Author Topic: 750 K2 Strip & Rebuild - help please  (Read 5464 times)

Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #30 on: March 26, 2022, 09:26:43 PM »
Whilst I was there a couple of cranks were done Ash, the first whose balls were rather proud 🥹, and mine whose were relatively recessed. The 1st crank, well, they popped out at first strike of the cold chisel, and on mine a couple+ of strikes were necessary, with one re-TIG’ing of a blob - the outcome tho’ was never in doubt.
Be sure to have replacement balls….

Lindsay mentioned the latter grub screws, and also that on any ball-plugged cranks intended for racing he’d tend to modify them to this.

Nige, many discussions wrt Synthetic oils…. do I assume you use it in your SOHCs with no detriment to the clutch? And if so are you increasing the change times?
« Last Edit: March 26, 2022, 09:39:27 PM by Lobo »

Offline AshimotoK0

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Re: 750 K2 Strip & Rebuild - help please
« Reply #31 on: March 27, 2022, 12:50:49 PM »
You should always remove the balls when cleaning a crank. The later 750 crank has grub screws with are easier to remove  ;)
  What's your recommended method for removing the balls Graham?
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Offline Trigger

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Re: 750 K2 Strip & Rebuild - help please
« Reply #32 on: March 27, 2022, 06:49:32 PM »
You should always remove the balls when cleaning a crank. The later 750 crank has grub screws with are easier to remove  ;)
  What's your recommended method for removing the balls Graham?

Crank in a big vice, lay a penny washer over the ball, weld a rod to the ball, attach the slide hammer to the rod and pull out  ;) Never tried a chisel before.

Offline K2-K6

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Re: 750 K2 Strip & Rebuild - help please
« Reply #33 on: March 28, 2022, 09:02:33 AM »
Nige, many discussions wrt Synthetic oils…. do I assume you use it in your SOHCs with no detriment to the clutch? And if so are you increasing the change times?
yes to using it in sohc engines without clutch problem.

It's as you mention a contentious subject. Routinely I've never ever worn a clutch out on bike or car, and so may have a different view from others. Aware that routinely some riders/drivers get nothing near the clutch life I experience, so a caveat there to start with.

I've looked after bikes that the rider habitually trashed the clutch with not any input from synthetic oil.

It could be turned the other way round for arguement sake. Given the choice of assessment to see if your bike has clutch slip if you use this type of oil, a potential only, to are they willing to compromise the bearings etc from poor oil conditions, which would they rather replace ? Clutch or engine rebuild ?

Many comments about clutch slip come from completely unqualified views. There's many different influences as to how a clutch can slip, but their projection only sees "slippery" oil.
One of the determinants here is that most are completely unaware that synthetic engine oils aren't more slippery than mineral type. It's just a non informed assumption. 
The facts here are (even in your own engine) there's been lubrication failure, however that occurred, that compromised the cam in it's history. Also that it has evidence of sludging in the crank passageways.  Far from perfect in any unbiased view. These engines, with decent lubrication should easily see 100, 000 miles, in pure engineering materials terms, why many of them don't is more the question I'd ask.
As you mention Simon, it's a densely packed topic and often filled with hearsay along with little phrases used in place of good technical explanation.

Perhaps a dedicated thread worthwhile.

Offline Trigger

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Re: 750 K2 Strip & Rebuild - help please
« Reply #34 on: March 28, 2022, 09:22:53 AM »
Every customer i have had in with clutch slip problems is that they are still using the old 40 year + plates or a high grade of synthetic oil.
Having gone by the Manual and measured the thickness of the plate and it is within spec. They have not taken in to that the friction plate has gone hard over time and is just slipping due to a hard surface and always say, but it is within spec  ;) 

Offline K2-K6

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Re: 750 K2 Strip & Rebuild - help please
« Reply #35 on: March 28, 2022, 10:12:51 AM »
The collective noun used by oil manufacturers is "lubricity" in description of how slippery an oil or fuel is. Covering a multitude of properties including shear stability, absolute shear strength etc.

It's very hard to form a competent position that can clearly attribute better lubricity to synthetic oil over and above a mineral oil. In other words they don't really differ much, if at all. It's the assumption that synthetic is more slippery that undermines most arguments against using synthetic.

The properties it has that are capable of outperforming mineral are in flow characteristics/viscosity range (high VI range) oxidation stabilisation,  raised heat tolerances,  all of which are a valuable asset in this situation. 

Offline Bryanj

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Re: 750 K2 Strip & Rebuild - help please
« Reply #36 on: March 28, 2022, 11:20:22 AM »
I think one of the problems is people see synthetic but think friction modifiers which early synthetic car oils had as well and its those that cause clutch slip

Offline Oddjob

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Re: 750 K2 Strip & Rebuild - help please
« Reply #37 on: March 28, 2022, 02:36:29 PM »
Getting those ball bearings out isn't for the faint hearted I'd imagine. Much better to have a spray that can dissolve the sludge without having to resort to drilling it out. Maybe someone like Ash can get some of the typical muck left in this passage and see if he can find a fluid which readily dissolves it, brake cleaner seems to work for instance but doesn't by all accounts do it totally. Knowing Ash he'll invent some exotic cocktail that will solve the problem without having to remove the ball bearing and potentially ruin a good crank.
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Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #38 on: March 28, 2022, 10:47:02 PM »
Surely the problem Ken, is that you’re unable to directly point any spray at the column of sludge given the geography of the holes. So (useful) mechanical degreasing / washing out is off the cards. Next issue is the 6(?) mm column, 1” high (?) of compacted ‘plastercine’ - how are you ever going to know it’s all dissolved?
Could ultrasonics be used? - though I guess the mass of the crankshaft would negate that?
The (grinding) method of removing the balls Ash put out on his link would be easy enough for most DIYers - given they had enough nous to get the CS out in the first place?

Offline Oddjob

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Re: 750 K2 Strip & Rebuild - help please
« Reply #39 on: March 29, 2022, 12:26:56 AM »
Odd thing is that the 500/550 crank only seems to have 2 ball bearings at each end, so how were the inner rods lubricated?

Didn’t someone post they’d sprayed brake cleaner down the holes from the conrod pin?
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Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #40 on: March 29, 2022, 04:27:49 AM »
Slight change of topic here, but with the bike totally stripped it might be time to swap the front brake from DOT 3 to Silicon fluid. If I plan to keep the existing master, hoses, caliper etc can someone pls advise me which is the best cleaning fluid to use on these components.
(Braced for…. ‘Brake cleaner’! 😂)

Offline Trigger

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Re: 750 K2 Strip & Rebuild - help please
« Reply #41 on: March 29, 2022, 06:51:42 AM »
I changed all my bikes to oke dot 5 silicon. You have to strip the M/C and the caliper completely and clean out with clutch and brake cleaner. It is only a hours work  ;)

It is the worst thing to do is soak a crank in anything, this will just loosen the crap and you not be sure if you have it all out. Do the job once and do it right  :o

Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #42 on: March 29, 2022, 08:01:51 AM »
Cheers Trig, wildo.

Next cleaning job are the clutch plates which @ 3.5mm thickness are good. Plan to immerse them in petrol overnight followed by same in a strong non-corrosive degreaser - will this be inviting trouble?

Ta.

Offline Trigger

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Re: 750 K2 Strip & Rebuild - help please
« Reply #43 on: March 29, 2022, 12:32:05 PM »
Cheers Trig, wildo.

Next cleaning job are the clutch plates which @ 3.5mm thickness are good. Plan to immerse them in petrol overnight followed by same in a strong non-corrosive degreaser - will this be inviting trouble?

Ta.

NOT petrol, it will loosen the fibers off the plate. Used Clutch and Brake cleaner  ;)

Offline K2-K6

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Re: 750 K2 Strip & Rebuild - help please
« Reply #44 on: March 29, 2022, 04:44:18 PM »
Surely the problem Ken, is that you’re unable to directly point any spray at the column of sludge given the geography of the holes. So (useful) mechanical degreasing / washing out is off the cards. Next issue is the 6(?) mm column, 1” high (?) of compacted ‘plastercine’ - how are you ever going to know it’s all dissolved?
Could ultrasonics be used? - though I guess the mass of the crankshaft would negate that?
The (grinding) method of removing the balls Ash put out on his link would be easy enough for most DIYers - given they had enough nous to get the CS out in the first place?

Important I feel to make the distinction here about how the "sludge" gets there. It's not travelling in the oil as sludge (it would be trapped by the filter if that was the case and prior to delivery) it's symptomatic of the oil used passing over temperature threshold at that specific site/location that causes it to bake out the components that stick to the metal. Think more of baked on oil in a domestic oven.
It can only do this by becoming stationary (or close to it) at a site that's above the critical temperature, and one of the important limitations of this oil type. Most likely when crank is stationary after running that has internal structure at elevated temperature, along with the oil sitting there. Essentially you can't cure it with this oil, the risk will always be there. Other less heat intensive sites have an absence of this effect.

 

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