cb360T cam and piston replacement?

MrTeacher

New Member
Fouling plugs and low compression led me to do a top end tear down. Inspection of the following pics shows issues. piston and head had some object flying around and deforming them. The other piston looks great and the walls all look and feel good according to the fingernail test. Should I replace the piston pictured or just clean it up?
Also, the cam is definitely worn, see pic. Where do I send the cam and rockers to get resurfaced? How much should that cost? I have all winter to get the project back together.

My HS shop students are doing this project so it's gonna be fun!
 

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irk miller

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Piston and rockers look trashed. I would swap out that cam too. The second lobe in the pick looks gone, ie. worn at an angle.
 

irk miller

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Common Motor refurbished cams and rockers, but their site currently lists the service as unavailable. I'd message them and see what's up. Super great guys to work with, so worth a call regardless.
 

teazer

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Megacycle cams can rebuild the cam and rocker arms, but they are not cheap.

The question is what will the bike be used for after it's rebuilt? If it's going to be ridden hard or regularly, the cam and rockers need to be really good. If the plan is to improve performance, get a decent cam grind, but if it's only going to do a few miles and infrequently, I'd ask on this forum in the WTB section to see if someone has a stock cam in better condition. There's a few CB360 owners on here.

And failing that, hope that Irk comes back with good news about his connection.

CB360s often suffereed from cam problems and frequently also damaged the bearing surfaces in the head and rocker box, but yours look OK from what we can see.
 

irk miller

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I'd get the $30 camshaft in good shape that's for sale on Ebay and run that (here). There's a few NOS rockers and rocker assemblies for sale, too. Then, ride a life of frequent oil changes and never idling on the side stand.
 

MrTeacher

New Member
So I have a pretty good cam from ebay now. I need new rockers, probably just gonna ebay a decent assembly for that too. Looking at my current rocker assembly, the springs on the rocker shaft seem to just ride on the cover and produce a binding feel when I move the rocker. Is that normal? Feels like a metal on metal scratching situation where the spring meets the cover.
I also am gonna replace 1 valve and 1 valve adjuster that showed pitting.

I found a rings and engine gasket kit on ebay for $84 from company called 4 into 1, seems like a good deal.
 

ridesolo

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I have a decent cylinder and stock pistons for a 360 laying around. I used a different cylinder when I did the 378 conversion. They are yours for the cost of postage in a USPS Flat Rate Box if you want them.
 

MrTeacher

New Member
I’d take the piston if you’re willing. My cylinders look good but something hammered the top of one of my pistons.
 

ridesolo

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I’d take the piston if you’re willing. My cylinders look good but something hammered the top of one of my pistons.
I'll make up a little package of both pistons (would rather keep them together and it won't hurt you to have an extra) give me your zip code and I'll get ya a cost.
 

ridesolo

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OK, Boyd... rainy day here so I'll probably be spending some time loafing in the shop. I'll get 'em down and pack 'em up.
 

MrTeacher

New Member
I have all my parts to start putting this thing back together. But... with my new bore gage I checked both my pistons and at the very top they are .001" outside of the service limit measured front to back. 1/2" down into the cylinder I am right at the service limit spec of 2.6417" . What am I to expect for compression if I use standard piston and rings?
I'd rather not have to get it machined and buy oversize stuff. I'm not building this to be a hot rod, just a reliable running machine.
My previous compression maxed out at 100psi, but I think most of that was due to worn out camshaft.
 

irk miller

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Best you can do is hone it, put it together and test. Piston slap can become a factor as well, though.
 

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