Triumphrat

SCCTrim · 04-01-2007

You speak the truth, test's have shown that a head with +1mm oversized valves doesnt benchflow as well as a head with +2mm oversized valves...but it does make more power...( I'm certain I read a post from Bill Gately stating this, my apoligy's if I am mistaken )...as with everything else it's the entire package that make's the best end result, not 1 individual addition.

...but to assume that you wont see a gain from a larger carb is silly when relating to our bikes. My bike gained a full 8 horses just from carbs alone when compared to a previous run on the same dyno, with the same operator.

Going larger than a 42mm carb on a 790 or 904 kitted bike just doesnt make sense of course....there are line's in everything.

Jimbonnie · 04-01-2007

"...but to assume that you wont see a gain from a larger carb is silly when relating to our bikes."

The fact that the carb is larger isn't nearly as important as the fact that it's less restrictive. The stock sized carb throats are more than capable of supplying all of the air fuel mixture stock motors can handle at less than explosive rpms. Carbs larger than optimum can easily decrease power, and destroy power at lower rpms. The key is having the optimum flow velocity with the least restrictive carbs. As usual, there's more to it than bigger is better.

SCCTrim · 04-01-2007

The fact that the carb is larger isn't nearly as important as the fact that it's less restrictive

Agreed

Carbs larger than optimum can easily decrease power, and destroy power at lower rpms.

Again I agree, but the hsr's aren't impeding power. That's kinda my point here, these carb's have been tested both on the street as well as on the track. Every bike that has had these carb's installed has seen power gains...not deficit's.

So at what point do you draw the line of larger than optimum?

It seem's absurd to install a 42mm miks on one of our bikes, especially considering hd's are only running one. I know when I got my carb kit they looked kinda freakishly big next to the little cv's they were replacing.

A lot of dyno run's and more info about our bike's with these carb kit's installed can be found Here

It's the delphi forums incase the link is a mess, seem's to have issues more often than not when posting a link to there. 2001 Modified Triumph Bonnevilles is the specific forum. Bill is a regular there, I'm sure he or other's would be willing to answer any question's you may have regarding the hsr's ability or lack there-of to make power gains.

150+ customers cant all be wrong...

SPRINGER1978 · 04-01-2007

i guess im drawing my conclusions from my hd dyno expeience. the stock cvs are the best and most cost effective carbs for harleys. s&s and mikuni are better carbs no doubt but in our shop some people confuse horsepower with throttle response. on another note if cv carb are so bad why does hd even produce larger cv versions 44 and a 50 mm for the older 103 kits and not just sell the mikunis they have in the s.e catloge. also i will tell you something will pick up 10 horses if you want to buy it from me and ill make money. nothing against bill ,bought parts from him but everone is not selling to lose money. also i am certfied to run the dynojet dyno at our shop and trust me if you want me to get you a print out with 5 more horses from bolting a fluxcapacitor onto a buell blats i can !

bonnieblackinfl · 04-01-2007

Comparing HD's and Triumph's is apples to oranges. Triumph's right on track with a 4V head, which increases velocity and has more valve surface.

HD needs to catch up on the times and throw out their old boots. As far as the CV carbs, you are right with the power department with the HD's, perhaps it's the port design they are using that doesn't allow for the full performance a HSR can offer.

CV's are more cost effective than the HSR's. Plus why would HD offer a superior carb stock, when they make a killing off the SE carb? BTW, I'm not HD bashing, I love HD's and other cycles as well, I'm a true enthusiast.

I know on my 790 the HSR's provided 10hp over the CV's. The CV's delivered 57hp, when I installed the HSR's my first dyno was 67hp with an a/f ratio of 10.-11.5. My last dyno I put down 70hp @8300rpm, with an a/f ratio of 12.5

Our engines are built very well, but have been choked to appear under powered, period. All it takes is an exhaust, pod filters w/o an airbox and Mikuni HSR's to deliver 70 or more hp w/o cracking the engine case or pulling the head.

Hell, I don't even have a good exhaust, gutted Thrux cans w/a thunder-monster type ghost ring in the header 3in from entering the can. I would like to dyno w/a set of predators just to see what the difference would be.

The proof is in the dyno, the numbers, and my ass, say that the HSR's fuqing rock on our Triumph's over the CV's. :hammer:

Greg

SPRINGER1978 · 04-01-2007

hd does offer mikunis! and you have issued a challeng i recently came into some money(thank you irs and my two little tax deductions) i shall build the end all be all of triumph twins and use cv carbs maybe be a larger size but cv non the less.

bonnieblackinfl · 04-02-2007

Yes HD offers the Mikuni HSR's, badged SE, but not on a run of the mill production cycle, excluding the the SE production cycles.

I did not mean to present a challenge or seem controversial, I'm stating the facts!

The Mikuni HSR 42mm PRODUCES 10HP OVER A 36mm CV ON AN OTHERWISE STOCK 790..period. :brk:

Greg :-D

BeastInBlack · 04-02-2007

Well in theory then considering my head has been skimmed, and gasflowed giving 69 bhp, i should be looking at the high 70s, and that is not even considering cams! just a shame about that 6th gear...

tcb · 04-02-2007

Something that hasn't been mentioned here and probably is important to this discussion is the fact that CV carb's were put on most bikes because of their ability to only deliver mixed fuel at the rate the engine could develop vacuum, thus delivering smooth accelleration no matter how heavy handed you were with throttle controll. The bike behaved in a more civilixed manner, which gives better magazine reviews and sells bikes. Performance often was not optimized.

MAR · 04-02-2007

I noticed a lot of you are using 39mm and 42mm carbs. What about the Keihin BCE-024 35mm carb? It would seem to be more street-able with more mid range.