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Discussion Starter #1
So I was riding on the highway earlier when suddenly, the bike began to slow down and lose power. I limped it home at about 30mph the whole way, having to keep the throttle fully open. I checked for spark, spark was ok. There is gasoline coming out of the carburetor boot on the cylinder head, and out of the intake. Anyone know what this could be?
 

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Stuck float, likely.

Tap on a solid area of that carb with the handle end of a big screwdriver.

But not hard enough to dent or bend anything.

Sometimes that'll make it let go.
 

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FREEBIRDS MC CENTRAL NY
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Look in the carburation board for a sticky titled "Wolfie's back blow method"

Sent from my Z899VL using Tapatalk
 

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Discussion Starter #4 (Edited)
Well, tried blowing it out, tried removing the bowls to spray carb cleaner, no luck. At idle it still refuses to review past 4k, and the rear cylinder misfires. The left carb still has gas coming out the intake. It also pops at the carb/airbox when I give throttle... What would the next step be? Remove the carb entirely? Or should I investigate a possible cylinder issue?
 

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Yep, remove carbs, remove bowls, remove dirt. Need to pull the float and float valve to get to the chunk of dirt holding the float open.
 

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Discussion Starter #6
So before I event pulled the carb I decided to perform a compression test. Front cylinder had 180, rear cylinder, zero. Looks like the motor is toasted....
Honestly not sure if I feel like doing a rebuild, so might be time for a new bike....
 

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So before I event pulled the carb I decided to perform a compression test. Front cylinder had 180, rear cylinder, zero. Looks like the motor is toasted....
Honestly not sure if I feel like doing a rebuild, so might be time for a new bike....
Did not see that coming.

No noises before or after, just sudden loss of power?
 

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Discussion Starter #8
So before I event pulled the carb I decided to perform a compression test. Front cylinder had 180, rear cylinder, zero. Looks like the motor is toasted....
Honestly not sure if I feel like doing a rebuild, so might be time for a new bike....
Did not see that coming.

No noises before or after, just sudden loss of power?
No odd noises at all, just lost power on the highway, wouldn't rev past 4000 RPM, and wouldn't drive past 30-40 mph. It did shoot some oil out of the carb boot which gave a hint, but I wanted to confirm. The rear spark plugs were also oily. It had been burning oil from the rear cylinder for a while, I just never expected it to completely give in.
The only odd noise was popping out of somewhere on the top end when I revved it at idle.
 

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No odd noises at all, just lost power on the highway, wouldn't rev past 4000 RPM, and wouldn't drive past 30-40 mph. It did shoot some oil out of the carb boot which gave a hint, but I wanted to confirm. The rear spark plugs were also oily. It had been burning oil from the rear cylinder for a while, I just never expected it to completely give in.
The only odd noise was popping out of somewhere on the top end when I revved it at idle.
This is one of those where I'd have to pull the cylinder apart just out of curiosity. Sounds like it has a piston failure of some sort. Could be the head itself but I'd expect some noise. The popping makes me think intake valve. ... broken valve spring or stuck valve? ... valve fractures piston... oiling, excess unburned fuel, and loss of compression.

Stuck/dropped/broken valves seem to be the most common catastrophic failure on this engine. Not that it's an epidemic, but almost the only failure that happens.
 

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unlucky , I know you worked hard on this engine ….RIP
 

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Sorry about that SergheiS. Tough break.
 

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Discussion Starter #13 (Edited)
Unfortunately I'm just about to head out to college, so I won't have the time to pull the motor to examine it. If I pull it upon return I'll report what I find, maybe fix the rear head/piston. All I know, before this happened, it would burn more oil than it should out of the rear cylinder, and now that cylinder has absolutely zero compression. It got me home running on one, so I'm honestly not even that sour about it. Either way, for now it'll just have to sit and rest until I decide what to do with it.
 

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you may only have a valve problem so its worth checking as it will be just top end fix if it is .
 

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Discussion Starter #16
Now that I recall, when I looked into the spark plug hole with a flashlight, one of the valves was clearly visible, coming down lower than the others. I don't know if this is normal or not, someone fill me in?
 

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Sounds like it dropped a valve then, could just be a broken valve spring.
Both valves of a set should drop the same amount. if just one is lower, then it has a broken spring or snapped shaft.
 

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Discussion Starter #18
Well, I was debating on pulling the motor to fix it up, but, after looking up the parts I might need, and seeing how much work is required, I decided to just get another bike. Just brought a 2008 Nightster home, registering tomorrow. Far as the 750 goes, if I can't sell it, I'll part it out. If anyone here wishes to buy it for parts/fix up, it is located in Westchester NY, just PM me. You can get half the story of this bike through my posts.
 

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Discussion Starter #19
Well, in closure, I had finally taken the motor apart as I was parting the bike out. Indeed, one of my valves was stuck in the open position. And that is how the motor died. I'll upload a pic if anyone's interested.

Not sure how common this problem is, and most of my problems with this bike related to cooling/electrical, but, this is how it finally ended its life.

I know this thread is ancient, I've been gone a while & didn't get a chance to do anything with it, but figured I'd let everyone know what happened. Despite the work I've done on this bike, most of its tech/engineering remains a mystery to me...
 

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Bummer! But thanks for the feedback. It's always good to know the rest of the story.
 
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