Topic: 1970 cb750 frame repair?

[Don R]

 I think it's the same Andrews that used to make a lot of our speed parts. Now they are into mini sprint cars and such.

[willbird]

  One more option,
https://andrewsmotorsports.mybigcommerce.com/chassis-products-tube-connectors-honda-cb750-sohc-1969-1978/

Those are exceptional. Nicest solution I’ve seen!

That is a good design from what I see, should be really strong and rigid. Having carved out a set I have not used yet I have really came to believe that the friction of a properly bolted together joint should be plenty strong. Some pull tests lifting known weights with a test set should show something. But really adding features such as the interlocking portions that he did are not costly.

Bill

Bill

[Don R]

 I snagged a lightly used bolt on kit from CycleX off of ebay. I'm guessing it might be one of Franks. I paid too much and really don't have a plan for it, but it might be the last one still loose in the wild. I was the only bidder which was good because I wasn't going any higher. $199 plus tax and shipping.

[scottly]

Don, please post a pic of the kit when you get it. BTW, Frank sold his kits for $150+shipping, and when he asked me to make them, I also sold them for that. After he passed and there was enough demand, I did another run of 14 kits, but had to increase the price to $175 as my costs had gone up. They were still cheaper than the Gordon kits, which was one of Frank's objectives in the first place.

[Don R]

 I ended up around $205 with shipping so I guess it wasn't so bad. I think the kit I got from you was finished better than this set, but they're living under a gas tank on the Rat Race in my storage unit so I can't look right now. Here's the Ebay picture.

[scottly]

That's Frank's design on the clamps. What about the two straps for the triangles? 

[Don R]

  Here is a pic with the straps. They look like the ones I made for my Gordons kit.
  I'm pleased they are Franks. I was able to get one of his rocker cover wrenches also, it hangs on the front of my toolbox.

[Stev-o]

That's Frank's design on the clamps. What about the two straps for the triangles? 

Hey Scott...any chance that you would do another run?

[scottly]

Hey Scott...any chance that you would do another run?

I don't think so, Steve. It's a lot of work, and it seems there aren't enough hours in a day lately..

[newday777]

Hey Scott...any chance that you would do another run?

I don't think so, Steve. It's a lot of work, and it seems there aren't enough hours in a day lately..

😮‍💨

[MauiK3]

+1, they look like they may be the best yet. Would they flex a little? Maybe, would need to somehow set up a test.

[Don R]

 Those clamps fit pretty snug, with the triangle also bolted back into place I have no worries. In my case, I replaced bars that had already been removed. I even sliced the top of the triangle out of an old frame and welded it back into that bike.

 Scott's clamps are so pretty it was a shame to have to put on the gas tank. I can see where the machining takes a lot of time. I'm still unsure how it's accomplished, that's why I was a pipefitter/plumber not a machinist. 

 Edit: I got them today.

[Don R]

+1, they look like they may be the best yet. Would they flex a little? Maybe, would need to somehow set up a test.

 I was thinking of how to test them, maybe clamp to a piece of 1" weld on a nut and twist with a torque wrench but I'm confident that they are snug. The ones on my 836 K1 haven't shown any sign of moving but the new motor might change that equation. We shall see.

[scottly]

+1, they look like they may be the best yet. Would they flex a little? Maybe, would need to somehow set up a test.

 I was thinking of how to test them, maybe clamp to a piece of 1" weld on a nut and twist with a torque wrench but I'm confident that they are snug. The ones on my 836 K1 haven't shown any sign of moving but the new motor might change that equation. We shall see.

Frank and I discussed whether the slots he put between the screws added to the flex, and in the end it didn't make the clamps more flexible, so I left them out. The last step on the mill is to cut the outer profile with the part clamped onto a steel post mounted to the mill table with an extra length 5/8" end-mill. After I made the post fixture I clamped it into a vice with a part clamped onto it, and tried to twist it with a 16" pipe wrench, using a spring scale to measure the torque. I don't recall how much torque it took to get the clamp to budge, but it was enough to prove the clamping force was more than sufficient.
BTW, when tightening the screws, do it evenly in steps on all 4 screws, like when torquing down a head.
I'm posting Frank's instructions for cutting the frame since so many pictures were lost.

[PeWe]

Franks frame kit has been used.
I have lost the count of all cylinder off, head off, cam changes to test a different cam.

Honda should have done this from the very beginning. Both my CB750 K2 and K6 have this improvement.

Ny K6 has very good handling for a CB750.

[bryanj]

Honda may well have had a different rame for R&D but why go to the expense for production bikes where every penny counts

[Stev-o]

Honda should have done this from the very beginning.

They did it on later models.

[Don R]

 We can see the coil space has been provided on the K frame, but they solved that issue in the CB750A Hondamatic so it becomes as simple as a couple bends and a gas tank change.
  My drag bike frame has been modified like an A but fits the stock K tank, it did sacrifice some of the coil space. That bike uses an ARD CD magneto that has a single wire coil and a CD box to find a home for.
  The A frame has a slightly longer and wider swing arm, if a guy could fit a pretty gas tank and an oil reservoir it would make a good K engined racer with top of engine access. I'm told that a 400F tank would fit.

[bryanj]

I seem to remember it was lower rails that Honda made removable

[PeWe]

I forgot to mention when top end is removed it is easy to swing out the bottom end alone.

[seanbarney41]

I still have not felt the need to use my frame kit.  I don't think there are many riders capable enough that they would ever notice any difference in handling.  Every road race 750 guy I have seen uses some sort of frame kit and none that I have talked to claimed to notice any problems caused by a frame kit installation.  You can't even ride if your top end is broke so there is that.

[Don R]

 Sorry if we hijacked your post la ca fe, but I guess we answered the best we could and had a good discussion.
  To summarize, I have welded the parts back into a K0 so you can't tell. I've used the Gordons kit and tig welded them in with that, I've used a Scott made set of bolt-ons, I bought a bike modified to remove the top end with the bars in place.
  Recently I purchased a set of 1" weld in frame splices off of ebay made for quad runner cages, and now I have a set of genuine Franks bolt on splices for no other reason than Frank made them before we lost him to an accident.
  We also found a nice set of frame splices at Andrews Performance.

[Kelly E]

I seem to remember it was lower rails that Honda made removable

Starting in 79' with the DOHC motors the right side lower frame rail is removable. In 82' with the V4 motors the left lower frame rail is removable and it carries coolant from the bottom of the radiator to the water pump.

[PeWe]

No need to take out the engine is the very good thing.
Lift valve cover, cam, head, cylinder as much as you need.
Lower frame rail off will only make an engine easier to take out and in again.