To give the full story I'm in the middle of a cross country road trip on a 1973 R75/5 with a Velorex 562 sidecar. It's hauling me, my wife and a fair amount of luggage so we're's definitely pushing the bike but we've been comfortably cruising at 60-65mph. We were in New Orleans a couple of days ago and stuck in stop-and-go traffic where I had to frequently turn off the bike from fear of overheating. Since we left New Orleans the bike has been struggling at 50-55 mph. It's now also harder to start and it's idling very poorly and often cutting out when coming to a stop if you don't give it some throttle. The idle is uneven but there's no noticeable misfires or pinging while riding, it's just underpowered. It does seem to make a bit of an undulating noise when nearing its limit (hard to explain, it sounds like the load is on a sine curve but the RPM is steady).
I pulled the plugs and they were looking white and crusty. I figured this might be residue from the stop-and-go so I put in new plugs, rode another 50 miles, pulled the plugs and they looked good with a slight light tan.
The carbs were rebuilt 3k miles ago with new diaphragms. I did the valve clearances at the same time. The valves still sound good so I haven't tried adjusting them again as it also doesn't seem like something that would happen overnight.
Things I've checked so far:
2. The ignition timing is spot on using a inductive timing light (I recently added dyna3 ignition to the bike)
3. I've done an aerosol test and can't find any vacuum leaks
4. I checked float levels (in case it's running lean and 50 miles wasn't enough to get a read) and one bowl is at 21m the other at 25mm so could definitely be better but doesn't explain the overnight power drop
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I have not yet tried adjusting the idle or syncing the carbs as that seems more likely to fix a symptom than the cause.
It could be a red herring but the only thing I really have to go on is that the bike might have overheated before this happened (but no glowing pipes of anything). Any ideas for other things to check? This seems too consistent to be caused by bad coils but maybe I'm wrong?
It runs so I'll keep riding and try to figure it out along the road but not really sure what to try next other than getting another plug read after a longer ride.
Thanks for any suggestions.
I pulled the plugs and they were looking white and crusty. I figured this might be residue from the stop-and-go so I put in new plugs, rode another 50 miles, pulled the plugs and they looked good with a slight light tan.
The carbs were rebuilt 3k miles ago with new diaphragms. I did the valve clearances at the same time. The valves still sound good so I haven't tried adjusting them again as it also doesn't seem like something that would happen overnight.
Things I've checked so far:
2. The ignition timing is spot on using a inductive timing light (I recently added dyna3 ignition to the bike)
3. I've done an aerosol test and can't find any vacuum leaks
4. I checked float levels (in case it's running lean and 50 miles wasn't enough to get a read) and one bowl is at 21m the other at 25mm so could definitely be better but doesn't explain the overnight power drop
[/LIST]
I have not yet tried adjusting the idle or syncing the carbs as that seems more likely to fix a symptom than the cause.
It could be a red herring but the only thing I really have to go on is that the bike might have overheated before this happened (but no glowing pipes of anything). Any ideas for other things to check? This seems too consistent to be caused by bad coils but maybe I'm wrong?
It runs so I'll keep riding and try to figure it out along the road but not really sure what to try next other than getting another plug read after a longer ride.
Thanks for any suggestions.