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subs1000w
07-22-2007, 09:06 PM
i just picked up a deere hd75 for 250 that had a blown motor but the guy included a briggs engine that he garanteed was good but i cant find any modle #s or hp no nothing but it looks alot like my 14.5hp on one of my riders which is a really common single cylinder ohv engine anyway i get it bolted down and the pulleys all on and tryed to jump start it and the starter will only turn to the compression stroke and then stop it doesnt have enough tq to overcome the compression so i swaped the starter with the one off my 14.5hp which works fine on it and it does the same thing ive also tryed jumping from 3 diffent batteries thinking mayby one was weak so i dont thing thats it either and it turns over fine with the spark plug out any ideas thanks

Restrorob
07-22-2007, 09:54 PM
The automatic compression release is not working properly most likely due to the valves needing adjusting.


Remove the valve cover then rotate the engine over by hand until you reach top dead center compression stroke, Then remove the spark plug. Once at TDC insert a small screw driver in the plug hole touching the piston and rotate clockwise past TDC until you see the screw driver move down inside the hole 1/4".

Now loosen the jam screw in the center of the adjustment nut and adjust to .005-.007" both intake and exhaust. Hold the adjuster nut with your wrench while tightening the jam screw. It may take a couple times to get it right because when tightening the jam screw it could throw the adjustment out so check after tightening.

Once you get the valve cover off look at the bottom side and the model type and code numbers will be stamped in it.

khouse
07-22-2007, 10:45 PM
I wonder if your engine got oil or gas in the cylinder while being stored? This would hydraulically lock the engine as the oil would not compress. With the plug out and cranking does it spit out any oil or gas?

Restrorob
07-22-2007, 10:54 PM
Forgot to mention, Should you pull the valve cover off re-install it with the numbers facing up like their supposed to be.

khouse
07-22-2007, 11:19 PM
I didn't read where you removed the plug - my mistake. After cranking it over without the plug in it did you then reinstall the plug and have the same issue?

petez
07-23-2007, 01:36 AM
Sounds like the exhaust valve is not opening, it compresses after intake opens and when comes up again to exhaust and it is recompressing air that should be exhausting. Make sure the exhaust valve is opening and the muffler is not obstructed

subs1000w
07-23-2007, 12:01 PM
i just adjusted the valves the intake was fine the exhaust was 002 so i adjusted it to 007 and i also removed both pushrods to make sure they werent bent and there fine and i also turned the engine over by hand and both valves are opening fine so the cam should be fine but i put it back together and the same thing i can turn the engine over by hand its hard but its not locked up and theres no rough spots the exhaust is not obstructed although i guess i could remove the muffler to make sure but i dont think thats the problem

also there are no numbers anywhere inside or out on the valve cover it just has the briggs logo and says OHV so it cant be put on upside down

any other suggestions thanks

Restrorob
07-23-2007, 01:12 PM
Did you position the piston at 1/4" past TDC compression stroke before adjusting the valves ?

I have seen the same problem you are having way too many times, If the adjustment didn't solve the problem then there is most likely a problem with the mechanical compression release on the camshaft.

Also, If one closes their eyes (sees no writing) this valve cover will in fact go on up side down. Some one has replaced this valve cover along the way is why there are no numbers stamped in it.

subs1000w
07-23-2007, 04:22 PM
i went roughly 1/4in past tdc

has the adjustment always solved the problem for you or have you ever had to go further into the engine thanks

Restrorob
07-23-2007, 06:00 PM
I have only had to go inside of a few, For the most part adjusting solves the problem. I have two units in the shop as I type with the same problem you have, My plan is to do as I suggested to you and check the valve adjustments.

If the adjustment doesn't solve the problem then I will remove the spark plug and valve cover, I will then rotate the engine clockwise slowly by hand and watch the intake valve rocker arm.

As the piston goes down the cylinder the intake rocker will open the valve, Once the piston gets to the bottom of the cylinder then starts back toward the top of the cylinder the rocker arm will let the valve start closing. The valve will close completely before the piston reaches full TDC.

Just before the piston reaches TDC the rocker arm will bump the intake valve back open just a little. This is the compression release working, If the rocker arm does not bump the valve back open there is a problem with the release arm on the camshaft which will require removing the sump (pan) for further inspection.

subs1000w
07-23-2007, 11:21 PM
ill try that tommarow and see if not ill pull the oil pan and take a look at the cam thanks

topsites
07-24-2007, 10:07 AM
I didn't read where you removed the plug - my mistake. After cranking it over without the plug in it did you then reinstall the plug and have the same issue?

Yeah because if you got the wrong plug it could be that the end of the plug touches the cylinder and blocks it from moving freely.
If in doubt or you're not sure, I'd try a Champion RJ-12YC

John Stiles
07-24-2007, 01:40 PM
Had the exact same problem on a brand new intek 23HP...I'm a spiteful kinda guy, so when the store told me they would hafta send it back, I didn't want to wait...I asked about adjusting the valves and they said it would void the warranty. So...I took both valve covers off and loosened the intake valves to make them open "later/smaller" and tightened the exhaust valves a smidge which makes them open "sooner/bigger" and eh voila'.....she purrs just like a kitten!!:clapping: ~john>>>P/S The guy who first answered your post is absolutely correct in his diagnosis!:usflag: