Bolens 1668 Diesel Conversion.

Well as you may know I picked up a nice freebie Bolens tractor yesterday with a crippled opposed twin:









Poor thing had the #2 cylinder head packed up with mouse nest and popped the exhaust valve seat. Normally I would attempt to fix it, but it most likely could use a tear down to be inspected and also re-gasketed, as it looks like it leaks oil from pretty much everywhere.

It's a shame, but I have a nice Yanmar L100 that needs to go in something so that's the direction we're going! Should be neat.

So anyways, yesterday I got the opposed removed, and used my parts diesel for mock-up, so I didn't scratch up my nice purty one.



Checked for clearance, and found some minor trimming was needed:





Not too bad at all! So I got that done and semi-cleaned up:





Tried to make it look as clean as possible, didn't turn out too bad!

Now here's what I was waiting to see!







Man she really fits well! I think it looks pretty cool too, haha. Next I'll have to work on the mounts, and then figure out something for a driveshaft adapter.

So yeah, this is gonna be my little project at home for a bit, should be lots of fun. Let me know what ya think!

That's really neat Allis. All the better for putting a blade under it

Yeah you guys got me thinking about that now, haha.

That would be pretty nifty.

That would be a perfect home for a diesel!

Thanks fellas.

Well another update here, I actually got the engine mounts done last night, but it was too dark to get any pictures. Nothing special there though, just some 1/4" plate and 3/8" bolts. So she's mounted, but it needs the driveshaft adapter now. That's what we did today!

After planning all morning, here's the few parts I need to make the adapter:



On the left is the recoil cup from the Yanmar, and in the middle is the original driveshaft hub off the oppy from this tractor. The other two pieces are simple brackets I made.

So basically the plan was to weld the brackets into the cup to allow for a place to bolt the stub shaft.



Used a digital caliper to get it centered, I went all the way around until I got a measurement of 1.664" in every spot.

Then I carefully welded it while checking the measurement after every tack. Eventually I got 'er fully welded up and trimmed the excess pieces off.



As you can see the cup can easily be bolted to the flywheel with the stub shaft removed.



Should hold up fine, but I'll be keeping an eye on it for the first little while.



Fits great! Then, the moment we've been waiting for..


The test drive!!



Man she works good! The transmission is smooth and quiet, same goes for the hydraulic lift. I'm very happy with it so far.

I don't have the throttle or electric start hooked up yet, so I'll probably work on that stuff some more today. Also gotta change the exhaust and make new hinges so the hood can be put back on.

But anyways, I'm very happy with the conversion so far, let me know what ya think!

Looks great Allis! I bet that driveshaft adapter will hold up alright, they don't see much torque.

So, got the turbo manifolds done yet?

I'll get there, haha.

Worked on a hand throttle setup yesterday afternoon, wanted to come up with something that was stupid simple and sorta heavy duty:



Turned out kinda neat looking, haha. I got it all welded it up and it works great, so I'm happy.

Gotta do some wiring next!

Oh I like the linkage for the throttle!

How is the adapter you made for the driveshaft working out?

It would be nice if you would post a video of the tractor running on youtube...please

Thanks Carl! The driveshaft adapter has been fine so far.

I did take a short video right after I got it going, I'll probably upload it soon.

Little more tinkering on the ol' Bolens over the last couple days. I got the hand throttle welded up but never tried it 'til yesterday, it works quite well!



Decided I wanted to re-do the wiring for the diesel, so I removed the entire harness and did the simple momentary push button for the starter.



Cranks over good! Still need to rig up a charging system, but I have a plan for that.

Last thing I did is something I've been wanting to try for a little bit. I figured since the choke lever is no longer needed, it would be handy to hook it up to the decompression lever on the rocker cover. The choke cable happened to be the perfect length, so I routed it and made a little bracket to clamp it down:



Pulls it and releases it nicely:





Perfect! So now I have the throttle, decompression, and starter all operable from the seat:



Fired 'er up and everything works nicely:





Pretty happy with that stuff. Next I should probably try and make that hood fit, haha.

Seems pretty ergonomic having everything to run it right there. The throttle is the kill switch too so that's nice.

Yeah I'm gonna do away with that evetually though. I never liked the idea of having to guess where the idle is so you don't shut the engine off, kinda tacky.

I have a couple different ideas for a remote shut-off.

You going to run the factory fuel tank and remove the one on the engine? And make a new exhaust? Will that be all the hood needs to clear or is the valve cover too tall?

I was actaully planning on running the original tractor tank, but the one on the engine fits under the hood quite nicely so I'm sorta tempted to just leave it there. We'll see I guess.

The valve cover clears fine, it's just the muffler causing issues so I'll have to come up with a different setup.

Any ideas for the exhaust?  You leaning stack? Side can and blow it forward? other?  Still on the fence?  HAHA... Loving where this is going.  Do you think the cup will stand up to any pressure of a load on the rear end over time?

Using the stock tractor tank as a reserve might be cool.

MightyRaze wrote:

Any ideas for the exhaust?  You leaning stack? Side can and blow it forward? other?  Still on the fence?  HAHA... Loving where this is going.  Do you think the cup will stand up to any pressure of a load on the rear end over time?

Still undecided on the exhaust, haha. There is probably a pretty good amount of stress on the starter cup with the hydro trans and all, but I imagine it will hold up fine. Still keeping an eye on it for bending or stress cracks.

TheBeal wrote:

Using the stock tractor tank as a reserve might be cool.

That would be neat, but this thing uses so little fuel it wouldn't prelly be practical, haha.

Took 'er for a nice long ride in the field next to my house this evening! It's a pleasure to drive, the transmission and steering are nice and smooth, and the torque from the diesel is nice as well. Can't wait to put 'er to work!

Okay so I did some more tinkering a little while ago, but I haven't posted it yet so here we are.

Wanted to get the hood mounted back up on this thing, so I had to figure the exhaust. Tool the stock muffler off to get a good measurement of the flange:



None of the ones I had lying around fit unfortunately, so I decided to just make a flange instead.

Figured some 1/8" plate would work nicely.



And the finished product:



Not too bad! Bolted it up and welded a pipe fitting in:



Then the I finally decided on a muffler:





Just clamps on as you can see. That'll be nice in case I ever decide to change this setup in the future. The original exhaust for the opposed twin exited out of the grille, so I tried to make this one do the same.

Made a bit of a deflector to get it flowing the right way:



Flipped the grille mesh 180° and the hole almost lines up with the new exhaust, but not quite.



Oh well, haha. Then I had a rather nice surprise when I tested the headlights out:



They both work! Haha, didn't expect that. Got 'em wired to a switch in the dash, so we're all good there.

Then finally, a shot with the hood on:



Definitely nice to see it back on there! She's a good looking ol' tractor tractor if you ask me, haha.

Let me know what ya think!

Nicely done AK.

Why thanks Mighty!

I did some messing around with a remote shut-off today because I didn't really like having to use the throttle lever, I wanted to have a solid spot for the idle so that had to change.

I messed around with a detent for the lever but it didn't work out too well, so I found a way to use the original throttle lever on the dash!

Here's the cable on the engine.

Run:



Shut-off:



So basically it just closes the fuel rack in the off position, and in the run position it just kinda hovers and lets the governor work as it should. Pretty similar to what I did with the de-comp control.

Made a simple stop for the throttle lever at idle:



Good ol' 1/4" bolt! Also I labelled the shut-off to make it look more official:



Tested it out and everything works great, also I picked up a set of four Ag tires on rims so I figured I'd throw a pair on the old diesel Bolens:





Still need to paint the rims but it looks pretty neat! Really happy to have that shut-off done too.

Let me know what ya think!

RichieRichOverdrive wrote:

All the better for putting a blade under it

Well since you mentioned it... look what I did!







Yep I finally did it, haha. I just cut the blade out of an old water tank, and made the other brackets myself. It has a couple different lock in positions for the pivot.

It works great so far!

Nice job on the swap! Looks factory. Nice job on the blade too that thing is pretty slick!

Thanks Blake! The blade had definitely come in handy so far.