Topic: Going thru my tranny. Anyone interested?

[MCRider]

I'm figuring a lot of SOHC-ers won't need it. But, it will help some of them recognize when something is worn out. I'll be trying to match up the symptoms with the worn devices in pictures, just for the records. I know what's wrong now (worn shift drum, shift fork pins, bushings on 3rd gear ID, ball bearings, 2nd gear slider), based on the symptoms. But, that's only because I've had the great fun of going through so many trannys before! 

I've already decided on Phaedrus II that I would have the tranny undercut by APE. I'll ask them to check things over. Maybe I'll do some checking myself with your input.

I had a guy set me up years ago and he said he put a thicker shim in where the 2nd gear slides over to give it a bit more engagement. (Or maybe thinner? I'm not familiar...yet...with the tranny anatomy) ever heard of such a thing? If such a trick exists, probably not necessary with the undercutting?

[HondaMan]

I've generated a few extra neutrals in my 126,000+ mile tranny. So, with Joce' and Soos' very kind help, I've gathered several trannys (CB750) and am about to mic and plug through a full rebuild for mine. Is anyone interested if I make a photo-doc of it, with how-to-checkit and Honda's clearances (and wear limits)?

Most of you don't have these kind of miles yet, so your "tranny" troubles are usually clutch plate issues, instead. But, some of you might be reaching that 90K mile mark soon...might need this?

Hondaman, did you ever follow thru on this and I missed it?

Like the rest of the Hondaman Special projects, it became enrolled into "the 750 book" pix and details. I just found some more "interesting" things in the HS bike's tranny, and decided to roll the two together to show a little more broadly the scenarios that can develop. It's coming, but I've been so buried in Ignitions these last two months (very strange!) that I haven't had much time to finish the HS bottom end. It also turned out to have a bad wristpin, so I tore the whole thing down to replace the rods, too.

[HondaMan]

I'm figuring a lot of SOHC-ers won't need it. But, it will help some of them recognize when something is worn out. I'll be trying to match up the symptoms with the worn devices in pictures, just for the records. I know what's wrong now (worn shift drum, shift fork pins, bushings on 3rd gear ID, ball bearings, 2nd gear slider), based on the symptoms. But, that's only because I've had the great fun of going through so many trannys before! 

I've already decided on Phaedrus II that I would have the tranny undercut by APE. I'll ask them to check things over. Maybe I'll do some checking myself with your input.

I had a guy set me up years ago and he said he put a thicker shim in where the 2nd gear slides over to give it a bit more engagement. (Or maybe thinner? I'm not familiar...yet...with the tranny anatomy) ever heard of such a thing? If such a trick exists, probably not necessary with the undercutting?

I haven't heard of this particular trick, but as I will inside the HS bottom end this weekend, I'll take a look.

[750duo]

 
There are always more projects than time.


You just got to get through with the ones that interest you and let the other ones slide   

[martino1972]

and where do i find that 750 book?

[HondaMan]

It will probably be coming out in this Winter's edition, just after Christmas, as a 3-ring binder with prepunched chapters, so you have room for your own notes amongst the pictures. Price will depend on whether it has color or monochrome pictures: I haven't had one printed yet. It's being made as I go through this rebuild.

[Chivo73]

wow.  I really wanna get a hold of that book.  I have only the clymer and about to tear into my tranny as well.  It seems I have a broken tooth on the second gear.  So I bought a replacement motor of dubious conditon to swap out, but maybe just use for parts.  Either way, I'd love to hear how you go through it.

cheers.

[cookindaddy]

I'm on board too! Looking forward to it.
Like you suggested, I am no where near your mileage, but I am always eager to know more.
Perhaps I will learn why mine is hard to get into neutral when hot?
Thanks

[BVCB650]

My '75 750F rolled over 108,000 miles today.  It shifts smoother than ever and is still quiet.  I'll be interested to see what the inside of yours looks like.

That's really cool! What kind(s) of oil do you use? Have you had the bike since new?

I've had the bike since July 4, 1977.  I bought it with about 3,900 miles on it.  I only started keeping maintenance records on it in 1988 when I got it out storage, where it sat for 6 years while I lived in the bush in Alaska.  But I remember I used car oil, 10-40 in the winter, and 20-50 in the summer, changing every 1000 miles.  I also remember using Belray oil a time or too, as well.  My records show I used Pennzoil 1988-1990.  I was living in Soldotna at the time, and I think that's what they had at the Pay'N'Save.  Then in 1990 at 30,000 miles I started using Castrol, the records show mostly 20-50, changing every 1500 miles or so.  In 1994 at 45,000 miles, I started using Honda HP4.  I upped the change interval to 2000 miles, then 3000 miles with this oil.  In 1998 at 62,000 miles, I started using BMW dino oil, mostly 20-50.  I understand that oil is made by Spectro.  Change interval with that oil was 3000-4000 for a while, but I do it at 3000 these days.  I am still using the BMW oil, but am considering switching because the price has gotten ridiculous lately.  It is good oil, though.  I change the filter every other oil change.  I use either Honda or Fram filters, whatever I have on hand.  The bike does not use enough oil between changes to require topping off. 

The farthest I've been into the engine was to replace the seals under the cam towers in 2002 at 82,000 miles.  At that time, the cam looked good, with no scoring or pitting on the lobes.  The rocker shafts had some slight visible wear, but still serviceable.  The cam holder and caps had slight visible wear, too.  I didn't measure the clearances, just put it back together. 

I check the tappet clearances every 3,000 miles.  I haven't had to adjust a clearance since 85,000 miles when a couple of them were a thou tight.  I've always set the intake at .002 and the exhaust at .003.

This has been the most reliable motorcycle I have been acquainted with, and there's been quite a few.  It puts my BMW to shame.

Any place you can drive to in Alaska isn't the bush. We were in Perryville and Chignik Lake.

[HondaMan]

I'm on board too! Looking forward to it.
Like you suggested, I am no where near your mileage, but I am always eager to know more.
Perhaps I will learn why mine is hard to get into neutral when hot?
Thanks

There's a few things that cause this, although these bikes never were REAL easy to get into neutral when hot:
1. All it takes in the clutch is one slightly warped plate or disc. Honda says 0.007" is the warp limit, but above 0.003" the neutral can get sticky when hot. It's often just one plate.
2. Some wear and looseness might be happening on the mainshaft's ball bearings, letting the mainshaft shift slightly to one side when the clutch is pulled in. These can be replaced with better-quality ones, like SKF, to solve this one. I'll be offering a 'kit' this winter with these upscale (and pricey!)) bearings.
3. Too-light oil, or high-detergent oils like Castrol's "no sludge" car oil or Valvoline's automotive oils. Both companies make fine Motorcycle oils, a little harder to find: these have more zinc and less detergent, just what these high-rev engines need.

Which model 750 do you have? Some are better than others: the K4 and later ones have a shift drum with longer Neutral groove tip, which helped. This drum can be installed in place of the earlier ones, with good results (but slightly slower shifting, if you're a street racer type...    ).

[Bill/BentON Racing]

HondaMan,your carbs went out today.Be there Monday.657Bs?A?.Anyway looked pretty good,pulled 1&4,1 of course a little dirtier,but fairly clean,4 surprisingly clean.PM whenever.Bill

[HondaMan]

HondaMan,your carbs went out today.Be there Monday.657Bs?A?.Anyway looked pretty good,pulled 1&4,1 of course a little dirtier,but fairly clean,4 surprisingly clean.PM whenever.Bill

Thanks, Bill!

[cookindaddy]

Hondaman:
Thanks for your thoughts on getting to neutral made better.
I have a K8 on the road and currently have a lower mileage K7 engine that I am getting ready to swap into the K8 when the season ends.
I've been using Quaker State 10W40 but based on the comments on this board planned to try 20W50. The K8 has a fair bit of oil consumption (bad compression on #3 and an oil leak) so I've been tending to replace the oil with a "good quality" oil more often than going with proper (more expensive and rare) motorcycle oil.
I wasn't planning to crack the case on the K7 because I hope/believe that the internals are in good shape but I do have the head and jugs off and all the covers, cleaning, measuring and painting. This engine only has about 19,000 miles on it so probably the main shaft bearings are still in pretty good shape. I haven't actually run this engine, so I am not sure about getting into neutral or what other surprises it might hold.
I'd be interested in your bearing kit when it becomes available for when I work on the K8 eventually.

[HondaMan]

Hondaman:
Thanks for your thoughts on getting to neutral made better.
I have a K8 on the road and currently have a lower mileage K7 engine that I am getting ready to swap into the K8 when the season ends.
I've been using Quaker State 10W40 but based on the comments on this board planned to try 20W50. The K8 has a fair bit of oil consumption (bad compression on #3 and an oil leak) so I've been tending to replace the oil with a "good quality" oil more often than going with proper (more expensive and rare) motorcycle oil.
I wasn't planning to crack the case on the K7 because I hope/believe that the internals are in good shape but I do have the head and jugs off and all the covers, cleaning, measuring and painting. This engine only has about 19,000 miles on it so probably the main shaft bearings are still in pretty good shape. I haven't actually run this engine, so I am not sure about getting into neutral or what other surprises it might hold.
I'd be interested in your bearing kit when it becomes available for when I work on the K8 eventually.

I'll be posting it, probably in "For Sale" section, when they are ready.
About the oil (no, I don't want to start an oil thread... ): in engineering tests run in the 1980s, the Quaker State and Pennzoil brands were found to be the least protective in air-cooled engines. This is becuase of the type of oil they are: it's a partial paraffin-based body. This means that the oil must fully heat up before it supplies full lubrication (when the wax becomes liquid), and air-cooled engines are not evenly heated, like water-cooled engines. Over time, these oils build up waxy deposits (witness my last T-Bird, where the engine was destroyed by these deposits collecting in the oil pump screen, but that's another story...   ) in engines, and in the 750 in particular, in the oil hoses to the tank.

My 2 cents: don't use those oils on these bikes, regardless of weight. At the very least, use Valvoline or Havoline or Shell or Rotunda, just not Pennsylvania oils...or any 'motorcycle' 4-stroke oil.

[cookindaddy]

OK Hondaman.
I appreciate your logic and explanation and I will switch to one of the ones you suggest!
And we didn't even (re)start an oil thread!
Now back to your tranny....

[ron.cieri.313]

just a +1 on this...I am going into my tranny soon due to the fact i no longer have a second gear on my CB750 K.

[HondaMan]

HondaMan,your carbs went out today.Be there Monday.657Bs?A?.Anyway looked pretty good,pulled 1&4,1 of course a little dirtier,but fairly clean,4 surprisingly clean.PM whenever.Bill

I got 'em, Bill! Thanks!
Your box went out this morning (I'm tardy...).