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engine troubles

diamondintherough79

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memphis tn
Hi.
okay so i recently purchased a 1979 CB750k bike as pretty much a box of parts, i assembled it got it painted and shined up, everything was good until i tried to spin her over. I checked the voltage to the batt all was well here then i checked the starter motor it was catching and dragging so i rebuilt it after i did that it was no longer catching and dragging, but it still wouldn't spin over, now i have taken the flywheel cover off and manually spun the engine just to see if it would and it did, much to my dismay it will only spin 3/4 of a turn and then catch in both directions, i pulled the plugs sprayed wd40 specialist in each cylinder and soaked it overnight and it is still doing the same thing any clue what might be going on? any tips or insight will be greatly appreciated.




p.s. the rotating assemblies are operating correcting until it catches, no resistance no drag.:banghead:
 
I am a experienced mechanic when it comes to cars and trucks but new to the inner workings of a motorcycle engine. where are the timing marks. how would i go about checking the timing, do you know dirtdigger?
 
Last edited:
First if it will not rotate all the way around and only goes so far in one direction and the same in other direction STOP!!!
You could have a couple things wrong
1. You have bent valves and they are not closing and the pistons are hitting the valves
2. Cam chain broke and it will allow you to move a little in both directions
3. Cams way out of timing and piston hitting valves
Either way if you can take valve cover off in frame if you can and see if you can see a broken chain/sucked in valve
Sounds like motor needs to be looked at
 
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