When do I know I am experiencing valve float?

[napalmfire]

I now notice myself experiencing what I think is valve float where the engine was revving higher but then dropping back down over and over again. I'm sure this is probably bad for the engine, correct? Anyone know how many rpm's I must be pushing based on the sound of the video below, and the fact that my valves are probably floating on stock springs? I only did this I believe twice so far(the video and my top speed 41mph run) and realized what must be happening. waiting on a response to see what to do. I'm going to have to get a billet rod and flywheel before I am to get better springs imo.

If you can figure rpm's based off of ratio, Here is my gearing info:

12t Clutch
70t Drive sprocket
14.5" wheels

http://smg.photobucket.com/albums/v347/Napalm_Fire/?action=view&current=0813091644.flv

 

[anderkart]

The link to your video doesn't seem to be working.

 

[napalmfire]

http://smg.photobucket.com/albums/v347/Napalm_Fire/?action=view&current=0813091644.flv

Revised it. There ya go.

 

[anderkart]

Sounds like it runs really good and you got it wound out pretty tight there but I couldnt tell if your valves were floating or not. (I supose the fuel mixture could just be leaning out at that RPM to)

If you can figure rpm's based off of ratio, Here is my gearing info:

12t Clutch
70t Drive sprocket
14.5" wheels

top speed 41mph

I entered your info into this gearing calculator: http://www.gokartracing.org/Calculate.htm and came up with 5600 RPM at 41.36363636363637 MPH. I had to convert your 14.5" wheel measurement to a circumference size. (you might wrap a tape mesure around the center of your rear wheel to get a more accurate measurement and then recalculate) On this calculator, I just entered your sprocket sizes and rear tire circumference and then clicked on the RPM higher/lower buttons to come up with a match to your claimed 41 MPH top speed.

If all the info you listed is accurate, I'd imagine you probably are floating your valves.

I couldnt tell what kind of engine your running, but you'll probably find lots of hard core race motor (and valve spring) info for it at this race kart forum:
http://karting.4cycle.com/forumdisplay.php?f=1
http://karting.4cycle.com/forumdisplay.php?f=71

 

[jr dragster T]

Sounds like its going lean.

 

[napalmfire]

It's a honda clone, HF 6.5hp.

Should I jet it out one size larger?

I probably will get a flat top piston and rod first. When should I look at getting a new flywheel? I suppose as long as I dont keep it revved for long, I should be ok with this, yes?

 

[jr dragster T]

I wouldnt worry a whole lot about your flywheel on a mild motor. If you have a header on that engine I'd say opening up the main couldnt hurt.

 

[anderkart]

^

 

[solomon]

Typically valves float after 6000RPM so its probably not valve float. Just use exhaust spring on the intake and you will be fine if you are concerned. It honestly sounds like ur mixture is off is all.

 

[jr dragster T]

Typically valves float after 6000RPM so its probably not valve float

On a stock clone? They seem to be floating at around 5500-5800.

 

[solomon]

huh. well it doesnt sound like it at all. like i said exhaust sring on intake will stop any valve float

 

[napalmfire]

Ordered some 18lbs so if theres any float, it'll be gone for sure.

Also ordered a flat top piston, billet rod, and UNI air filter off of AGK. Should be here by Wednesday at the latest!

I should probably bump my timing, correct? Where do I file off of the key? I have digital calipers so I can tell exactly how much I am taking off. Any pics of before and after would be great.

 

[jr dragster T]

You want to advance your timing correct? If so this is how its done the cheap way. Put half of the key in a vice and file the backside of it (To rear of engine if installed) with the bottom of the file resting on the vice jaws. Every 0.006" is equal to 1 degree. When installing the flywheel rotate flywheel forward (Advanced) till it hits the step in the key and torque down the flywheel. I've succsesfully made many advanced/retarted timing keys this way. Sorry, I dont have any pictures.

 

[mike75925]

the fly should be rotated clockwise to meet the key. correct?