My new ride..an old 720

[kilohertz]

So I ran it around again today, got stuck in the snow for a half hour, then went for a drive down the road. Seemed to be quite good. Only started to slow down on one of the little hills. I went back up to the house and checked the compression again, and it hasn't changed, still 25 PSI at cranking and 60 PSI when running on 3 cylinders. So now I think I will be ordering an engine gasket set and pull off at least the valve covers again and make sure the tappets are adjusted correctly, and if need be, pull off the head and see whats going on. Lap the valves and set the tappets. I have run about 1 liter of ATF/MMO and about 1 cup of water through the intake in the last few days, and it is definately better, but I want all 4 cylinders to be 90 psi at cranking speed. The vacuum gauge still flutters a little at high speed, considerably more at idle. Who knows, maybe the tappets are out of adjustment and the valves aren't closing all the way.
I'll keep you posted.
Paul

Okay, figured out how to post pics...so here are a few. I now know I need to make them smaller for this site.

 

[HarryN]

Okay, figured out how to post pics...so here are a few. I now know I need to make them smaller for this site.

Picture size is fine. No need to change it. Nice pictures too! Thanks

 

[Tazza]

Picture size is fine. No need to change it. Nice pictures too! Thanks

I agree, file size is good.
Pretty tidy looking machine too.

 

[wings5j]

I agree, file size is good.
Pretty tidy looking machine too.

Hey Paul,
Welcome aboard and thanks for the good post and pics. Should be a fun rig once you get caught up on the tlc.
John

 

[kilohertz]

Hey Paul,
Welcome aboard and thanks for the good post and pics. Should be a fun rig once you get caught up on the tlc.
John

Hello John, Dan, Tazza, Harry et al...
Thanks for the welcome and for the help with this machine. Well, this may be my final installment for this thread as it's getting quite long and I have another question re: electrical and besides that......today......da dada daaaaaa... I fixed it!!!!

I decided to get into it deeper and pull off the head on the suspect cylinder(s) and before I did that, thought I better check the valve clearances. So, here is something important to remember when troubleshooting a compression problem. No matter how much ATF/MMO or water you inject into the engine, it simply will not fix tight valves that have no hope in hell of closing as they are WAY out of adjustment. I have no idea how the exhaust valve tappet got so tight but that was it. I set it for .016" and the intake for .008" per the Wisconsin repair manual and put it all back together, without pulling the head, did a compression test and it was up to 60 PSI at crank, the others were still 90 psi, fired it up and it ran so much better. The vacuum gauge still showed some flutter...for about 30 seconds, then after the valves had a few minutes to find their happy place, seated properly and away she went. Full power, no bogging, vacumm gauge smooth as a cucumber with no signs of flutter, even at idle. I drove it down the road and cleared my neighbours driveway, then brought it back home and taught my 10 year old son how to run it and he moved some snow around the property all by himself.
I'm so happy and relieved it was so simple. I sure learned a lot on this part of the adventure. Now I can relax and go through the rest of the maintenance schedule, filter changes etc. and get ready for spring.
So, I will ask the question here, but if I should open another thread let me know....When I shut off the machine, the alternator light stays on, sometimes it flutters, sometimes it goes out, it depends on where the engine stops. I can just hit the starter and then it will go out. I have adjusted the regulator as the charge voltage was 16VDC when I got it, it's now back to 14VDC.
I am listening to your suggestions with open ears.
Cheers
Paul

 

[Tazza]

Hello John, Dan, Tazza, Harry et al...
Thanks for the welcome and for the help with this machine. Well, this may be my final installment for this thread as it's getting quite long and I have another question re: electrical and besides that......today......da dada daaaaaa... I fixed it!!!!
I decided to get into it deeper and pull off the head on the suspect cylinder(s) and before I did that, thought I better check the valve clearances. So, here is something important to remember when troubleshooting a compression problem. No matter how much ATF/MMO or water you inject into the engine, it simply will not fix tight valves that have no hope in hell of closing as they are WAY out of adjustment. I have no idea how the exhaust valve tappet got so tight but that was it. I set it for .016" and the intake for .008" per the Wisconsin repair manual and put it all back together, without pulling the head, did a compression test and it was up to 60 PSI at crank, the others were still 90 psi, fired it up and it ran so much better. The vacuum gauge still showed some flutter...for about 30 seconds, then after the valves had a few minutes to find their happy place, seated properly and away she went. Full power, no bogging, vacumm gauge smooth as a cucumber with no signs of flutter, even at idle. I drove it down the road and cleared my neighbours driveway, then brought it back home and taught my 10 year old son how to run it and he moved some snow around the property all by himself.
I'm so happy and relieved it was so simple. I sure learned a lot on this part of the adventure. Now I can relax and go through the rest of the maintenance schedule, filter changes etc. and get ready for spring.
So, I will ask the question here, but if I should open another thread let me know....When I shut off the machine, the alternator light stays on, sometimes it flutters, sometimes it goes out, it depends on where the engine stops. I can just hit the starter and then it will go out. I have adjusted the regulator as the charge voltage was 16VDC when I got it, it's now back to 14VDC.
I am listening to your suggestions with open ears.
Cheers
Paul

Here is hopeing that it will stay in top shape.
The alternator light should come on when you shut down, it shows that its not charging. When you turn the key off it should go out. Seems odd that it depends on where the engine stops, no idea why though.

 

[kilohertz]

Here is hopeing that it will stay in top shape.
The alternator light should come on when you shut down, it shows that its not charging. When you turn the key off it should go out. Seems odd that it depends on where the engine stops, no idea why though.

Yes, the light comes on when you shut down the engine by turning off the key, and it flickers as the engine slows down, but then depending on where the engine stops, the light may stay on, or go out. I don't know if someone has incorrectly rewired something behind the control panel...I guess I will have to get in there and find a wiring diagram and start troubleshooting. And like you say, not sure why it depends on where the engine stops. Maybe something to do with the alternator commutator or???
Thanks
Paul

 

[Tazza]

Yes, the light comes on when you shut down the engine by turning off the key, and it flickers as the engine slows down, but then depending on where the engine stops, the light may stay on, or go out. I don't know if someone has incorrectly rewired something behind the control panel...I guess I will have to get in there and find a wiring diagram and start troubleshooting. And like you say, not sure why it depends on where the engine stops. Maybe something to do with the alternator commutator or???
Thanks
Paul

When it is shut down, no power will be generated, so the light should be off as the key is also off. It does sound like some weird wiring, i just have no idea how it could be done so its so wrong. Other than a bad ignition switch allowing power to the alt?

 

[kilohertz]

When it is shut down, no power will be generated, so the light should be off as the key is also off. It does sound like some weird wiring, i just have no idea how it could be done so its so wrong. Other than a bad ignition switch allowing power to the alt?

Hi guys! Happy new year!
Well it's been a few years since I last updated this thread...and fixed the alt. problem. I just removed the old one and the external regulator and installed a complete GM alt from an 80's vehicle, bolted right in, is self regulated and solved all the problems. Has been running great for a few years now....however..she need some serious engine work.
It has been running fine now for 3 years, but doing regular tune up yesterday I thought I would check compression, found 3 of them down at about 30-45 psi at crank and the original problem cyl at about 10 psi at crank. This is warm and with throttle wide open. Going to check again today cold, but wow!. It seems to run fine and the original problem cyclinder plug looks like it is running fine, the right 2 cyls seem to be a little oil wet, but still okay. The engine has about 1200 hours since complete rebuild by local Bobcat dealer. It should still be running fine so maybe it's time to remove the heads and see what is going on inside. Just guessing valves but maybe head gasket..shouldn't be rings yet??
Also thinking, as I am now using this a fair bit, that maybe look into putting a deisel into it. Just thinking out loud. I'm sure it's doable and will search out some options. Would be nice to have a little more snort and torque. would the drivetrain and hydraulic system be up to an little extra power or should I be looking for a newer machine? This one has had all the drive rebuilt and and ois overall in pretty good shape, although the pins/bushings are getting worn and should be replaced.
Cheers
Paul

 

[discountufoparts]

Hi guys! Happy new year!
Well it's been a few years since I last updated this thread...and fixed the alt. problem. I just removed the old one and the external regulator and installed a complete GM alt from an 80's vehicle, bolted right in, is self regulated and solved all the problems. Has been running great for a few years now....however..she need some serious engine work.
It has been running fine now for 3 years, but doing regular tune up yesterday I thought I would check compression, found 3 of them down at about 30-45 psi at crank and the original problem cyl at about 10 psi at crank. This is warm and with throttle wide open. Going to check again today cold, but wow!. It seems to run fine and the original problem cyclinder plug looks like it is running fine, the right 2 cyls seem to be a little oil wet, but still okay. The engine has about 1200 hours since complete rebuild by local Bobcat dealer. It should still be running fine so maybe it's time to remove the heads and see what is going on inside. Just guessing valves but maybe head gasket..shouldn't be rings yet??
Also thinking, as I am now using this a fair bit, that maybe look into putting a deisel into it. Just thinking out loud. I'm sure it's doable and will search out some options. Would be nice to have a little more snort and torque. would the drivetrain and hydraulic system be up to an little extra power or should I be looking for a newer machine? This one has had all the drive rebuilt and and ois overall in pretty good shape, although the pins/bushings are getting worn and should be replaced.
Cheers
Paul

Dropping a 3 cylinder Kubota into it would be a project but definitely worth it if you can find a used one at the right price. Also replacing the the ujoint coupler with a heavy duty rubber equipment coupler at that time can save some space if yours has the ujoint system between the engine and hydrostat.
Look at equipment auctions. A D1803 would probably be good for your application. Has 38 horse in the naturally aspirated version and 115 ft/pds of torque.

 

[discountufoparts]

Dropping a 3 cylinder Kubota into it would be a project but definitely worth it if you can find a used one at the right price. Also replacing the the ujoint coupler with a heavy duty rubber equipment coupler at that time can save some space if yours has the ujoint system between the engine and hydrostat.
Look at equipment auctions. A D1803 would probably be good for your application. Has 38 horse in the naturally aspirated version and 115 ft/pds of torque.

Ebay also has a ton of Kubota engines at reasonable prices ranging from 900 bucks to 3000 for something you would want. You may even be able to get away with a D1105. That is what is stuffed into my Bobcats. They came off of Reefer units. Just depends on what the needs of your machine are.

 

[ChandlerW]

Ebay also has a ton of Kubota engines at reasonable prices ranging from 900 bucks to 3000 for something you would want. You may even be able to get away with a D1105. That is what is stuffed into my Bobcats. They came off of Reefer units. Just depends on what the needs of your machine are.

Glad to see I'm not the only one with a 700 series. Mine is a 722 with the Ford engine.

 

[kilohertz]

Ebay also has a ton of Kubota engines at reasonable prices ranging from 900 bucks to 3000 for something you would want. You may even be able to get away with a D1105. That is what is stuffed into my Bobcats. They came off of Reefer units. Just depends on what the needs of your machine are.

Hi Guys,
Thanks for the ideas. I'll keep an eye open for the diesels. In the meantime, I will start with the easy stuff, like pulling the heads and giving her a good valve job to see if that gets some life back into it. Just as soon as the snow goes, which we have had several major dumps in the last week...over 2 feet now in a week.
If a Wisconsin engine is rebuilt, and is well maitained, what should it's service life be, in hours, before one should consider a rebuild? I know it's a generic question with many variables, but just in general. I wouldn't think rings should not be an issue with only 1200 hours since overhaul.
Thanks!
Paul

 

[Tazza]

Hi Guys,
Thanks for the ideas. I'll keep an eye open for the diesels. In the meantime, I will start with the easy stuff, like pulling the heads and giving her a good valve job to see if that gets some life back into it. Just as soon as the snow goes, which we have had several major dumps in the last week...over 2 feet now in a week.
If a Wisconsin engine is rebuilt, and is well maitained, what should it's service life be, in hours, before one should consider a rebuild? I know it's a generic question with many variables, but just in general. I wouldn't think rings should not be an issue with only 1200 hours since overhaul.
Thanks!
Paul

I would have thought many times more than that, especially for the figures you have given.
Diesels generally get 6,000 hours before starting to get a little lower on compression. I was always told that they generally last twice as long as a petrol/gas engine so you should have had at least twice as many hours a you have now.
Can you do a wet test? take a pressure reading, then take a plug out and squirt in some oil then re-check the compression. If it goes up, the rings/bore is worn, if not it should be the valves.

 

[kilohertz]

I would have thought many times more than that, especially for the figures you have given.
Diesels generally get 6,000 hours before starting to get a little lower on compression. I was always told that they generally last twice as long as a petrol/gas engine so you should have had at least twice as many hours a you have now.
Can you do a wet test? take a pressure reading, then take a plug out and squirt in some oil then re-check the compression. If it goes up, the rings/bore is worn, if not it should be the valves.

Yes, I will do a wet test later today. In general, should compression tests be done on a cold engine or just after running? When I did it last week, it had just run for a few hours.
Thanks!

 

[Tazza]

Yes, I will do a wet test later today. In general, should compression tests be done on a cold engine or just after running? When I did it last week, it had just run for a few hours.
Thanks!

I thought it was meant to be done cold, about 90psi is a good figure i thought.

 

[kilohertz]

I thought it was meant to be done cold, about 90psi is a good figure i thought.

Update...I pulled the manifold and tappet covers and used my little video scope snake thing to look into the cylinder and the problem cyl. #2 looks nice a clean, no carbon, and the plug is the cleanest of them all. It looks like the cylinder is running fine, just no compression. I checked the valve clearance and found them to be tight again, almost no clearance, way less than .008" on both, so I adjusted them to spec and immediately went back to 40psi and then compared to the other cyclinders and they are all the same again...put some oil in each cylinder and they all climbed to 60 +/- 10 psi which is where I was 3 years ago. So, what the heck happened? Do valves just tighten up by themselves or is this just normal wear of the valve seat? It has 160 hours on it in the 3 years since I had the original problem. Maybe there was some carbon stuck under the valve that finally cleaned up.
So today's project is to adjust #1 and #3 cylinders and put it pack together and see what I have when it warms up. As you can see, I am dealing with a little snow and have my patio umbrella setup so I can work on it. I tried to loosen the head bolts with my electric impact gun but decided against further removal attempts...I need the machine and don't want to get into removing borken bolts from the block and the mess that goes with that.
One other thing I noted, the problem cylinder seems to have a weak exhaust valve spring, in that I can actually pull it off the tappet with some effort with my fingers..have nothing to compare it until I get the other covers off, but is this a problem or normal? It seems weaker than the intake spring. It's not broken.
I'll keep you posted.
Thanks!

 

[Tazza]

Update...I pulled the manifold and tappet covers and used my little video scope snake thing to look into the cylinder and the problem cyl. #2 looks nice a clean, no carbon, and the plug is the cleanest of them all. It looks like the cylinder is running fine, just no compression. I checked the valve clearance and found them to be tight again, almost no clearance, way less than .008" on both, so I adjusted them to spec and immediately went back to 40psi and then compared to the other cyclinders and they are all the same again...put some oil in each cylinder and they all climbed to 60 +/- 10 psi which is where I was 3 years ago. So, what the heck happened? Do valves just tighten up by themselves or is this just normal wear of the valve seat? It has 160 hours on it in the 3 years since I had the original problem. Maybe there was some carbon stuck under the valve that finally cleaned up.
So today's project is to adjust #1 and #3 cylinders and put it pack together and see what I have when it warms up. As you can see, I am dealing with a little snow and have my patio umbrella setup so I can work on it. I tried to loosen the head bolts with my electric impact gun but decided against further removal attempts...I need the machine and don't want to get into removing borken bolts from the block and the mess that goes with that.
One other thing I noted, the problem cylinder seems to have a weak exhaust valve spring, in that I can actually pull it off the tappet with some effort with my fingers..have nothing to compare it until I get the other covers off, but is this a problem or normal? It seems weaker than the intake spring. It's not broken.
I'll keep you posted.
Thanks!

I think the valve seats wear or sink allowing the valve clearance to reduce. Possibly from the exhause gas cutting as it blows past the seal of the valve and seat.

 

[kilohertz]

I think the valve seats wear or sink allowing the valve clearance to reduce. Possibly from the exhause gas cutting as it blows past the seal of the valve and seat.

Finally got at the #1 and 3 valves and found they were all tight as well. All adjusted to .008 and .016 and am making up tappet cover gaskets and will be reassembling shortly. Hopefully she'll run better after this. I now have 60 PSI in #1,3 and 4, and 50 in the original problem #2 cylinder, cranking cold. Did a leak down test on it and have some leakage on all the valves on all cylinders. I will try it again after I get it back together and warmed up.
more later...

 

[kilohertz]

Finally got at the #1 and 3 valves and found they were all tight as well. All adjusted to .008 and .016 and am making up tappet cover gaskets and will be reassembling shortly. Hopefully she'll run better after this. I now have 60 PSI in #1,3 and 4, and 50 in the original problem #2 cylinder, cranking cold. Did a leak down test on it and have some leakage on all the valves on all cylinders. I will try it again after I get it back together and warmed up.
more later...

So I cranked down the manifold this morning after the high heat RTV set overnight and fired it up. I started right away and ran way smoother. I had a vacuum gauge on the intake and as the seconds went by, the needle smoothed out and the vacuum increased, indicating the valves were seating again. Yeah! I set the idle speed and governed speed and ran it for 15 minutes. It's much better and runs great again. Going to get it off the trailer and plow the driveway and hopefully she'll be back in good working order. I checked the compression after it ran for 15 mins and #2 is still only 30 psi with the others at 60. It may come up as it runs in. I didn't want to get into a valve job at this point, broken head bolts etc. but will do it this spring when it warms up and drys out.
What I learned here, is valves can go out of adjustment and should be checked more regularly. I only have 200 hours on the machine since I bought it so maybe a tune up every 50 hours is in order.
Thanks to all who helped, much appreciated.
I think that's it for now.
Cheers