questions on a big bore kit??

[1fasttrucker]

hay guys any body give me any imput on a big bore kit for my bike,I run back and forth to work , back roads tooling on the weekend , and like to let hang out and twist the throttle a bit to much, but mostly slower and easyer,
is there any problems with cooling and over heating during city riding ? I know an oil cooler would help!! just looking for some input !! thanks

[airborneXS]

let me know what you find out. when i get my R1 back up and running, i want to tear the xs down and rebuild the motor and tranny....might as well throw some power at it as well...

[1fasttrucker]

no problem

let me know what you find out. when i get my R1 back up and running, i want to tear the xs down and rebuild the motor and tranny....might as well throw some power at it as well...

I will let you know what I learn !!

[airborneXS]

i appreciate it...i was just thinking this same thought this morning...scary...lol

[DGXSER]

There are a few folks here who have the big bore kits installed. I know TRBig and TC have done them IIRC. Never heard anything about overheating or any other issues.

[crazy steve]

You better get a big-bore kit while you can as Wiseco has announced that they going to quit producing them shortly....

And don't expect a big power gain, as the cam/head limitations keep gains down in the single digit area....

[1fasttrucker]

Single digit wow

I would have thought maybe 10 hp , there is a place on the web u can get different cams for the Xs 1100 all to gether if I figured a little over a $1000 dollars , I think I will yay leave her stock and use the grand toward a fast bike from the factory, V Max Maybe !!

[natemoen]

I would have thought maybe 10 hp , there is a place on the web u can get different cams for the Xs 1100 all to gether if I figured a little over a $1000 dollars , I think I will yay leave her stock and use the grand toward a fast bike from the factory, V Max Maybe !!

HAHA!

Maybe a grand for just the big bore and the machine work required! Add another 3-500 for the custom ground cams!

[Rasputin]

I know next to nothing on this subject except for one thing. I have a set of Russ Collins pistons here minus one ring. The jugs they came out of was heat checked quite severely. The pistons etc look brand new. The jugs looked like old weather checked tires. That could have been anything from idling to long without a fan to cool while setting the carbs to who knows what.
The pistons I have here mic out at 74mm so I am not sure what the total displacement would be but I think it is like 1204 or something close to that. Too bad I did not have that one ring as I would love to find out.

[WMarshy]

Does anyone have a source for the custom cams?

[bikerphil]

Does anyone have a source for the custom cams?

http://www.megacyclecams.com/

They list the XS11, never used them myself, these bikes make enough power the way they are.

[jetmechmarty]

If you are increasing compression to 10.25/1 on a later bike, I would think I'd be able to feel the gain in the seat of my pants.

[BA80]

Just throwing this out there for y'all.

The horspower gain with a the "big bore kit" is really insignificant. After all, all your talking about is a few mm larger bore. The oversize pistons are meant to repair worn engines with tapered cylinders. Not really to make more horsepower.

As far as changing the cams, if you change the cams plan on changing carb setups, timing curves, exhaust, ect, ect.

You can't just change ONE thing and expect performance.

Just a word to the wise from an old fart that's been doing engine work for...........GEEZE!.........decades.

[BA80]

If you are increasing compression to 10.25/1 on a later bike, I would think I'd be able to feel the gain in the seat of my pants.

You want to increase HP on an SG? Just drop in an earlier engine. That's what I did.

If you really want to tear into it, get an early head, 78-79 (2H7) and stick it on that engine. That will increase your compression right there. The 3J6 pistons have a higher dome than the 2H7 and the 2H7 head has a smaller combustion chamber. The 78 head would run best I would think but whichever you use you'll need to keep the cams that go with the head.

With that head and cams you will need the centrifugal and vacuum advance units that match to get the proper timing curve to run with those cams.

It might run OK with the newer carbs but I would run the earier ones because the ar much more adjustable. I was running those even when I still had the 3J6 in mine.

I can bet you that tuned properly that setup would be awsome.


That my friends is low dollar horspower increase. You can probably get that done for less than the big bore kit and have a larger horspower increase to boot.

[TopCatGr58]

Rasputin,

My little big bore kit had the 74mm pistons...OEM is 72.5 IIRC, the 74 gives you 1179, the 75mm gives you 1196cc/s. Dan Hodges has done a lot of work on trying to squeeze as much HP from the XS11 engine, multiple types of cam swaps, etc..

My bike is an 81Sh, so it has the more roomier piston chamber and larger valves. The stock compression values are supposed to be 142 +/- 10 % at sea level which is where I'm at. After I did my big bore, broke the engine in, stock cams, I measured my compression at ~180psi across, and I'm sure I didn't have much carbon buildup, this was only 500 to 1000 miles after my topend re-breakin.

I got my bike NEW, rode it for 9 years, tranny crapped out, parked it for 9 years, got all rusted, but didn't have the braintrust of XS11.com at that time so didn't know that I could have possibly gotten the engine running okay with the rust being scraped by reseating the rings..so I rebuilt it with a big bore.

I also put on Indy filters, had the same 4-1 pipes I had before the rebuild, put on new high output coils. It does seem stronger than it was stock, but my dyno run wasn't very impressive, others with well tuned 78's have posted better numbers!

The 74mm's don't make the cylinder walls too thin, I've only had one issue of overheating but it was extreme stop and stop/crawl traffic, I don't run an oil cooler, we get 95+temps here in the summer. I can't speak for the 1196 kit.

SO...as has been said, if your engine is running well, good comp, best to just tune it as well as you can, maybe put on high output coils, and just enjoy what you have and save your $$.

I would like to see a set of dyno results of a bike with driveshaft, and then same bike/engine after the chain drive mod has been done..I think you might actually see more of an increase in power to the wheel with the chain drive than the big bore!?

T.C.