1981 CB250 engine needed asap !!

[Maffoo]

does anyone know where i might find a 1981 (or thereabouts) Honda CB250N engine? the twin cylinder one

i fubared mine yesterday :( 2 days after my rebuilt bike got rego'd & warratned !! grrrr

condition is not important, as long as its running, & preferably in auckland so i can go get it

any help appreciatted !!:rockon:

[xwhatsit]

As I said in the PM, Econohonda is your friend. They often has complete spare motors. If you do an exchange with your busted one you might find price bearable.

What happened? That's really shit, man :(

[Maffoo]

yeah ive been meaning to ring them

im waiting on a couple of wreckers to get back to me as id rather not have to bring one up from down there

well i was meaning to do an oil change on it 'next week'
but then i decided to ride it to Mercer & back just for a blowout
nearly made it back !
died on the motorway yesterday with a bang
not exactly sure whats wrong with it, but it sounds terrible


failing that, does anyone know if any other engines fit this bike?
like, from a later model, or different model, honda

[xwhatsit]

Whoops I just realised I didn't talk to you in a PM, that was Magua. Damn people with similar names wot own Superdreams!

I think the CB400N will just bolt in. The CB250/400T, CM250/400 engine is the same lump, but I would think the 250N would be more common. Still, more models to look out for.

Sounds terrible? They're relatively simple motors, and pretty robust, so you may be able to rebuild it on the cheap.

You say it died on the motorway with a bang, and now sounds terrible (so it still goes?). Exhaust valve hit piston, bending valve, keeping it stuck open? The camchains are notorious for wearing out quickly, so a really worn and neglected one (don't forget, manual adjustments!) could cause valve interference.

[Maffoo]

it hasnt fired since then
but turning it over sounds terrible
i just about have the motor out :D
no-one has one, so im stripping this one

steep learning curve this !!

[xwhatsit]

steep learning curve this !!

Ahaha, know how you feel. If you're ever bored shitless (or want to become so), look up my earlier thread when I was forced to rebuild my 250RS.

Surprised nobody's got one; it sounds like an engine wrecker's dream -- relatively unkillable motor, but with atrocious handling and poor brakes :lol:

That's a right shame. Do oblige us and post up pics so we can share in the misery. Whereabouts in Auckland are you? I'd be happy to lend a spanner hand if you want.

[Maffoo]

I live in Birkdale, & i will be getting pics ... where are you? feel free to pitch in...
I will throw up some pics of the completed bike a bit later
i did make a thread on here when i first finished it
ill see if i can find it

yeah the wreckers all said that by now, all the engines had gone into bikes with blown engines :D


edit - heres pics in this thread !!
http://www.kiwibiker.co.nz/forums/showthread.php?p=1027078#post1027078

[xwhatsit]

Heh, yeah I remember that, the Superdream with the 250RS headlight. Birkdale's not that far from Mangere Bridge :laugh:.

I've got an extensive university break, work in the afternoons though. Got a workshop manual?

[Bonez]

Another option is CB400T or N donk. Fits straight in. But I didn't tell you that ok? Also a rebel 450 engine may fit, but unsure on its electrical setup is compatable with the earlier units.

[Maffoo]

Ok i have n update !!

on the cam it has like, wings, which have bolts in them, to bolt to the gear that the cam chain turns ... one of those bolts came out, which put so much pressure on the other side that it SNAPPED !!!! i have the engine in pieces (i have pics but telecom is having issues with sending them)
im planning on looking online for a workshop manual... i need to know how to realign the cam to the crank, & the torque settigns for the head... i think thats all i really need
io found a complete honda manualonline in pdf form, which i have, but thats on my other PC which is packed away so i need to find it again :(
I will be doing that search tonight ....

[xwhatsit]

Holy shit! That's exactly the same thing that happened to my bike! Check out this photo: http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=46509&d=1163992914

So it's not so bad. Your biggest worry is probably what I had -- heaps of swarf down the camchain tunnel and getting picked up in the bottom end. Is the CB250N a roller bearing crank? Can't remember. If it is, apparently that improves the chances heaps. Don't keep turning the engine over any more.

Hopefully the head is still OK?

Spectacular, but fixable :thumbs-up:

[Maffoo]

i will post pics later :) head is fine, engine turns freely :)
i have to go sort dinner now, check back in a few hours formore !!

[Bonez]

Use a suitable lockite on the threads when you attach the camchain sprocket to the cam next time.

[Maffoo]

yea ill remember the loctite
shame the last guy didnt think of that :D

[Warren]

Those bolts are M7 too! I lost mine and had to buy longer bolts for $5.50 from a bolt store as they are impossible to find and grind them down (Of course I later finding the originals).

Some guy brought my CB250N with a slightly shagged engine so he could put the good engine of his one into the frame of my old one.

[Warren]

If you want the two bolts that I made then PM me with your addr and I will post them. I swapped the originals back in so only have my custom ones that had to be ground down at both ends to fit.

[Maffoo]

thanks but i rescued one & got a second one (to replace the one that fell out in the first place) from the wreckers where i got the cam

props to Action bike wreckers, barrys pt rd !

i have pics of the job thus far... should i post them here or make a thread somewhere more appropriate?

[xwhatsit]

Ah just post them here -- this can be the gory rebuild thread :D

Sweet, sounds like you got off lightly then. Sourced a new camshaft? Or was it just the bolt that broke? Valves OK -- didn't hit the pistons?

Get some cheap oil (car oil, doesn't matter) and flush the oil through a few times before starting the engine. I pulled off the side cover to scrape out most of the swarf. When you first fire up the engine, idle the engine for 10 minutes or so in the garage, then do an oil change. Do it again if you like. Then do an oil change within 500kms. I did that and my bottom end seems to have survived.

[Maffoo]

http://i46.photobucket.com/albums/f127/bmwmaffoo/6.jpg
http://i46.photobucket.com/albums/f127/bmwmaffoo/5.jpg
http://i46.photobucket.com/albums/f127/bmwmaffoo/10.jpg

oh lame... it doesnt display images like i was hoping

[Maffoo]

i also need to find the honda workshop manual thats online
damned if i can find it

[Maffoo]

hhaaaaaa i have found the honda common service manual !

woot

[xwhatsit]

I found that Common Service Manual a bit useless. Trying to turn up a CB250N manual, but surprisingly having little luck. Send Magua a PM, I think I might've seen him post about having a manual once.

[Maffoo]

Ok
i have a reoplacement cam
i have oil
i need to know just two things
how to align the cam to the crank & how tight to torque the head down

im gonna ask in the appropriatte forum on here :D

[xwhatsit]

Aligning the cam to the crank should be easy. You just get the engine at TDC on the compression stroke -- there should be an inspection plug you unscrew that will show you index marks on the flywheel to get there. Usually a `T' mark on the flywheel rim. Then the camshaft, once it's bolted up to the cam sprocket, there will be a pair of index marks on the sprocket as well, or something like that. Align these with the gasket face, and you're all done. Slightly complicated by the fact it's a twin, but they've got index marks for a reason.

I'd troll around for a manual, as that'll be the biggest help. Or go down to your local library and search for the manual -- Haynes or Clymer -- they often have them there. Probably won't be able to borrow it, so just photocopy the appropriate bits.

[Maffoo]

I posteda thread in engine maintenance & got everything i need from magua :D:D:D

im just gonna print it out & go finish it
i have the head sitting on, i got out the piece that went into the engine
also, thankfully because it was a clean break, theres no shit in the engine :D

i also went out & bought a torque wrench today :D

[xwhatsit]

Feck you're a lucky bastage :D

[Maffoo]

ahh i know, but i was due some luck :D

its finished BTW, about an hour ago
it run... i think i need to reset my exhaust valve clearnaces though,... bit noisy
will take it for a spin later on :)

thanks for alll your help guys :rockon: