briggs timing

[DirtTrackRacer_07]

If you have a bent valve, i believe more than likely one of the valves would be slightly open when it should be seated.

So it would not be letting you get enough compression and not burn the fuel enough. That would also explain the back fires.

If you have a piece of air line that has the male course thread end on the end of it, screw it in the spark plug hole and pressurize it to about 80 to 100 psi.

Make sure that you turn the motor over to where the piston would be at the top of the cylinder. You could take both the rocker arms off to make sure both of the vavles are colsed or if you dont think you can set them back you could find the compression stroke.

You will see it when you turn the motor over, watch the valves and stick a small screw driver in the chamber to feel the piston.

Watch the valves close, and you will find the perfct spot, both vavles will be closed and the piston will be round about the top of the cylinder.

Once you pressurize the cylinder, listen for any air leaks out of the intake manifold or exhaust. If you can hear some air, then the vavle is not seated, meaning eithier you have a bent vavle or a bad valve seat.

If it were mine, I would tear it down and rebuild it while I had it apart but its what I like doin.

 

[metalthrashinman]

ok i know it is only on one cylender because i took turns runing one cylender without the spark lead connected when only the lead was connected it ran fine (appart from the niose of a non firing cylender).

the engine is about 4 years old and has done 5611 hours it gets the air filter cleaned and an oil change twice a year.

there is plenty of spark based on the fact that when my dad grabbed the spark lead it gave him one hell of a shock and made him jump back.

im tempted not to pull it apart based on the fact it is very fiddly and i dont like small engines. ill practice on our old mower and see if it is worth the trouble or just take it to the small engine shop and let them sort it out.

Check your exhaust. If you were running the motor with only one spark plug lead attached, the carb is still sraying fuel into the non firing one meaning that you are dumping raw fuel into your exhaust tube; and that can clog it. A clogged exhaust tube of muffler will create backpressure and the motor will perform as you have described. Try taking the muffler off and seeing if it runs okay. It will be loud, but will identify if this is the problem.

5611 hours is not a ton, but considering the way you've been running it; it is a lot... BUT---

Your spark plug wires are probably bad because you should be able to touch them and not get a shock. They are rubber insulated, and when the wires wear out, they will shock you. Try new spark plug wires before tearing the engine apart. Cheap fix if that is the problem, and if that is not the main problem, you need them anyway.

 

[slideways]

I would look into more simple things besides bent valves and such. If this is something that has happened all of the sudden it probably isnt something intensive. Remember this is an OHV motor here. I'm still not understanding exactly what the symptoms are here or that the original poster is even really trying what is being suggested.

 

[Bluethunder3320]

i still cant believe its only 4 years old. there are still briggs going strong from the 60's 70's. do what metal said oh also try swapping the spark plugs from each cylynder to see if that does anything... its just something to try.

i dont have a lot of experience with twin's but last summer my granpa and i pulled an 1982 8hp evinrude twin that sat since 1990 from the shed and dumped some gas in the cyls and ONE pull it fired right up. even the original plugs from 1982.

 

[sideways]

If you've got a bent valve then your valve clearances will be way to big on one valve.

Thanks

Hayden

 

[DirtTrackRacer_07]

Try swapping the coils around from cylinder to cylinder and see if that cures the problem on the missing cylinder.

If the good running cylinder run bads and the bad cylinder runs good its a coil.

I worked on a kohler that started missing on one cylinder out of the blue one day,it would only spark three or four times everynow and again on the right cylinder.

I done the coil swap and found it had a bad coil.

It was on a stump grinder, it ran at a continues rpm most of the time much like a lawnmower.

 

[fowler]

Check your exhaust. If you were running the motor with only one spark plug lead attached, .

i was only doing that to test it it will always operate with two cylenders unless im testing it and the test was only 10 secs of running
dirttrackracer seems to have some good ideas of useing air line and a small air compreser
also i may try swaping the coils around
ill try the spark plug swap first but i dont think thatll change much

 

[DirtTrackRacer_07]

I am about 90% sure that the air line will thread into spark plug hole but if the plug is deep in the head, you may want to get a piece of lengthed pipe with the same thread on both ends and then put you air line onto that.

The reason saying that is the air line that i have swivels on the end and it might be hard to get out if it is in a hole that you can not get a wrench on.

The piece that I use is about is about 10" long with a air fitting threaded onto the end of it.

You don't have to worry about over pressurizing the cylinder because they will hold 100 to 150 psi easy. Thats about what most air small air compressors put out.


Pull the engine cover and trace you coil kill switch wires on your coil and see if they have a burnt spot or rubbed spot anywhere.

If either of the two are grounded out anywhere, it will cause the coil to not fire properly.

 

[fowler]

i just learnt we are starting shearing tomoro so i can do nothing but chase sheep for the the next 4 weeks
dam!!!!

 

[Bluethunder3320]

have fun....

 

[metalthrashinman]

i just learnt we are starting shearing tomoro so i can do nothing but chase sheep for the the next 4 weeks
dam!!!!

Hope none of them stop real short!

 

[lencoo12]

are yes
well i live 130 km out of town so it looks like im not mowing.
but just in case how would i ajust the spark timeing.

i dont know if its possible. your flywheel is factory set with a keyway on the crank and the magneto cant be moved. its already set to blow just past TDC. i dont know what else to do than to take off the head and check the valve seats. usually you can bend a valve back with a hammer.


__________________
watch movies online

 

[Bluethunder3320]

yup but i hop you dont break a HEAD BOLT. grrrrrr i hate those.

 

[fowler]

ok well it rained so that managed to stop shearing and **** up our hay but i was able to take a look at it.
the problems are all very simple but create a huge efect
choke set increctly.
moth in fuel tank, grass in line.
due to incorect choke the spark plugs blackened.
now those issues where my fault
but the the biggest issues are due to the people who serviced it last.
they cleaned the carb and when they put it back on they put the beather tube in the wrong place, so the fly wheel was sucking air from it, conciquently it was sucking all the air from the carb and u all know what that means.
second of all when the rocker cover was taken off some time long ago, the seal was not put back in and the bolts where done up too tight so the seals around them where chewed off so the vaum tube for the fuel pump was not funtioning properly.

so in summery
most of these isues dont explain the symptams or why they all started haveing affect at the same time while it was working.
but realy i dont care as now it is working properly once more!!!!!!!!!!!