Topic: CB750A Hondamatic sharp metallic clinking and clanking

[jukku]

Sharp metallic clinking and clanking when in gear but unloaded.
Spare parts list page E-18 item 15 shaft stator (fork)
Spare parts list page E-18 item 10 shaft input (broken damper springs)
Spare parts list page E-14 item 17 regulator valve (operated by item 15)
Spare parts list page E-15 item   1 crank case (upper part)( steel pin limits the fork movement)

When the springs are broken the system is, in gear but unloaded, not in balance and the fork starts smashing the pin back and forth. Thats is the sharp metallic clinking and clanking.

Today, after more than 2 years of clinking and clanking, I opened the gear box to find out the source of the noice.
I dont know if the regulator valve completely ok. I do not think it is dameged.

Hope you have any help of the pics.

Start tomorrow to put the gearbox together and perhaps put in a 836ccm 9:1 bore kit, F2 cam shaft and K7 carbs.
If the weather is not too hot.

[jukku]

3 of 4 springs broken.

[Don R]

Are you having any luck finding parts?

[Medyo Bastos]

Springs, clutch discs and fibers are available


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[Don R]

Have you made any progress?

[Don R]

 The reason I ask is I have the bottom half of a cb750A engine. I'm considering opening it up to see what's inside or junking it.

[Medyo Bastos]

Don I have sourced the parts I posted above. I got part numbers from kmb in a post here on the board. I’m pretty sure I got the clutch parts from raybestos, the springs might have come from keith.. I will try and find out for sure who I got them from.





I am just looking for someone that can increase stall speed on the TC before anything else. I contacted Britain parts, but neither of us followed up.

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[Medyo Bastos]

keith and mike both chimed in L@@kie here->
Clutch plates for 1977 CB750A Hondamatic
 https://r.tapatalk.com/shareLink/topic?share_fid=13548&share_tid=163702&url=http%3A%2F%2Fforums%2Esohc4%2Enet%2Findex%2Ephp%3Ftopic%3D163702&share_type=t&link_source=app


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[RAFster122s]

Tapatalk link doesn't work for me...

[kmb69]

Don I have sourced the parts I posted above. I got part numbers from kmb in a post here on the board. I’m pretty sure I got the clutch parts from raybestos, the springs might have come from keith.. I will try and find out for sure who I got them from.





I am just looking for someone that can increase stall speed on the TC before anything else. I contacted Britain parts, but neither of us followed up.

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Springs came from JTMarks, RIP, off eBay. He just recently died. Not sure where he was getting them.
Pretty sure he was selling mold release springs from somewhere - not OEM Honda stuff. They worked!

Brittain's website appears to no longer be up and the last post on their FB page was June 23, 2018. Huh?
Not to mention, pictures I saw of their CB750A convertor mod looked like hammered $hit!

Need to find a new convertor expert IMHO.

[kmb69]

Tapatalk link doesn't work for me...

Try this one: http://forums.sohc4.net/index.php?topic=163702

[scottly]

Don I have sourced the parts I posted above. I got part numbers from kmb in a post here on the board. I’m pretty sure I got the clutch parts from raybestos, the springs might have come from keith.. I will try and find out for sure who I got them from.





I am just looking for someone that can increase stall speed on the TC before anything else. I contacted Britain parts, but neither of us followed up.

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Springs came from JTMarks, RIP, off eBay. He just recently died. Not sure where he was getting them.
Pretty sure he was selling mold release springs from somewhere - not OEM Honda stuff. They worked!

McMaster-Carr lists them as "die springs". Pick a flavor, plug in the length, OD, and wire width and see what they have to offer..
https://www.mcmaster.com/die-springs/

[RAFster122s]

If you have a set, then taking a set of good measurements might help any future or current cb750A owners order replacements from McMaster Carr.

[Don R]

 That is awesome. Good work and appreciation to the helpers.

[Don R]

   I was told Coan converters has some experience with the 750A's. I read that they can't change the fin angle but can increase the gap between the stator and rotor.
  Worth a call, they built the ones in my dragster, I have one that was raced for 7 years, rebuilt at 2 and then raced for the next 5. Still works but I replaced it because we were chasing points and didn't want to chance it. The one in it now has 3 seasons but short ones.

[MRieck]

   I was told Coan converters has some experience with the 750A's. I read that they can't change the fin angle but can increase the gap between the stator and rotor.
  Worth a call, they built the ones in my dragster, I have one that was raced for 7 years, rebuilt at 2 and then raced for the next 5. Still works but I replaced it because we were chasing points and didn't want to chance it. The one in it now has 3 seasons but short ones.

Yes....we've (a few people) have seen that (regarding stator fins). Personally I wasn't that impressed as the work was done by hand....it could be done on a rotary table and mill at the least.....CNC at the best. I've taken a few auto engines apart at this point and those square springs have been shattered in every engine (stock applications too). A #$%* design IMO that could have been avoided.

[scottly]

I've taken a few auto engines apart at this point and those square springs have been shattered in every engine (stock applications too). A #$%* design IMO that could have been avoided.

Where inside an auto engine have you seen those springs? I've seen them used as dampers in clutch discs, but never inside an engine?

[Medyo Bastos]

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[scottly]

I've taken a few auto engines apart at this point and those square springs have been shattered in every engine (stock applications too). A #$%* design IMO that could have been avoided.

Where inside an auto engine have you seen those springs? I've seen them used as dampers in clutch discs, but never inside an engine?

Brain fart ; I took it to mean automobile engine.

[Don R]

 I had a look at the innards from an A.  It's not nearly as intimidating as I expected. 

  It makes me wonder if it is the inspiration for the modern dual clutch transmissions. Mine was silicone'd on the covers, so someone was in there ahead of me, possibly why it was abandoned. The top end however, was very nice so the goo didn't plug the oil jets. Probably didn't work after the intrusion.

[Medyo Bastos]

   I was told Coan converters has some experience with the 750A's. I read that they can't change the fin angle but can increase the gap between the stator and rotor.
  Worth a call, they built the ones in my dragster, I have one that was raced for 7 years, rebuilt at 2 and then raced for the next 5. Still works but I replaced it because we were chasing points and didn't want to chance it. The one in it now has 3 seasons but short ones.

fyi, I contacted coan via email and they replied, but no way no how… BUT, got a second email from a fella named Todd stating:  “I actually talked to the boss and did some leveraging since I’m a motorcycle guy myself and we can look at it to see if we can do anything with it, however we cannot make a guarantee that we can change the stall until we get it here and take a look at it.”

I will be sending my tc to them, and will update this post in case anyone else is interested!


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[Don R]

 Cool, they have always treated me well. The first powerglide converter I sent in was cut open and inspected, it was a disaster inside. He shipped it back for $7 so I could see it for myself. The guy said it looked like a little bulldozer drove around inside, he was correct.
 

[Don R]

 I noticed Honda lists end plates in different thicknesses, I wonder if that is to adjust the clutch / plate stack height?  I've seen that in clutch type positraction differentials.

[kmb69]

   I was told Coan converters has some experience with the 750A's. I read that they can't change the fin angle but can increase the gap between the stator and rotor.
  Worth a call, they built the ones in my dragster, I have one that was raced for 7 years, rebuilt at 2 and then raced for the next 5. Still works but I replaced it because we were chasing points and didn't want to chance it. The one in it now has 3 seasons but short ones.

fyi, I contacted coan via email and they replied, but said no way no how… BUT, got a send email stating:  I actually talked to the boss and did some leveraging since I’m a motorcycle guy myself and we can look at it to see if we can do anything with it, however we cannot make a guarantee that we can change the stall until we get it here and take a look at it.

I will be sending my tc to them, and will update this post in case anyone else is interested!


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Definitely interested!

[Don R]

  Sorry for the thread hijack,
Just a Coan story, I asked them to build a tighter converter for our drag car and they got the specs out on what I already had. The converter guy guessed the name of my Dragster's engine builder based on where I was located and the torque/horsepower curve. The motor was built by a Super Stock guy and he said my existing converter is exactly the one he would spec for a Super Stock door car. 
 Moral of the story, the new one was too tight and didn't work as well as their first try. It would carry the front wheels 60'.

[Medyo Bastos]

***Coan Engineering UPDATE*** got a call from Todd. He said they can for sure machine and get the stall speed up on the tc I sent in! I told him there is a handful other knuckleheads looking to do the same!


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[kmb69]

***Coan Engineering UPDATE*** got a call from Todd. He said they can for sure machine and get the stall speed up on the tc I sent in! I told him there is a handful other knuckleheads looking to do the same!


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Awesome!
Many Thanks

[MRieck]

That is awesome. I wonder if they would be able to approximate the stall by how much (and how) material is removed from the stator.

[Medyo Bastos]

Just out of curiosity, what stall speed are you guys after?


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[Don R]

 I noticed a few inexpensive converters on ebay in case anyone needs adjustment. I may save my A case for a while.

[Medyo Bastos]

Looks like they can loosen up about 500 rpms without extensive machining.


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[Don R]

 That's a good number. Cam accordingly. Fill us in on the details when you get it back.

[jukku]

Hello
The third of my CB750A Tomatics started clinking and clanking. I´ll drive this summer with the "accompaniment" from the gearbox. It is a feature not a fault. ;-)
Have to find two of the gaskets that I´m missing.
The clutches tend to slip a bit when I hit the throttle, too much torque with with 836 10:25 Wisecos, K7 carbs, F2 cam advanced a bit?

[Medyo Bastos]

Clutch parts are available; they are the same as the Honda cvcc


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[newday777]

Hello
The third of my CB750A Tomatics started clinking and clanking. I´ll drive this summer with the "accompaniment" from the gearbox. It is a feature not a fault. ;-)
Have to find two of the gaskets that I´m missing.
The clutches tend to slip a bit when I hit the throttle, too much torque with with 836 10:25 Wisecos, K7 carbs, F2 cam advanced a bit?

The 836 shouldn't be the slipping problem as there have been many of the automatic 750s drag raced.

Exactly what oil do you have in it?

[jukku]

Gulf single 40 used in classic cars.
Temperature is now about 30 degrees celsius.

[jukku]

The source of the CB750A Hondamatic sharp metallic clinking and clanking
http://forums.sohc4.net/index.php?action=dlattach;topic=99952.0;attach=411532
Page -6-
Fig. 5
Stopper Pin and Regulator Valve Drive Arm acts as "anvil and hammer".
It is not a fault, but a characteristic. ;-)

[TdLpps]

Great document.  Thanks for attaching to the thread.