Triumphrat

Rhinoe · 04-01-2009, 04:34 PM

After not running my '01 Thunderbird for almost a year due to relocation/medical complications I have been having some problems with it lately. Initially, only the #1 sparkplug was firing. I grabbed the main wiring harness where it runs under the spine of the frame and twisted it around. After that it started sparking all three plugs. Ever since then (About two weeks now) the bike has started up easily every day. However, it does not run perfectly. It seems to be missing (Feels like it is not getting enough gas) when cruising at very low rpms. Whe I give it gas it smoothes out instantly and pulls hard to redline. It idles smoothly.

Also, the headlight gets brighter when the rpms increase and dims when the brakes are applied.

I have tried different size pilot jets and different mixture screw settings, but nothing has changed. Could it be that there is a bad ground/connection in the harness that is causing all of this? I am pretty good with a wrench, but a bit lost when it comes to electrical problems. Any input would be greatly appreciated.

IrlMike · 04-01-2009, 06:15 PM

The headlight will dim as revs drop towards idle. This is normal, the alternator (charging battery & powering bike electrics) only starts working above around 1,500 rpm. Adding the brake light load will accentuate the effect.

Your moving the loom will only give a temporary benefit to the connections (likely coils) that were failing a bit - loose, dirty etc. You need to go thru' those properly & clean, tighten etc. See if can enlist a buddy who can help with this if you're very unsure with electrics.

You shouldn't be messing with carb settings to fix an electrical problem - put them back where they were, you'll make things worse !

Mike

Rhinoe · 04-01-2009, 07:19 PM

Thanks for the suggestions Mike. Appreciate any help I can get. I did clean and lube the connections to the coils before twisting the loom, but it did not make a difference. Also, when only the #1 plug was sparking I tested the two other coils and HT leads (attaching them to the #1 "primary circuit electrical connectors" - Haynes Manual) and they all worked. It seems that the problem would be somewhere in the wiring before the coils.

I was thinking the problem could be due to the carbs as the problem felt like it was not getting proper fuel. My changes ruled that out. No need to worry about the Keihins. I have taken them apart dozens of times and experimented with jet/needle/screw/float/airbox changes. They are pretty much at baseline now.

I didn't mean to sound like a complete newbie. I have done much work to this bike. However, I have never had to hunt down an electrical gremlin before and I know it can be a real pain in the arse. Will keep fiddling with the machine, hoping someone has come across and solved this problem before.

IrlMike · 04-01-2009, 08:11 PM

Have you considered the infamous coil failure fault, this may not show up testing with the plug removed from the engine? Swap #1 with another coil & see if the good cylinder moves, engine running. Aftermarket Nology pro fires are the sure cure.

Both plug leads & plugs can behave differently open air to in cylinder under pressure. Shouldn't rule out those at this stage either. Again swapping components can help diagnose.

Note the coil secondaries ground thru' the mounting hole sleeves. The bolt normally has a rubber washer so the connection goes thru' the captive nuts frameside.

Moving the loom could have jiggled the igniter connector. Contacts are kind of self wiping/cleaning when unplugging/plugging.

You should get an AC volts reading across the coil primary connections, can't tell you a value but it should be same on 2 & 3 as cyl #1.

Mike