new member, rust in cylinder head
I'll be starting my rebuild soon (CB72), and I'm wondering about valve guide wear. Is this any issue on these bikes? I've no documentation for the mileage of the bike, but it looked all original and speedo as 47000 miles on it - should I expect any particular wear in any of the engine parts at that mileage? I think the guide wear is the only thing I've got no way of measuring, and as the bie has never run in my ownership I've no idea whether it was a smoker or not.
I'm hoping this is going to just be a strip down for the clean up of the cases and then putting back together, but I'll probably find all sorts of horrors once I get into it. Any tips appreciated.
Toast, when you've gone to all the trouble of taking the motor out and tearing it down, I'd say it'd be wise to go through it with a fine tooth comb, mate. Especially at that suspected mileage. Make it a winter project, which is also what I'm doing with mine (30,000 miles shown). Guides are a doddle to drift out with the right tool and a gas torch. And while they're out, it's a cinch to polish the ports too!
Internal chains, lower cam chain roller, bearings, seals, small ends; close inpection of the selector forks, shimming the transmission, kickstart pawl, etc, etc,. It's all that awkward shite that can't be accessed when the motor's in the frame! It's all extra work but you only reap what you sow..... Think about it. Regards, Steve
Yes, I'll be measuring everything while it's apart, but the guides I can't measure, so it'll be best guess judging by wear on the valves themselves. I'd expected to send the head away to get the guides done, not seen anywhere selling them.
Should I be putting new rings in as a matter of course? I've rebuilt loads of RD350 engines, and I normally junk the pistons and get a rebore just as a matter of course, never rebuilt a 4 stroke though so I'll have loads of questions when I get started.
Trawl eBay frequently for pistons & rings, but only after inspecting yours to see if a) there's any deep scoring in the bores and b) what size o/s you currently have. Once again, they're cheap enough -- I got a pair of Art pistons & ring sets, 0.75 o/s, for $70. It's another of those things that's a right pain in the attick if you find that the motor's smokey or slappy (I shouldn't have thought so, but these are prone to seizing if hammered). If there's any sign of alloy on the bores then I'd suspect a past seizure.
Also, once again, if you're going that far then don't spoil the job for a cut corner. Do it right, do it once!
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
