[Jay_85]

Hey there all.

Hoping you guys can help diagnose a problem that I may have caused myself.

It all began on a fateful Sunday afternoon. It was an unusually warm winters day, it was all going so perfect as I set up for a ride when I did something completely stupid...

I attempted many many times to try and start my bike, a Honda CD250U 1989 which normally starts well, thinking it was my low fuel or spark plugs etc. Alas, it was simply my kill switch was on and I failed to realise this for a good 10 minutes.

And so the stupidity continue throughout this time as I continued to try and start the bike. The starter motor has a very distinctive sound on the bike and you can clearly hear everything grinding away in there as it tries to kick.

I eventually realised the error of my ways, switched off the kill switch and the bike started fine. After short ride (15 minutes to get fuel) I returned home.

Just wanting to be sure everything was ok, I switched off the bike and tried to start it again. This time the bike didn't start (kill switch off this time) and instead of the distinctive clicking and grinding away of the starter motor when I pressed the starter button, there was a whirring sound. Its hard to explain but its as if something snapped or broke because now it sounds like something is spinning that isn't connected to anything or turning what it normally does.

I should clarify the bike is fully services and runs well despite her age. She recently had a new battery installed and is taken for a ride multiple times per week.

I know I am going to have to pull the starter motor apart, but I am hoping one of you gurus can help diagnose based on that info alone. Have I indeed broken something with my incessant and ill-fortuned attempts as starting the bike with the kill switch on?

Any advice would be appreciated?

Cheers,

Jay

 

[J-T]

I would start by ensuring that your battery is fully charged.

 

[Jay_85]

I would start by ensuring that your battery is fully charged.

Thanks J-T. I can confirm it is.

 

[ancientdad]

there was a whirring sound. Its hard to explain but its as if something snapped or broke because now it sounds like something is spinning that isn't connected to anything or turning what it normally does.

Jay, after re-checking your battery and if it still sounds the same, I'd suspect your starter clutch may be slipping. They make an ugly, grinding racket when not gripping properly and if completely slipping, just sound like a starter motor turning connected to nothing. take a look here to see the design of the starter clutch on the back of the alternator rotor, parts #4, 5, 6, 7 and 24 (5, 6 and 24 are typical replacement items)

https://www.cmsnl.com/honda-cd250u-1989-k-england_model2596/partslist/E__0900.html#results

 

[Jay_85]

Jay, after re-checking your battery and if it still sounds the same, I'd suspect your starter clutch may be slipping. They make an ugly, grinding racket when not gripping properly and if completely slipping, just sound like a starter motor turning connected to nothing. take a look here to see the design of the starter clutch on the back of the alternator rotor, parts #4, 5, 6, 7 and 24 (5, 6 and 24 are typical replacement items)

https://www.cmsnl.com/honda-cd250u-1989-k-england_model2596/partslist/E__0900.html#results

Awesome advice thanks ancientdad. I will pull it off the bike tomorrow and have a look to see whats happening. What your describing sounds very likely. When it was struggling and whirring freely every couple of rotations it was sounding like it was ctaching something but then lost it again. This seems like it could be slipping.

I will see how the parts fair once I pull it apart and hopefully its an adjustment rather than purchasing new parts. But if new parts are required I will grab one.

How universal are starter motors anyway? Do Honda bikes have interchangeable ones or am I stuck with the current one for eternity?

 

[ancientdad]

Awesome advice thanks ancientdad. I will pull it off the bike tomorrow and have a look to see whats happening. What your describing sounds very likely. When it was struggling and whirring freely every couple of rotations it was sounding like it was ctaching something but then lost it again. This seems like it could be slipping.

I will see how the parts fair once I pull it apart and hopefully its an adjustment rather than purchasing new parts. But if new parts are required I will grab one.

How universal are starter motors anyway? Do Honda bikes have interchangeable ones or am I stuck with the current one for eternity?

You won't be doing any adjusting as there are no adjustable parts. The "sprag" style clutch grips when the engine is sitting still or turning slower than the starter motor... and you are "stuck" with your starter motor unless another Honda starter will interchange (and some do, I'm just not familiar with your bike as I don't think it was sold in the US) but they are usually pretty reliable and the starter clutch is the thing that usually needs attention. The likely parts to fail are the springs, caps and sometimes the rollers due to wear. worst case scenario, the outer housing can get cracked and will need replacement but that isn't often

 

[longdistancerider]

Just checked the part number and it doesn't cross reference to any US models 31200-KW4-008

 

[Jay_85]

Hey all,

Many thanks for the continued advice. Particularly about the parts numbers.

I've just tried the bike again this morning. When its cold it starts great first time. I rode it for 15 minutes to get it properly warm then switched it off and tried to start it again. No dice, same whirring noise with the occasional sound of it catching something.

I've gone to take the starter off but noticed it feeds into the left crankcase where it obviously goes to the transmission (?)

The cog on the starter (in looking at the below web site) seems to be wrapped in a starter chain which feeds to a larger gear in the crankcase. I didn't want to take off the starter if it meant affecting this assembly unduly, particularly if I have to drain the engine/transmission before opening the crankcase. In short I didn't want make any more stupid mistakes!

https://www.cmsnl.com/honda-cd250u-1989-k-australia_model2597/partslist/E__1000.html#results

Given this new information, especially the failure to start once warm, is there any other further thoughts on this?

Cheers,

Jay

 

[Simo]

It sounds like the pins in the starter clutch are being thrown out by centrifugal force ( like they're supposed to) but are then sticking because of heat from running,
.... engine cools and the pins fall back into place

 

[Jay_85]

It sounds like the pins in the starter clutch are being thrown out by centrifugal force ( like they're supposed to) but are then sticking because of heat from running,
.... engine cools and the pins fall back into place

Thanks Simo.

Not sure what these pins are but I will research. Any idea on a fix for this?

EDIT: Is it number 23 and 24 on this page?

https://www.cmsnl.com/honda-cd250u-1989-k-australia_model2597/partslist/E__0900.html#results

 

[TOOLS1]

The parts you most likely need are #5 and #6 in that diagram.
TOOLS

 

[Jay_85]

Ok thanks TOOLS. I will order those.

I assume I need to get into the left crank case to access these. If so should I be draining the oil in the engine first or is this transmission oil (sorry never been in this part of a bike before)? Also is there anything spring loaded in there I need to be aware of?

 

[ancientdad]

You don't need to drain the oil unless you have it a bit overfull. There are 2 covers to remove, the front sprocket cover and the alternator cover. No spring surprises inside. Then the alternator rotor has to come off the crankshaft (you'll need a rotor puller or a CB350 rear axle, same thread), at which point the rollers and springs/caps may fall out but it's not that complex... take it a step at a time and look at the parts diagram, you'll be fine - it's somewhat self-explanatory if you pay close attention

 

[Jay_85]

You don't need to drain the oil unless you have it a bit overfull. There are 2 covers to remove, the front sprocket cover and the alternator cover. No spring surprises inside. Then the alternator rotor has to come off the crankshaft (you'll need a rotor puller or a CB350 rear axle, same thread), at which point the rollers and springs/caps may fall out but it's not that complex... take it a step at a time and look at the parts diagram, you'll be fine - it's somewhat self-explanatory if you pay close attention

Awesome advice, thanks again ancientdad. I will begin pulling it apart shortly.

In terms of things to look out for to diagnose where the problem is, is there any tell tale signs I should be wary of with the rollers springs? How will I know if something is wrong?

Also, if the problem is the metal expanding under the heat caused by the engine and causing the rollers to stick, will buying new parts make any difference? Is there something else I can do to reduce heat to these parts?

 

[ancientdad]

Awesome advice, thanks again ancientdad. I will begin pulling it apart shortly.

In terms of things to look out for to diagnose where the problem is, is there any tell tale signs I should be wary of with the rollers springs? How will I know if something is wrong?

Also, if the problem is the metal expanding under the heat caused by the engine and causing the rollers to stick, will buying new parts make any difference? Is there something else I can do to reduce heat to these parts?

Don't overthink this, it's not a big deal and there are only a few things to look for. Parts will likely fall out of place when you take it apart anyway, but the parts can only go together one logical way based on how it works. The caps go on the springs and the pair goes into a machined passage in the outer shell of the clutch where they press the rollers into gripping the inner "race", if you will, of the sprocket. You'll see. And BTW, once the parts are all good, it will work as it is supposed to with reference to the slippage when hot - as in, all the time.

 

[Simo]

Don't overthink this, it's not a big deal and there are only a few things to look for. Parts will likely fall out of place when you take it apart anyway, but the parts can only go together one logical way based on how it works. The caps go on the springs and the pair goes into a machined passage in the outer shell of the clutch where they press the rollers into gripping the inner "race", if you will, of the sprocket. You'll see. And BTW, once the parts are all good, it will work as it is supposed to with reference to the slippage when hot - as in, all the time.

I agree untill it's open there no real way of knowing how minor or major the issue really is, at the moment it's just speculation and worry which can easily be fixed with observation and facts.

 

[Yendor]

The SPRAG Clutch has (3) Spring Loaded Rollers that ride in a ramped slot.
When it spins in one direction the rollers slide to the outside and are forced against the mating part by riding up the ramp.

When the Motor Starts and the Crankshaft spins faster than the starter, the rollers are forced back the opposite direction away from the mating part.

The rollers will over time wear in size and begin to slip. - Sounds like you killed yours all in one session of excessive operation.

I would suggest you CHANGE your OIL - ASAP.

There will be a lot of ground metal from the rollers that is now in your crankcase.

 

[ancientdad]

You won't be doing any adjusting as there are no adjustable parts. The "sprag" style clutch grips when the engine is sitting still or turning slower than the starter motor... and you are "stuck" with your starter motor unless another Honda starter will interchange (and some do, I'm just not familiar with your bike as I don't think it was sold in the US) but they are usually pretty reliable and the starter clutch is the thing that usually needs attention. The likely parts to fail are the springs, caps and sometimes the rollers due to wear. worst case scenario, the outer housing can get cracked and will need replacement but that isn't often

The SPRAG Clutch has (3) Spring Loaded Rollers that ride in a ramped slot.
When it spins in one direction the rollers slide to the outside and are forced against the mating part by riding up the ramp.

When the Motor Starts and the Crankshaft spins faster than the starter, the rollers are forced back the opposite direction away from the mating part.

The rollers will over time wear in size and begin to slip. - Sounds like you killed yours all in one session of excessive operation.

I would suggest you CHANGE your OIL - ASAP.

There will be a lot of ground metal from the rollers that is now in your crankcase.

Yeah, I mentioned that the day before. I've never seen a set of rollers in a starter clutch that actually works some, but slips, ever worn enough to consider a lot of ground metal going into the bottom end, they're made of hardened steel as is the "race" they grip. that said, of course it would be wise to change the oil... it always is

 

[TOOLS1]

Since we are "speculating here" I think he just stressed/overheated the springs, taking the temper out of them with all the cranking he did. Doubt he did much damage like constantly cranking an out of time, backfiring engine would do.
TOOLS

 

[Jay_85]

First up, apologies for the belated reply. I have been unterstate with work.

I am back in town and had a chance to work on the bike.

It seems you guys were right. It was a spring and roller issue. Thankfully it was just full of crud and gunk and the whole assembly needed a really thorough clean as the rollers were getting stuck in the gunk.

Took it to a mechanic after cleaning just to be sure and it was confirmed.

So it works well now. Although I am yet to go on a big ride to test more excessive heat impact in the starter operation.

So thanks to everyone for the advice. It seems I dodged an expensive bullet on this one.