Kdx idle issue

[JZ05220r]

I have been riding my 91 200 a good bit recently and I am noticing an issue with the idle. I start the engine and let it warm up revving it every few seconds. After a few minutes the idle starts to drop lower and lower until it’s basically loading up and nearly killing the engine. When warm it’s just as bad. I notice when I turn the gas off the problem goes away within a minute as the fuel supply gets closed off from the bowl so it’s obviously over fueling. When I turn the gas back on, immediately it starts to load up and nearly die. Doesn’t get better no matter how hard I ride or try to clear it out. I am confused because I didn’t notice this with the bike running the stock rich jetting, stock needle, 48 pilot and 155 main. Now I am set up with a 40 pilot, CEL needle, and 152 main. It is now doing this with the stock jetting as well. What could possibly be the cause? It was not an issue before. I did put another float valve in it that I had lying around and didn’t see a change. Thank you guys

[bufftester]

Make sure to set the float to 18 mm (works better than the stock 16) and inspect your float valve and seat. Might also give the carb a good clean and make sure all the air passages are clear.

[JZ05220r]

Make sure to set the float to 18 mm (works better than the stock 16) and inspect your float valve and seat. Might also give the carb a good clean and make sure all the air passages are clear.

Ok. I do have it set to 18mm. I will take a look at the seat and polish it up it need be. I know all the breather lines are clean. Would be interesting to use the clear tube float height method while the bike is running and do what I described in my original post and see how the fuel level changes and where the sweet spot is. Thanks

[JZ05220r]

Checking and polishing the float seat was no help. I cleaned the carb thoroughly. I’m stumped. It was just idling beautifully a few weeks ago. I understand it’s alittle pathetic to be whining about the idle but it’s definitely an issue for me. Could it be the damn gas station I have been going to? This started happening after I got some gas and mixed 40:1 like I always do. I had this issue with my other kdx as well.

[SS109]

Possibly fuel. Try draining out what you've been running and then run some fuel from a totally different company.

[JZ05220r]

I picked some up last night from a different station. Will try after work.

[JZ05220r]

Today, after filling up at a different station all the idle trouble went away. There was no change in the idle issue the handful of times I spent messing with it until today with different fuel. Still gonna keep an eye on it but I think this was the issue.

[bufftester]

Entirely believable. Some stations and brands have a lot more ethanol than what is usually posted on the pump. And in spring and fall they change their "blends" from winter to summer and back, I have seen fuel issues spike around those periods with the group I ride with. Lucky enough to have a VP station near me, never had any trouble with their fuel.

[KDXGarage]

Congratulations on getting it sorted!

Bufftester, I am jealous of you having a VP station. :-)

[JZ05220r]

Entirely believable. Some stations and brands have a lot more ethanol than what is usually posted on the pump. And in spring and fall they change their "blends" from winter to summer and back, I have seen fuel issues spike around those periods with the group I ride with. Lucky enough to have a VP station near me, never had any trouble with their fuel.

So you can get ethanol free fuel straight from the pump? If so their is one about a half hour from me. I’d definitely make that drive and buy a couple extra gas cans if that’s the case.

[SS109]

The ethanol wasn't the direct issue with the fuel but probably a contributing factor. The fuel clearly had water in it which the ethanol attracts and that was what was affecting your idle. Going from 10 to 15% ethanol fuel won't affect our bikes much. 15% is the legal maximum in some states and it has to be clearly stated at the pump dispensing it.

If jetted correctly, which can't be done with our OEM type carbs (large enough jets are not available), you could run our bikes on a pure ethanol/oil fuel mix without issue. You could actually get even more power than a standard gasoline/oil mix run engine as you can take advantage of the cooling effect ethanol has and increase your compression ratio significantly.

While I'm not a fan of ethanol, it is not the devil that most think/claim it to be.

[JZ05220r]

The ethanol wasn't the direct issue with the fuel but probably a contributing factor. The fuel clearly had water in it which the ethanol attracts and that was what was affecting your idle. Going from 10 to 15% ethanol fuel won't affect our bikes much. 15% is the legal maximum in some states and it has to be clearly stated at the pump dispensing it.

If jetted correctly, which can't be done with our OEM type carbs (large enough jets are not available), you could run our bikes on a pure ethanol/oil fuel mix without issue. You could actually get even more power than a standard gasoline/oil mix run engine as you can take advantage of the cooling effect ethanol has and increase your compression ratio significantly.

While I'm not a fan of ethanol, it is not the devil that most think/claim it to be.

Interesting, thanks for that info. The tanks also must be pretty old as the station has been there for as long as I can remember. Probably been a gas station there since the 70s. That’s not to say the tank hasn’t been replaced since then. The bike is running great through the rpm range. Super fun to ride. Alittle too smokey only when getting on it hard so I will be working down on the main jet. I’ll keep an eye on the idle moving forward but the difference is night and day compared to how it was acting a day ago. Oh and I’ll have my cylinder back for the 220 in a few days. I’m going to take my time setting up the KIPS. I’m going to polish all of the riding surfaces the best I can with a dremel and extension to get in there deep. Can’t hurt I imagine?

[SS109]

Awesome! be very careful when polishing the exhaust ports. If you change their size in any way where they enter the bore of the cylinder it will change how the engine runs. Anything after the openings to the bore can be polished without much worry as long as you don't go grinding them out bigger.

[JZ05220r]

Awesome! be very careful when polishing the exhaust ports. If you change their size in any way where they enter the bore of the cylinder it will change how the engine runs. Anything after the openings to the bore can be polished without much worry as long as you don't go grinding them out bigger.

Good to know. Also I am actually going to leave the ports alone. But what I really want to focus on is where all of the kips parts are making metal to metal contact. Thanks!

[SS109]

Awesome! be very careful when polishing the exhaust ports. If you change their size in any way where they enter the bore of the cylinder it will change how the engine runs. Anything after the openings to the bore can be polished without much worry as long as you don't go grinding them out bigger.

Good to know. Also I am actually going to leave the ports alone. But what I really want to focus on is where all of the kips parts are making metal to metal contact. Thanks!

I hear ya. You're doing the KIPS bores.

I always thought about sending out my KIPS subvalves and flapper valve to have an anti-friction coating applied to them. The coating would also help keep carbon from building up on them so it would extend service intervals. Sadly, never got around to trying it as the coating is not cheap but thought it very well might be worth it.

[JZ05220r]

Awesome! be very careful when polishing the exhaust ports. If you change their size in any way where they enter the bore of the cylinder it will change how the engine runs. Anything after the openings to the bore can be polished without much worry as long as you don't go grinding them out bigger.

Good to know. Also I am actually going to leave the ports alone. But what I really want to focus on is where all of the kips parts are making metal to metal contact. Thanks!

I hear ya. You're doing the KIPS bores.

I always thought about sending out my KIPS subvalves and flapper valve to have an anti-friction coating applied to them. The coating would also help keep carbon from building up on them so it would extend service intervals. Sadly, never got around to trying it as the coating is not cheap but thought it very well might be worth it.

Thats a great idea.

[JZ05220r]

Oh I have a can of berrymans carb dip. Would it be a bad idea to soak the kips parts in there to help clean them?

[SS109]

Oh I have a can of berrymans carb dip. Would it be a bad idea to soak the kips parts in there to help clean them?

Won't hurt them as far as I know.