Topic: 1972 cb750 k2 rocker box interchangeability

[Odin]

Hi

Im rebuilding the engine in my 72 k2 750 and just discovered the rocker box (not sure if thats the proper name for it) has totally worn out camshaft bearings/guides or whatever to call it. As far as i can tell i have to change the entire rocker housing. The cam was also totally wore out and i bought a new one so i dont know how i missed the housing bearings.

I wonder if someone can tell me if these fit from other years and k models, like k1,k3 etc? the rocker arms and shafts is in good condition, so im hoping to get the housing only and just swap the rest over.

Thanks in advance for ur help

[bamacb]

Yes they will but you better check more as something caused the damage, as in lack of oil. If the cam and bearings are gone I can't imagine the rocker arms are good. Start by checking the oil orifices in the head and go from there.

[seanbarney41]

there are some differences over the years in the rocker shafts and how they are retained, but all years can be made interchangeable

[Odin]

Hi again

Thanks for your answers.

So just so i understand correct, getting the rocker housing from a k1 for example is no problem?

The rockerarms was also damaged but i saw this a long time ago so i have replaced them, basicly it took out the rockers, camshaft and then the rocker housing-bearings.

I have tried to inspect the oil channels as good as i can, blew air threw them and so on and everything seems open and good. However i wonder if theres any known problemspots i should take particular care to inspect?

Im also gonna take the oilpump apart for cleaning and inspection, are these pumps good or are they failure prone?

Could the camshaft and such get messed up from for example low/little oil in the engine and/or poor oil?

im also a little confused by something else. In the gasket set i bought, theres valve stem seals, in one bag theres "normal" looking valvestem seals and also some bigger rubber rings or whatever to call it. I never seen those kinda rubber rings before and i dont understand how they will go on my bike, so i assume these stems for an older or newer engine, or am i missunderstanding something obvious?

Thanks again for all help

[seanbarney41]

Yes indeed...make sure the oil jets are clear.  There are 4 indentations underneath the cam towers.  The 2 inside (one for each cam tower) contain the oil jets.  These are easily plugged by debris.  The outside 2 are blanked off but should contain a very small o-ring, same as the o-rings enclosing the oil jets.  Missing o-rings will also cause cam and valve train failures.

[Don R]

 The cam towers come apart in two sets. I prefer to use matched ones, unfortunately a lot of guys on e bay like to split up a set and sell halves. Some guys say it doesn't matter but I'm picky.

[Odin]

Thanks again for your answers.

The rockerhousings i been looking at is a pair, which i also prefer, even tho i guess it doesnt really matter that much.

Im doing a lil bit everyday on the engine and i discover new things as i go, so now i have a diffrent question.

The valvestems, on the inlet the valvestems has grooves for the valvestems seals, the exhaust stems have no grooves and looks a bit diffrent, i would call them pointy on top. Do i then have a head which originally doesnt have exhaust valvestem seals? and if so, how to i go about getting them seals to sit on them, a bit of loctite?

[bryanj]

Fit later valve guides which means having the seats re cut

[Odin]

Oki Thanks

So to make sure, the pointy ends means their not supposed to have valvestemseals?

[bryanj]

Correct, means its an early head.