No power under load

The other day I was tra la la-ing along on my 1980 LTD, when I heard a bang and I lost all my power. The bike slowed down and died on the freeway. This was the first time I had ridden the bike with another passenger, and it was about a mile of riding.

I pulled over and found that the main fuse was blown (had a 15a in there, and the service manual called for a 20a) So I replaced the 20a fuse and started her up. Purred like a kitten. I started off on the road again, but there was no power when in gear. I could rev it up to 6-8k rpm, but it would not go over 45mph.

So i drove it back home, and found that the air filter had some sort of burn-out and was partially melted. I put in a new air filter, pulled the carbs and did a full rebuild/clean.

I fired her up, idled great, but still had no power when under load (little around the block test drive). The throttle was responsive, the RPMs went up to the right places, but there was no oomph. I could full throttle in 1st gear and I would only get to about 25mph.. really odd.

I thought it was a carb thing, but I am thinking maybe a totally shot clutch, and its just slipping like crazy?
Any ideas?

Pics of plugs?
Steve

I wonder if you blew up your charging system, over voltages it all and maybe the ignition system too.

Re: Steve:
When I pulled the plugs, they were all super black (rich), and I replaced them with new plugs. When I did my mile or two ride around the block, the plugs all looked clean except for one which was black. on cyl #4.

Compression cold (apparently this isnt the way to do it) was about 110 on each cyl, and the compression didnt leak. I know the manual calls for a higher (150-180 compression) when warm. But I need to do a warm test.


Re: missionkz:
Would that have an effect on the low torque/power when driving?

Have you adjusted the valves?
Steve

charleylabri wrote: Re: Steve:
When I pulled the plugs, they were all super black (rich), ....
Re: missionkz:
Would that have an effect on the low torque/power when driving?

I'm not sure. I don't know why the fuse blew. But if it was an over voltage issue, it could be possible to damage current sensitive electronics such as electronic ignition or maybe even the coil windings.

no, that was going to be my next step. But before I started ordering shims, I was trying to imagine why it went from running perfect to bam, terrible. Dont valves fall out of spec slowly?

Tight valves can cause all kinds of symptoms. Check them then move on.
Steve

try pulling your plug wires one at a time and see if cylinder 4 has any affect when you pull it. If no affect when you pull cyl 4 switch cyl 4's plug wire with cyl. 1 's plug wire. If the problem jumps to cyl 1 then it's most likely electrical related if not it's most likely something mechanical.

missionkz wrote:

charleylabri wrote: Re: Steve:
When I pulled the plugs, they were all super black (rich), ....
Re: missionkz:
Would that have an effect on the low torque/power when driving?

I'm not sure. I don't know why the fuse blew. But if it was an over voltage issue, it could be possible to damage current sensitive electronics such as electronic ignition or maybe even the coil windings.

But if I had electrical parts damaged, would if affect the running of the bike when under load?

swest wrote: Tight valves can cause all kinds of symptoms. Check them then move on.
Steve

Ill take a look this weekend and let you know!

joshkamp1988 wrote: try pulling your plug wires one at a time and see if cylinder 4 has any affect when you pull it. If no affect when you pull cyl 4 switch cyl 4's plug wire with cyl. 1 's plug wire. If the problem jumps to cyl 1 then it's most likely electrical related if not it's most likely something mechanical.

interesting idea! I will do this on saturday, and update the thread.