cb500t – engine rebuild – Part 1

2021 update – click here. Below is deprecated info…

It looks like I’m not putting a 450 head on the 500t cylinders.
Everything on the 500t is in way better condition so I’m going with it.

Here is the 450 with the 500t engine in it. So long semi-stock bike…
See ya soon when you’re not as lame.

Rip all the shit off it.

Get the engine top end apart.

The 500t combustion chambers are in way better shape then the 450’s were.

Cam followers are worn a normal amount I suppose, but they’re definitely not dished inward like the 450’s were. See the 450’s here. I’m not sure if I have to fuck with these? Seem okay I guess.

The cam has a tiny bit of pitting on the lobes, but it’s pitted inward and overall seems smooth. If the cam followers are smooth and not dished inward, I’m guessing the cams are fine too?

Valve seats look decent. I’ve never lapped valves before, so that should be interesting. I’m going to make a post about it. Hang tight on that one.

Valve seals out…

So far everything has gone smoothly except the valve seal removal, which… I might have a problem here. The picture above is after the valve seal removal. I practiced removing the seals on my extra 450 head, and they came out super easy. piece of cake. So… then I went to do it on the 500t head, which is the head I actually plan on using, and they would not come the fuck out. WTF. Took forever. Seemed like they were glued on there?

Looks like I nicked the top of the bronze valve guides. Fuckkkk. I looked closely with a flashlight and the inside looks smooth. The concern is that the valve going up and down a million times on something that may not be perfectly smooth could put a groove line on the valve and then put wear on the rubber seal, and then allow oil blow by into the combustion chamber, then I’ll throw the bike off a cliff 3 months from now, or do the rebuild all over again.

So… I’m not sure what to do.

Thoughts… Ricky? Jason?

Here is what I’m thinking…

I don’t know if it is bad enough where anything would be affected on the valve operation. The inside looks smooth. I inserted the valve and it feels smooth going up and down. I could run some 2000 grit sandpaper on the inside of the guide to clear any burs (if there are any). Not sure if that’s a good idea though. The guide is bronze right? and valve is steel. Bronze is way softer than steel right? So I don’t see, even if there was a hypothetical bur, I don’t see how it would score the valve. Seems the valve would just smooth it out and it’d be fine?

Not sure if I want to have new valve guides pressed in because i’d almost certainly have to get the valve seats re-cut. I think…

Below see the seal cap getting damaging while removing the seals. I have extras of these from my other head and they’re perfect. The only concern is the guides.


The engine build is going okay so far.

Bike should be pretty quick when I’m done with it. Or blow the fuck up. We’ll see…

6 responses to “cb500t – engine rebuild – Part 1”

  1. […] and I think in the final part, there is a mention of the pros and cons of such an undertaking cb500t ? engine rebuild ? Part 1 – Chin on the Tank ? Vintage Motorcycle Enthusiasts in Philadelphia Reply With […]

  2. Eric Harris says:

    Hey Ed! I’ve got a 1975 Honda CB500t and I was hoping you could give me a little advice. I’m planning on breaking the bike apart to repaint it and turn it into a cafe racer. The guy I bought it from supposedly says that this bike has sat in a shipping container (with a ton of other classic motorcycles) for over 30 years. He said the bike was only ridden for 3,000 miles before it sat for that long (but the odometer is broken so I’m not totally sure if that’s true or not). The bike is in great shape other than the original tires being dry rotted (the tread on them is hardly worn). It would run but the fuel line was dry-rotted so it was having trouble accelerating due to lack of gas flow. It had a little bit of white smoke that I’m assuming is due to the fact that it sat for so long. My fear is that the seals/gaskets are brittle and could go bad at any time. I was wondering if I should go ahead and break down the engine and replace all of the seals/gaskets since I’m already planning on removing the engine to paint it. What is your recommendation? And if you do recommend rebuilding the engine, what rebuild kit would you suggest?

  3. Ed says:

    I recommend getting the bike running without opening up the engine at all.
    Once you’ve ridden it a bunch then determine what to do next.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

From Past

Published - Sep 25, 2016

Nesco vintage MX track

It’s coming up in 4 weeks.  If you remember a post I made last year, this nesco event was pretty awesome. You get to ride your dirt bike on the race track and it was pretty loose with pretty much no rules. https://www.chinonthetank.com/2015/10/nesco-vintage-dirt-bike-track/ I’m definitely going again this year. A month from now. Who’s coming […]