Topic: Vanishing third gear??

[jonda500]

   Today after gently warming up my 500 for 15 minutes down a dead end road, I did a U turn and took off quite rapidly in first gear. I went full throttle to around 8000 rpm in second and was doing the same thing in third gear when I distinctly felt it pull back suddenly (like a sudden interruption to the expected power delivery), so I reacted by changing to fourth and everything seemed just fine. It didn't take long however, to realise that I no longer have any third gear - when ever third gear is selected it is just like being in neutral.
   My other 500 has a broken fourth gear - but it has a noise and a bad clunky thing happening when ever fourth is selected - and I found a piece of the fourth gear dog in the sump.
Well at least I broke a different gear this time! (I have a spare engine with a buggered primary chain but all it has all 5 gears intact and it also has a good top end that my 550F needs.)
   How could a gear disappear like this? The shifting into third and out of feels normal but it just revs freely... lucky I didn't pay the due rego!! (It's no fun putting up with the necessary double click shifts from 2nd to 4th for any extended length of time - I know this from my other 500. Dang nammit!!)
John

[M 750K6]

Bent shifter fork?

[bryanj]

More likely dogs broke off, it is not common but heard of

[Don R]

 I'm thinking there might be a trend here. The road racers (in england?) used to make special transmissions for these but $$$$!

[bryanj]

I have been riding and working on 500's since 74(got 4 in bits in my garage!) The centre selector was notorious for wearing badly, it came from the 350 twin, and with clutchless changes i have seen 2 damaged gears with dogs ripped off.
The clutches slip at takeoff for a pastime but rarely wear out, my opinion is its the weight in the operating system slowing down the engagement.
Primary chains wear badly and can damage main oil gallery, even more so if carbs not kept synced and ragged, plus primary dampers get like rock.
In us they tell me the rocker shafts oval the cover holes, ive only seen 1 in uk.
Camchain tensioners get fubarred by hamfisted owners but if used as intended are absolutely fine

[jonda500]

Are you saying that you think all three dogs suddenly broke off right at the bottom of each one simultaneously? (There are no weird noises in third, it just revs up freely like a false neutral)
Wouldn't that cause the engine to suddenly rev up when it happened rather than suddenly go tight, as if it it was about to seize, like it did?
John
I guess before I ride it again I'll check the sump for dogs! Leaving three dogs roaming around in the sump doesn't seem like a good idea... I guess my KTM380EXC dirt bike is suddenly gonna get ridden much more for a while now!

[bryanj]

Yes the only 2 i saw broken had all 3 dogs broken off, not necessarily all at the same time as only one would still drive but be overloaded till it sheared

[jonda500]

Ah yes that makes sense now, more of a quick succession of dogs shearing rather than simultaneously breaking off. Thanks,
John

[jonda500]

Well I can confirm that all three dogs have been ripped off - I only found two but I put it in third and turned it over and definitely all three broke! I guess I tipped one out into my sump oil drum - I tried to find it with a magnet but no luck, not happy!

I have drained the carbs & lines and also the tank but around 1/2 an inch of fuel remains in the bottom. It may be a long time sitting unused - I assume I should try and shake all the fuel out? 
John

[Oddjob]

That looks to be 23471-286-010 which is not that easy to find new. I'd also replace 23461-286-030 as it's most likely chewed up the slots where the dogs engage.

The good news is that's it's a common part for bikes such as the CL350 and CB250/350 engines so likely to be easy to find second hand.

I would suspect though it's got a burnt or damaged gear selector and it's that which caused the breakage, those can be difficult to find as well. Looking at it's location I strongly suspect it the right hand selector. Shame as I have the left and the centre NOS.

[newday777]

That looks to be 23471-286-010 which is not that easy to find new. I'd also replace 23461-286-030 as it's most likely chewed up the slots where the dogs engage.

The good news is that's it's a common part for bikes such as the CL350 and CB250/350 engines so likely to be easy to find second hand.

I would suspect though it's got a burnt or damaged gear selector and it's that which caused the breakage, those can be difficult to find as well. Looking at it's location I strongly suspect it the right hand selector. Shame as I have the left and the centre NOS.

https://www.hondarestoration.com/photodetail.asp?hrPart=23461-286-030

[RAFster122s]

Usually when something is not available south sound doesn't list a price or add to cart button but when I used the part number it indicated it was replaced by a different part number and that came up at $135.xx

23461-286-030

https://www.southsoundhonda.com/--xpartsstream#/s/HOM//234A1-390-315//1/y

[Oddjob]

That's the gear it locates into not the gear that is broken. that's 23471 not 23461. CMS for example show stock of 23461 but no 23471.

NPN are showing one dirt cheap which makes me suspect they have no stock even though it allows you to add it to your basket.

https://www.nospartsnow.com/vintage-used-oem-honda-cb350-cb550-cl350-sl350-4th-fourth-gear-29t-23471-286-010/

Edit, didn't notice is was second hand not NOS, they have no NOS.