Way off topic: bent B&S exhaust valve

[brokeasajoke]

Bad gas, after sitting with old fuel which smells like varnish it will coat the valve stem and bind the valve open allowing the piston to smack it , this is a bi-product of ethanol ,use stalbil if the fuel can not be drained if it is to sit without being run at least twice a month

How does it affect the exhaust valve? Not denying just learning.

 

[brokeasajoke]

Lead will not completely burn off during combustion and it coats the valve stem and acts as a lubricant With newer fuels that do not contain lead you have less lubricant

So maybe some lead additive tetraethallead or what ever it is occasionally in the b&s engines?

 

[hogpatrol]

B&S used to make decent engines. From this chair, buying parts from China and assembling them here is the root cause of all their recent ailments.

 

[338 dude]

So maybe some lead additive tetraethallead or what ever it is occasionally in the b&s engines?

Just buy some and use it in your fuel every time as it takes time to build up a decent coating you will have better results than just using it occasionally

 

[338 dude]

And as said earlier always use a high-quality oil it is even more important in an air cooled engine they run much hotter than a water cooled engine

 

[Cecil S.]

Run synthetic oil and good gas and your engine problems will lessen.

Grandfather had a Lawn mower repair shop we rarely had this problem back in the leaded gas days. Like hog said synthetic oil and leaded gas will extend the life of your engine. Oil is the life blood of an air cooled engine. Good advice on here.

 

[butchlambert]

After reading all of this, I would highly recommend you go to a reputable mower shop for the real answer. High octane fuel will do nothing for a mower.

 

[alby280]

Every other tank full of gas run some marvel mystery oil in the gas and most problems will never happen again.Sea foam also works.

 

[alby280]

Carbon is a biproduct of the combustion of fossil fuels we use today but depending on the combustion temperatures carbon build up will more with lower temperatures or rich air to fuel ratios.Need to adjust your air fuel ratio to help with the combustion temps.

 

[brokeasajoke]

After reading all of this, I would highly recommend you go to a reputable mower shop for the real answer. High octane fuel will do nothing for a mower.

True but your higher octane fuels "usually" contain more cleaners for deposits and I believe that is the reason for that advice. Mom and pop stores may not contain those cleaners but around here your ethanol free fuel are normally in the higher octane fuel. On a side note, swapped the head and got it going. Broke a rockerarm adjusting nut from the used replacement head so I had to replace it and do a valve adjustment out in the yard.

 

[Dusty Stevens]

Higher octane fuels cause detonation unless you adjust the timing accordingly. Do not run more than 87 octane in there and no additives that retard the burn rate even farther

 

[brokeasajoke]

^^^^^^^

 

[luckeeshot]

How does it affect the exhaust valve? Not denying just learning.

if the fuel is bad as I think it doesn't burn clean unburnt fuel collects everywhere on piston rings, wrist pin and both valve stems anyplace , exhaust because it runs hotter and gets all the crap on the way out so when it shuts down it drys up and looks like black paint or varnish when the next person comes to start it hits the starter it probably was slow at first to turn over then it spins like crazy no compression , I've seen it on all types of vehicles cheap gas don't pay

 

[Twicepop]

When you get it put back together, start using a little Marvel Mystery Oil added to your gas.

 

[brokeasajoke]

Not mine, again I fixed it for friend. Already together and running. I run commercial Kawasaki. I add occasional autotrans fluid in my fuel and have for years.

When you get it put back together, start using a little Marvel Mystery Oil added to your gas.

 

[hogpatrol]

Guys, you can use any gas you want in a small engine but those that run chainsaws for a living use high octane. The cheap, low octane stuff is ok for 30 days. After that, it's junk. I'll add that any additive like MMO or other cleaners reduce octane.

Stihl and Husqvarna recommend the use of high octane unleaded gasoline. Both brands of pro saws are designed to burn fuel rated at 89 octane or higher. Most regular grade fuel has an octane rating of about 87. This is not enough.

 

[hogpatrol]

Higher octane fuels cause detonation unless you adjust the timing accordingly. Do not run more than 87 octane in there and no additives that retard the burn rate even farther

Actually, it's the other way around. Too low of an octane causes engine knock and detonation. If one wants longevity and gas mileage, low quality, spot market gasoline sold at the quickie marts won't give it to you. I've been running high octane gas in all my small engines for eons and some are over fifty years old (Kohler, Cub Cadet 126) and they run without any issues. I don't run it in my vehicles but I do use name brand gas.

Edit: Car gas degrades in about a month. Avgas has a one year shelf life. I've started motors with one pull that had five year old avgas with no additives.

 

[Adam in WI]

Actually, it's the other way around. Too low of an octane causes engine knock and detonation.

Bingo. I don't always buy premium for the mower, but whatever I can get that's ethanol free.

I just replaced a set of pushrods in my Vanguard last spring. Yup, valve guide worked loose limiting rocker arm travel. Dang cute little things; I think that whole darn engine weighs less than an ISX turbo.

 

[brokeasajoke]

Not giving octane advice, knew that would start a gentlemanly conversation. I run a lot of small engine stuff. I use high octane and mixed fuel gets stihl ultra silver bottle. My pro saw gets only that. My BR600 gets only that. I have run sunoco some of my 112 in a pinch if i forgot to fill up. You better run high end mix oil in your high end equipment. Been there done that (oil is oil right or thats what I believed early on) paid the price more than once more than twice sadly more than 3 times. I used to mix 5gal of fuel at a time. I ran great quantities. While you may not run additives or believe in their abilities believe in this. #1 run good oil #2 run good gas especially especially late in the season when it may set #3 clean equipment is happy lasting equipment. #4 mix your 2stroke stuff correct. More oil is not better and for you stroke buffs you know that more oil actually leans the mixture. Empty them out and run'em. #5Cheap gas settin in the carb from Nov to April ain't good on it. #6 maintain maintain maintain and keep records. I keep filter changes, hydro flushes, belt sizes marked in sharpie on the mowers.
I've seen a lot of things and lost engines but actually never seen a bent valve on small engine. And for you guys with Sthil 4mix engines, adjust them valves on your weed eater or backpack blower. Makes a big difference.

 

[jonbearman]

Run non-ethanol gas in it. Use premium oil and change often. I stuck a valve in my snow blower but thankfully it is a flat head. Varnish being the culprit. A lot of gas stations now offer non ethanol fuel for boats and tractors etc. You can look up gas stations in your area on the internet. It is more expensive than the absolute garbage they pass off as fuel today. When I was a kid you could go to Hess and get 101+ and Sunoco had 280 premium which was I think 104 octane with lots of that beautiful tetra ethyl lead in it. I miss the good stuff. I know my Mustang with 10.5 to one compression idles better and has more power on race gas but at over 10 bucks a gallon it is crazy.