Topic: Oil Pressure + Easier Shifting HOW TO / WALKTHROUGH

[72hondacb750]

So I wanted to make this walk through .. this is based on advice that I was given by Hondaman but I couldn't find a walkthrough for it anywhere and stumbled my way through it. Thought maybe I could make it easier on some other new comers. .

PROBLEM : I had low oil pressure at idle .. I also had a TERRIBLE time shifting into neutral if the bike was stopped .. this was worse as the bike would heat up. My oil pressure would go down and my shifting would get harder and harder.. ..

I did three things to resolve these issues ..
1. Drilled the clutch basket to improve oil flow across the clutch.
2. Replaced the o-rings on the oil pump which had flattened and shrunk down.
3. Replaced the o-ring on the countershaft oiler.

here's some info that I gathered while doing so..
------

The first thing I did was to drill additional oil holes in the clutch basket .. This is in Hondaman's tech articles .. found here .. http://www.sohc4.net/index.php?q=node/278

Here is a picture of it and another picture that shows the approx** pattern that I used when i drilled it.. This is just hand drawn and is only meant to be a guide.





After this was done there was a noticeable improvement in the shifting of my bike. Much less of that feeling like the bike always wanted to take off, even when the clutch was pulled in all the way.

--------------------

all the o-rings you need for the rest of the project can be found in this pack sold at harbor freight.



2. The o-rings on the oil pump..

I've heard many people talk about their oil pressure .. it seems common that most show about 10psi for every 1k of rpms  .. I too had pressure like this .. My oil pressure now holds pretty steady .. Even at low idle its still 65lbs or so... this is what I did..

- removed 4-1 exhaust ..
- removed oil pan held by 10mm bolts.
- cleaned debris from oil pan and replaced gasket , set aside.
- removed oil pump with 4 bolts that held it in place .
- ensure all the little steel sleeves for the oil passages stay in place.. In this picture the sleeves are #9 .. don't loose em .. they're loose in the pump.
- replace o-rings #14 .. 3 of them. .. they are 15mmx2.5mm ..





here is a picture of the old and new o-rings together.. It's hard to see but the new one was almost twice as thick..



After you install the new o-rings the assembly is just the reverse of what we've done already. One thing to note is that it's recommended that you prime the oil pump before you reinstall it. Do do this put it in a tub of fresh oil and spin the gear until all the air is out.

-------------------------

3. Countershaft oiler O-ring ..

This one is huge to me .. I'm sure this is the biggest reason I can NOW shift into neutral while stopped at a stop light <cheers>

To get this done I needed one o-ring from the kit purchased. I also needed a dremel and an impact screw driver .. I'm pretty sure from what I read that most people will have a hard time with the screws involved in this..

- remove shift lever.
- remove trans cover.
- Carefully remove linkage and note it's assembly ..



this is where things go bad ..

the 4 screws that hold the countershaft oiler are uh .. difficult.. I tried a large screwdriver with a crescent wrench on it, did not try this for long. Could tell immediately that was not going to work so I bought an impact screw driver. The 2nd hit of the impact properly finished the points inside the screw.. See picture.



dont panic .. thats what i told myself.

so at this point i got out the dremel and cut slots into each of the 3 mangled screws ..



I then used the wide flat head bit from the impact screw driver and gave it a couple more whacks ..

ps. this is a good time to tell you not to buy the harbor freight impact driver for $4.99 .. it sucks .. at least go to the auto part store and buy their $12.99 one or better yet sears for $39.99. The tips in the harbor freight one just fell right apart.



yay success ! !



so this is the o-ring you need to replace .. I didn't spot it at first it's sooooo small .. mine was flat as hell and not sealing anything !





once you get that in there its just putting it back together and you're good to go, I used this time to also replace the seal for the shift lever as well.

Here is another diagram of that shift linage that you took out .. it was tricky to me getting it all back together .. this helped.



Hopefully this helps you to get a bike that runs better, smoother and for longer .. Enjoy.

[Terry in Australia]

That's excellent mate, I've gotta rebuild a K2 engine soon, so I'll make sure I give this a try! Cheers, Terry.

[grumpy]

Very cool.

Thanks!!

[MasterChief750]

what size oring for the countershaft oiler?

[72hondacb750]

That o-ring is 5x2.5 but either of those numbers can be .1 smaller if needed depending on whats available.

[Flying J]

Does anybody know if drilling the holes in the clutch basket works the same for a 550?

[72hondacb750]

looks like it in the parts fiche

part number 6?




question would be does it help in the same way? .. I've never had a 550 to tell ya.

[MCRider]

Thank you for the discussion and the diagram. I will be drilling my, er hub as well.

Forgive my anality, but the part to be drilled is the hub, not the basket.

The ORings I had done as part of the rebuild. But its good to know someone can change those ORings without a complete rebuild and get the smotther shifting results.

[rhodeisland_rust]

just spent the day replacing the clutch, and said 'what the heck, why not drill some holes in this beast while im at it'
i will let you guys know what kind of results i have once i get my 750k8 out on the road...hopefully soon.

[VTCBike750]

just spent the day replacing the clutch, and said 'what the heck, why not drill some holes in this beast while im at it'
i will let you guys know what kind of results i have once i get my 750k8 out on the road...hopefully soon.

Look forward to hearing about it. About tp do the same.

[HondaMan]

Great writeup, 72CB750K2!

15 x 2.5 mm and the 5 x 2.5. Thats the INSIDE diameter and thickness?

That's the size designation. Ask a seal shop for the 4.9 x 2.5 or 5.0 x 2.4 or 5.0 x 2.5, any one will fit (Honda used all 3 at one time or another). The 15 x 2.5 is the same one as found in oil filter kits, the one that fits on the oil filter bolt.

[VTCBike750]

Hondaman and 72hondacb750,

Amazing iinformation.  My bike went from shifting like a fork in a garbage disposal to as smooth as butter. 
I recommend this advice to anyone with shifting issues. 
Thanks for all the help

I also added the clutch spring seats which were missing, and feel that it maybe an added benefit.

[BottomUp]

That Harbor Freight o-ring set shown at the beginning of the oil pump walk through doesn't contain EITHER of the required sizes.  I found this out after buying this set, but I noticed that there was another o-ring set at HF...maybe it has the correct sizes.  You can see the sizes included right in the chart on the container in the pic...

[750four]

There are sets for sae and metric o rings.

BTW is there another link to the clutch hub drill mod. The link just runs you back to the home page. Just pulled my pump yesterday, the pick up screen was caked and the o rings are flatened out to. After I dropped the pump about a half qt of oil fell out too.

I also popped the 14 mm bolt off and cleaned up the internals there, then the 2 10 mm bolts on the end of e scavenge side. Cleaned up the shaft, spring, and also found that o ring. Might aswell replace it too. The shaft neededa lil tlc. Itwas a bit sticky, but smoothed out with some fine steel wool.

My pump gear has side to side play. About a 1/4". Not in turning, but in and out. Is that normal?

[chewbacca5000]

The drawing makes sense if you download it to your desktop open it in picture viewer and rotate 90 degrees.  you could also print it out.

[Pecantree]

I'm still learning this stuff. But, I thought you couldn't use regular nitrile o-rings inside the engine. That there is a special hi-temp nitrile that goes to 300deg and then viton takes you to 400deg. What's the consensus on this?

[chewbacca5000]

If your worried about it just go with Gennie Honda parts.  The good news is that these O-rings are used in a bizillion other Honda engines.  I ordered a couple sets from Boats.net for around $17 delivered.

Honda O-RING,15X2.5 Part Number: 91301-MY9-003
Honda O-RING (4.9X2.5) Part Number: 91301-426-010

The key is to do an internet search with Honda and part no.

[Dimitri13]

Does anybody know if drilling the holes in the clutch basket works the same for a 550?

I'd like to bump this thread with this question

[trueblue]

Does anybody know if drilling the holes in the clutch basket works the same for a 550?

I'd like to bump this thread with this question

I would also like to know if this works for a 650?

[1974cb550k]

To simplify things you can change the o ring without removing the cover completly. Just remove the bolts and slide the cover forward, snake the old one and replace it.

[goon 1492]

This is awesome. This winter I am going to attack my cb and do this! Good readup and thanks for the info!

[PeWe]

So I wanted to make this walk through .. this is based on advice that I was given by Hondaman but I couldn't find a walkthrough for it anywhere and stumbled my way through it. Thought maybe I could make it easier on some other new comers. .

PROBLEM : I had low oil pressure at idle .. I also had a TERRIBLE time shifting into neutral if the bike was stopped .. this was worse as the bike would heat up. My oil pressure would go down and my shifting would get harder and harder.. ..

I did three things to resolve these issues ..
1. Drilled the clutch basket to improve oil flow across the clutch.
2. Replaced the o-rings on the oil pump which had flattened and shrunk down.
3. Replaced the o-ring on the countershaft oiler.

here's some info that I gathered while doing so..
------

The first thing I did was to drill additional oil holes in the clutch basket .. This is in Hondaman's tech articles .. found here .. http://www.sohc4.net/index.php?q=node/278

Here is a picture of it and another picture that shows the approx** pattern that I used when i drilled it.. This is just hand drawn and is only meant to be a guide.




#
#
#

I do not have the same hole pattern. If I drill the holes according to the drawing, I might make the clutch construction weaker?
I have the 3 holes 2+1, either drilled in positive flank or negative.  [Positive, negative, positive, negative] The holes have the same place compared with the inner 'wings'. I'm sure that it's important to drill correct and not make the construction weaker. I understand that the holes must be drilled closer to the double set to ensure more oil at this position.

So where to drill, other side of the 'wings'? So holes will be on each side?

[VTCBike750]

here ya go PeWe

This is what I did:

But the good news is I dropped the pan and oil pump, and changed out the oil pump o-rings without a problem.

The big victory was removing the 4 screws that hold on the countershaft oiler. Quality impact driver and a dremel tool! Thought for a second that I was gonna strip everything though.


Im gonna get new screws though before I finish things. 

I also had a chance to modify the clutch




This is what I came up with.  I added a total of 8 holes.


Just a little countersunk

[PeWe]

Thank you very much for the clarification and encouragement of how to do. I'll drill some extra holes...

[chewbacca5000]

So I tried this mod today on my 1973 CB750 which was having oil pressure around 15 to 20 PSI at idle and after adding 8 additional holes, two per section it spins the dial past 70 at idle.  Shifting is much improved.  I love this mod.