Bonneville America Forums Forums Technical Forums Performance Mods NOT a BB but still interesting

I spoke to Carlos at TPUSA today...hes great to talk to and very informative in a not pushy kind of way. I got some really good info from him and Ill share it but I know Im forgetting some of what he told me...here goes.
BTW...Im quoting Mag10 cause his questions/comments were the same as the ones from ym conversation today...

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looking at these dyno charts (and everyone elses)cams seems to be the biggest improver (for the 865 motors), followed by getting away from the stock pistons.

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EXACTLY...Ive heard it before but he was able to confirm it. Triumph detuned the 865 motor with cams to pass emissions. The 865 (270 especially) responds really well to carbs and cams.
When I mentioned cams before carbs he said (not quoting, paraphrasing here) yes, that will be a good upgrade but I would get a beeter torque number at lower RPMs with carbs before cams.

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It is a pretty small increase in displacement, it should be possible to get pretty close to the same power out of both.

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I specifically asked about this...HP yes but not Torque. He referenced the dyno runs with the 865 HC kit vs typical 904 results (funny, kinda like I did in my earlier post). At a certain point the 865 becomes limited...if I remember it was a combination of lack of clearance for valve opening that would be needed by the cams as well as simply not being able to move enough air through the motor (limiting factors being carbs, cams, displacement, exhaust). Displacemetn being teh biggest factor as all other area easily changed.
This all led to the reason for the 865 HC kit...there was a demand for more without the machine work of the 904.

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although if you go to the effort to change out the pistons, and for a couple of bucks more do the 904, why not.

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I brought this up as well...the bottom line here is that that little 39cc of increase is enough to get this little motor to boogey. The 904 kit increases displacement enough to provide more room in the cylinder for bigger valves which opens this motor up to higher Tq numbers at lower RPMs.


The great thing is that he did not push one way or another. He gave great info about each kit but also gave even better insight as to mods and order fo mods to get to my final result in an orderly manner since I dont have a bag of cash to drop in his lap.