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Wide open bog

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Any thoughts on this?? Jetting where its always been... 162/62... Was riding all day, pit stop at house, then hard to start... Started after several kicks, big black/gray smoke out exhaust... Cleaned carb couple times, checked timing on hotcam stage 1, 420 kit... Might be a degree or two off, but not a full tooth... Jets look squeaky clean... Air shutoff valve was dirty and i thought deteriorating, but was in better condition than from another known working carb... Mid to wide open, on a stand in garage, i get sputtering and backfire, steady and less than a second apart... Bop! Bop! Bop! Bop! Accompanied by small puffs dark smoke... Thought i was loading a short video, but not at moment apparently...

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Tried the known working carb and experienced the same initial failure as my pit stop.... Not only does it not try to start at all, but I no longer have to use decomp lever... I even disconnected the cable and I can still kick through... I did a leak down test and had 60% compression with hash marks in viewing window... A degree or two turn, making the cam dead level, but hashmarks barely disappear from view, yeilds 100% compression... A tooth either direction makes the cam way out of level, but the proper tooth is not how i remember building it.... It was level with hash marks in window.... Really can't decide if this problem is timing, carb, or decomp related....

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You don't have tight/ riding valves by any chance?

 

Disconnect, or at least verify that the decompression arm is not being pulled. Slightly pull on the lever and roll the kicker, do you feel it in your finger? If so, then the cable is tight, and disconnect to be sure you aren't bleeding pressure.

 

If that doesn't work, then I agree with double checking the valves. Remember to do so on a cold engine (sit for a few hours, or overnight).

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FYI.......When setting the camchain on the sprocket, with the engine at TDC and the sprocket lines level with the head, when you wrap the chain over the sprocket, pull all slack from the front side of the chain before wrapping it over the sprocket, so all slack is on the back side/tensioner side. That way, when installing the tensioner later, it doesn't pull slack out of the front side of the chain and pull the cam sprocket marks off time with the head surface.

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It's been a while since I had one apart. Timing marks are on the flywheel correct?

Is it possible the keyway broke and the flywheel is out of time?

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