Topic: Triple Tree Help new bearings -Solved

[Stev-o]

Cal - have you installed a frame kit in a 750?  I bought a couple years back, but have been reluctant to cut the frame on my K4 - concerned it might compromise the rigidity of the frame when hitting the twisties at high speeds.

[briancwynn]

I'm not sure if this is a value add assuming I take care of things before I put the engine back in? If done correctly I guess I might need a head gasket change in the future, will that make it that much easier to remove? Am I missing something?

[70CB750]

Head gasket on lot of vehicles can be replaced with the engine still in.  If this kit allows you to do it, it depends if there is enough room to take the head off.

Edit:  looks like yes, the head can be removed with the engine in.  Here, for instance:

http://www.cb750cafe.com/products-page/body-parts-and-accessories/frame-adapter-kit/

[briancwynn]

Calj would you do it with any bike that you restore?  Unless you were doing a factory rebuild of course.

[70CB750]

I would not do it.  In my opinion it compromises rigidity of the frame, no matter what kit makers say.

I would have to see structural analysis of the frame before and after; I can not imagine Honda would design a frame without it.  The kit maker just cuts it to make space without any calculations, there is nothing anywhere published that compares the rigidity before and after - and I may be biased, but I trust Honda more.

The only way to decide what is stronger is FEA for a complex structure like this. Would love to see that even if it proofed me wrong 

[seanbarney41]

I would not do it.  In my opinion it compromises rigidity of the frame, no matter what kit makers say.

I would have to see structural analysis of the frame before and after; I can not imagine Honda would design a frame without it.  The kit maker just cuts it to make space without any calculations, there is nothing anywhere published that compares the rigidity before and after - and I may be biased, but I trust Honda more.

The only way to decide what is stronger is FEA for a complex structure like this. Would love to see that even if it proofed me wrong 

+1, the cb750's frame rigidity is marginal and barely adequate imo and those braces are very important for keeping the head stable and rigid.  Why spend money on a frame kit to make an already not that great frame likely worse?, even if it's only slightly worse.  After you have done it a couple times, pulling and replacing the engine is not that big of a deal. 

[70CB750]

Words are just that, words.

In engineering, elements are calculated and verified by testing.   Unless proved by calculation that diy frame kit is as strong as original, I chose to call it BS.

[briancwynn]

So how about those Ravens?  Thanks all for the choice points.   

[70CB750]

Words are just that, words.

In engineering, elements are calculated and verified by testing.   Unless proved by calculation that diy frame kit is as strong as original, I chose to call it BS.

And you offer: words. Excellent retort.

I'll happily review any FEA analysis you provide of your '70/750 proving (being the engineer you claim) that it's structurally dependent on these tubes.

LOL, like you would understand it 

[Stev-o]

So how about those Ravens? 

They looked good but the Steelers were flat.  And I'm sick of hearing about Rice!

[briancwynn]

Good luck with it, Brian! Get jammed up, give me a holler. I'm close by and happy to pop down and lend a hand.

Calj - thank you for that and it is much appreciated. Its not a quick trip down here to the burg but I will for sure reach out to you if I get stuck... I am great at taking things apart.  We will see when I put everything back together. 

[briancwynn]

Good luck with it, Brian! Get jammed up, give me a holler. I'm close by and happy to pop down and lend a hand.

Calj I'm back on the build. I need to buy the engine motor mount bolts. We're you able to fabricate these?  How you doing?

[briancwynn]

I need to confirm. It's the longest and thickest of the bolts. I believe it's the lower. I will check.

[briancwynn]

Calj it is the lower. Does the lower come in two sizes?

[briancwynn]

I took off the Swing arm and now how do I take out the inside bearing?  1978 cb750 k2


 

[Restoration Fan]

Make yourself one of these:


Find yourself something round that is the same diameter as the little lip on the inside of the tunnel.  In my case, it was a valve shim but a thick washer would work as long as the little hole in the middle isn't very large. Then, take your grinding wheel and grind 2 opposite sides of the round piece so that they're flat like shown in the photo.

Now, you just take the new shim tool and push it up inside behind the bushing...up onto the top of the bushing.  The flattened sides let it go past the bushings but the still rounded edges will let it catch the lip when you flatten it out inside the tunnel (I used a magnet and gravity).  Now that you have a "solid" surface sitting on top of the bushing, take a piece of pipe or something and insert from the top down onto the new tool and smack it a couple of times with a hammer. 

Bill Benton taught me to make this and gave me the valve shim and it turned out to be one of the most useful tools in my tool box.

[briancwynn]

Thanks all!  I got the rod out and working on the bushings.