Bead Blasting concerns

[Gcraay]

This may be a dumb question, but I'm looking to bead blast my engine during my bike build and have a question. Is there any parts of the cylinder and case I shouldn't blast? I understand that I should block off any blind holes, but what about the inner chambers. The piston sleeves will be blocked off, but some guys tape off the valve chamber. Why would I want to do this, mine look pretty dirty, it is a 75 after all.

 

[5twins]

You DO NOT want to blast any internal surfaces. The glass beads will imbed themselves in alloy. They don't all wash out. They do come loose when the engine heats up. Then they run all through your engine destroying things like bearings and cylinder bores.

If you want to blast things like the ports and combustion chamber, use baking soda. That can be washed away.

 

[TwoJugs]

I know many will not agree but I glass bead blast almost everything. I do the combustion chambers but leave the valves in the seats to protect them. The steel domes come out nice. I even blasted a really bad head directly on the seats and the valve face. I did tape off the stems. They were pretty rusted and I wanted to see how they would clean up. They came out great. After a really special session of lapping they went together and ran fine. I have to add that the clean up part is the critical stage. If you are not anal about doing it right you will compoimise the motor. I don't use glass beads inside the cases. Mostly because it is not needed. Stay away from any close tolerance machined aluminum surfaces too. Glass beading has been used a long time to "stress relieve" very important engine internal components, for years. Again the cleanup is the key. I even stuck a hose off my bead nozzle into a rusted steel gas tank. It made the inside look like new. Even though I spent lots of time washing it there were beads left that got wedged into the welded seams. I found out that gas petcocks do not like glass beads to operate smoothly. I ended up installing a set of Purolater pleated paper filters inline. They did fill up with some "fine sand" over time but after a little while it all slowed down. Petcocks smooth again. Filters grabbed the beads and carbs never gave a problem. Fresh filters now and they are not showing any signs of beads.

 

[5twins]

I've found there's no need to do the combustion chambers. They clean up easily and just fine using paint stripper to remove the carbon and then a little chrome polish to finish, like so .....

I don't see the need to get them any cleaner.

 

[Gcraay]

Awesome thanks. I'll do just that.

 

[Mr_Dunev]

Tagged for future

 

[Gcraay]

Thank you for the warning. I wonder what those guys do when they blast car engine blocks.

 

[TwoJugs]

Nice. I need to try the stripper. Does it clean up the rust too?

 

[5twins]

It might, but the chrome polish will do that. I do a little scraping on any small left over chunks of carbon but they're soft from the stripper and come off easily. I also use the little wire wheels in a Dremel for around the valve pockets and seats. In the pics above, the seats are lapped and the ports are done up (casting flaws ground out with a Dremel) - don't expect that from the stripper, lol.

 

[5twins]

The valves are very hard steel so once removed, they can just be wire wheeled clean .....

Since the carbon is really baked on them, even the stripper may not get it all off easily. I do the backsides as well .....

 

[650performance]

In a Ducati race department bulletin in the '70s or '80s the factory advised racers to NEVER glass bead engine internals because the bits were so small that clean up efforts with compressed air, solvents, etc. simply could not get all the residue out. Once the engine was running there was no telling how and where unwanted material would travel and collect.
Instead, they recommended walnut shells, plastic or other forms of "soft" media.
Just sayin'