KX Riders
Maintenance & Technical => KX500 Original => Topic started by: funkj on May 30, 2018, 12:28:51 PM
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first off; Great site, lots of really good solid info, hats off to those that provide it. Thanks so much. Thanks
I'm a long time kart racing dad, years of building and racing two strokes on the national level. mostly IME 100cc, KT-100 cc yamaha, Cr-125's and a host of 200cc Yamaha motors for fun.
Recently, I've been "volunteered" to help a struggling 500cc outlaw kart racer of a mutual good friend. I The only one in class running a bone stock kx-500 with a Sup pipe and a mid pack racer who I'm guessing is just outclassed by better prepped motors.
Un familiar with the kx-500 other than my week of lurking/reading self educating.ive never been a fan even in kartting for an all out top end motor and always been a fan of a motor with good mid range/ upper power. So saying that I think I have talked myself out of elimination of the power valve presently the stock motor has a good mid range/upper pipe by straight up performance.
My thoughts at this point right or wrong and certainly acceptable and open to to advice and critical opinion.
1. Raise cylinder to zero deck or deck to zero.
2. Like to shoot for 194 ex duration.
3. Clean widen transfers, possibly raise but like to keep a reasonable blow down number
4. remove exhaust sub port wall.( Not sure what to do with compression bump)
5. Clean / widen exhaust port.( Stay with 75% ish of bore possibly)
6. Open exhaust floor back up from raising cylinder.
7. Make modifications/clean power valves.
8. Raise booste port
9. Clean/port intake
10. Modify intake for v-force Reed cage.
11. port / clean transfer main/aux.
12. Cut head for :
A. 1.3 to 1.5 squish clearance.
B. 5 degree squish angle
C. 35cc chamber installed.
Note: I've heard of several national guys running kx500 with out power valves but I'm not wanting to put this guy in a balls out top end motor with a bunch of piston maintenance.id like to shoot for so.ething in the 8600 rpm power range.
Flame away guys..
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He should be beheaded for removing it from the bike!
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Oh boy, and I thought Ford blue loyalist were bad. :|
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I think your project sounds fun. I love it when people think outside the box with our favorite big two stroke. We have a few guys on the site that are very well versed in modifying the 500. Some of them don't get on very often, so it make take them a few days to comment. Be patient though; there is a lot of knowledge on this site.
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Umberto, thanks for the support.
Yea, this guy is in a field dominated by Honda CR-500's. Im not particulary brand loyal between Honda/Kaw but Ilike you I'm encouraged to help the guy outside the box. I'd like to see this guy in the front row, so I'm gonna give it my best, and a kinda of pay it forward effort to help out a racer.
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Oh man.... I've been wanting to do a KX500 Kart engine for some time....
Jason Tanner who does all my builds for me has been doing several CR500 Kart motors but it seems in that game KX500's are far and few between.
In fact, his build won the local championship last year.
https://www.youtube.com/watch?v=wEC_voeVpws (https://www.youtube.com/watch?v=wEC_voeVpws)
Can you make the KX500 competitive?
Oh yes you can.... :-D
Most of what you said you would like to do is ok.
But there is some easier ways to do it.
Don't raise the transfers or ports... Lift the entire cylinder using a spacer and two base gaskets.
A good number to shoot for on the port timing is 191.
191 give a good all around power range...
Don't get me wrong, 194 will work but it will start making the engine a bit peaky.
You can get really close to 191 by lifting the cylinder approx .080".
That means you would need a .060" aluminum spacers available from Cometic, one .020" standard base gasket, and one modified .020" base gasket also available from Cometic.
But before I go further, is the engine pulled apart?
If not, watch this vid and get the info asked for.
https://www.youtube.com/watch?v=eTjceU2M7kw&t=110s (https://www.youtube.com/watch?v=eTjceU2M7kw&t=110s)
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Sandblaster, thanks for the responce. After lurking for a week I was hoping you would would be one of those who offered advice. :wink:
Yes, I'm excited to do the project. Just watching him run mid pack with a bone stock kx5 eBay motor with who knows what kind of time on the motor against some well prepped pro build Cr's motors I hope is an indicator there is a ton of potential in a Kx5 equally prepped.
His present plan is to buy a used cylinder/head and make the proper modifications and continue to race his present motor and at some point change them over and have the same modifications for a spare cylinder/head. Maybe even change the second cylinder/head up a bit depending on the performance of the first.
He located a in-expensive 85 cylinder (non Pv) that needs plating but I really didn't feel as if I had enough info/knowledge to pull the trigger on that and suggested we stay with the same year cylinder for simplicity.
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What year engine is it?
What fuel do you plan to run?
What carb and intake is on it?
Does it still have all the gears in the trans or are you using only one gear? Usually 4th...
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1.Not sure what year, he hasn't identified it yett but he thought it was 88 or 89.
2. I think right now he runs 93 pump
3. Stock carb/intake/reeds and cage.
4. No gear delete , yet.
5. I thought he ran a Sup pipe , but my buddy says he run's a stock pipe.
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Ok, well... there is plenty of room for improvement :lol:
One thing to remember.. When you have the cylinder plated, be sure to add .001 inch of extra clearance.
Kart engines get ran on the cold side and I have seen a number of them cold seize.
There are some key differences in the cylinders by year,
Post a pic of the left side of the cylinder...
You don't want the 85 cylinder.
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My couple ideas. Take em or leave em.
Blowdown is way more important than transfer duration.
That center powervalve is a joke. You want a nice clean (as flat as you can get without catching a ring or piston) exhaust port edge to send a good pulse into the exhaust. That's the most important thing of the entire cylinder layout in my opinion.
Going to a bored kehin at 41 added a couple thru the powerband on a stockish engine. If you get a motor that flows, a 44 will add 3-4 on top of that.
The kx is not set up for making power. Need help to make it flow. Gotta do it all to get big gains, otherwise your just talking 1-2-3 hp here and there. Cylinder work, pipe, carb, compression, timing all need major help in my findings on the dyno.
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My couple ideas. Take em or leave em.
Blowdown is way more important than transfer duration.
That center powervalve is a joke. You want a nice clean (as flat as you can get without catching a ring or piston) exhaust port edge to send a good pulse into the exhaust. That's the most important thing of the entire cylinder layout in my opinion.
Going to a bored kehin at 41 added a couple thru the powerband on a stockish engine. If you get a motor that flows, a 44 will add 3-4 on top of that.
The kx is not set up for making power. Need help to make it flow. Gotta do it all to get big gains, otherwise your just talking 1-2-3 hp here and there. Cylinder work, pipe, carb, compression, timing all need major help in my findings on the dyno.
I'm definitely open to suggestions..
1. I'm unclear on you center Pv comment if your suggesting it's removal I'm not sold completely on keeping it. However I'm apprehensive on its removal due to my inexperience. I don't want this a top end peaky narrow band build with a bunch of piston maintenance.keeping in check he has a mid/upper pipe designed around a 8600 rpm and a track that doesn't have to have a top end 200 hp alky motor to win.
2. Also unclear of the blow down comment, maybe eluding to cut the ex-port to desired duration rather than lifting the cylinder and keeping stock blowdpwn transfer numbers.
I appreciate the comments.
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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
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Here is food for thought...
You are driving very small diameter tires.
Yes, they are wide but you can only apply so much power to the dirt and drive forward and not spin the tires.
From what we learned on the championship kart is that smooth usable power is where it's at.
It's a learning curve based on your track size and conditions.
Sometimes you have to go slower to go faster.
That is why you can go to 10 different tracks with the same set up and some you will do good, others you will get destroyed.
Kart set up and engine tuning will play a huge part in winning and loosing.
Don't over build is my suggestion... it's tempting to do but will hurt you far more then help you.
On your Kart are you using fourth only or are you shifting?
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Here is food for thought...
You are driving very small diameter tires.
Yes, they are wide but you can only apply so much power to the dirt and drive forward and not spin the tires.
From what we learned on the championship kart is that smooth usable power is where it's at.
It's a learning curve based on your track size and conditions.
Sometimes you have to go slower to go faster.
That is why you can go to 10 different tracks with the same set up and some you will do good, others you will get destroyed.
Kart set up and engine tuning will play a huge part in winning and loosing.
Don't over build is my suggestion... it's tempting to do but will hurt you far more then help you.
On your Kart are you using fourth only or are you shifting?
I think that track the locals use 3rd/4th.
It's a hard lessons but the simple fact is you can't win with a great motor, poor driving and poor chassis, nor can you win with a great chassis, poor motor and driver or a great driver and poor motor and chassis. But you can win consistently with a good driver, good motor and good chassis.
As far as smooth on dirt in outlaw class it just isn't as critical as other classes and other kart venues that don't have the power to re-cover. I've seen both in outlaw the smooth driver who drives radial preserving corner speed to the guy who pitches his kart and clutches for a big hit off every corner.
I prefer not to put the driver in a motor that he can't carry corner speed without clutching and upsetting /unloading the kart to keep a usable power band or adding teeth and gearing himself out..it's a balance act.
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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 :-D ) .
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 :lol:
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..
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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
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Cool... 8-)
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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
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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. :lol: :lol:
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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..
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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.
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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.
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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.
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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..
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Option one works well and gives a lot of power,,
Option two gets freaky power :-D
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More discussion.. :lol: :lol:
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.
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Anybody know what the factory specs are.on the 86 head?
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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..
(http://www.oem-cycle.com/forum/download/file.php?id=4359)
(http://www.oem-cycle.com/forum/download/file.php?id=4357)
https://youtu.be/5D6_9w3KlAI (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 :lol:
But I will tell you this... Less has been done to this then you might think..
And that bike is freaky fast...
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I thought I read somewhere that the 89 and up bikes were detuned a bit from the earlier 86-88 bikes. Is that true?
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Port timing
(http://www.oem-cycle.com/forum/download/file.php?id=6830)
Compression
(http://www.oem-cycle.com/forum/download/file.php?id=6831)
Skipping 85---
86 had the highest port timing and compression.
89-04 was next best
87 was next best
89-04 was next best
88 was the worst
86-88 are the easiest to port and can all be made to scream.
89-04 can also be made to scream but it takes a bit more effort.
With my new valve design I'm hoping to make some significant improvements on the 89-04 but time and dyno testing will need to be done.
Mechanically I have it operational... Took me three attempts (welding and hand machining) to get what I wanted.
I'm sending my cylinder away next week to get it bored and machined..
I'm also sending in my crank to get it rebuilt.
So I should have something to test in about a month or so...
I hate sending my cylinder off to the competition because they will see what I am doing :-(
But they will only get half the story without the valves :-D
I won't say who it is going to either cause I really like the guy but we don't share everything :evil:
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86/ 88 had all almost similiar port timing {120/180duration}
only real differance was main exhaust port on 86 is far smaller
Dont know where clmer got those specs
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Hmmm... I did not know that.
I'll have to pull the 88 cylinder off the wall and do some measurements...
Do you have the exhaust port height and width for the 86?
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I'll have to pull the 88 cylinder off the wall and do some measurements...
Sorry to hijack a thread, but did you ever get an 88 cylinder head in? I'm still looking for one...
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Am I safe to assume the 86 cylinder is a 3 port exhaust with 2 drum valves and no main port flipper?
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Hmmm... I did not know that.
I'll have to pull the 88 cylinder off the wall and do some measurements...
Do you have the exhaust port height and width for the 86?
yeah i post a pic if in can find it
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86/ 88 had all almost similiar port timing {120/180duration}
only real differance was main exhaust port on 86 is far smaller
Dont know where clmer got those specs
That makes better sense to me.
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Am I safe to assume the 86 cylinder is a 3 port exhaust with 2 drum valves and no main port flipper?
Yes, that is correct.
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Here is a pic of the 86 cyl.
Note: no decomp scallops and a smaller exhaust port then the 87-88
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Here is a 1988 Cylinder..
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Great info... :-o :-o
Looks like for me the 86 cylinder would be the best for and application where your wanting to eliminate the power valve. You have the option of lifting the cylinder or raising/the exhaust or a combination of both and leaves some options for transfers.
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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..
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 :lol:
But I will tell you this... Less has been done to this then you might think..
And that bike is freaky fast...
don't under estimate what all has been done here lol.
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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..
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 :lol:
But I will tell you this... Less has been done to this then you might think..
And that bike is freaky fast...
don't under estimate what all has been done here lol.
I would never.... :lol: