Crankshaft disassembly

[rpr851r]

Steve,
I have done a bit of searching on the forum to see what other people have done and I see that some people have had success with leaving the crank at a local machine shop but the shops local to me will not touch the job without having the rods removed first. I have also heard of people reaming them to size but my experience with reaming holes is that I can’t count on them to make the hole round if it is egg shaped to begin.

On a junk crank I attempted to hone the small ends of the rod with a Sunnen honing machine without removing the rods from the crank. While I was successful in getting to size there was too much bellmouth in the bore to call it a success. While I am not an experienced Sunnen hone operator, it seems all but impossible to hold the crank and guide the rod on the honing mandrel without everything getting out of alignment and causing issues with bore shape. My next attempt at resizing the holes will be using a mill and boring the rod ends. I think with very careful setup I can get a nice straight and round hole that I could run a ball hone through to get the surface finish I am after without removing appreciable material.

Good luck,
Rich

[conbs]

Shop manual says repair limit for "parallel distortion" on the big end is .01 mm. In that range my sense of feel is probably pretty worthless.

[e3steve]

Thanks for the comments so far, guys.

Bill, I dial-gauged both 'rods movement this pm: 0.03mm (both identical). I don't know if 'lengthwise movement at BDC' translates as 'parallel distortion'.

I'm going to use the spare crank as-is. My rationale here is that, after sliding my std pins into the small ends, there is just the minutest degree of parallel play (in the 'old' crank's rods there is appreciable movement -- one more so than the other), and diagonal play is pretty much identical in both horizontal and vertical planes. I measured the pins and they are a perfect 15mm tube -- no wear whatsoever, anywhere. I also measured the IDs of the small ends' eyes: both 15.005mm, and both identical in horizontal and vertical IDs, so no ovalling whatsoever. GTG!

I don't know why I didn't do that in the first instance. Doh!

[jerry]

Well guys, You asked about pulling cranks apart and putting them together again. That is one issue. Now we are entering into areas of what is OK and what can one get away with. This is an area I do not want to enter into as it is frought with danger. I personally will only do cranks if everything is pulled apart as I have seen TOO MANY nasty surprises. The other issue is that the sludge build up in the grooves that feed the big ends have always been very similar to the centrifugal oil filters that have not been cleaned for a while. When I do my work I put my reputation with it and as you can imagine I do NOT want to damage that. I have control of all of this when I do the work myself and make the judgement calls. If any of you decide to rebuild cranks and I think you should. USE the specs that HONDA supplies. Conrod little ends I bore and hone on the mill otherwise you end up with a hand job. :-). All the best Jerry

[conbs]

Jerry,
Thanks so much for the last post.

The oil runners inside the crank acting just like the oil slinger is a no-brainer when you mention it, but it hadn't even crossed my mind. As you mentioned you require them to be apart before you work on them, so you may not have dealt with it. But, if anyone else has a good idea about the best way to clean all that accumulated, centrifugally compressed crud out of the oil runners in the crank, I would appreciate your thoughts. I am only changing the rotor end and want to avoid issues with needing a jig with complete disassebly. Sure hope I can get that muck cleaned out.

Also Jerry, you said only 30% of the parts are reusable. Certainly hoping not to hear that, but if that is true, can you elaborate a little on what issues you have found, particularly with respect to the "moisture" problems. It will be a big help to us virgins who are hoping against hope that we can actually refurbish a crank and make it a little better and avoid just compounding our problems.

Indeed, disassembling a Dream crank continues to be a big adventure. I was building a jig like Graham's for pressing the crank apart last night and ran out of acetylene. DOH! I was cutting some really thick plate steel to go under the counterweight and wrap around the con rod. Would have been really great except it turned out to be 5/8" think. Goes in between the counter weights on the one side that I checked, but the counterweights are closer together on the other side and it wouldn't fit between them. DOH! Started cutting a piece of 7/16" plate and ran out of gas because I burned up so much cutting through the 5/8" piece. DOH! My little Victor torch could cut through the 5/8 plate, but it was grunting and groaning all the while - and burning a lot of gas.

I will try to get pictures to post. My work won't win any beauty contests, but should get the job done.

[e3steve]

Thanks for the comments so far, guys.

Bill, I dial-gauged both 'rods movement this pm: 0.03mm (both identical). I don't know if 'lengthwise movement at BDC' translates as 'parallel distortion'.

I'm going to use the spare crank as-is. My rationale here is that, after sliding my std pins into the small ends, there is just the minutest degree of parallel play (in the 'old' crank's rods there is appreciable movement -- one more so than the other), and diagonal play is pretty much identical in both horizontal and vertical planes. I measured the pins and they are a perfect 15mm tube -- no wear whatsoever, anywhere. I also measured the IDs of the small ends' eyes: both 15.005mm, and both identical in horizontal and vertical IDs, so no ovalling whatsoever. GTG!

I don't know why I didn't do that in the first instance. Doh!

I forgot to complete the 'rationale' paragraph! By my reckoning, if the small ends are within spec, then so should the big ends' needle rollers be, as the small ends are under greater stress (unless anyone can tell me different).

[jerry]

In pulling cranks apart I ALWAYS pull everything apart. As I said there are so often nasty surprises. On these cranks many of which have just lain about without turning for many years and have ended up having condensation etch away at the bearing surfaces and the needle rollers. I have seen broken cages and as said big accumulation of crud in the oil grooves and oil holes that run parallel with big end pins. There is no way that I would do a $5000.00 Yes $5000.00 race crank unless everything is right. A blow up can end up costing $20,000.00 in time and money. I would just suggest that one of you just pull a crank apart completely and then look at it all and think about what has been written. The knowledge will not be wasted and really the fun is not THAT expensive. At this point of time LM has I think got 5 CB450 cranks which will go to the 500cc CB72/77 race bike. I will be happy if I end up with enogh parts to make 2 good cranks which will end up with new rollers and new billet big end cages and CB72/77 crank centres. Please dont try to make a "Silk purse out of a Sows ear". It will come back to bite you. All the best Jerry