My Small Engine Projects

MightyRaze wrote:

Sweet... don't know why but your idea in this thread is very interesting.

Thanks, I seem to have a thing for collecting engines and not working on them and the plan for this thread was to motivate me to work on them. Don't think it's worked lol 

AllisKidD21 wrote:

Yeah I agree, the steam engine idea is super neat!

Thanks Allis, a steam engine would be pretty cool.

RichieRichOverdrive wrote:

Be careful with your boiler, superheated water is dangerous stuff.

Yeah, and it's at high pressure. I don't really think a boiler is feasible in the near future but it would be nice. In the meantime I need to pull the engine apart and take the cam out to modify the lobes and hopefully make it more efficient.

I've chosen 3 engines to fix up/work on now that it's coming into summer and hopefully that will get them off my to-do list.

No 1: A 1978 Flymo lawn mower. I think I have a thread on this somewhere on the forum but I'll just detail the project in here. I need a rough cut mower to cut the grass verges on our lane so this would be perfect. It's got a 3.5hp Briggs (not the original). The plan is to drill and tap the crank shaft for the blade adaptor, order a carb rebuild kit (it's the older auto choke carb) and fix the rear 'grass gate'. It's been sitting like this for ages and it's time to resurrect it. 


No 2: Build up a 3.5hp Briggs with float carb, no governor, AK's advanced timing trick, performance exhaust, porting & polishing. I think it would be a cool little engine and I might put it in a small RER or something similar.



Finally No 3: This is a 6hp single cyl diesel engine I've had for a while. Plan is to build a hydraulic log splitter for splitting the firewood, it's a shame to see this one sitting doing nothing so I think an application where it's sitting on a steady RPM is better than if it was on a go-kart or tractor.

That 3.5hp build up should be pretty neat, looking forward to seeing That!

You wouldn't be interested in selling that diesel would you? I have a JD 110 that would just love it!

AllisKidD21 wrote:

That 3.5hp build up should be pretty neat, looking forward to seeing That!

Yeah I'm looking forward to building it. Will be interesting to see what power difference it has compared to the stock 3.5 in the mower. Btw, the carb I'm planning to use is a Walbro off a 3.5hp Tecumseh. I can't find it at the minute but I'm sure I still have it.

Double W Cross Ranch wrote:

You wouldn't be interested in selling that diesel would you?  I have a JD 110 that would just love it!

The cost to post it might be a little steep, haha. Na, she's staying here, I think her powering a log splitter would be pretty cool. Also it would save my back from swinging a hatchet

MatthewD wrote:

Double W Cross Ranch wrote:

You wouldn't be interested in selling that diesel would you?  I have a JD 110 that would just love it!

The cost to post it might be a little steep, haha. Na, she's staying here, I think her powering a log splitter would be pretty cool. Also it would save my back from swinging a hatchet [smiley]https://2img.net/i/fa/i/smiles/icon_razz.gif[/smiley]

Haha I was mostly joking. But would you happen to know where the engine came from?

I knew that  I got her from ebay.

Started on the 3.5 Briggs build up, I'm pretty excited to work on this project.

Put on the starter cup & tightened down the flywheel nut and removed the vane governor.

Found a shroud that is in reasonable condition. The date on it is 00, but the original shroud says the engine is 02. The original shroud also says it's a 3.75hp Briggs but I can't see any difference in the blocks or anything. 

Recoil with the innards added.

Looks like a 3.5 Briggs now.

Found the Walbro carb I'm going to use. Off a 3.5hp Tecumseh.  

Measured the diameter of the intake, it's about 20mm. 



Here's the only markings I could find on the carb, it's not a great picture, I'll try and get a better one tomorrow.

This is approximately where the carb will go. I think I'm going to get an M20 washer, and use that as the flange for bolting the carb to. Then weld an intake pipe with a 90 degree, and weld that to the original metal intake tube (you can see the tip of it just left and down a bit from the carb)

I like that diesel. I have about 5 of those 3.5HP Briggs classics at the moment.

Nice... have a plan for the motor when complete?

muckmudd wrote:

I like that diesel. I have about 5 of those 3.5HP Briggs classics at the moment.

Thanks Muck, I had 5 of the 3.5 Briggs at one point too.

MightyRaze wrote:

Nice... have a plan for the motor when complete?

Thanks Mighty! I think it would be cool in a little RER or mini lawn tractor, or I could put in it a push mower. Who knows

Decided I'm going to put the carb here, because in the other configuration I couldn't adjust the idle/fuel mixture screws and the intake tube would be longer and would have a sharp 90 degree turn in it.

Removed the throttle plate and coil to remove intake tube

Intake tube has a few dinges in it but I think this is to clear the coil and block.


Onto the air filter, here's the Tecumseh air box.

Took off the top and I plan on cutting the bit with the holes in it to use on the Briggs.


Found the Tecumseh intake manifold with the throttle linkages and stuff but I don't think I could use it on this.

Removed the muffler and valve cover because there was some oil leaking out of the valve cover. One of the bolts was loose so hopefully it will stop the oil leak.

Cleaned it up and put the valve cover back on. Also installed a thread on muffler, it will do for now and means I can access the valve cover without removing the muffler.

Looking good so far Matt! Got any specifics on the exhaust plan?

Yeah, those gaskets usually last as long as the engine does.  Nice work dude!

AllisKidD21 wrote:

Looking good so far Matt! Got any specifics on the exhaust plan?

Thanks Allis! I could run a gutted out 3.5hp exhaust, or I might leave the exhaust until I figure out what the engine is going onto.

Double W Cross Ranch wrote:

Yeah, those gaskets usually last as long as the engine does.  Nice work dude!

Thanks W!

Stripped the carb down. It was surprisingly clean after sitting in a dusty shed for years but I thought I would clean it up really good anyway. 

'W' for Walbro!

Going to boil the bowl, carb body, jets in water and vinegar to clean them up sparkling.

It's probably Walbro, but maybe 'M' for mikuni?
naw that ain't a mikuni....

It's definitely a Walbro. I know Tecumseh used Walbro carbs a lot.

Boiled the carb in water and vinegar today, outdoors style!

This is a very interesting technique.  I'm so used to using aerosol carb cleaner and compressed air because it's quick, effective, and cheap.  However this method won't cost you really anything.

Yeah, compressed air and carb cleaner work well, but I find the movement of the water when boiling helps to shift dirt that is really stuck on or really gummed up carbs. This carb didn't really need boiling but I thought I'd do it anyway. Will build up the carb tomorrow.

Hmm...I may do this to my John Deere carb, it's so stuck that the butterflies won't even budge with vice grips.

I'd maybe soak that in some engine oil or something first. That'd probably free it up and then you could clean it all out afterwards.

Yeah, the boiling trick probably won't free up that carb if it's that badly stuck, I find soaking stuff in ATF helps to loosen things up.

Got the carb all cleaned up and reassembled.

Intake tube made up, the dinging is to allow it to fit between the cylinder head and the coil. The stock one is like this too.

Now here's where things go a little pear shaped. I had intended to weld my new intake tube to the old one, but it turns out it's aluminium, and I can't weld to it with my arc welder. 


So I think it might be better to use a carb/tank combo that normally comes on these engines but with some mods to allow it to run better.

I then decided to do some work on the lawn mower as the rough grass I need to cut with it is growing fast!
Pulled her out of the garage yesterday and laid all the parts out on the ground, she was pretty dusty and there was a slight bit of damp round it. 



All reassembled. Put the cylindrical muffler back onto it because I think it suits the mower better. I put some fuel in it and she fired up and ran great after adjusting the carb. The carb probably needs a new carb kit (it's the older style auto choke carb) as it's missing the little spring in the diaphragm so the operation of the choke is slower than normal

However, I couldn't fit the blade because the crankshaft bolt hole is a little... shall we say messed up? 

Alright, I'll confess it was me  When I got the engine a few years ago, the shaft was really long so I cut it down to the right length but found there was no threads in that piece. So I tried drilling a hole but it didn't turn out too good. The hole isn't even in the centre and it's too large and I can't seem to cut decent threads in it. I was wondering if I could fill the hole with weld and start again? Or would it be too hard to drill/tap threads? Your thoughts would be greatly appreciated

You should pull the crank, weld it up and take it to your uncles lathe to drill and tap it the right way

I’d say screw it and weld the blade and adapter to the crankshaft lol

Crazy_Carl wrote:

You should pull the crank, weld it up and take it to your uncles lathe to drill and tap it the right way

Good idea, that may be the best solution.

CraftsmanQuad19 wrote:

I’d say screw it and weld the blade and adapter to the crankshaft lol

I'm sure there's a better solution haha. I'd like to be able to remove the engine if I need to CQ.