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Old 12-16-2009, 02:04 PM
wayneshrt wayneshrt is offline
Join Date: Mar 2008
Location: kingsport, tennessee 37660
Posts: 33
Question timing question

I have a 1981 xs1100 motor with 12000 miles on it. The motor set for a while and I installed it on my 1980 xs1100 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
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Old 12-16-2009, 02:15 PM
motoman motoman is offline
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Location: Grand Junction, Colorado
Posts: 8,309
81 motor had non adjustable timing as slots are filled.........you got some carb issues.......can't just plug and play and expect perfect running. Plus after cleaning and checking carbs all out using info on this forum you need to sync them after installing carb bank. Just removing and installing will change carb sync.....also finish all you info here, location, etc. as with that you may be near some XSessiveve help.
81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.
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Old 12-16-2009, 03:06 PM
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Schming Schming is offline
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Location: Pittsburgh,PA
Posts: 1,882
Hi Wayne, you might want to do a search for the pickup coil wire fix. Maybe the timing isn't advancing properly. HTH
1980 XS1100G "Dolly G" Full Dresser (with a coat of many colors )
1979 XS1100SF (stock-euro mods planned)
1984 XV700L Virago (to be hot-modded)
1983 XJ750MK Midnight Maxim (semi-restored DD)
1977 XS650D ( patiently awaiting resto)

Sometimes it takes a whole tank of gas before you can think straight.
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Old 12-16-2009, 04:08 PM
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dbeardslee dbeardslee is offline
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Location: Maineville, OH
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The TCI on an 81 is different than the 80's. Pre '81 used the 2H7 and the '81 is a 4RO. The rotor under the timing plate is different too, and the wiring harness was slightly different. The pre '81's have a mechanical advance, while the 81's don't. You might be able to get it working by swapping out the mechanical advance and the plate with the pickups on it from the 80 to the 81 motor. You'll have to drill out the tamper proof bolts to get them off. You'll have to get some new bolts, and then you will have to set the timing.
I think I have a loose screw behind the handlebars.

'79 XS11 Standard, Jardine 4/1, Dyna DC1-1 Coils, 145 mains, 45 pilots, plastic floats - 25.7mm, XV920 fuel valves, inline fuel filters, speed bleeders, Mikes XS pods, spade-type fuse block, fork brace, progressive fork springs/shocks, manual petcocks, 750 FD, Venture cam chain tensioner, SS brake lines

Last edited by dbeardslee; 12-16-2009 at 04:16 PM.
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Old 12-16-2009, 04:11 PM
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John John is offline
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You need a 4R0 ignition module if you are using the ignition components from the 81 engine. Try swapping the pick up coils, and centrifical advance from your 80 engine. I'll bet that cures it.
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Old 12-16-2009, 04:30 PM
Athedra Athedra is offline
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Join Date: Oct 2009
Location: Benoni, South Africa
Posts: 221
Hear what you are saying, but have you considered fuel starvation?

Have a look at your petcocks and tank filters. Once you are happy with your fuel supply, then check you vacuum advance.

I am working on my knowledge of the 2H9 here, where you should have a 39 degree on 5000 rpm. I found the big bore motor to be the same. Just put your bike on an electronic tach/dwell tester. (About R200 at Midas (about $20)) and test it like that. If you are happy with you idling dwell (Think it was 10 degrees, but not sure) then have a look at your Coils and HT leads. The tach/dwell I got hold of tests everything from ohms (to test your coils) right up to volts. I paid R200 for mine, and can test eveything from Volt supply to my coils to my actual revs and dwell angle).

You might even have the wrong heat range plugs in there. Over here we use NGK BP6ES, but saw a few guys mistakenly putting in BP6ERS which is a higher resistance plug used for Racing (as far as I understand it). If I am not mistaken, it is shorter, resulting in your sparkplug not reaching into the actual chamber.

The other possibility is a stuck choke. See if your choke isn't stuck. Had that on my previous set of carbs where the holding screws was loose, and the choke lever closed, but not the actual chokes on the carbs. This will however result in over fueling, giving you a similar result. While we are on the over fueling part, what filters do you have on there? A while ago, we discussed cones (pods) with a broad inner lip closing the jets. It will be as if you close the carbs at the back with your hand (Choking it).

Just a thought...........
'79 XS1100 (2H9) named Bones
1196 Big Bore
4-1 Cowley exhaust
750FD Conversion
Echlin 54mm Racing Cones (Americanese = pods)
Black Ebony Bottled glazed Tank (To be redone now)
BMX footpegs
Tank internally lined (Professionally this time)
GSX400 Throttle bodies (Under serious investigation)
Anti Sticky float bowl system
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Old 12-16-2009, 05:30 PM
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John John is offline
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I am speaking from experience

One of our members, BTDTdan, who lives in my area had the very same problem. It was an 81 Special. He put the bike in a shop and they messed with the carbs, timing, etc... I know the shop owner, and asked him if I could look at the bike, he said ok. The first thing I did was remove the seat and there was a 2H7 TCI. I told him that it was the wrong TCI, but he said there was no difference in the TCIs. Instead of argue with him, I came home and went to YamaMama's parts site. I printed out the exploded views of both ignition systems, showing him the differences between part numbers of the TCIs. I told the member of what I found, and suggested he find a 4R0 module. He was able to locate one, and as soon as it was installed the problem went away. Wildkat's bike has a 78 engine in it and we had to swap all of the ignition components from the 81 engine onto the 78 engine, and there was never any problems with the performance.
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adjust time, motor, question, timing, vacuum

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