Should this shaft have end movement if I pull it by hand?

[Nurse Julie]

If the pin hole is elongated, it may have been caused by the bearing spinning in the case as some stage in its life. Can you see any evidence of where the bearing may have spun?

[McCabe-Thiele (Ted)]

If the pin hole is elongated, it may have been caused by the bearing spinning in the case as some stage in its life. Can you see any evidence of where the bearing may have spun?

Tbh if the bearing had spun I would have expected the elongation to be radial rather than axial if those are the right adjectives. The crankcase looks odd due to shadowing but the slot for the bearing looks ok.

I have attached a photo if this helps.

bearing location is elongated by Macabe Thiele, on Flickr

[Nurse Julie]

Those definitely look like partial spin witness marks. But, I agree, the ovality would be fore to aft, not port to starboard.
Edit, but if there had been side to side play on the shaft, that would account for the slight ovality being port to starboard.

[smoothoperator]

I would have a look at mine Ted but I’m away. Make sure on the washer as it could easily have got misplaced. Hard to see that ovality giving 1 mm of float.

[McCabe-Thiele (Ted)]

Is the thrust washer behind the needle bearing Ted, there should be a 20mm washer between the bearing and the gear.

Yes, I assume you mean between second gear & the needle bearing.
The end float  is more  than the thickness of the thrust washer - if it was ever dished slightly it isn't now it's flat with some light rotation marks.

I've ordered a new needle bearing, thrust washer & lock pins.
The parts book shows 3 of those thrust washers are fitted somewhere in the gearbox so I've ordered all three anyway as they were cheap enough.

I can't see much point in stripping down the whole mainshaft as the endfloat is basically the gap between the fixed gear on one end of the mainshaft that fits up to the large bearing & the second gear at the needle roller end. Second gear sits next to a fixed circlip on wide splines so it can't really move anywhere except for the gap between it & the thrust washer.

As a last resort a second thrust washer might be a option ?

[400 Cafe Racer]

Hi Ted,

I just spotted your post as I was about to post a query on the roller pins of the gearchange positive stopper. (Soon)

I have my crankcase halves assemmbled and have been measuring the 5 mainbearing borings for size.

Just been in my garage and checked this shaft for end float - mine is solid with no movement between the shaft and the inner bearing, but if I push in and pull out firmly it will move the outer bearing in the casing and shaft about 0.5mm, which appears to be the side movement in the half circlip and its groove.

Hope this helps.

Regards

Dennis

[McCabe-Thiele (Ted)]

Hi Ted,

I just spotted your post as I was about to post a query on the roller pins of the gearchange positive stopper. (Soon)

I have my crankcase halves assemmbled and have been measuring the 5 mainbearing borings for size.

Just been in my garage and checked this shaft for end float - mine is solid with no movement between the shaft and the inner bearing, but if I push in and pull out firmly it will move the outer bearing in the casing and shaft about 0.5mm, which appears to be the side movement in the half circlip and its groove.

Hope this helps.

Regards

Dennis

Thanks Dennis I haven't really started on  the bearing with the half moon clip side of the equation. What I did notice was that when the crank case was bolted up there seemed to be an overhang of the bearing outside the casing that seemed more than I expected. It might be both bearings are not as planted as the design suggests. Perhaps constant gear changes on a revvy little 400 engineb takes its toll on the bearing fittings. Very useful info thanks. Ted

[400 Cafe Racer]

Hi Ted,

This is the overhang on my bearing FWIW.

Dennis

[Nurse Julie]

That bearing is fitting far too proud for some reason, it should be flush 🤔 well, more flush than it appears to be in the photo.

[McCabe-Thiele (Ted)]

Hi Ted,

This is the overhang on my bearing FWIW.

Dennis

Hi Dennis, My overhang is about the same or marginally more. Not sure if new half moon clips would change anything. My bearings were installed dry maybe a smear of Hondabond would help stop further lateral movement. I have a spare gear cluster set that came with a casing from a member. I'm planning to try them for comparison. If they're a tighter fit I will use them. There is no ovalation on the needle bearing locator hole.

[K2-K6]

"It might be both bearings are not as planted as the design suggests. Perhaps constant gear changes on a revvy little 400 engineb takes its toll on the bearing fittings. Very useful info thanks. Ted"

Typically of bikes in general and certainly in these engines, there's essentially no real thrust load of any significance with all the gear teeth straight cut.

Clutch operation is the largest (which should be opposed by the clutch assembly clamping it's shaft on that principle bearing) but the rest of tolerancing is to facilitate accurate movement and controlling engagement of the dogs and their relationship to the shift drum along with it's forks. Insignificant load that would cause wear though in that direction.

Even the crankshaft has no effective thrust bearings as it's not subjected to that force.

In a car with helical cut gearbox and clutch pushing directly onto crankshaft end,  then they need to be mitigated, but on these it's just positional accuracy without much force that could cause components to wear.

[McCabe-Thiele (Ted)]

"It might be both bearings are not as planted as the design suggests. Perhaps constant gear changes on a revvy little 400 engineb takes its toll on the bearing fittings. Very useful info thanks. Ted"

Typically of bikes in general and certainly in these engines, there's essentially no real thrust load of any significance with all the gear teeth straight cut.

Clutch operation is the largest (which should be opposed by the clutch assembly clamping it's shaft on that principle bearing) but the rest of tolerancing is to facilitate accurate movement and controlling engagement of the dogs and their relationship to the shift drum along with it's forks. Insignificant load that would cause wear though in that direction.

Even the crankshaft has no effective thrust bearings as it's not subjected to that force.

In a car with helical cut gearbox and clutch pushing directly onto crankshaft end,  then they need to be mitigated, but on these it's just positional accuracy without much force that could cause components to wear.

Well made point about the gears being straight cut not helical I hadn't given that factor any thought.

One of the reasons I love this site so much is the knowledge of its contibuters being greater than the sum of the whole - its not just "corroborative detail intended to give engineering verisimilitude to an otherwise basic & unconvincing narrative" to misquote Poo-Bah of G&S fame.

[Nurse Julie]

Are the half rings proper half rings? We have had numerous engines through here where someone has been in them in the past and they have used half of a piston ring as a substitute.

[McCabe-Thiele (Ted)]

Are the half rings proper half rings? We have had numerous engines through here where someone has been in them in the past and they have used half of a piston ring as a substitute.

Good question NJ- they look okay I've ordered a new pair for belt & braces - Ted

[McCabe-Thiele (Ted)]

I've just done some work on the two gearshafts - fitted two new end needle roller bearings plus the locating studs and half circlip washer that retain the big ball bearings.
Also replaced the thrust washers (3). Tbh it has not really made much difference to the end float on either shaft.
Most worthwhile part of splitting the case down again is  replacing the primary drive shaft bearings.

I have a spare set of gears in a spare crankcase set that seemed pretty tight until I cleaned them up with some petrol etc and they are pretty much the same as regards end float / side movement so I'm putting it down to the nature of the bike at present.

BiL is going to take a look as he is an experienced rebuilder of Japanese & Italian bikes though not of Hondas oddly enough he likes his Yamahas.
Currently in PAUSE MODE on assembling the crankcase so will do some more frame work.