Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Safo on December 28, 2018, 06:14:26 PM
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Hi everyone
Some of will have seen my intro in newbie section.
The motor is now fully striped and I'm looking at the 3rd gear issue, which I now to be a problem the thing is there is signs of wear but not execesive, the forks look straight
Does anyone know how long the 3rd gear dogs should be should be
Thanks
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We have a customers CB500/4 engine in for overhaul at present. If you can wait until tomorrow either I will measure it or get Trig to and let you know but it's usually the width of the dog end which is measured and the service limit is in the service manual.
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If you assemble everything into the top case with selectors engaged you should be able to turn the shafts(both need to turn) and select all the gears to visually check of engagement.
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Yes I Already tried this, looks OK, also tried to Separate the gears by taking up all slack in selector mech but they still seemed to have purchess, just found 0.9mm end float in selector drum, selector fork measures 4.9 Grove in gear is 5.15 I think is OK what do you think? Tried to post pics but to big
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Sorry no can diagnose without pics i am afraid.
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If theres wear in the actual dogs on the gears they can jump out of engagement under load I think. Selector forks seem to be a common culprit for wear.
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Lets start from scratch.
(1) What was the 3rd gear issue in the first place
(2) You dont move 3rd to engage 3rd
(3) It really is impossible to diagnose by mystical guesswork
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Safo, it sounds as though you are trying to post full size photos (as in Meg size) and not jpeg which are smaller and don't exceed the size limit you can post.
When I take a photo with my phone I send it to myself via a message. When I recieve the message I save the photo to my phone as this is automatically reduced in size to a jpeg. You can then attach this saved photo to any forum reply using the attachments and other options located below the message box.
Hope this helps.
Dave
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Thanks everyone will try again
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OK, if this has worked there should be 2 pics
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Yep that's worked👍
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And yes it has, top one is 2nd gear selected by turning drum by hand below is 3rd selected, it seems to be fully engaged but when the bike was last running it used to try jumping out of 3rd but never actually did so it was a case of short shift to 4th but it spoilt the ride, as I said before there is signs wear and evidence of the gears trying to separate but I still don't think it's excessive, should I turn my attention to the claw that pulls the drum around, is this a part that wears?
Thanks in advance
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It may be the light of the flash but the countershaft pinion (second photo) appears to be worn to me? I've never had a CB500/550 and maybe this is normal? I'm sure someone with better knowledge of these bikes can confirm and offer some insight though.
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The selector has overheated and probably worn to excess or is bent. If it is the centre one you are going to have trouble getting a new one, last one i saw advertised on ebay was over £100 delivered. I think it is the same as the 350 twin but will have to check numbers again and if so there are lots about used in the US and for some reason they dont wear as much in the 350.
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I am not understanding "it tried to jump out of 3rd" ? Was it going in to a false neutral between 3rd to 4th ?
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The dog drive looks like it's been spitting back out from the look of the radius on those drive faces.
You need to compare them with a known good set to see how much they are worn. But they don't look disposed to staying in place under load. Don't think you could rely is on them even if everything else wash perfect.
If under load it's trying to separate the dogs it will heat up the selector fork as it'll be "leaning" on it which it's not supposed to do.
Is that back dog of the three sticking up a different size to the others? Can't get a good view of it in the photo, and is it supposed to be?
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Pictures of Good centre, Right slight ware and a good left ;)
[attachimg=1]
[attachimg=2]
[attachimg=3]
[attachimg=4]
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No Trigger it just felt like I wa pulling and releasing clutch very quickly
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Sounds more like a clutch or push rod problem ;)
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Would it do it only in 3rd and not in any other gear?
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I think k2 is on the right path, looking closer, there is a a lip on the fork, which suggests it's had some pressure from the gear, but contrary to the pic is not blue so hasn't had too much, it certainly isn't as good as the ones in the picture that trigger sent
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OK folks, reckon it's time to accept that I've, (well the wife that is) cos it's her bike has to spend some big bucks and find some new bits, gonna see if silvers still got them repro gears I saw a few months ago
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The only lip i can see is on the dog. Maybe some better pictures would be better ;)
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Glad you asked for a better pic Trigger, this confirms what's been going on
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I take it, that is the Right one ? Will have L & R on them ;)
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Yes it says R2, but things just got worse, the middle one has suffered tne same, I also found the drum bolt in the top case wa loose the locking washer had bent back
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You need to check what you need against a parts book. Anything with 323 middle number is 500 any other middle number is another model.
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Thankyou,will do, a mate of mine has a 450 twin bottom end, some say the k4 forks are same have I got a chance?
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Thankyou,will do, a mate of mine has a 450 twin bottom end, some say the k4 forks are same have I got a chance?
Not the same !
PN for the right is 24211-323-000 and PN for the centre is 24212-286-030, that relates to Honda Motorcycle Models with no year CB350 A GEARSHIFT + CHANGE PEDAL + SHIFT DRUM + SHIFT FORK
Honda Motorcycle Models with no year CL350 A GEARSHIFT + CHANGE PEDAL + SHIFT DRUM + SHIFT FORK
Honda Motorcycle Models with no year CB500K2 A Gearshift Fork / Drum
Honda Motorcycle Models with no year CB500K1 A Gearshift Fork / Drum
Honda Motorcycle Models with no year CB500 A Gearshift Fork / Drum
Honda Motorcycle Models with no year SL350 A SHIFT DRUM + SHIFT ARM
Honda Motorcycle Models with no year CB350G A Shift Drum / Shift Fork
Honda Motorcycle Models with no year CB350K2 A Shift Drum / Shift Fork
Honda Motorcycle Models with no year CB350K4 A Shift Drum / Shift Fork
Honda Motorcycle Models with no year CL350K2 A Shift Drum / Shift Fork
Honda Motorcycle Models with no year CL350K4 A Shift Drum / Shift Fork
Honda Motorcycle Models with no year CL350K5 A Shift Drum / Shift Fork
Honda Motorcycle Models with no year CB350K3 A Shift Drum / Shift Fork
Honda Motorcycle Models with no year CL350K3 A Shift Drum / Shift Fork
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Snookerd then, could be a long game,
Thanks all, will let you know when I find a way out
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Look for someone in your area that makes gear cogs, that can help with your problem. I had some dogs welded and heat treated some time ago and they worked very well with the new cogs that they made ;)
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Ebay US and you will find CB 350 twin parts there, if you have to buy a complete box just tell the seller to ship the selector drum and forks and bin the rest
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Ebay US and you will find CB 350 twin parts there, if you have to buy a complete box just tell the seller to ship the selector drum and forks and bin the rest
That only sorts out the middle fork mate ;) The right one was only fitted to the 500 four.
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https://www.ebay.com/itm/1972-1978-Honda-cb500f-cb-500-f-cb500-Transmission-Trans-Shift-Forks/202527543516?hash=item2f279510dc:g:KjoAAOSw9g1cCUIX&redirect=mobile
Any use?
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https://www.ebay.com/itm/1972-1978-Honda-cb500f-cb500-Transmission-Gears-Shafts-Trans-Tranny/202527538479?hash=item2f2794fd2f:g:qggAAOSwolpcCUAz&redirect=mobile
Could be from same engine, is it same supplier?
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I know the other two dont fit but they can be got nos it is just easier to ask the seller for all three and they frequently leave them on the drum which is the same as 500.
Those two links are the same seller but carriage might be high as you can only get airmail now.
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I know the other two dont fit but they can be got nos it is just easier to ask the seller for all three and they frequently leave them on the drum which is the same as 500.
Those two links are the same seller but carriage might be high as you can only get airmail now.
I know and you know but, other members may not know mate ;)
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I have almost a complete NOS gearbox for the 500 including 2 NOS selectors but not sure which they are, one is certainly the centre one but the other could be left or right. I could look if your interested.
If you have a parts book list part numbers instead of descriptions as it avoids confusion.
I was waiting for you Ken ;D ;D ;D
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What can I say, I still have loads of parts in the loft
Good thing you do Ken. I know many people would have been at a loss without your roof top Parts Department full of rare parts 👍👍👍
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Trigger, having a bad day mate, still awaiting DVLA extrication of finger!
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Trigger, having a bad day mate, still awaiting DVLA extrication of finger!
At least it is only the finger mate, it's when you have the DVLA thumb you have problems ;D
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Well that's brilliant, thanks, will get the missus on to go on ebay tomorrow, and if oddjob will part wi the bits yes I am interested, by the way if anyone is going to the winter classic show at Newark this weekend I will be on the crmc racing club stand
Thanks again
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One thing to check that i just thought of is that when the shafts are in the case do any have excess movement along the shaft as there are several washers in there that could possibly break(even if i havent seen it) and/or been misplaced or lost on a previous stripdown.
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The only gear with any excessive play is the 1st gear on the layshaft, all others (the fixed ones) seem to have their respective circlips and washers and feel ok.
Selector forks ordered from ebay
Looking for 4th gear L/S and L/S gear
HAPPY NEW YEAR!
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I cant remember which gear but there is one that must be fitted with its mating gear on the other shaft as the tooth profile was changed in production. The only way i found out was when i tried to get one decades ago and was told it was superceeded and came as a pair. Sorry cant be more help
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Isnt it 4th you move to lock up 3rd?
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OK, thanks for the tips Bryanj and yes that's correct after studying things when you shift to 3rd the right selector moves the 4th gear on the layshaft into what is just called a layshaft gear via the dogs which then connects it to the mainshaft for 3rd
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OK, oddjob I stand corrected on my terminology as I got it from the Haynes manual, already paid for the selectors, they should be here next week, if they are no good it's £60 down the drain, and I may have to shelve the project untill I get all the bits we need,
The bike was last used in 95 up until then the oil and filter were changed at the latest every 2000m, but l don't think we ever did that much in any one Yr
must admit there was, still is a film of black crudd in the bottom of the sump. How much would you want for the centre fork?
Thanks
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Those doggies ( Forks) look pretty good to me Oddjob. I think you have been looking at too many NOS parts for too long ;D ;D ;D
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[attachimg=1]
[attachimg=2]
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If they are like that when they arrive, think I will be happy cos they look 10 times better than whats in there now
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I see what you mean oddjob, you mentioned drum out of line?
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I have a cb500/4 that has this issue on 1st and 2nd, what I am wondering is what is the possibility of getting the forks built up with weld - grinding back to profile and re case hardening them... we case hardened tools in collage but were working to much looser tolerances of 1/4 mm. That's obviously way too crude for an engine. I'm kind of curious to know if anyone here has experience of a engineering shop and could offer insight into how they avoid oxidation losses of the steel when heating during case hardening, plus distortion - barring those factors it's something one might attempt at home, given a kiln and accurate pyrometer, plus a lathe / mill. A bit of a skill stretch for me but most of the kit is here and a dead selector fork is dead, no harm in trying to fix it, rather more of an issue is the groove thr fork runs in on the gear, that I imagine is rather harder to re machine. The dogs seem less prone to wear and rather harder to repair / higher risk. I guess the groove could be ground smooth at an oversize and the forks built up a bit to match..... Thinking long term here, supplies of new bits running out, good used bits likewise. My bike got well past 200,000 miles before the box succumbed, others might not last so long. I would think getting new bits made would be prohibitive cost wise.
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It's worth checking the hardness of the fork first Matt.
Just run a metal file across non toleranced surface of a knackered fork to see if it'll cut it. It's usually the gear's that are heat treated material for obvious reason, fork's in many gearbox applications are only bronze.
A healthy gearbox would not routinely "run" the forks under load generally. The gear is not side loaded when driven on these straight cut boxes.
If they wear as discussed above, touching diagonally opposite faces on the pads, gear component making a mark further up, then it would suggest the fork is bent such that it's not presented to the gear slot perpendicular/true.
If that's the case, then if the dogs aren't engaged fully they can try to spit themselves back out of gear. This is usually obvious as the damage on the dog's noses gives evidence.
The original gears in this thread look like that's happened, you can see it starts to round off the leading/driven edge of the dog as well, making it even harder to stay in gear when loaded.
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On the ones I have closely examined the gear has been a bit rough on the corresponding faces. Really need to look again though as it has been a few years. It might be interesting to make a rig to test the dogs ability to stay in engagement under load without the forks. Might only need to be a spring balance on the output, maybe on a bar welded to a worn sprocket, compare the jump out force on a problem box and good one - I would expect the good one not to but a bad one to be still quite hard to get jumping unless awfully. I have 2 cb500 engines that stuck in 2st and second gear particularly. Rather the opposite of the jumping out issue. I never did investigate further. Ax I clear my shed of BMW boxer bits I'm thinking ahead to get back onto my cb500 project. For now it's getting a cb550 mill, because that was close to hand and looked good to go, but cb500 is looking more tempting as times have moved on, it's going to be a fun bike, not the mile munching commuter it always was when last running. Mot no longer relevant, being stock for insurance might help. Being as it was when I did most of my miles would be nice. A sorted cb500/4 is just so very good.
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Yes I will oddjob, as I don't want to strip the engine again
Got a full oil seal kit and new wiring loom from the Honda guy at Newark at the weekend, also bought 2 sets of c/cases from the auto jumble, wi part g/box
Right and centre selector forks no good on both sets but one countershaft gear OK, and one full pushrod
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After paying £17 import tax the forks are finally in my hands, the L and R are like new but as oddjob said the centre one is just showing first signs of wear but as I said before, it's ten times better than whats in there, a big thankyou to trigger for the bolts
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Hi all, I know it's been a while since last post so here is a update on the progress.
After fitting the selectors that I bought from the US I began the search for the formentioned gears, I soon found out that this was going to to be a long search as all the gearboxes that I found, 3 in total had all suffered the same bar one and that had been robbed of the c/shaft 3rd but the 4th was OK so I bought it just for the one gear, finally just 2 weeks ago I got a gearbox in great condition from somone has built probably the best 500 classic racer I have seen, anyway as it stands the bottom end is now rebuilt and back in the frame, now awaiting std piston rings from silvers, about 3 weeks, will post updates and some pics soon
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Well after a long layoff, partly due to sourcing parts and other projects, theres been a leap forward this last week, thanks to the nice weather
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Hi all, project now finished at last, she's being ridden again, here is a pic after yesterday's second test ride,
all seems OK even the front brake gave a little hint of a sqweal, time to hand the keys to someone who is looking fwd to a ride out, will post more pics
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Ooooh, that looks very good.
I'm always surprised just how stunning the candy paint on this era bike looks, that's from dull/twilight right up to full on unthrottled sunlight :)
Fabulous.
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Thanks K2-K6, this forum has been a great resource for info, advice and help, and will continue to in the future i am sure