Bobcat 721 engine options

[kylem1]

Hello, thank you for providing a great site. This is my first post. I purchased a Bobcat 721 with the deutz f2l-411 2 cylinder diesel last December. It was not running, I replaced the fire rings, adjusted the valves and it got it running. It starts right up everytime. But, it smokes, a lot of smoke a lot of blowby and it's getting worse. I tore the top end off and took it to a machine shop, the cylinders are worn down to around 20-25 thousands, and Deutz in Germany does not sell oversized rings anymore (that was my plan, bore the cylinders, new oversized pistons and rings). Now, I'm looking at $1000 for two new cylinder jugs, $250 for standard size rings and $800 for custom made pistons. The reason I am posting is I'm looking for any good advice on repowering the machine with say a f2l 511 or Vanguard or any other engine. Someone with some experience on fitting a different engine up to the hydraulic. I love the little deutz engine, I've used it all summer to load old dead ash trees and spread dirt and gravel. It's just investing so much on an out dated engine makes me think I'm nuts. Thanks for providing this forum, it's great!

 

[SkidRoe]

I have used a place in the UK for obsolete engine parts called Cox & Turner Engineering. Drop Martin Turner an e-mail at martin(at)coxandturner.co.uk, or call at +44 1202 823322. He may be able to fix you up with some over-size rings.
As far as repowers go, I typically send people to the Small Engine Warehouse, but they are not listing a kit for your machine. They still may be worth a call: http://www.smallenginewarehouse.com/Repower-Old-Equipment/Repower-Bobcat/
Hope this helps - SR

 

[flyerdan]

I have used a place in the UK for obsolete engine parts called Cox & Turner Engineering. Drop Martin Turner an e-mail at martin(at)coxandturner.co.uk, or call at +44 1202 823322. He may be able to fix you up with some over-size rings.
As far as repowers go, I typically send people to the Small Engine Warehouse, but they are not listing a kit for your machine. They still may be worth a call: http://www.smallenginewarehouse.com/Repower-Old-Equipment/Repower-Bobcat/
Hope this helps - SR

The 700 series came with three engine options, the 700 and 720 have the Wisconsin air cooled V4, the 721 the Deutz, of course, and the 722 has a Ford liquid cooled.
You might find an engine from one of these, the benefit would be that the fittment problems would be solved if you could also get the mounts and u-joint fittings.

What you might also consider is figuring out what ring diameter would be needed if your cylinders were punched out to round again, find the closest size regardless of make and match the cylinders to them. Then have a couple of pistons made for them. That should cost far less than the $2100 or so that you're looking at; downside is that it would be a one-off, but should give you several thousand hours of running before it's an issue again.
I'll take a look at the Deutz section and see if it gives any cylinder measurements. And it does, this gives all the info needed for some frankenpistons.

 

[kylem1]

The 700 series came with three engine options, the 700 and 720 have the Wisconsin air cooled V4, the 721 the Deutz, of course, and the 722 has a Ford liquid cooled.
You might find an engine from one of these, the benefit would be that the fittment problems would be solved if you could also get the mounts and u-joint fittings.

What you might also consider is figuring out what ring diameter would be needed if your cylinders were punched out to round again, find the closest size regardless of make and match the cylinders to them. Then have a couple of pistons made for them. That should cost far less than the $2100 or so that you're looking at; downside is that it would be a one-off, but should give you several thousand hours of running before it's an issue again.
I'll take a look at the Deutz section and see if it gives any cylinder measurements. And it does, this gives all the info needed for some frankenpistons.

SKidroe and Flyerdan, Your time is much appreciated, thank you very much. I will certainly give the people you referenced in the UK a call. An engine machine shop local here in Columbus, OH (Fowler is their name) referred me to Diamond Pistons in Michigan, I sent the piston out yesterday and they supposedly have a 3 week turnaround time, minimum order of 4, roughly $175 per piston. I also emailed the manufacturer Nural? I believe and have not heard back. But, I'll give Cox and Turner a call tomorrow. Thanks for specifications, those are spot on with what the machine shop told me, and very good information otherwise. I'll print that out and keep it. I will keep you posted, likely going to be around Thanksgiving before the old deutz is up again, I'm looking forward to not worrying about dumping oil in it everytime I run it. Thank you!

 

[kylem1]

SKidroe and Flyerdan, Your time is much appreciated, thank you very much. I will certainly give the people you referenced in the UK a call. An engine machine shop local here in Columbus, OH (Fowler is their name) referred me to Diamond Pistons in Michigan, I sent the piston out yesterday and they supposedly have a 3 week turnaround time, minimum order of 4, roughly $175 per piston. I also emailed the manufacturer Nural? I believe and have not heard back. But, I'll give Cox and Turner a call tomorrow. Thanks for specifications, those are spot on with what the machine shop told me, and very good information otherwise. I'll print that out and keep it. I will keep you posted, likely going to be around Thanksgiving before the old deutz is up again, I'm looking forward to not worrying about dumping oil in it everytime I run it. Thank you!

Trying to piece together my old f2l411 with new/machined parts I decided, at least for the time being, to be too expensive and too much of a crap shoot. I picked this up today and will be trying to slide it into my 721. I have a photo, but boy, I couldn't figure out how to upload even after reading faqs, no big deal

 

[kylem1]

Trying to piece together my old f2l411 with new/machined parts I decided, at least for the time being, to be too expensive and too much of a crap shoot. I picked this up today and will be trying to slide it into my 721. I have a photo, but boy, I couldn't figure out how to upload even after reading faqs, no big deal

It's a f2l511 deutz generator

 

[Tazza]

It's a f2l511 deutz generator

I had a 731 that had a "new" engine from a dynapac roller installed, it worked great. 2 cylinder Deutz, not sure if it was the same model as you have or not, it's been far too long

 

[kylem1]

I had a 731 that had a "new" engine from a dynapac roller installed, it worked great. 2 cylinder Deutz, not sure if it was the same model as you have or not, it's been far too long

I'm getting the flywheel machined to fit, should be ready to install next week.

 

[kylem1]

I'm getting the flywheel machined to fit, should be ready to install next week.

Here it is Hello, good news, the transplant is complete (minus the air filter hook up and the up piping for the exhaust). I added some photos under bobcat 721 repower, including the flywheel being machined. If anyone wants to do this job, it's not bad. The motor dimensions are nearly identical. The bolt holes for the motor mounts, the height of the pump shaft to the yoke of engine and the depth of the engine are the same. Here are a few issues I ran into. The intake and exhaust are plumbed different from the 411 to 511. I cut the exhaust outlet off, plugged it, cut a hole on the opposite end and welded on an outlet. The intake still needs some thought. Also, the exhaust hit the side wall and a piece about 2" by 18" was cut out, this is the only body modification I did. I could have did some cutting and welding with muffler itself, but decided not to mess with it. The 511 flywheel is 1/4" bigger than the 411 so about 3/16" had to be shaved off the top of the rear motor mount. Other things, the oil drain plug is in a different place (The 411 is in the middle/bottom of the engine, the 511 is near the flywheel, back right as you are facing it) I'm buying a barbed fitting and connecting that to a hose with a cap to make oil changes easier. It has more power and turns smoother than before, runs good, I'm happy with it. Here are few of the costs, the 511 cost $2250 and the machine work cost $387. The prices range a lot, I have seen them for $1500 and there is one on ebay for $6000. As far as the 411 rebuild would have looked like, I found pistons and rings for about 900 euros from an ebay seller in German. The cylinder jugs are around $1000 for both. So, the cost was about the same. I'll play with the 411 and see if I can get it running a little better this winter. The nice thing is that rebuild kits for the 511 are available and at a reasonable price. Thanks for your support.

 

[Tazza]

Here it is Hello, good news, the transplant is complete (minus the air filter hook up and the up piping for the exhaust). I added some photos under bobcat 721 repower, including the flywheel being machined. If anyone wants to do this job, it's not bad. The motor dimensions are nearly identical. The bolt holes for the motor mounts, the height of the pump shaft to the yoke of engine and the depth of the engine are the same. Here are a few issues I ran into. The intake and exhaust are plumbed different from the 411 to 511. I cut the exhaust outlet off, plugged it, cut a hole on the opposite end and welded on an outlet. The intake still needs some thought. Also, the exhaust hit the side wall and a piece about 2" by 18" was cut out, this is the only body modification I did. I could have did some cutting and welding with muffler itself, but decided not to mess with it. The 511 flywheel is 1/4" bigger than the 411 so about 3/16" had to be shaved off the top of the rear motor mount. Other things, the oil drain plug is in a different place (The 411 is in the middle/bottom of the engine, the 511 is near the flywheel, back right as you are facing it) I'm buying a barbed fitting and connecting that to a hose with a cap to make oil changes easier. It has more power and turns smoother than before, runs good, I'm happy with it. Here are few of the costs, the 511 cost $2250 and the machine work cost $387. The prices range a lot, I have seen them for $1500 and there is one on ebay for $6000. As far as the 411 rebuild would have looked like, I found pistons and rings for about 900 euros from an ebay seller in German. The cylinder jugs are around $1000 for both. So, the cost was about the same. I'll play with the 411 and see if I can get it running a little better this winter. The nice thing is that rebuild kits for the 511 are available and at a reasonable price. Thanks for your support.

Good to hear you have it mostly sorted out and the swap can be done!

 

[SkidRoe]

Good to hear you have it mostly sorted out and the swap can be done!

Nicely done!! Thanks for the update!!
Cheers - SR