New engine, 79cc predator for high mobility air compressor

[oil pan 4]

I haven't fired it up yet. I'm rebuilding my ancient 5hp Briggs flathead air compressor to be lighter and easier to move and easier to start. The old flat head needs a squirt of carb cleaner if I want it to a least pop on the first pull. It really really don't want to start when it's cold during the winter.
I'll probably sell the old flathead it on fb marketplace.
The predator 79cc has a foam air filter, I'll be spraying that down with K&N air filter oil to keep the dust out out of the engine.
For break in oil I figured I would use the sj rated STP oil they sell right next to the predator engines.
The engine doesn't have provisions to attach the unloader bullwhip to the throttle lever, but I should be able to figure it out.
I'm putting a smaller lighter air compressor on those tanks too, HF used to sell an aluminum body, head and pulley compressor years ago, I made an electric air compressor out of one. I'll poach that compressor off my electric and replace it with a cast iron one from HF. That aluminum twin cylinder compressor can still be found on the assembled wheelbarrow air compressor they sell currently.
So for break in oil changes I'm thinking change the oil a 1hr then again at 3hr?
Has anyone used any of these 79cc predators? What are they like? Easy to start?

 

[Ausfahrt]

I don't have any experience with the 3hp 79cc engine that you have but the larger Predator engines that I bought have been solid. The idea of repowering old equipment to keep it functioning as intended appeals to me and applaud your efforts.

Are you concerned at all about replacing the original 5hp engine with a smaller one? Any pictures?

 

[meep]

I had a smaller predator engine, one of the few I’ve heard of with problems. The compression release would get stuck in run mode often, but I learned to tap it smartly with a hammer where the camshaft bearings were on the pto side - worked every time. Sipped gas, burned clean, and I ran it hard on a pressure washer.

I would think you’d want the 212 CC motor? It’s probably a closer power match. If you go with the 3hp and it’s under-powered however, you can use a smaller pulley and carry on - it would be a touch lighter - however I think either will be less weight than the old Briggs.

 

[oil pan 4]

I had a smaller predator engine, one of the few I’ve heard of with problems. The compression release would get stuck in run mode often, but I learned to tap it smartly with a hammer where the camshaft bearings were on the pto side - worked every time. Sipped gas, burned clean, and I ran it hard on a pressure washer.

I would think you’d want the 212 CC motor? It’s probably a closer power match. If you go with the 3hp and it’s under-powered however, you can use a smaller pulley and carry on - it would be a touch lighter - however I think either will be less weight than the old Briggs.

Oh I already have a really big Honda gx200 powered compressor with aluminum and cast iron compressor it's got about 4 foot long tanks it weighs nearly 140lb. This is just going to be my small and easy to move tiny compressor. This little one has smaller nearly 3 foot long tanks, it's going to be light. I'm going for under 80lb, I'm not even going to put a belt guard on it.
This is for when I just need to fill a tractor tire, or car tire, blow dust around, blow down a hot water heater, sand blast something tiny like a crack for a few seconds so I can get the dirt out of it and weld it, run a half inch impact for one tire. Or God forbid a roofing nailer.

 

[oil pan 4]

I was about to put the engine on the tanks last night and maybe fire it up. Figured I better magnaflux around the bolt slots. Sure enough there are several cracks I couldn't see.
My magnaflux powder is just grinder dust that I swept up from around the bench grinder.

 

[oil pan 4]

I welded up 4 cracks with my gtaw rig.
I fired it up and ran up a half hour on it so far. With a 2.5 inch pulley it builds air pretty slow I'm going to see if tractor supply has a 3 inch pulley.
I had that 2.5 inch 5/8 keyed bore pulley in my junk collection and figured I would try that first.
It works as intended so far.

 

[oil pan 4]

Real easy to start, starts first pull every time like a Honda engine, sips fuel. Not even filling the fuel thimble all the way up, about 3/4 full gives an hour of run time.

 

[oil pan 4]

Ran the little 79cc air compressor for all it was worth yesterday to obtain a maximum oil temperature.
Full tank of gas, ran till it was out of gas, 90f outside, maintained 70 to 110psi in the compressor tank, never let the unloader trip.
The oil temperature when it ran out of gas was 210f.
So use your favorite flavor of oil that ends in 30.

 

[#18FAN]

Ran the little 79cc air compressor for all it was worth yesterday to obtain a maximum oil temperature.
Full tank of gas, ran till it was out of gas, 90f outside, maintained 70 to 110psi in the compressor tank, never let the unloader trip.
The oil temperature when it ran out of gas was 210f.
So use your favorite flavor of oil that ends in 30.

A 79cc engine can’t be running a big pump at all.

 

[oil pan 4]

A 79cc engine can’t be running a big pump at all.

Yeah that's the point.

 

[oil pan 4]

Well the mini compressor has been in service for a year and I've barely used my big gx190 powered compressor.
My little 79cc has been my go to machine.
I'm thinking take my Honda engine off there, stick a predator 212cc on there and sell it.

 

[oil pan 4]

Well I tried to start my little air compressor when it was 15f this morning. Didn't start. I was like pulling the air compressor through the mud by it's rip cord.
It's got supertech 10w-30 in the engine and straight 30wt SA oil in the compressor.
The oil in the compressor is looking kinda black, probably change that over to 20wt since I can put my hand on the compressors oil sump after it's been running for 45 minutes so it doesn't get hot enough to need 30wt.
For the engine I'll put PP 5w-30 I think I have some already open. If not I'll go buy a quart of 0w-30 something or other.

 

[repairman54]

I had to go to a 0w - 30 oil to recoil start a BS 5600w unit at 0f. 5w was too thick for it to spin over fast enough at that temp. to fire up, even with the 5w I was lifting that heavy generator off the ground with the recoil.

 

[oil pan 4]

Another 15f morning. I changed the oil over to 0w-30. Seems to turn over a little easier, but not enough difference to make a difference.
I left the Mobil 1 0w-30 and the supertech 10w-30 outside over night.
Just giving the bottles a shake the 0w-30 isn't terribly thinner. The 0w-30 at 15f seemed about as thick as the 10w-30 at around 25f. As it warms up I'll give the bottles more unscientific shakes.
Still need to change the compressor over to 20wt.
There should be a bigger difference going from straight 30wt to straight 20wt than going from 10w to 0w.

 

[meep]

Does the belt drive not use some kind of clutch on these? Seems like compressors have some sort of “idle down” clutch when the tank is full?

 

[oil pan 4]

Does the belt drive not use some kind of clutch on these? Seems like compressors have some sort of “idle down” clutch when the tank is full?

They have an unloader valve.

 

[dlundblad]

If you absolutely need to run it in the winter, I’d give a 0w20 or 5w20 a try for the engine. If it pulls just as hard as a 30 weight oil, then it is what it is a just go back to that. With an unloader valve on the pump, would we see any difference in a 20 or 30 weight?

My vertical oil lubed compressor’s manual specifically said not to run it below freezing temps. If I need to fill my tires or need a few bursts of compressed air, I either pull from the tank with the motor off or just use my little pancake compressor.

 

[oil pan 4]

I put 0w-30 in the engine halfway up the dipstick and filled the compressor up about 1/3 up the low/full line with 20wt. Before it was all the way full on both.
And it's 16f out this morning....

 

[oil pan 4]

It fired right up after several pulls.
Going from full on the dipstick 10w-30 to half on the dip stick 0w-30 made a difference but not a huge difference.
Going from full compressor straight 30wt to 1/3 up to the full mark straight 20wt made a big difference.
In my totally unscientific and highly subjective shake test the straight 20wt appears to be more viscous than the Mobil 1 0w-30 at 16f.

 

[oil pan 4]

I went and pulled on it some when it was 0f. I didn't need to start it, wasn't really trying to start it. Just wanted to pull on it to see if I got that "dragging it though the mud by the ripcord feeling".
I did not. Seems like I was able to turn it over fast enough to fire it.
Some more pulling or a squirt of starting fluid, carb cleaner or brake cleaner I know it would fire.