[PoiPio]

Can I ask has anyone ever actually done a top end strip down. I am still confused as to why two of the bolts are solid and will not undo. The other six are as free as birds. The bolts definitely are not exposed to outside where corrosion could occur.
Actually breaking the bolts would be ok as long as they broke in the middle, if the break just above the crank case that would be a whole lot of trouble.

The is more the steroid jerk. Full on leverage might snap the bolt off. But more a torsional turn on and off so the metal distorts instead. Longer the bar on the ratchet, more torque to twist. Imagine sheering the hex off the bolt and is rounded. This keeps the hex/bolt head in good condition to reuse, or it's drill the bolt head off. Try the torsion load.

 

[Hawkeyefxr]

So confusion does not take over, state which type cm250 you are referring to.

The superdream like solid crank, 6 valve engine, horizontally split, call it the 6 valve engine

Or the non superdream like pressed up crank 4 valve engine vertically split, call that the 4 valve engine.

As you will remember on some hondas, 2 thou was a common ( but not the only ) valve working clearance.

I have no 4 valve cm engine info, even the cb250, the 1990's version, which was a vertical split 4 valve engine. I still may have that sales brochure but will take some finding.

I do have info for the superdream like cm model 6 valve engine.

Removing cylinder head "studs", the long "wasted" cylinder head studs like in a c90 engine that screw into the crankcases, can be problematic. Heating the alloy casing and/or cooling the stud, or bolt for that matter, helps, and sometimes is your only option.

Sonic screwdrivers have not been developed yet, or have they......a tomorrow's world April the first maybe or are they a reality these days....

As a side note, Yam XS250, remember them ? They did have a cam chain "ratcheting" adjustment system, but the engine was far from good, always sounded as if the engine was on the verge of siezing up !

Anyway, which type engine you having head bolts/studs yriuble with, and, which type engine you want cam chain and valve clearance info for ?

Probably better to start new threads perhaps ?

Apologies for the 6 valve statement, it's a 4 valve per piston, why the hell i made a 3 valve per piston i'll never know

 

[DD23]

Do you mean 2 valves per cylinder, so 4 valves in total ?

Pictures please....

 

[PoiPio]

it's a 4 valve per piston

Then that changes valve lash specs. I gave you this engine family's 2v per head spec. New for me then.

1983 Honda CM250C A CAMSHAFT / VALVE | Ron Ayers

Shop online for OEM CAMSHAFT / VALVE parts that fit your 1983 Honda CM250C A, search all our OEM Parts or call at 252-758-3084

www.ronayers.com

 

[Montanabill]

Yes but what type and viscosity of oil should you use? This has to be one of the more confusing threads. Photos of the bike please.

 

[PoiPio]

Funny you should ask about oil types. I've tried to blowup 4 new bikes using 46 year old racing 50w and whatever is around in multi weights. This is a very high performance engine (stock) and I used the oil that came with the bike for its first 600mi, then switched to 2qts of 50w and 2qts [one each ] of 10w40, and 20w50, 10w30, syn or non-syn.

The forever page after page of oil arguments, I wanted to squash an old wives tale flat on its nose. So last oil change, and out of the 4 of the same model, the current bike's oil filter was cut open to [continue] seeing the results. This time I found the most cleanest of filter pleats of those 4 engines.

Home he here at home does not struggle choosing WOT oil to use in his engines. After all it's just distilled light sweet crude base. Oil mixes with oil. Get it?

About the only thing I feel assfactor wise is how thick it feels rolling backwards down the driveway. Then goes away after awhile. Then the shift quality signs off right about its time to change the oil every 3000mi. So that's an average of 36 time for the 4 bikes oil and filters were changed. 72 times the bikes were fed 50.

I rest my light sweet crude's 'cases.'

Signed,
NOLTT (not one likes turtle testing)

 

[DD23]

Oil filter bye pass valve ?

Picture of the bike please Hawkeye or confusion will rule the day.

Pictures please Hawkeye, pretty please Hawkeye...🎅👍