Hondaman clutch mod

[MarkCR750]

I did the hondaman clutch mod this morning, it seems to have worked well, putting it in 1st now doesn't result in the bike trying to pull forward, finding neutral from first was sometimes a bit of a faff but it now selects effortlessly , had a minor trauma when I broke the clutch lifter plate refitting it but replaced it with the one from an engine I'm stripping, it used to clonk into first but of the ten starts I just did it only clonked twice, I still have to set the adjuster properly so maybe I'll get 100% once that's done, the above was with cold oil as well, so I'd recommend it if you have gear change issues, photos below show the extra holes I drilled in the clutch hub (2 extra holes per quadrant) and countersunk all holes including the stock ones, cheers Mark.

[royhall]

Its so easy to break the clutch lifter plate on a 750, it's very hard to feel when it's down flat. Tightening the opposite bolts a little at a time by hand is the best way. Now you've broken one you can join a very large and growing club. A very interesting mod that, just wondering, how does it stop the crunch into first.

[MarkCR750]

I guess it was because the clutch was dragging before Roy , therefore the gears/selector were under load as the gear was being selected, an exaggerated scenario would be trying to put the bike into gear without using the clutch at all, I believe the extra oil flow through the clutch aids the plates to seperate , that's my take on it but I'm not a scientist 😀

[royhall]

HHMmm. That would make sense I suppose. My F2 only does the heavy crunch the first time into gear, after that the crunch is much lighter. Not sure if  Honda modified the F2 clutch or not, I put that crunch down to sticking plates.

[MarkCR750]

For those that haven't broken a lifter plate yet, here's what I wish I had done the first time!,nip up all 4 bolts, then remove one, look inside the hole with a torch to see if the plate is seated on the tower, if you see a gap of even half a millimetre remove the plate, File a slight lead on all 4 towers, put the plate back on but only nip up the bolts, remove one, check there is no gap, replace it and nip up, remove the next bolt, check there is no gap, repeat this on all 4 bolts, once you are sure the plate is touching the towers at all 4 positions torque it up, hindsight is a wonderful thing 😀

[Greebo]

Mark & Roy,

I have to say I have not had the heavy 1st gear crunch you mention,

The only quibble with my clutch is that it only grabs on set off when the clutch lever is almost all the way out, like you would notice when a clutch is on its way out or knackered, but its a new clutch & we have tried to adjust it so it grabs sooner but no joy.

I am use to a clutch that grabs when the lever is aprox' half way..

[MarkCR750]

Mine comes in quite late Greebo, it still has the old plates in it (3.4+ mil, limit 3.1 mil), not sure if it's normal?

[Greebo]

Mine comes in quite late Greebo, it still has the old plates in it (3.4+ mil, limit 3.1 mil), not sure if it's normal?

Hi Mark

Not sure about the numbers you have quoted above, its a bit too technical for me.

how is your bike running now ?

We fitted a new accelerator pump last week & renewed all the air mixture screws complete with all new springs o-rings & washers, these were not really needed but while the carbs were off I decided to do it.
The rich mixture problem I mentioned on  carb/cylinder 4 seems to have disappeared now

[MarkCR750]

Good news re the rich cylinder Greebo, maybe it was just the mixture screw, mines running well thanks, only managed a few miles this weekend due to the weather, so did a few jobs on it instead , clutch mod, re-routing cables, fitting an audible indicator warning (cos for some reason I constantly forget to switch them off on that bike despite being able to see the front ones flashing!), I'm thinking of a complete engine rebuild later in the year though cos I've booked the ferry for next years TT so it will need to be reliable (and take a bit of stick!).

[Greebo]

Good news re the rich cylinder Greebo, maybe it was just the mixture screw, mines running well thanks, only managed a few miles this weekend due to the weather, so did a few jobs on it instead , clutch mod, re-routing cables, fitting an audible indicator warning (cos for some reason I constantly forget to switch them off on that bike despite being able to see the front ones flashing!), I'm thinking of a complete engine rebuild later in the year though cos I've booked the ferry for next years TT so it will need to be reliable (and take a bit of stick!).

TT next year hey, Nice one Mark, you will think you are Mike Hailwood, but be carefull with the wrists..
I know exactly what you mean about the indicators, I constantly forget to turn them off, or if I do remember I push the switch too much & the other side are then on,  which is very dangerous..
on my other modern bikes you only have to push the button to cancel them

Hopefully see you in a few weeks at clay cross

Greebo

[MarkCR750]

I picked a few drills from my drawer of many drills and tried them in the stock holes until I found the closest, sorry I didn't take note of the size, hondaman says one eighth of an inch, but I'm guessing it's metric, so 3mm if memory serves?, I can't find the link myself now but found it before by googling "hondaman clutch mod", you have to trawl through quite a few similar threads before you find it!.

[MarkCR750]

Good news re the rich cylinder Greebo, maybe it was just the mixture screw, mines running well thanks, only managed a few miles this weekend due to the weather, so did a few jobs on it instead , clutch mod, re-routing cables, fitting an audible indicator warning (cos for some reason I constantly forget to switch them off on that bike despite being able to see the front ones flashing!), I'm thinking of a complete engine rebuild later in the year though cos I've booked the ferry for next years TT so it will need to be reliable (and take a bit of stick!).

TT next year hey, Nice one Mark, you will think you are Mike Hailwood, but be carefull with the wrists..
I know exactly what you mean about the indicators, I constantly forget to turn them off, or if I do remember I push the switch too much & the other side are then on,  which is very dangerous..
on my other modern bikes you only have to push the button to cancel them

Hopefully see you in a few weeks at clay cross

Greebo

Yes I'll be there, just remind me of the dates please Greebo , it's the 2 stroke and classic jap days I want to go to.

[Erling]

Isn't there something in Hondaman's advise on clutch modification about lengthwise groves up to the holes inside to sort of catch oil for the hole?
Should be more of an improvement than just extra holes!
I've seen somewhere lately that very early CB750 did not have these holes at all?
And I wrote to Honda in the day asking for advice on that clonking. Dated Sep.16 1969.
Still have the answer a nice Air Mail postcard telling me to contact their distributor for my area to whom they have forwarded my letter.
Where of cause I had already been having bought the CB750 there, and they knew nothing. Was the first one they sold.
Really I do not remember anything were ever done.
Erling.
P.S. About turn lights try to get used to turn it off the very moment the turning are started!

[Greebo]

Good news re the rich cylinder Greebo, maybe it was just the mixture screw, mines running well thanks, only managed a few miles this weekend due to the weather, so did a few jobs on it instead , clutch mod, re-routing cables, fitting an audible indicator warning (cos for some reason I constantly forget to switch them off on that bike despite being able to see the front ones flashing!), I'm thinking of a complete engine rebuild later in the year though cos I've booked the ferry for next years TT so it will need to be reliable (and take a bit of stick!).

TT next year hey, Nice one Mark, you will think you are Mike Hailwood, but be carefull with the wrists..
I know exactly what you mean about the indicators, I constantly forget to turn them off, or if I do remember I push the switch too much & the other side are then on,  which is very dangerous..
on my other modern bikes you only have to push the button to cancel them

Hopefully see you in a few weeks at clay cross

Greebo

Yes I'll be there, just remind me of the dates please Greebo , it's the 2 stroke and classic jap days I want to go to.

Mark...
#2stroke Sunday is the  26rd June....#
British bike Sunday on 10th July....
Custom & Modified on  24th July....
#Classic Japanese    on  7th Aug'.....#

[MarkCR750]

Thanks Greebo, fingers crossed for good weather , I've known them get rained off before now.