Topic: CB500K restoration and re-styling. RED FRAME

[Lorbaez]

Hi boys,

I'm really new in this world. I've been rinding modern bikes since 20 years ago, most of them Honda. one year ago I decided to buy a CB500K in very good condition.

[Lorbaez]

Riding is OK even considering that the bike is one year older than me. I enjoy riding it and I still can go faster than some other with ultra modern bike. Its funny to see their face when you overtake them,je je.

Last november I noticed an oil leakage from the oil pan, I removed it to change oil seal but I found this into the oil pan.

[Lorbaez]

This was the starting point of this project

[LesterPiglet]

What is it? 3rd gear? I had 3rd go on mine and heard it's a common fault.

[Lorbaez]

First step was to remove the engine from the frame

[Lorbaez]

This is the owner of broken part

[Lorbaez]

I found 2 parts in the oil pan but just 5th gear broken. the other part belongs to 3rd gear but in my bike it is perfect.

I asume that previous owner repaired it before otherwise I do not know how this part arrived into the engine.

In any case it is a very good oportunity to make a complete restoration. Mounted into the frame engine seems very clean but once you remove it you can see that it is not.

[Lorbaez]

What is it? 3rd gear? I had 3rd go on mine and heard it's a common fault.

The Smallest is part of 3rd gear but mines is OK I don't know were it comes from. What is rare for me is that gearbox works fine even with one gear broken. Once I disasembled the engine I saw that bearings were really bad. This was noticeable while riding, specially difficult engagement of clutch when starting in hot condition due the freeplay of mainshaft on the bearing.

[Lorbaez]

What is your opinion about white exhaust valves? specially number 1 and 2. Maybe ignition out of point?

[Lorbaez]

Maybe the coil is not perfect, know I understand why exhasut 1 and 3 were blue while 2 and 4 were OK.

[lucky]

Rinding is OK even considering that the bike is one year older than me. I enjoy rinding and I still can go faster than some other with ultra modern bike. Its funny to see their face when you overtake them,je je.

Last november i noticed an oil leakage from the oil pan, I removed it to change oil seal but I found this into the oil pan.

That bottom piece is a shifting dog.
The top part is a part of the shifting drum I believe.

Not good.

[lucky]

What is your opinion about white exhaust valves? specially number 1 and 2. Maybe ignition out of point?

That is a normal look for used exhaust valves.

[lucky]

When you see people downshift a motorcycle without revving the throttle a little first then you hear the transmission make a loud clunk that is HOW motorcycle transmissions break.

I have seen this before  when a motorcycle rider will be coming to a stop and just keeps stomping on the gear shift lever repeatedly to get down to first gear without revving the engine between shifts.

A motorcycle trans does not have syncros like a car. A motorcycle only has 3 or four dogs on the gear that must match up and fit into the holes on the gear next to it.
The gear must be slowed down to match up correctly with out clunking into each other while it is being pushed by the shifting fork.

I would bet if the gear has a broken dog that the shift forks could have turned blue from overheating ,and be bent also.

[Lorbaez]

That bottom piece is a shifting dog.
The top part is a part of the shifting drum I believe.
[/quote]

As you can see top part is from 5th gear.

[Lorbaez]

Shift forks are OK, no blue color and within spec.

[Lorbaez]

Today I show you a before and after pictures of the cylinder head. Just machined to clean it and new valve seals. Here in Barcelona there are good professionals for this king of job.

[Lorbaez]

Upper part of valves are also machined. During the use, the contact of the bolt makes a crate in the midle of the valve that makes difficult to get proper valve clearance. Machining it you get a perfect flat surface that helps you.

[LesterPiglet]

It looks to me as though quite a lot has been milled from the cylinder head, this will affect compression. Do you know how much was machined? What will the comp ratio be?

[Lorbaez]

It looks to me as though quite a lot has been milled from the cylinder head, this will affect compression. Do you know how much was machined? What will the comp ratio be?

It is grind only 0.1mm by machining roughness 8S. Increase of comp ration It is not noticeable, theoretically it is  9.25/1 or less. I don not expect by troubles on it.

[Lorbaez]

This bike was restored 10 years ago, but each part that I check reconfirms me that this restoration was not properly done. Since I'm not confident on that I measured cylinders. They were not ovalized but diameter were to big compared with the pistons installed, the piston ring end gap were out of spec in 4 cylinders (more than 0.5mm). I asume that these cylinders were improperly machined in the past.

[Lorbaez]

These are the cylinders once machined, one more time I'm really happy with the job done.

[Lorbaez]

Once cylinder and cylinderhead is OK it's time to clean all the engine.

[Lorbaez]

I decided to sandblast all the engine, but I don't pint it.
Do you have experience with non pinted crankcase?
I asume that colour will become dark after some time and I know that this finish will need all my care to mantain it in perfect condition but I love colour and finish of "nude" cast.

[Tews19]

Looking good. You seem to moving pretty fast.

[Lorbaez]

Looking good. You seem to moving pretty fast.

Thanks Tews.

To be honest some job is already done, I started this project last December. But I decided to share with all of you one week ago.