[akempter]

Morning all, I picked up a basket case 1976 CB500T as a project and I’m wondering if it’s too far gone.

I pulled the oil filter just to see how much goo had accumulated over the decades, and found a serious amount of glitter in there. Absolutely caked in metal flakes. I tested it and it was magnetic. So I pulled the top end apart and found it had eaten The upper timing chain guide bearing. The metal seems to have gone through every passage way and acted as a sort of grit to wear everything else down.

The pistons and cylinders look great, and the lower end seems to be tight. Of course it’s all going to come apart anyway.

My question is, in the opinion of the experienced members among us. Do you think it can be saved? One of the cam bearings is significantly worn, and I’m not sure it’s even possible to locate those parts anymore. The rockers and the Cams appear to be worn as well. I’m thinking this is one of the sources of the iron metal flakes.

Thanks all

 

[ancientdad]

You can still find cam bearing caps. That one looks like the tach side from what I can see in the picture. David Silver Spares has many 450/500T parts still, and you have cmsnl.com as a last resort (higher prices sometimes, higher shipping all the time). Many top end parts from the 450 will fit. Can't say I've personally seen a guide sprocket as bad as that one, good used ones are out there.

https://www.davidsilverspares.com/parts/by-part-number/partnumber_1879/

#2 in price list here

https://www.cmsnl.com/honda-cb500t-twin-dohc-1975-usa_model463/partslist/E++01.html#.XHLurKJKi00

The cams might be repairable, Delta Cams does nice work and can build up and machine your followers too if necessary. More pictures of the parts in question would help us

Mods need to move this to the DOHC 450/500T section

 

[tbpmusic]

Luckily for you the top end is the same as a 450, except for the exhaust side cam cover thingie.
The cam bearing in your photo is toast.
There are still parts (even new) around for 450's, so you should be ok (albeit a lot more broke).
I have seen cam rollers self-destruct like that - cam chain got loose most likely (be sure to replace it) , I've seen them grind through all the way and have oil leaking out all over the place.

 

[pemdoc65]

I've bought quite a few parts from this guy, and they've all been in good shape.
https://www.ebay.com/itm/1975-Honda...h=item3fbb045669:g:HrIAAOSwSk9cbv9I:rk:3:pf:0

 

[J-T]

Moved to DOHC engine section.

 

[ancientdad]

I've bought quite a few parts from this guy, and they've all been in good shape.
https://www.ebay.com/itm/1975-Honda...h=item3fbb045669:g:HrIAAOSwSk9cbv9I:rk:3:pf:0

There you go akempter, most of the parts you need right there.

 

[450roo]

I mean no disrespect when I say there is great satisfaction in raising machines from the dead.
New parts are expensive and you are putting them in a used motor made up of used parts. If you do your shopping prudently you will be surprised how little it will cost to get it going.
Parts on ebay and other sources are constantly changing be prepared to wait a week or two if you are on a budget.
Good Luck!

 

[oupa]

I fully understand the question, "how much is too much?" The truth however, is that is completely up to you. We all have different bike budgets. Time constraints. Patience, etc... About all you can do is try to assess what you need to make it what you want it to be and try to get some handle on what that's going to cost, then make your own assessment on worth.

Not much help I know, but we've all been there. Depending on what you already have in it, together with space considerations, maybe if it's too much now, next year will present some different options. Maybe a good donor motor will turn up in a wrecked frame. A cheap head. Who knows. The engine I'm working on right now was precisely such a situation. I've even cannibalized parts off it. Now, thanks to a complete head & cam chest coming along at an unbelievable price ($20! ) I'm hoping to make it live again. It's a hobby. Hobbies by definition have value only to the practitioner.

 

[akempter]

Guys thanks so much for the replies!

So a couple posts asked for some measurements, and I’ve gone out and done some work with my micrometer.

Cam journals 21.7 min spec from FSM 21.9

Camshaft bearing 21.8 min spec 22.05

Follower ID 10.0 min spec 10.28

Follower shaft 10.1 service limit 10.1

These aren’t a compete set of measurements, since this is my first engine tear down I don’t have the proper micrometer to measure a couple things, or at least don’t know how. I can’t check the camshaft for bend. And I don’t know how to check the height of each cam, the FSM says the service limit is 4.65 and I’m not sure what that means. It’s not the outside diameter of the cam lobe, that 40.7. I’m thinking I need one that has a plunge depth on the end.

But back to the original question, everyone is totally right. I need to examine what this project is worth to me personally. It seems that like most things given enough time and money nearly everything is possible.

So I feel the best way forward is probably to just get a solid idea of what It needs to get running, make a budget and keep an eye out for a bargain.

Photos are of the cam followers, the FSM doesn’t list a spec for them, but they’re pretty dished out. So I’d have to get them built up. It appears they’ve been welded and ground once already.

Thanks all

 

[ancientdad]

These engines have somewhat marginal oiling to the top end and the heat on the exhaust side usually makes those followers and/or cam lobes wear sooner. In theory, as long as normal oil flow is present, things shouldn't wear excessively or the followers get dished. That said, good maintenance and warm-up habits can make a big difference there - keeping it full of clean, proper oil and taking the time to allow oil flow to get to the top end when cold, which can take as much as a minute and a half to two minutes and should be done at the lowest revs possible to avoid running through the oil film left on the cam lobes and followers, really helps prolong the life of the parts. You won't likely have any runout on the cams, but checking the bearing surfaces for excess wear will be important, especially on the points side - excess wear there will affect your points gaps and the accuracy of the timing as a result. As you already know, bearing caps are available both new and used, but followers are hard to find except used and many times will be no better than yours, or only marginally. they can be repaired of course, but did you check into that complete used head? If in good condition, that would save you some money

 

[tbpmusic]

Those followers are crap - probably means your cams are trashed too.

 

[lceecitee]

I talked about my 450 experience with the frozen piston in previous question in today's forum. I totally agree about the poor oil flow the the top end on start up, my motor had serious wear up top. After an expensive top end rebuild I decided to try and cure the oil lag on start up. I put an electric oil pump on it. It pumps oil into the right and side camshaft bearings. Probably a bit excessive but actually pretty easy to do. The idea is to run the pump for a minute or two before starting. That way everything up top is flooded with oil before the engine starts.