Time to make the Keeper

[BA80]

How well will the newer head, valves and cam work with the older TCI, vac advance and timing?

Would there be any sacrifice in power and mpg or can it still be tuned properly?

That's a good point. Missed that one.

The TCI will be OK, the 2H7 TCI was used up through 80. But, with the later cams it would need the later centrifugal unit. I don't think the vacuum unit will really make that much difference as to what year.

http://www.xs11.com/forum/showthread...erchange+guide

[Bartman]

I got the swing arm off and the motor and frame are laying on the right side on an old sofa cushion covered with plastic.

So HOW do you get the 4 U-joints off! I guess you are to loosen them when the bike is sitting on the tires, not when there is no weight on it.

Motor is loose, but I will use the tractor and boom to pick it up and put on a table. Thanks Kurt for the offer but you don't live right next door!

[kboehringer]

U Joint Bolts...

..... So HOW do you get the 4 U-joints off! I guess you are to loosen them when the bike is sitting on the tires, not when there is no weight on it. ....!

Bart,
I had the EXACT SAME issue with one of my XS11's. I will try to explain what I did......

I believe the nuts are 13mm? I used two 13mm (?) combination wrenches. I pulled tighter on one bolt and in the loosening direction with another. Inevitably the "Loosening Wrench" won. Worked great until I was left with one still rock hard. I then worked a couple back & forth until I finally got 'em all in a loose condition... Once that initial 35+ year torque was broken loose on all the bolts it wasn't too hard to get 'em un-done.

Because of the very tight fit I had to use a crows foot to re-set the torque during assembly.

KURT

[TopCatGr58]

Hey Kurt,

Thanks for the explanation of the grenaded engine. Yep, redneck engineering of the oil supply system to "try" to add an oil cooler sounds like a recipe for frying bearings and such!

IIRC, once I got several of the bolts loosened, I was able to place a pry bar or such between/amongst the loosened but not removed bolts to allow leverage against the last bolt.

Greg, I doubt that there will be much loss in power with the early TCI timing curves vs. the XJ's. The cams and valves timing are matched in the XJ engine. The ignition timing is similar. Remember, folks have reported using the 81 TCI which ONLY has the cent. adv. curves programmed into it on an XJ, and it had all of the power it can create just like the 81 XS. It just looses the FUEL SAVINGs advance of the vacuum pot since the XJ uses an electronic Vac. sensor to control the vac. adv. curves that are also programmed into the XJ's TCI.

With the earlier XS's mechanical cent. and vac. adv. devices transplanted onto the XJ engine, the XJ engine should perform just fine and also provide the fuel savings affect with the vac. adv.. The POWER curves are provided mostly by the CENT. adv. curves up to the max 35 degrees advance which has been set as the max adv. under strong throttle/load for the best power timing. The vac. adv. actually retards the timing from the max of 52 degrees under cruising rpm back to the 35degrees when the throttle is opened for POWER/ACCELERATION.

T.C.

[Bartman]

It looks like the number 3 exhaust valve came loose and ran lean until it burned a hole in the piston.

I took the stator off and then turned the motor over with a wrench and all four pistons go up and down, not locked up at all. But something blew a hole out the crankcase, it might be the remains of the exhaust valve.

I was able to put a wrench on the u-joint bolt and rotated it until the wrench rested on the back of the motor then I could break the other bolts loose.

[Bartman]

I am amazed at the amount of oil still in the motor after draining or is it just the size of mess a little bit of oil can make.

Cleaned the basement up and put cat litter down and swept into a neat three foot area. Go out to get some firewood and comeback and of course my five year old granddaughter has been running and playing in the cat litter!

[BA80]

Hey Kurt,


Greg, I doubt that there will be much loss in power with the early TCI timing curves vs. the XJ's. The cams and valves timing are matched in the XJ engine. The ignition timing is similar. Remember, folks have reported using the 81 TCI which ONLY has the cent. adv. curves programmed into it on an XJ, and it had all of the power it can create just like the 81 XS. It just looses the FUEL SAVINGs advance of the vacuum pot since the XJ uses an electronic Vac. sensor to control the vac. adv. curves that are also programmed into the XJ's TCI.

With the earlier XS's mechanical cent. and vac. adv. devices transplanted onto the XJ engine, the XJ engine should perform just fine and also provide the fuel savings affect with the vac. adv.. The POWER curves are provided mostly by the CENT. adv. curves up to the max 35 degrees advance which has been set as the max adv. under strong throttle/load for the best power timing. The vac. adv. actually retards the timing from the max of 52 degrees under cruising rpm back to the 35degrees when the throttle is opened for POWER/ACCELERATION.

T.C.

The ignition timing curves will be quite different because of the different grinds of the cams. The older engines (cams have a longer duration) need a much faster mechanical advance. The 78 ( the quickest engines in my opinion) has a base timing setting 5 degrees more advanced than the later engines. The 79 has the same cams but the centrifugal unit goes full advance much quicker.

The later engines have a shorter duration cam but a higher lift ( Thanks Ralph Nader) for emissions purposes. It has a slower mechanical advance but smoother power through all RPM ranges and because of the shorter duration cams a smoother idle.

Others that have mixed and matched cams and timing components have had performance issues.

[MaximPhil]

Hi Greg,
Thanks for the explanation of the differences.
Phil

[crazy steve]

I'll comment on the ignition/charging system issues. If you can find a '82 ignition box, it can be used with the earlier harness. All the needed wires are there (with the exception of the 'vacuum switch' for part of the advance, another part you'll need to acquire), but you'll need to move some of them around in the plug to the box. It will be easier (and cheaper) to use the early ignition but because like Greg says, the '78 mechanical advance will probably cause tuning issues. So get a '80 advance unit, it will be compatible with the '82 cams. There's also some slight differences in the vacuum cans '78 through '80, but these aren't nearly as critical.

As to the charging system, the same thing applies. The wiring is pretty much identical, but the regulator/rectifier IS different. The XJ system puts out more current, so one modification you should do if using the XJ system is increase the wire size on the output from the regulator to where it connects to charge the battery (the one 'big' difference between the XS and XJ harnesses). With the higher output, it's even more critical that all connections be clean and near-zero resistance. I'll also point out that the XJ system DOES have wearing parts (the slip-ring brushes), the XS system doesn't.

One more minor difference. The XJ has a 'low oil LEVEL' indicator (a float switch in the pan), the XS a low PRESSURE indicator. Move the XS sending unit and oil pan onto the XJ motor and that's solved.

[BA80]

Hi Greg,
Thanks for the explanation of the differences.
Phil

Kind of a cursive explanation but makes the point. I don't type fast enough to go into detail.

I have the 78 timing setup on my 79 engine and is awesomely quick, particularly since the exhaust issue has been sorted out. Even with the 850 FD.

[XJOK2PLAY]

Bart,
Crazy Steve covered it pretty well.
I'll add this fwiw...

Numerous changes occurred in '82 for the XJ, as you're hearing.
Cams, heads, carbs, first year for electronic ignition, pilot boxes, oil level warning instead of oil pressure, charging systems... etc.

There's a small electronic device under the tank like a potentiometer.
It converts a vaccuum level to an electrical voltage that is then sent to the TCI, which processes and control timing.

This is different from all other XS11's. So, you'd have to have that little device PLUS the XJ's TCI to make the ignition advance work properly, if you use the XJ setup.

The XJ does use brushes in their alternator. Not a big deal, and there's an advantage. It puts out 5 MORE amps than the XS's. Helps if you run accessory lights, etc.

The XJ motor was built during Jimmy Carter's EPA era. Therefore, the '78-'79's idle more lopey, (like a hot rod with a high lift cam), and were more powerful. As the years progressed, and the EPA tightened it's grip on imports' emmissions, it had choked a lot from the XJ. They idle steady and smooth, no lope.
They still run fine, but even at mine's peak of prime performance tune, it still wouldn't run on top end with most '78/'79's. Carb jetting changed...

Nothing wrong with transplanting an XJ motor into an earlier XS, but unless it's what you have on hand, there are differences between them to be aware of. And they're the lowest performers (somewhat) of the XS lineup.

Electronic ignition and bigger charging systems are the desirable parts.
Teardrop shaped gas tanks rated @ 5.1 gallons are nice, too.

[Bartman]

So let me repeat back to make sure that I understand:

I can swap vac advance and stator on the XJ to the 78 parts (plus 78 carb) and it will run smoothly and fairly strong.

OR

I can buy a 80's ignition module and vac switch, move a few wires around, increase the current carrying wire's size and have a smooth running good motor (not hot rod).

I did ride my 79 today about 40 miles with those new clutch springs and l do like that hot rod feel 😃! But in the back of my mind I should be a good influence to my son and his friends when riding with them.

[BA80]

There is no centrifugal advance on the XJ, the ignition rotor is solid. You do know what I'm speaking of right?

You would need an 80 centrifugal advance unit to do it without rewiring.

[Bartman]

I "think" that I do. You are saying that the 78 advance + vac shouldn't be used but to get a 80's advance + vac (all of the left side of the motor's components).

I need to look up my other spare motor and see what it is. 3J6-001497, might work.

[XJOK2PLAY]

I "think" that I do. You are saying that the 78 advance + vac shouldn't be used but to get a 80's advance + vac (all of the left side of the motor's components).

I need to look up my other spare motor and see what it is. 3J6-001497, might work.

Guess I'm missing why you'd want to do that in lieu of the XJ's electronic ignition system?