High Rev Closed Throttle

[petro]

Hi all! I'm new here and just bought a k5 about a month ago. I have run into a couple things I need some clarity on. First off I was out riding this past weekend when all of a sudden I came up on the mother of all washes and needed to come to an abrupt halt! Well pulled in the clutch and slamed on the brakes but the rpm's were pind. I played with the throttle figuring the slide was stuck. Well I soon noticed that the bike was lurching when riding after that. Also when pulling in the clutch after wot the rpm's took a while to wind down. I thought of a couple possible things. 1) Dirt in carb 2) Air leak. Looking at the carb after the ride there is a lot of dust on it as if fuel is leaking and the dust is sticking. Same thing on reed cadge. Any ideas what it may be and what to do. Thanks. Oh by the way bike is a 94 5hundo (of course) with a fmf pipe and silencer, stock engine.

Mike

[KXcam22]

Mike,
  That reving is mostl likely caused by a too lean condition.  It can come from an air leak somewhere or from starving for fuel.  As a suggestion heres where I would start:

1. verify carb jetting (with the chart on the site) for your elevation and set the float level.
2. inspect the base gasket, reed gasket and carb clamps.  On my 92 I didn't like how the stock carb clamps worked so I replaced them with std automotive hose clamps.

Being it is fairly new to you it may be worth pulling off the reed valve and replacing the gasket plus it is cheap insurance.  On important gaskets like base and reed I like to use a gasket cement (like pematex motoseal - cheap & good) to coat the gasket to ensure that no air gets in.  Hope this helps. Welome to the site. Cam.

[petro]

As far as the base gasket goes are you referring to were the jug and the crank case meet? I'm going to tear down the carb and the reed cadge and check jetting. First I'm going to clean and spray some break cleaner on and around the intake and reed box while the bike is running at operating temp to see if she revs up when hosed with brake cleaner. Do you have any sug about v-force 2 or 3 which is better? Think I might up grade while apart need some more power raced my buddies 450 and we were neck and neck. Dunes for thanksgiving gotta smoke the 4stokes!!!

[Motorrad]

Check the gaskets by starting the bike.   Then spraying somthing lie carb cleaner around the base gaskets.  Head gaskets.   IntakE gaskets.    If it dies. Or changes the way it's running.  Check given gasket.   (make sure you check the entire gasket. Not just one side

[Hillclimb#42]

They will also rev like the way you describe, when they start running out of fuel. I.e. clogged fuel line, petcock or carb issue. Idle screw turned way in caused mine to have extra run-on after I shut the throttle off, too, but not really a high rev.

[petro]

Ok so I checked for air leaks via the method described and all checked out to be fine. I did however find some interesting lube on the slide in the carb. I'm guessing this is a graphite lube. Is this a common thing to do. I have never seen nor done this before to a slide. The slide did however look a little worn especially on the bottom corners. I'm guessing this may have been a solution to a problem the previous owner had. I also noticed that the clip position was 2 from top. Its supposed to be at the 3rd from top right? Making the lean condition I was describing. I moved it rejeted and did a plug test. Looks perfect nice tan color. The previous plug was black but not wet (lean condition right?) Seems as if slide is still sticking though. I guess my question is whats up with the white lube on slide? Good or Bad?

[KXcam22]

Petro,
 Black plug is rich, white plug is lean, medium tan to dark brown is good.  The lube on the slide may have come from pressure lubing the cable, or the PO used lube on the slide.  I have never done that.  The slide will always look a little worn but it is never enough to cause sticking (that I have seen).  The mechanical things that usually causes sticking are the cable itself sticking or the throttle tube not returning.  I have once seen engine vibration do that.  A broke head stay caused the motor to vibrate side to side which caused the slide to bounce side-to-side and not return right away. Rare.  After that it is usually causes by a lean condition.  To go further on this you need to post your jetting and elevation.  If your pilot jet is too lean or partially plugged it can cause this.  Generally the needle is not the culprit.  Hope this helps. Cam.

[petro]

Original setting from PO......

168 main
55 pilot
needle pos 2
air screw 1 1/2 turns

Problems.... Black plug, lean conditions, chocking, rpm took while to drop after wot and pulled clutch. Oh and i guess white lube s**t all over slide.

The white lube was that of graphite. I have heard of it being used before just never seen on dirt bike.

What I have done......
Checked for air leaks..... None
Cleaned carb rejeted
Main 165
pilot 55
air screw 1 1/2 turns
Clip pos 3
cleand white crap off slide
lubed throttle (properly)
Elevation 1,000ft temp this time year about 70-80 dry air
results.....

Tan plug reading with great throttle response and power
Just the right amount of pipe smoke from exhaust
Slide still sticking guess this is the prob which is causing long wind down and screaming when throttle is closed. No brainier!!!!


It seems as if the needle position adjustment (richer) with a tad bit leaner jet solved black plug problem.
Going to dunes in 2 weeks dont wanna have wot when Im not asking for it!!!

[Hillclimb#42]

Have you checked the throttle housing? If the tube is too far in the grip will drag, I've had cracked throttle tubes, the little cable wheel on the Housing, needs to be clean and free. I don't lube throttle cables, myself. It will run into the top of carb. It should be snapping closed "Whack" Should have some slack, too. Is graphite white? Sounds like grease, or water and oil product.

[KXcam22]

Petro,
  Excellent. Thats the detail I was looking for.  For 1000ft the 55 pilot is likely too lean.  I ran a 55 at 3000' and it got too lean in cold weather and would rev up like you are describing.  I would suggest trying a 58 (60 is stock and too fat everywhere).  Your other jetting is good.  Cam.

[petro]

Thanks for the guidance guys.... All is fixed and she sounds and runs f**kn awesome. The richer pilot and needle position helped solve part of problem. The other half of the problem was dicovered when I removed the gas tank and discovered that the PO routed the throttle cable all crazy likely getting pinched between tank and frame. Has me wondering what the hell this guy was thinking between the carb settings which were way off and the little attentions to detail that were looked over. Scary!!!!!!!!!!!!!!!!!! 

Happy Thanksgiving

Ride Fast

[KX5MOD]

Let us know how you make out against your buddies 450 now 
I have a sick modded K5 that just dusts 450's like a joke, & a bone stock one that beats them everytime as well.....second gear starts---to well past top out.

[Polar-Bus]

Thanks for the guidance guys.... All is fixed and she sounds and runs f**kn awesome. The richer pilot and needle position helped solve part of problem. The other half of the problem was dicovered when I removed the gas tank and discovered that the PO routed the throttle cable all crazy likely getting pinched between tank and frame. Has me wondering what the hell this guy was thinking between the carb settings which were way off and the little attentions to detail that were looked over. Scary!!!!!!!!!!!!!!!!!! 

Happy Thanksgiving

Ride Fast

Pilot jetting plays a pretty substantial role in overall jetting, and the reason being is that no matter what tune you have the pilot circut, that tune also affects the entire carb jetting spectrum as well. Pilot jetting mainly is noticable from "closed" throttle to 1/4 throttle. But the pilot jet is still feeding fuel even at 3/4 throttle. I like to adjust my engine for a temporary idle, and just listen to the idle quality. If I hear the idle slowly rise, this is lean, and you need to richen the pilot. If you have a decent idle, and you hear the engine rpm's slow, and the engine sounds rough, this is the engine loading up and your a bit rich. This is my personal crude method, but it's worked for me for years. Sometimes you can achieve results juts by adjusting the air screw, but other times a jet change is required. You generally want your air screw to be able to maintain a clean idle between 1.5 and 2.5 CCW from seated.  If you are out of that adjustment range on the air screw, that means you need a corrective pilot jet change. You can read for days about 2 stroke jetting, but your best jetting tool is a keen ear, and feel. Takes much trial and error practice. (I still after 22 years don't have jetting perfect, but I get my bikes very close)