Naughty step GT550B

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yeadon_m
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Naughty step GT550B

Post by yeadon_m »

Hi folks,
The NSB 550B has been behaving itself engine wise. Since replacing the oil pump & piston pin on the previously noisy left cylinder, it’s been running sweetly & I’ve steadily built up a few more miles on the way to running it in. Cautious optimism.
That said, it used to be a good starter on the electric foot but over time became a non starter on the button & a bit of a bugger from time to time on the kick start.
The carbs needed adjusting so they’re on the bench.
Meanwhile, I’ve checked the starter motor, which checks out fine. I’ve not taken it apart but it spins very fast indeed on the bench.
So to the clutch cover & starter clutch. Sure enough, I can see that, often and always after a couple of seconds on the button, the bronze gear riding on the one way clutch is merrily spinning the wrong way, without gripping. I’ve dismantled it and at first, while still covered in gear oil, I could sometimes reproduce this fault. Stripped it completely & while I can’t point to the specific failure, I think the sprags or whatever they’re called are too loose in the metal holding clip. I washed all the lube out of it and after reassembly, for a few seconds, I thought it had started working again, doing what it should in response to the button. But no way was it going to be that easy...soon started it’s failing to grip one way. So I’ve ordered on of those one way bearings from Marcel. He says he’s dispatched it, so fingers crossed.
Meanwhile I’ve a few days to sort the carbs out.
Thankfully my other bikes are kinder to me.
Hope everyone is keeping safe,
Cheers,
Mike
Ps: it’s wearing it’s smaller siblings 380B tank. Nice isn’t it?
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Alan H
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Re: Naughty step GT550B

Post by Alan H »

It's certainly a patience tester Mike....
Proof that four strokes are over complicated
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Harrymail
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Re: Naughty step GT550B

Post by Harrymail »

Hi Mike

I know you are a bit of a carb guru, and I have been following closely in your footsteps with my 550A. Something I have just come up with is mismatched needles and needle jets.

Early model 550's and all US years are fitted with 5DH21 needles in slot 4 with P-0 Needle Jet.

UK models MAB are fitted with 5D1 needles in slot 3 with a P-4 Needle Jet.

Thats three sizes different in the Needle Jet and the Needle has a very different taper. If you have a mix of the two then you end up with either a rich or weak mixture through much of the range. I checked mine a couple of weeks ago and found I had P-0 Needle Jets with 5D1 needles which is incorrect. I have now changed the Needle Jets to P-4, correct for MAB models. Not had chance to try the bike yet, but I'm hoping that the slight bogging down I was getting at wide throttle openings will be gone. Still running in after the second rebuild, so early days yet but I'm hoping that this may also help the mpg as it was drinking fuel. The changes coincide with the Nikasil cylinders I think.

If you haven't already, it might be worth checking what size your Needle Jets are.

Regards

Paul
Currently without a GT, but looking
2003 Yamaha Fazer 600 Blue
2020 Triumph Street Twin Red
1968 BSA Bantam Sports Red
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yeadon_m
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Re: Naughty step GT550B

Post by yeadon_m »

Paul,
Thank you for that reminder. I noticed it long ago, but as I have two sets of carbs, I really don’t recall what I’ve got at the moment.

Folks,
Just been in communication with Marcel V in Holland. He is sending me the superseded one way bearing & says it will fit if I remove the thrust washer bearing which sits under the one way bearing. We’ll see soon enough!

Cheers,
Mike
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Alan H
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Re: Naughty step GT550B

Post by Alan H »

What happens if you have need of a thrust after it's been discarded (willy nilly?!?!) though, Mike? :shock:
Proof that four strokes are over complicated
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yeadon_m
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Re: Naughty step GT550B

Post by yeadon_m »

I’ve had a look at the clutch basket & one way assembly. If I lift out the thin ‘thrust bearing’ that sits under the bronze starter gear as well as the thin washer, I think the wider one way clutch bearing will fit & drive as required. But the bronze gear will then be skittering along the face of the recess in the basket. I can’t believe that would be silent, though I doubt there’s much thrust when the clutch is spinning, so we’ll have to see. The wider one way bearing won’t accommodate a slim, internal circlip, but it can’t go anywhere as the basket is bolted to the input shaft with an impressively large but.
Provided it’s not noisy, I feel optimistic. I struggle to believe knowledgeable suppliers like Marcel don’t already know whether this works like the original part or if there are compromises to install it.
Anyone actually used the superseded one way bearing?
Cheers!
Mike
Ps: I’m rebuilding a set of carbs I last rebuilt in 2013. A bit depressing scooping the horrible black gunge out of the carbs arising from dissolved accordion rubbers which seal the carb tops. I’d already replaced one but luckily I had two spares. Blooming expensive things!
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Alan H
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Re: Naughty step GT550B

Post by Alan H »

yeadon_m wrote: the basket is bolted to the input shaft with an impressively large but.
I would imagine there's few worse things, but I daresay a large spanner would tighten it up..... :shock:
Proof that four strokes are over complicated
barney01
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Re: Naughty step GT550B

Post by barney01 »

Mike i had the bigger bearing from Reiner last week. I tried as you said lifting out the thrust washer and the flat bearing. This meant that the bigger bearing would fit in the recess and comes flush to the top of the basket. But you cant fit the circlip.
My point is this. The starter clutch bronze gear wheel has a flat surface for the bearing to grab hold of. That is only 13.5mm wide so the larger 15.7mm bearing wont have all of the teeth on the wheel.
I made the descision to send it back and he refunded me.
I am not saying it wont work, it probably will. I just wasn't happy with it :D
NO SMOKE .......NO POKE
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yeadon_m
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Re: Naughty step GT550B

Post by yeadon_m »

Cheers Barney. I haven’t compared my starter gear with your picture, but my memory is that the diameter that the one way bearing sits upon is constant on mine. I can’t see from your picture for sure, but perhaps yours has a machined portion exactly the width of the slimmer one way bearing and the diameter of the starter gear is greater as soon as you go wider than the slim gear.
They really are oddities. Even though I can see & hear the one way gear not gripping properly when on the engine, if I take it off, the one way bearing works perfectly when turned by hand. The conclusion I take from this is that a good feeling from a bench test is a necessary but not sufficient condition for it to work on the bike. And the only way to find out is to fit it!
I’ll have a go soon. I can only try the wider bearing and if that doesn’t work & fix it, I’ll be knocking on Alan’s door to see if he has a surplus starter gear, even an older style one!
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Alan H
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Re: Naughty step GT550B

Post by Alan H »

You can knock on my door anytime Mike, but I just sold all my old style clutches to Barneys mate, fitted BW clutches to both my 550s and getting rid of my spare (when I get a needle roller for it) to another 550 owner without a clutch.
So I won't have any clutch bits at all (other than plates etc.)
Last edited by Alan H on Fri Jun 19, 2020 9:17 pm, edited 1 time in total.
Proof that four strokes are over complicated
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