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Hello all

Last year I worked on a similar engine used as a generator. I love those old Briggs flatheads, especially the 5HP I/C with sleeved cylinder, dual bearings and oil alert.
Si I won for five bucks the auction of the following motor, that was the description, I even don't know what was the usage/application :
- Briggs 5 HP
- Hard to start
- 19.05mm shaft (3/4'')

For this price I don't need to know anything else... best case I can make it run, worst case I'm happy to do some wrenching and I save parts for the other motor.
Furthermore with the current stay-home period, I have something to play with when the wether is bad.

I just pick it up today, it was close to my location. It's not locked up, but has low compression feeling on the rope.
Pics as I got it :











Paint is even worst in reality... very faded, it has dealt with weather for sure during at least a part of this 30+ years old - it's a 1990 model.
Even come more than half a fuel tank, and it is not rusty. Good new. It has oil (thanks oil alert - this force people to at least fill it) and it does not look too bad - will see better when I drain it.

Compression is low, spark plug is a NGK so not original, and changed by someone did not have a spark plug wrench (broke a bit of a fin and pliers marks on the plug).
But it has spark, that's good too! Spark plug is fouled and the gap is too small, 0.55mm instead of 0.75mm nominal. At least it the good reference, NGK BPMR6A that cross with original Champion RCJ8.





Time to remove the head to know more, but first the shroud with the recoil. The base is quite oily, I think replacing all the gaskets will be needed.
We can see inside of shroud is oily too. I don't know yet if I will remplace the crackshaft seals ? For flywheel side this mean I need to remove the crankshaft, but I'm not sure I will go this far - I not needed I leave the piston and the rod assembled.



Wow air filter is really old and dirty, and prefilter even worst... this can explain the look of the spark plug too.
Foam is close to disintegrating, but they are known for.

(I was limited to 10 pics...)

The 3 longs bolts are not in the right spot anymore, and we have marks on almost all fasteners. Someone did some repairs -or try to do- on it.
Inside there is some carbon build up, I'm not sure the valve are sealing good. Cylinder looks ok, nothing I can feel with my fingernail. Some traces of use of course, but crosshatch is still visible. No play of the piston in cylinder at TDC.
Good new, as if the cylinder is toast, the engine is toast too. But some cleaning to do for sure...







About low compression, I think there is two problems. First, head gasket is damaged, it is leaking at the most right bolt on picture. We can see the missing part on the gasket (still on the head below), the traces on the block between cylinder and bolt - and this bolt had some carbon built up on it !



The other source of low compression are the valve, at least the intake. I can rotate this one by hand when closed, and when I removed the air filter I was able to hear a "pschhhh" from the intake.
For sure, I have to set the valve lash and do a good lapping to make them seal properly.

Others traces of "human being there" in the past, including coil rubbing on the flywheel and customs "clamps" for breather tube, with RTV in bonus. This is not needed, even if those rubbers are always a bit loose, they are not cracked. So for a crankcase breather that's fine.
So definitely someone tried to make it run correctly, scratches and marks are there, but nothing broken until now, that's a good start.


Current state of disassembly. I think the carburetor and the muffler was the last disassembled things - at least recently, not recent traces on the valve cover / breather. This is however where I need to go to fix the valve issue, but the downside of this engine is you need to remove the muffler, the carburetor, the fuel tank and bracket/throttle plate to access it. When you have a shop and you need to put this on a bill, this often make the engine go to trash - and sometime on auction for close to nothing, to make someone else happy



To be continued...

I continued my work on this 5HP (and my monologue here )

This was a bit less fun, has after removing tank and carb, this was only cleaning. Greasy stuff with dirt all around the block, but I need something clean to be able to open the crankcase.

Checked the valves lash, no surprise with intake, zero lash (as I was able to turn the valve with finger when it was supposed to be closed). Exhaust is not bad, more in the 0.20mm range instead 0.25mm, I am a bit surprised - I would have thought exhaust is often worst than intake ?



Start to looks better, even if the paint is flaking and goes away with the dirt...

Those horiz. IC motors are pretty tough. Clean the carbon, lap the valves, get the clearance right, new gasket, probably good to go. And good to see those cooling fins on the cylinder are nice and clean.

I love working on them to, check the valves and like tom3 lap the valves those were famous for the exhaust valve burning a spot of them, that cylinder looks great, get someone with a valve grinder to light face them or it can be done on lathe, Joe

Thanks for your comments tom3 and Its Me. So I'm not alone to love them

Yes I need a head gasket for sure, don't know if I will buy the whole gasket set, the motor was pretty greasy - so some leaks exist here and there. For sure the dipstick tube oring is toast, but other probably too. Thereupon, I don't know if I will keep this plastic dipstick... it is in bad shape and I prefer the "classic" oil fill and check at the bottom of the crankcase (but it was probably added for more easy access). Does anyone know a "plug" part number exist to close the hole in the crankcase cover ?

And of course I'll clean all the carbon in the head, on the block and the valves, grind the tip of the valve stem to adjust clearance. Check valve play in block/bushing. Hope the seats and valve are in good shape so I can lap them so they seal nicely.

I plan to remove the flywheel to, to check the crankshaft seal and degrease all the dirt behind. But I have to buy (or build) the tool for starter clutch and the flywheel puller. Will see on the weekend, less time during the week.

I progressed in the disassembly this weekend

First I made a little "tool" from a flat steel bar, two holes and a bit of grinding to allow me remove the starter clutch. I know a tool exist, but time to order with current restrictions and shipping that will double or triple tool cost, I went DIY. Worked great with a few tap on it with a small hammer while holding the flywheel.

I was surprised to see flywheel without holes to remove with a puller ? It is always like this with this kind of long crankshaft ? (because of this old starter clutch usage ?) So I went the way with prying behind the flywheel and small taps on the crankshaft... was very easy to pop off, second try ! nice

Removed the coil and now it's time for a good clean here ! Done.



Next I jump to the valves. Hard time to remove them because I was convinced I need the valve spring tool to remove them... (don't know why...) in fact you only need to put the retainer in the right position and push it with a flat screwdriver (I have the cup retainer style). Waste of time... but at least its done.
All good carbonated up, intake even on the sealing surface. Have to clean all good valve and seat and lap them.

I checked the valve play (stem to guide), and exhaust as some. Guide is good (6.40mm, reject is 6.73mm according to my old post https://www.lawnmowerforum.com/threads/briggs-5hp-ic-generator.52044/page-7) but anyone know the valve stem rejection / minimum size ? At the middle of the stem I am at 6.15mm, nominal diameter of the valve is 6.25mm. Nominal guide is 6.35mm so I almost doubled the play from 0.15mm to 0.25mm. Not a big deal if guide is allowed to be worn to 6.73mm, this mean 0.38mm of clearance/play even with no valve stem wear.

But anyone has an official reference or a place I can look at normal stem values ? Thanks !

I cleaned the valves and inspected them more thoroughly. I am a bit concerned with them, some pics below :


- The intake has quite a deep groove, is this a problem ?
- The exhaust has some "pitting" on it, should I clean it with something more abrasive, like a scotch bite pad ?
- I'm still looking the minimum acceptable valve stem diameter

Any advice will help me. I don't have the experience to say if those valves are good and I just have to clean them and do the lapping or if they need to be changed ?

Thanks

So finally, I clean the valve good and I lap them. The exhaust had a little bit of pitting, but should not be a big concern.
The intake worries me a bit more, the ring is clearly at the outside. An the seat "seating" size is at max of tolerance according Briggs manual. Anyway, I give it a try.



After that, it was time to grind the valve stems to set correct clearance, 0.25mm EX and 0.15mm IN.

Next and last big thing to check : open the crankcase. I was not really worried as the piston does not looks to have play regarding to the crankshaft when I move it up and down. But its better to check and it is also a good opportunity to clean the block. The oil wasn't too glittery, tha'ts always a plus. And some black deposit at the bottom, even perhaps with a bit of moisture. All is clean now
I think I am the first to open the crankcase cover, the gasket is hard has a rock. No tool traces on the folding locks of the connectig rod bolts - all seems original. But someone over tighten the bolts of the cover for sure, trying to make it a bit less leaky I think (but this does not work).



Next step, carburetor, order engine gasket set and carburetor overhaul set I think ?
Don't know if someone is still reading ? lol

Yes the intake valve should be replaced. How is the valve guides? Is there considerable amount of side to side movement. Usually the exhaust guide is the one that wears the most.

Oki... But I don't have seat cutters and I dont plan to buy some, I checked and they are way too expensive, like 300-400$ !
If I only buy a new valve this make a difference without touching the seat ?

Yes valve guides are within specs, intake is perfect and exhaust as a bit of play - but the valve itself is also a bit worn. Detailed measurement above in post #7

Intake guide is really nice, I had to file the valve stem (where the keeper retain it) to remove it without scratching the guide (its only aluminum in the block, bushing is available only for repair on intake). Intake valve has no wear too on the stem, was very surprised to had so much wear on the valve face.

You can drop the engine off to me.
I will set the valve lash for $ 20 ( Aus) but the freight might be a bit steep.
Most REAL mower repair shop will have a Neway Small Engine set of cutters .
Older ones will have a set of stones
Doing a SV valve lash takes about 10 to 20 minutes.
Pulling everything off to get to them takes near an hour .

Thanks for proposal, I would be happy to have you doing the seats for me, but as you said, sending the block to you is 60$ US ! And I think about the same for the return... so we reached the value (or more) of the running engine
And here, nobody do that on old flatheads, and on OHV you just have to buy a new head. I don't know how much it cost per hour for a small engine shop (I do maintenance myself) but should be at least 100$/hour.

So if I buy a new valve, unless someone has a stone I can buy for cheap to do it, I will not touch the seat. And even with a stone, you need a tool to grind/dress it at the right angle...

Hi, lot of time has past since

Busy busy summer, and I tried to order parts from firedog.com, without success. They won't ship worldwide during the COVID pandemic, ant I can't contact them because their formulary system always fail me at the captcha test like I am not human... so I can't order original parts, its a bit a shame because they have a pretty good inventory of Briggs part (and even Honda) and reasonable international shipping costs.

After loosing two months, I finally order a chinese full gasket set for 12$ shipped... It's worth a try, I plan to use Permatex Form-a-Gasket anyway because I had bad luck even with original parts on my last crankcase covers, they leak both a bit.
The kit looks good, one nice point si it include all the gaskets - even options like Oilguard sensor or dipstick tube, and even crankshaft seals !



I cleaned all the gasket surfaces, applied Permatex on both side of gasket, let it dry a bit and after assembled all.
Double checked the camshaft timing, on engines with a bearing I learned just recently the dots are to line up as on the picture.


Cleaned pistons and head too; new head gasket - without Permatex this time




Now engine is assembled, with fresh oil. Just have to put gas and test tomorrow
And then, do the adjustments, finish assembling air box and put new air filter.

I did the governor adjustment like in this video, but seem quite loose... will see how it rev, I prefer too low than too high :

Seem to have decent compression at the rope, even if I did nothing to piston, rings and bore

Looking good!!!!!

Thanks

Was able to short test it outside, after a few pull on the rope (carb diaphragm has to fill bowl in the tank to allow fuel to the main jet) it started and ran pretty good I just tested a few minutes without air filter/box, let it warm 5 minutes and looks it can idle and rev. I have to adjust both because idle is low and I don't think its reving 3600rpm, more in the region of 3000-3200 I think - I have to put the tach on. I will do this when the weather will be better, it's raining almost continuously since the quick test.
I have to check how to adjust max RPM on this governor setup.

One last pic of outside test; I will try to do a short clip of engine running next time - its more "fun" than pictures




I forgot to mention the guy teach me the right way to set the timing, James Condon :

I like his channel, I works mostly on generator, most of the time commercially lost causes. He is pretty thorough and meticulous, discovered him recently but when I have time I like to watch his channel