Topic: Engine upgrades?

[napoleonb]

Hi Gents,

I'm starting to rebuild an engine and am contemplating which mods I would like done for it. Its going to be a dedicated track-bike for street-circuits.
I already have Keihin smoothbore CR31's, a CR750 generator and F2 head on a K6 bottom end. Currently I'm tackling all the pro en cons of every part (also keeping costs in mind)
Perhaps I'm going to run my NOS CR750 cylinder block with slipper ring pistons (pistons are still lacking) and upgraded tensioner if I can make/buy the remaining items.

I was just wondering that the CR750 kit bikes used regular clutch plates and friction disks as there is no mention of special plates.
Some other Honda racers had the option of aluminium clutch plates, they wear out quicker off course but that's no biggie imo.
I've also heard that medium blasting standard steel plates will increase friction.
Putting in stiffer springs or an extra plate are more discussed but what about the plates, is it worth making aluminium clutch plates?
Besides friction the benefit of less rotating mass comes to mind as an added bonus.

[bwaller]

I can't see how aluminum plates would ever last, especially if it's raced. I far prefer an extra plate and stock springs for a better feel & easier pull. Springs need to be changed every 3 years.

I have tried bead blasting plates and of course slippage is reduced, but that is the problem. A clutch needs to be slipped some at high RPM to launch well and these made the clutch too grabby and very difficult to get a good start.

Maybe for a street bike if the clutch is engaged at lower revs they could be ok.

[turboguzzi]

are you sure about the ally plates kits for other hondas? space wise you maintain same plate thickness to fit the pack in the basket, so that means that the crushing stress where the engaging teeth meet the hub remains same but you have much weaker material to carry it. but what do i know....? would be nice to see a link to those ally plate kits....
sand blasting sounds good but essentially you are turning the steel plate surface into fine sand paper so yes, friction will increase but also the amount of clutch material dust inside the engine oil. 
if you are so worried about getting clutch slip I would simply increase spring force up to what is reasonable to handle at the lever and if that's not enough, then look into fitting an extra plate in the basket through some smart machining...


 

[napoleonb]

Here's a Honda list which replaces the standard clutch items with different kit parts, aluminium for both the friction and regular plate.
The friction plates have an aluminum core which the regular plates didn't have.
I recon this was mostly done to save weight, as stiffer springs or an added plate would have created enough friction.

[napoleonb]

I'm not really after more friction by the way, this can be done by adding a plate, stiffer springs or just by adding a washer.
Stiffer springs however makes working the lever a bit harder so I'll rather add a plate for the same effect.
Perhaps installing medium blasted and then anodized aluminium plates is the way to go.
Its saving weight, is still relative hard thus limits wear and keeps galling between both aluminium plates and clutch parts to a minimum.
Haven't read about it though...

[gschuld]

The most common ones I have seen are called Hyperplates.  More common in newer bikes but I’ve seen the Hyperplates offered for 70s Kawasaki 4 strokes at least.  I imagine there is a very hard anodized coating on them to deal with the friction and wear.  The one photo below shows the clutch pack weight is cut in half.  It won’t be like removing the charging rotor off the crank or anything, but there is less rotating mass for sure.  No clue how it would hold up in our bikes though.

George

[turboguzzi]

well, learnt something new today.... never heard about these before.
assuming they exist for a cb750, then -400 grams for 100 $ (from what i've seen) is sort of reasonable i guess.
shouldnt be that hard to DIY them with water jet cutting.

[napoleonb]

To my understanding the more modern factory Honda CR dirt bikes also use aluminium clutch plates.
This makes sense since every 60 hours or so you have to replace a lot of components anyways so excessive wear and debris from the plates woudn't make that much of a difference.
 

[gschuld]

Yup, standard from the factory.

George

[bear]

You want to now about the best clutch set up for a road racer?
You nead to ask a sidecar road racer.
And the answer is easy.

It 's just like a cake recipe.

OEM fibers, OEM or after market steals, after market springs ( replaced springs after 50 hours track time religiously).
Adjust clutch cable and actuator free play at the clutch after every race.
Measure the clutch stack after every race meeting and replace when it gets close to serviceable limits. ( do not measure indervidule plates)
Sand steals on glass or machine surface after every race meeting
This recipe works.

Resist the temptation to get funky.
If you get funky with your clutch recipe it will bit you on the ass.

I know, I have a lot of teeth marks.

Cheers,
Brian

[MRieck]

The most common ones I have seen are called Hyperplates.  More common in newer bikes but I’ve seen the Hypeeplatrs offered for 70s Kawasaki 4 strokes at least.  I imagine there is a very hard anodized coating on them to deal with the friction and wear.  The one photo below shows the clutch pack weight is cut in half.  It won’t be like removing the charging rotor off the crank or anything, but there is less rotating mass for sure.  No clue how it would hold up in our bikes though.

George

I installed those aluminum plates in my Hayabusa years ago and they did not work well. More to do with the stack height. Installed a set in my friends CBR 929 and they have worked very well for about 10 years of street riding. I believe they are also cyro aged.

[turboguzzi]

not to discourage innovation in sohc4, but i'm aligned with Brian on OEM...
through my work on the 750 kawasaki motors, got in touch with the crazy Gpz750 turbo community, essentially the same engine but with power passing trough it tripled, something in the region of 200 hp or thereabouts , and in particular with a certain Mr. Lorcan (google him up, multiple records holder), he told me specifically that he uses only stock OEM steel plates & fibers...

[gschuld]

You want to now about the best clutch set up for a road racer?
You nead to ask a sidecar road racer.
And the answer is easy.

It 's just like a cake recipe.

OEM fibers, OEM or after market steals, after market springs ( replaced springs after 50 hours track time religiously).
Adjust clutch cable freeplay at the clutch after every race.
Measure the clutch stack after every race and replace when it gets close to serviceable limits. ( do not measure indervidule plates)
Sand steals on glass or machine surface after every race.
This recipe works.

Resist the temptation to get funky.
If you get funky with your clutch recipe it will bit you on the ass.

I know, I have a lot of teeth marks.

Cheers,
Brian

Brian, I was hoping you would voice an opinion on this😁.  Most experienced racers are strong supporters of genuine OEM fibers, usually steels too along with stronger springs like Barnett springs, etc. 

Your mention of sanding the steels after each race.  I assume you meant every race weekend?  Doing it after every heat would be pretty hardcore😳.  I’m curious what grip paper you go with on the steels.  180 grit?  Finer?

Mike, I read up on a few discussions regarding the Hyperplates and other aluminum “Steels”.  The main complaint has been regarding a slightly off stack height at times but those who didn’t have that problem seemed to be generally pleased with the performance and wear.  The typical mention is they can feel the lighter rotating mass, but not by a lot.

I have heard mention of “cryo aged” as well along with special coatings (specialized anodizing I’d suspect)

George

[napoleonb]

I've never heard of sanding the discs, please do elaborate Brian.
Cryo treating is also done on chains improving live because of moleculair rearrangement, suppose it makes sense on clutch plates as well.

[bear]

Brian, I was hoping you would voice an opinion on this😁.  Most experienced racers are strong supporters of genuine OEM fibers, usually steels too along with stronger springs like Barnett springs, etc. 

Your mention of sanding the steels after each race.  I assume you meant every race weekend?  Doing it after every heat would be pretty hardcore😳.  I’m curious what grip paper you go with on the steels.  180 grit?  Finer?

George

[/quote]

Sorry George, right I meant "race meeting".
I've amended my original post to make more sense.
And yes usually I use 180 carbide.

Cheers,
Brian

[napoleonb]

When we're still on this subject, how do you guys feel about the Hondaman clutch oil holes used for racing bikes?
http://forums.sohc4.net/index.php?topic=7401.0 (reply 7)

What I will be doing is replacing the rubbers and bearings, do any of you experience with those guys?
http://honda60-70s.net/Pieces/23110-300-030_GB/23110-300-030_gb.html

[bear]

I've never heard of sanding the discs, please do elaborate Brian.

Discs can glaze up, blue or sometimes develop small high spots.
On many occasions (unlike warped plates)this does not render the plate unservisable, but it does affect the performance and action of the clutch itself.
Placing the steal's on a sheet of carbide paper attached to a flat surface and sanding them can bring them back and help provide a consistent clutch action.

A road racer not only requires a strong clutch, a good consistent feel makes all the difference at the start line as well.

Another tip while I'm at it.
If like me you carry a complete spare clutch in your spares kit.
Make sure you run it in on the bike for few laps, disassemble and clean, reassemble in the same sequence then place it in a container of new oil (same as you run in the bike) over night or longer.

Wrap it in cling wrap before storing it away.
Running a green clutch in a race bike is just asking for trouble.

Regarding cush drive rubbers, it might pay to contact kmb69.

That will probably result in a salty message arriving in my personal message box at some stage but what hell I'm sure he's just sitting around waiting for something to do. 

Cheers,
Brian

[bear]

Opps sorry, thought you where in North America. 
The French kit should be fine if the bike is under 85RWHP.
If you do use their kit I suggest you pin punch the edge of all the countersunk machine screws.

Cheers,
Brian

[gschuld]

Excellent and thoughtful posts, thx Brian. 

George

[napoleonb]

Thanks for the answers!

How do you feel about these oil holes and "sipes" as per Hondaman's advise?

[PeWe]

The clutch rubbers can be replaced in Germany. I sent them my hub they replaced the rubbers in, riveted together. I let them replace the needle bearings too when they had the hub.
http://www.fourever-classic-parts.de/index.php?option=com_content&view=article&id=26&Itemid=31

I do not know how it withstand racing. They also offer engine tuning up to 93 rwhp so the clutch might match that.
http://www.fourever-classic-parts.de/index.php?option=com_content&view=article&id=6&Itemid=17

The Hondaman clutch hub additional oil mod might cause slip in stronger engines?
I had no issue with 836 +80 rwhp street use but frequent use of the throttle.
I removed it when I got clutch slip with 1000cc wich give much more torque from low. Installed stock clutch without the mod, lightly sand blastered steels, EBC fibers, Barnett CB550 springs + washers under. Still streetbike.

I started a thread about clutch and avoid slip. Washers at last page. I think the early K0 clutches had those washers. I got mine washers with a clutch kit in the 80's.
http://forums.sohc4.net/index.php/topic,165531.0.html

[754]

 Pretty sure wecwere selling aluminum Barnett friction discs in the eighties.

[napoleonb]

I'm still collecting parts and info before putting the engine together.
I've got some primary drives, clutch baskets and will use the best of those for refurbishment. Following the tips above I will get new OEM clutch plates, springs etc.
We just got a 2.5D waterjet at work so I might cut some alu clutchplates in downtime for giggles and comparison later on.
When I've got the clutch parts redone I was thinking of getting them balanced.

Now I would like some input on the next parts I'm looking at:
The final drive had some versions over the years.
23520-300-020 SHAFT, final driven weighs 396.2 gram (early style hollow axle with chain oiler)
23520-300-030 SHAFT, final driven weighs 462.6 gram (later K version)
I was thinking of using the older type shaft and blocking of the end with a custom machined and staked alu plug to save on rotating mass.

Which bearing do you guys recommend?
91007-300-008 BEARING, ball, special 6305
91008-300-008 BEARING, ball, special 5206
both are listed for these shafts, whereas the first is for a 25mm ID 62mm OD and the thickness is 17mm (which doesn't fit my shaft)
The latter is 30mm ID which fits my shaft but the thickness is 23.8mm, comparable you can buy a 6206 bearing which is 16mm thick but otherwise fits.
Perhaps I have to come up with some special washer for this bearing as well, but that's no problem for me.

Longevity aside a smaller single bearing should reduce drag and alignment issues if I've understood correctly.
Is it worth the hassle?

Here is a link to a page on which I've put some of my CAD models where the later version solid shaft with double row bearing is posted.
https://grabcad.com/library/honda-cr750-cb750r-final-driven-shaft-1

[kmb69]

.....
Here is a link to a page on which I've put some of my CAD models where the later version solid shaft with double row bearing is posted.
https://grabcad.com/library/honda-cr750-cb750r-final-driven-shaft-1

I had not made the connection till now. I have downloaded several of your models from GrabCad. VERY nice work!

[napoleonb]

Thanks, as you can tell I model the parts in 3D and conceive of methods of making them better suited for racing.
I do take some shortcuts considering the evolute gears and other "minor" things which aren't relevant for my models at the time.
(I weigh them on a scale and when I give the model its correct material the physical calculations should give me the same weight as a confirmation for its dimensional accuracy)
It's a painstaking proces but really fun to do, as I'm a teacher in mechanical engineering its also a way to keep my skills up to par.