Author Topic: how much heat can a cb400f 1976 carb get before it distorts or melts?  (Read 757 times)

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Offline Redline it

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does anyone know, or have a ball park range of heat in 'F before a carb has before it encounters irreversible damage from applied heat gun, hair dryer etc. if not would anyone like to take a guess, from the material the carb body is made from. thanks if you can help.

 i got 3 stuck slides and 4 stuck emulsion tubes in a tight group of carbs, low mileage, with slight signs of rust near the bottom of the slides. flooding with pb blaster, one came out fairly easy and left no pitting or corrosion in the length of the slide boor or slide. they're the best looking set of carbs i've ever had, the air idle limiter jet caps are still on them, they were stuck as well as the float pins but back and forth so iittle at a time they all are loose now.

 i don't want to repeat the mistakes i've made unsticking slides in the past by wedging something under the intake side and prying up on them. i've heated them to the point of not being able to hold them. still no signs of microscopic movement.

so i got some trash carb bodies with 4 holes in each carb when someone bored them oversized, i see how thin in places they are,  so i'm gonna see what they'll handle, if it's 200+ degrees or more. it's not magnesium is it? more like aluminumish.

 i was thinking of making a jig out of a bowl, with a compressed air fitting, and closing as much vents etc to see if high pressure could shoot it out. or pack some controlled level of black powder in it, with fuse, that's  if everything else fails.

Offline willbird

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I hope you’re joking about the black powder ?

There almost has to be galvanic or some other type of corrosion holding the parts together?




Bill

Offline Scootch

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Maybe try cooling it the refrigerator to see what that does. Then maybe the freezer. Or freeze spray. Surely solvents of some kind can do the trick...

Offline willbird

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Soak in garage sale crock pot filled with ballistol ?

Offline 69cb750

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Quote
does anyone know, or have a ball park range of heat in 'F before a carb has before it encounters irreversible damage from applied heat gun, hair dryer etc. if not would anyone like to take a guess, from the material the carb body is made from. thanks if you can help.
Propane torch and penetrating oil, pry gently under slide.
If that fails the slide can be machined out with end mill getting very close to one side.

Offline jgger

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Oven heat will be more even than using a focused heat source.i think maybe a nicer one something like Dawn and water mixed and slowly soak in a pot on the stove. But that's just a guess. You're on your own with my advise!
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Offline ekpent

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When I am freeing stuck carbs, and a lot of times its from varnish, I use an acid brush to apply some carb dunk out of my gallon can and let it work for awhile. I then go at it with a heat gun but cannot tell you the temperature. It does not take a tremendous amount of heat to melt old varnish. These carbs get plenty of heat living behind an engine. Brass float can expand and deform with too much direct heat so a shield is good on them and plastic floats also.

Offline Rosinante

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Maltby's Premium Rust Dissolving Penetrant is the best.  Other than their website, it can be had at industrial supply places and diesel and heavy equipment shops.  And my favorite Porsche mechanic's shop (with 50 years' experience).  Truly better than all the rest. 

Without it, I'd try another penetrant.

I would not expect a hair dryer to damage carbs, except for o-rings and such.  And of course, floats especially plastic ones. 
1978 CB750K

Offline TwoTired

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The carb castings are an alloy similar to pot metal.  It does have a low melting point depending on the actual alloys used.    If it has tin in the alloy, you looking at something around 400 degrees F.   Probably safe using 300 degree heat for the castings.  But, if there is plastic involved, 300 is the upper limit I would use, and safer with 250 F.

Never...Ever pry on the slides with any object near the hardness of the slides.  You will just distort the slide metal "lip" and it'll make grooves in the bore once it is forced to move.  I have a set where some numbskull did this.  They are misc. parts carbs now.  Never to be run on another engine.  Grooves in the bore leak air and make later tuning near impossible.  One of the carbs in this set has the bore ovaled for the air passage and a very mangled and has a scored slide to match.

The very best loosening penetrating oil I've ever used was ATF mixed with acetone.

Lloyd... (SOHC4 #11 Original Mail List)
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Offline TwoTired

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A heat gun or hair dryer will never provide sufficient heat to cause damage to the carb body.

Err...  not so sure about that.  I have a Titan ProV55 Heat gun that can put out 1200 degrees F on the 1500 watt setting. (Though you can dial it down).  I agree a hair dryer is pretty safe, though.

Cheers!
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

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Offline BenelliSEI

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #10 on: June 11, 2023, 05:29:28 PM »
Any stuck slide I have encountered is usually fuel that has turned to varnish. I drop the carb in a pot of boiling water and they slide out after a few minutes……..

Offline Mark1976

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #11 on: June 11, 2023, 06:06:02 PM »
   I've done the pot of boiling water,  when it works, its great. To calj's point, I've done this method as well, keep the flame moving over a small area and expand outward in small circles.  When it works, its great as well, if it remains stuck, try quenching the slide with PB Blaster, that may help. We've done this for years on studs that are stuck in ford flathead blocks, its been quite effective. I've still got a rack of fz750 carbs that I was never able to free up, soaked, boiled, and torched, nothing worked.
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Offline grcamna2

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #12 on: June 11, 2023, 07:14:29 PM »
Any stuck slide I have encountered is usually fuel that has turned to varnish. I drop the carb in a pot of boiling water and they slide out after a few minutes……..

I like this idea + you can put Simple Green purple HD solution into the water with it and it will make the surface of the carbs look nice;a warm penetrating(Liquid Wrench is a good product)liquid in a pot about 160-175 degrees?

I put a carb in an oven and it warped the slide bore;it was un-usable after that and it's a parts carb now..
hot liquid is the same temperature all the way through and I like that because it will evenly heat all the parts of the carbs. at the same time.
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline RAFster122s

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #13 on: June 11, 2023, 10:14:04 PM »
MAPP gas has changed a while back, now all you can get is MAPP + I think it is called. It barely has 200 more degrees than propane if I remember correctly but it does tend to work better, faster than propane.
Thank the EPA most likely...
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Offline Redline it

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #14 on: June 11, 2023, 11:40:54 PM »
there's a lot of excellent response here, i've been away from riding an xr650r which is out of this world fun, if only they were around in the late 70s, they're that much of blast. anyway getting the responses even though my memory is taking a dump, the ones that i had questions from in the past were well drilled in my memory and it's a pleasure to know you're all around still together.

got no where today with heating it 2 times and pb blaster then pulling like heck on the aluminum elbow on top even with a dowl in the hole leveraging on the top of the stipped carb, nothin. they are tight in clearances more than the others i got. i wasn't kidding about the black powder, i loose patience and if anything seeing the slide fire off leaving only a trail would make me happy so i'd quit tormenting myself, every carb project there's some other catch that wont budge.

this'll explain the levels of frustration as an example, 7 yrs ago or so, it's probably here on the site,  was working on a rack of 4 400f carbs trying only to get the float levels bench tested before mounting them, i've worked on bikes my whole life, every day of completely disassembling because of a peculiar 1 or 2 various carbs would be pouring out overflows, while one or 2 others wouldn't be getting any gas. they switched every day, on the 30th day i was so frustrated that instead of keeping the jets in the same bowls, screws in the threads they came out of, i piled everything in one pile and put every jet float and pins just wherever they randomly were picked for, and the sob had no leaks, and fuel levels all were spot on. for the next 6 yrs. i ride it every day, until 2 yrs ago, and it broke the day i went to look at this new addition. got a flat and to push it 5 miles, riding a quarter mile leaning over the bars. is all the cheating i could do to get a bus ride home to get a wheel off of a 400 that's been sitting in the garage the past 10 yrs and outside since the 80's on what looks like the stock tire, it was so hard that you could file it, i aired it up it had a slight valve core leak, it was almost midnight getting back to where the bike was with an air compressor which i didnt use, put it on adjusted the brakes to the max adjustment and rode it 12-15 miles, on 40 yr old tire and tube. in 05 i put that motor that's sat in back yard uncovered in my frame after work one night because my motor cracked a compression ring 15 miles away from home, going about 75mph 90 miles one way, it fell on it's face, didnt' pull over i rode it home at 45 or 50 all she'd do, and rode it to work 90 miles away the next day. then i realized the motor only had a just over a 1000miles on it.

 summarizing all that was input: i'm first gonna try the boiling water, for a few mins, i gotta find the heat infra red gun to keep track of temps for now then spray it with pb blaster as that's all i got tonight, that'll keep the black powder in the can anyways. caring for my mom the last 9 yrs her in hospital bed, in the living room. she was a handful to say the least, she passed away 1 yr ago 2 days ago. bike is in the living room now. i thought i would have it made  in 2 weeks after she was gone. it's only gone downhill since then.


Offline grcamna2

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #15 on: June 12, 2023, 12:27:43 AM »
Try hot water(maybe 190,almost boiling?)with Simple Green purple HD(Home Depot or Lowes)and leave them in for almost an hr?
Attach a wire coat hanger on both ends of the carbs to rattle them every 15mins while the water's hot.
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
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Offline Kevnz

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #16 on: June 12, 2023, 12:45:16 AM »
I've freed seized carb slides with acetone. Worked immediately, dissolves that varnish that nothing else seems to touch, even cleans up the outside.
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Offline Redline it

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #17 on: June 14, 2023, 09:39:11 AM »
Any stuck slide I have encountered is usually fuel that has turned to varnish. I drop the carb in a pot of boiling water and they slide out after a few minutes……..


I spent 1/2 a night making a slide puller, to have something to hold and tap on the slide, the other night and a half i spent trying to pb blaster it and tap it out with no luck at all, this morning i boiled some water and after about 2 mins of soaking in not a rolling boil but close and it moved 1/4 inch, then it pulled out smooth leaving most of the varnish along the grove ?slide pin. it close to being rust, but kerosene cut it and a lot of rubbing got that out smooth. the emulsion tube came out after 30 mins of pushing and tapping. yaaa! couple more questions, the air mixture screws were all stuck pretty hard, got them loose, they all have the limiter caps on, do you think i need to pull the screws? i want to save those caps, or just blow em out with the compressor, there's a little port hole in the bore bottom center that's just inside of the slide, would that be connected to the air screw or the pilot jet? in 40 yrs i've had no luck with stuck slides without prying them up with something that leaves damaged carbs. i got 2 more to go plus 3 emulsion tubes thanks for the tip, this one carb looks brand new now!

Offline newday777

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #18 on: June 14, 2023, 10:28:15 AM »
The limiter caps are pressed on the screws, heat and pry off.
And yes the screws have to come out along with the tiny oring, flat washer and spring on each screw, so you can properly clean out the ports in those circuits.
Stu
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My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
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2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
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Offline robvangulik

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Re: how much heat can a cb400f 1976 carb get before it distorts or melts?
« Reply #19 on: June 14, 2023, 10:53:46 AM »
The limiter caps are pressed on the screws, heat and pry off.
And yes the screws have to come out along with the tiny oring, flat washer and spring on each screw, so you can properly clean out the ports in those circuits.
No O-ring, no washer, just the screw and spring....