Author Topic: small engine help needed (Read 1774 times)

keith44 · « **on:** March 27, 2011, 08:44:13 PM »

I have a tiller I bought new 7 years ago, 6.5 hp Briggs and Stratton overhead valve horizontal shaft. Trouble is itstarts and runs great only until the engine warms up, then it hunts or surges, backfires, and will not run more than two minutes between starts. Am I looking at carb. problems, a vacuum leak, or an overheating issue?

thanks
Keith

blind ear · « **Reply #1 on:** March 27, 2011, 10:05:29 PM »

I had one that had dirt daubber nest under the cover in the cooling fins and it would overheat. Cleaned out the dauber nests and it worked again. It's pretty obvious and easy to see when that is the problem. ear

bilmac · « **Reply #2 on:** March 28, 2011, 01:59:28 AM »

That would be my guess, something clogging the cooling fins. Take off some of the shrouding covering them and have a look. Don't be tempted to leave the tin off, the front of the crankshaft has a fan on it that blows air over the fins and it won't cool right without the shroud.

keith44 · « **Reply #3 on:** March 28, 2011, 06:57:31 AM »

Thanks guys, sounds logical. It's been a solid running tiller until this year

charles p · « **Reply #4 on:** March 28, 2011, 03:33:20 PM »

Check your fuel line between the carb and the tank filter. Could have a split or leak. My small tiller would run great at half throttle, but not at full throttle until we found the split in the intake tube.

hillbill · « **Reply #5 on:** March 28, 2011, 03:38:13 PM »

yu may have to pullthe carb off and giv it a good cleaning and blowing out.thats always where i start with a little engine that ran fine last year.

scootrd · « **Reply #6 on:** March 28, 2011, 03:50:47 PM »

Quote from: hillbill on March 28, 2011, 03:38:13 PM

yu may have to pullthe carb off and giv it a good cleaning and blowing out.thats always where i start with a little engine that ran fine last year.

+1 Dirty Carb.

Sound like you have some buildup.
Did you pinch off / disconnect the fuel line and drain the Bowl before putting it away for the storage months ? You would be surprised at how very little buildup it takes to cause the problem that's occurring with your Tiller. clean the bowl add some fresh gas and run a little stable through it. If you have an air compressor blow out carb orifices.

keith44 · « **Reply #7 on:** March 28, 2011, 04:12:23 PM »

I put sta-bil and seafoam in the tank and ran the tiller for about 10 minutes before storing it last year. When I pulled it out of storage I changed the air filter and pre-filter like I always do, and changed the oil. The fuel line was put on new two years ago and looks ok but it is wet at the barb fitting on the carb. No dirt dauber issues, fuel tank vents correctly, cold it runs best with the choke off, as it warms up I have to "add a little choke" until it gets to half choke and becomes cantankerous. I'll pull the carb later this week and have a close look there

Keith1 · « **Reply #8 on:** March 28, 2011, 08:09:49 PM »

One other thing to check is the vent in the gas tank cap. It's got to be open. Sometimes they get rust in the hole.
Keith

bigbird09 · « **Reply #9 on:** March 28, 2011, 08:37:13 PM »

Something is causing it to not get enough fuel if you are having to run it on choke. If you feel confident in your abilities get you a rebuild kit and go through the carb even soak it for a day or so in parts cleaner, if not have a small engine repair shop do it.

keith44 · « **Reply #10 on:** March 28, 2011, 08:48:58 PM »

gas cap vent is fine Keith, one of the first things I checked. Yes I have rebuilt other carbs in the past, really doesnt seem to act like a carb prob, more a supply problem, or water in gas, except that it starts so easily, even after it starts to act up. Two pulls and it fires up and runs great for about two minutes, backfires or not and dies. Two pulls and it fires right up, runs great for two minutes surges, then dies, then back fires on first pull (due to choke being on I'm guessing) second pull it fires right up. I'm really leaning toward a vacuum leak, that is either vibration or heat induced leak.

At any rate I'm gonna pull the tank, fuel line, and carb and just go through everything.

SHOOTALL · « **Reply #11 on:** March 29, 2011, 02:41:17 AM »

Our generators are treated with stabil but after 4 mos they still get what looks like a jel in the carb bowl. You might want to remove the bowl and clean out. It effects the float or clogs the jet. . I hear there is a product out now that you add in the fuel and it cleans out the jel but I have not used it. The ad says it is at walmart in auto section.

dks7895 · « **Reply #12 on:** March 29, 2011, 03:11:14 AM »

http://www.goldeagle.com/brands/start_your_engines/default.aspx

LanceR · « **Reply #13 on:** March 29, 2011, 04:17:49 AM »

Gas with ethanol in it breaks down much faster than gas without ethanol. For years we used Stabil or similar products and didn't have any issues with engines that were used seasonally or only occasionally. For the last few years we have had many more problems. For seasonal use engines (tillers, mowers, snow throwers etc) the best solution is to run them dry.

If you prefer to use fogging oil when you store them spray in the fogging oil until it stalls and then drain the tank, clean out the float bowl and blow out the carb.

We no longer keep the tanks full on our generators, welders etc. We keep them pretty low and add fresh gas when we use them so there's less gummy crud in them. Heck, we're farmers and enjoy the higher prices for corn due to the federal requirement to use ethanol as an gas additive but I wish ethanol would go away....

Lance

scootrd · « **Reply #14 on:** March 29, 2011, 07:25:37 AM »

Quote from: LanceR on March 29, 2011, 04:17:49 AM

Gas with ethanol in it breaks down much faster than gas without ethanol. For years we used Stabil or similar products and didn't have any issues with engines that were used seasonally or only occasionally. For the last few years we have had many more problems. For seasonal use engines (tillers, mowers, snow throwers etc) the best solution is to run them dry.

Lance

+ 1

SHOOTALL · « **Reply #15 on:** March 29, 2011, 07:31:40 AM »

We use the stabil ( gray) for gas with ethanol its good for about 4 mos , not long enough as we just found out.

Drilling Man · « **Reply #16 on:** March 29, 2011, 12:17:04 PM »

From what i keep reading, you have to use the "marine grade" stabil for longer lasting use.

DM

mechanic · « **Reply #17 on:** March 29, 2011, 12:28:02 PM »

After some recent experiences with Briggs that have plastic carbs, I won't have another one. Honda only for me. Yours sounds like it is old enough to have the aluminum carb. and thus is well worth fixin'. I usually do the whole gamut when I fool with a small engine. Spark module, or points, plug, clean the flywheel, clean the carb, replace the fuel lines, etc. Once you break it down you might as well.

Ben

LanceR · « **Reply #18 on:** March 29, 2011, 12:43:42 PM »

All of which reinforces my desire to eventually have all our smaller equipment moved over to diesel or multifuel engines.....

Unfortunately our welder, wheelbarrow air compressor and smaller gen sets are all low hours units so I'll have them for some years yet.

All the bigger stuff and our trucks are diesel of multifuel. The two 6x6 multifuel trucks rarely see pavement so they run on purified waste motor oil. I only put diesel fuel in them when heading out on road trips.

Also worth noting is that ethanol is corrosive to older formulations of gaskets, packings and hoses. It is worth changing your fuel lines, in particular, to ethanol safe line. Older hoses can swell shut from the darn stuff. It really plays hell with our antique engines and tractors.

Lance

scootrd · « **Reply #19 on:** March 29, 2011, 01:25:28 PM »

Quote from: LanceR on March 29, 2011, 12:43:42 PM

Older hoses can swell shut from the darn stuff. It really plays hell with our antique engines and tractors.

Lance

I've had a few hoses become soft, breakdown, collapse and pinch off. Most recently my family's old snowblower, had to make a trip to parents house to replace fuel line last year at start of season. Got a good home cooked meal out of it though

SHOOTALL · « **Reply #20 on:** March 30, 2011, 02:30:51 AM »

Quote from: Drilling Man on March 29, 2011, 12:17:04 PM

From what i keep reading, you have to use the "marine grade" stabil for longer lasting use.

DM

Yep but in some cases its only about 4 mos.

Hooker · « **Reply #21 on:** March 31, 2011, 01:20:33 PM »

When was the last time you ran the valves?

Pat

keith44 · « **Reply #22 on:** April 01, 2011, 06:56:12 AM »

Quote from: Hooker on March 31, 2011, 01:20:33 PM

When was the last time you ran the valves?

If you mean pulled the head, and checked the seat / seal and did the whole carbon cleanup thing on the top end it's been two winters ago, nothing really out of sorts, just pulled it down for a look, re-seated the valves, ran six tanks of fuel through it last year doing some "land scaping" on the new place. Hoping to avoid having to do that NOW

Hooker · « **Reply #23 on:** April 01, 2011, 02:25:20 PM »

If it is an overhead valve engine there is an adjustment.
Some of these type Briggs engines actually will beat the valve seat into the head making the valve lash to tight. That's right I said to tight as the valve seat move up into the head the valve stem also moves closer to the rocker arm. When the engine is cool things are fine but as it warms up the lash gets tighter until you start to lose seat contact and the compression falls off. Lower compression means less vacuum which is what runs the fuel delivery system. I have a riding mower that does this usually it requires that I run the valves twice a season. Takes about 10 minutes.

Pat

keith44 · « **Reply #24 on:** April 02, 2011, 07:01:42 AM »

hmmm, and setting the valve lash on the tight side...hmm

scootrd · « **Reply #25 on:** April 02, 2011, 02:26:46 PM »

did you get a chance today to clean the Carb Bowl?

torpedoman · « **Reply #26 on:** April 02, 2011, 03:45:51 PM »

I never leave any gas in any type of small engine when putting them away for the season i run them dry then try to start then again. works great and is cheaper than stabilt

keith44 · « **Reply #27 on:** April 02, 2011, 05:15:50 PM »

Ok got it sorted out

Pulled the tank, pulled the carb, cleaned the crap out of the carb(nothing visible) put in the rebuild kit, put it all back together...pulled my guts out!! Pulled the float bowl, nothing, dry bowl!! Pulled the needle valve and float back out, no gas coming from the fuel inlet port. So I pulled the gas line off, got a full stream of gas!! Pinched off the gas line got the carb cleaner and filled the barb fitting for the gas line attachment and let it soak. Started getting a few drips out of the needle valve seat hole. Re-assembled carb, again. let the bowl fill up, started tiller, it died after a couple minutes (like before), kept re-starting it each time it ran a little longer. Gave up on using it today and borrowed Dad's. I'd till for a couple minutes, and re-start mine, the third re-start on mine and it ran rough and backfired every third or fourth revolution, then smoothed out, and ran like it's supposed to. Finished the main garden area, and started preparing an area for blueberry bushes with mine!! I guess that tiny little hole that the needle seat has was just too clogged up.

Thanks for all the input guys!!

Quote from: torpedoman on April 02, 2011, 03:45:51 PM

I never leave any gas in any type of small engine when putting them away for the season i run them dry then try to start then again. works great and is cheaper than stabilt

I'll try it your way at the end of this season torpedoman!

Keith

scootrd · « **Reply #28 on:** April 03, 2011, 10:54:59 AM »

Quote from: keith44 on April 02, 2011, 05:15:50 PM

Ok got it sorted out
I guess that tiny little hole that the needle seat has was just too clogged up.

Thanks for all the input guys!!

Glad it worked out for ya. It doesn't take much Just a grain of sand so to speak.