Case damage

[alankelly]

Hi All

Just helping a mate rebuild his AC 250 engine

Got cases back from vapour blasting and got this



We think it’s water damage and thinking maybe fill with a smear of JB weld and neatly and carefully dressed back flat with a flat file, as want to avoid welding and re machining

What does everyone think or leave and use yammabond on the base gaskets

Just not happy leaving as is but feel if I get most of the damage dressed flat and then a small smear of sealant to prevent an air leak all is good and it then not just a bodge job

(Going to leak test anyway once assembled)

Thanks in advance

Best wishes Al

[midlifecrisisrd]

Jeez that's bad, never seen it so widespread before

Looks like corrosion but maybe not helped by a porous cast

The godsend is that it's an air-cooled so separate heads meaning any slight discrepancy will be taken up and they can sit slightly different

Yes, fill the gaps with epoxy of some kind, jb weld is a good choice

I'd use genuine base gaskets so they are not just paper

I'd also use a smear of 3 bond to be safe

Steve

[alankelly]

Thanks Steve

Just spoke to Rob and think plan is to try and get studs out and then either fill with JB and then skim on the mill or a more drastic solution is maybe take off 1-2 mm and then add a spacer plate to replace the removed material

So next stage is try removing the studs and if that is successful can fill and skim or cut back

Best wishes Al

[chrisg]

Feb 8, 2024 19:10:21 GMT 1 alankelly said:

Thanks Steve

Just spoke to Rob and think plan is to try and get studs out and then either fill with JB and then skim on the mill or a more drastic solution is maybe take off 1-2 mm and then add a spacer plate to replace the removed material

So next stage is try removing the studs and if that is successful can fill and skim or cut back

Best wishes Al

personally i would get it skimmed and use a spacer.

[midlifecrisisrd]

The studs would need to come out for either

Milling is the preferred solution if possible

Once the studs are out place a steel rule across and see just how bad it is

If the high points are the original face height epoxy would do as you are just filling the holes

If its eroded across a wide area or too much gone then milling is the only issue

Do you have a tool to remove the studs?

Steve

[jon]

Studs that have been in 40 years have a habit of being seized in my experience.

If it were mine I’d cut the studs down nearer the case and weld a nut with a chamfer on. The heat will help it remove.

Personally I’d drill out some 17mm hex bar and give it a good chamfer to get some extra torque.

I’d also get it machined and use spacers.

An air leak here could be disastrous.

Jon

[alankelly]

Hi all

Ok studs out so at least that’s one less headache

This is the results of the straight edge








Worst area is between barrels

But I think we could mill off 2mm and then add spacers?

Any thoughts welcome

Best wishes Al

[alankelly]

Next question please is can I source 2mm barrel base spacers “off the shelf”

Thanks for all the help so far

Best wishes Al

[donkeychomp]

If you get really stuck with this I have an RD250 engine sulking in the back of the garage.

Alex

[alankelly]

Hi Alex

That’s very kind but going to try a repair first

Love a challenge 😂

Best wishes Al

[midlifecrisisrd]

Are the gaskets not the same pattern as LC

Did Rob not get some made

Steve

[midlifecrisisrd]

Yep

Here

rdlccrazy.proboards.com/thread/60511/4l0-4l1-ac-cylinder-spacers

Steve

[JonW]

Wow, Spacer is my thought as well.

[shaunthe2nd]

Feb 8, 2024 18:02:46 GMT 1 alankelly said:

Hi All

Just helping a mate rebuild his AC 250 engine

Got cases back from vapour blasting and got this



We think it’s water damage and thinking maybe fill with a smear of JB weld and neatly and carefully dressed back flat with a flat file, as want to avoid welding and re machining

What does everyone think or leave and use yammabond on the base gaskets

Just not happy leaving as is but feel if I get most of the damage dressed flat and then a small smear of sealant to prevent an air leak all is good and it then not just a bodge job

(Going to leak test anyway once assembled)

Thanks in advance

Best wishes Al


Ouch, that's bad Alan. How was it before blasting? do you think its the blast process that was the issue?

[alankelly]

Feb 8, 2024 23:32:05 GMT 1 shaunthe2nd said:

Feb 8, 2024 18:02:46 GMT 1 alankelly said:

Hi All

Just helping a mate rebuild his AC 250 engine

Got cases back from vapour blasting and got this



We think it’s water damage and thinking maybe fill with a smear of JB weld and neatly and carefully dressed back flat with a flat file, as want to avoid welding and re machining

What does everyone think or leave and use yammabond on the base gaskets

Just not happy leaving as is but feel if I get most of the damage dressed flat and then a small smear of sealant to prevent an air leak all is good and it then not just a bodge job

(Going to leak test anyway once assembled)

Thanks in advance

Best wishes Al


Ouch, that's bad Alan. How was it before blasting? do you think its the blast process that was the issue?

Hi Shaun

No I am certain the damage was already present as could feel the base gasket face had some imperfections

Trouble is the guy who had supposedly rebuilt the bottom end had just slapped a load of black paint on the complete bottom end including this gasket sealing area

Now spoke to Rob and he is going to see if we can get a 2mm alloy spacer cut then I will machine 2mm off to removed the damage (and if any slight holes are left will feel with JB) then rebuild using the spacer to get barrels back to original heights

[4l04ever]

2mm spacer ordered from laser cutting place :-)

[Tobyjugs]

I don't see any problems with using a spacer. It might come in handy as you can adjust the cylinders to the correct height depending on their condition and state of tune.

A very good sealant to use once you have the correct height etc. and are in the final build process is Loctite 5910. If i ever get a bad leak difficult to cure this is the stuff to use. Just one small problem with this stuff is it can be difficult to part the components when you need to strip them back down. 

[midlifecrisisrd]

My first thought was to use a sealant like that and permanently bond the spacer on

Steve

[Tobyjugs]

Actually when i think about it we use and aluminum gasket material which is made up of lots of thin layers. You fit the component onto the engine measure the clearances then remove the component and peel the layers away until you have reached the correct tolerances. A bit too "over the top" for this sort of repair.

[alankelly]

If it machines and cleans up at 2mm, and I use a 2mm spacer, what’s the thoughts on case sealant between the case and the spacer and then the normal base gasket between the spacer and cylinder (of the correct thickness) to create the correct squish

That way I don’t need to allow for a “lower base gasket” as the case deck height will be as before?

[midlifecrisisrd]

As said that's what I'd do

Permanently bond the spacer on, single gasket, barrel on top
Steve

[4l04ever]

I would use 2 gaskets to allow for any distortion/tolerance to be taken up.

I run 2 base gaskets on my 4L0 with a 1mm spacer plate between them. Just fitted with a smear of grease to aid disassembly.

Leak down tested with no issues.

[4l04ever]

Probably put a 0.4mm or 0.5mm on the bottom and a 0.25mm on the top. Should get close to OEM :-)

[alankelly]

All done and waiting for a 2mm spacer

“Another one lives to fight another day” 😎

[donkeychomp]

Nicely done Al!

Alex

[alankelly]

Feb 12, 2024 22:10:19 GMT 1 donkeychomp said:

Nicely done Al!

Alex

Thanks

Bloody hate doing stuff on other peoples bikes

If you drop a clanger on your own engine thats just unlucky but you don’t want to do that on a friends😔

[abar121]

Nice job Al!

[steve63]

Excellent job 

Had it been under the sea for a decade?

Just interested to know how this damage has come about. The outside of the cases look OK. It just looks like the gasket faces are corroded but everywhere else is fine?

[lcmarky]

Feb 12, 2024 18:20:32 GMT 1 alankelly said:

All done and waiting for a 2mm spacer

“Another one lives to fight another day” 😎

Good work & exactly what I would have done.  You now have a good base to work with.

[lcmarky]

You could probably bore the damage out of the vertical pieces too and then screw some material back on in it's place..