I've spit my MC28 engine and on reassembling I've noticed a white paint dot on the gear on the end of the crank. I can't see a corresponding dot on the clutch drive gear, so was wondering how or what you were supposed to line it up with? I'm assuming it's important in balancing the engine, so any ideas on a solution much appreciated?

Cheers

Dan
07919 303762
dan.williams@s-n.com

not sure youll get an answer,
i posted the same question many moons ago, and no one answered, when i ripped the gearbox out of my 21r it had a white dot on both but when replacing with a dry clutch asemblie the dry clutch main gear diddnt have a mark, needless to say i slung it together and there was no ill affect.. not sure if its requied either, as the basket is mounted to it and when you engade or disengade surly your changing the ballance anyway!!!!

Could always give someone like BDK or Total traction a call and see what they say!!

Thanks for the reply rc46. I'll give what you said a go and see what happens.

As regards 'disengaging the clutch changing the balance'. The crank gear and the clutch gear will stay fixed in whatever position you 'mate' them together. It's the gears that provide the balance. Disengaing the clutch will only allow the clutch inner to spin relative to the basket, not the gears, so disengaging won't affect the balance.

Either way thanks for the advise, I'll try it out.

Cheers again

Dan

rc46 wrote:Could always give someone like BDK or Total traction a call and see what they say!!

You could do, but you'd better make sure your belt is nice and loose (and you know when I say someone overcharges, they overcharge properly)

Or you could tryhere, even brand new Honda cranks are not balanced and I believe one of these guys has built the most powerful NSR in the country.
but he can't handle his whiskey....
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

I've had mine apart more times than I can count and don't worry about it. What are you supposed to do when you purchase a new crank and it doesn't come with a gear on it or the marks are gone on one or both parts I'm no expert but I belive the clutch gear is ballanced alone. As I said I have assembled mine different every time and never had any vibrations or any problems.
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1995 A kit TZ 250
1994 Rothmans NSR 300sp SOLD
1998 RM 250 freestyle/motorcross
1998 Meathanol burning CR 500 AF super retard/motorcross/sand dunes/play bike

i have allways marked the bits before ive took them off that way i know its going back the way it was even if it makes no difference

Interseting thread, which gives me some hope... My 21 is horribly vibey - to the point I don't like to ride it - but there is no noticeable noise from the crank (mains sound fine etc.) and I have receipts that suggets that the motor was rebuilt with a refurbed crank less than a thousand km's before I bought it. If there's a dot I'd very much think it's there for a reason? - although a machined-in mark is more common in such applications for the obvious reason.

Does anyone have a japanese workshop manual? The motor rebuild section should indicate if it should line up with something I'd think?

Cheers

Wb

I just looked through my manual...I can't read Japanese but, I see no pictures that refer to that dot. I can see the dot you are talking about, but no special arrows pointing at it or anything.

I would think you can't use the clutch basket to balance the crank, since it's turning what, 6 times faster than the basket. How would that work? You ever see a balance shaft in a car engine? They have to spin at the same speed as the crank.... Maybe I'm way off though.
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MC21
04 NSR50R
93 CBR F2
98 CBR F3 track bike
95 VFR750
89 FL400R Pilot
90 FZR 4/600

Just throw the primary gear on and be done with. Then throw the clutch together and call it a job done.

The primary drive gear is not balanced and does very little. I skimmed mine down on the 300 a considerable amount and just bolted it on. Smooth as silk.

The primary driven gear is balanced at the factory, independant of crank etc.

The clutch basket is just a cast lump, so there would be some benefit to bolting that onto the primary driven gear and balancing the assembly.

If your NSR is full of vibe, then I suspect that the crank is out of true.

Thanks Matt. That has been my ongoing No.1 suspicion for why mine is so particularly vibey, but thought the alignment idea might be worth a punt - even if a paint dot does sound highly unlikely as a long term alignment marker. Any idea what the dot is about then? I've not had my crank out yet so haven't seen one. It's not just a daub of paint on the end gear nut to show it's been done up to tolerance or anything is it?

Cheers

Wb

It's not just a daub of paint on the end gear nut to show it's been done up to tolerance or anything is it?

Might be.

I just built a bottom end yesterday and it didn't have any marks, and I didn't care. I trued the crank so it'll be ok.