How much of an 82 xj motor is really xs11?

[Unclefacts]

Been thinking of doing some mods to the bike over the winter, one of which would be a big bore kit.

So I got to thinking, how much of the '82 Xj1100 engine is really xs11 parts?

[Yahman]

Everything is the same except for the XJ has a better generator. The YICS system is a junk emission system which I have a fix for and the ignition system is better.

The big bore kit will work with both the XS and the XJ1100 engine.

Larry

[Unclefacts]

As Mr. Burns would say, exxxxxxxcellent.


My plans for tire shredding nirvana will go forward.

Thanks!

[trbig]

The head and cylinders are a bit different also. The cylinders have a YICS tube attached to the back side of them and the head has the ports that attach to this tube. Won't make any difference on boring though. There's more differences between the 78-79 motors VS later 80-81 XS motors than there are between the later XS and the XJ, but everything from the piston pins down and back to the middle drive are the same in all of them.


Tod

[Unclefacts]

I see by your sig, that you have what I'm thinking of doing.

Thinking though of going to the 2nd overbore and the big kit.

Are you using stock carb bodies with a jet kit? I saw on here that the GSXR 36mm Slingshots will mount. I may go with those as there's a set for sale local. Then jet them appropriately.

Going to also have the stock heads ported/polished while it's apart as well.

Check everything on the top end while it's apart, then button it up and enjoy it.

Thanks for the info!

j

[trbig]

Thinking though of going to the 2nd overbore and the big kit.

Good idea and wish I had gone the 1196 versus the 1179. There is a difference between a 2nd overbore and the big bores that Wiseco has though.

Are you using stock carb bodies with a jet kit? I saw on here that the GSXR 36mm Slingshots will mount. I may go with those as there's a set for sale local. Then jet them appropriately.

I have stock carb bodies and stock jetting... except I went up a size on the mains. The slingshot carbs are good if you are just drag racing, but normal riding... bad idea, and a tuning nightmare so I've heard.

Going to also have the stock heads ported/polished while it's apart as well.

Another bad idea unless someone who knows these motors intimately and has a flow meter to back up this knowledge. As a general rule, with porting.. and especially polishing.. you will LOSE hp with these motors. A stock head and carbs will move more air/fuel than a 1200cc motor can draw. Even if done absolutely perfect (Which is pretty doubtfull) you're talking of spending hundreds of dollars for probably 5 hp or less.


Tod

[Unclefacts]

thanks for the heads up on the slingshots, was planning on doing some drag racing with the bike, but it has to live on the road too.

Have access to a full race shop here, wasn't aware that the ports on these heads were that big. Maybe then instead of a full port, I'll have them Extrude Honed and just port match and clean them up.

Any idea if there was a hotter cam available for these bikes? Thought there was a company called Webcam that might have at one time.

edit: Ahhah! Webcam's Page for XS11 cams.

j

[Yahman]

Dan Hodges

Do a search for Dan Hodges, he knows more about modifying these engines than probably any one else on here. Lots of good info in his threads.

Larry

[trbig]

Cleaning up all that rough casting is said to be the biggest part of the power loss. As stated, PM Dan Hodges and he'll give you some reading material. Instead of saying "Don't polish the intake" he'll give you lots of information as to his opinion of it.. lol.

I know he has had his ported and shaved. He also knows of a company that will make the pistons at the dimensions you want for about the same price as Wiseco. The 78-79 motors had lower domed pistons than the later models, but a smaller valve relief space in the head and actuallly had higher compression due to this smaller head space. Higher compression.. to a point.. is going to bump your hp numbers better/cheaper than anything besides more cc's. Wiseco pistons have a dome that is in the middle... between the higher domed later model and the lower domed early model motors. This results in a bump up in compression for the early models and a reduction in the later vs a stock motor. If you can have some pistons made to fit the 1196 bore but are the same dome as the later model pistons, you'll increase your compression and hp.

You can spend money on cams, but they aren't really going to give you any more hp.. just change the area in the rpm range where that hp is made... low end.. midrange... top end. It all depends on what you want and the stock cams are a pretty good all around cam, though some prefer a slotted cam with a 5 degree advance on the intake side.

Tod

[Unclefacts]

Spent the afternoon reading up on Dan's stuff. He sure seems to be a wealth of info. Great stuff.

thanks for the tip

[yamahansolo]

my question on the bore kits is this... if they are all the same size pistons. how then will my 79 have a 10.25 ratio and someone elses 80 with the bigger heads have a 10.25 comp. ratio??? would it be lower due to the bigger chambers?

[trbig]

Yeah, that's what I was saying. A big bore will increase the 78-79 motors VS stock, while the later motors won't reach that compression ratio due to the larger valve reliefs in the head. BUT.. the later model heads will flow better than the earlier models due to the larger valves. It's really a toss up.

What I'd like to see is a piston with the same amount of crown as the stock later pistons.. in a big bore kit. As stated, apparently you can get this with that company Dan Hodges talked about.


Tod

[Jerry]

If anyone is interested, I have a set of brand-new Venolia 11 to 1 pistons, no rings, that I bought on ebay a few years back. NOS. Stock, not oversize. Boxes are not great. $50.00 plus shipping. Venolia is still in business making replacment high-perf forged pistons for various applications. Alas, their catalog no longer lists pistons for the XS11. They used to stock rings for these pistons, don't know if they still do but you could probably match up some Perfect Circle or Hastings rings to fit. Will take photos if anyone is interested. Had thought of upping the compresion in the XJ, but 11:1 is more than I wanted.

There are a few places that make custom pistons, but last time I checked, about a year ago, the going price was around $100.00 each. Most often these are for antique or classic cars where there is no alternative source. If you search on 'custom pistons' a few different manufacturers show up.

[Unclefacts]

Ohhh if those were the oversize I was looking for, I'd be all over those.

Someone's gonna be real happy with those slugs.