Surface Finish Requirements.

[xXx Octane xXx]

What kind of surface finish is required on the mating surfaces of the crank case halves?

Thanks in advance,

Eric.

 

[douglee25]

I've always just cleaned the surfaces up with an emery cloth or a razor blade. Any slight imperfections are made up with the adhesive.

Doug

 

[Sanford]

What kind of surface finish is required on the mating surfaces of the crank case halves?

Here is how I do these type of "critical" surfaces...

Glue a full sheet of 600 grit wet/dry sandpaper on a very thick piece of glass. Make sure there are no uneven spots of glue and paper is very flat. Then coat sandpaper with WD-40 and lap mating surface(s) until area is uniform. If there are high spots, keep lapping (I am more worried about high spots then lows). However, don't over do an area and keep the time you spend lapping an area consistent on all other areas.

I have a VERY thick (heavy) piece of Silestone that I use for this purpose or for other mic work. Glass works just as well as long as its at least 1/2" thick.

Don't forget to use 1211 on the case halfs.

 

[romack991]

Sandpaper is not good to use across a sealing surface. The silica can leave very fine, sharp scratches across the sealing area and the seal can not fill those areas and there will be a leak point. This may not be as big of issue when using a liquid/gel sealant.

 

[WFO Speedracer]

I believe that Yamabond 4 or threebond will take seal up to about .004",after that you got problems,personally I would want the surfaces a lot closer than that.

 

[Sanford]

Sandpaper is not good to use across a sealing surface. The silica can leave very fine, sharp scratches across the sealing area and the seal can not fill those areas and there will be a leak point. This may not be as big of issue when using a liquid/gel sealant.

Naaaa...

When using such v.fine grit like 600 (and WD-40 as a lubricant) on metal you get as close polished as you can get. Besides, all cases need to be sealed with sealant and if a heavy viscus sealant like 1211 can't seal it then nothing will.

This method is proven and is better than taking a chance to nick the machined areas with a razor blade or gauge with a ROLOC scotchbrite pad.

 

[#ZERO]

Just wipe it down with acetone to remove any oil residue and apply 1211

 

[romack991]

Naaaa...

When using such v.fine grit like 600 (and WD-40 as a lubricant) on metal you get as close polished as you can get. Besides, all cases need to be sealed with sealant and if a heavy viscus sealant like 1211 can't seal it then nothing will.

This method is proven and is better than taking a chance to nick the machined areas with a razor blade or gauge with a ROLOC scotchbrite pad.

Like I said this maybe ok on sealing surfaces when using liquid/rtv type sealants.

Just thought I'd throw out the warning. I design customs seals for a living. I've seen where a customer used sandpaper to polish up a groove to make it nice and pretty and it creates sharp tiny scratches across the surface. Typical rubber seals can't fill that sharp void and you get micro leakage.

 

[ANT]

scotch brite and some wd-40 but dont press to hard. clean it off with parts cleaner, let it dry. I use the flange sealant that they use from the factory, an equivalant that loctite makes is called 512 it's red stuff. Bolt it up and let it set up...my motor is still runin strong.