OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs 3hp -aligning timing marks

Hi folks!

Wanted to know what will happen with a one tooth (either way) misalignment of the cam gear with the crank gear. Reason being, is that I have a flange mount crank bearing covering the usual timing mark on the gear. The punch mark on the crank counterbalance is between teeth instead of alongside one tooth and I am not sure which tooth it is supposed to be referring to. Pic below, to help identify my issue:

xhall,

The first thing you want to do is remove the bearing and do it properly. Trying to do it the way you have is open for issues.

If you don't line the marks up correctly you will have timing problems and the machine will not run or run badly.

Hi Bruce,

Don't have a proper bearing puller and it is pretty tight.
Should I try to heat the bearing up first and then attempt to move it?
I think I only need to move it about an inch along the PTO to get a good look at the gear, not remove it completely.
But then again, maybe they didn't even mark it....

You need not to remove the bearing but your trying to time on the wrong side. Your current picture is way out of time.

Oh wow, I was way off. Your a lifesaver AVB; saved me a heap of time and trouble!


I assumed that the timing marks had to be aligned in a horizontal plane as per my previous engine. Boy was I wrong (I definitely need to take the time to inspect the parts more closely before taking them apart).

Got the green engine assembled today. Will post a video tomorrow of it working back on the edger. Having fun repairing these old Briggs flathead engines (such a simple design and really easy to work on). Have recently acquired a black one as a freebie, so I have shelved the bonnar frame repair for the moment. I am quite positive I can get this engine to work too.

Timing marks now aligned correctly


Plenty of assembly lube used on internals. Wear gloves, crap sticks to everything.


Even after 30mins, some scoring still remained, luckily it's at the bottom of the stroke and not too deep. Must have accidently chosen a really fine stone.


Cross hatch pattern left in the bore. Not quite 45� but close enough. Drill was rotating at about 80-100rpm and you have to work it hard and quickly (up-and-down) 1/2-1 second per stroke to get a good hatch pattern. New rings were fitted.


New sump gasket, used RTV to seal one side to the block to try and prevent leaks. Unfortunately, on my other recently repaired engine (red), there is leakage (consistently a couple of drops an hour around the bottom of the sump gasket- I think from near the bolt holes). Wish I had used some silicone.


Reused the head gasket, polished, lapped and gapped the valves. Cleaned valve ports and head.


Decided against painting everything, only the cylinder head got primed. Oh, and the 3 longest bolts go around the exhaust port.

Here is a video of me starting the engine this morning. Does anyone know how to embed the video into the post?

It is hunting slightly when above idle speed, which indicates the mixture is a bit lean. Also, Briggs disapproves of allowing the engine to idle slower than 1,750 rpm, because the fan becomes largely ineffective at lower speeds, and heat soak-back after running under load, can then result in thermal damage. Other than those small points though, it looks and sounds like a successful rejuvenation job.

Thanks Grumpy!

Re: idling - The idle screw is close to bottoming out as the spring is pretty much crushed. But there is about half a turn left. For a cast iron bore isn't the idle rpm is supposed to be 1200rpm. Anyway I don't own a tachometer.

Re: hunting - the carb was given a good clean. The fuel pickup screen was cleaned with a brush, ports were cleaned with carb cleaner and compressed air. I installed a new fuel tank gasket, flange gasket and diaphragm. There is a lot of vibration and maybe this is causing the linkages to jostle a bit affecting the idle. However, the hunting is almost neglible once warm. Are there any other adjustments that can be made to richen the mixture?

I suggest you post the Model, Type and Code for the engine, so we can access the Operator's Manual. At the moment I'm unclear on why you haven't mentioned the mixture screw. Also, IIRC, the idle speed is only different for the very old all-cast-iron engines, not for the I/C versions of the aluminium engines (I/C versions have a cast iron cylinder liner and a two stage air cleaner on what is otherwise a standard light duty aluminium engine).

That is this one.


Idle mixture screw is 1.5 turns out from seated.

You probably already know that engine was made on 15 February, 1984, which means it has Magnetron electronic ignition. Here is the Illustrated Parts List:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6mmyAVJ1DajI.pdf

Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/lrwBF-wU7eL7hAxB91ObQ.pdf

The engine has a horizontal crankshaft and is designed to be flange-mounted.

If you look at Page 7 of the Operator's Manual, in the left column at the top of the page, you'll see the instructions for adjusting the mixture - it is a main jet adjustment, not an idle adjustment. I'd guess you will need to adjust the mixture screw about an eighth of a turn anticlockwise, but you'll soon find out when you follow the procedure in the manual. It also tells you to set the idle speed for 1,750 rpm. Be sure the engine is warmed up for at least 5 minutes, and the choke is pushed all the way in, before you make either adjustment. It is usually convenient to use a simple tachometer with a sensing wire which wraps around the spark plug lead, similar to this one:
http://www.ebay.com.au/itm/Engine-D...DefaultDomain_15&hash=item5d51922c4e

However you'll find there are some hundreds of suppliers of this or similar instruments on ebay.

Thanks for that info Grumpy. I will try adjusting the mixture screw to see if there is any improvement. The idle rpm will have to wait until I purchase a tachometer. Is there a tachometer you have personally purchased that you would recommend, besides the one you have posted in the link?

Apart from the one I posted (and remember there are about 50 different vendors selling the same item) I've only used a stroboscope on mower engines. The stroboscope is not convenient unless the engine has a visible flywheel, and even then is not as easy to use, mainly with regard to safety, and reliable accuracy.

If you are looking at tachometers similar to the one I posted, please remember two points. First, there are several vendors selling a variant on that design which simply has a slot in the back which the pickup wire is run through, rather than it being hard-wired to the tacho module. They are a couple of dollars cheaper. I haven't used one of those so I can't give an opinion on how well they work. The second point is that old versions of the one shown in the link I provided, like mine, have the battery embedded in the module's potting mix so it can't be replaced. At least some new versions of that tacho now have replaceable battery. I think that would be a positive feature if you use the tachometer a lot.

Well, I have been messing around with the mixture screw and that has only managed to make things worse. It is running very rough now at full throttle. Maybe I should use some RTV silicone around the manifold and tank gaskets - rule out any air leaks. The air vane mechanical governer and loose linkages are rubbish IMHO. Do you think the cold weather has any effect?

BTW, I have gone ahead and purchased the digital tachometer from the link you posted, should be here sometime soon.

What is condition of the fuel tank? Here I have had problems with these carburetors when the tanks are rusty or had old fuel left in them causing the fuel pickup screens to clog during carburetor rebuilds. Sometimes the only solution is a new tank and re-cleaning the carburetor assembly.

The fuel gasket on this setup is there to prevent fuel leaks primarily using sealant is not necessary unless the gasket is damage but that can problems in itself.

The tank is in pretty good shape. There is only some minor rust on the bottom of the tank as you look straight down the filler neck. I have fuel leaking from around the fuel filler neck/cap. This happens when you tilt the machine back, so you can push it around without the blades scraping or hitting the ground when in operation. I got nothing to lose , so I might try giving the carb another clean and double check the fuel pickup screens. Are there any other parts of the carb (besides the diaphragm) that could need replacing?