Replacement engine for BCS 948 tractor/tiller.

[oughtsix]

Next Sunday I will be picking up a BCS 948 with a bad Honda GX390, tiller attachment (33" I believe) and a brush cutter for $1000. I have been investigating options for a replacement engine:
1) Rebuild the Honda GX390 - 69lb
2) Harbor freight 420cc 13hp Predator engine - 76lb - $389
3) Harbor Freight 450cc 15hp Predator engine - 80lb - $499
4) Harbor Freight 670cc 22hp V-Twin - 110lb - $999
5) Chinese Diesel engine - 406cc 10hp - 96lb (shipping weight others are actual weight.) - $630

My first thought was the Chinese 406cc Diesel but it is quite a bit more of an unknown quantity and I also am very nervous about all the extra vibration from a single cylinder diesel. I am sure the torque would be fabulous to have though.

The HF 420cc I am currently running is really nice and the extra power over the Honda GX390 is very noticeable with the snow blower. It rarely bogs down like the Honda did (which is what probably killed my Honda GX390).

For $110 more I am really thinking the 450CC Predator is the way to go. A bit more power is always a good thing! One of the things I love about bigger engines is that I can run them at a slower RPM while tilling and they don't bog down due to being at part throttle. The high tine speed is nice sometimes but it is also REALLY nice to have a lower tine speed sometimes, especially when breaking ground.

I fear that the 22hp V-Twin will be too much for the tractor and liable to to cause something to break. I really cherish the idea of the smoothness of a V-Twin though and being able to run it at a very low speed and still have enough torque to get the job done sounds VERY tempting. I also like the idea of running an engine at a fraction of its rated power rather than full out for stuff like snow removal.

I have 5 acres with 1 acre vegetable garden. I use the 28" snow blower a few times a year after a heavy storm as my main snow removal. I look forwards to finally having a brush mower to tame some overgrown spots on the property. I do not do any work for hire or do any commercial work with my BCS. Fuel usage isn't really a concern for me.

What do you guys think?

P.S. I have had a BCS tractor with locking diff and wheel brakes for about 30 years now. When I bought it is was already ancient and no BCS repair person has been able to identify it from the model number stamped on it (Very old Italian tractor). I replaced the 10hp ACME with a Honda GX390 decades ago (with the adapter and a new clutch) then again with a HF Predator 420cc 13hp, which is really nice, a few years ago. But the whole tractor is getting VERY old. The threaded lug for retaining the tiller blades to the tiller drive shaft on my tiller attachment broke many years ago and I replaced it with a tiller from a 715 with a dead acme (which I also have the rest of stashed in a shed). My 28" Snow blower attachment is quite a bit newer and I am currently using a spline to 3 dog adapter. The 948 should have the 3 dog adapter and it looks like it comes with a quick connect.

 

[super55]

Been years since I worked on a BCS but very similar story. Had replaced an old acme motor with a honda because the acme was like just like the looney tunes cartoons. Pull on it forever to start and then just stop for no reason whatsoever.

In small engines Im a fan of the saying no replacement for displacement and would go with the largest Predator motor that fits. Those motors are essentially Honda clones to the point where parts are interchangeable. Diesel small engines I'm not a particular fan. Reason being they are hard to pull start and require pressure relief. If your BCS is running long hours like running a chipper shredder I might consider diesel due to longevity and fuel economy.

 

[oughtsix]

I like the HF Predator engines and they have a great reputation. The 450cc Predator is really looking like the way to go. I am thinking the Predator 670cc V-Twin will be too heavy and possibly too powerful. At half the price I am thinking that the 450cc is going to be a perfect upgrade without being too much weight and power.

I appreciate the feedback! I don't have a shredder and doubt I would acquire one.

 

[super55]

I think you are right. That upgrade is going to move you from 9 to 15hp. With the gear reduction to the PTO I doubt you will find few if any situations where you are going to say you wish you had more hp.

 

[jbradley]

I have a 948, and its balance tends toward the engine side. I have had to rig weights on my snow thrower, and the 45" oil bath sickle mower is a bit light in the front, though not unusable. Putting a heavier engine on is going to throw that balance off even further. I'd rebuild the GX390.

The above comment is after I removed the 948's weights. It was much worse when they were in place. I had the tires foamed to regain the weight.

 

[oughtsix]

I have a 948, and its balance tends toward the engine side. I have had to rig weights on my snow thrower, and the 45" oil bath sickle mower is a bit light in the front, though not unusable. Putting a heavier engine on is going to throw that balance off even further. I'd rebuild the GX390.

The above comment is after I removed the 948's weights. It was much worse when they were in place. I had the tires foamed to regain the weight.

Good point! Do you have a battery on your 948? Balance is something I will definitely evaluate after I pick it up before I decide on an engine.

 

[jbradley]

I did add an electric start to mine, but I had the balance issues even after I added the electric start. It is so nice to not have to pull start that engine.

 

[oughtsix]

I picked the tractor up this after noon. It was about a 5 hour round trip drive.

Man this thing is a beast! I have an old BCS tractor sold by Mainline WAY back when. I have had it for 25 years and it must have been at least 20 years old when I bought it. I thought is was a big 2 wheel tractor with the locking diff and the steering brakes but this 948 is just an order of magnitude bigger in pretty much every way. The tiller attachment is MASSIVE! I had to take the tiller attachment off to get it into my truck and it took the two of us to lift the tiller up into the bed of my pickup. It is SERIOUSLY heavier than my tiller which is great because I broke the tiller that came with my old BCS/Mainline. The brush cutter is beefy too!

I think the GX390 on the 948 is pretty much toast. It has a new carb and a new head gasket and no compression. I think I will start by taking the Predator 420 engine off my old BCS/Mainline tiller and putting it on the 948 since I missed Harbor Freight this evening. I will try to post some pictures when I have it back together.

 

[super55]

If you get some time. Post a few pics. Love following these kinds of projects and seeing the end result.

 

[oughtsix]

Well here it is before I unloaded it. I thought I took more pictures after unloading but I guess I didn't

Not shown is the 30" combo mower and several accessories like a furrower.

After I got it unloaded I took the air cleaner off and disconnected the oil shutdown wiring. Man does this thing have compression (I am pretty sure the compression release is not working properly)! I checked the oil level and it was full to the point of just overflowing out of the fill hole with the engine level. I put a little starting fluid in the carburetor and it fired up after about 5 pulls. The seller showed me that he had stripped the valve cover retaining bolt and sure enough it was spattering out a fair amount of oil from the valve cover. After running it for 5 minutes I shut it down and wasn't able to get it started again.

I started pulling the GX-390 off of the transmission. The lower right engine bolt is completely rounded off and I wasn't able to get it to budge. So I started dismounting the engine adapter instead of the engine. There we 3 nuts on 3 adapter studs. 2 of them were very loose and the third one is under the metal piece that retains the plastic handle bar shaft cover. That is as far as I got.

The dead-mans switch lever is broken. There was no wiring or cables going to the engine. The cable for the throttle is missing the little knob that goes into the throttle lever. The dead-mans switch was not wired to the engine. The clutch feels like it might be stuck but I am not 100% sure.

I am guessing that the GX390 has a compression relief that isn't working. I bought a Predator 459cc engine to replace the GX-390. I haven't opened the Predator engine box yet so I can still return it. I think I am going to spend a fair amount to bring this tiller back to factory functionality. New throttle, clutch and brake cables. New dead man switch paddle. And a few other odds and ends.

Where is the cheapest place to get parts? Earth tools? I could not find the 948 on their site. Does the 948 take the same cables as the 850?

 

[oughtsix]

The (new) BCS 948:

I ran the GX390 one time for about 5 minutes. Here is the puddle it left:

Below is the leaking valve cover. I think the previous owner also messed with the valves and disabled the compression release which is why it is such a bear to turn over. The threads in the block for the valve cover retaining bolt are stripped so the valve cover can no longer be tightened. For $500 I can put a new more powerful engine on this 948 which I think will be worth it.

Top view:

The broken dead mans switch/paddle:

The clutch control cable looks a little questionable. I will have to see how much a new one is to decide to replace it or not:

The cables on the other (right) handle. One for brake and one for releasing the steering column so it can be repositioned. I think the outside one is the brake which looks like it should be replaced. Again I will have to see how much a new one costs.

The rest of the right hand handle:

A shot from the back:

Here is the 948 looking longingly at todays snow just itching to go out and play!

 

[oughtsix]

********************************** 735 ******************************************
Here is my first BCS, a Mainland 735 just in time for the first snow of the season today. I think it dates back to the 70's:

The original motor was an Acme 10hp. About 25 years ago I bought the engine swap kit and put a GX390 on it. A couple years ago the GX390 lost compression so I put a Predator 420 on it. Those extra CC's made a huge difference in how it handles the snow blower. The Predator 420 doesn't bog down like the GX390 did.

It is wearing the handles from a 715 which do not have a differential release lever or brake levers. Having the differential locked when blowing snow is a MAJOR disadvantage. This is the proper 735 handles:

The toggle switch is my version of a dead mans switch. Forwards is run. I can grab the switch and pull it back quickly to kill the motor.

This is the control shaft from the 735. The internal rod and cone shaped piece rusted through. This is the control column:

I have welded it back together a couple times. I think it is time to make a whole new column with a new disconnect rod and new cone shaped piece.

Here is the old 715 parts tractor still wearing its ACME 8hp engine. The ACME does run but has low power. A few years ago I scored a engine swap kit on ebay for a couple hundred dollars because I figured I could use it some day. I might put a new engine on this 715 and sell it.

This is the tiller gear box from the 735:

There should be a similar stud on the other side of the gearbox but it snapped off several years ago. So I put the gear shaft in the lathe and drilled out the stud (not really a stud because it is cast as a single piece) so I could rep0lace it with a bolt:

Right after doing the operation on the tiller shaft I found the 715 on Craigslist for $200 and bought it. I used the 715 tiller on the 735:

The rear cover plate for the 715 tiller (on the left) fell off in the middle of my garden somewhere. I need a buddy with a metal detector to find it. I will probably just order a replacement.

The 715 came with wheel extensions which I will remove before selling it.

How am I doing for a picture thread? (I like threads with lots of pictures to so I might have gone overboard a bit).

 

[Topzide]

You can put a heli-coul in valve cover bolt hole to fix that issue. Would be worthwhile to see if you can get the Honda working. If you had already budgeted for the other motor, put on the shelf if you get Honda running. Money in the bank down the road if it goes belly up on you. Who knows, another project may drop in your lap for the Predator motor. Great find and a beast of a 2 wheel tractor! Played with a lot of Gravelys and work on a couple BCS's with BS.

 

[oughtsix]

You can put a heli-coul in valve cover bolt hole to fix that issue. Would be worthwhile to see if you can get the Honda working. If you had already budgeted for the other motor, put on the shelf if you get Honda running. Money in the bank down the road if it goes belly up on you. Who knows, another project may drop in your lap for the Predator motor. Great find and a beast of a 2 wheel tractor! Played with a lot of Gravelys and work on a couple BCS's with BS.

Good advice. I had a heli-coil in the back of my mind. I have never done one before. I am a little worried about the compression release not working. I "think" that this might be fixed by adjusting the valves? I think it was over 40 years ago that my father showed my how to adjust the valves on out 63 Falcon but have never done it myself.

P.S. I was considering putting the GX390 on the 715 since I have a spare ACME to BS conversion kit including the new clutch then selling it.

 

[oughtsix]

I just spent a couple hundred on cables and a dead man handle bar lever. They should be her next week.
All new cables should go a long way to getting her back in good shape. New motor and new cables should make is close to a new tiller.

 

[otsegony]

Joel DuFour of Earthtools does a good job of explaining how to adjust Honda GX valves here:

 

[oughtsix]

It has been a little while. I forget where I left off. I went with the Harbor Freight 459cc Predator motor. The deeper I dove into the Honda motor that came on the tractor the more I found wrong with it.

3 of the studs were broken off of the engine adapter so there were only 3 left to hold the engine to the rest of the tractor. I drilled the broken studs out as carefully as I could but inevitably buggered some of the threads in the adapter plate. My local Napa fixed me up with some helicoils (or their version of them) and the proper metric replacement studs. That one guy on the end counter always goes out of his way to help me and was happy to dig through the parts shelves to find the right studs.

It took me a fair bit of Kroil and persuasion to get the screw out of the center of the clutch that holds it on to the GX390 motor shaft. To my horror I found that the shaft on the GX390 had a taper on it! I didn't know they made such a beast. Luckily I had a spare clutch for the straight shaft 459cc. I got it all put back together only to discover that I put the clutch too far onto motor shaft and the clutch lever was no where close to touching the clutch.

I went in for the night and looked up some of the Joel videos which told me exactly what I needed to know, the flat face of the clutch bearing needs to be 4 1/2 inches from the flat of the engine adapter plate for the clutch lever to engage properly. I ALSO found in the same video the the newer BCS clutches come with a spacer for a motor shaft and a tapered collar that clamps the tapered clutch to the straight motor shaft. The next morning I looked at the old GX390 and sure enough it had the spacer and tapered collar which I mistook for a tapered motor shaft. I removed the motor from the transmission, replaced the clutch with the original clutch using the spacer and tapered collar and sure enough everything fit together perfectly! It did take a fair bit of wiggling and pulling to get the 6 studs into the holes on the transmission and the clutch onto the transmission shaft.

I fired it up yesterday and it came to life nicely. I put the 30" HD Combo mower on (I used bolts because the studs were missing. I ordered new studs). The mower fired up nicely and took down my 2' tall overgrown grass. I was surprised when it bogged some on the taller wetter grass then I realized that the throttle was in the lowest position. After going to full throttle there was not really any more noticeable bogging down.

There is a 3" pto extension that came on this 948 tractor and with that the heavy 30" mower balanced very nicely. I am confident the even heavier 33" tiller will balance well to. My 24" snow canon will be where the extra weight of the motor will test the balance of the tractor. The snow thrower will be easy to add some weight to if needed.

I still have some more cables to replace (already have the replacement cables) and a few more tweaks and it will be good to go.

I did notice that my old blue version of the 30" combo mower is quite noisy. I found a video of the same mower online and it had the same scratchy noise. I need to take my deck apart to attend to some rust around the seams before it starts to cause some real damage. I will take a close look at the gear box at the same time. I know Joel doesn't like the combo mower but it is going to suit my purposes just fine. I did order and received a replacement blade that has swing tips on it in case I get into rougher ground where I might hit a rock or big stump. I will probably put this swing blade on when I rebuild the deck.

So far I am very happy that I went with the 459cc Predator engine.

 

[WesKootenay]

Thanks for the detailed post. Good to hear it has worked out OK.
I must look at the clutch on our 732, I had Earthtools rebuild it several years ago, now I need to adjust it or get a bigger left hand
I'm in the middle of replacing the 250cc B&S (blown) engine on our Ariens snowblower with a 420cc.

 

[jbradley]

The 948 has built in (add-on) weights that are on the engine side of the axle. I found that the balance on my tractor made it almost unusable for anything other than the 34in tiller box, so I took the weights off and had the tires foamed. The balance is much better now.

 

[jbradley]

In regards to replacing the engine, is it as simple as removing the 4 bolts to the clutch housing and pulling the engine off, or is there a bolt/screw that secured the clutch to the engine shaft?