TECH - Trueing your diaphram cover

hemigremmy

hemigremmy

New Member
#1
#1
Maybe this has been posted before but it came up in another thread and was asked about how to do it and I had one out there that I needed to do so here is a how to.
So I happen to have this old glass table top that I have been wanting to get rid of but never have and my wife has been on me to get it gone. But today it came in very handy.
I pulled this diaphram cover off of a good carb that just needed rebuilt, looked good and true even before sanding it true. But once I started sanding it I could tell it wasn't even close. I had about about a 1/4 of a sheet of 320 wet/dry sand paper, I held it flat on the glass

Here is a picture before I ever started sanding, looked pretty good I thought.

Here it is after holding it good and square and giving it a couple good swipes on the sand paper....not as true as I thought....WAY OFF!

And some more sanding....

And even more sanding.......

And after a whole lot more sanding....it finally looks good enough for me.


I took the carb and held it just right so I could get a couple good square swipes to the bottom of the carb where it mounts to the gas tank and even that flange is pretty far out of true but I know lots of people double gasket that connection so it should be fine.
 
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hemigremmy

hemigremmy

New Member
#2
#2
The cover was bowl shaped from the factory and probably some from over tightening the screws. I was just showing how out of true (flat) the cover actually was. It's not rocket science or anything, I was just trying to show how to go about making it flat and even if it looks good its probably really now truly flat like you think.

Sorry I didn't mean to waste your time with my stupidnes, it was asked how to do it on another thread and I had everything to do one.
Again, sorry!

Just FYI, people do this same thing to shave heads, clean them up and make sure that they are true or perfectly flat for a good seal.
 
The_Ruppster_86

The_Ruppster_86

New Member
#3
#3
hemigremmy said:
The cover was bowl shaped from the factory and probably some from over tightening the screws. I was just showing how out of true (flat) the cover actually was. It's not rocket science or anything, I was just trying to show how to go about making it flat and even if it looks good its probably really now truly flat like you think.

Sorry I didn't mean to waste your time with my stupidnes, it was asked how to do it on another thread and I had everything to do one.
Again, sorry!

Just FYI, people do this same thing to shave heads, clean them up and make sure that they are true or perfectly flat for a good seal.
Click to expand...
This technique has always worked well for me. I always do it to any diaphragm covers or cylinder heads. I first learned about it in the Jimmy Glenn's "How to Build a 5HP Briggs Engine" book. Thanks for sharing.:thumbsup:
 
M

metal man

New Member
#4
#4
Miniwood i think what your missing is the shiney spots are the high spots on the plate . see the glass hes using as a backer is dead flat and with the paper on it you get a flat grinding surface . as you move the part around the high spots will hit the paper first and sand down . as you keep going more and more of the high spots go away giving you more of a flat surface . so when the whole thing is flat you get a nice shine across the part .


hemigremmy nice write up man :thumbsup: good pics and easy too . :drinkup:
 
hemigremmy

hemigremmy

New Member
#7
#7
I know it is not rocket science or anything but thought since it came up and questions were asked I would go ahead and do a TECH on it just to show how it was done so others would know too.
Thanks for the compliments guys.

I have a question, on another carb I have to rebuild that came off my Raptor the cover looks really ate up and inside the diaphram cover on the carb everything was like covered in this white powder. Kind of thought it was oxidation but all the passages were almost clogged with this powdery substance and it is a real :censure: to try and get out. I soaked all the carb torn apart in GUNK brand carb cleaner for like a week then I used a wire to try and clean it all out, it worked a little. I even went and bought a set of small wire brushes from HF for airbrush cleaning to try and get the powery build up out of the passages but it is still pretty hard to get it all out. Here are some after pics of the cover after I cleaned it but you can still see some powder in it, what causes this? Could it have been because the carb alcohol at one time maybe? See how pittted up the cover is too. Look at the lower passage on the left in the first picture, see all the white powery build up.


These work great on carbs by the way @ $2.29!!
5 Piece Airbrush Cleaning Brushes
 
Richard Trotter

Richard Trotter

#8
#8
The white powder could be aluminium oxide. Even the low amount of alcohol in the gas today attract water. If left standing, it will create an acid which will create the oxide. Soaking in vinegar will remove it but don't let it soak too long. Vinegar is a mild acid and if aluminium is left too long, it will eat it. Some of the new gas additives will prevent the acid from forming. I use Stabil Marine.
 
creia

creia

#10
#10
hemigremmy,
Very nice step-by-step documentation of a common issue on Briggs diaphram covers.:thumbsup: The Ruppster is exactly correct- your technique is also commonly used to true up cylinder heads as well. If I may add to your excellent "how to" thread, the preferred method is a "figure 8" motion when sanding/truing either a diaphram cover or cylinder head.
I'm going to pay you the ultimate complement and request to the powers to be that your excellent how-to thread be permanently enshrined on this forum as a "Sticky".:scooter:
 
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hemigremmy

hemigremmy

New Member
#12
#12
Maybe we could get a MOD to make a "Tech" folder and when somebody does a tech article it could be put in the title of it and moved to the folder, I think it was metal man that did one on the briggs recoil wind up that could be put in there as well. I have a couple pulsa jet carbs I need to rebuild that I could do a tech on as well. I'm also getting ready to install a head gasket and head, can do a tech on torqueing the bolts and the the order that they are to be torqued.
I have a lot to do just need to do it and take pictures and make the tech articale along the way. It's all simple stuff and comes in handy to everybody, I was a "NEWB" not to long ago and had questions and still do but now I am trying to contribute and help others along my journey to learn.
Again thanks for everything guys!:thumbsup:
 
Miniwood

Miniwood

New Member
#16
#16
Sorry i see what you did now with the glass table.
good info.
didnt mean to be ugly just wondering what you were doing.
thought at first you were just sanding the gasket residue off. re-read my post ... didnt come out the right way,,, sorry
hemigremmy said:
The cover was bowl shaped from the factory and probably some from over tightening the screws. I was just showing how out of true (flat) the cover actually was. It's not rocket science or anything, I was just trying to show how to go about making it flat and even if it looks good its probably really now truly flat like you think.

Sorry I didn't mean to waste your time with my stupidnes, it was asked how to do it on another thread and I had everything to do one.
Again, sorry!

Just FYI, people do this same thing to shave heads, clean them up and make sure that they are true or perfectly flat for a good seal.
Click to expand...
 
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Clayon

Clayon

#17
#17
Great work hemigremmy. :thumbsup: This was a good how-to. I have a carb with the same problem so I am gonna have to go true it up. Thanks. :thumbsup:
 
jrzmac

jrzmac

Active Member
#18
#18
Yes hemigremmy, great job. Nice to see somebody that actually knows what they're doing, and can explain how to do it even better! We need more of these type of how to's around here, from guys like you, believe me!!!
 
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