leaf blower blues (Briggs 8HP I/C)

[hazmat]

Since it seams customary to post small engine repair questions here, I've got one to add.

I've got a hand me down Little wonder walk behind leaf blower. It has an 8HP briggs Industial/commercial horizontal shaft engine. I estimate the unit is between 10 & 20 years old.

I couldn't find a serial number on the engine. Of course I was trying to find it quickly this morning while trying to get to work on time. Where should I look? I want to buy a service manual to walk me thru troubleshooting & repair.

Sometimes it is hard to start. Once it gets warmed up, the engine frequently loses power. The choke needs to be set about halfway on (in line with air intake tube vs 45 degree up for "ON" or 45 deg down for "OFF") for it to run correctly.

So far I've changed the oil, sparkplug, fuel filter & air filter (all the basics). I've also tried playing around with the carb adjustment screws, but I don't really know what I am doing & it didn't seem to make much of a difference. Any tips while I try to track down serial number & manual?

I suspect a blown head gasket as I think I saw some blow out as I was trying to start it. Plus it is really loud even with a new muffler. I don't have a compression tester. Is it a worthwhile investment? Or should I just pop the head off & inspect the gasket?

hmm, maybe this is a blessing in disquise, If the motor self destructs, I just might have to convert the blower to a three point hitch version for the tractor. Probably cost more than replacing the motor/w3tcompact/icons/frown.gif

 

[heehaw]

my guess would be fuel problems, maybe trash in the carb bowl and/or tank. good luck
heehaw

 

[kubmech]

It's a leaf blower, so it does alot of sitting around not running. The fuel in the carb gets old and allows varnish deposits to build up and gum up the needles and seats and orifices in the carb. Sometimes you can get away with removing the adjustment needles and the float bowl and spraying 2+2 carb clean (with the little red hose attached) through all the orifices and clean out the bowl and this will get you going again. When re-installing the needles, gently (with your fingers) screw them in till they bottom out. Then back them off about one and a half turns. This should be pretty close to get it running. Then run at full throttle, adjust the needle that goes into the bottom of the carb till it runs smooth. Then at idle adjust the other needle till that smoothes out. That should get you pretty close. The model/serial number should be located on the engine shroud, it's stamped in. Unless you have a newer engine then there will be an id plate/sticker. Another problem you will see with equipment that sits around alot is "critters" love to build homes in the cooling fins under the shroud which will cause the engine to overheat and blow the head gasket. Both of these likely problems are very common. The manual you want is part#270962 if you have the good old fashion L head engine.

 

[hazmat]

Thanks guys, I looked again tonight. Armed with the knowledge that the ser. number was on the shroud. wouldn't you know, right there on top staring me in the face. Amazing how much more open my eyes are at 10pm vs. 6am!

For those interested
Model 195432 type 0297-01 code 84011710 per the briggs and stratton web page That dates it as a 1984 model.

I'll order up a manual & get myself a compression tester to check the gasket. I'll Also try some carb cleaner on it & pop the shroud to check for critter damage. Might not have a chance to spend too much time on it before turkey day.

 

[hazmat]

Well, ordered the manual & while I was at it got the gasket set for $13 and the carb rebuild for $17. all from jacks small engines. Figured that the kits were cheap insurance: I'll be up and running & the leaves removed before old man winter settles in.

I'm going to pick up the compression tester & carb cleaner tonight & open the old girl up.

 

[justractors]

Most, but not all, small engines have a compression release system of one type or another that make them easier to start.
Your engine does have the compression release built into the camshaft. Point is that the engines will not show the proper compression reading with the compression gauge unless you can spin it fast enough to override the compression realease feature. Best way to check the rings and valves on your engine would be by performing a leakdown test which any good small engine repair shop should be able to for a small charge.

Just my humble but well thought out opinion.
Bill

 

[hazmat]

<font color=blue>Your engine does have the compression release built into the camshaft. Point is that the engines will not show the proper compression reading with the compression gauge unless you can spin it fast enough to override the compression realease feature. </font color=blue>

Hmmm,

I got 80 psi for a reading. What is the compression ratio for the briggs? If it's 7:1 I should have read 90psi, if its 6&change:1 I'd get the 80.

Edit here:
Should mention that this test was on a cold engine contrary to the compression tester's instructions.

 

[kubmech]

Hazmat, Bill is correct. They do have a compression release. However, when I first started out, I didn't know about the leak down/differential pressure tester (not even sure if they had them) and I use to use a good old fashion compression gauge. On most of the small engines I tested, I found that an engine with an electric starter was in pretty good shape if I got 90 psi. If it was a pull start, I would be satisfied with 80 psi. After checking compression on light aircraft with a leak down tester for a few years I was pretty happy to see that Briggs came out with one and immediately purchased it. Granted, it is a better test. But the compression gauge will still tell you what's going on if you have used one for any length of time on small engines. At 80 psi (never saw a little wonder blower with electric start, besides the "2" at the end of your model# indicates a pull start if I remember correctly) I would venture to say that the cyl. piston, rings and valves are in pretty good shape. Just keep in mind that this is not "the most effective test" for a leaking head gasket due to the fact that cyl. pressure under running conditions will be much higher. You said you ordered a gasket kit and that you were going to pull the shroud. It only makes sense to pop the head off at this point to have a look at the gasket and clean the carbon out of the combustion chamber. It's good PM to clean out the carbon anyway. As an added bonus it gives you a great excuse to buy (or use if you already have one) a torque wrench./w3tcompact/icons/wink.gif

 

[hazmat]

<font color=blue>As an added bonus it gives you a great excuse to buy (or use if you already have one) a torque wrench. </font color=blue>

Already got 4 of those. From screwdriver size all the way up to 1/2". I have been looking for an excuse to upgrade the 3/8 & 1/2" ones. They are the "old school" beam type. Kind of inconvenient to use if you're in a position where you can't see the gauge. Also the ratchet comes in handy. But the price was right & I can recalibrate them myself.

 

[hazmat]

Well after a little mix up (they shipped me the wrong order) I got the manual & parts yesterday. Just in time for 6" of snow!.

Pulled the shroud off, only found 2 leaves, so the fins weren't clogged up. Pulled the head off. Gasket looks OK. LOTs of carbon on the head & piston. What's the best way to clean it? Wire brush? Solvent?

Took apart the carburater. It doesn't look gummed up, but does have a slight tint to it. Since I've got it apart I will soak it in carb cleaner. Only ran into one snag. The "Inlet seat" is pressed in, the replacement that came with the kit is a threaded one. Should I worry about it?

If the ground stays covered in white stuff, I've got 5 months to figure this out.....

 

[Molerj]

You can clean the head & top of the piston with a wire brush on a drill or angle grinder.
As for the "inlet seat", are you talking about the float bowl needle valve seat? They
should be the same. You can't replace a pressed in seat with a threaded seat (i'm sure
you know that).

 

[hazmat]

<font color=blue>As for the "inlet seat", are you talking about the float bowl needle valve seat? They
should be the same. You can't replace a pressed in seat with a threaded seat (i'm sure
you know that). </font color=blue>

I think so. Item 11 in the attached pic, but it actually looks different, see next post

Edit Here:

What I meant by "should I worry about it" was, should I get the correct one IE the press it seat & replace it, or is cleaning the seat & replacing the inlet needle good enough?

 

[hazmat]

In the previous pic, the seat is horizontal. The seat is actually vertical (horizontal in the attached pic, but the carb has been rotated relative to the previous post) Clear as mud eh?

 

[Molerj]

Well, that does look a bit confusing. If the needle valve didn't leak thru before, I wouldn't
worry about changing the seat. I haven't had to change many seats, if I did, it was
because it came with the kit.

 

[kubmech]

Hazmat, I'm just a little confused. Item 11 in the first view looks like the fitting that the fuel hose clamps on. Item 10 would be the float needle seat. The second picture gives you a technique for removing the float needle seat (the press in type). Both types of seats were used and I would think that if you have the proper carb kit you should have the proper seat or both seats, some carb kits cover several different model carbs. You may want to compare the other parts in the kit to what you have. As far as cleanig the carbon, I like to use one of those flimsy little "giveaway" pocket rulers. You can use the round end and the flat end as a scraper to get the heavy stuff off. Then I use a wire brush and carb clean to clean it up nice. Just remember you are working with aluminum and it gouges easy. Nothing wrong with using a "motorized" wire brush either as long as your careful not to remove too much aluminum in the process, you just have to be gentle. Don't clean the gasket surface like this, the best way to do that is scrape off any heavy stuff. Then if you have an old peice of glass laying around or a flat machined surface you can clean it up by rubbing on a piece of 400 grit wet and dry paper keep it wet and clean with carb clean. Just lay the paper on your flat surface and "sand" the head in a circular motion. And like Ron just said, if the seat was'nt leaking you can blow off that step. Just shoot some carb clean through the old one and use the new needle valve. By the way item 9 is the needle valve.

 

[hazmat]

Kub & ron,

Hmm maybe the item number (11 vs 10) was a typo in the manual, don't have it in front of me now to check.

How do I know if the seat was leaking?

The other parts in the kit appear to match the existing parts.

Thanks for your help guys!

 

[kubmech]

Fuel enters at item 11 flows through item 10 past item 9 and fills the float bowl. Item 9 is attached to the float (item 4). With no fuel in the bowl the float drops to the bottom (it's on a "hinge pin"). As the float, "floats" up, item 9 seals off item 10 and stops the flow of fuel to the bowl. This is what maintains the proper fuel level in the float bowl. If item 9 and 10 were leaking you would notice a constant fuel leak from the carberator especially when the engine is shutdown. Depending on the severity of the leak you may not have a problem while the engine is running but this condition could cause overfueling.
Some people just turn off the fuel when the engine is not running when they have a leak in this location rather than repair it and never have a problem. Depending on the mounting and model of the carb and it's location to the valves. The fuel could seep into the valvetrain and combustion section of the engine, causing the fuel to fill the crankcase of the engine. You would not experience this condition on your engine due to the design and location of your carb. You would just have a constant leak from the carb.

 

[hazmat]

Ut Oh, Sounds like I might have a leak there, as the leaf blower smells of gasoline when it has been sitting.

Maybe It's time to call Jacks back & get the right seat since I've got everything apart & I don't know if it's the needle or the seat that is causing the leak.

 

[hazmat]

Well I cleaned the carb & reassembled using the new parts that came in the kit. Cleaned the carbon off the head & cylinder top. Replaced the head gasket for good luck.

Brought it outside. Started on the first pull! After playing with the high speed needle, it runs like a champ!

Thanks to everybody for their help!!!/w3tcompact/icons/smile.gif

Now. any suggestions how to blow leaves that are under 2" of snow? Come spring, I'll be ready!/w3tcompact/icons/tongue.gif

 

[DocHeb]

Yeah, our snow came early and hasn't melted yet - this is the longest December cold spell I can remember.

Leaves under snow are hard to blow - but wet, matted leaves in spring are even harder!