Engine revs up when bike on side stand or leaned over

[Clint vB]

Hi All



New to riding, new to posting in forums and 1st time working on my own toys.



I just purchased a very good condition 2006 KDX 200. My carb was overflowing so I pulled it off, gave it a good clean, replaced float valve and set float height to service manual spec (needed to be lowered slightly). Also, have air screw out 1.5 turns. I reinstalled everything and started the bike whilst it was in an upright position, then adjusted idle screw until I got a nice idle. The problem is when I lean the bike over to rest on the kickstand it starts revving very high. I then adjust the idle screw again while on kickstand to get a nice idle, then when I lift her up back to upright position she idles very low and then stalls in about 15seconds.
The tank was not removed during the process and I am keeping the handlebars straight at all times so I don't tug on any cables.


She was running perfectly fine before I done this, except for the carb that was overflowing. Could I have possibly set the float slightly too low and when the bike is on the stand the engine revs up because it's running lean due to lack of fuel? (not 100% sure what to expect from a lean or rich running motor). I was aiming for the lower end of the float height to avoid the overflow, however, now that the float valve was replaced maybe I should return the float level back to original position? I'm thinking maybe the float valve was causing the overflow and not the float height to begin with.


Hoping someone with more experience can give me some advice.

[KDXGarage]

Sorry to confirm your suspicions, but it is indeed time to re-re-adjust the float height.

A two-stroke dirt bike is usually not the champion of idling anyway.

[Clint vB]

Thank you for the swift response, I'll re-adjust this weekend and report back.
Would like a perfectly running bike for my next Funduro on 4th September.

Thanks for a great forum, been reading it for the last 10months and finally joined yesterday. Received your welcome message AND thank you for allowing me to participate

[KDXGarage]

Hey, thanks for asking easy questions. :-)

Have fun at the funduro.

[Goofaroo]

Are you sure you aren’t getting a “false” idle setting because your throttle cable doesn’t have any free play?
Are you sure it’s routed properly?

Fire it up and turn the bars from lock to lock and see if your idle fluctuates.

[SS109]

Yep, I bet the problem is the throttle cable. I set the float height to 18mm and not the factory 16 and never have high idle issues. I highly recommend setting your float to 18mm as it helps keep your bike from peeing while leaned over and from giving a false rich running condition which can make jetting a nightmare.

[Clint vB]

Thanks for all the responses. Much appreciated. I will definitely check all the above this weekend.

[Clint vB]

Hi guys

Just wanted to provide an update. I lowered the float level slightly at first which didn't make a difference. On the 2nd attempt I lowered the float quite significantly {allowing more fuel into bowl} which resolved the issue with the idling. There is a drop of fuel every few mins from the overflow which means I probably set it just a little too low, however, I am grateful that the root cause of the idling issue was identified and resolved, I can now ride comfortably. I will make a tiny adjustment to the float again if it continues to leak after a few rides, it's literally one drop every few minutes. I am a perfectionist though so will monitor it closely.

Thanks for all the tips, I'm happier than a pig in Palestine.

[Goofaroo]

If it’s dripping at all it’s most likely that your needle isn’t sealing. I usually put brass polish on a q-tip, chuck it up in a drill, and polish it up thoroughly. Thoroughly clean the seat and the needle and reinstall. You can bench test by attaching a piece of fuel line to the fuel inlet and blow into it while holding the carb upside down. It should hold pressure. Flip it right side up and you should be able to blow through it.

It’s hard to say what’s truly going on with your “custom “
float level but I frequently “fix” float valve issues with a brisk ride over some rough terrain. It will sometimes dislodge whatever debris is causing it not to seal. If it is dripping out the overflow your fuel level is too high. If the float valve is leaking your float height is irrelevant.

With what you’ve told us if you brought your bike to my shop I would pull the carb, clean the needle and seat, set the float height to factory specs, bench test the valve, and reassemble expecting it to run just fine.

Just my $.02.

[KDXGarage]

yep, always good to check the float valve needle and seat

good reminder!

[Clint vB]

Hi All

It's a brand new OEM float valve, I noticed the tip is much sharper than the old one. I have cleaned the seat numerous times with carb cleaner and a rag but will try the q-tip idea as well if need be. PS: it's dripping out of the overflow after I lowered {or raised, depending how you look at it} the float to allow more fuel into the bowl.

[SS109]

Why would you raise the fuel level? Like I mentioned earlier, it causes a rich running condition which makes getting your jetting spot on rather difficult and it can drip while on the kick stand or while leaned over in a turn when riding. Set it 18mm and forget about it.

[Goofaroo]

Hi All

It's a brand new OEM float valve, I noticed the tip is much sharper than the old one. I have cleaned the seat numerous times with carb cleaner and a rag but will try the q-tip idea as well if need be. PS: it's dripping out of the overflow after I lowered {or raised, depending how you look at it} the float to allow more fuel into the bowl.

If your needle isn’t sealing it makes no difference where you set the float. It will never shut off the fuel at the correct level.

Clean it again, set the float to the correct height,
bench test it, and ride off into the sunset.

[Slick_Nick]

Yeah you shouldn't keep raising the float level if you're having issues. Set it to 18mm and leave it there. Then figure out why it's not shutting off at 18mm. Polish that seat, or maybe it's worn to the point of replacement. It's "non-servicable" according to Keihin, but you can remove the old one and have a new one machined and pressed in for cheaper than a new carb.

[Goofaroo]

Yeah you shouldn't keep raising the float level if you're having issues. Set it to 18mm and leave it there. Then figure out why it's not shutting off at 18mm. Polish that seat, or maybe it's worn to the point of replacement. It's "non-servicable" according to Keihin, but you can remove the old one and have a new one machined and pressed in for cheaper than a new carb.

Yep. It would be very unusual for the seat to be damaged that badly but it is feasible.

I have almost always gotten them to seal with a q-tip and brass polish. In a few cases where that failed I have used very fine lapping compound and gently lapped the needle to the seat just as you would lap in a valve. I slide the needle into a piece of model engine fuel line and apply the compound to the tip of the needle and gently lap it in.

One more thought- If he is using an aftermarket carb kit the needle may be slightly different and unable to seal. I have had problems with aftermarket kits (such as Keyster) on several occasions. Not only with the needle but also with the jets. The pilot jets in those kits are often an entirely different style than the original. I still buy those kits from time to time but only use the gaskets and o-rings. I always use use all of the original brass whenever possible.

It would certainly be worth a try at this point to polish the seat and clean the original needle and see if it fixes his problem.

[John_S]

Good idea to recommend the polishing of the seat. He mentioned in one of the posts that the float valve is a new OEM piece. I bought a brand new PWK 35 that would leak overnight on the kickstand and was rich down low. Set the float to 18mm and polished the seat with a Q tip, Mothers, and a drill and its been good for years.