Triumph Rat Motorcycle Forums banner
1 - 8 of 8 Posts

Discussion Starter · #1 ·
This one has me stumped and I think I have an electrical problem. I could use some help...

I have owned this bike since new and have 22,000 maintained miles on it. The bike ran great until about 100 miles ago. I originally attributed the condition to poor fuel: Poor acceleration, bucking from about 2500 rpm to 4000 rpm. Weak power. To start, this occurred when the bike reached operating temp, but now it's all the time.

I pulled the plugs, they were about 12,000 miles old and all three were heavily sooted and appeared gas fouled. They were all identical in appearance. Assuming a rich condition, I cleaned the air filter (K&N) and checked the choke adjustment. At that time, I inspected the inside of the carbs and all appears clean. The fuel has been replaced and a shot of Lucas Fuel System cleaner was added thinking there may be deposits to clean out.

The second set of plugs were gas fouled in less than 10 miles and the bike is worsening. The bike has been on a Battery Tender, so I am sure there is 12 volts at the battery.

If it were a lean condition, I would start looking for vacuum leaks. That is how it is behaving. But the plugs tell me rich fuel or low spark. I haven't made any adjustment to the carbs and the airbox and filter are unobstructed.

The next step is to start digging into the electricals (coils, etc.) I am concerned that my issue may be in the charging system. I'll check that with a voltmeter.

I am not familiar with the ignition system on this bike. I have hotrodded small block Fords for years so I understand the principles.

If anyone has a place to start, I would appreciate it.


[ This message was edited by: Singlefin on 2007-01-04 21:20 ]

· Registered
728 Posts
90% of the time you think it is carburation it turns out to be ignition.

I would check out the coils, I think that they are a fairly likely culprit. Check for resistance on LT & HT see what you get for starters.

Coil failure can typically start to occur after operating temperature is reached, so your failure mode would appear to correlate with that.

Nige. :cool:

· Premium Member
10,732 Posts
On 2007-01-02 23:24, Singlefin wrote:
The bike has been on a Battery Tender, so I am sure there is 12 volts at the battery.

I am concerned that my issue may be in the charging system. I'll check that with a voltmeter.
I am not sure that this has anything to do with your problem, but you are making assumptions and that can be dangerous when diagnosing faults.

Check the fluid level in the battery.
These bikes tend to be a bit thirsty on battery fluid normally, and if it has been on the battery tender for any length of time, it may have dried it up a bit too.

Check the charging voltage with the revs above 3k rpm.
Check the battery voltage when starting.

Get back to us with your findings.

Discussion Starter · #5 ·
Without sounding defensive, my assumptions about the battery were based in the fact that it is about six months old, the acid at the proper level, and it had been on an anti-sulfating trickle charge.

I did hit it with a multimeter and the voltage is 13.5v. The charging system checks good as well.

I put a new spark plug on the #3 ignition wire, grounded it, and got a pale yellow spark. Not the blue I'm used to from the hot rods. This looks like weak spark is my problem.

I am concerned at this point, since all three plugs read exactly the same, that the coils are OK. I haven't pulled the tank and checked them with a multimeter. In fact, I don't know what my reading should be.

Since there is spark, the breaker or pick up, is functioning and unlikely to be at issue. Sort of like if you have spark, your points are breaking the current. Again, if there is a way to test this with a meter, what should the reading be?

The remaining, and in my opinion, most likely culprit, is the module or igniter. If this is anything like a car, we're measuring milliamperes. A powered multimeter could spell disaster.

I think at this point, I'll get the dealer involved rather than just replacing parts. At least this way, I don't think they'll BS me with a diagnosis.

Discussion Starter · #6 ·
Had the same problem on my 1998 TBS at about 25K. Replacement coils solved it. Also replaced the ignition sensor. I then went the entire season (4k miles) without a recurrence.

Discussion Starter · #7 ·
I am sure that you have done this but, checkall your connections and grounds. It seems to me that the odds of all three coils going bad at once is probably very high. At the cost of new coils I would check my other pieces before randomly replacing parts and hoping.
1 - 8 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.