Topic: crank cases

[kew]

Hello all,
I race a 750 and I have collected lots of used parts so I thought I'd sort them over the holiday.
I have some crank cases but I don't know if they are matched pairs.
I can't see any casting marks that look the same.
Is there something I should be looking for?

[jack58]

should be a number on the back of both cases if you have any real low numbers or any sandcast cases or parts id like to get in line thanks jack

[kew]

Hello Jack, thank's for the reply.
I was told that there should be numbers on the flat part on the back of the cases but I can't find any.
I'll have another look tomorrow in the daylight.
All my cases are late numbers, I obviously need lots of spares as I race a sidecar. 

[754]

Are you thinking they may have got mixed up.
One thing that may help sort them is wider output bearing, on cases after 76 and again at 77.
 The other thing, the main bearing codes are marked under front motormount shelf on top case, these marks should correspond with the shells in the lower case.... I think you can determine what shell it is by the number markings.
 Any pics of the sidecar or details on the motors you run?

[kew]

Yes I think some of the cases may be mixed.
I have some K and some F cases, the F cases with the wider casting for the output bearing are not mixed but I think the K ones maybe mixed.
They also don't have shells in them but I don't think they would tell me anything because the numbers on shells are a bit random to say the least.
I'm starting to pull my hair out and I haven't got much left anyway.
I raced an 836cc engine last season and finished 5th in the Camathius cup championship which is a European classic sidecar championship, I'm building a 1000cc engine for next season.

[tony sawyer]

hello mate if you get stuck i can probaly sort a set i
you might need to erode a stud
short of any battle scratches and scar that pass through both halfs
. they seem to shot up in price for no reason
how many sets you got mixed up

[kew]

Hello Tony, how are you mate?
I only have 2 sets that may be mixed and I do have some others so I'm OK but it's so bloody annoying because they are really good looking cases.
Have you got yourself a passenger yet for next season?

[bear]

Off topic I know but............

I note you blokes seem to be thinking of "going large" to take advantage of your new regs.

Can I suggest that you focus on your drive line.

The clutch aside,  I belive that you will need to upgrade both your cush drive and gear sets if you want to achieve an acceptable level of reliability.

Tony I know that you have souced aftermarket rubbers for your cush drive but I believe they are rated at around 75 duro, thats only marginly stronger than the std units unfortunately.

Cheers,
Brian

[Medyo Bastos]

Off topic I know but............

I note you blokes seem to be thinking of "going large" to take advantage of your new regs.

Can I suggest that you focus on your drive line.

The clutch aside,  I belive that you will need to upgrade both your cush drive and gear sets if you want to achieve an acceptable level of reliability.

Tony I know that you have souced aftermarket rubbers for your cush drive but I believe they are rated at around 75 duro, thats only marginly stronger than the std units unfortunately.

Cheers,
Brian

would welding the sprocket carrier onto the hub be an option? is there a way of doing away with the inside bearing and spacer to make this happen?

[kmb69]

Off topic I know but............

I note you blokes seem to be thinking of "going large" to take advantage of your new regs.

Can I suggest that you focus on your drive line.

The clutch aside,  I belive that you will need to upgrade both your cush drive and gear sets if you want to achieve an acceptable level of reliability.

Tony I know that you have souced aftermarket rubbers for your cush drive but I believe they are rated at around 75 duro, thats only marginly stronger than the std units unfortunately.

Cheers,
Brian

would welding the sprocket carrier onto the hub be an option? is there a way of doing away with the inside bearing and spacer to make this happen?

Highly unadvisable. You need some kind of dampening to prevent "shocking" the gearteeth to fracture and eventually, if they last that long, to rip them off. 

One might be able to design and make a new clutch outer with spring dampers, like every other manufacturer does, that would allow a "solid" primary sprocket.

[bear]

would welding the sprocket carrier onto the hub be an option? is there a way of doing away with the inside bearing and spacer to make this happen?

Highly unadvisable. You need some kind of dampening to prevent "shocking" the gearteeth to fracture and eventually, if they last that long, to rip them off. 

The gear dogs are usally the weak link.

Example A

[madmtnmotors]

would welding the sprocket carrier onto the hub be an option? is there a way of doing away with the inside bearing and spacer to make this happen?

Highly unadvisable. You need some kind of dampening to prevent "shocking" the gearteeth to fracture and eventually, if they last that long, to rip them off. 

The gear dogs are usally the weak link.

Example A

I knew that was coming. I was hoping you were going to include a picture of the "four dogs" though, I can never get enough of them... 

[bear]

One might be able to design and make a new clutch outer with spring dampers, like every other manufacturer does, that would allow a "solid" primary sprocket.

That sounds like a viable option that I hadn't considered Kieth.

[bear]

would welding the sprocket carrier onto the hub be an option? is there a way of doing away with the inside bearing and spacer to make this happen?

Highly unadvisable. You need some kind of dampening to prevent "shocking" the gearteeth to fracture and eventually, if they last that long, to rip them off. 

The gear dogs are usally the weak link.

Example A

I knew that was coming. I was hoping you were going to include a picture of the "four dogs" though, I can never get enough of them... 

 

[kmb69]

would welding the sprocket carrier onto the hub be an option? is there a way of doing away with the inside bearing and spacer to make this happen?

Highly unadvisable. You need some kind of dampening to prevent "shocking" the gearteeth to fracture and eventually, if they last that long, to rip them off. 

The gear dogs are usally the weak link.

Example A

I knew that was coming. I was hoping you were going to include a picture of the "four dogs" though, I can never get enough of them... 

 

Still hoping to get my hands on one of those.....for just a day or two. 

[kmb69]

One might be able to design and make a new clutch outer with spring dampers, like every other manufacturer does, that would allow a "solid" primary sprocket.

That sounds like a viable option that I hadn't considered Kieth.

Got to think outside the box with these old girls!   

Brian, I lied to you last night. Did not have time for pictures today, but will do my best tomorrow. 

[bear]

Still hoping to get my hands on one of those.....for just a day or two. 

I apologize for my tardiness Kieth.
The motor has been on the bench gathering dust.
I will get my bum into gear when we get back from holidays.
As penance I will scrounge one of our cam sprockets and throw it in as well.

Cheers,
Brian

[madmtnmotors]

 

Nice! I hope to have a motor with enough power to make these mandatory... one of these days! 

[RAFster122s]

I guess I don't follow entirely.  Are the gears modified by replacing the 3 dogs that are cylindrical pins with the 4 dogs with the wedge shaped dogs?  Does the gear have to be heat treated to make the new dogs strong enough to lessen any wear?

Curious about the story.  If there is a thread that discusses it and shares the mod, then direct me to it rather than repeat it...

Thanks! David

[Don R]

 I wonder if you could bolt up a set and check the machining match at the outermost main bearings? There might be enough difference to spot a mismatched set, then swap them and check the result. Especially if there are only two cases mixed up.

[bear]

Kew,

I apologize for draging this thread off topic.

David,
I will start a thread to address your question.

Cheers,
Brian

[kew]

That's OK Bear, I'm interested in your gear thread anyway.
Don R, I think I have sorted it. I had main bearings as per the stamping on the top case and fitted a crank, with 1 of the bottom cases bolted up the crank would turn and with the other it would not.
Thanks for the suggestions gentlemen.

[Don R]

Good deal. I always cringe when I see guys on ebay selling half cases, rod caps and cam carriers with no caps. Your test proves they need to be matched.

[Bill/BentON Racing]

Yep, me too, ....50lbs of boost might do sumpin, I need to call Dimey , see if he's interested,  lol, we all getting a little crazy, I like 2017 already. I'm betting we see 9's on some SOHC 750's this year! But I gotta build a big NA engine first. Happy New Year,  yes Brian, please get Keith dem gears,,,you da man!,Bill

[Nose736]

You can miss match cases for cb as long as you plastigage for clearance, and keep the years close,EG  you can,t mismatch.sandcast with diecast They were line bored from the factory. Been doing it for years.

[754]

My opinion us that it could work some of the time..but not always.
 How many times have you done it with success? How was lineup for sidethrust.. That could matter.
And second trans bearings could end up too tight, and or maybe even loose... That would suck.
Pretty easy and safe to just get a matched set... Usually reasonable for 71-76 stuff.

[slikwilli420]

You can miss match cases for cb as long as you plastigage for clearance, and keep the years close,EG  you can,t mismatch.sandcast with diecast They were line bored from the factory. Been doing it for years.

This makes no sense whatsoever. If they are line bored and split up and mismatched and one half needs a different bearing shell than the other that won't work. You may Ashley need to worry about the mating surfaces on the side covers not matching.

[754]

Yeah and the side clearance of the rod.
 There is good engine building and not so good, guess which one takes no shortcuts...?