Briggs rebuild?

[mclothier3]

I have an old 4hp Briggs I pirated off of a $20 garage sale Monkey Wards Tiller, I attempted to get it to run before I pulled it, but no luck. It seems low on compression, and weak to no spark.

it appears to be a #100202 built in 1965

I havent torn it completly down yet, but I did pull the head and found that the cylinder looks ok, with just a slight ring ridge, besides some carbon build up it really dont look that bad.

In the process of checking it out I found that the flywheel is rubbing on the coil, it appears that the crank bearings/bushings? are sloppy causing too much slop.

Questions I have...
Is it worth saving? Cylinder would be no big deal, but the crank slop has me worried.

Good online place for parts? I tried local, but it seems like all the mower shops either want to sell me a new engine at $270 or a "rebuild kit" for $240

I would also like to replace the carb with a mikuni or other type that is more like a motorcycle so I can run a separate gas tank (gravity feed) Any suggestions on what would work ? I will probably be fabbing my own intake manifold so Im open to anything.

Any performance improvements? anybody have any basic performance mods to share? I plan on at least doing at least a slight port job, maybe bumping up the compression a bit.

Its been many years since Ive rebuilt one of these, but I dont remember it being too hard.

thanks for the help!

 

[Rhovis]

you need to pull the crank out to the block and inspect both the journal in the block and on the crank. I would guess one or both is beat resulting in a junk motor. If the journals look good, proceed with the rebuild

 

[Barticusmax]

You could also sleeve the case if the crank is ok, they used to call them "Speedy-sleeves".
Also, I can't tell you how many dozens of coils I have replaced because they were too close or rubbing, and that seems to kill them, not sure why.
I have milled up to .020 off the head for improved compression, check the valve guides too since it might be a "High Miler" and reseat them with some valve compound, you will be surprised how much that helps.

 

[mclothier3]

Hmmm, well it sounds like its not gonna be a cheap build. I can handle most everything except installing valve guides, and sleeving the case since I probably dont have the tools for it. What would a shop charge to do those?

As far as parts, it looks like Ill need a set of rings, possibly both valves and new guides, new coil, points and stuff, gaskets, new carb, etc.

Weighing my options at this point, the more I look at those engines from Northern tool and Harbor freight the better they are looking, especially since I didnt want to spend a whole bunch, trying to keep the cost down.

thanks for the help.

 

[mclothier3]

Oh, forgot to ask...

Im pretty sure the drive side has a regular bearing, does the flywheel side have a bushing? and can I just replace it if the crank journal is ok? or does it require a special tool or something?

 

[Nitrohorse]

To be honest, the amount of money you will get into the engine isn't worth it.
Unless the engine hold sentimental value (on a mini bike that you had as a kid, grandfather willed it to you, etc.), I would just move onto a new engine. I have rebuilt many old engines, but there's a point where you decide if it's worth it or not.
The point to remember is that everything in the engine is worn. To do it right, almost every component should be replaced, milled, or repaired.

 

[mclothier3]

Well after tearing it down all the way...I agree!

The crank dont look like it can be saved, its got some pretty deep grooves, especially on the rod journal, plus the engine has no bearings, its sleeved on both sides of the crank.

I really dont have any reason to save it, I just thought it would be cool to keep it old school briggs.

Oh well, looks like I got a $20 paperweight :doah:

 

[Nitrohorse]

I can sympathize with you. I bought a Kohler 16hp cast iron engine that I was told was never bored. Shame on me for not verifying that, but the engine was already bored .030 over and was useless to me unless I had it sleeved or I had a custom piston made. I inquired about the piston and was told that the minimum I would have to order was 4...x 140.00 each. I eventually had it sleeved for $135.00.
I guess we all get "bit" one time or another.
My suggestion would be to hunt for a 5hp flathead. There's thousands of them out there...

 

[mclothier3]

Oh I dont think I got bit, I bought the tiller for only $20 and ended up selling the remains for $10, and I might be able to get a few bucks for the shroud and maybe the flywheel, gas tank with carb etc.

And yeah Im on the lookout for a decent flathead, even thought the clone engines look like a good deal, I really wanna stay with the flathead look.

I did find a huge Briggs Vanguard 22hp up for auction... Briggs v-twin but It probably wouldnt fit, plus not sure if the can be run horizontal.... definetly cool though!

 

[Nitrohorse]

Oh I dont think I got bit, I bought the tiller for only $20 and ended up selling the remains for $10, and I might be able to get a few bucks for the shroud and maybe the flywheel, gas tank with carb etc.

And yeah Im on the lookout for a decent flathead, even thought the clone engines look like a good deal, I really wanna stay with the flathead look.

I did find a huge Briggs Vanguard 22hp up for auction... Briggs v-twin but It probably wouldnt fit, plus not sure if the can be run horizontal.... definetly cool though!

Ok, you didn't get bit "this time"..ha..ha. We all do though at one time or another.
The vertical shaft engines can be used, but they have to remain in the vertical configuration. Surplussupply.com offers 90 degree gear boxes to use them, but you're getting into issues with space limits on a mini.
I like the sound of a horizontal Briggs Vanguard (Harley-Davidson), but they're too expensive on the secondary market. I guess time will change that eventually.

 

[mclothier3]

Well I found a used 5hp Briggs I am going to look at tomorrow, $75 obo the guy says it runs excellent with low hours and came off a walk behind blower. Ill check the year code when I see it, and Ill definetly check the crank slop. think it worth it?

 

[drheilman]

Well after tearing it down all the way...I agree!

Oh well, looks like I got a $20 paperweight :doah:

Not exactly. You were just buying "high performance parts" for a engine You didn't own yet. Buy the 5 horse, then take the head off the 4 horse (marked by the #10 in-between the fins ) add bolt it on the 5 horse. The 4 horse head is higher in compression than the 5 horse. You may have spent more than $20 to get the 5 horse head milled down. Anyways, Your better off with a old flathead Briggs than some disposable clone motor..:thumbsup:

 

[mclothier3]

Well I picked it up for $60, the guy was right... it runs excellent. Its on a MTD yard blower. Numbers off the engine are...
model 135212
type 1313 E1
code 970925YB

Ill get some pics later, the only thing that has me worried is that it does have a 3/4" shaft but its like the crank comes out of the side cover at 1" then necks down to 3/4" which means Ill have to set the centrifugal clutch a little farther outboard than I was wanting. Or maybe a crank mod to turn it down to 3/4" the whole length.

 

[mclothier3]

Ok well I screwed up...again :censure:
The crank is actually 1" then it necks down to .875" and the keyway is really short like only on the last inch of the shaft. Since I ordered the 2 speed jackshaft it definetly needs a 3/4" shaft so Im hosed :hammer:

Anybody ever had a similar problem? and how did you fix it? :grind:

I had a thought... I could start the engine and use a grinder to take it down, I know it sounds like a hillbilly fix (and it is) but I know I could make it work, it just wont be pretty.

Only other option would be to take the thing apart, and turn the crank on a lathe, I might have access to a lathe so this sounds like a better way to do it.

But either method I use... I dont know what to do about the keyway. Does anybody know if those clutches come with a set screw arrangement to lock it in place? if so I could just dimple the crank using a drill.

 

[mclothier3]

Here are some pics of what Im up against...

And here is a shot of the 4hp head, even though a couple fins are broke around the plug area, would you use it?

 

[Nitrohorse]

Ok well I screwed up...again :censure:
The crank is actually 1" then it necks down to .875" and the keyway is really short like only on the last inch of the shaft. Since I ordered the 2 speed jackshaft it definetly needs a 3/4" shaft so Im hosed :hammer:

Anybody ever had a similar problem? and how did you fix it? :grind:

I had a thought... I could start the engine and use a grinder to take it down, I know it sounds like a hillbilly fix (and it is) but I know I could make it work, it just wont be pretty.

Only other option would be to take the thing apart, and turn the crank on a lathe, I might have access to a lathe so this sounds like a better way to do it.

But either method I use... I dont know what to do about the keyway. Does anybody know if those clutches come with a set screw arrangement to lock it in place? if so I could just dimple the crank using a drill.

I would either pull the crank and turn it down to 3/4" and broach a keyway in it or hunt for a 3/4" crank. The older Briggs (1940's-1950's) used a dimple on the crank to nest the set screw, but they were only churning out all of 1.5 hp on a good day. I'm not sure I'd trust a dimpled set screw on a mini bike application.

I would use the 4 hp head as long as it's not cracked. The missing fins by them self won't cause any problems.

Now I think I can say you were "bit."
It happens to all of us sooner or later.

 

[mclothier3]

=
Now I think I can say you were "bit."
It happens to all of us sooner or later.

LOL, well thats what I get when I dont look it over like I should, I jumped in and bought it without even thinking about the crank, I just assumed since it was a 5hp that it had to be 3/4"..... my bad :hammer:

I went ahead and stripped it down to the point where all I have to do is pull the side cover, remove the rod and pull the crank. Ill find someone here local that can either let me borrow their lathe or do it for me, Ill probably have a machine shop broach the keyway.

Do you think Ill need to replace the crank seals while Im at it?

And yeah the 4hp head isnt cracked, just a couple of fins broke around the plug area, I can clean that up with the die grinder and it wont look too bad.

I also have access to a powdercoater, has anyone ever powdercoated an engine or head before, and how did it hold up to the heat?

 

[briggs_boy]

i have a 4hp parts engine and tons of 5hp parts let me know if u need some.

 

[mclothier3]

PM sent :thumbsup:

 

[Nitrohorse]

LOL, well thats what I get when I dont look it over like I should, I jumped in and bought it without even thinking about the crank, I just assumed since it was a 5hp that it had to be 3/4"..... my bad :hammer:

I went ahead and stripped it down to the point where all I have to do is pull the side cover, remove the rod and pull the crank. Ill find someone here local that can either let me borrow their lathe or do it for me, Ill probably have a machine shop broach the keyway.

Do you think Ill need to replace the crank seals while Im at it?

And yeah the 4hp head isnt cracked, just a couple of fins broke around the plug area, I can clean that up with the die grinder and it wont look too bad.

I also have access to a powdercoater, has anyone ever powdercoated an engine or head before, and how did it hold up to the heat?

I would replace the seals while you have it apart. My philosophy is why take a chance when you already have it apart. You disturbed the seals when you remove the crank. New ones are cheap enough to give you peace of mind.
I know that during the time I built modified engines, no one I knew of ever powder coated one due to the belief that the coating retained heat. It might be ok with a stock engine though. Maybe someone else on here can give you more advise on powder coating a stock engine??
I know that there's a company down near Philadelphia, PA (Jet Coat) that does a ceramic powder coat on headers and their claim is that it helps to retain the heat inside the header and improves exhaust flow. So I'm sure that there's powder that can handle high temps.