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2001 Bonneville TPS loom wiring missing

4K views 6 replies 3 participants last post by  Trumpet02 
#1 · (Edited)
I recently purchased my 2001 Bonneville, privately, with a genuine 8,700 miles on the clock. Its a two owner bike with a comprehensive service history. Its my third Hinckley Bonnie and has standard carbs fitted. Its in standard factory spec except for TORs and a Triumph alarm fitted. It hadn't been used for a while before I bought it but appeared to run well. It starts instantly, cold or hot, ticks over well but has an annoying stutter between closed throttle and opening up again.
The exhaust gas recirculation kit has been removed and plugged.
The carbs are clean inside and have standard jets. Fuel mixture screws set at 2 and three quarter turns out. It has needles with adjustable settings with the circlips on the third notch down. It has the factory airbox/air filter. The diaphrams appear to be in good condition and the slides move freely. The spark plugs are new and appear to be burning the right colour. However, when checking the wiring, I noticed that the Throttle position Sensor was not connected to the main loom or anywhere else and that there didn't appear to be anywhere to connect it to !
Stupid question time, where on the loom should the TPS plug connect to ? Is it hidden from view ?
Could the person who fitted the Triumph alarm have used the TPS Sensor wiring as a power source ?
Once the stutter has cleared, it pulls very well, however, when I returned home last night from a 50 + mile run, it had been stuttering more than usual and backfiring on tickover, eventually cutting out at a junction.
The lights are bright and it appears to be charging ok.
I know its difficult to diagnose a problem when the bike isn't in front of you but any helpful advice would be very welcome.
Thanks, Mac.
 
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#3 ·
Thanks for that.
I've had the seat and side panels off and had a search round with a torch.
As you mentioned, it may have dropped down behind the air filter box.
Hope its there !
At 8,700 miles I cant imagine that the TPS would have failed, which makes me wonder, why was it disconnected in the first place ?
Would the TPS being disconnected cause the mentioned stutter ?

Mac.
 
#6 ·
Your carbs have non standard needles installed which may be causing your stuttering. The standard needle reference is NAGB. It's hard to say if 2.75 turns out on the pilot screw is correct with the needles that are in there.

Your igniter unit has five maps which are set to 0%, 25%, 50%, 75% and 100% throttle opening and as you open/close your throttle the ignition timing is interpolated between the five maps giving different timing depending on engine load and revs.

With the TPS unplugged, your ignition timing is set to one map (100% throttle) throughout the rev/throttle range. This means that at different engine loads/revs your ignition timing is advanced or retarded more than it should be for that particular engine condition and the only time your ignition timing will be as Triumph developed it will be a full throttle.

As Forchetto has said, the triangular TPS plug will be around the front of the airbox somewhere, but it's possible you may need to drop the airbox to find it if it's really tucked away.
 
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