CDI Box differences over the years ?

[Colin Compton]

Dear Group,
I need a little help here and any opinions, help or suggestions would be appreciated.
I recently bought an 81 XS1100 that had been abandoned at a motorcycle shop. I have cleaned the carbs, checked the jet sizes and have synced the carbs. The problem is the bike idles fine, but will only rev to about 7k.
The bikes has an aftermarket exhaust system, stock jets, and a stock airbox. The ignition timing seems to be advancing properly. The last weird thing is that the bike has an earlier year ( 79 ) CDI box.
Should I go with bigger jets ? A different CDI Box ?

Any thoughts would be greatly appreciated

Colin

[randy]

Welcome to the forum, Colin.

It may not be advancing enough. Depends on what the previous owner did underneath the pickup coils. The pre-81 models had mechanical advance on the rotor. 81 and up had electronic advance built into the TCI box. You need to dig a bit deeper under the timing cover to discover what you've got. Take a visit to my webpage (below) for some more info.

BTW, put your location and bike model in your details. makes answering questions a bit easier.

[crazy steve]

You may also want to check to see if the motor is a '81. The TCI needs to match the engine, unless the engine-mounted components have been swapped to match the box.

'78E original owner

[DGXSER]

And the plot thickens

The pre 81 models had mech advance under the timing plate, the 2H7 TCI, AND had 3 ohm coils, and no ballast resistor.

Sooo, not sure of all the electrical implications of the 3 ohm coils and no resistor on the TCI, but perhaps it plays a part as well?

[randy]

Sooo, not sure of all the electrical implications of the 3 ohm coils and no resistor on the TCI, but perhaps it plays a part as well?

Same difference, TCI sees a total of 3 ohms in either configuration.

[dbeardslee]

What's it doing at 7k? Does it act like it's starving for fuel? If you had the wrong TCI installed, I doubt that the motor would rev that high, but you never know.

[Elevener]

The pre 81 models had mech advance under the timing plate, the 2H7 TCI, AND had 3 ohm coils, and no ballast resistor.

Sooo, not sure of all the electrical implications of the 3 ohm coils and no resistor on the TCI, but perhaps it plays a part as well?

My 80 had a ballast resistor.

[randy]

Correct 80 was the last year of the ballast.

[DGXSER]

Ooppsss

My 80 had a ballast resistor.

I had a brain fart in mid sentence there.... Yes, the PRE 81 models had 1.5 ohm coils and the ballast resistor stock. The 81 and later 82 XJ models had 3 ohm coils and no ballast resistor.

Sorry for any confusion created there.

[Colin Compton]

Thanks for the info !!

Dear XS1100 Group,

Lots of thank yous go out to all the people who have sent messages about my problem with the bike.
The bike is serial number JYA4R000-3-BA003328 which I believe makes it a 1981 (?) model. This would be confirmed by a manufacture date of 9/80. Additionally, the B as the 10th digit also confirms the bike as an 81.
I may be wrong, please feel free to chime in here, that the serial number indicates an XS1100SH model (?)
The motor is serial number 4R0-00328 which, by the last three digits matching, indicates to me that it is the original motor to the bike. Any thoughts on this would be greatly appreciated.
The bike has a vacuum advance on the ignition pickups and it goes to full travel when at full throttle. It is my understanding, please correct me if I am wrong about this, that the bike uses both a vacuum and a programmed advance on the ignition timing ??

Any thoughts would be Greatly appreciated

Colin

Marietta Ga.

1981 GS850G - Had for over 25 years, can't kill it
1979 CBX - Bought from an estate 15+ years ago and never ridden
1982 CBX - My rider for over 20 years
1986 VF700F - Chic bike (?)
1979 KZ1300 - Requires it's own zip code. will be sent to Scandinavia soon
1985 Honda Sabre - Will soon be the main rider
1975 GL1000 - Low serial number and a locked up motor currently hibernating
1976 GL1000 - Shredded Tweet
1985 Honda Sabre - Will get to eventually
1977 GS750 - An exercise in simplicity
1981 XS1100 - A conundrum

[oldnortonrider]

Colin, the numbers you just gave are the key. You see part of the frame number has "4R0", and motor number starts with "4R0. The CDI is supposed to also start with "4R0". If previous owner has put a CDI on your machine that starts with the number "2H7" , that will make it flatten out early on the rpm's, like it's got a governor on it. If your CDI does start with the number "4R0", then that will not be your rpm problem. Look at the number, and let us know.

[randy]

The 4RO TCI boxes are rather rare, which is probably why the P.O. installed the 2H7 TCI. The simple fix is to install a rotor from a 2H7 that has the mechanical advance, then you will have all the advance you'll ever need.

[DGXSER]

I do just so happen to know where a spare 4RO TCI is. But it might be cheaper to get the mech advance setup.

[oldnortonrider]

I hadn't checked lately, but there's usually 1 or 2 or 3 on eBay.

[dbeardslee]

But it might be cheaper to get the mech advance setup.

The wiring harness between the tci and the coils is different on the 81's than on the earlier models. Might have some issues there if you try to adapt a 2H7 to an 81. JAT