Where Do I Find Inexpensive Horsepower?

[Brad]

Hi All,
Im looking to gain a little inexpensive horsepower on my butchered XS11, any leads?

[CatatonicBug]

Really, to gain anything noticable, you're gonna have to spend a chunk of money. These machines were built as solid monsters, with little that can be adjusted in that area. Some have said that pod air filters add HP, and some have said they even lower it, but most agree it's nothing you'll notice either way.

Really, the only thing that will change the HP much is a big bore kit. That's where the $ comes in.

[Big Daddy Funk]

Bang For the Buck

A Dynojet Kit for the carbs makes a difference you will notice. About a hundred bucks.
Rick

[79XS11F]

The cheapest HP you will find is with a 4-1 header and properly jetted carbs for that pipe. If the pipe is one of the performance types and jetted properly you can get up to 10% additional HP.
Rob

[Ken Talbot]

Unless you already know what your bike can really do, you might be surprised what well cleaned carbs and a proper sync/colortune can do for you. If you have only ridden older, smaller displacement bikes, you could hop on an XS with two dead cylinders and think it was okay. Before I got Tsunami, my biggest ride was my old '51 BMW R51/3, which probably put out about 25 hp on a good day. OTOH, if you are thoroughly familiar with what a finely-tuned XS can do, finding more inexpensive horsepower might be a challenge.

[trbig]

I've been told that newer hotter coils makes a noticeable difference.


Tod

[Ivan]

Mega Cycle will weld up and regrind your cams to a hotter profile for about $400 I think. It looks like you have a 78 or 79 clicking on the liink in your post, so your compression ratio will actually go down if you go with a Wiseco bore kit. I have heard from a couple guys that the bore kits them selves don't add noticeable HP gains, so I think the money would be better spent elsewhere.

Probably your cheapest gain will be a good jetting and A dynojet kit, but if you have the early carbs, there is not one available, but the needles are adjustable in those carbs, which is what the Dynojet kit does on the later carbs.

My thinking is that the HP is still climbing and the bike just pulls harder and harder even at redline, so increasing the redline would be where you could really start seeing some gains, especially with a good 3 angle valve grind and some port work. Being able to raise the redline a couple grand would be great as well. As far as I can tell, valve float is the determining factor there, and valves don't float because the springs are too light, but mainly because of the waves that travel through the springs, so high performance engines use progressively wound springs. Maybe finding some more modern valve springs of the same diameter off a toyota or something might do the trick there. For a good read on that, look up "desmodromic valves" on Wikipedia.

Also for the rough 1000 bucks it would take to get a bore kit done, you could probably find a turbo setup, which would definitely give you a bigger boost than anything naturally aspirated.

[blue giant]

You could just buy a Harley Davidson motorcycle and.......................


......... oh wait............ that's expensive horsepower.

sorry

[XSokieSPECIAL]

$1000-$1500+............................ horsepower ain't cheap.

More than 1 hp per lb ain't enough for you?

[Larrym]

Other Side of the Coin?

Increasing horsepower is one way of increasing top speed and the acceleration needed to get to that top speed quicker. But there's another approach.

The overall acceleration is determined by the horsepower to weight ratio of the bike/rider combination.

Stripping "unnecessary" weight off the XS can be done but each essential component removed must necessarily be replaced by a lighter, therefore usually much more costlier item. Sourcing and then modifying these lighter/stronger components can be a daunting task and not really cost effective in a "pounds loss vs cost" analysis.

Downsizing (Rightsizing??) the weight of the rider seems to be the most cost effective means of achieving higher performance:

Cost Comparison

Jenny Craig:

According to the folks at J.C., average cost is approximately $65/week. However, there are different membership options which afford different benefits, and one can spend as much as $400 in the first month.

Nutrisystem:

$54.95 per week (includes meals and snacks). Save 15% by signing up for the Auto Ship plan.

The long term benefits and continued monitoring of the performance gains of rider weight reduction must require the use of the bathroom scale along with regular trips to the race track. Elapsed Times in the 1/4 mile should be used to verify performance gains and continued adherence to the chosen weight loss plan.

It's really just a matter of mathematics and which side of the equation you choose to work with.

[clcorbin]

More than 1 hp per lb ain't enough for you?

Uhm, math??? Bike: around 600 lbs.
My Fat Butt: around 280 lbs.
Total: 880 lbs

Horsepower: MAYBE 90 hp on a good day. Oh, wait. I'm at 5200 ft, so deduct 12% or 79 hp on a good day up here.

Power/Weight = 79 hp / 880 lbs = around 0.080 hp/lb!!!!!

So, yes, 1 hp/lb would MORE than be enough! I'm just over an order of magnitude away from that lofty goal!

Just to be fair, I have to assume you actually meant hp/in^3, which should come in at 79hp/67 in^3, or right at 1.18 hp/in^3

[fredintoon]

- - - - Downsizing (Rightsizing??) the weight of the rider seems to be the most cost effective means of achieving higher performance: - - -

Hi Larry,
body mass reduction works best when racing in the 50cc class as 40lbs less on a 100lb bike is far more effective than 40lbs less on a 600lb bike.
However, even with a heavy bike one cannot deny the math, eh?
So what's the least costly way to loose weight? As you say, Jenny Craig, Weightwatchers etc charge top dollar for membership.
Provided you have good medical coverage, here's a less costly way:-
Go mouth off in a rough bar.
Some Redneck will undoubtedly break your jaw.
You will spend the next few months with your jaw wired shut.
Weight loss is inevitable.

[Pat Kelly]

"Want to lose 10 pounds of unsightly fat?

Cut off your head"

read that on a bumper sticker in the 80's

[bikerphil]

Hi All,
Im looking to gain a little inexpensive horsepower on my butchered XS11, any leads?

You can cheat and advance your timing a few degrees. Cost: nothing, maybe a piston or two.

[MNS494]

I've read where the older xs's were faster but i don't know why..........