Sudden loss of power

[davekeck]

Hey guys, I was on the highway when my '82 XS650 lost power quickly, as if I was out of gas. I switched it over to the reserve tank and then filled up the tank at the gas station, but there was no change -- it still accelerates very slowly.

It seems to be running on both cylinders, as both exhaust pipes are equally hot to the touch.

The alternator rotor is starting to fail, so that may be the issue, but I don't have a multimeter at the moment to test the battery. It fires right up with the kick start, but barely turns over with the electric start. Could a low battery cause such a sudden loss of power?

 

[Take Warning15]

It could be giving you a weak spark.

 

[XSLeo]

Yes, the TCI is very voltage sensitive. When I had charging issue with my 81 I could fully charge the battery and everything worked great, even the e-start.
Full charge, kick start and 20 minutes later it was running like crap. No power.
Do you have a Harbor Freight near you? The sell multi meters for almost nothing. With some coupons they are free.
My item #90899 works very well. Just as well as my $40 SunPro.
You will need a meter to check out the charging system.
You can spend around $20 and get about the same meter at most auto parts stores. A few bucks less at Wal Mart.
Leo

 

[davekeck]

Thanks guys, I'll start by assuming it's a low battery. I have a multimeter at home, I'm just 400 miles away and every place is closed for the night. Going to try an auto parts store tomorrow...

 

[Take Warning15]

Check the acid levels in the battery cells. You can top them just up to the plates with distilled water.

 

[davekeck]

Today I replaced both the battery and the spark plugs and the bike still ran poorly.

I swapped the spark plug cables (connected the left-side cable to the right cylinder and vice versa) and the bike ran great! I then restored the original cable set up and it still ran fine, so I assume the problem was either a loose cable or a coil going bad. I still need to remove the tank to investigate further, but maybe this will help someone in the future.