FF-320 Rebuild
01-04-2010, 09:31 PM
#1
Thread Starter
My Feedback: (22)
Join Date: Sep 2003
Location: Jefferson,
MO
Posts: 655
Likes: 0
Received 0 Likes
on
0 Posts
FF-320 Rebuild
I am rebuilding a FF-320 and will do a thread is anyone is interested?
For those thst don't know the FF-320 is a flat four cylinder opposed engine manufactured by O.S. They are a beautiful engine and sound assume!
I received the engine is a basket on a trade for assembling the other one that came in the same basket. The one I assembled had a nice C&H ignition and was in very good shape overall. I was told that both of them were FF-240's and never gave it another thought until I order parts for mine. After some of the new parts I ordered did not fit I discovered it was a FT320 (lucky me). When a friend of mine found out it was a FF-320 he asked if he could buy it to put in his Balsa USA 1/3 scale cub. Since I can not even fly a rubber band model I decided I better sell it. Enough of the BS let's get to the good stuff.
The attached pictures show most of the parts for the lower end. I have polished the rods and the crank. The cases have been hot tanked in anti-freeze and brushed clean with Dawn Power Dissolver.
The crank had me concerned after removing the rods. As I said this thing was a basket case and the crank throws were pretty rusty. I polished the crank with some pretty aggressive emery then finished it with 800 and finally 1000 grit wet-dry. I plasti-gauged the crank tonight and all clearances are between .002 and .0025. I am very happy with this.
The next step is to install the cam and front main bearings. The pictures attached don't show it but the crankshaft is a 2 piece unit with a offset coupling and a sleeve that slides over the offset to hold the 2 halves together. I will post a picture of the crank before I install it.
This build will take about 2 weeks to complete if I get time to wok on it as planned.
For those thst don't know the FF-320 is a flat four cylinder opposed engine manufactured by O.S. They are a beautiful engine and sound assume!
I received the engine is a basket on a trade for assembling the other one that came in the same basket. The one I assembled had a nice C&H ignition and was in very good shape overall. I was told that both of them were FF-240's and never gave it another thought until I order parts for mine. After some of the new parts I ordered did not fit I discovered it was a FT320 (lucky me). When a friend of mine found out it was a FF-320 he asked if he could buy it to put in his Balsa USA 1/3 scale cub. Since I can not even fly a rubber band model I decided I better sell it. Enough of the BS let's get to the good stuff.
The attached pictures show most of the parts for the lower end. I have polished the rods and the crank. The cases have been hot tanked in anti-freeze and brushed clean with Dawn Power Dissolver.
The crank had me concerned after removing the rods. As I said this thing was a basket case and the crank throws were pretty rusty. I polished the crank with some pretty aggressive emery then finished it with 800 and finally 1000 grit wet-dry. I plasti-gauged the crank tonight and all clearances are between .002 and .0025. I am very happy with this.
The next step is to install the cam and front main bearings. The pictures attached don't show it but the crankshaft is a 2 piece unit with a offset coupling and a sleeve that slides over the offset to hold the 2 halves together. I will post a picture of the crank before I install it.
This build will take about 2 weeks to complete if I get time to wok on it as planned.
01-05-2010, 11:08 PM
#6
Thread Starter
My Feedback: (22)
Join Date: Sep 2003
Location: Jefferson,
MO
Posts: 655
Likes: 0
Received 0 Likes
on
0 Posts
RE: FF-320 Rebuild
Some more progress tonight.
I dropped the front main bearings in the front cover and dropped the rear cam bearing into the back cover. The front cam bearing goes into the main case and the bushing in the picture is placed on top of the front cam baearing to locate it in the appropriate position.
The cases were heated to 300 degrees and the bearings were placed in the freezer. They slid in like they were on ice!
I dropped the front main bearings in the front cover and dropped the rear cam bearing into the back cover. The front cam bearing goes into the main case and the bushing in the picture is placed on top of the front cam baearing to locate it in the appropriate position.
The cases were heated to 300 degrees and the bearings were placed in the freezer. They slid in like they were on ice!
01-05-2010, 11:17 PM
#7
Thread Starter
My Feedback: (22)
Join Date: Sep 2003
Location: Jefferson,
MO
Posts: 655
Likes: 0
Received 0 Likes
on
0 Posts
RE: FF-320 Rebuild
Pictured below is the 2 piece crankshaft and the coupler the is used to hold them in alignment. The camshaft is also pictured. Note it only has 4 lobes. Eash lobe actuates a pair of opposed cylinders.
01-06-2010, 08:21 AM
#12
Thread Starter
My Feedback: (22)
Join Date: Sep 2003
Location: Jefferson,
MO
Posts: 655
Likes: 0
Received 0 Likes
on
0 Posts
RE: FF-320 Rebuild
The sleeve just has an interference fit.
After taking another look last night I will put the rear bearing on the front crankshat half and then slide the sleeve on. I can set the crankshaft in the front bearing/cover and put this in the freezer. I will heat the case in the oven at 300 degrees and slide the assembly in from the front. I will get some pictures of the steps.
This is the 2nd Pegasus I have gotten the opportunity to rebuild! As I said earlier the other one was a FF-240. Both in pieces in the same basket.
After taking another look last night I will put the rear bearing on the front crankshat half and then slide the sleeve on. I can set the crankshaft in the front bearing/cover and put this in the freezer. I will heat the case in the oven at 300 degrees and slide the assembly in from the front. I will get some pictures of the steps.
This is the 2nd Pegasus I have gotten the opportunity to rebuild! As I said earlier the other one was a FF-240. Both in pieces in the same basket.
01-06-2010, 08:15 PM
#14
Thread Starter
My Feedback: (22)
Join Date: Sep 2003
Location: Jefferson,
MO
Posts: 655
Likes: 0
Received 0 Likes
on
0 Posts
RE: FF-320 Rebuild
Kmot,
I did not take a picture. I wish I had. I had not thought of doing the rebuild thread until after I started cleaning and polishing.
I did not take a picture. I wish I had. I had not thought of doing the rebuild thread until after I started cleaning and polishing.
01-06-2010, 08:49 PM
#15
Thread Starter
My Feedback: (22)
Join Date: Sep 2003
Location: Jefferson,
MO
Posts: 655
Likes: 0
Received 0 Likes
on
0 Posts
RE: FF-320 Rebuild
I took a few pictures of the front half of the crankshaft ready for installation.
It is ready to be slipped through the front of the case. I insalled the thrust washer and prop drive to make sure the crank is located at the poper depth after it is installed. There is not any bearing seats in the case for the main bearings. The case has a clean bore from front to back.
I will put the crank assembly in the freezer and the case in the oven. I will slip it in and put a few screws in the front cover to ensure every thing is seated properly.
It is ready to be slipped through the front of the case. I insalled the thrust washer and prop drive to make sure the crank is located at the poper depth after it is installed. There is not any bearing seats in the case for the main bearings. The case has a clean bore from front to back.
I will put the crank assembly in the freezer and the case in the oven. I will slip it in and put a few screws in the front cover to ensure every thing is seated properly.
01-06-2010, 09:23 PM
#16
Thread Starter
My Feedback: (22)
Join Date: Sep 2003
Location: Jefferson,
MO
Posts: 655
Likes: 0
Received 0 Likes
on
0 Posts
RE: FF-320 Rebuild
OK, change of plans.
The crankshaft will not go in through the front of the case. I have removed the crank from the front cover and installed the front cover on the case. I will be installing the crank from the back.
The crankshaft will not go in through the front of the case. I have removed the crank from the front cover and installed the front cover on the case. I will be installing the crank from the back.
01-06-2010, 10:46 PM
#17
Thread Starter
My Feedback: (22)
Join Date: Sep 2003
Location: Jefferson,
MO
Posts: 655
Likes: 0
Received 0 Likes
on
0 Posts
RE: FF-320 Rebuild
I assembled both crankshaft pieces and placed them in the freezer. I put the case in the oven. After 20 minutes in the freezer and the oven the crank assembly dropped rigth in.
I installed the camshaft and put the back cover on.
The thrust washer and woodruff key have been installed along with the prop drive assembly.
I will install the rods next and put the lower end asside. I have lots of cleaning and prep work to do on the pistons, cylinders and heads!
I installed the camshaft and put the back cover on.
The thrust washer and woodruff key have been installed along with the prop drive assembly.
I will install the rods next and put the lower end asside. I have lots of cleaning and prep work to do on the pistons, cylinders and heads!
02-14-2010, 07:56 PM
#20
Thread Starter
My Feedback: (22)
Join Date: Sep 2003
Location: Jefferson,
MO
Posts: 655
Likes: 0
Received 0 Likes
on
0 Posts
RE: FF-320 Rebuild
Sorry Guys,
I ran out of time to document the rest of the rebuild.
I do want to post the Connecting Rod torque figure.
8KG f CM
I got this straight from OS Japan. It is the same for the 120, 160 and 240 pegasus.
I ran out of time to document the rest of the rebuild.
I do want to post the Connecting Rod torque figure.
8KG f CM
I got this straight from OS Japan. It is the same for the 120, 160 and 240 pegasus.
11-01-2011, 06:05 AM
#25
RE: FF-320 Rebuild
Here is the Manual but there is not anything in there about setting the timing.
I remember it not being that difficult to time them. The marks are visible on the cam gear. With the rear case cover removed, you will notice a small hole in the large camshaft gear and a small dot on the crankshaft gear. These marks must be looking at each other to time the camshaft correctly.
http://www3.towerhobbies.com/cgi-bin...?&I=LXBY71&P=7
Manual http://manuals.hobbico.com/osm/ff-320-manual.pdf
I remember it not being that difficult to time them. The marks are visible on the cam gear. With the rear case cover removed, you will notice a small hole in the large camshaft gear and a small dot on the crankshaft gear. These marks must be looking at each other to time the camshaft correctly.
http://www3.towerhobbies.com/cgi-bin...?&I=LXBY71&P=7
Manual http://manuals.hobbico.com/osm/ff-320-manual.pdf