Aug 4, 2018 - Carburetor problems generally fall into three areas: too lean a mixture, too rich a mixture, or an incorrect adjustment. Luckily there are telltale.

1. Cvk Keihin Carburetors Diagram

I never hear anything about the CR round slides on here. No performance gains?

No better throttle response? Or do people just not know about them? Same goes for FCRs or Mikuni RS.

I dont think there is a plug and play kit for FCRs or RS's for the EX but I would assume someone has tried them. There sure is a lot of stupid modification / money wasting from people on this forum that I would think better carbs would come before leds, turbos, and body kits?I couldn't agree more that this forum is quickly turning into an led light mod forum. That and which noisemaker is the best. And we all know the ex500 community generally speaking doesn't have two nickles to rub together. I've never even imagined a more frugal group of people in my life.

I'm far from an expert, but it seems that these are budget bikes without many easy upgrades that significantly increase power. For most parts, the question ' What should I upgrade to?' Is answered with ' There isn't really anything that performs better than stock.' Based on what people like FOG say, there simply isn't that much headroom left in the engine for increasing performance; it's not that the is too small, it's that the engine is pretty much maxed out already, so a bigger doesn't really help anything.

Every factory vehicle has compromises to meet budget and legal requirements. I'm sure there are many parts that can be improved over stock. The FOG airbox mod is one basic example. However, it comes down to how much improvement you get vs. How much you spend on the improvement. I just found for $500-$600 (depending on specifics).

I honestly don't know enough about carbs to know if that would be an overall improvement (for street or track). However, that's a pretty good chunk of money (10% of the cost of a brand new bike, more than some people paid for their used bikes). Are you really going to get a 10% improvement over stock with that? Maybe if you spend a few hundred more on an exhaust and jet kit, it might help more.

Cvk Keihin Carburetors Diagram

Now you're up to $1,000+ spent and how much better is the bike? I'm not saying that everything's been done and there's no way to improve anything. However, it seems like the relatively cheap, easy basics have all been tried over the past 25 years and don't significantly improve things. When you factor in the price and role of the average EX500, it's just not worth it to spend so much money for such small improvements. It might be different if it's an old trashed bike where everything needs to be replaced anyway or you're racing professionally and looking for every last tweak to wring an extra drop of power out of it.

Personally, I think my biggest dream is fuel injection. In my eyes, carbs are cheap and 'good enough', nothing more. Once you understand FI tuning, it's so nice to work with. With a computer controlling it, you can adjust the fueling for a multitude of engine loads and speeds. Whereas there are a couple ways to adjust how much fuel a carb injects, FI allows for nearly infinite adjustment.

The biggest issue with putting FI on an EX500 is probably retrofitting all the electronics and sensors needed to give the computer good information to base its fueling on. Again, with all the time and money it would take to set things up right, sticking with the cheap carbs seems like a better value, even though I know FI would be much better.

On the carb kit. Yes they 'work' Funny thing to say. They just lay there unless you do something. But you need a new float needle and a gasket so I guess they 'work' To Invisabil: Your verbose statement above is what I've been screaming about on this forum for 10 years. Nice bike if left unmolested. FI is just a way to better control emissions on this bike without a re design of the combustion chamber and cam timing it would be a waste of $ just like all the rest of the mods.

Cost effective is the word of the day. Even for my race bike where cost was no object, there was nothing to be had.

Front view, compliance fitting side. Left side view. Aft view, branch tubing or intake side. Right side, idle adjustment screw can be plainly seen. Top view looking at diaphragm cap. Bottom view looking at carb bowl drain.

Tools needed to work on Keihin carb. Optional Pin gage set show below is available from When working on the carb, drain the fuel from the bowl.use a 3mm Allen wrench to crack the screw open.catch fuel in a clean container and check for contaminates. You are looking into the front of the carb, the back plate with 2 screws is the butterfly valve. At 6 o'clock in the mouth of the carb you can see the end of the idle mixture needle poking up. Try not to damage it!

The idle mixture screw adjustment is underneath the carb. Turn the screw very gently CW until you just meet resistance.any further and you will damage the needle. Factory setting is 1.5 turns CCW from seated. If you remove the needle these are the pieces top to bottom. O-ring, washer, spring and needle. Be very careful not to lose or damage the rubber O-ring!

Many times it will remain up in the carb, turned sideways and get crushed when the needle is driven home. Then you are buggered.

If you use a long shank Philips screwdriver to break the bottom float bowl screws loose.you won't bugger the heads. Well, some of you will anyway. Clean any crud from the bowl with solvent. With the float bowl removed you can now see the.float.float needle.main jet.starter jet.and idle jet. To remove the float and float needle, use a toothpick.to push the pivot dowel out. Lift the float with needle attached out. The needle has a wire loop which slides over the float tab.use caution as it falls off easily and can be damaged.

Careful of the tab also, if bent it will change the level of fuel in the bowl. To remove the main jet, hold the air tube steady with an 8mm wrench and use a flat blade screwdriver to unscrew the main jet.

If desired, you can remove the air tube and main jet as one unit. Main jet removed. Now remove the air tube with the 8mm wrench. If you are doing this on the bike expect the needle jet to drop free. Have a towel down to catch it. If the carb is free, hold it right side up and catch the needle jet in you hand. There are two distinct ends to the needle jet.

This end goes in first. The rounded end.goes against the air tube you previously removed. Way down inside here.is the idle jet.

It takes a long thin flat blade screwdriver to get it out. It like the rest of the jets is soft brass. You will be removing it blind so take your time and don't bugger it up. Clean all orifices of each jet regardless of whether you 'think' they look clean or not. You should use Pin gages so you don't bugger the orifices but if you carefully select some soft wire you can do a decent job.

Upon reassembling, don't swap the idle and main jets.it can be done. I use a little silicon grease on the float bowl O-ring just because. The top end of the carb only needs to come off for two reasons. First, suspected hole/tear in diaphragm. Second, if you do something like submerged your engine in water. If you pop the top, use a long shank driver to prevent stripping the screw heads. Top cap off.allows you to remove the spring and needle holder.and the diaphragm/slide and needle.

Caution again.the needle is not secured and can fall out if slide is inverted. If the needle or diaphragm gets damaged you are hosed. A little difficult to see in this picture.but the slide is off set and only goes into the carb body one way.don't force it.it should drop right in. A view into the carb body.the slide off set is rather slight and might be overlooked. Keeping the diaphragm from popping out of the groove can be a challenge.especially if doing this on the bike. A little silicone grease in the groove helps hold the diaphragm down.

Nine times out of 10 the diaphragm should go in with no trouble. Much easier off the engine. Place the slide needle into position.and drop it home into the needle jet. Drop the needle holder and spring on top of the needle. Place the cap on being sure to get the spring over the keepers under the cap. Put the screws back in and you are finished.

Here's a view with the needle removed showing the needle jet in the mouth of the carb. Opening the butterfly valve with the thumb plate. Choke pulled on opening the enrichener orifice top right, inside carb. Choke closed. Vacuum port cap. Cap removed exposing port.

This is where a carb sync'ing device would be hooked up. Idle adjustment screw and thumb plate. On the throttle cable bracket the portion from this seam up can be cut off as it is not used.