# 8hp Briggs - locks up-- but runs fine. Why????



## Dogman7 (May 22, 2009)

Hello,
New to the forum here, but hope to gain a lot of info from more knowledgeable people. I am reasonably experienced with engines, but by no means would I claim to be "qualified" as I am sure, at least some of you, are. Anyhow, here's the problem. 

Have an 8hp Briggs that runs great, BUT, from time to time, when I go to pull the starter rope, it won't budge. However, I could take the shroud/starter housing(?) off and move the flywheel by hand, but it would only turn in one direction about a half a round, then it would turn in the opposite direction about the same amount. If I do this 2 or 3 times it will start to turn a completete revolution, reinstall shroud, pull rope, fires right up and runs fine. No knock, no smoke just perfect. Sooooo, after talking this over with a local "higher up" he suggested either hydrolocking from gas or some foreign object was on top of the piston. Dissassembled engine and found some serious vertical grooves wore into the cylinder bore and piston. Incidentally, on the lower side. Yep, needle and seat time. So, polished out scratches, as far as I dared, both cylinder and piston, and reassembled. Cranked and run fine probably dozen times or so. Then it did it again. This time however, it took a certain amount of force to make the flywheel turn, and when it did, I could hear a scraping noise, which after several revolutions went away. The only thing I did not check was the sychro balancer. Could this be it ? Or, is it simply the rough bore and the rings are catching on it? This thing has just about run me crazy and I believe this is where I have to stop working and listen to some people with experience. Any help would be greatly appreciated. Thanks for listening.:beatdeadhorse:


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## LowRider (Dec 23, 2008)

!. Buy a honor, i think there like 15$ bucks. goes right in a drill
2. Never try to polish a piston, just replace.
3. If the cylinder was really bad just replace along with piston/rings and what not.

My thoughts is its probably gone, so buy a new head and piston/rings and what not


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## pyro_maniac69 (Aug 12, 2007)

check your crankshaft also, sounds like it might have a bad spot in it


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## Dogman7 (May 22, 2009)

Thanks for the replies. 

This is an aluminum block, not an I/C w/cast iron sleeve. While I understand the logic behind the hone, would it not be necessary, if you hone it, to replace with oversize rings? Because aluminum cuts fast and if I were to hone it enough to take out the vertical scorings, I believe I would be way oversize. 

As to the crank, I did not mike the journal for concentricty, but the rod journal looked virtually new. Besides, since it made a scraping noise, that would definitely show up in the rod journal. 

Suppose I will have to tear it back down and take another look........ I'll post the results.....

Thanks guys!


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## HVNFNYT (Feb 13, 2009)

If this engine has a charging system, you may have a loose magnet on the underside of the flywheel, or a piece of foreign material trapped in the magnets.


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## LowRider (Dec 23, 2008)

Dogman7 said:


> Thanks for the replies.
> 
> This is an aluminum block, not an I/C w/cast iron sleeve. While I understand the logic behind the hone, would it not be necessary, if you hone it, to replace with oversize rings? Because aluminum cuts fast and if I were to hone it enough to take out the vertical scorings, I believe I would be way oversize.
> 
> ...



really depends on how much you have to hone. i will only hone a cylinder a little myself. if i have to use oversized rings i call it a day and just replace the cylinder but thats because i can't get or order parts from after market dealers.


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