Anyone build an 1100????

[Mr. Schweer]

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.

Yeah, see the problem with the second theory is that the rough surface actually causes the fuel separation. Without quoting a million different sources that prove that, I'll just say this, if rough ports help atomization, port fuel injection engines never would've made it off the drawing board since there is nowhere for the fuel to mix with the air as the fuel is injected directly at the backside of the intake valve.
End of that theory.
With regards to the evaporation thing, well, water evaporates from a smooth surface much more quickly than a porous surface, and although the fuel wouldn't get absorbed by the aluminum, the principle is the same and since the first theory doesn't hold water, then the second point is moot.
The third part is the absolute antithisis of ram-air....smooth surfaces create velocity....not bumpy factory castings. If you go down a water slide that is smooth, you will have more velocity than if you went down a water slide that is bumpy. Bumpy=friction. Friction=heat. Heat is not wanted in an intake charge.
Ram air has MORE effect at high rpm as the cylinder has LESS time to fill with the same valve lift as rpm increases.
But thanks for the info on IIRC!!!

[crazy steve]

....Polish intake and port and polish exhaust ports......

Porting can be good. The current generally agreed opinion on polishing is: intake bad, exhaust good. The reasoning behind that is the rough surface in the intake helps keep the fuel in suspension and the smooth surface in the exhaust helps prevent carbon build-up. But there's exceptions to all of this, depending on what you're trying to do. As to the idea that the rough surface makes no difference and using an EFI motor as an example, the difference is the injector does a MUCH better job of atomizing, and as it's squirted almost directly into the cylinder, doesn't have time to separate. On a carb motor and anything with a long intake tract, it does help.

As to porting, bigger isn't always better. Looking for valve shrouding and doing some light clean-up and port-matching will usually give dividends and the better equipped shadetree guys can usually do this, but just hogging them out can be a disaster. If you have a flow bench and one or two sacrificial heads, then by all means, go for it...

'78E original owner

[TopCatGr58]

Hey James,

My bad, like I said....IIRC Just reviewed the big DYNO run thread, and folks were reporting 80, 85, 90 RWHP values..these are with some "MODS", and around 60 or so Ft/lbs torque. I still think the crank rating of 95 is correct, but the RWHP values are probably closer to 70-80 for STOCK...found a thread/reply by MRO another knowledgeable Xsive and stated that it was 70 +/- 10% for RWHP!?

Some of the DYNO runs images are still in the thread, but many have disappeared due to changes in PHOTODUMP's linking policies!

I read in another thread that you're kinda tired. But I also read that this will be long time project, so you've got plenty of time to PERUSE the site, the tech tips, the forums. There is an article about making the XS11 handle better with suggestions from Progressive fork springs, etc.! Brake mods vary, but all agree the Stainless Steel braided lines are a must. You can also find aftermarket floating rotors, drilled/slotted and much less weight. Can replace OEM front MC if too messed up. Ithink it was stated getting some newer carbs, like from an FJ1100 or GXSR would also help, vs. going the FUEL INJECTION route as some have done. You also might get lucky and find a TURBO KIT, yes, they were made for these machines. One fellow who races one with a TURBO reports twisting driveshafts!

Dan Hodges is our resident Engine Hopper-Upper GURU/SENSEI, a search for his posts regarding cams, porting, big bores, etc., would be enlightening to your research. He's going thru the process of making a IIRC 1300 XS11, with custom pistons, jugs, etc.. I don't know what his expected HP results are going to be with this supermod, but I don't know IF your 150HP target is financially feasibly attainable?
T.C.

[79XS11F]

As many may know I opened up my exhaust ports a far amount after researching the topic. From what I read the average handy man can get up to 15% more air /fuel into his engine just by making sure the ports in the head match the exhaust and intake components. I didn't do anything on the intake side because the match to the carb boots is already just barely detectable with the fingers. on the exhaust side I increased the DIA by about 1/4 of an inch to get the match to the pipes. This was done on my 1179 hop up that I hope to finish soon. All I can say is that as i was told to expect the largest gains are from about 5600 to 6000 RPM to past red line. Once the RPM get to that "sweet" spot the bike will nearly rip your arm off.The first time I gave her a good twist I came very close to going off the back of the seat. I therefore think that opening up the ports is worth it unless you intend to go touring.
Rob

[trbig]

Why would the Yamaha XS11 head/engine be that different from any other head in the world that DOES flow better with smooth ports??

Just telling you what I've read on here and in MANY many articles on the XS engine while doing my rebuild and bore on mine. I am, by far, no expert. But I will say... just about every other motor out there runs better with less restrictive exhaust. Open headers works GREAT! Dual exhaust outperforms single exhaust hands down, right? Then why do 4 into 1 pipes make the most performance on these bikes?

As stated, the casting marks, as I have come to understand, do help atomize the fuel. These stock Mikuni carbs matched to these stock intake ports will move far more air/fuel than these bikes can possibly consume, even at the 1196cc setup. You can also do some searching and reading of how adding material by welding to the bottom of the ports and making them into somewhat of a "D" or heart shape, (which would actually be closing off the port some,) if done properly will gain big increases in H/P.

Alot of the stuff goes against the conventional way of thinking.

Tod

[psycoreefer]

Yeah, see the problem with the second theory is ..... port fuel injection engines never would've made it off the drawing board since there is nowhere for the fuel to mix with the air as the fuel is injected directly at the backside of the intake valve.
End of that theory.

The third part is the absolute antithisis of ram-air....smooth surfaces create velocity....not bumpy factory castings. If you go down a water slide that is smooth, you will have more velocity than if you went down a water slide that is bumpy. Bumpy=friction. Friction=heat. Heat is not wanted in an intake charge.
Ram air has MORE effect at high rpm as the cylinder has LESS time to fill with the same valve lift as rpm increases.
But thanks for the info on IIRC!!!

As was pointed out you can't compare fuel injection to carbs, to many differences. Some folks have gone to fuel injection, do a search....

Second the velocity isn't created by the rough surface, I should have been more clear. You lose velocity with a port an polish because you've increased the size of the ports not because of the surface. Larger ports = less velocity. Its a law of fluid dynamics or something.

Next there needs to be some discussion on what we mean by more power, sure you might gain a few peak hp with this or that mod but you lose a little in other areas. If the bike is going to be ridden on the street you'll have a lot more fun on a bike with a great big flat power band then one with twice as much power and a sharp peak with little power on either side, but if you've been building cars you probably already know that.

The only way to really figure out what works best on these motors is to get multiple heads, do each one up a little different and then swap them out on the same motor and do dyno runs. If you want to do that I suspect you'll make a lot of friends here, otherwise all you can do is read and make your own decisions and then post your results for others to use.

[Mr. Schweer]

NOW we're talking......these last few posts were what I was looking for....thank you Tod for clarification as well as the rest of the guys chiming in.
I went back and re-read my thread and I want to apologize if I came off as a dick. I really wasn't intending to sound so rude. I'm just kinda used to idiots on the Corvette forum simply being naysayers to everything out there and each one of them being an expert on everything while actually knowing nothing!!
A couple of the replies were short statements with no explainations which caused me CF flashbacks

[Mr. Schweer]

So I'm thinking that simply port matching the intake, and porting (which looks like I will be removing mucho material to match the head-pipes) and polishing the exhaust will be the best way to go. Like I said, I'm not looking for huge power numbers, only about a 50% increase with a the most area under the torque curve I can get.
Custom pistons only run about $125-150 each and I can do the porting myself and slap the head on my buddies superflow flow bench.

Now, I need to know if anyone has stock flow numbers and whether or not the stock cylinders can be bored?? If so, I can save money on new cylinders. I'll most likely be looking for used parts if available.

[Pat Kelly]

In an intake or exhaust runner, a rough surface creates turbulance along it surface... almost like a 'virtual' bearing surface. A smooth surface will allow the fuel to cling to the surface.
As the piston moves up and down it displaces a set volume of air. A large diameter port or runner will allow more volume to pass through (less velocity or speed of the air) untill it allows more air than the piston can move. A smaller diameter port or runner allows more air velocity or speed until it begins to choke or restrict the airflow.
One can clean-up the casting surfaces of the ports, remove sharp edges and bumps but it takes experience to do it right or even well.
In the long run are you skillful enough of a rider to utilize 100% of the engine's capability? I've been riding over 30 years and used to roadrace in the late 70/early 80's. A stock XS1100 has plenty of power and will never be able to handle as well as a newer bike.

[Mr. Schweer]

I really am not concerned with the handling capabilities of these frames or suspensions. I am looking to build some power. I am going to go straight. Handling doesn't really matter when I rip the throttle and tear down the road going straight. If I wanted an ugly plastic fantastic bike I woulda bought one.

So just for all future clarification, I am going to build the bike I want. If that means that I build a full-tilt race engine with monster cams, huge custom pistons two 450cfm holley's running nitro and a 250 shot on the jug, I will. I don't give a crap about handling.

I HAVE a beautiful almost perfect essentially stock '79 XS11 special for zipping around curvy roads and using up all 95 hp.

Please, no more nay-saying or pissing on my parade.

Thanks,

James

Oh yeah, I know how to build an engine, port heads, set up suspensions (drag or autoX) and play with my own nuts. I don't want to get into pissing contests about who knows what porting does or doesn't do. I am only asking for pointers from people who have built these bitchen engines since I have yet to do one of these. If you don't have any positive input for this thread, please refrain.

[Bigfoot]

Dude, please chill out a little. The guys were just trying to answer your questions and giving you their honest opinion as to the effects of porting and polishing the engine. Obviously you are set on doing it anyway but I did not see anyone

pissing on your parade.

[Pat Kelly]

I wasn't telling what to do with your bike or how to do it.
I will refrain from replying to your post(s) as you seem to already know it all.

[crazy steve]

...Like I said, I'm not looking for huge power numbers, only about a 50% increase with a the most area under the torque curve I can get.

If you can get a 50% power increase without spending the cost of a new bike or building a grenade, you'll make LOTS of new friends here!!! LOL!!

'78E original owner

[trbig]

Something I have considered.. and you might look into, since it's really doubtfull you can get a 50% increase in power. That is a HUGE number for a pretty tricked out motor for it's day already. (Yeah I know.. your parade is getting wet again.. it'll dry... get over it.) Probably the cheapest way would be to install a turbo. BUT... what I have considered.. is running an XJ head on XS cylinders, there are YICS ports exposed behid the fins. NOS jets would tap right into these. These ports lead to directly in front of the intake valve. A few members have turboed these bikes, but I've never heard of a NOS setup. Might be areason though.. lol.

These cylinders can be safely bored for the 1196 kit, but there are also, as stated about Dan Hodges' post, that you can purchase even bigger cylinders to drop into the block.. you just have to have the aluminum bored so they will fit. Dan is currently building something in the 1300cc range. There's also a racing head you can get that has 4 valves per cylinder if you have the cash. Again, Dan Hodges is the one to ask about that. He's been building go-fast things with motors his whole life.


Tod

[Mr. Schweer]

Geez guys. Didn't say I know it all and I am chill. My thread asked if anyone has built an XS11. So far I've gotten one reply from someone who's actually done engine mods. The only other posts with any info I could use are from T.C. and Tod. The rest of the posts seem to be opinion. If head porting works, great. If not, fine. But if I get a "porting sucks" type of post, I would like to know why. And not just someone theory on head porting but why it actually doesn't work and if someones got actual firsthand knowledge.....AWESOME! I can't get 150hp fine. But why??? Please give input.