Loss of power 300 miles into trip

perkinja

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I'm taking a trip from Chicago to Charleston WV and I made it here but it took 16 hours.

The trip started out great, made the first 300 miles cruising along at 75mph. But I stopped for gas, had myself a sandwich and drink and then kept going and everything just went to crap.

My acceleration through all the gears seemed fine on the way to the highway but once I got to and over half throttle It just wouldn't accelerate. It makes small poping noises out my left exhaust when I decelerate as well.

I've checked all my wires to see if my pamco is losing power and it's all good. I checked my timing wth marks I made behind the cover of the pamco and it didn't move at all so I'm assuming that's good as well. I checked my advance and weights, they look fine and snap back.

Im thinking my carbs have become extremely unsyncd. But even if they were unsyncd I should still be able.to go faster than 55mph. Maybe my advance weights are shot? If you have an idea I'm open to hear it, don't want to take 2 days to get home haha. Thanks guys
 
its unlikely something has gone out of sync I should have thought. My inclination would be to check to see if an air leak has developed on the inlet and carbs somewhere due to the vibration or an exhaust valve is leaking. Check all around the inlet rubbers and carbs for leaks and remake the joints .
Check the exhaust system for leaks around the joints.;)
Lastly I would reset your valve lash in case you have a leaking or burnt exhaust valve due to your lash beiing set too tight.
Do a compression test to verify your valves are seating and not burnt.
Check your spark plugs for colour after a high speed run ie plug chop. Do a steady run at the speed you are experiencing problems then pull the clutch and cut the engine and coast to a stop.
 
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If you have vacuum barbs on your intake boots check to see that they are caped. Like peanut said it sounds like an air leak. Since you got gas I would drain some out of the bowels. Water possible. The advance weights snap back are the opening when you rev the engine.
 
...Since you got gas I would drain some out of the bowels. Water possible...

Ditto, (but I would drain the bowls, pop out and clean the mainjets). It would take your 'fresh' fillup about that long to get into the carbs. Filling station employees are supposed to periodically check the water levels in the underground tanks, using a long wooden dipstick. They've been known to lapse that duty...
 
Hardly have service here but I'll make sure to check the intake boots. I do have my barbs covered and I put 2 fresh exhaust crush gaskets on about a month ago. I'll clean the jets and toss fresh gas in there.
 
I took my carb off and there was oil on the bottom of cylinder 1 intake, enough to leakk through my boot back to where it meets my carb. So I cleaned that up made sure the boots were tight and tight on my carb. I made sure the header pipes were tight against their clamp nuts as well.

I fired it up let it idle for about 3 or 4 min and then Ripped it down the road winding out first second and third and it ran just like it should, no back fire and deceleration and no bogging past half throttle.

But the engine wasn't as hot as it is when I'm highway riding and seeing as how I don't have room to take it at highway speeds without going down the road for an hour I think maybe the problemishes has fixed itself?

I think my valve stem seal on my intake has blown and is leaking oil once the oil is thin from running for a decent amount of highway riding. Anyone else think so too?
 
This calls for a plug inspection. Your left plug may be running on the verge of oil fouling.
Do you get any smoke on startup, that slowly goes away?
 
We don't know anything about your engine but if it is a recent rebuild it would be worth going over the cylinder head nuts and retorquing them in case you've developed a slight head gasket leak.
Riding 300 miles cruising at 75mph all the way, the continuous vibration and heat is bound to produce some problems on these old bikes
 
Left cylinder has a bit of oil on it. Right cylinder doesnt. There is a bit of white smoke that comes.out my left tail pipe when I Rev the engine at idle.
 
I'm not saying they won't do it, but it's not the way I roll an XS650. It's a happy camper all day at 50-60 mph. A long hard run on the interstate may show you where the weaknesses lie.
 
:agree: Marty is right on the money. Perkinja's bike has some internal engine problems, that may have taken 2 or 3 years to show up, if he drove at 100 km/hr ( 62 mph) . By running down the road at 75 mph, he has just compressed 2 or 3 years into one trip. 75 mph was OK when these bikes were in new condition, but sadly these bikes are now getting older.......................time for a top end re-build now.
 
I just rebuilt the entire motor when I got my crank rephased about 2 years ago. There's around 6500 miles on the engine. If I already need a tip end rebuild Im not taking this across country to much anymore haha
 
I just rebuilt the entire motor when I got my crank rephased about 2 years ago. There's around 6500 miles on the engine. If I already need a tip end rebuild Im not taking this across country to much anymore haha

I bought mine new in 1983. I've never had an extended interstate run on it. I have had it on trips up to 2000 miles long. I rode it from Cherokee, NC to Front Royal, VA on the BRP and back again in 2010. It will run all day on the back roads. Even with over 50,000 miles on it, I could likely ride coast to coast right now and make it fine. I'm just going to have to go all the way at 4,000 rpm. That's where these old girls are happy.
 
I just rebuilt the entire motor when I got my crank rephased about 2 years ago. There's around 6500 miles on the engine. If I already need a tip end rebuild Im not taking this across country to much anymore haha

Perhaps the top end work 2 years ago missed replacing some key components, that were nearly worn out? A leak down test may indicate where the problem is.
 
I bought mine new in 1983. I've never had an extended interstate run on it. I have had it on trips up to 2000 miles long. I rode it from Cherokee, NC to Front Royal, VA on the BRP and back again in 2010. It will run all day on the back roads. Even with over 50,000 miles on it, I could likely ride coast to coast right now and make it fine. I'm just going to have to go all the way at 4,000 rpm. That's where these old girls are happy.

Again, I totally agree with Marty. I'm in my 10 th year with my bike, and it just loves to drive down the road at 100 km/hr (62 mph). With 17/33 gearing, the engine is purring at about 3700/3800 rpm. Last summer, I travelled 620 kms during one day, and the bike ran great, but my butt was a little tired:bike:
 
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