Planning 1980 xs1100 big bore project

[greengoon3]

I am setting up to do a big bore project on my XS1100 special.

I am thinking of getting a spare set of jugs that I can send to the machine shop for boring and honing.

First question are all xs1100 jugs the same for 78-81 years?

I see a kit on fleabay for $150.00 + shipping for the big bore kit.

I am doing the extra jugs thing so I can still ride what I got going now.

I do plan on replacing the cam chain and guides while I'm in there.

I've already upgraded to the auto cam chain tensioner

Any thing else I need to do or be aware of?

Any suggestions, ideas or worries?



Thanks in advance!
George

[crazy steve]

Yep, any XS cylinders will work, even XJ although those will have some 'extra' holes that won't be used. Other than that, the only thing I would look at would be maybe installing the '78-79 cams as they have more duration (although slightly less lift on the exhaust valves) which would help with cylinder fill (and a bit more poop on the top end ).

[TopCatGr58]

Hey there George,

Folks will be interested in seeing this project come to fruition. We all have seen the big bore kits on Ebay for $150.00, they are cast pistons instead of forged hence their cheaper price vs. Wiseco! But they are made in Japan, so we expect them to be of good quality.

How many miles are on your bike/engine now? When I did my rebuild/bigbore kit I estimated that I had about 50K miles, and the bike had been running well before I parked it and let it get rusted...so I felt the BOTTOM END was still in good shape. Folks have commented on their engines going for 100K miles or more, and with the large bearings, they last a long time! I didn't even split the cases or plastigauge the crank, just pulled the jugs, had them bored and put the new pistons in with a head treatment..lapped valves and seals.

I recommend the McBride Motorcycle racing machine shop(Cycle Specialists did mine)
http://www.larrymcbride.com/
on 11115 Jefferson Ave near main street N.N. to peform your boring...you'll need to bring the pistons with you so they can match them to the holes!!! They will also taper cut the bottom of the bore to make fitting the jugs back on the pistons if it's not already tapered.

That's all I can think of for now.

T.C.

[natemoen]

Yep, any XS cylinders will work, even XJ although those will have some 'extra' holes that won't be used. Other than that, the only thing I would look at would be maybe installing the '78-79 cams as they have more duration (although slightly less lift on the exhaust valves) which would help with cylinder fill (and a bit more poop on the top end ).

Just to clarify, only the XJ11 not the smaller XJ bikes. All the XJ's were 4 cylinders though.

[WMarshy]

I am setting up to do a big bore project on my XS1100 special.

I am thinking of getting a spare set of jugs that I can send to the machine shop for boring and honing.

First question are all xs1100 jugs the same for 78-81 years?

I see a kit on fleabay for $150.00 + shipping for the big bore kit.

I am doing the extra jugs thing so I can still ride what I got going now.

I do plan on replacing the cam chain and guides while I'm in there.

I've already upgraded to the auto cam chain tensioner

Any thing else I need to do or be aware of?

Any suggestions, ideas or worries?



Thanks in advance!
George

I bought one of the BB kits for $150... I posted pictures of them some where on the fourm if you cared to see some close up pictures...

JAT another member was going to use the same kit but with the earlier head (78-79) and I believe he was planning on claying the piston domes to verify valve clearances. I cant remember who that was but it's a good idea to do with the earlier head because those pistons were made in reference to the later (80+) engines...

[GLoweVA]

Hey George, welcome to another tidewater XSive!

I too am thinking about the $150 big bore to 'fix' my SG's holey pistons.
Right now I'm in the process of an engine swap. (Thanks again TC)
Now that there's another one of us XSives here in Hampton Roads, we really need to ALL get together at least for a group photo or something.

[Bonz]

I'm watching this with great interest... Have an 80G I just got on the road, nothing wrong with the engine but might be a good candidate to find a set of jugs to bore and do a swap out for the heck of it at some point in the future.

To my mind, a big bore is the ticket to boosting the low end/mid range. With respect to our beloved XS's, they don't have a lot of beans below 3k rpm. Back in the day it was even noted the engine woke up above 3k rpm by the testing media. I will agree with them as well.

Nothing like some cubic inches to add some grunt. All things equal, you will gain a few hp along the way simply because of more torque at any given rpm.

I have noted most guys don't feel there is a lot to gain with the big bore kit, but simple physics says it will add some torque that should be noticeable.

[GLoweVA]

I once had a chance to ride TC's 'Zilla (he's got the wiseco kit) and it was DIFFERENT! Noticable? Hell Yeah.
That ride was the reason why I'm even considering this as a fix to my holey pistons.
Being on a budget like most of us here, I was just going to replace those 2 pistons with 2 used ones and re-ring all 4 and go, but since time isn't really an issue because I've got the donor engine going in and the cost of this kit isn't way out there, why not. (maybe spread the $pain$ out over several paychecks. LOL)

So, I am also watching how this goes. Oh, and he's local too, so I may get eyes on instead of just seeing pics here.

[greengoon3]

I figure the bike has around 50,000 miles or so I have replaced the speedometer twice since I've had the bike (6 years or so).

Great machine runs really well. Just looking for a little more. Like the old saying "there is no replacement for displacement".

Since I added an additional clutch plate, new springs, and converted to a hydraulic clutch. My clutch never slips anymore. So I figure now is the time to add a little extra horsepower.

TC's oil filter adapter really made changing the oil easier and a lot less messy, and I feel I need to do more modifications to set my bike apart from the others.

I ride to and from work @ Newport News Round Trip ~ 74 miles.

I rounded up the materials required to change over the rear drive, however I couldn't make myself sacrifice the low end torque.

[Bonz]

Good stuff!

Don't think twice about changing the final drive to the 750/850 mod.

1) I can get through the intersection without changing gears
2) Gained an mpg or two
3) 400 rpm lower at 60 mph is a REAL nice rpm drop, even more rpm drop at higher road speeds.
4) I wouldn't hesitate to run the 750/850 FD with the BIG BORE as I don't ride it like I stole it, but the 850 FD has been shown to be the stronger of the two, so I would go with one of them.

[GLoweVA]

I ride to and from work @ Newport News Round Trip ~ 74 miles.

So, you take the MMBT every day whereas I take the HRBT. My commute is 29-30 miles to NN Shipyard from Va Bch Towne Center.

Occasionally, I'll take the longer way around and do the MMBT, I sure do like the smoother roads on that side of town. Norfolk and Va Bch's interstates SUCK!

The FD conversion may be an option for me, but I'm currently getting about 34 mpg with the monster and I'm happy about that.

[Schming]

Great machine runs really well. Just looking for a little more. Like the old saying "there is no replacement for displacement".

.... I feel I need to do more modifications to set my bike apart from the others.



....I rounded up the materials required to change over the rear drive, however I couldn't make myself sacrifice the low end torque.

These couple statements are the reason most of us have more than one Eleven in our stables.

Welcome to the Sickness

[trbig]

Yep, any XS cylinders will work, even XJ although those will have some 'extra' holes that won't be used. Other than that, the only thing I would look at would be maybe installing the '78-79 cams as they have more duration (although slightly less lift on the exhaust valves) which would help with cylinder fill (and a bit more poop on the top end ).

Not sure about the timing setup on the 80, but an '81 or '82 (XJ) where the timing is pretty close between those two years, the early model cams are a mistake. I ran them quite a while in my bike, not knowing what I was missing. When I bought the XJ, it had a '78 motor in it. After I spun a crank bearing and put another XJ motor in, I used the cams from the '78 motor because people said it'd make a hotter bike. It ran good on the top end, but it wasn't any faster than others I rode with, but it was an absolute gutless pig on takeoff. Another big issue is trying to adjust them. When you hook up a set of gauges to synch them, it shows almost ZERO vacuum.. like 1-2 Mb due to the timing. There was just no way to synch the carbs with readings like that. I ended up putting in the right cams and WOW.. talk about waking up a motor with vacuum to boot for adjustments. The only way the early cams would work in the later motors is if you swapped all the timing and TCI from a 78/79 motor (Insane to go from electronic to mechanical) OR.. as mentioned, run the complete 78/79 head on the late motor. I wish someone would do this after checking the piston to valve distance. I've always wondered about it.

For those of you thinking of doing the big bore for more HP.. you will be quite disappointed. The only thing you'll have is a fresh engine over a worn out one. If you've got a good strong motor and bore it simply for the HP, you'll never feel it in the seat-of-the-pants dyno. An actual dyno run may show one or two more horses.. but it's nothing you or I will feel. If that is your reasoning for it, it's a waste of money. A good tuning will give you FAR more HP back than a rebuild.

If you choose to bore, DO NOT go that far into a rebuild without replacing the crank bearings. Rod bearings almost never go bad. You can plastigauge them to make sure, but I doubt you'll need new ones there unless you just never change your oil. Also, new valve seals and a valve grind would be very beneficial.

[Bonz]

trbig,

Good info, thanks for sharing it. What you said about the cams/timing has been talked about over the years on the forum, good refresher you gave.

I didn't catch if you have done a big bore and ridden one? There is really no way to not gain some torque down low with bigger jugs, even doing no other changes. Going to an 1196 is 8% gain in displacement.

I haven't seen a dyno chart, and no one seems to have one for an 1196. But I just can't see not getting a gain that you can feel. That is a kin to saying the XS defies the laws of physics in this respect.

I can take a ZRX 1200, go from 1164 cc to 1224cc and gain a crap load of torque down low and in the mid range with no other changes. It's physics. There are more dyno charts with different motor combinations than you can believe on that forum, and they all bear this out. More displacement is more power, even if it's just down low and the top end doesn't gain much when it's only a piston up-size.

Then you start adding a bit of compression and ZZR 1200 cams, holy crap... You've got liter bike power in the ZRX with monster torque in bike that is easier to ride than a moped.

Ok, that's not what this thread is about, just like to toot the ZRX horn once in awhile as I think of it as my modern XS without a shaft drive.

Anyway, hope someone comes out the woodwork with an actual dyno chart that bears out this "no real gain" with 8% more displacement...

[crazy steve]

It's interesting that Tod had poor performance with the early cams, but does illustrate that the relationship between displacement, valve timing, and ignition timing can be critical for best performance.

With a displacement increase, you have to get more air/fuel into the motor to see a meaningful increase. And the effects of cam duration will usually be less noticeable as displacement goes up, as mixture velocity will go up too. But if you don't change the ignition timing to take advantage of all this, much of this power will be lost. Generally speaking, more air-fuel in, you need to start the ignition 'burn' sooner so as to have enough time to burn all the fuel. More initial timing will help, as will a more aggressive 'curve', but max timing usually can't be increased much or at all because of mechanical limits.

The non-adjustable XJ ignition simply can't be 'tuned' for a non-stock combination (well, you might be able to dial in a bit more initial advance by modding the backplate, but not being able to limit max advance may cause serious issues) so little or no power gain is understandable.

One idea I want to try on my 'modder' '78 is a more aggressive ignition curve. The '80 mechanical advance comes in sooner/faster but has too much max advance if using 10 degrees initial timing. If I can take 5 degrees out of the total curve (by moddng the limit slots on the backplate), this may give me a big boost in the midrange. Down the road a ways, but I'll post results when I do....