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I recently bought a 'Xv700 in showroom condition with 5k miles on it for $900 which I considered a good deal.
I'm a long time HD rider & lots of experience working on old Harleys panheads but no experience with Yamaha bikes.
The bike ran great when I bought it though it was cold & raining when I test rode it so didn't get it really up to temperature. On the way home it fell over against the side boards.. Anyway it ran like crap when I tried to ride it. Start right up, idle great but couldn't make it 300 feet without it coughing & cutting out. Pulled carbs & went through them but just basically cleaning them well. Put back on & bike fired up ran well but same issue of cutting out again. So pulled carbs & took them to a a shop that specializes in British iron but willing to go through the carbs for me. Get them back, reinstall being hyper careful properly mounted with new boots and clamps, new fuel lines, in line fuel filter, & air filter in pristine condition.
So starts up with some effort but smoothed right out and rode great around the block a couple of times. However getting on for longer ride it started back up with coughing, backfiring, & flat out dying. Wouldn't restart so pushed it home & tried starting & fired right up but try & ride it & its right back to same problems.
So what's going on with it, blown front head gasket possibly? Sometimes the rear cylinder will misbehave as well. Kinda perplexed. Bought it for a use as a commuter bike as the panhead is not the best for stop & go traffic.
 

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So what's going on with it, blown front head gasket possibly?
I think that is a BIG stretch.....and based only on your post, you have overlooked some other more basic things.

Like contaminated fuel, blocked fuel line or filter.....a weak battery or maybe not charging......or an electrical connector that is corroded and acts up when hot.
 

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Check out the tank vent too but probably some rust or other crud got knocked loose when it fell over.
 

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Check out the tank vent too but probably some rust or other crud got knocked loose when it fell over.
The tank is pristine. Fuel comi
Check out the tank vent too but probably some rust or other crud got knocked loose when it fell over.
That was my 1st thought but tank is pristine with no sign of rust or dirt. In tank filter when I pulled the petcock had 0 junk on it. New clear in line filter shows absolutely clean fuel flowing through it. I've been riding almost 4 decades & turning wrenches. Just to be safe I had replaced the whole petcock assembly. The carbs were professionally gone through by one of the best shops in the the northeast. The problem lies somewhere else, possibly electrical or maybe a valve sticking. Electrical was suggested by the shop. My''50 panhead is a breeze to figure out & work on compared to this bike. Thanks for your reply & thoughts.
 

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It is just a little disconcerting to reply to a request like this.......only to find out that about 90% of the pertinent details about the problem were omitted from the original post. :mad:

Note that the tank vent can be sticking independent of how "pristine" the inside of the tank is.

Things need to be tested while it is in "failure mode".
I tend to agree with the shop. Maybe even the alternator is failing and the battery is going low.
 

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Possibly faulty coil/s only acting up when hot...also any other ignition componants doing the same. Get some of that freeze spray used by electronics techs to identify heat affected parts would be my suggestion.
 
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