kx500 outlaw kart motor

[sandblaster]

Ok.. the 3 tracks within a 70 mile radius of me are all 4th gear only (Or some use 2nd only in their CR500's  ) .
I don't know anyone who is shifting at any of these tracks.

Anyhow I wouldn't abandon your center flapper if your cylinder is a 89 and newer.
Having the longer usable power curve gives you a advantage over the CR500's.

Find some heavy duty clutch springs to help keep your power on the ground and not slipping the clutch 

On the vid I posted earlier, if you can get the measurements asked for on it I can calculate your compression ratio and see what cc head you should be using based on the fuel you want to run..

[funkj]

Yea, just confirmed they do just a 4th gear also.His plan was to buy a spare cylinder/head and make the improvements and then change it over. Until he pulls the trigger im  just preparing. look

[sandblaster]

Cool... 

[1901306708]

1901306708

Re read your comment and see where you where going and the importance of port shape and efficacy regarding blowdown and duration not being the only important factor.

It does raise the question if a guy left the center valve at what point can you modify it and know where you have achieved the most efficient usefulness on both ends. Good old fashion R&D.lol

correct, i am saying in my findings, the shape of that top edge is more important than being able to adjust only half of the top edge. talking major surgery here so it may not be what you want.

i agree with the more clearance comment. they are too tight if you are going to be working it hard.

something to also consider is that cold crankcases make significantly more power. if your coolant is above 90F you're going to be down some. its probably worth looking at what you can do to address that. ducting, larger rad, increase coolant flow rate thru the motor etc

[funkj]

I think for now I'll make correction and keep the kips in tact and see where that lands us. If the kips allows a strong mid range that allows the driver to move in and through the pack /traffic over the Cr's, that's like gold.

Right now I'm waiting for the driver to make some decisions on how/when to approach this build. I'm excited to make this happen and see if there is any noticeable advantage to the Kx.


Of coarse, ifas a tuner if you find a advantage to put your driver in the front, you get to wear the Superman shirt.  

[funkj]

After a discussion with owner/driver, mutual friend/driver and a few others the discovery was 6000 rpm and under simply don't come into play after the start. They clutch/slip for a big hit of the start maintain 8600 rpm we with little rpm drop off the corners. Not one of them thought that the kips would play a factor.like anything else if not used doesn't make sense to maintain moving parts. in the end the owner wants the kips gone

That being said , here are a few questions.

1. It's a given with a raised cylinder exhaust and transfer port floorss will be well above piston at bdc. Not having the motor in front of me limits my fact finding mission.the obvious question is raising the exhaust floor and the transfer for duration.

2.with the kips removed, the resonance chamber will be open , it will have an effect on top end how much I have no clue. What's the best option if the chamber needs blocked?

Thanks guys..

[sandblaster]

If it were me I would do one of two things.
1. Lock the valves in the wide open position.
If you remove the valves you are leaving the resonators open and also creating turbulence.

2. If you want the most power, remove the the center flapper and replace it with a one piece machined part and reshape the exhaust port more like what you see in a CR500.
Use the drum valves and lock them wide open.

[1901306708]

its pretty easy to lock em open. just make a little gizmo that will hold the rod out all the way. then its temporary, you can lock it open and test, and put it back

mine is hooked up to a dyno now. one of the things on the list to test is locking the kips open vs having them operate.

not sure i would run it long at 8600. may work for awhile until it unravels. the stockers also dont make much power up that high.

[funkj]

not sure i would run it long at 8600. may work for awhile until it unravels. the stockers also dont make much power up that high.

Idk but George Becker of Becker motors and qrc karts literally invented outlaw karts in the 80's and been keeping them together at mid 8000 rpms for years. Zimmerman of Straight up performance is probably the most conservative builder in the business and I know for a fact he will tell you to gear for 8400-8600 with his pipe/ motor combo. Every builder out there advertising 90-100 hp on gas nobody going to convince me their doing them numbers at 6000-6800 or at conservative port timing. Kart motors period are high maintenance about 4 nights on a piston and six is pushing your luck. in my sprint shifter 80/125cc moto motors 3. Race days was tops on a piston.

Stockers area  out of power under 7000 and there also in the back of the pack with not a prayer of being competitive . I picked this guy out to help because I believe his driving ability/experience is the only reason he is mid pack in a stocker and the fact he isn't an overweight 40 yr old.

[funkj]

If it were me I would do one of two things.
1. Lock the valves in the wide open position.
If you remove the valves you are leaving the resonators open and also creating turbulence.

2. If you want the most power, remove the the center flapper and replace it with a one piece machined part and reshape the exhaust port more like what you see in a CR500.
Use the drum valves and lock them wide open.

That's pretty much where I was headed, seems like the most simple solution..

[sandblaster]

Option one works well and gives a lot of power,,
Option two gets freaky power 

[funkj]

More discussion..

Came across a  86 kx500 jug for sale.b. Looking at some of the data provided on the site, states that year is factory stock port timing at 192 /119 . Seems a little big on blow down and a little light on transfer duration to me.

[funkj]

Anybody know what the factory specs are.on the 86 head?

[sandblaster]

I don't have head specs for the older K5's but I can tell you that if a 86 top end is done correctly they can be a rocket..





https://youtu.be/5D6_9w3KlAI

7X KX500 Drag championship winner Jeff Grawbarger uses a 86 top end on this bike with a 89-04 bottom end.
Yes, I know the specs.
No, I can't tell you 

But I will tell you this... Less has been done to this then you might think..
And that bike is freaky fast...

[umberto]

I thought I read somewhere that the 89 and up bikes were detuned a bit from the earlier 86-88 bikes. Is that true?