tools for cleaning carb jets?

[p5200]

Hello, would something like this work for cleaning jets in a MIKUNI BST40-251 carburetor? If not, suggestions would be appreciated I'm wanting to put an OEM rebuild kit in the original carb and put it back on my 2005 500 Scrambler 4x4 Thanks! 🙂   Tool Shop® Standard Tip Cleaner at Menards®

[geezer99]

I've been cleaning carburetors for the last 60 years.  Compressed air and broom straw following a soak in carb cleaner are my goto methods.  I have never had gunk so stuck in an orifice that it needed a gas welding tip cleaner or a drill.  The tip cleaning kit you show would work fine, but you will need to be careful not to over-do it for risk of enlarging the orifice.

I have used drills to enlarge jets, mostly with poor results.  Most engines seem to run best with the factory size jets.  Hopped up engines are a whole different story.  I have been satisfied with factory performance, but I respect the folks who like to hot-rod their equipment.  I knew a guy that built sand rails back in the early 70s.  He souped up everything, and nobody could come close.  I remember he rebuilt a rear end out in the dunes at sand lake on the Oregon coast.  He practically had a service station in his trailer.

tom

 

[Mech]

No Ps, those are for welding tips and they are like tiny files. Don't use those.

If jets are dirty it's nearly always a lump of dirt or bit of fluff and you can see it if you hold the jet to the light. Most things can be blown out easily. Sometimes the jets get a build up of verdigris which doesn't blow out, and people use chemicals, but I just use any small bit of hardwood whittled down to a fine point to ream then out, and then give them a blow through and reinspect against the light. It's important to take out the emulsion tube, which is the brass tube the slide needle drops into. A few taps from the top with the handle of a small screwdriver and it comes out the bottom. It has several tiny holes halfway up the tube that need a good blow out because they are too small even for a whittled down bit of wood. Don't try cleaning them with a pin, a single wire from a wire brush some times fits nicely but they mustn't be enlarged or distorted.. or blocked with a tiny point of whittled down wood !!  The holes in the tube are arranged on opposite sides of the tube, so you can look right through if you are very careful, and you will see light if they are all clear. The drilling in the carb body that the emulsion tube fits into, is a precise diameter and volume and needs to be cleaned out of it has a build up of chalky or gummy crud..

Apart from the fuel jets there are air jets near the air-cleaner end and some of those can not be removed, and even the ones that can be removed don't really need to be taken out. They are so big you can see and blow straight through them. Blow every passage you can in the carb body, in the opposite direction to normal fuel or air flow, as much as possible. Blow a little one way to see where it comes out before blasting it through from the other way. The idle discharge holes are the smallest passages in the carb body.. Try not to force any fluff or dirt up towards them by blowing from below. It's awkward, but best to open the butterfly or take the slide out, and blow down through the idle discharge holes as best you can, before blowing back the other way from below.

If you have compressed air it's a good thing to make a long tipped air nozzle out of four mill steel brake pipe. It's handy for getting down the hole where the slide drops in, and blowing the drillings there or under the butterfly.

 

[p5200]

That's a lot of valuable info there, I'll try my best to follow it Thanks! 🙂

[p5200]

I guess the emulsion tube just pushes back into place to put it back in?

[JSL]

I agree with geezer99. Also you can use electrical wires. Such as old electrical cord. Just strip the wire and unravel. Then cut a small strand. NEVER force anything through a jet. Doing so may enlarge the jet opening.

[Gwbarm]

I do pretty much the same procedure except, what I do before I ever open the carb up is clean all the dirt trash and mud off of it in the parts washer, get the outside very clean , you don't want any of that getting inside your carb, or the ultrasonic cleaner, ultrasonic is generally not necessary for a carb off of a running bike, they are usually fairly clean with a stray piece of dirt blocking the jet openings, unless it sat for years before you got it. I just do it incase there is a small piece you didn't see or come loose from the carb cleaner. I used to use the electrical wire method but was always loosing my wire so I got a set of jet cleaners , a bunch different size wires all attached like feeler gauges. I got 3 cause I knew I would loose I right away, and I did. I also don't use strong chemicals in the ultrasonic cleaner, I used to use carb dip, never really liked it, it would always turn the metal a darker color. I use Simple Green or Royal Purple or something along that line, I have even used Dawn dish detergent and I think it works just as well. Mech covered the tear down really well, and everyone has their own procedure, but this is what I do.          

[Oldguy]

A few months ago, I helped a friend clear the pilot circuit on a CT70 carb. Similar to a TRX70. The passage to the idle mixture screw and outlet were clear, but the outlet just behind the back edge of the throttle slide was blocked when we tested the circuit by spraying carb cleaner through it. I took a fine wire from a welding tip cleaner set and pushed it down into the port. I could feel some resistance and then it pushed through. I don't recall if we saw the dirt that was obstructing the port, but the engine idled and accelerated normally after that. I think it is VERY important to test the passages by spraying something through them before giving it back to the customer. And don't forget to check that all if the air jets are in place too!

[Mech]

Yes that second idle discharge hole is very important. It starts off diluting the mixture when it's idling, but then turns into a discharge port enriching the mixture as soon as the throttle is opened a little amount. It's an important part of the acceleration process and if it's not right, or if the throttle is too far open when you adjust the idle mixture, it will cause flat spots.

It's not a good idea to use welding tip cleaners though..  that initial resistance you felt Oldguy, may have been aluminum being chewed away.. and we really don't want to enlarge that hole..

[Oldguy]

Mech, the tip cleaner I used does not have serrations all the way to the end of the wire, so I'm sure I just pushed out some chrud blocking the passage. 

American Honda power equipment lists a carb tip cleaner set that looks a lot like welding tip cleaners, so I'm not so keen on banishing them from anyone's toolbox, but having said that I do think that they can be miss used by novices who don't understand the how sensitive jets are to modification. I'd much prefer to replace it with an OEM jet of the same size or a different size if the engine has been modified. I firmly believe in letting the engine tell us what it wants in the fuel system. I do that me riding the vehicle and doing a spark plug color check. 

[Mech]

That doesn't really inspire much confidence in American Honda power equipment then..  haha.