Vintage Dirt Bike Q & A

I've scored a set of BRAND NEW crankcases for a 1981 CR450RB and they are absolutely beautiful. The only problem is that where the cylinder skirts go into the cases they are 3mm larger than my old cases and where the crankshaft goes it is 4mm wider. Also, the mainshaft left side bearing is larger than standard. What gives? All these things can be overcome by machining spacers but were there 2 different cases available? The part number for the case set is 11000 KA5 305 so the KA5 tells me it should be for the 181 CR450 but it is really odd. I'm confused.

it seems to be a cr480 case.
KA5 is also used for the 480s.

_________________
80 CR250Ra
80 CR250Ra
78 CR250R
80 CR80
82 Bultaco Sherpa 340
78 Bultaco Pursang 250 MK12
76 Bultaco Frontera 370 MK10
76 Bultaco Alpina 250
73 Bultaco Lobito 125 MK6
76 Suzuki RM125A
90 Kawasaki KX250

The KA5 is a red herring; it indicates a part was first used on the 1981 Honda CR450RB model but does not preclude its use on later models. The first iteration of a Honda part normally ends -000 so I suspect during the production run there was a mod that included a larger bearing housing etc...

_________________
Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

the 480 crank is wider, cylinder skrt is larger, the gear shafts are wider and it has an other bearing behind the clutch than te 450. you can´t really mix it.

_________________
80 CR250Ra
80 CR250Ra
78 CR250R
80 CR80
82 Bultaco Sherpa 340
78 Bultaco Pursang 250 MK12
76 Bultaco Frontera 370 MK10
76 Bultaco Alpina 250
73 Bultaco Lobito 125 MK6
76 Suzuki RM125A
90 Kawasaki KX250

Thanks for your help guys. I've been doing a bit of checking and it seems to me they are a set of cases for a 1982 CR480. I bought them off ebay as CR450RB, they are brand new, still wrapped in the Honda packaging, and they are red with what is quite obviously paint from the factory, not redone by someone.

The 1982 CR480R never had a red motor, so if they were painted by Honda one would assume they are destined for the 1981 CR450R...

...one time I had a '78 RM250CR that blew the primary drive seal. Got a new one, but it still sucked in oil. Eventually we found that the crank and inner dimension of the seal were not the same even though both parts were OEM and for the same model and year. By chance we found another OEM seal from a TS250 of the same age and it fit perfect. It was like during '78 Suzuki had been playing around with the specs of the parts. Hence my thoughts on your situation.

_________________
Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

My initial thought were that this may have been another upgraded parts, as they did with the clutch, pipe and rear shock, but you would think that the standard 450 cylinder and crank would fit so maybe it was just someone at the factory had had too much saki to drink and simply painted it the wrong colour.
It doesn't matter too much because I'm only going to build a garage queen out of it, I'll use my other 450 and my 480RD for racing.
Thanks for your input guys, it's really helpful.