Anyone build an 1100????

[Mr. Schweer]

So I recently bought a 78 XS for the pricey sum of $175 and I'm going to be building a cafe racer style bike out of it. I've always built big cube, big power engines for my cars, but this will be my first bike engine build.
Since this is the place to be as far as getting first rate XS info, I have a few questions:
1. Has anyone here done a big bore kit on there bike?
2. Are there any good after market cams available?
3. Does anyone have any chassis-dyno numbers for stock 1100?
4. Does anyone have any chassis-dyno numbers for a 'built' 1100 or 1200?

I'm not in a big rush, my son and I are going to be building this as a project for the next couple of years and it only takes a few hours to actually build the bike, (A few hours per segment of bike that is....engine, carbs, electrical, steering rack, etc.) so getting the right parts, info and advice are the most important and time consuming parts of the job.

TIA,

James

[79XS11F]

You should be able to find lots of info on all you question on the forum.
Many have modified these bikes with ether the 1179 or 1196 kits.
Cams are available from a few sources.
Dyno test results are on here in some threads for those who have had tests done.

Rob

[thewiz]

Mr Schweer ...

Search for posts by member 'Dan Hodges' .... he is down with some VERY heady discussion on how to squeeze the most juice out of one of these motors.

Member 'Tadracer' has offer some good performance info as well, IIRC.

[TopCatGr58]

Hey there James,

A few questions are what will you be using the bike for when it's built? And how much $$ do you want to put into this project? Regrettably, unlike the cars you've built where there are hundreds of aftermarket suppliers, and parts, the XS11 is 25+ y/o, was only made a few years, and it's parts and manufacturers are getting more rare every year! ie. Jardine which made the better quality and performing exhausts for our machines dropped them last year, so there's only MAC, or some others in UK or such, and much more $$!

The stock engine puts out decent power, IIRC 65 bhp at the rear wheel, 95 at the crank, but you should be able to find the absolute specs in the tech tips or misc forum. Due to non-availabilty of standard oversized pistons and rings, IF the engine mics out of spec, a big bore kit is the only solution to get a clean cylinder/bore. The big bore kits provide a decent increase in power/performance with modest $$ investment. You have the earliest model XS with the hottest specs for cam, it was the fastest of the model years before they started getting detuned due to EPA and such!

But as you know, the more radical of changes and increases in power, the less reliable and durable the engine can become. Folks have reported putting over 100K miles on these stock engines, unheard of for most motorcycles of this era or later.

Another MOD to get more of the HP to the rear wheel is the Chain Drive conversion, see XSCHops thread for this, which can also enable the use of a much wider rear tire/rim since you won't have the restriction of the driveshaft and swingarm tunnel.

So...lots of "stuff" can be done, but how much MORE power you would get vs. a relatively stock engine and whether it would be worth the $$ is up to you! Perhaps you could try to contact a member close to you that could either take you for a ride, or even let you ride/pilot their XS11 to let you feel how a stock one feels? Whatever you decide, don't forget to post lots of pictures!

[fredintoon]

Hi James,
you gotta love the XS11, warts and all. Thing is, the XS11's handling and brakes are already marginal with the engine left in it's stock state. Unless you upgrade the handling and brakes to match any power boost you build into the engine you will be building a real widow-maker.

[Steptoe]

B.h.p

Hey T.C,you just made my day, my old girl before the work over was 89, haven,t had the chance to test it since,IIRC she now has 74mm pots. I am pretty gullible, I was told it is now 1188cc

[tw1980]

To answer your first question yes.Two Wiesco kits available 1179 and 1197cc 10 1/2-1.Megacycle will regrind your cams to specs from stock to drag race only and all points in between.Dynojet doesn't make carb kits for a 78 but cr carbs are available.Head can be shaved ever so slightly.Polish intake and port and polish exhaust ports.Hotter ing coils can be found from Accel or at Mikesxs.Pod air filters and Jardine exhaust.That's a list of the engine mods I've done to my 80 special.I'm very happy with the performance but I've never had it on a dyno.Warning!!The amount of $$ spent on this I could have easily purchased a nice sport bike or a vmax.Yes I know building it is half the fun but I wanted you to be aware of the expense.Have fun and keep us posted.Terry

[T99Ford]

Were these bikes really only rated at 65 BHP at the wheel? I am getting right at 80 (from a dyno jet dyno) at 5500 ft. with only minimal mods. If I care to sacrifice fuel economy, I think I can jet to about 84-5 HP. My pipe is my own custom, but that is the only serious mod I have done besides jetting. The airbox is also gone. I though my dyno results were pretty average.

[trbig]

Polish intake and port and polish exhaust ports...

... actually makes you LOSE power. Intake runs better with the rough casting, and the chances of you porting the exhaust right without it being on a flow meter are slim to none. Actually ADDING material to your intake to make somewhat of a "D" shape with the higher portion to the bottom will increase HP... but again, not without someone who knows what they're doing and has a flow meter. Better stick with the other mods mentioned.



Cam sprockets can be slotted to degree the intake, or I think Weber makes a hotter aftermarket. As mentioned.. you can buy a faster bike cheaper than you can make this one faster. To get things right, it's going to be hit and miss, and the only real way to know is with lots of Dyno runs.. which is lots more money.


Tod

[WMarshy]

... actually makes you LOSE power. Intake runs better with the rough casting, and the chances of you porting the exhaust right without it being on a flow meter are slim to none. Tod

I heard acid porting leaves that casting texture... Anyone ever heard/used it?

[CatatonicBug]

I heard acid porting leaves that casting texture... Anyone ever heard/used it?

Never actually tried it for that purpose, but I know that Muriatic acid EATS aluminum (won't touch steel) very quickly. It looks like Hydrogen Peroxide on a skinned knee! I imagine that a few dabs of the stuff on any aluminum part would severely etch the surface, and FAST!

[Mr. Schweer]

... actually makes you LOSE power. Intake runs better with the rough casting, and the chances of you porting the exhaust right without it being on a flow meter are slim to none. Actually ADDING material to your intake to make somewhat of a "D" shape with the higher portion to the bottom will increase HP... but again, not without someone who knows what they're doing and has a flow meter. Better stick with the other mods mentioned.



Cam sprockets can be slotted to degree the intake, or I think Weber makes a hotter aftermarket. As mentioned.. you can buy a faster bike cheaper than you can make this one faster. To get things right, it's going to be hit and miss, and the only real way to know is with lots of Dyno runs.. which is lots more money.


Tod

Okay, now that is one of the most um, how should I put it, well, absurd things I've ever heard. I could be wrong, so if you have some empirical data or info from a head porter I would be interested in reading up on it. Why would the Yamaha XS11 head/engine be that different from any other head in the world that DOES flow better with smooth ports?? Do you KNOW this or is it anecdotal? I really am not being rude or a smarta** here, but if you know something about head porting that I don't......I really need to know. And yes, I have ported heads, and yes, I've had them flowed, and yes I've had heads ported professionally with a flow-bench so I do know what I'm talking about. In fact one of my clients (I own an insurance agency) owns a company (which I insure) called Air Flow Performance.

[Mr. Schweer]

NOOB question here.....what does IIRC mean?? I think I've picked up on most of the other acronyms here but this one I can't get.

[Mr. Schweer]

Thanks for the responses guys....good insight which is exactly what I'm looking for. T.C., the main use is going to be 'joy-riding' my son will be using it for short commutes to school so mileage isn't going to be too much of an issue. I'm thinking that if I can squeeze a total of 140-145chp I'll be happy. What I'm trying to learn is whether or not that is reasonable without sacrificing streetablity as you noted. Is that 65whp factory rating correct?? I can't imagine there being a 69% parasitic loss with a manual trans, short driveline, direct-couple and single tire. On my last real mild build, I built a Pontiac 455, 462cid for my '71 Trans-Am and the engine dyno'd at 400hp. The car chassis-dyno'd at 304hp. That's roughly a 75% loss but that was with power steering, high amp alt. automatic trans with a 3K stall, heavy spicer u-joints, very high gears (3.08), posi and heavy drag radials. In a 3500lb car.
Fredintoon, is there anything other than the tkat brace that I can do for handling?? This particular bike won't be tearing through the twisties to much, at least not where the extra power will be needed, but I would like to stiffen up my '79 a bit. What about brakes?? Are there any good replacement alternatives to stock. I know I can make my own braking system with parts from other bikes, but I'd rather upgrade the stock system. Do the later year disc's just swap on. I believe the later years (80-82) have slotted rotors. Could I just get a set and slap them on or do I need different calipers?

[psycoreefer]

IIRC = if I remember correctly

As for porting there are several trains of thought I've read.

1. Porting/polishing is good, more flow = more power, smother larger bores flow more and therefore produce more power. This is true if the head can't flow enough air for the motor, or if your running very high RPM's a lot.

2. Porting/polishing is bad, more flow doesn't always = more power. Carbs aren't as good at atomizing fuel and the rough casting provides two benefits. First it creates boundary turbulence causing the fuel to stay suspended in the air. Second it is a better surface for the fuel to evaporate off of if it does come out of the air. Second it creates more air velocity which tends to "ram" air into the cylinder during the time between when the piston reaches bottom and when the intake valve closes. This effect is less noticeable at higher RPM's.

It's been reported that our carbs can flow way more then the engine can use, and the later heads with larger valves are supposed to have more top end so the 2nd theory has some anecdotal evidence if nothing else.