, not the additional cc's. The 865's appear to benefit equally with the 790's from this modification.

Larry

sweatmachine · 03-22-2007, 04:16 PM

Quote:

On 2007-03-22 14:08, RedBird wrote:
The 865's appear to benefit equally with the 790's from this modification.

Larry

I'll let you know about that this weekend...I'm reassembling my 865-904 tomorrow! :-D

DrEnglish · 03-22-2007, 05:57 PM

865 is bigger. And we know what that means. Seriously, mostly bragging rights AFAIK...

Besides, where's my extra 35cc for my Thruxton 900? Was my bike a ripoff? P'raps a lawsuit is in order.

dazco · 03-22-2007, 07:14 PM

I think the 865 speedmaster's torque really does make a difference. Not sure about the bonnie 865. But one thing people don't realize is that while the bikes are not that different in acceleration, the speedy 865 is geared considerably higher yet still retains acceleration about the same as the 790 even tho the higher gearing should make it slow to catch up. From what i gather theres not much difference except at high speeds the bonnie seems to be a little quicker in a roll-on. But with lower gearing it should be even if the engines were exactly the same. I've read lots of posts where people cited thier RPM's at a given speed and the bonnies are always quoted at higher RPM's at a given speed. Thats why bonnie owners are more rabid about installing bigger front sprockets, and also why they often find too bigg a loss in low end when they go up more than a tooth. As for the 790 speedy, i dunno whats different there. All i know is that the RPMs/speed ratio i always see in regards to bonnies are considerably lower than mine, and even with a 17 on the front and a 41 on the rear, mine pulls quite hard.

Anyways, point is i think gearing is the often overlooked part of the equasion. And don't forget not all 790's are the same, and not all 865's are either. Different models with the same CC have different cams and jetting and who knows what else. It's a puzzle.