OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Chokeomatic sending out fireworks from muffler!

I picked up an old victa from the nature strip and have noticed that there was this black sooting around the back area of the steel base.. i wonder why...

I started the mower up and lo and behold, i get to see fireworks! the muffler seems to spit out healthy sparks on a regular basis with a decent flame ball every now and then when the throttle is released back!

apart from that.. the mower runs great

i do want to sell this mower on ebay but i wouldn't be comfortable selling it as is.

I have trolled through the forums and cannot find anything specific regarding backfiring through the muffler and sparks being emitted. is this even fixable or is it a throwaway mower?

Hi Johno, I don't suppose you could take a video of it running, I am sure the members would love to see it!
As for the fix....Joe Carrol or grumpy may have the answer for you.

hehehe, ill see if i can get a decent video going with my phone, ill try this arvo. then ill need to figure out how to post it.

I would suggest that maybe the packing in the exhaust that acts as a spark arrestor has burnt out over the years, the black soot on the base seems normal on the older victas due to burning a bit of oil, etc over the years.

If there is actual flames coming out the muffler I would be thinking that maybe the exhaust valve is no longer sealing 100% also.

If it isn't burning oil now, there should not be much carbon in the muffler: accumulated carbon from smoke emissions prior to a piston ring replacement usually burns away fairly quickly. If it is burning oil now, there would be blue smoke - especially at start-up.

If it steadily emits sparks without smoke, and puts out a flame-ball when you shut the throttle, I think Joe is right as always: you need to take a look at the exhaust valve seating. This needn't be a big job, but do take care to end up with the correct tappet clearance or your work will be wasted.

hmm, i turned the mower on to record the light show and i could not get it to throw sparks or flame ball away this time.. i wonder what might have happened between today and the previous time? ill take it apart still and check the exhaust clearance just in case.

Lapping both valves into their seats, and then setting the clearances, seems like a good idea. One possibility is that the mower had carbon in its muffler (maybe a second-hand muffler had just been fitted) and the previous owner took fright at the burning carbon and threw the mower away. If so, it is your good fortune, now that you've burned it all out of the muffler. That doesn't really fit the fireball symptom though - a burned exhaust valve makes more sense. You'll know as soon as you look at the valve seat.

Ahhh, Johnno, what a shame we won't get to see the sparks fly!!

Hey guys

i cant seem to find the workshop manual for regarding the exhaust valve work which needs to be carried out, can anyone guide me in the right direction?

thanks!

You can find the B&S instructions here:
http://www.tpub.com/content/recoveryvehicles/TM-5-4240-501-14P/css/TM-5-4240-501-14P_152.htm
and on the following page or two (just use the "next" button at the top right of the page). You may find you need to select a smaller font size if you are using Internet Explorer with default font.

i found this doc a while ago for all B&S engines containing torque settings for about everything.
I have the whole pdf if anyone is interested