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heating a carb in the oven

  • Thread starter Thread starter rideOn
  • Start date Start date
R

rideOn

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i'm fixing to do the carbs next week and the mix screw in #1 is froze. is it safe to stick that carb in the oven, say around 150 deg. or so, to expand the aluminum to remove the screw?
 
Probably a better idea to soak it with PB Blaster for a few days, then heat locally with a small torch or heat gun, although I don't think 150F would hurt much. Be sure to remove the diaphram & slide assy 1st...
 
I was a big fan of PB Blaster until I read somewhere that a 50/50 mix of ATF and Acetone is far better. I had the opportunity to try this compund a couple of weeks ago and am confident that it worked on something that PB wouldn't have. I'd like you to try it (in a well ventilated area) and report on your results.
Also, FWIW, I'd be surprised if heating the entire carb is going to help loosen that screw simply because the brass is going to expand as well. I wonder if the difference in the coefficients of thermal expansion between brass and aluminum is large enough to lossen the fit. Anyone know fer sure?
Willie
 
Here's a chart. 22.2 vs 13. The alluminum will expand a bit more. I don't know if that will be enough once you figure actual alloys involved, how much corrostion there is, etc. At least the ratio is in the right direction.
 
The expansion rate difference is why it is better to use a small torch so you heat up the aluminum faster. Ray.
 
Dogma said:
Here's a chart. 22.2 vs 13. The alluminum will expand a bit more. I don't know if that will be enough once you figure actual alloys involved, how much corrostion there is, etc. At least the ratio is in the right direction.
Click to expand...
It may be in the right direction, but it's not as good as you say.

I just looked at that chart and have no idea where you got that 13. Brass was listed as 18.7. :o

.
 
willie said:
I was a big fan of PB Blaster until I read somewhere that a 50/50 mix of ATF and Acetone is far better...
Click to expand...

funny when i took a motorcycle repair class one thing they always said no too was playing mad scientist with your chemicals
 
If all else fails drop it in the carb dip and ignore it for 3-4 days.
Works with the NAPA brand dip for me.
 
Steve said:
It may be in the right direction, but it's not as good as you say.

I just looked at that chart and have no idea where you got that 13. Brass was listed as 18.7. :o.
Click to expand...

I believe Dogma correctly used the thermal numbers for aluminum vs. steel (not brass), as that's what the OEM mix screws are machined from - some of the aftermarket mix screws are made from brass...
 
All I know is please make sure the carb has had all of the vapors removed prior to heating (especially from inside the oven). I work in Indianapolis so I'm sure I wont hear the BOOM if there are vapors still in the carb.:)
 
I use a butane torch type lighter to heat up the cast body. I have also used the bigger propane torches. the expansion of the cast aluminum happens before the brass and loosens up the "crust" in the threads. heating up the whole thing in a oven is not the application of heat you want. it is too slow. what you want is a quick heating of the immediate area surrounding the stuck mixture screw.
 
hikermikem said:
I believe Dogma correctly used the thermal numbers for aluminum vs. steel (not brass), as that's what the OEM mix screws are machined from - some of the aftermarket mix screws are made from brass...
Click to expand...

It being late when I posted, an I in a hurry, I looked at the chart cross-eyed and posted the value for bismuth.

The screws that I recently knocked out of the carbs that came with my 1000 were very soft, so brass seemed quite plausible to me. My new rack still has the plugs in it, so hopefully I don't have to find out how tough the steel screws are when I clean them.

Anyhow, I second (third? Fourth?) the idea of using a torch instead of the oven.
 
When I removed the mixture screws on my brother's 1000g, it seemed as if they were factory sealed with a red colored sealant, maybe a lacquer. In this case, I used some spray gasket remover into screw recess and waited. After a while I could get screw to move and by methodically loosening and tightening the screw a little more each direction could I finally get it to turn out without further drama. I would try to get them to tighten in so that I could spray more solvent and dissolve this sealant ring that was gunking up the threads. Once dissolved, the screws would usually back out fine. Note: any sort of paint remover would probably dissolve this sealant, I just happened to have gasket remover handy which readily dissolves paint.

Two fundamental keys to success here. One, get or make a screwdriver that precisely fits into the screw slot. I ground down a cheap flat screwdriver to fit the slot in width and girth (not sure how to describe a screw's slot dimensions). Secondly, patience pays off. Spray one with penetrant or with solvent and give it time to work. Pick up something else to mess with while waiting. Then try turning screw both directions, once its starts to move it is only a matter of time before it will come out.

Finally, acetone and ATF, may have to give that a try. Slightly mad Chemist here. I tend to like MEK a little better than acetone.
 
Dogma said:
Anyhow, I second (third? Fourth?) the idea of using a torch instead of the oven.
Click to expand...
Wouldn't you rather have a fifth?
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i think a good laquer thinner would work better than methel ethel ketone, or how ever its spelled

maybe you could--- boil---them, thats what i do when i need to remove studs or stuff out of aluminum, just make sure to use thick gloves cause the aluminum gets hot!
and i think its safer than melting or warping aluminum with open heat from flames ect...,and there be clean!!!!!
 
i've been periodically squirting in pb blaster (i had a couple of freebie cans). i figured it couldn't hurt. i have a propane torch and could try that. thanks for the tips, i'm sure i'll get the screw out with one of these methods.

what is a good source for getting a replacement mix screw. i pretty much stripped out the head that had a previously good start on being ruined.
 
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