Spare Engine Rebuild.

[mick]

Evening all, i've had this engine under the bench since 2005 and have robbed some parts off it over the years, so i thought i would drag it out and start pulling it

apart & see what i had  , so over the last 3 nights ive been in the shed for an hour or so 

it appears to be a F1 bottom end CB750E 2544770 with F2 Barrels and Head (marked 410 on the back of the head).

Rocker cover & cylinder head came off very easily, camshaft & towers have already been robbed, head gasket just lifted off not stuck to either surface ?

Barrells came off ok to, thats when i got a nice surprise its fitted with a Yoshi 812 kit  bores look very good and pistons look fairly new, the top lip of the

sleeves feel sharp to the touch ? maybe been recently rebored or honed?,

so far i've stripped everything off it and split the cases no major issues so far everythings come apart very easily,

my plan is to strip all the internals clean the cases and paint them and start rebuilding the engine,

can anyone see any problems with the F1 bottom end and the F2 top end and 812 kit?,

i'm sure i'll have plenty of questions as i get into this so watch out  in the meantime heres some photos i've taken so far  , cheers Mick.



 

[Voxonda]

Hey Mick,

Sorry for that Yosh kit, will take it of your hands and get rid of it for you. LOL
Sometimes life still has some small surprises for us.
Good luck with your engine.

Cheers, Rob

[hairygit]

You might find it will go even better with an F1 head, unless they are F2 specific pistons, if they are yoshi pistons for normal sohc engines, the F2 head with its larger combustion chambers will effectively lower the compression ratio. I'm not sure what markings on the pistons identify F2 ones, but if you look at some of the U.S. big bore manufacturers sites you will see one set for K0-7 and F1, and a different set for F2, the F2 ones having a higher crown to raise the compression ratio

[Voxonda]

You are right hairygit,

But do not think the cr is actually lower than oem, but lower than it would be in a K-series head. The dome on the Yoshi piston seems higher than the F2's. Tho maybe the deep pockets will 'even' it out.

[hairygit]

I think you missed my point there, if they ARE F2  yoshi pistons, then all will be fine, if they are K0-7/F1 yoshi pistons, using an F1 head will unleash the full advantage of the Yoshi kit, and it would be a shame not to get the full benefit of a Yoshi big bore

[Voxonda]

I dont think Yoshimura produced specific F2 pistons, if my memory serves me right.

[mick]

Cheers HairyGit & Rob, the only markings on the crown of the pistons are A & E, i'll look into it further and see if i can find any more info, cheers Mick.

[UK Pete]

I am pretty sure they did a yoshi kit for the f2 , your probably in luck and have it,
i have to say you will have all sorts of problems, so save yourself the agro and sell it all to me LOL!
Check out the US site, there was a post on using a f2 top end on a k or f1 engine, i seem to remeber that the oil galleries at the bottom of the f2 barrels might have  to be slightly machined to match, i found this post and it shows you the difference at the base of the barrels http://forums.sohc4.net/index.php?topic=99165, if you search a bit more honda man has a post on the subject, and a guy called yoshi on this forum had a yoshi kit on his f2 some years back, search the user name yoshi on hear and take a look through his posts
pete

[SteveD CB500K0]

Yoshi823 (also named Pete) hasn't been around for a while. He's in SE London. I think I have his number somewhere if you can't contact him via the PM system.

Steve

[mick]

Thanks for all the suggestions and help  , after a bit more detective work on the US site it would appear that i have either K series barrels or F1 not sure which yet?,

i found a photo from Terry in Oz which shows a f2 & k2 barrels side by side,

first pic Terrys


my barrels


my barrels look the same as the k2 barrels but i'l have to try and find a photo of some f1 barrels to compare  , cheers Mick.

[Seamus]

I believe there is a difference with the top of the barrels. The later (K7 on I think) had deeper recesses for the oil seals.

[Seamus]

Top view of a set of K2 barrels.



Sorry about the picture, bit taking it apart. Note round oil seals on top of barrel.

Hope this helps. If I have a better picture, I will post later

[mick]

Cheers Seamus i'l get a photo of the top of these barrels to compare  , cheers Mick.

[Seamus]

I have a set of early barrels (K1/K2) as well as a set from a later bike. The later barrels look the same underneath as your barrels, but different on top. I will photograph this afternoon for comparison

[mick]

Hi Seamus heres a photo of my barrells top and bottom i'll post on the US site aswell might get to the bottomof this one   , cheers Mick.