Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Dazza215 on April 19, 2017, 11:46:45 AM
-
I sent my head, barrels, rocker cover etc to the vapour blaster. Currently waiting for the call to collect them.
I feel like an expectant father. Surely this is not right!!!
Ive never gone to this level of restoration before, So chaps, when I get them back, what do I need to ensure before putting the engine back together?
Thanks in advance
-
Make sure every single grain of glass bead is removed from all the oil ways you can find, and the oil ways you can't find and ensure no engineered surfaces have been damaged during the process.
-
After having my engine cases vapour blasted I was careful to remove every scap of glass beads from the oilways, I run a tap down every tapped hole, in short, I was paranoid about glass bits damaging the internals so I was scrupulously clean when reassembling it.
Fast forward seven years. I went to replace the camshaft with one that wasn't worn and the first thing I noticed was loads of swarf and glass bits. The head, rocker cover, crankshaft, shells, oilpump are all now scrap. My theory is that the glass beads were lurking up a dead end oil path in the bottom crankcase, like the one that's got the plug in behind the alternator.
Luckily I had a spare dismantled engine which is now not far off ready.
Hope you fare better than I did.
-
Lucky you did have a spare Mike ;D. Just one piece of glass bead can wreck a beautifully restored engine :'( :'( :'(
-
Thanks both. I was going to go over the oil ways with a maginfying glass and carb cleaner and compressed air and, and, and.......
I'm just praying that the guy does a good job and he knows about these things.
I will check everything but i am still neurotic about ruining my engine. lol. :-[
-
I hope all goes well for you. Does your magnifying glass go round cornets and is it so minute you need another magnifying glass to see it ?
-
Just to hijack the thread..
The replacement head has two sheared off M6 bolts. Drilling them out and tapping them didn't work out accurately enough with my crappy £50 piller drill and the rocker cover bolts don't kgo in.
I've had to get an engineering bod to spark erode the bolts out and replace the threads. Only tenner a hole; could have been worse.
-
These sort of jobs make compressors such a great piece of kit to have, and they have never been cheaper to buy.
-
[attach=1]
This is how they turned out.
-
I've got a compressor, didn't help.
-
O dear, I hope you never had the head basted with the valves in ?
-
I am replacing the valves but didnt want the seats ruined.
-
Cheaper to reface the valves and regrind the seats than new valves, what is wrong with the valves ?
-
They were covered in sandstone from the American desert i think.
I thought thats what you were referencing with your last comment.
Why would you not have the head blasted with the valves in? Surely with the valves in it will protect the guides and the seats etc?
-
They were covered in sandstone from the American desert i think.
I thought thats what you were referencing with your last comment.
Why would you not have the head blasted with the valves in? Surely with the valves in it will protect the guides and the seats etc?
If the blaster knew what he was doing, they would have put bungs in to protect any machined surfaces
-
So do you think these valves will be ok with a clean up and a relapping?
-
So do you think these valves will be ok with a clean up and a relapping?
You will not until you have taken the valves out to see if there is any pitting, which lapping will never get rid of.
-
Thanks Trigger, that's the job for this evening.
I'll let you know. Fingers crossed I won't need to buy the valves.
-
Back to Vapour blasting and cleaning up after, has anyone knocked the plug out of the end of the main gallery that sits behind the alternator. If so what is the process for fitting it back, do we centre pop it around the edges etc?
-
No need for that, just twat the thing in and friction will do the rest.
-
I too relied on compressed air, etc. to clean out the vapour blasting deposits on my 400 casings. I could only find any in the blanked-off oilway mentioned already in this thread. It occurs to me that if doing it again, I could deploy the 'endoscope' thing my wife bought me for Christmas... before the comments come in, it's strictly for engineering use!
Cheers, D.
-
No need for that, just twat the thing in and friction will do the rest.
Is that a metric KiloTwat or Imperial Twats per Foot ;D ;D ;D
Thanks for getting back
neil
-
850 milliTwats, you don't want to snap anything.
-
850 milliTwats, you don't want to snap anything.
You are well out Mike, 550 milli twats is the recommended measurement in my Honda manual ;D ;D
-
You are well out Mike, 550 milli twats is the recommended measurement in my Honda manual ;D ;D
I bet you have the official Honda twatometer, that was only issued to dealers, and now as rare as hens teeth.
-
Silly question..........vapour blasting use only water or any "media" more? If only use Water/vapour where is the problem about the cleaning up after?
-
As i understand it its a water based slurry with glass beads. Because the glass beads are smooth (unlike sand or grit), it's kinder to the metal.
-
Has any one tried Soda blasting yet. I am presuming (always a dangerous thing) that any residue would dissolve with water.