OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs and Stratton 80202 Staring Issues

Hi,
I recently offered to have a go at getting a 1969 Briggs and Stratton powered rotavator to run which a friend had inherited from someone on the allotment.

The engine is a B&S 3.5HP with a air flap governor, manual choke and pulsa-jet carby.

The engine had no oil to start with so added some SAE30. The compression has not been tested with a gauge- it is slightly harder to turn backwards than forwards (it has Easy Pull) so not sure if that is bad. The carby looks as if it has been replaced by someone trying to fix the motor as it looks very clean but had no diaphragm in the pump (which is on the side not the base). I fitted a new diaphragm, checked the jets- which looked v.clean, and fitted a new base gasket between the carb and the tank. I did not get a new gasket between the carb and the head which maybe was a mistake.

Anyway the problem is I can only get it to start by injecting some petrol into the throttle opening. Then it starts immediately and runs okay but a bit smoky. Without doing this injection trick the motor just won't start no matter how many times I pull the cord.

I have checked the spark and looks a bit weak. Setting the armature gap has made no difference to the starting.

I should mention that when I close up the air mixture screw the engine will cut out at about 1turn out position (keeping it at 1.5 t out seems alright).

Any ideas. Possibly poor compression, or leaking carb to head gasket, or points or condenser? Also my petrol mover has a B&S motor and that has a bulb you squeeze to inject a jet of fuel to get it to start. How is it that this sort of carb doesn't have something like this?

Any pointers of what to look at next would be much appreciated.

Thanks
Fossil Light

Being a 69 of unknown condition I would check the valve clearances as they do wear to a point where they partially open even when they are supposedly closed and ACR has a much greater effect on decompression which which can lead to hard starting.

Hi Fossil,

Well it has to be fuel pick up issues as you've mentioned if injecting a bit of fuel manually it runs, there's your process of elimination sorted for you.

Is the spring in behind the diaphragm correctly placed with its protection seat facing towards the rubber, are the pick up tube filters clear etc. ?

Cheers,
BB.

[b][/b]

Hi BB,
All those items you mentioned looked fine when I checked them. I think the carb is virtually new as it is in such good condition. Odd that it was missing the diaphragm though.

Do you know if with a pulsa jet if it normally is supposed to inject a squirt of neat fuel into the throttle during starting to get things going? Don't see the mechanism for doing this.

Do you know what ACR is mentioned in the previous reply?

Thanks for you help
FL

No mechanism other than the choke and the intake vacuum.
Forgive me I forget sometimes that not all are familiar with the ACR term. It is an automatic compression release device. On newer engine is usually a spring loaded swing arm on the camshaft that lowers compression by bumping one of the valves near dead top center (TDC) compression stroke a split second at start up to make starting easier for manual pull and electric starters. On older engines such as your '69 it would be either a ramp or bump ground on the camshaft lobe journal usually for the exhaust valve. Once the engine is up to operating speed these are normally no longer effective.

What I was referring to was that L-heads (side valve) engines tend wear the valve train in such as way that the valve clearance close up making the bump decompression more pronounce. If the valve train has enough wear it can actually have zero clearance. I even seen a few where the exhaust valve clearance was in the negative range. Basically the valve just stays open too long (duration time). Great to make the engine free breathing but terrible for start-up compression because of the ACR.

The solution is a valve job to regain the needed clearances. During the process of the valve job you may find the valve faces need lapping and valve guides need replacing. It may even be worse depending the engine use. You just don't what you find until you actually start the valve job but the first step is to check the valve clearances. These are .005-.007" Intake and .007-.009" Exhaust for the 080000 series. During the valve job I tend to set to the higher clearance to extend the life of the valve job just as I set to the lower clearance on OHV as they wear right the opposite of L-heads.

Boy I getting jet lag here as I am a minus 15 hours from the site time. I going back to saw a few more logs.

Thanks AVB,
To help with the diagnosis of compression loss (valve clearance or otherwise) without having to pull it all apart can I put a compression gauge on the engine and turn it backwards by hand and see what reading I get? Usually you need to crank it for a compression test don't you so you build up a reading in several passes?

Thanks
FL

Yes you can do it backwards but still need to achieve around 250-350 rpms for a valid compression test. Beware that some pull starter are damaged this way depending on the engine's design so you need make your not tightening the pull rope on the reverse method.

Actually compression tests on engines with an ACR is nearly useless though you can get a general idea as most will be around 60-70 psi. Though I have have seen few that would still run around 50psi most won't.

What it takes is a leak down test to determine the engine's condition via non-invasive testing. I don't even use my compression gauge on these 4 cycles anymore other than a go/no go test but I still use it a lot on the 2 cycles.

As for valve clearance you would access the valve area via breather on the side of the engine. Most require the removal of the carburetor and intake manifold to access this breather then it is a simple matter using a feeler gauge with the appropriate valve closed. Now this will not tell if the valves are sealing just the clearance. If the clearance is off then you will need pull the head to make the adjustment.

G'day folks,
Due to the cam design, so as to incorporate ACR as AVB says, compression gauges are of no real diagnostic use on these Briggs engines.

'Easy Spin starting' is old technology now, and Briggs no longer have any detailed docos on their website describing it. You have to go to an older print edition shop manual for that - even the current Briggs CE8069 'Repairman's Handbook' manual omits it.

The excerpt which follows is taken from the 1981 edition of B&S' 'Service And Repair Instructions'.

Briggs have gone away from Easy Spin due to its making hot starts, particularly after the engine has been stalled, more difficult.

Hi,
Thought I would give an update on my issues with this engine, as I got it working last weekend.

-Tested the compression by spinning it backwards with pull starter removed and got it to bounce so compression okay.
-Fitted a new spark plug but that didn't help.
-Checked the spark distance and got an easy spark at 10mm gap so thought ignition must be okay.
-With Bonner Bloke's comments in mind (1st reply) I decided to dismantle the carb again even thought it was in very good condition and all gaskets had been replaced by me. Whilst removing carb I noticed that the small carb-to-head gasket had swung down out of position from the top screw when I had refitted it in March, after putting in the new gaskets. This would have been a massive vacuum leak and prevented the carb drawing up any fuel except once running. This issue had occurred in March before I had inserted the bottom screw and tightened both screws up and I hadn't noticed it then or since. With this rectified the engine started first time on the choke!!! Deep joy.

Problem now is that later in the day, when having another go at starting, the engine stalled with the choke pulled right out and kicked backwards breaking the pull rope. Not sure how common a problem this is but if it happens once I hand it back to my wife's friend she will be stuck. Any comments on how likely this is and what to do to avoid it. The original old rope was a bit on the short side but not sure this would make it more likely to break. Should the rope be strong enough to resist a kickback like this??

Thanks
Fossil Light