Detailed Rebuild How-to: Briggs 3hp Cousins

[Dr. Shop Teacher]

Replacing Starter Rope

The second most frustrating thing about recoil starters is replacing the rope. The spring is the worst.

The most important thing to do is get the right diameter starter cord. The Briggs L-head manual posted as a sticky gives the diameters/lengths for engines 9000 series and up. It doesn't have the 8000 series or the 6000 series, so you need to take a piece of the original cord with you when you go to the hardware store or small engine shop. Trying to stuff in the wrong size cord is a nightmare.

Extend the starter cord fully out and use a small clamp to secure the recoil in place. Remove the knot and save the rope, you'll need it to get the right length.

Of critical importance is alignment of the knot hole to the handle hole. I used a piece of wire to get it lined up correctly. <<The rope does not simply wind around the spool>> rather it passes through a small tube and then to the knot hole and is shown by the yellow line below.

Cut the rope about 2" longer than needed and use a lighter to slightly burn the end so that it's a little "glob" on one end.If you're really lucky, you can slide the rope right in and pull the end out with needle nose pliers. Otherwise, grab a small, solid diameter wire (18g or smaller) or your spouse's needle point hook and push the rope through.

Then, loosely make a knot on the other end as shown below (be sure to put the pull handle on first) and release the clamp to allow the cord to recoil into the starter.

Adjust the length as needed and tie the knot as shown above after burning the end. And, you're done.

BTW, I used Rustoleum to break down the rust on the shroud and I need to re-sand to get the flash rust off.

 

[Dr. Shop Teacher]

Do you really...want to keep and install points???

Just for fun, I decided to keep the 72 engine with a points ignition. If the engine is a "modern" L-head, you can convert it to a Magnetron (solid-state) ignition simply by swapping out coils, which I'll do if this engine has a weak spark. The old Briggs engines require the magnets on the flywheel to have their polarity changed. The 64 engine is going Magnetron because the new crankshaft does not have a lobe for the points plunger. Points/condenser kits are getting expensive and a 3rd party solid state coil can be had for about $15.

I'm reusing the points/condenser that was on the engine (they were pretty clean with little pitting). First up is connecting the coil wire and ground wire to the condenser. I used my spring compressor to compress the tiny spring on the condenser. I didn't have the tool or a thumb plunger for the spring.

Mount the coil on the block to get it out of the way. Insert the plunger in the proper hole on the crank bushing (there is a reject size found in the 1975 Service Manual).

Install the condenser and loosely tighten into place. Then install the points and secure in place. Make sure you have the spring mounted correctly so it doesn't bind.

This diagram shows how to set the points and is better than my photo. You'll need a feeler gauge set to 0.020".

Make sure you rotate the engine so the points have the largest gap between it and the condenser. Adjust the condenser to set the gap. Tighten firmly in place.

Check the point gap again after tightening! It's nearly guaranteed to move. Briggs engines are sometimes forgiving with point gaps but not as a rule.

Install the dust cap and you're done. A dab of silicone sealant where the wires exit is a very good idea.

 

[neo71665]

If you have any cord left in the recoil I find tying dental floss to it before you pull it out so you can tie it on the new cord to guide it in easier. Everything and the stars still have to be aligned to get it in.

 

[Dr. Shop Teacher]

If you have any cord left in the recoil I find tying dental floss to it before you pull it out so you can tie it on the new cord to guide it in easier. Everything and the stars still have to be aligned to get it in.

Great suggestion...I got really lucky and the stars aligned!

 

[Dr. Shop Teacher]

Here's an example of how not to knot the recoil rope

This is the 74 shroud/recoil. See how small the knot is and, thus, would eventually come out.

 

[Dr. Shop Teacher]

Taping the 74 up for paint

Haven't decided what color to use on this engine. I spray my engines in pieces to get even coverage especially with the tank. I covered the mating surface for the intake manifold to assure a nice seal. I also tape up the crank seals.

 

[Dr. Shop Teacher]

'74 in paint

Got lucky today and could get outside to get some color on the '74. Trying to stage parts to get them in urethane. Both Briggs and an H35 are ready for some Eastwood 2k. One good weather day coming this week, so I hope to be able to spray and cure under heat lamps.
.

 

[John S]

The paint looks nice! Are you using rattle can?

 

[Biffmini]

:thumbsup:Great job on engines & thread

 

[Dr. Shop Teacher]

The paint looks nice! Are you using rattle can?

Yes, this was Rustoleum Gloss White. I wasn't too worried about matching to original Briggs white.

:thumbsup:Great job on engines & thread

Thank you sir, tomorrow is the day for urethane.

 

[Dr. Shop Teacher]

Reassembling the 74

The urethane cured pretty quickly, so time to put this one back together. I used button head hex screws to put the carb/tank back on the engine. The old screws were pretty much shot and these seemed to do the job with a hex wrench. Next up was the breather tube (new), grommets, and air filter gasket.

You know you have an old engine when the air filter screw has cross hatched knurling and the slot is curved to accommodate a coin. Look close...

 

[jackeo21]

Looking really sharp Doc, awesome work :thumbsup:

And I had no idea about the air filter screw being designed to accommodate a coin! Would never have thought about that.

This is such an informative and helpful thread for anyone interested in learning about or rebuilding the 2HP and 3HP Briggs engines.

-Jack

 

[maknwar]

I wish I wish I would have seen this before I started my restoration. Your Briggs are in the same shape mine is in.

I didn't notice if you kept the governor? Can you show the throttle hookup because all my throttle linkage is so bad that I need to make or buy new.

 

[Dr. Shop Teacher]

Looking really sharp Doc, awesome work :thumbsup:

And I had no idea about the air filter screw being designed to accommodate a coin! Would never have thought about that.

This is such an informative and helpful thread for anyone interested in learning about or rebuilding the 2HP and 3HP Briggs engines.

-Jack

Jack, you got me hooked on these beauties! This has been fun to do and document. Allows me to tinker for a bit on days my back says, "not today." Today was certainly one of them!:doah::laugh::surrender:

I wish I wish I would have seen this before I started my restoration. Your Briggs are in the same shape mine is in.

I didn't notice if you kept the governor? Can you show the throttle hookup because all my throttle linkage is so bad that I need to make or buy new.

Yup, I'll be doing the linkage next. Needs to be cleaned up a bit and I'll need to disassemble another (similar) linkage to direct my progress. I'm undecided about reusing the governor, but I have all the parts for it. Maybe tomorrow or the next day before I do them, but it'll be all documented.

 

[Dr. Shop Teacher]

Throttle Linkage and Governor (74 engine)

I was asked if I was going to run a governor or not. I did some research on this engine's governed maximum speed and it ranges from 4000 to 4600 depending on intended use (from the 75 manual). I also did a search within OldMiniBikes for commentary about running a 3 hp ungoverned. One of the more respected builders advised against it. So, 43 yr old motor with original internals and cast flywheel, maximum governed speed of 4000. So what is this engine is intended for?...a small bike. Governed it is.

There are about 15 different combinations of throttle/governor controls, so what you see may not be what you have. First up, clean all the little parts...you want them to move freely.

This carb has a choke-a-matic. If you have a side choke carb, you may or may not have this linkage. It's actually good to have, as I've had carbs without it and the choke moves around a lot. Below is the rod installed. Note the spring location. A throttle cable retainer is also installed. You also see the speed control lever (on the right)--it has a stepped washer that must be installed to allow it to move freely.

The purpose of the governor is to limit maximum engine speed and maintain idle rpm when not under load. The throttle control and the governor are in competition: one wants the engine to accelerate and the latter wants to bring the engine back to idle.This particular governor is a pneumatic-type. Larger Briggs engines and Tecumseh engines use an internal governor weighted spool. Make sure the air vane governor is clean and moves freely. Newer versions are plastic and metal.

The governor rod attaches to the throttle plate and to the governor (in the top hole). A throttle spring is connected to the loop in the governor rod and connects to the speed control. Be sure you have the right spring for your application. A hardware store spring is not acceptable.

This is how it looks assembled. The governor is adjusted by bending the rod. I have it fairly straight currently. Note also the choke-a-matic rod. This needs to be adjusted so it does not prohibit free movement of the throttle lever. The spring is connected in the second hole down.

 

[Dr. Shop Teacher]

Flywheel and Starter Clutch Install

One of the critical elements is the proper attachment of the flywheel to the crankshaft. Some folks believe the flywheel key keeps the crankshaft in place; in reality, it's purpose is to keep the engine in time. So, the flywheel needs to be tightened securely (in this case to 55 ft-lbs). First things first, though.

The flywheel has a taper which corresponds to a taper on the crankshaft. Havasu Dave recommends lapping the flywheel to the crankshaft. This ensures both tapers fit snugly--a tension fit. Use fine lapping compound, slide the flywheel on and spin it for a bit. Be sure to clean both surfaces, when done.

Next up, the crankshaft extension (before the threads). This slides into the starter clutch...the fit is pretty tight, so you want to be sure the starter clutch slides on with little resistance. 220 sandpaper does a nice job cleaning up any burrs.The flywheel is then installed with the appropriate key--soft metal--and a Briggs specific key. Don't use a steel key....ever. Say the the drive wheel on your bike suddenly locked up...if you're lucky, you throw a chain...if not, you might bind up the engine and the rotational force of the flywheel wants the engine to keep going. A soft key shears and saves the engine internals.

The washer shown below is a Belleville washer. It is cupped like a dinner plate. In conjunction with the starter clutch, the washer locks the flywheel to the crankshaft. Unlike a dinner plate, the washer is placed upside down on the crankshaft, and then the starter clutch is installed. As the clutch is tightened, the washer evenly spreads the threaded torque as the clutch is tightened.

KMC3420 sent me a really cool little tool to lock the crankshaft in place in order to torque the starter clutch.

This tool is designed to fit the starter clutch ears and should be used to install and remove clutches. It's the only way to properly torque the flywheel on an old style Briggs engine. It's about 12 bucks online, and worth every penny.

Use the tool and a torque wrench to torque the flywheel to 55 ft-lbs.

 

[KMC3420]

What an awesome informative thread, looks as good as new. Keep up the pictures please, I know myself included will reference this thread when the time comes. :thumbsup:

 

[Dr. Shop Teacher]

What an awesome informative thread, looks as good as new. Keep up the pictures please, I know myself included will reference this thread when the time comes. :thumbsup:

Your "crank lock" worked like a champ and made torquing the flywheel a piece of cake!:thumbsup:

 

[KMC3420]

Your "crank lock" worked like a champ and made torquing the flywheel a piece of cake!:thumbsup:

:thumbsup: glad to hear that. Looks like you always have a good plan no matter if you have a tool or not. I am going to get a dial indicator like you did on your other thread and make a fixture for it. You have plenty of good ideas tool wise.

 

[Dr. Shop Teacher]

Anatomy of a Starter Pawl

If you've ever wondered where that shriek comes from when you're revving your older Briggs flathead, this post is for you. Briggs went to a "modern system" some years ago using a ratchet type starter. The starter pawl used on old-style Briggs engines is actually fairly complicated and uses ball bearings as an "on-off" mechanism to rotate the crankshaft to start the engine. Once running the ball bearings release.

The images below show how the pawl is assembled. There are six ball bearings inside the pawl. If the pawl is disassembled for inspection, simply clean up the balls but do not oil. The cover needs to be securely reinstalled, or at speed, it will come off.

There is an oiler hole located at the top of the pawl, as shown below. The manual says to lubricate with one (1) drop of synthetic oil. I'm not too sure why it has to be synthetic, maybe for longer life? Who knows....

Looking from the base up, the inside of the pawl is machined to fit around the crankshaft extension. If you have a crankshaft that DOES NOT have the roughly 2" long extension, you CANNOT use this style starter. A couple of pulls and the pawl will be in pieces without the support crank extension.

This image tries to show the inside of the shaft and the threads. Threads, of course, need to be clean. It is not unusual for the starter pawl threads to pick up some corrosion, dust and dirt, making it more difficult to remove the starter.

So where does the shriek come from? Like everything Briggs does, parts are designed to perform within certain design parameters to make the products they produce cost effective. The starter pawl is NOT designed to handle extended run periods without lubrication and, more importantly, it's not designed for extended periods of revs in excess of 4500 rpm.

Eventually, heat and friction cause the pawl to lock up against the crank extension sounding first as a shriek. It's safeguard is to blow apart sending the ball bearings everywhere.