# YS 4500 (917.27664) engine questions



## JEM1947 (Apr 14, 2011)

I bought a used YS 4500 with the B&S 20hp single cylinder engine with about 100 hours on it. The mower cuts, mulches and bags great but the engine is a puzzle to me. 
1. On cold starts it seems to be searching for a stable idle but can't find it. It runs fine when the rpm is raised.
2. When turned off it seems to flood easily.
3. Sometimes it will back fire when turned off at a higher rpm.
4. Dang muffler is really loud. Are they any quieter when new?
5. Is there a washable air filter available for this engine?

Any suggestions are appreciated!
Jim


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## dangeroustoys56 (Jul 26, 2010)

More then likely most the issues you described are caused by the carb. Newer motors have a 'antifire' solenoid ( to shut fuel flow off when its shut down)- either that can be acting up and not working right or the carb needs a good cleaning. Probably wouldnt hurt to check the plugs either. You also might want to do a tune up- fuel filter, whole round.

Personally ive bypassed the antifire solenoids by snipping the retractable pin off with side cutters ( and putting it back in the carb) and just adding my own fuel shut off valve- my 2003 murray would diesel something firece when it was shut down, and also run and idle rough- after the solenoid 'adjustment' it runs and shuts off normal. Id hate to see what a new one costs.

If you have the room, you could mount a small car or dirtbike muffler - be cheeper then a new tractor muffler - or a cheep way out : earmuffs or ear plugs.


the only filter i know thats washable is a K&N type filter- see if an auto parts store could match one up to yours- it wont be cheep initially tho.


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## JEM1947 (Apr 14, 2011)

dangeroustoys56,
Thanks for the feedback.

When the solenoid is "clipped" will the float behave as in an older non-solenoid carb? Bypassing the solenoid doesn't affect anything else?

What type fuel shut off valve did you find to use?

And I will do the tune-up as suggested.
Thanks,
Jim


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## wjjones (May 28, 2010)

JEM1947 said:


> I bought a used YS 4500 with the B&S 20hp single cylinder engine with about 100 hours on it. The mower cuts, mulches and bags great but the engine is a puzzle to me.
> 1. On cold starts it seems to be searching for a stable idle but can't find it. It runs fine when the rpm is raised.
> 2. When turned off it seems to flood easily.
> 3. Sometimes it will back fire when turned off at a higher rpm.
> ...


 Are you sure its not a twin cylinder??
1. Mine has done this since it was brand new.
2. Cut it down to the lowest idle position for about 20 seconds before shutting it off.
3. Turning it off before idling it down is what causes it to backfire that is in the manual.
4. Mine is pretty quiet you may need to buy a new muffler or clean out the spark arrestor.
5. Wash the pre-cleaner (green foam) and blow the other out with air.
6. Welcome to the Forum!.. I hope this helps you if not let us know..


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## JEM1947 (Apr 14, 2011)

wjjones,
Thanks and it is helpful. I'll give the advice respect and give it a try.
Best regards,
Jim


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## wjjones (May 28, 2010)

JEM1947 said:


> wjjones,
> Thanks and it is helpful. I'll give the advice respect and give it a try.
> Best regards,
> Jim



Your Welcome.. I wondered if you got a chance to see if it is a twin, or a single cylinder..


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## wjjones (May 28, 2010)

dangeroustoys56 said:


> More then likely most the issues you described are caused by the carb. Newer motors have a 'antifire' solenoid ( to shut fuel flow off when its shut down)- either that can be acting up and not working right or the carb needs a good cleaning. Probably wouldnt hurt to check the plugs either. You also might want to do a tune up- fuel filter, whole round.
> 
> Personally ive bypassed the antifire solenoids by snipping the retractable pin off with side cutters ( and putting it back in the carb) and just adding my own fuel shut off valve- my 2003 murray would diesel something firece when it was shut down, and also run and idle rough- after the solenoid 'adjustment' it runs and shuts off normal. Id hate to see what a new one costs.
> 
> ...


 I had a sears tech tell me about this trick of cutting the fuel solenoid, and that is good advice dangeroustoys56 i would also do a complete tune-up. I use ear muffs because it does seem louder than it should be. I almost had to fight a guy over the loud mower one day he didnt like it either, but thats another story..:lmao:


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## JEM1947 (Apr 14, 2011)

wjjones
It is a single cylinder B&S model 31P977, type 0670-E1.

So you guys think cutting the solenoid is the way to go?

Thanks again.


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## dangeroustoys56 (Jul 26, 2010)

I just used a standard plastic fuel shutoff ( i manually turn it on and off) in the fuel line before the fuel filter - all the solenoid does is to stop fuel flow ( when the key is on it retracts- when its off it extends)- doesnt affect anything else. First one i saw was on my '94 murray with a 14.5HP single OHV briggs motor- i swapped on a different carb. 

I tired literally everything to keep my 2003 murray ( it has a 16.5HP single OHV briggs) from dieseling, idled it down for 10 mins, cleaned the carb , changed the plug - before i did the snip it would just quit while mowing and run extremely rough , not to mention was also really hard to start.

I have a habit now to shut the fuel valves off and let the tractors run till the carb is out of gas ( couple mins)- some of my carbs leak gas by , just havent had time to get rebuild kits for em.

I forget where i first herd about 'modding' the solenoids - i think when theyre new they work fine, just as they age is when the issues begin.


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## wjjones (May 28, 2010)

JEM1947 said:


> wjjones
> It is a single cylinder B&S model 31P977, type 0670-E1.
> 
> So you guys think cutting the solenoid is the way to go?
> ...



Like dangeroustoys56 said you just have to get used to remembering to shut the fuel off when done. The sears tech i mentioned advised me (un-officially) that if mine had trouble again to snip the fuel shut off plunger..and install a manual shut off..


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## JEM1947 (Apr 14, 2011)

What puzzles me a little is, for years we have lived with a simple carb bowl float/neetle valve that shut fuel off as needed. Wondering why the solenoid in the first place. Seems the newer ones should work without the solenoid or shut off valve. What am I missing?
Just curious, trying to learn.
Jim


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## wjjones (May 28, 2010)

JEM1947 said:


> What puzzles me a little is, for years we have lived with a simple carb bowl float/neetle valve that shut fuel off as needed. Wondering why the solenoid in the first place. Seems the newer ones should work without the solenoid or shut off valve. What am I missing?
> Just curious, trying to learn.
> Jim



Because it can siphon into the engine when its sitting, and you end up with a crankcase full of gas..


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## dangeroustoys56 (Jul 26, 2010)

Wjjones:


> Because it can siphon into the engine when its sitting, and you end up with a crankcase full of gas..



Had that happen a few times ( before my tractors all got shut off valves) - I caught it before i fired it up tho. Running the motor ( if itll start) with gas in the oil will ruin the berings - itll thin the oil out. 

I do a ritual when i mow- check the oil ( if it seems a bit high or watery i check for gas in the oil), turn the gas valve on and fire up the tractor- when im done- i shut the valve when its running and let it stall - that way the bowl is 'empty'- if any extra fuel seeps by itll just sit in the bowl and not flow into the combustion chamber.

Another plus of the valve is when i fill up the gas tanks- i make sure the valve is off , so it doesnt put extra pressure and possibly over flow. 

Putting the valve before the fuel filter also saves from emptying the tank to change it .


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## JEM1947 (Apr 14, 2011)

dangeroustoys56,
Where did you buy your valve? Do you have picture maybe?
Thanks,
Jim


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## wjjones (May 28, 2010)

JEM1947 said:


> dangeroustoys56,
> Where did you buy your valve? Do you have picture maybe?
> Thanks,
> Jim


 They have them at TSC, and maybe Lowes,etc..

Briggs & Stratton® Inline Fuel Shut-Off Valve - 4442416 | Tractor Supply Company


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## dangeroustoys56 (Jul 26, 2010)

I bot mine at Advance auto and a flea market actually .


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## wjjones (May 28, 2010)

dangeroustoys56 said:


> I bot mine at Advance auto and a flea market actually .


 Yep i didnt think about that dangeroustoys56.. And possibly Autozone..


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## dangeroustoys56 (Jul 26, 2010)

Yepper- most autoparts stores today carry a small section of lawntractor parts - my dad gets his from Napa .


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## JEM1947 (Apr 14, 2011)

Got it at Lowe's.
I'll post with the after install results. May be a week or so.
Thanks Guys.
Jim


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## wjjones (May 28, 2010)

JEM1947 said:


> Got it at Lowe's.
> I'll post with the after install results. May be a week or so.
> Thanks Guys.
> Jim



No problem.. glad to see you found what you needed keep us updated, and dont be a stranger..


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## formationrx (Sep 6, 2012)

i have seen where people have just put a bolt and washer in place of the solenoid... what i dont understand is ... if you are plugging the hole... how is the engine getting gas? seems if the solenoid stops the flow when the key is turned off... arent you stopping the flow by plugging the hole with a bolt and washer? what am i missing here?


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## dangeroustoys56 (Jul 26, 2010)

Its actually easier to just snip the end of the solenoid off and put it back in, just unhook the wire to it.

Earlier carbs before the solenoid used a short bolt to hold the bowl on - the fuel would flow into the carb thru holes in the sides of the threaded section - w/o looking at a couple of my carbs- couldnt tell if it would work or not - itd have to have holes in it to work.


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## Bill Kapaun (May 8, 2007)

Manual says to place the throttle between 1/2 & full to shut off engine.

Fuel solenoid has absolutely NOTHING to do with the float.
it's just a retractable "pin" that blocks the MAIN JET.
It has NOTHING to do with fuel ENTERING the carb bowl.
LOOK at an IPL for the engine. .You can SEE it has nothing to do with fuel filling the carb bowl.

On cold starts, you probably are taking it off choke too soon.
These carbs are jetted (too) lean and a cold engine requires a richer mixture. Pre EPA, carbs weren't jetted as lean, so cold performance wasn't quite as bad as the newer types.
(The choke is there for a reason)


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