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So my 20B engine is stripped for rebuild and looks good. I have complete new seal kit for it. I have been told I should go over the I inner surface of the housing carefully to remove any high spots that could snag the new tips .. Which seems reasonable as you would home a piston engine. It has been suggested you can do this with a large flat wheel around 150grit on a dremel and carefully go around the surface of the housing keeping the dremel square. I am guessing the coating is very hard but wanted to check for some other feedback on this or other suggestions. Likewise on the side sealing face can I rub over these with a big flat block wrap in say 320-400 grit wet and dry to make sure it is good and clean or is it best to leave this and just scrape and clean thoroughly?
Cheers
Lee
I'm far from an expert but the dremel sounds like a bad idea to me. Especially with 150 grit tip on it. The last thing you want to do is damage the chromed surface.
I'm assuming you are talking about used housings?
If so.... I've rebuilt a few engines and I always sprayed the inside surface down with carb cleaner and used razor blade to scrape off the carbon buildup.
The condition of the housings is the key here. If you have excessive flaking and wear then you will want to consider if the housing is worth re-using.
okay.. cheers. Housing are good nick. Just a couple of tiny score marks right on the edge were the corner seals runs I guess. So just clean and leave alone? I just wanted to knock of any really tiny high spots that might catch and wear the new tips badly? What is usual break in time for just seals and tips? Waht about if I add in new front and rear bearings?
if there isn't any actual flaking or chunks out of the chrome then i wouldn't worry about it.
someone else who is on here everyday giving help and advice also does the service if you choose that route, but everyone seems to have forgotten about them.
Lol! Is that you by chance? Sadly I am in the UK so not really viable. Might consider moving though for a better rotary scene!
what about the side faces too. Scrape clean only or can I give a light rub over with a flat block and some 600 wet n dry or maybe finer?
Cheers
Thanks.. It is more to get the last bit of staining and marks off that cannot quite scrape /scrub. I might see if I can stick some wet n dry to a surface table at work and rub them over that. Which should ensure keeping the surface perfectly flat.
is it worth getting a narrow block and rubbing locally over the spark plug arear to see if there is much of a raised area there and if so carefully just taking that down? I cannot see anything by eye or feel it with my finger.
on the chrome surface or the aluminum? that spot of the housings is usually the narrowest due to thermal expansion so as long as it is flat, i wouldn't worry much about surface coloration. if you mean the chrome, the only item to be concerned about there is horizontal cracking coming from the spark plug holes.
Ot was a bit of both really. Flat/smooth/cleanliness of the side faces by blocking or rubbing o. A surface table. And whether there was any mileage in Locally running a flat block over the chrome face where the plug hole come out in case of a slight bulge around the hole I see people talk about. Looks fine. No visible cracking. Will try and post pictures later.
chrome is an extremely hard metal, but it also wears very slowly(generally). so working any of the chrome surface is at your own risk when doing anything by hand and i don't generally recommend it unless it is just dremeling over some very minor apex seal wounds.
and if using any machine tools on the chrome use the appropriate respirator and ventilated area. chrome dust is highly cancerous.
No worries I will leave alone.. I did not know Chrome was cancerous! Good tip. I look forward to getting that. I rubbed back some chrome wheels a while ago to give them a polish up!
anyway. Here is a pic of how the housings look in general. All three basically the same as you would expect!
they're not in too bad of shape, won't get perfect compression but it shouldn't be **** poor either. but you can see the crown already developed, so they are half through their lifespan.
I thought they looked pretty good to be fair with my limited knowledge.. Not major scores, chips of chatter marks. it's a rebuild after all so you wouldn't expect them to be 100%. Compression was too bad before I pulled it apart. Was more the fact the whole thing was a bit of an unknown and I wanted piece of mind before it broke leading to a more expensive rebuild!
03-06-17, 03:56 PM
