Timing question update

[wayneshrt]

I posted this message a while back and just now had time to check my bike out.
"I have a 1981 xs1100 motor with 12000 miles on it. The motor set for a while and I installed it on my 1980 xs1100sg frame. All the extras like carbs were off previuos good running engine with 70000 miles. I wanted to take the old one off before it was not usable for parts.
The 1981 motor started right up and idles perfect. It has no ticks or knocks. My question is the engine will rev up to around 3500 rpms and then doesn't want to go any higher (just bogs down until 3500 or lower) and I wanted a second opinion. It also has good power until the 3500 or so is reached.
I tried taking off and on the vacuum to the distributer and there is very little change. I considered setting time but wanted to ask you guys first.
thanks wayne"

I wanted to thank everybody for their input and report that the ones which told me the distributor needed changed were right. I replaced the distributor on the 81 motor with my old 80 one and it ran almost perfect as soon as I hit the switch. It was almost plug and play since the bike had been ridden everyday and even carbs plugged and played.
Thanks wayne

[dbeardslee]

The 81's used the 4R0 TCI, while the 80's and previous used the 2H7. The 2H7 requires the mechanical advance under the pickup coil mounting plate, which you don't have on the 81 motor. If you've got the 80 motor, you can just swap the parts. If you don't, your going to need to find a mechanical advance.

These bikes don't use a distributor. Did you change the parts at the timing plate, or did you change the TCI? If you want to verify the TCI, the 2h7 has raised letters on it, while the 4R0 has a sticker on it. The wiring harness on the 80's is also different from the 81's, so changing out the TCI could be somewhat problematic.

[mro]

I'd bet you have a carb problem or less likely a problem with the wires from the pick up coils. 3500 RPM is around the range of transition from low speed idle/starter circuit to the mains on the carbs.

mro
BTW, welcome to CH 11

[mro]

TCI ???
Did you use the TCI from the 81 along with the motor?
Forgot about that but not sure just how much effect it would have using the wrong TCI.

mro

[trbig]

OK.. I am probably wrong, but I thought the 78-79 used the 2h7 and the 80-81 used the 4RO... and all of these have a mechanical vacuum advance. The advance mechanism rotates on a bearing that gets locked up sometimes. Take off your sidecover over the pickup coils and see if the assembly is rotating as you rev it. If it's rotating freely, then I'd suspect the TCI, as stated.

If it runs and idles well, then your actual timing.. cam-crank timing... is good.


Tod

[DGXSER]

There were a few things that changed from 80-81 in the ignition area. The 81 model introduced the full 3 ohm coils which got rid of the ballast resistors, Also in 81, they incorporated the mechanical advance into the $RO TCI and removed the mechanism from the timing area.

Not certain, but I would think swapping the 4RO or 81 TCI into the 80 electrical system with a mech advance in place and the ballast resistors in place would play heck on the timing and may even fry a TCI. If you put the 81 coils on a bike with the 80 TCI, ballast resistors, and timing setup it could again be ugly.

All of the 78-80 models used the same setups, 2H7 TCI with ballast resistors and actual mechanical advance under the timing plate and 1.5 ohm coils, until the 81 model so it is kind of important to get the entire system lined up with the right components when you switch the 81 motor into an earlier model bike. IMO. IIRC, the XJ model only changed from the 81 by removing the vac advance and putting it into the TCI with a vacuum module under the tank. So the XJ to 81 swap is not so bad.

[dbeardslee]

OK.. I am probably wrong, but I thought the 78-79 used the 2h7 and the 80-81 used the 4RO.

Probably. The 81's are the only year that used the 4R0 on the XS's.

[wayneshrt]

Answers to timing

I asked the question above a month or so ago and some said carbs, some wiring harness and some change distibutor. My answer is: first I know a distributor takes the fire and sends it out the the corrisponding plug and I call this a distributor only because it has all the same parts except a cap. Anyway I used my carbs, dist (whole timing, advance, moduals), and merely placed the motor on my 1980sg frame.
The 1981 timing parts were different but everything else was the same. When I changes the timing (dist) It ran just exactly the same before the old motor started missing. I did not adjust carbs or change anything else.
Also I have worked on cars, trucks, and bikes for over 40 years but am positive that a good mechanic is always open to more opinions plus it saves a lot of time asking instead of runnig a problem down the hard way.
thanks to everyone

[WMarshy]

I asked the question above a month or so ago and some said carbs, some wiring harness and some change distibutor. My answer is: first I know a distributor takes the fire and sends it out the the corrisponding plug and I call this a distributor only because it has all the same parts except a cap. Anyway I used my carbs, dist (whole timing, advance, moduals), and merely placed the motor on my 1980sg frame.
The 1981 timing parts were different but everything else was the same. When I changes the timing (dist) It ran just exactly the same before the old motor started missing. I did not adjust carbs or change anything else.
Also I have worked on cars, trucks, and bikes for over 40 years but am positive that a good mechanic is always open to more opinions plus it saves a lot of time asking instead of runnig a problem down the hard way.
thanks to everyone

I assume your talkin about the coils... Our bikes dont have a distributer and are not even close to the same. The coils are the black "boxes" the spark plug wires connect to. The TCI the others are talking about is under the seat in the back near the fender or on the fender for the earlier models... It helps everyone to enderstand the probelm and the solution when we use the same/correct lingo for parts... Happy to hear its running.

[DGXSER]

Hey Wayne, the distributer in these bikes is basically the pickup coils under the timing plate down under the left side cover on the engine. It is also in the TCI or electronic ignition box.

The pickup coils (2 of them) send a signal each to the TCI box. The TCI box then reacts by sending a signal to each of the two coils based upon which pickup coil has signaled. So each coil is fired by one of the pickup coils through the TCI. Each coil then sends a spark voltage to two of the plugs. One coil sends the spark to cylinders 2 and 3, the other to cylinders 1 and 4.

So it is a somewhat drawn out and multi-component "distributer". HTH

Now to further complicate the system, on the pre 1981 models, the mechanical timing advance is an actual mech adv. mechanism behind the timing plate. Also on the pre 1981 models, the coils are 1.5 ohm coils and there is a "ballast resistor" built into the system which provides a 1.5 ohm resistance. So the coils and the TCI from a pre 1981 system do not work well on a 1981 system with no ballast resistor.

But it sounds like you got it working well, although I could not follow exactly what you did.

[WMarshy]

Thanks for that clarification.

[wayneshrt]

timing

This is an excellent site and I enjoy all the interaction. I noticed a couple seemed to be confused at my definition so I thought it would help to draw a pic.
The distributor of any motor distributes fire to the plugs; it can have one ridge on side of the reluctor and spin making contact with one or more pickups (or points). As it turns the fire is sent to the corresponding coil which sends it out to plug.
On some motors the may be one pickup and several ridges on reluctor which as each ridge passes the pickup creates fire for a different plug and it usually needs a rotary button to direct the fire through a cap that divides the wires and fire to the corresponding plug.
Both have timing plates, points or pickup coils, and reluctors. Both turn with engine by crank or cam. The xs1100 has a vacuum advance and is called pick up coil governor assembly in parts catalog. I have also seen pulsor coil, timing plate, pickup assembly, and there are probably more.

http://i302.photobucket.com/albums/n.../mopardist.jpg

http://i302.photobucket.com/albums/n...shrt/dist1.jpg

[dbeardslee]

What did that part come off of?

[Ivan]

If you swapped in an 80 motor with an 81 ignition setup, you also need to swap the reluctor post. On the 78-80 they had mechanical advance hidden behind the pickup coil plate. on 81 they switched to a solid reluctor with no advance, and left it to the TCI to advance based on RPM, but kept the vacuum advance.

The easy way to tell is to look at the pointer of the reluctor. If it looks to be formed from a small piece of sheet metal and spot welded on the post, it is the early model. If it looks like a cast piece that is pressed on the post it is the 81.

If you had the early reluctor with the late TCI you could have been running up to or over 60 degrees of advance when the vacuum advance kicked in, which happens about 3500 rpm. This would have definately made it run bad and more than likely caused a lot of ping.

If you have everything swapped with like parts, then all should be good.

I also get what you are saying about the distributor. But distributors are on the secondary side, I think the pickups would be analogous with breakers. JAT