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View Full Version : Briggs compression reading for 3.5hp?


bobcat175
03-02-2007, 02:19 PM
Does anyone know what the expected compression reading should be on a 3.5 Briggs and Stratton? Also what is the service limit reading?

Not sure on the engine type but it's on a Little Wonder edger 6032 that's 5+ years old.

thanks

lucforce
03-02-2007, 06:15 PM
There are no psi limits for this.

The test is LEAKDOWN.

Another test for small engines(not good for little wonder blower) is to spin the flywheel backwards, by hand. The pressure in the cylinder should cause the piston to kickback, and rotate the flywheel in the opposite direction. Better seal= better kickback.

bobcat175
03-02-2007, 08:26 PM
There are no psi limits for this.

The test is LEAKDOWN.

Another test for small engines(not good for little wonder blower) is to spin the flywheel backwards, by hand. The pressure in the cylinder should cause the piston to kickback, and rotate the flywheel in the opposite direction. Better seal= better kickback.

??? I don't understand...of course there are acceptable limits for compression. I was just wondering what is normal for this engine....as well as what B&S considers low to the point that service is needed.
Leakdown is a completely different test, I know that it is a better test but I don't have a leakdown tester....only a compression gauge. The other test you mentioned sounds like a broken finger waiting to happen.

Restrorob
03-02-2007, 09:00 PM
Another test for small engines(not good for little wonder blower) is to spin the flywheel backwards, by hand. The pressure in the cylinder should cause the piston to kickback, and rotate the flywheel in the opposite direction. Better seal= better kickback.

That EXACT ^^^^ procedure is written right in the Briggs service manual....

Let's just say 70 or below is hard to start and below 50 is no start.

bobcat175
03-02-2007, 09:13 PM
That EXACT ^^^^ procedure is written right in the Briggs service manual....

Let's just say 70 or below is hard to start and below 50 is no start.

Thanks - but wouldn't you say that the amount of "kickback" is subject to interpretation. Yes it would tell you that you have compression but it seems that numbers off of a gauge would be a lot better.
So are you saying that B&S does not publish compression #'s?

Restrorob
03-02-2007, 09:25 PM
Straight from the manual; " Briggs & Stratton does not publish any compression pressures, as it is extremely difficult to obtain an accurate reading without special equipment.

It has been determined through testing, a simple and accurate indication of compression can be made as follows"

Then they list the procedure lucforce described.

How many lbs. compression do you have ?

bobcat175
03-02-2007, 09:41 PM
How many lbs. compression do you have ?

Thanks - I'm going to look at a used Little Wonder edger on Sun. The engine is a B&S 3.5hp. I was going to do a compression test as part of my inspection. Anything major that I should look for besides the obvious...not sure what are the common issues. I don't even know what series/type it is...here's a pic...I have higher res ones if you're interested.

dutch1
03-02-2007, 10:06 PM
Briggs doesn't publish compression limits and lucforce is right on with his recommendation. This is the procedure given by Briggs in their repair manual. When I was in a shop envornment, anything under 60 was usually subject to rejection. Customers were advised of low compression units that ran, that they may not run with power under a load and we let them make the call on additional work/engine replacement/new unit. On the high side we considered 90 and above satisfactory. Low compression will tell you that you have some leakby, either worn cylinder/rings, improperly seating valves, loose valve seats or a leaky headgasket. Keep in mind that numbers I gave above are for the single cylinder 3.5-6.5 hp engines.

A leakdown test will tell you where the leak is. If you do much engine work and don't want to spend the money for a commercially made tester, you can put one together with available fittings, guage and hose at much less expense.

We didn't do much leakdown testing. On low compression units our procedure was to pull the head and inspect gasket, head and block for leakby, check valves for proper seating and guide wear, then check for cylinder wear/galling.

Our most common found problem was a low oil condition, leading to overheating which further leads to blown head gaskets, galled cylinder walls, stretched valve stems and loose valve seats. Of course we didn't necessarily find all those conditions at the same time.

Other techs will have additional thoughts. Your mileage will vary.

Dutch

bobcat175
03-02-2007, 11:01 PM
...Customers were advised of low compression units that ran, that they may not run with power under a load...
Dutch

Thanks - Excellent info and all makes sense....

They did say that it ran but when the blade was engaged the engine stopped...this is what sparked my original post...so it is either similar to what I quoted you on or a simple issue with an operator presence control....I wanted to do the compression test to make sure that it wasn't what you said. If the compression is low I will not have the luxury of dismantling their engine (nor would I want to)....and will walk from the sale.

dutch1
03-03-2007, 12:03 AM
Make sure the blade spindle is free and not locking up. Its been a while since I worked on a Little Wonder so I don't recall if the spindle is greasable or not. Spin the blade to check for noisy bearings. If the spindle locks up, this could cause the engine to die, particularly at lower speeds.

Dutch

Restrorob
03-03-2007, 12:17 AM
Below is a possible reason for the engine stalling when put under load (Blade engaged).

bobcat175
03-03-2007, 10:53 AM
Make sure the blade spindle is free and not locking up. Its been a while since I worked on a Little Wonder so I don't recall if the spindle is greasable or not. Spin the blade to check for noisy bearings. If the spindle locks up, this could cause the engine to die, particularly at lower speeds.

Dutch

Thanks - dutch1 and Restrorob...Yes it is greasable. Here is another view.

bobcat175
03-03-2007, 11:50 AM
From looking at the online manual looks like no operator presence controls...so that theory is out.

khouse
03-03-2007, 01:59 PM
It sounds like you have a main jet issue, water in the fuel ='s dirty carb. Or maybe your governor is not working properly. That can make it die when a load is applied. Remove and clean the carb. Drain out all old fuel and add new. If you use the kick back method of checking compression - pull the plug wire for extra safety.

bobcat175
03-03-2007, 02:54 PM
So as long as the compression isn't low....with these other possible issues do you think that $125 is worth it?

dutch1
03-03-2007, 09:40 PM
Personally, for me to put $125 into a 5+ year machine, it would have to be running and I'd also have to see it in use. Incidentally the first two digits of the engine code will tell you the year that the engine was manufactured. If that varies much from the 5+, I'd have reservations.

Dutch

bobcat175
03-04-2007, 12:36 PM
Personally, for me to put $125 into a 5+ year machine, it would have to be running and I'd also have to see it in use. Incidentally the first two digits of the engine code will tell you the year that the engine was manufactured. If that varies much from the 5+, I'd have reservations.

Dutch

I haven't got the engine code....6032 Edgers started in 1990+ so it could be as much as 17 years old...I guess if I have to rebuid the carb or replace the spindle, rods...I could easily be up around the $200 mark.....hmmm now I have doubts.

dutch1
03-04-2007, 01:20 PM
Bobcat,

You most likely find the model,type and code stamped in the blower housing near the spark plug. If not there, it could be on one side of the blower housing. The model number is a 6 digit number, the type is a 4 digit number with a hyphen followed by a letter and 1 or two digits. and the code is an 8 digit number the first two of which give you the year of manufacture.

Dutch

bobcat175
03-04-2007, 04:25 PM
Bobcat,

You most likely find the model,type and code stamped in the blower housing near the spark plug. If not there, it could be on one side of the blower housing. The model number is a 6 digit number, the type is a 4 digit number with a hyphen followed by a letter and 1 or two digits. and the code is an 8 digit number the first two of which give you the year of manufacture.

Dutch

Thanks - I've asked for it but just haven't received it yet....it's for sale and I'm about 1.5 hours away from it.

bobcat175
03-05-2007, 07:09 PM
Thanks - I've asked for it but just haven't received it yet....it's for sale and I'm about 1.5 hours away from it.

990920YB

...it's a 1999. So I guess $125 would be on the high side?