CB72 or CB77 crank ?

[LOUD MOUSE]

Let us know what you find when you take it apart. ....lm

No I did'nt.
in fact I bought the rods with rollers ;they were sold on ebay to fit CB 72,CB77.
I asked a specialist to replace rods and to balance the crank .
I must tell you that after riding ,the motor suddenly blocked .after ten minutes ,it started again freely but noisier... I am afraid the rod play is due to this incident..

[G-Man]

It sounds like some dirt or debris may have stopped the flow of oil to one or both bearings..

Please let us know what happens.

G

[cliquet]

ok Guys
thanks for your interest and help ;see you later for news;
JFF

[cliquet]

hi every body , and G.man and loud mouse... 8 months later...

After opening motor and checking oil circuit and pump...nothing seems to be wrong.however I changed pump packing and gear, rotating filter shaft and decided to try a great experience :
bought a new crank assy (but CL72 ,360°) and transform it to 180° to fit my CB72 ;a specialist did it ;no real problem except need to adjust the starter roller plate thickness (rotor side).
the crank works great without any vibration or noise . (my first problem is over) but my motor runs bad...no powerful at starting (cold motor) ,difficult to increase RPM .
compression both cylinders : 92 PSI .....I red somewhere that standard is 170 PSI!!
I can't understand cause my camshaft is well attached (punch mark, T mark, parrallel sprocket ect...)
Checking timing valves : closing angle intake is 55° after lower dead point(instead of 30°?)
That seems to mean that whe loose 25° of compression stroke compared to standards.
I red somewhere that after 1964, Honda had changed compression ratio (8,5 to 1 instead of 9,5 to1) ;my motor is a 1965 .
an other possibility could be my camshaft is not correct ( I bought it as a CB72/CB77 but from thailand.......)
can you give me your feel .thanks a lot
regards

[Tim Miller]

While reassembling a crankshaft not only is it important to maintain exactly 180 degree's you must also clock cam gear correctly. This could be your problem.


Tim

hi every body , and G.man and loud mouse... 8 months later...

After opening motor and checking oil circuit and pump...nothing seems to be wrong.however I changed pump packing and gear, rotating filter shaft and decided to try a great experience :
bought a new crank assy (but CL72 ,360°) and transform it to 180° to fit my CB72 ;a specialist did it ;no real problem except need to adjust the starter roller plate thickness (rotor side).
the crank works great without any vibration or noise . (my first problem is over) but my motor runs bad...no powerful at starting (cold motor) ,difficult to increase RPM .
compression both cylinders : 92 PSI .....I red somewhere that standard is 170 PSI!!
I can't understand cause my camshaft is well attached (punch mark, T mark, parrallel sprocket ect...)
Checking timing valves : closing angle intake is 55° after lower dead point(instead of 30°?)
That seems to mean that whe loose 25° of compression stroke compared to standards.
I red somewhere that after 1964, Honda had changed compression ratio (8,5 to 1 instead of 9,5 to1) ;my motor is a 1965 .
an other possibility could be my camshaft is not correct ( I bought it as a CB72/CB77 but from thailand.......)
can you give me your feel .thanks a lot
regards

[cknight]

If you used the marks on the rotor for cam timing, and it's 25 degrees retarded, the ignition timing is also off. Retarded cam timing will reduce the cranking compression as you've experienced. It's time to verify the Top Dead Center markings on the rotor. This can be accomplished with the cylinder head off, or make a TDC stop that will screw into the spark plug hole. Then, most likely, re-mark all the timing marks accordingly, then re-time the camshaft. Regards, Chase

[cliquet]

thanks for your answers
Tim you're right but no"punch mark" on the cam gear (crank side) so the maximum error is half tooth on the cam gear ;do you think that can explain the missing 25°compression on the rotor marks?.

Chase, the ignition timing is ok (checked with stroboscop on the rotor marks)and screws fixing the points plate are in the range ;as you tell me, perhaps a wrong mark "T" on the rotor.... I am going to check it.

Do you know the normal compression (in PSI) for CB72 ?I remember (but not sure ) that it is 10,5Kgs/cm²?
Cheers
Cliquet from Paris