Friday, August 29, 2014

Removing Corrosion and Carburettor Cleaning - Definitive Guide?

So many opinions, but what really works?
I'm going to presume the carburettor(s) are already removed. I'm not going to go down the route of remove tank, air box etc. because there are way too many variables with different models of bike. If you're already at the stage of thinking your carbs need a clean, you're probably more than capable of doing a great job. So from the simplest Amal Concentric to a bank of four Mikunis, we'll delve straight into what actually bloody works at home - 'cause that's where I need to do it.

Here's the replacements I bought off eBay. They're rough, but hopefully good enough to make one set of complete carbs for my GS550.

Possible reasons for cleaning.
  • Bike not idling correctly?
  • Misfire or flat-spot at certain engine speeds?
  • Yellow varnish on the outside?
  • Covered in dirt?
  • Maybe they're corroded?

All good reasons for a spring clean, but if you are chasing an engine running issue, make sure it isn't something mechanical, or electrical, too. It's very easy to blame the carb, so try to work through the diagnosis methodically. I'll go through the basics of this soon.

Guinea pig bike - '80 Suzuki GS550.
A little history first. It was a bargain not to be missed on eBay. I didn't even have to pick it up as my old mate Bryan worked in the area and grabbed it on his trailer. Good lad Bry, always said you were a good 'un!
The carbs were in a separate box, in bits, not looking too clever, and the engine was leaking oil. That turned out to be a clutch cover gasket not fitted correctly - so an easy fix, but the carbs weren't so easy. Two were broken where the float bowls attached so I kept my eye out for a set on eBay. Eventually, a set turned up that needed some TLC, so I got 'em bought.

Don't store your carbs in a pond.
They put up with all weathers on a bike, but are still somewhat protected by the engine and its heat. They may even get a wash with the bike occasionally too,  but when removed they tend to get left to gather dust and corrosion, and generally deteriorate. If you're going to remove them for any length of time, a good going over with WD40 is a nice way to treat this very clever fuel metering device. It all helps to protect. 
As for the ones I bought? More corrosion than the bastard Titanic, but all is not lost.

There must be a magic liquid you can just dip them in...
I've been researching more forums on this than I can shake a stick at. There's a lot of opinions - vinegar, battery acid, Pine-Sol, CLR, carb cleaner, ultrasonic cleaner, water, lemon juice, diluted, boiling, left for days, fifteen minutes only etc. etc. 
I just want to drop them in a bucket of something for half an hour and they come out like brand new, ready to be assembled. But it's not going to happen is it? 
The bodies are generally made of a cheap pot metal which doesn't put up well with acid. Sure, a quick dip might not hurt it, but you need to be very careful with what's left over at the end. Carb cleaner will remove gummed up, oily residue but won't touch corrosion or white residue.
Also, when you remove carbs from some sort of "dip" they need to be washed and dried immediately! One carb body I used as the test mule began to corrode up within half an hour of being washed and left to air dry. 

Pine-Sol gets a good rap, but isn't available in Australia. And what works in one country might be useless in another because ingredients are very often changed to meet local legislation. (WD40, for instance, has a completely different smell here compared to the UK - how I miss that aroma!)
Carb cleaner is ok on oily-type, carbon buildup, but doesn't seem to do much on some of the stuff that's been baked/dried on for years. And actual fuel injector/carburettor cleaner (the stuff you put in your fuel tank) was pretty much useless too. I expected better things from this because of how diluted it is when adding to the fuel system of a car etc.
There wasn't enough lemon juice in the house, and I wasn't keen on vinegar because I've seen how fast it can erode aluminium. I did, however, have CLR in the cupboard. 
So, I poured what was left into a bucket of hot water and dunked in my test carb (this one has already been destroyed by some buffoon trying to remove the float - it brings such joy when you happen across work like this). After soaking for twenty minutes, I took it out and put it in the sink, and was quite impressed with the results. So into the bucket with them!

It wasn't all as easy as that though. They still needed work and that's when the Jif came out.

With various brushes, and a bit of work, they started to come up pretty good. And if it means I can do them at home, all the better.

The Jif is great at removing years-old stains, and this will get the carb bodies looking pretty good. I've not gone too mad here because all I want is a working set of carbs to try on a bike; a little extra time and they'd be pristine.

You can see the colour difference between the carb that has been scrubbed with Jif, and one that's just come out of the CLR.

What about the internals?
Of course, having them shine on the outside doesn't mean they're any good on the inside. Fuel and airways get blocked over time with petrol residue and dirt etc., and then the engine won't run cleanly. It'll either have a partial misfire at certain revs, an uneven idle, or the revs might not drop down properly and you'll be chasing these annoying faults forever! It's not the easiest job to remove a bank of carbs, especially if you retain the original airbox, so you want to get it done right first off.

There are excellent diagrams in the workshop manuals which show exactly which internal drilling comes out where. From this you can use an airline to blow down them, or spray carb clean, and see if they are clear. There also great tutorials to read on the Mikuni carbs at the GS Resources forum, or on Basscliff's website along with the Suzuki workshop manuals. These guys know Suzuki GS and GSX's inside out so sorting your carbs and its jetting shouldn't be too much of a problem.

It gives you a an idea of what you can achieve at home and, more importantly, not paying a professional to do it for you. They're not perfect, and the photos probably make them look better than they actually are, but they're good enough for me to see if this bike runs. 
When the bike was delivered there were no spark plugs in it, and the carbs were in pieces in a box. One needle was bent so I had to use one of the donor carb slides (and they've different part numbers), and one of the pilot jets is now different because one I needed had to be drilled out - more butchery, but no matter, it should still fire up. 
Float heights were adjusted to 22mm, give or take a micron, and they were just slapped back together. Rubber grease was applied to the inlets and then the carbs slotted gently in... not. It took leverage baby, a lot of leverage.
Eventually they were in, then it was just the airbox to go. I can see why so many K&N's got fitted over the years. But sweat and toil prevailed, and it looked standard once more. Whoop!

A moment of truth.
Some old plugs I had laying around as testers went into the head, fuel was poured into the tank (would it leak?) and a freshly-charged battery slotted into its side. Fuel was poured into the carbs via a funnel so there was a fighting chance of getting it to the combustion chambers quickly. 
Ignition on, we have lights. Choke out and hit the button - spinning over nicely, but nothing happens. No matter, I'd soaked the bores in oil to try and offset the months, or years, of open air damage. The plugs would've oiled up. Whip them out and clean them off. We try again, and it attempts to fire. Not long now, and then it sucks in a decent drop of air-to-fuel and she's away!
I get excited at this sort of stuff. The years of lying dormant, destined for the scrapyard, but she lives again (yes, it's taken on the female gender now). Smoke begins to bellow out the pipes as they warm up - probably the squirts of oil pumped out of the bores getting burnt off. The engine itself sounds pretty good, slight cam chain rattle, but it selects all six gears and even the gear indicator on the dash is working. The bike is so quiet! The silencers are very impressive.
I have something to work with now. The carbs need the correct jets and needles putting in, but otherwise they seem fine. The top-end will need a refresh because the bores were probably covered in surface rust, but at least it sounds like the crank etc. are nice and quiet.

I put some injector clean in the tank with the fuel so, if it does do anything, it'll be getting to work on any internal varnish in my carbs that hasn't been cleaned. I start it every couple of weeks now, just because I can, and it fires up instantaneously. Happy with that, and carbs look reasonable enough too. No expensive solutions or ultrasonic cleaners, just done the old-fashioned way.