dont let this happen

[davepainter]

Well found out what the fault with the float bowls was, a snapped camshaft-OUCH??
carefull buying on e-bay to be honest the guy i bought this off probably thought he had cleaned thoroughly just goes to show
basically something blocked the oil feed to cylinder 3+4 camshaft.
i,ve yet to inspect the head and VALVES scary.
within 2 hours i found a mint cam carriers and followers for my 76 k6 inc postage from good old USA for

[steff750]

  4 times in 30 years, yes been there done that and had the t-shirt.I'm surprised you did not hear the camshaft seizing up, they make one hell of a squeal before they give up the ghost  (a sound i will never forget or want to hear again) mine snapped as i tried to get home i was only about two miles away so limped home on two cylinders,the problem in my case was stripped threads on the cam cap bolts and a bit of crap welded its self too the camshaft, ,everything under the rocker box had worked loose from previous owners rebuild it had run for six years so cant be to harsh on him ,the head has since been heli-coiled so better than before , you will learn from this ,so don't feel to peeved,i think it has happened to quite a few of us .i would say most likely bent valves aswell in my case anyway.just make sure them oiljets are clear and be ultra clean on the rebuild i always spin my engines over on the bench with the battery connected to the starter motor and check for plenty of oil on the camshaft, before installing the engine,this used to be a bit of p*ss years ago, with plenty of old chops about for spares and gasket sets only costing twenty quid ,just swap heads or even engines and off you go not any more lol  

[UK Pete]

Yes it does seem to be a common problem, kind of makes you feel paranoid for a while after a rebuild and riding for the first 500 miles or so
The problem after something like this happening is all the ground up bits of metal that have managed to circulate around the rest of the engine, i would only be happy to run it after a full strip and clean out of entire engine after that
Pete

[hairygit]

Steff, the odd thing was that the side of the cam with no oil supply was for cylinders 3+4, which were the only 2 running! The cam snapped leaving the part above cylinders 1+2 not turning, but the oil supply to them looked okay!

[davepainter]

Well spotted,its going to be interesting ? to see which valves if any have been affected
my geuss would be that up untill the exact moment the cam snapped 3+4 were firing to allow bike to run?
however ground zero day at 160 miles on clock 12-9-2011  cylinders 1+2 on inspection as suggested by yourself were found to have NO play in tappet arms,---
 The last time i rode the bike with all 4 cylinders running was 29-8-2011.at 160 miles,as you say odd that the undamaged looking side 1+2 was the side i,ve had constant stop start, wont run then ok then not.
when i had the bike delivered with 8 miles on the clock,from new engine build and start, it did,nt run on 1+2 the FIRST time i started her i had to ring the guy i bought the bike from and asked him what main jets he was running, i ASSUMED it needed bigger jets i ordered and tried 120s then 110s before putting the 105s back in which were the ones in the bike when it was delivered!
 So mr watson for some reason all the time (160) miles that the cam damaged side 3+4 was disintergrating and turning into molten metal,
the bike covered at least 140 good miles running on all 4.
 the 5 or 6 times i went out and rode 20-30 miles at a time good --then next time i went to use her she WOUld,NT fire on 1+2
Like you say its strange all the damage was being done to 3+4 .
prediction time i reckon when head comes off i,ve bent valves on 1+2--caused at the exact moment the cam snapped!!!!






=

[hairygit]

Sadly at least 1 bent valve is a certainty maybe more as the cam may have still moved at odd times due to the fact of the way it broke, leaving a rough edge which could occasionally move the cam a fraction and let other valves hit the pistons One thing I will suggest though, when you have rebuilt the engine, as it's in a chop frame, leave the rocker cover off and leave the spark plugs out and wind it over on the starter  several times to make certain that oil is reaching the top end as it should, then fit the rocker cover and spark plugs! (something we have to do OUT of the frame on a standard bike ) 

[Bryanj]

Used to see this semi regularly in the past when a person not used to Honda's would re-build an engine and not be carefull enough to claen out bits of gasket or use excess silicone.

Also 20/50 is too thick in the UK

[davepainter]

Here is the cam and carrier-i hope it shows pic? i bought on e-bay from the states

[SteveD CB500K0]

Love the way they get "Sandcast" into every CB750 listing...

[Hinomaru]

CB750K cam cap bolts do work loose and this has happened way too many times, even with stock engines. This problem becomes worse when running aftermarket valve springs and cams. One solution is a modified cam cover which adds extra support to the cam caps to prevent them from coming loose and dropping oil pressure. Old modification from the 1970

[Spitfire]

Nasty, saw a lot of them back in the olden days, snapped cams seemed to be very common, the cam and holders from the states look like a bargain as the last time I looked just one new cam holder from CMS was

[davepainter]

Hi  Den thanks message ref spares prices, on that note i,ve just bought a very clean f2 to use as an engine doner shame to split a nice bike BUT i will run f2 for a while set timing balance carbs etc check she runs well then at least i can USE chop. with what i sell rolling chassis f2 for it will work out much cheaper than a ground up engine rebuild.If so then i can also sell whats left of k6 engine along with as new cam and carriers.
i will post pictures of f2 when she arrives fingers crossed!
as uk pete noticed f1 f2 prices are rising they dont make them anymore? look on e-bay at moment mint 1978 f2 in black gorgeous.
best wishes dave
ps some help needed advice as to fitting f2 lump to k6 chokes different etc electrics?

[Bryanj]

With the problems F2's have with valve guides i would stick with the engine rebuild mate

[hairygit]

Use the F2 carbs with it, electrics are the same for your needs, the main problem you will have is the exhaust on your chop (K6 engine) wont fit straight on (different at the exhaust port mounting)

[K2-K6]

At least you'll have enough room to get the head off easily to fix the guides!

Thought the K6 exhaust stubs may fit to F2 head in place of standard F2 studs and header combination but you'd have to check it through for yourself.

I'd say the K1-6 and F1 motors are much better for cruising than F2 if that affects your decision.

F2 runs quite lean as standard and gets going a bit as you open throttles (additional fuel pumped as you turn the throttle) but you may not like that feel if you just want to mooch around.