Topic: SUCCESS - 3D Print - CB650 to CB550 Primary Tensioner Project

[RickThomas]

Update:
I finally finished this project. After having a polymer test piece printed, I went forward with a metal 3D print of the part. I ordered the part from Sculpteo and had the part made via binder jetting out of 420SS/Bronze. Attached below is an image of the installed adapter (forgive my dirty engine, I store my bike outside and it sees a healthy amount of miles). For my build, I opted to not use the middle bolt in an effort to minimize case holes. I found the two end bolts to provide a secure mount. I also opted to bend the bottom of the tensioner by 90 degrees to enable the use of the stock oil pan and pickup as noted in the forum. My 3D printed part did require some grinding with the Dremel to mate with the tensioner and case properly. I assume this is likely due to slight variances in part castings. I also required some epoxy around the exterior bolt hole due to a slow oil seep. Following an hour ride and some aggressive testing, the part performed perfectly.
Prior to the install, I had excessive chain slap that resulted in a rough/noisy idle and metal flakes in the oil pan. After the install, the idle is smoother and there is no chain slap in the lower end. Overall, this was well worth the effort.

Original Post:
Prior to the whole COVID-19 issue, I was working on developing a 3D print file for an adapter to install the CB650 primary chain tensioner on the CB550. It is based on the drawings and discussions which took place on this forum: http://forums.sohc4.net/index.php?topic=80690.0
I have made a simple 3D file and was going to have it cut out of polymer to check the fit and operation. Once that checked good, I was going to seek having it cut from aluminum. Unfortunately, this has not been able to pan out in our current shutdown. The stl file and the shared diagram on from the forum are attached to this post. I was hoping somebody out there may be able to help me get this to the finish. The one change I had to make in this case is that the holes are not threaded since I wanted this file to be 3D printer compatible. If someone is able to finish this or if they already have, I'd be willing to pay for one since I am currently bored and happen to have an extra CB650 tensioner laying around.

[Sano]

Rick,
  I made the mounting adapter you show here from those same drawings using only a end mill bit on my drill press an  X-Y axis machinest vice as well as files a Drexel grinder and the appropriate size metric tap.  You might want to attempt my “stone knives and axes” fabrication method.  The hardest part was aligning the holes in the case with the tapped holes but if you give yourself a little extra length on the aluminum blank to play with (7075T-6) and establish one hole location first you can keep everything in registration.  I also had a bit of a challenge getting the 2 through-the-case bolt heads to have a nice flat landing on the not flat casting surface.  It needs to be flat to tighten up against.  A copper gasket under the bolt head was not enough to stop weeping and had to remove, clean and beef up the sealing with a small bit of Hondabond.  It’s a tight fit in there but the modification worked great with the 650 tensioner which I looked for for some time and had to pay a lot for so if you have one I would say you are a third of the way there.  I got the aluminum from an online metal supplier.  Go slow and enjoy the process and good luck.  This is a smart mod for anyone planning on putting lots of miles on the bottom end or wanting a nice tight drive train.

[Lotus54]

I am interested in doing this to 750 sei engine and understand the dimensions are the same.
   I don’t have the facilites to make the block, but I also don’t want to weld on the cases and mount that way.


Any sources for new tensioners?   I already have the needed pan and pickup.

If someone gets one machined- I would be interested in getting one also.

Mark

[RickThomas]

Update:
I finally finished this project. After having a polymer test piece printed, I went forward with a metal 3D print of the part. I ordered the part from Sculpteo and had the part made via binder jetting out of 420SS/Bronze. Attached below is an image of the installed adapter (forgive my dirty engine, I store my bike outside and it sees a healthy amount of miles). For my build, I opted to not use the middle bolt in an effort to minimize case holes. I found the two end bolts to provide a secure mount. I also opted to bend the bottom of the tensioner by 90 degrees to enable the use of the stock oil pan and pickup as noted in the forum. My 3D printed part did require some grinding with the Dremel to mate with the tensioner and case properly. I assume this is likely due to slight variances in part castings. I also required some epoxy around the exterior bolt hole due to a slow oil seep. Following an hour ride and some aggressive testing, the part performed perfectly.
Prior to the install, I had excessive chain slap that resulted in a rough/noisy idle and metal flakes in the oil pan. After the install, the idle is smoother and there is no chain slap in the lower end. Overall, this was well worth the effort.

[Deltarider]

Wow! Great project!