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View Full Version : how to time a 8 hp briggs engine



hotroddal
06-10-2006, 09:46 PM
how do I time a 8hp briggs engine, thats all i need to know?
thanks hotroddal

MTS
06-10-2006, 09:58 PM
You talking cam/valve timing? Theere should be a little mark on the cam-shaft gear and the crank you have to line up when the piston is at TDC.......with the flathead brigs anyways.

hotroddal
06-24-2006, 11:06 PM
is there any way to tell if your engine jumped time or is that possible for it to jump time.

85ytz250n
06-25-2006, 12:02 AM
It would have to have the teeth on both the crank and the cam worn to almost nothing. The timing marks have to be lined up, the timing mark on the crank will be tdc and the timing mark on the cam will be bdc, now all that means is the marks will be like this : I have never seen a 5hp jump time, havent worked on but a couple 8hp so I cant tell you 100%. I hope this helps.

Barry

hambone
06-25-2006, 07:42 PM
i've never seen a briggs jump time.
has it thrown a rod before?
you may have a stuck valve , briggs is notorious for valve sticking.

hotroddal
06-25-2006, 09:24 PM
it has never thrown a rod before, im not sure if it has a stuck valve , is there a way to check if the valve is stuck?

85ytz250n
06-25-2006, 10:31 PM
You can pull the head off, and turn it over by hand. Unless it has the OHV and then you would have to ask someone else, I am more knowleadgable about the older briggs. Pulling the head is no big deal, just remember which bolts come from which hole cause there are different lenghts. What are the problems you are running into with this engine that makes you think it jumped time?

Barry

corndawg
06-26-2006, 12:19 AM
make sure the key on your flywheel isnt sheared or partially sheared, that will make the magenents on the fly wheel pass over the armetuer at a different time, therefore jumping time

hotroddal
07-03-2006, 11:17 AM
what problems I am having is that the engine wont start it has great spark, and is backfiring and spitting gas out the air intake on the carb, so i thought it may be the timing that is off.

hambone
07-03-2006, 02:03 PM
flywheel key is broke and the ignition timing is 180 degrees out.
pull the flywheel and put an new key in and make sure the flywheel nut or starter clutch is real tight or it will just shear the new one.

hotroddal
07-03-2006, 04:23 PM
thanks for the help, i will go and pull the flywheel and see if the key is sheered.

MTS
07-03-2006, 11:56 PM
Sounds liek a stuck intake valve to me....i have NEVER seen a brigs Shear a Flywheel key, im sorry but unless your running on alky, it dont happen....lol

200m
07-04-2006, 02:17 PM
hi. it could be the flywheel key and they do shear if a heavy load is put on right away it causes the flywheel to keep going so it shears. and yes all engines can shear the flywheel key. if its backfiring and spitting gas its the key. ive had that problem before and i put a new key in and it started right up

hotroddal
07-04-2006, 02:50 PM
well I took that mesh screen off the flywheel and that aluminum piece that it screws to off the flywheel, and it doesnt look like the flywheel key is sheered, is it possible to tell if it is sheered just by looking at it or will I have to pull the flywheel?

hambone
07-04-2006, 02:57 PM
they are bad for imprinting a small score on them.
i'd pull the flywheel to check it out.
i've had many do this.
if it pops and spits bad after starting you'll have to do a valve job.
most likely a burnty valve then.
hope you find the problem

hotroddal
07-04-2006, 07:24 PM
well if this helps any it isnt very hard to turn over, but when running it would run strong and started right up, all that happened is that it just quit running.

85ytz250n
07-04-2006, 09:21 PM
You need to pull the flywheel and replace the key if it is sheered. If it isnt sheered then pull the head and unstick the exhaust valve. Put your hand by the exhaust and pull the starter, if you feel exhaust gas being vented then it is something else. If there is no exhaust gas being vented then you definetly have a stuck valve. If the valve is stuck closed then it will be hard to turn over and you will probably bend the valve. What is the motor on?

200m
07-05-2006, 12:37 PM
he said it was just running then stoped so how would the exuast valve be stuck they cant just get stuck when its running? only when it sits for like years.

NewOldSchool
07-05-2006, 01:19 PM
these briggs motors...you gotta take off the flywheel sometimes to check the key...that washer makes it look like its still good but its not.....you could have fouled a plug or have low compression did you check that?

hotroddal
07-05-2006, 05:03 PM
well, ive replaced the sprk plug and ive pulled the flywheel and the key isnt sheered, its in perfect shape, but the thing is it always ran strong and started good, but I was just mowing the lawn with it and it quit running, ive cleaned the car, changed the plug, checked the flywhel key so are you guys leening towards a stuck valve?

MTS
07-05-2006, 08:48 PM
As i said, stuck Valve, Brigs are notorius for it, Valve face's get worn, dont cut the carbon and it gets stuck in the guide....iv torn oodles of them apart...with this problem..

hotroddal
07-07-2006, 04:58 PM
well I took both the carb and th muffler off and turned the engine over and both the exhaust valve and the intake valve are opening and closing, I thougherly cleaned the carb , and tried adjusting it but it still wont do anything, it has great spark, and is getting gas to the carb and the cylinder, i just cant figure this thing out.

hotroddal
07-10-2006, 06:43 PM
any idea of what could be wrong????, I really need the help here.

hambone
07-10-2006, 08:11 PM
have you pulled the head to be sure the valves are seating.
sometimes the valves will stick but still move up and down.
what brand plug are you using.
briggs engines only like champion plugs.
i'd use a J19LM or # 845 champion and gap it at .025".
you'd think it won't make a differance but i've made a lot of owners believers.
if this engine has points igniton gap the points ( under the flywheel) to .020".
you could possibly had a bad condenser or a burnt set of points.
i don't remember the part number, but you can change the coil and do away with the points.
this is what i usually do for my customers.
i'd check the valves and go from there.

hotroddal
07-16-2006, 11:51 AM
if the points were burnt out would there still be spark, becuase the engine still has spark?

sblt500r
07-16-2006, 09:45 PM
did you pull the head? the valve seats in briggs, on the exhaust valve mainly will pop out and hold the valve open. try this, put your finger over the spark plug hole and spin the engine over. your finger should get blown off the hole.

hotroddal
07-17-2006, 07:25 PM
ok ill try that, thanks for that tip.

hotroddal
07-17-2006, 07:29 PM
I just whent outsaide and put my thumb over the hole and there hardly is any pressure, i can keep my thumb on the hole for as long as I want., so now what do you think th problem is, when it was running it didnt smoke and always started easily?

sblt500r
07-19-2006, 12:41 PM
well first check the tightness of the head. i know thats not a word! the bolts near the exhaust ussually loosen up. if there loose then tighten then and try to start it. if it doesn't start, or the bolts weren't lose, pull the head. and look for a valve seat that came out or carbon build up.

hotroddal
07-19-2006, 03:23 PM
all of the head bolts were kinda loose I got about a half a turn out of each but it still wont start so what do I do now?

sblt500r
07-19-2006, 08:58 PM
you either blew the head gasket or a valve seat popped out. your going to have to pull the head off. if its not a steel gasket you need a new one.

hotroddal
07-20-2006, 11:52 AM
thanks for all your help on getting my mower back to run, what happened was a valve seat had popped out so what I did was pop it back in and it fired up.

hotroddal
07-20-2006, 12:31 PM
well i whwent to go mow the lawn with the mower today and it did the same thing, the valve seat popped out again, when I had the head off, i noticed the area around the valve seat was scored up, so do I need a different head to correct the problem, becuase the seat keeps popping out.

sblt500r
07-20-2006, 02:15 PM
once it pops out thats it. thats a bad design on briggs part. if you just push it back in it will just pop out again. you can try this, but if it doesn't work you need to get another engine, or a short block. get a center punch and hammer and prick punch around the seat after you push it in. the prick punching will push the aluminum tighter round the seat, in turn holding it in. it does work, i've done it before, but there is no gaurantee that its a permanate fix. it does work for awhile, if done right.

i see i was the only one who new about valve seats popping out on brigg's. i think i've been doing this for too long, and i'm only 26:lol: