Briggs-Stratton Quattro

Re: Briggs-Stratton Quattro
Seven-yr-old MTD 22" rear-bagger. 4 hp Briggs-Stratton Quattro, well maintained, doesn't smoke, oil level fine, carb is clean in/out, air filter has been cleaned.
Motor starts fine, than it revs up, then nearly dies, then revs up, then nearly dies, etc etc. It -does- carbonize spark plug electrodes ("black plug disease"), and I thought that was the problem, but when I put a fresh plug in, it ran the same as with the black plug.
Anybody got any idea what might be going on?
TIA, Puddin'
****************************************************** *** Puddin' Man PuddingDotMan at GmailDotCom *** ******************************************************;
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Likely a sticking float , clogged jet or airleak . probably time for a carb cleaning.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
All carbs have a fuel bowl and float system or you would have a direct flow of gas into the motor filling the engine completely with gas till it would run out the carb and exuast, even filling the crankcase to all gas. The fuel bowl is not in the tank.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
This often happens when the speed regulator (governer) doesn't work right. These engines have air vanes, and often times a squirrel or some other critter has made a home inside, and the nest blocks the vane.
Take off the top cap (around the spinning part on the top, where the pull cord goes in) and I bet you find it. I used to do this every spring to mine.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
ive seen many of these with the small passage in the fuel bowl nut clogged. you can take the nut off and use a needle or a tag wire to run thru it and then blow it out. this is also a good time to take the fuel bowl off and was it out. if you still have a problem after this. i would snug up the head bolts, check the flywheel key to see if its partially sheared. there is a oring that goes on between the engine and the carb that may be worn,, or the tube that the oring goes on may be worn ,and a gasket on the other end of that tube that may have blew.its easy to check the intake tube while your checking flywheel key. ..... another common problem is the valve clearance closes up so the valves dont shut as well. you can use a file between the lifter and valve stem to get the clearance back where it should be..006 intake,,,.011 ex.at top dead center.. lucas.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 20 Apr 2005 14:20:56 -0400, snipped-for-privacy@webtv.net wrote:

To repeat, it is a B&S Quattro, 4 hp.
I could find no fuel bowl nut.

Fuel bowl is part of the gas tank. Can't take it off. But I cleaned it out. Wasn't very dirty, minimal residue only.

Head bolts were tight.
It fouls spark plugs. Gotta be a fuel/air mixture problem. Carb/tank is all clean, no apparent problem. Compression feels a little weak.
Still don't know what the problem is ...
Why do I see so many B&S mowers sitting in the alley waiting for the trashman? They are made to be lo-price. To my knowledge, "They Ain't Much Designed To Be Worked On".
Thanks, Puddin'
****************************************************** *** Puddin' Man PuddingDotMan at GmailDotCom *** ******************************************************;
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
hi, if you have the type carb that has a flat gasket between it and the tank,, that rubber gasket can cause it not to run if it gets streched.. lucas
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 20 Apr 2005 14:03:03 GMT, snipped-for-privacy@Gmail.com (Puddin' Man) wrote:

Last week had the same problem with my 10 year old murray with B&S 5hp Quattro. (Lets remember that these engines have a 250 hour life expectancy from B&S) Mine ran/runs great and hated to throw it away just because I left some gas in the carb over the winter. Self propelled costs around $300 to replace.... now it looks like I'll get at least another season out of it..
You'll need to google +"Briggs & Stratton"+Quattro or go here and look for Engine IPL (illustrated parts list) to see the breakdown http://www.briggsandstratton.com/display/router.asp?DocIDd103
You'll need the model of engine (not mower) it will be on shroud that covers flywheel stamped in the end just above the spark plug. You'll have to remove some "stuff" depending upon your model to get to this number.
Once you find the B&S web site, search for that model number. You'll end up with probably a .pdf file showing breakdown of engine.
Note that there is probably more than one model carb for your engine , you'll have to figure which one. Usually asks, do you have choke or primer bulb.
On mine (which may vary quite a bit from yours) I had a bolt in bottom of carburetor bowl which acts as a jet. Using carb cleaner and very fine wire (I used safety wire) clean the gunk. Clean the gunk from needle and seat under (above) the float. My "carb to intake" seal is a "O" ring.... Looked fine. I had to take carb off, put back on 3 times till I decided to put a little gasket sealer on flange near "O" ring to help seal. On these engines a little vacuum leak will cause it to not suck gas.. Till I found this air leak, mine would run great as long as I kept pressing primer bulb.
I spent $8 to fix mine including oil change and pull rope change.. If it wouldn't have worked after that,, I'd have dumped it.. It being 10 years old.... Chuck
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Is this 250 hour life true of the older B & S engines? If so I have several living in the twilight zone. But then I guess that figure must be an average.
Colbyt
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 25 Apr 2005 15:44:09 -0400, "Colbyt"

I saw the 250 hour figure on the b&s web site,, but now older ones are probably different.. Modern ones ya can't even adjust mixture (but no need to if it's already right.) No idle speed screw.... Chuck
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
250 hr is till it will pollute due to worn rings you may get 100-250 more hours than that you may not. There are higher hour rated motors by B&S 500-1000 for example but it a true indicator of a motors construction and durability .Using the EPA rating is a good way for you to compare a motors life expectency. B&S and others even honda have a light duty and commercial service line. Honda used to be only Commercial duty but now has the cheap line to.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.