View Full Version : Substance for Dissolving Calcium like Deposits in Carburettors

07-28-2012, 06:17 AM
As in title ..

is there anything out there that will desolve these deposits ...without effecting brass of the magnesium alloy castings.

this is about my work on the two Honda c70's of just bought.

spent a lot of time unblocking jets ..cleaning them out etc.

tried ultrasonic cleaner it didn't work...nor did air or degreaser

resorted to wire...but have feeling the wire didn't push every thing out ...one jet is 0.35mm...wire wouldn't of damaged it really as it is quite long about 3/4 of an inch....i will replace them with new sometime ..

so what's the chemical called ...and what are these deposits ..that i call calcium .

found varius reference around the net to something called CLR


but not seen this stuff in the uk

all the best..markj

07-28-2012, 06:28 AM
sounds like aluminium oxide, if the carbs are ali, if so then an alkaline solution will clean, add pearl caustic to water SLOWLY, a metal container like an old stainless saucepan works well, solution will get hot, enough to melt through a bucket [ my version of the china syndrome], dip them in on string and the surface will etch/ deposit dissolve, good for etching ali and stripping paint too!

07-28-2012, 06:35 AM
im going into town..to see if there is such a thing as calcium lime rust remover here under another name perhaps.

all the best.markj

07-28-2012, 07:08 AM
Not being a chemist I can't tell you what it is but it's not calcium in the sense of water and aluminum corrosion. It's a byproduct of gasoline. I'm sure you're referring to when pilot jets get plugged. When a carburetor sits for a long period, with the new fuels generally longer than 6 months, the fuel will evaporate and leave that carbon byproduct in the jet. I like you have tried motorcycle specific carburetor cleaners but they won't penetrate such small orifices. I have made up a set of 'pricker wires' from piano wire. They are soldered into a small brass piece which serves as a handle. The smallest is around .008 (.2 mm). I use these to poke through the jet and then let is sit in carb cleaner for an hour or so.
I have never seen any buildup in the needle or main jets, just the pilots.
In the fall before I put my bikes away I fill the tank and drain the carbs. On my mowers and such I run them till they stall so there's not much fuel left in the carb. On bigger pieces of equipment I fill the tanks and put a fuel stabilizer in it.

07-28-2012, 07:38 AM
i`m not sure if you can still get it(been a while since i purchased any) but i used to use a product called Berryman`s Carb Dip - came in a gallon can- about 5 minutes in the stuff would dissolve any gunk.

07-28-2012, 07:41 AM
this had been stood for 16 years ..even the main jet was plugged ..

i had to straiten out a spring similar to a biro spring to do the unplugging on the small jet.

all the best.markj

07-28-2012, 08:29 AM
I would not use CLR. There are some very small holes in those little carbs and if you etch them away they will never work right again.

Two things I use on them are white vinegar or lime juice. But even then it is a guess. The problem with them is not plugged jets, they can be unplugged, it's the buildup of the "white" stuff in one or more of the very tiny passageways drilled in the carb. Once those become eaten away it's usually to late and I consider the carb junk.

Honda thinks very highly of those things and a new one, if you can find one, is in the $150 price range. What a lot of people are doing is fitting a Chinese carb from one of the clones being made. They can be found on ebay or my favorite site for little Honda parts, http://www.dratv.com/

07-28-2012, 10:03 AM
I have soaked a dis-assembled carb in mineral spirits over night then used an ultrasonic cleaner with mineral spirits OUTSIDE for several cycles until the fluid was slightly warm. Worked like a champ on outboard and chainsaw carbs.


07-28-2012, 10:24 AM
Sounds like you need a 0.35mm drill bit.


07-28-2012, 11:59 AM
It isn't likely calcium. A very common additive in unleaded gasoline is MMT (methylcyclopentadienyl manganese tricarbonyl). It will leave manganese deposits in carbs that are light coloured. I don't think there is an effective chemical method of removing it.

michigan doug
07-28-2012, 02:48 PM
"if the carbs are ali, if so then an alkaline solution will clean, add pearl caustic to water SLOWLY"

While this might work, you have to understand that pearl caustic (sodium hydroxide, ie lye) solutions eat aluminum for breakfast and produce hydrogen as a byproduct. Pretty quickly I might add. Approach with extreme caution. Magnesium, not much better.

Finest regards,


07-28-2012, 03:06 PM
I'm on the second carb now on the later cub (i bought two) ..there is about 7 years difference between when each was last run ..

the first one was last ran, 7 years before this one

this one has completely different deposits in it ..

like varnish.

the first cub is now running sweetly.

all the best..markj

07-28-2012, 10:29 PM
I've seen these whitish deposits in elderly carbs. It is not likely to be calcium-based, but possibly an aluminum or zinc compound, depending on what the carb body is made from. This is supported by the fact that there is often some pitting of the body in the same area. If it is a mineral deposit, organic solvents aren't going to be much help. The last time I saw these, a Phosphoric acid dip did the trick.

J Tiers
07-28-2012, 11:44 PM
Phosphoric may do it......

Sounds like (without seeing it) a corrosion product related to water/humidity. Those tend to cause other problems besides just the gunk, so be prepared for the carb to still not be good afterwards. Think of the stuff as "zinc casting rust", and you will get the idea.

The last comment on varnish seems odd though, does that refer to the same stuff? Because varnish can have flaky stuff also, of "light color", and the ticket there would probably be a solvent.

07-29-2012, 08:12 AM
no corrosion in there ..once the deposits are removed the magnesium is like new ...no pitting .

they are both clean but for the idle orifice on both ..this is proving impossible to clean .

shown here ..the smaller hole of the two..pic looking down the slider hole ..this picture is not mine ...but shows how it should be .

i cant see through mine nor get anything down it ..its solid


all the best.markj

07-29-2012, 08:23 AM
ive not got phosphoric acid ..i do have Oxalic Acid...anygood ?

for now ive put a few drops of cellulose thinners down the hole ..before i get brutal

all the best.markj

07-29-2012, 08:38 AM
toilet duck or general toilet cleaner is phosphoric- usually!, check on the bottle

07-29-2012, 08:51 AM
The tub of Hammerite rust remover gel I have has phosphoric in it..


J Tiers
07-29-2012, 09:06 AM
If it isn't corrosion, you can probably forget about the acids. They are only good against corrosion, and not against most all the gasoline deposits.

A strong cleaner like "purple power" or Castrol purple cleaner might do something. But they are composed of both lye and other cleaning solvents, so they may do more damage than good unless the gunk is removed quickly. While they DO "eat" aluminum and casting alloys, a short cleaning dunk does nothing but foam up alarmingly... the total material removed is undetectable. Not so if you must soak the part.

It sounds as though a solvent is the ticket. I might suggest a closed container of gasoline or possibly kerosene (less flammable) with a good soak of a few days. If that tube is caked to any depth, it may take some time to penetrate the gunk. And you may even need to mechanically remove some of the gunk first (carefully) just to allow the solvent to get to the material near the far end.

Some sort of scrubbing may still be needed, some of those deposits do not really dissolve, but only get to a sort of "jelly" state with solvents.

07-29-2012, 11:29 AM
A strong cleaner like "purple power" or Castrol purple cleaner might do something. But they are composed of both lye and other cleaning solvents, so they may do more damage than good unless the gunk is removed quickly. While they DO "eat" aluminum and casting alloys, a short cleaning dunk does nothing but foam up alarmingly... the total material removed is undetectable. Not so if you must soak the part.

I refurbish a lot of old bikes. Mostly Japanese, but brit and american iron as well. I run into tons of carbs with that white crusty crud in them, Purple power is what I use.

Tear the carbs completely apart, separate different metals and put each type of metal in it's own bowl, I use plastic coffee cans and use purple power mixed about 50/50 with water let them soak a while and check on them every couple of hours. I don't really know how critical keeping the dissimilar metals apart is, just prefer keeping anything that could form a 'battery' apart.
I've used straight purple power and a toothbrush with good results on hard spots, and even soaked in straight purple with no ill effects.

I can't say with absolute certainty that it won't hurt them, but they've always come out clean with smooth surfaces and no pits, so to the eye, it doesn't look like they've corroded. Jets come out looking like new.

Sometimes you the crud will start to 'boil' which makes you step back a bit....

07-29-2012, 11:50 AM
I also use Purple Power type cleaners for carbs (usually aluminum) and other parts from chainsaws (mag alloy and small engines. I dilute it about 4:1 and put it in an ultrasonic cleaner. Purple power is lye and surfactants, and although it could eat aluminum (and dull paint), it show no such material effects other than "clean". I don't use it "undiluted" or leave parts in solution over night! 10 minutes to maybe a hour for really bad stuff. The Ultrasonic just provides the "scrubbing" action. On small carbs I like to put them in a second bath of just hot water - trapped cleaner in passages will just make for more corrosion problems!

My main ultrasonic bath is a 4 transducer commercial unit -not the tiny jewelry stuff availablle cheaply - that warms the water through the ultrasonic action (I do use the small units for small parts). If your unit is not powerful enough to raise the bath temperature, use hot water (fauclet temps) for the initial dilution.

07-29-2012, 02:13 PM
ive unblocked that tiny hole now

just working on the actual idle jet now .

no purple power here

the cellulose thinners seams to have done a good job

all the best..markj

J Tiers
07-29-2012, 04:27 PM
Good work.

As for the lye and material removeal, kendall and Lakeside are probably correct.... I tried to use purple cleaner once to DE-BURR some thin flash on a machined aluminum part that I couldn't do with a deburring tool. I was very disappointed, I left the parts in for 30 min, with very active bubbling going on.

When I pulled them out, not much had changed. I didn't have any idea of the molarity of the lye in the purple, so perhaps I should not have been surprised... there is a lot of solid material, and the lye may have simply become exhausted before the aluminum was eroded. I didn't have a big container, so the total active material was likely small.

Evidently the warnings about "it will eat your parts" are a bit overblown for the typical concentrations of lye. I have no doubt that one could make a solution that would be harmful.... but purple power isn't it, unless you put the metal in a larger container of it.

With a big enough container full, I don't doubt you could make the carb nearly disappear.....

07-29-2012, 11:04 PM
According to an MSDS for Purple Power, it is "<10%" Sodium Hydroxide, so it should be relatively tame.

This is the white stuff I mentioned earlier in an elderly Amal carb:


These bodies are a diecast zinc alloy, and the Phosphoric worked well. To see how the carbs cleaned up:


J Tiers
07-30-2012, 12:28 AM
the "tameness" isn't so much in the concentration alone, but the concentration AND the total volume of solution, which affects the total volume of reactive material.

A vat of the stuff will eat up a part that a cupful might only clean.

07-30-2012, 01:44 AM

True enough, but it would be sort of tricky to try to adjust the volume to make sure the reaction doesn't go too far. Probably better to use concentration, time, and maybe temp for sticklers.

07-30-2012, 06:47 AM
Once upon a time, I entrusted a set of gs750 slide carbs in good but dirty condition to a company who allegedly did this sort of thing for lots of people, they left them overnight in their "chemical cleaning bath" which turned out to be caustic based. The sorry mess I got back, with distorted slide bores, and obvious erosion on the slideways from the chemicals means I personally would never use a caustic based cleaner for the job. I ended up with flatslides unable to find a replacement set of original carbs in useable condition.

If you get too stuck, c50/70/90 carbs are on the bay, or at least chinese replica's of the originals. I think from experience of the replicas however you'd be better off making good any wear in the originals.

07-30-2012, 06:58 AM
Not the most professional looking tools ..but they worked
lots of patients required and maybe 3 hours of your time !!!!!
tools ..now a bit bent up, after the last operation... the pilot jet itself ..they were strait when i started
showing the two for the main jet ..one cranked so i could uses it as a sort of drill ..yes they were that solidly packed .


here you see the pilot orifice tool ..made out of a video recorder spring ........you need springs because it resists bending ..that spring has a wire diameter of 0.25mm.. (jet was 0.38mm) I'm told that you can use guitar strings ...G-string i think........if you have a music shop near you .....I'm told, that when home bargains (uk chain store) have guitars in stock they stock the strings.


in use .......i couldn't seem to get it in from the other side, as the hole is off set from the pilot jet housing tube..nor can i see light ..because of the offset.
you may be able to see light if you held a torch to it ..but not the sun or the workshop lights would do it ....
in use .


pipe cleaners come in handy as well ..dip them in cellulose thinners....don't get any of the thinners on rubber .


i don't know how they get on in the 3rd world with this bike ....as they sell petrol at the side of the road in pop bottles..i would imagine everyone's travelling around with their pilot jets blocked.

and that guy on youtube ..he's travelling across the world on a c90

he must carry a spare carb and jets around with him .
i will replace the jets once on the road ..

all the best.markj

J Tiers
07-30-2012, 08:22 AM

True enough, but it would be sort of tricky to try to adjust the volume to make sure the reaction doesn't go too far. Probably better to use concentration, time, and maybe temp for sticklers.

or solvents, as the OP did, and which has been recommended here as well.

I would NEVER leave a susceptible metal in a large tank overnight..... with so much available reactive material, damage can be done. With a small amount, the material will be exhausted long before you can measure a change without a rather sensitive scale.

Any use of a caustic on a susceptible material is tricky, you have to hope the caustic gets the gunk before the metal is damaged. Actually, caustics don't work as well on liquid petroleum as they do on vegetable oils, but they do work pretty well on crosslinked oils that form sticky films.. When oils crosslink they must have active sites, double bonds which develop and can bond with others. Liquid petroleums don't have them, and are best attacked with solvents, but after years of exposure, petroleum oils can develop broken bonds and crosslink similarly to a "drying" type vegetable oil like tung oil.

And a blocked jet is the worst, because the area for attack is so small..... just the end of a 0.4mm bore! And the bore may be 10x that long. that will take forever, as the caustics eat the rest of the carb.... no thanks. Solvents can be left to soften things up at least, and at best may dissolve quite a bit of the gunk. No worries about metal, although rubber parts might be an issue, depending.

07-30-2012, 11:15 AM
I was going to suggest you hammer the end of the wire flat and touch it up on an oilstone to make a rudimentary spade drill. Might have saved a bit of time, but obviously all is OK.

J. Randall
07-30-2012, 11:59 AM
Mark for several yrs. now I have settled on a strand of cable, depending on the size of the hole, I sometime use a strand from a throttle cable, or if bigger, I have some larger size cable I use. When you unwind them they have about the same form as a straightened spring.

07-30-2012, 01:36 PM
In the photo below is an example of why you should not use anything corrosive to dissolve deposits in a carburetor. Those two little brass balls pressed into the carb are plugging factory drilled holes. To rout fuel/air throughout the carb they have to drill through and then across to get from point A to point B. No problem to just plug the end of the hole afterwards with a little plug. This creates pockets that not only collect the crud but also anything corrosive used to try to clean them out. Unless you can neutralize any acids in those pockets in a rinse it will continue to eat away at the passages. Years ago it was possible to drill them out clean the passage and to carefully clean any holes going into the throat of the carb. You could then replace the plug and be on your way.

It can still be done. But you must be very careful when cleaning any hole that feeds fuel to the venturi. If you distort it in any way it will alter the way the fuel is able to atomize. I would not try to use a drill like tool or action when cleaning those little holes. A smooth wire smaller in size than the hole will allow solvent to attack the deposit after you can pass the wire through.

I use a professional carb dip tank to get all the junk off that is followed with a good soaking in lemon juice, followed by a water jet tool that I fasten to my kitchen sink faucet. Its just a large hypo needle attached to the end of a small hose.

This is a really rotten Trail 90, just to show the plugs.


07-30-2012, 02:47 PM
Point noted re not using a drill, topct. With the makeshift spade drill I mentioned, I would round off and smooth the corners of the point to reduce risk of damage. The "cutting" edges are only to help the wire to chew its way through well-solidified crud. I think forcing a wire straight through could push it sideways and score the side of the hole. Opinions and technique may differ of course.

07-30-2012, 02:59 PM
i did make the wire into a drill just by chopping it at 45 degrees with the pliers .

i had it running today

it started ok ........then ran rough .........5 mins later was running smooth for about 2 mins ..then ran rough again ..and wont run smooth again now

the plugs are sooty ..the needle is in the 2nd to top groove which would make it leaner

maybe i should have cleaned the tank out (*i did drain it completely) and the fuel cock has a filter .

or it may be condenser or points

will check them over tomorrow unless i'ts got cdi

all the best.markj

07-30-2012, 04:57 PM
the plugs are sooty ..the needle is in the 2nd to top groove which would make it leaner

First try moving the circlip on the needle to the top slot.

From my recollection, that was the factory setting for the 1968 Triumph Trophy 650.

Is the exhaust smokey?

07-30-2012, 05:14 PM
only smokey when i hear the slight misses at tick over ..black smoke ..fuel smoke

strange that it ran ok for a bit ..

all the best.markj