I'm rebuilding the top end of a 1964 Honda S90 motorcycle engine. The work is nearly done, but I'm concerned about the 40 years of accumulated gunk in the crankcase. I really *don't* want to split the case, but I would like to flush it out somehow.
I'm thinking that before I put the cylinder and head back on, I could fill the case with stoddard solvent, kick it over a few times, drain it and repeat. Before starting the engine, I'll fill it with fresh oil, which I'll replace after 15 minutes or so of running.
Would this be a good idea or will I mess something up?
On Thu, 10 Jun 2004 05:10:01 GMT, Jim Stewart calmly ranted:
Well, how would you like to run solvent-tainted, gunk-ridden oil through your veins? Avoid solvents and leave it to good quality oils with standard additives to do the cleaning. Anything else could cause more trouble than you're ready for. My first automotive job was working for an old shadetree mechanic at a used car lot. Even that idiot wouldn't do a solvent flush any more. It caused him too much work when all of a sudden, 1/4" thick sheets of mud scaled off the crankcase walls, clogged the oil filter, went through the bypass valve, and went straight into the bearings, silt and all. Oops!
If you're truly concerned, split the case and clean everything well before reassembly. Make sure that all solvent-cleaned parts are well dry before reassembly. Bearings hate solvent.
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One trick I know of for cleaning smaller engines is to drain the oil and refill it with diesel oil instead. Then run the engine for five to fifteen minutes, drain, add the regular oil. Any diesel left behind will diffuse into the oil and not cause any trouble. Works great as PM on power equipment, but I don't think it'll clean up 40 years of crap in a motorcycle engine without screwing something up. Probably best to split the case.
That depends on how much gunk is in there. I don't think it's a particularly good idea in either case. If there's a lot of gunk, you'll wind up getting it in places you don't want it, and have an even bigger job on your hands. If there's not much of it, it's a waste of effort.
If you believe the crank case is seriously gunked up, best to open it up, clean it thoroughly and put it back together. If you don't think it's badly gunked up, then just do more frequent oil changes for a while after you get the engine back together. If, attempting this, you discover that your engine needs more work, there's nothing to stop you from going back and doing it right.
Honda step-throughs of that vintage don't have paper element filters. They've got a pickup screen though.
I'd bore-scope the sump and see what's in there.
Jim
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On Thu, 10 Jun 2004 05:10:01 GMT, Jim Stewart vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email
Split it! Not worth anything else. isn't that what "rebuilding" means?
You are rebuilding 40 year old machine, and 90 ccs at that! You are already insane, (although in huge company)! Do it properly! I'm rebuilding the top end of a 1964 Honda
no
Probably.
Look. One afternoon, I and a mate sat down with few beers and installed a new hi-lift camshaft on a Honda CB750. It was good. I have since rebuilt motors and gearbxes of various sizes (no beer). I have NEVER regretted going that extra step. There is both a Zen experience in that rebuild, and the purity of the rebuild, and good old grunt satisfaction of a thorough job well done. (Same result, different culture?)
I will admit that I have a few machines about the place that have not had projects _started_ on them because of the knowledge that Zen takes time! I tell people I am afraid of what I will find when I open them up. but the truth is that I am afraid of what I se inside ME that scares me.
Sometimes in a workplace you find snot on the wall of the toilet cubicles. You feel "What sort of twisted child would do this?"....the internet seems full of them. It's very sad
Tell me about it. Just split the cases on my dearly beloved old '56 Panhead Harley to investigate troubling sounds from the bottom end. The factory cast in outer bearing races on both case halves had worked loose. Has to be sent out to California to have them bored out, cases heated, races cooled and then pressed in. For two fistfuls of money. And they can't promise that the cases won't crack during the surgery. Shit, shit, shit. Flat ruined my whole month.
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