86 XR600 Carb or ignition?

My friend just bought a used 86 XR600 and is trying to get it running. He had a poor spark and replaced the coil. Improved it. We took apart both carbs yesterday and cleaned them and checked float levels. Now the bike starts and runs but will not rev any higher than mid range. Motor stutters and backfires. Seems to run ok idling or running with the throttle open 1/4 to 1/2. We're trying to figure out if we have a timing problem or a carburator problem. Any suggestions?

Got it found and in the process of fixing. Turned out to be a broken cam shaft. Only one intake and one exhaust were working properly. Hopefully that's all that is wrong....

km-How the hell did he brake the camshaft??!!!! :):D:D

How much did your friend pay for his 86 xr 600? I'm trying to sell one that does run but don't know how much to ask for it?

He paid $800 for it. Thought it was a good deal and still do. Don't know how the cam got broken. I'm thinking sticking valve. One of the exhaust rockers has a pretty deep grove worn in it where the cam lobe hit it. The guy he bought it from said the piston and ring were just replaced before he parked it about 2 years so that may be the ultimate cause. We sent the head out for valve and any milling work. There was a problem with the coil which we replaced and the carb was pretty well varnished from sitting around for 2 years and we got that cleaned up. Still going to replace the jetting. The rear wheel and swing arm is a little loose but that may just be bearings. We'll inspect those next. Tranny and clutch seem ok. We'll check those as well later.

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