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December 22nd, 2012, 04:10 PM   #1
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644 to 628cc?

Hi,

I just bought a rebuilt '04 FS650 (644cc) and got one ride out of it before finding metal in the oil. It's now completely apart and looks like failed CB bearings (P.O replaced all bearings except the CB bearings), destroying the left main and causing a bit of scoring on the piston & liner. I want to re-build it properly and have spent hours on here researching the best way to do it.

What I cannot find a simple answer on is if the 628cc pork chop crank will fit the 644cc cases?. I assume the 628cc piston will be needed too due to the shorter stroke. I am going to be buying a complete crank as the big end has some play, and I will be getting the crank balanced and welded regardless, and tossing the counter-balancer in the bin. I'm happy to decrease the capacity slightly if it means a stronger crank and I only want to replace the mains every 100 hours, not every ride. Another bonus is the OEM 628 complete crank appears to be noticeably cheaper.

I saw mention on JBS racing's site under the OEM crank "Can be fitted to older models of Husaberg we strongly recommend this over the older OEM crank"

Anyone care to elaborate? Straight fit? Do I need to match any other parts with it?

Thanks guys
Lee
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December 22nd, 2012, 11:42 PM   #2
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Re: 644 to 628cc?

the cranks are a straight swop and so is the piston. you just simply need the later crank assembly. nothing wrong with the balancer, just put two new bearings in and get going again. as for the piston and liner, I've seen this many a time and have caresingly removed scratches and got on with it.

don't throw the crank - I'll have it. I can probably do you an excellent price on the crank.

regards

Taffy
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December 23rd, 2012, 12:59 AM   #3
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Re: 644 to 628cc?

Thanks Taffy,

That's great to know, as the later ones don't seem to have as many problems with lighter crank & larger pin. I'm happy to sacrifice capacity for a bit more reliability on this one. I would rather keep it simple and get rid of the balancer, it seems unnecessary for my use, cannot see how those puny bearings can take that much load, no wonder they failed. The less moving parts the better I reckon.

The piston and bore are lightly scratched, at first glance I thought it would be re-usable, but then I thought while it's apart I may as well replace it. If I go for the 628 crank I'll have to get a piston anyway.

Oh and looking at Wossner piston kits, they list the same part number for 2003-2008 model 650's, wouldn't the piston have to be different when they changed the stroke?

Are you saying that the crank and piston from the later model are both retrofittable, or the crank is retrofittable and the old piston will work with this crank? I cannot think how this is possible, but I have a feeling it might be, the piston wouldn't travel all the way to the top of the bore would it?

Thanks,
Lee
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December 23rd, 2012, 02:58 AM   #4
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Re: 644 to 628cc?

you shouldn't need to change anything else. the engine will be very rough at low revs without the balancer. I think they changed the crankcase height by the 1mm.

1mm throw = 2mm stroke.

regards

Taffy
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December 23rd, 2012, 03:39 AM   #5
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Re: 644 to 628cc?

OK, seeing as though the old balancer bearings for my 04 are unavailable therefore supercede to the complete balancer for the later model crank, would I be able to use your modified replacement balancer bearings in my old undamaged balancer weight to keep the balancer with the later crank? Would it be as reliable as no balancer at all? Is the weight of the old balancer going to add vibration with the lighter crank? Or doesn't it work like that? Would it be worth getting the whole crank/balancer assembly balanced, as I've read on here that even stock they aren't balanced as well as they can be?

If I go to the parts diagram for the 2005 model when they changed the crank, there is a picture of both style cranks, with a line pointing between them, so I'm sure its retro-fittable. Every source of piston kits shows the same part numbers for all year models.
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December 23rd, 2012, 04:26 AM   #6
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Re: 644 to 628cc?

ill have a quick go at it since i see taffy is not online to give yo real info......about the bearings, do you have the engine apart already, you should be able to order generic skf bearings, this is what i did on my engine build, read the number off of the side of the bearing then type in in under a google search and see who has it, i found simplybearings.co.uk to be a very cool place to deal with and have everything in stock, and an easy website to navigate......

as far as the balancer i also would recomend that too, the cranks are not balanced since they have the counterbalancer that brings them back into balance, so basically the way i understand it is that the crank is actually intentionally unbalanced by a fair amount for this reason that the counterbalancer will bring it back into balance, if you insist on removing it then your new crank should be rebalanced, i think there is a value to balance the crank to in the doc if you remove it.
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December 23rd, 2012, 08:34 AM   #7
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Re: 644 to 628cc?

I didn't think an early balancer would work on a later crank or a later balancer on an early crank.... I thought I read somewhere gears would not mesh correctly.
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December 24th, 2012, 03:02 AM   #8
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Re: 644 to 628cc?

you mustn't mix stuff from the 2001 with the other years (2002 to 200 otherwise the earlier balancer (2002 - 2005) works fine with the pork chop crank. so re-fit the balancer assembly and don't run without it is MHO on it.

as for the bearings themselves, well they are special. you can't buy them off the shelf. they start out as 6906s and have to have 1.5mm ground off both faces so the width comes down from 9mm to 6mm. then you have two of them in the 501/550/650 and only a single standard 6906 in the 400/470.

you can't really convert to a single or back without a lot of work.

here is a link to my advert for the bearings. clarky sells them as well and I just can't believe he's making any money at all? It costs me 8-10gbp to get each bearing ground down. so where's the profit?

http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=261135770746

regards

Taffy
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January 4th, 2013, 03:49 AM   #9
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Re: 644 to 628cc?

Taffy,

I'm just wondering what variations of pistons I can run with the later crank in my cases. Unfortunately I don't have the crank in my hands yet so can't bolt her up and do any measurements. So the deck height of the cases may be different with the shorter stroke, but everything I've read says the 628 crank is a direct replacement, I am sure the compression will be less than with the 644 and the same piston. Would it be worth using one of your "tall boy" pistons to make up for the compression? Keep in mind that I will be using this mainly for weekend road riding, and probably the occasional track day, so I do not need ultimate performance (they're already freakin amazing stock standard). I tried doing some maths, but how much difference do you think the 2mm stroke and 1mm(??) deck height difference going to make to my compression?

I will test fit the new crank with the old piston & sleeve when I get to that stage before I even order a new piston, but just wondering if anyone has been through this already. I found mention on these forums of a couple of guys saying they know for sure the crank will work, and JBS say they recommend the later OEM crank over the earlier one, but I can find no mention of what anyone has done piston wise. Excuse me if I'm asking the same stupid questions again, I'm just pondering while I wait for my crank to arrive.
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January 4th, 2013, 06:10 AM   #10
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Re: 644 to 628cc?

Originally Posted by CaptainRedline
Taffy,

I'm just wondering what variations of pistons I can run with the later crank in my cases. Unfortunately I don't have the crank in my hands yet so can't bolt her up and do any measurements. So the deck height of the cases may be different with the shorter stroke, but everything I've read says the 628 crank is a direct replacement
so wait then! you can use your old piston as a measuring device.
Originally Posted by CaptainRedline
I am sure the compression will be less than with the 644 and the same piston.
yes it will and that is why you won't want a concave 628 piston but something flat or flat + +
Originally Posted by CaptainRedline
Would it be worth using one of your "tall boy" pistons to make up for the compression?
as the advert says: I can do anything you want for 20 quid!
Originally Posted by CaptainRedline
Keep in mind that I will be using this mainly for weekend road riding, and probably the occasional track day, so I do not need ultimate performance (they're already freakin amazing stock standard). I tried doing some maths, but how much difference do you think the 2mm stroke and 1mm(??) deck height difference going to make to my compression?
you'll only lose on the stroke - NOT on the compression
Originally Posted by CaptainRedline
I will test fit the new crank with the old piston & sleeve when I get to that stage before I even order a new piston, but just wondering if anyone has been through this already. I found mention on these forums of a couple of guys saying they know for sure the crank will work, and JBS say they recommend the later OEM crank over the earlier one, but I can find no mention of what anyone has done piston wise. Excuse me if I'm asking the same stupid questions again, I'm just pondering while I wait for my crank to arrive.
JBS race sidecarX

regards

Taffy
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