ladisney
Loquacious
Reged: 01/12/05
Posts: 3166
Loc: Des Moines, Iowa, USA
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Like many on this forum I've wanted to increase performance on my BA. The problem is figuring out what I need to do to get to, say, 75 horsepower or 80 horsepower or 100 horsepower. What mix of performance mods will achieve my goal? Which exhaust, which intake mod, which jets, etc. With many automotive applications there is almost a cookbook available. For instance, with a Chevy 350, if you do certain combinations of modifications you get certain performance within a small margin of error. Has anyone put together this data? Do we collectively have the data to do this?
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"Democracy is the theory that the common people know what they want, and deserve to get it good and hard." -- H.L. Mencken
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Deon
Saddle Sore
Reged: 01/11/05
Posts: 5172
Loc: SW Pennsyltucky
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Pick a number. The modifications range from mild to wild. I think 100 horses is probably beyond the capabilities of these 790cc engines.... but there are big bore kits.
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More flags
More fun!
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jazzplayer
Adjunct
Reged: 01/13/05
Posts: 134
Loc: Longmont, Colorado
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I think there are a lot of varibles that don't translate perfectly. Carb tuning for one is very dependent upon where you are riding. The right jets for someone in New York or LA are not going to work for me at all here in Denver because they'll be way too rich. As far as your numbers go;
75 hp - will require a big-bore, performance exhaust, air filter mods of some type and carb jetting or possibly higher performance carbs
80+ hp - there was a story in the Summer 2004 edition of Torque detailing the mods made to a stock Bonneville to get 84 bhp @ 7250 rpm - bored out to 944cc with higher compresson pistons, custom valve work, 42mm Mikuni carbs,K&N filter, ect.
100+ hp - buy a Daytona or Speed Triple
Basically you can get about an extra 10-12 hp with pipes and jetting after that you get into pretty serious mods from a technical and cost standpoint. You'll also need to upgrade your brakes (at least on the BA) and suspension as well once you get past about 65 hp.
Keith
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Dinqua
Worn Saddle
Reged: 01/11/05
Posts: 6261
Loc: Honeoye, New York
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Speed is $$, how fast do you want to go?
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A word to the wise is not necessary. It is the stupid ones who need the advice.
Pat
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ladisney
Loquacious
Reged: 01/12/05
Posts: 3166
Loc: Des Moines, Iowa, USA
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I guess that's my question in a nutshell. All those mods are out there but what combination will get you what net increase in power? I've worked on the Chevy small block a few times and we could always work backwards from a horsepower/torque requirment and figure out what we needed. Of course there must be 50 million small block Chevys in the US and millions of them have been hopped up so there is a huge knowledge and experience base to work from. As far as I know, when it comes to the Triumph 790, this is the best resource and there really aren't many of us. I'm just wondering if we have the knowledge base to tell us what the result is of various combinations of modifications. Some Harley freak was talking about the mods they have available and said they can put together various mods and know in advance what the result should be. He asked if we could do the same and I just don't know.
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"Democracy is the theory that the common people know what they want, and deserve to get it good and hard." -- H.L. Mencken
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Dinqua
Worn Saddle
Reged: 01/11/05
Posts: 6261
Loc: Honeoye, New York
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Well, here's a start with "guestimates" on gains (just my take, not a scientific sample)
Free stuff;
Gut pipes using one of the hole saws in here (1-5hp?)
Cut hole in bottom of airbox (1-2 hp if done with pipes)
adjust pilot screws so they are at least the same on both sides (no gain, just idles better)
Cheap mods:
new jets - $10-25 (gains maybe 2-4hp if done with pipes/air mods)
TBS needles - $15 smoothes out dip in middle of throttle
JC Whitney pipes - $80 loud and maybe gives you 1-3 hp?
front springs - $70 smoothes front end dive, better handling, no HP gains
more $$ mods;
Aftermarket pipes - $200-750 Gains are from minimal to reported 15% hp increase with Thunderbike pipes
rear shocks - $200-450 pair huge difference in handling, which is directly porportional to performance, no HP gains, but ability to ride better and track smoother increasing effeciency overall.
Big bore kit - kit is about $400, another $400 for parts if you do labor - hp gains? TBD soon!
Carbs - CR's, $500 smoother response, better performance, hp gains?
$1750 Mikunis - 42mm flatside carbs, hold on! Big throttle response, big $$ but maybe too rich for the bike without big bores. hp gains?
FCR carbs - NEW!! $1250, 39mm flatside carbs should give huge throttle response, hp gains?
Lesser done due to expense, mods:
Cams:$800 gains not yet known
Bigger big bores - $1500+ , gains unknown
Valves/shim under bucket conversions - ?$ ? gains
well, it's a start....
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A word to the wise is not necessary. It is the stupid ones who need the advice.
Pat
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Cody
Adjunct
Reged: 01/10/05
Posts: 704
Loc: Holland, MI
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There was a story in one of the mags, probably Cycle World, in 2003, about the time I was buying my bike, that told about a Triumph shop (I think in California) that modified a Bonneville to make over 90 HP. I don't remember much except they did the whole gamut, bored, port and polish, cam, etc. That's all I can tell you.
It's hard to find accessories made specifically for these bikes ( with the exception of guys like Brent ), let alone detailed performance information. Try to find something as common as a windshield that is marketed specifically for a BA/SM. They just do not yet have critical market mass. They certainly are not as ubiquitous as a Chevy small block. But then, that's kind of what makes if fun. We feel like pioneers breaking new ground.
Good luck with that.
John
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I was born a long ways from where I was supposed to be. - Bob Dylan
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