Big Bore, How much more power?

[cochie]

I am thinking of big boring my xs1100. Can any one tell me how much more power & top end i will gain. Also any other methods along side this to increase power/exceloration ect. Many thanks Cochie

[Ivan]

Well, like the final drive mod with mileage, you'll find that the verdict is unclear on the bore kit. Some have said its a huge boost, some have said not. I have yet to do it, so I am not a first hand experience. I can say that I have kept pace with guys that do have a bore kit on my 79, which isn't bored. But it will absolutely smoke my 80 (actually a 80 frame, with a 78 engine and some 81 parts ) which is stock fare as well.

When I get a rountuit, I am going to explore the cheaper ideas first. Port matching the head is a labor only pursuit and as far as I can tell, if you're just matching the ports to the manifolds and exhausts, could be done on the bike if you're extremely careful to keep filings out of the engine. I'd try it on my bike. Trying to do a full porting job would require yanking the head, so you'd possibly need a head gasket, but some have successfully used them over again. Also, I think its Megacycle that will weld and regrind the cams, which runs around $450, where a bore kit will run upwards of $2000 with machining and replacement gaskets and seals and such. If I were going to spend money, I might start with a set of those.

Another excellent resource for this is DanHodges. I haven't seen him on here for a while, but if you search for his posts, you'll get more information than the mortal mind can handle. Great stuff for gearheads.

[fredintoon]

I am thinking of big boring my xs1100. Can any one tell me how much more power & top end i will gain. Also any other methods along side this to increase power/exceloration ect. Many thanks Cochie

Hi Cochie and welcome,
more power? Nitrous for pulling away from stop signs and a turbo-charger for long range.
Seriously though, the XS11 already has more power than it's brakes and steering can cope with.

[XJOK2PLAY]

Cochie,
Welcome to the forum.

At best, real world expectations... if you have lots of $$ and time and experience wrenching... best you might hope for would be 100 hp.
A big bore kit alone won't give you that much increase.
It'll take that, and several other mods to get an 11 to that point.

But, a big bore kit, (1196 Wiseco) is a great start.

Like Fred said... these bikes already have enough power to challenge the brakes and the handling departments as they are. So, if you do increase the HP, plan on mods in those areas as well.

Regards,
Bob

[TopCatGr58]

Hey Cochie,

A search for the word POWER will reveal many threads, but you'll find the ones regarding big bore kits as well. Oh, duh, search big bore! Also search for dyno results/tests.

We don't know your experience with the XS11..have you had it long, ridden it much, etc.? Remember that these are OLD bikes and engines and technology. They will still only top out at about 135mph max, so almost any 600+cc crocheteer will take your lunch on the top end!

As stated, with proper tuning, they put out plenty of power for their size/age and frame and suspension capabilities. So, depends on what you are really wanting or expecting from your machine.

I've done the "little" 1179 big bore, but it had been 9 years earlier that I had been able to ride/drive my machine, so my seat of the pants memory was rather faded by that time. I do feel it's definitely stronger than it was before STOCK..and mine was an 81 which was the weakest of the XS11 series, and had a bit more head combustion chamber volume, so the alleged increase of compression that WISECO claims is supposedly less than the 10.5:1 that you should get with an earlier 78-79 engine vs. the 80-81 engines/heads. However, after it was broken in, I got 175-185 PSI compression across the board with otherwise stock head parts...cams, valves, no porting!!

If you're wanting an XS11 to be able to compete with crotch rockets...forget about it unless you're just doing street light to street light runs!

[lee_dutcher]

I am thinking of big boring my xs1100. Can any one tell me how much more power & top end i will gain. Also any other methods along side this to increase power/exceloration ect. Many thanks Cochie

i think a member on here has a turbo on his 11.. might want to check that out. might spend a little bit more. but if you do it your self might not be bad.

[DGXSER]

You might want to search through some post from member Dan Hodges. If he don't know all there is to know about making power with these machines, he can't be to short of it. He has posted a few threads based upon thinge he has done that give results of different upgrades, like boring out the cylinders.

[XJOK2PLAY]

Also, might add one more thing...

My advice if you decide to do the big bore...

Before you do, take the bike to a MC dyno, and make a couple of runs.
Then do the big bore. Take it back to the dyno after it's good & broke in.
Compare. Then you'll know. MC's will vary somewhat... especially depending on tuning, compression, carbs, cams, ignition, etc.
That'll give you YOUR realword performance figures for your bike, though.

Costs a bit to do it, but that's what I'd do to find out for sure.

If you're looking to make power on a budget, one thing I've been told is for every 6 pounds of weight you drop, it's equivelant to adding 1 HP.
JAT

[Rasputin]

If you're looking to make power on a budget, one thing I've been told is for every 6 pounds of weight you drop, it's equivelant to adding 1 HP.
JAT

So what your saying is I could gain about 18Hp if I weighed my ideal weight

[XJOK2PLAY]

So what your saying is I could gain about 18Hp if I weighed my ideal weight

Well..... that's what 'THEY' say....

Is that also why horse jockeys are always the little 90# types?

[newc4]

My 79SF has the 1179 big bore. I can't tell much difference from my 78E. Has a little more at the top end.

[clif731]

I am thinking of big boring my xs1100. Can any one tell me how much more power & top end i will gain. Also any other methods along side this to increase power/exceloration ect. Many thanks Cochie

if it's hp your looking for you can't beat a turbo.that's if you like to roll the throttle on in 3rd gear and stand your bike straight up almost over backwards and top speed at 150 plus then a turbo is for you. by the way i have one for sale on here

[cowboybob998]

more cubes more horse power

Thats the bottem line of drag raceing, the biger the faster.
I dont care what any one says about any motor, if you set it up right its gona run faster if you bore it, but they are right about how fast ( top end ) it is gear bound with the rear drive.
Wonder if you could put two of these motors together like they do in the big slead pull tractors.

[TADracer]

Size matters ?

Size matters, but only if everything is balanced. Bore it out and put in bigger pistons and you have only given yourself the ground work for more power. To get the most out of the higher compression, larger volume and higher cylinder pressures you will need to do other things too. Alot of other things. Like re-jetting, better ignition, perhaps head porting, exhaust work and so on and so on. I have said it here before, a top performing motor is a balancing act. Upset the balance and you are setting yourself up for headaches. I am not against the big bore kits but there are better horsepower gains to be had from less costly things you can do so, why not try them first.

Here is one, for instance, try playing around with thinner head gaskets. A .010" thinner gasket can jump your compression ratio a few percent and still give adequate piston/valve clearance. The average composition head gasket will mic out at around .051" compressed. Try a .040" gasket if you can get ahold of one or places like Hussey Copper can supply gasket material and you can make your own in a few hours with modest tools (and yes, a copper gasket will perform well for street use if done right). Plus, its reversable if you dont like the performace.

If you are looking for top end power, try playing around with cam timing. You can carefully slot your sprockets with a drill press and alittle file work. Then, degree your cams in right and your power curve can be put right up into the high RPM range for absolutely no cost other than a degree wheel and a dial indicator. Reversable too.

Head porting is always a good bet and is cheap to do but cannot be reversed without changing the head. But think about what you are going to do otherwise you can screw up a good head. The early heads have alot to work with, especially on the exhaust side. The exhaust ports can be opened up approximately 30% and still leave a 1/16" lip at the pipe to prevent the reverse wave along the pipe wall from coming back up into the port. Here is another cheap trick that will produce for you, do a 30 degree back cut on your valves. Most machine shops will probably do the grind for less than $10.00 per valve. This alone can significantly increase the amount of air/fuel into the chamber. If you want to go a step further, mill the head (if you have the valve room) to add to that thinner head gasket.

All of this can be done for alot less $ and hassle than a big bore kit and will garner you a noticable increase in performance. But like I said before, it will take finding that balance again before you will be satisfied with what you have done.

[yamahansolo]

over 100 hp to the wheel is achievable with these bikes. go to youtube they dynod one with the little bigbore and head mods it had 107 to the wheel.