Messages

1

General Two Stroke Talk / KX500 engine rebuild

« on: January 13, 2013, 11:07:25 PM »

porting, 250 ignition, 41mm pwk (pump gas), and what ever else i can think of

I recently built a CR500 engine specifically for MX so our two goals are miles apart, but some
of the mods I made would be beneficial for a dune bike.  For the top end, I had Eric Gorr do the
port and head work.  He recommended a Wiseco piston because it is more durable than the
cast OE.  I sent that piston and crank assembly to Crank Works for balancing at 6-8000 rpm
which is the meat of the powerband for a 500.  I also had all of the rotational internals REMed.
This process greatly reduces friction and heat and improves clutch action and shifting.  I also
installed a VForce 3 reed and a 2000 CR250 ignition with a Vortex IC.  IMO, all of these changes
would also be beneficial to a big power, top end engine. 

Here's a couple of pictures of my engine.  I look forward to following your build and to see what
you ultimately come up with.

With the lighter weight that monster is going to hit like a beast

Actually, the bulk of the weight (crankshaft), is still there.  The smaller rotor helps with the gyro
effect and makes the bike feel lighter and more manageable in the air and in corners.  The biggest
gain is going from an analog to a digital ignition and the ability to program the mapping.  You can
really increase the hit (if you're a sadist), or virtually eliminate it.

dogger

I see you have the Delta 3 reed valve system. Did that come with a boot that goes to your carb or do you have to use the stock boot?

2

Technical / 91'''''''''''''''' Kx500 trouble running. HELP!

« on: January 13, 2013, 10:50:49 PM »

Coil testing is done over the resistance and even with a good looking spark the coil could be on its way out. They have 2 circuits both have to work. Ohm values should be in the manual.

If you have another coil at hand just connect it and try to start the bike.

I have a few gaskets and other parts on order that I think I'm going to try first. They needed to be replaced anyway.

I'll get a multimeter and test the coil pack. Let me ask you this. What is the coil doing for my bike and why would it make the bike start and cut off. Still trying to learn all the parts for my bike. I don't have a spare one but if all else fails I can order a new one.

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Technical / Delta 3 Reed Valve system...?

« on: January 13, 2013, 01:48:27 AM »

Looks like it has a boost bottle nipple on it

I think that is a general picture, not the exact one for my bike. What would a "boost nipple" be doing on a Kx500 intake?

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Technical / Delta 3 Reed Valve system...?

« on: January 13, 2013, 01:24:45 AM »

This is the link and P/N if it helps.

http://www.partzilla.com/parts/detail/aftermarket/XP-4578956.html

5

Technical / Delta 3 Reed Valve system...?

« on: January 13, 2013, 01:22:17 AM »

I'm replacing the carb boot on my 91' Kx500 and I haven' t touched the reed valves yet. I ordered the boot only but it doesn't ship until the 15 Jan. I still have time to change my order so here's my question. I'm looking at the Delta 3 Reed Valve System by Moto Tassinari. Does anyone know if this comes with the reed valves as well as the boot in one assembly? If I go ahead with this upgrade do I need to screw around with my jets and needle? Any takes on this manufacturer? Good or bad reviews?

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Technical / 91'''' Kx500 trouble running. HELP!

« on: January 13, 2013, 01:12:22 AM »

Everyone here has great ideas and is full of info. I really appreciate the help and all the knowledge people are sharing. I hope everyone is learning as much from this as I am. If anyone rides in VA or is close to it lets get some riding in once I get this beast running. I have no doubt you guys will help me fix the bike. I'm going to take pictures monday when I go into my shop and show you what I'm working with.

7

Technical / 91'' Kx500 trouble running. HELP!

« on: January 13, 2013, 01:10:11 AM »

How about the coil? Did you test it? Coils  can get back give you some problems which seems to get jetting.

Should I have to even test the coil? I'm getting a steady spark. And when you say test the coil do you mean a voltage test or an ohms check? Give me a little walk through on what you mean so I can see if that has anything to do with it.

8

Technical / Keihin PWK carb Kx500 Jetting

« on: January 12, 2013, 07:11:34 PM »

Where do you live (humid/dry) and what elevation are you at? Stock bike or mods?

I live in Virginia, we see a lot of 100% type days here. I'm directly at sea level. Stock bike... for now.

9

Technical / Keihin PWK carb Kx500 Jetting

« on: January 11, 2013, 06:27:33 PM »

I'm going to re-jet my carb here as soon as I get some good advice. Let me know what you guys know about this, I'm new to the whole jetting thing.

main jet - no number on it which is really weird to me. ive ran it before but i would like to know what size it is. im ordering a new one but not sure what size i should get. what size main jet should i run - 162, 165, 168, 170, 172, 188?

pilot jet - clean as a whistle. didnt look at the number on that but I'm thinking of re-jetting anyway. any suggestions on the size for when i do look, 55, 58, 60, 62, or 65?

What two jets would work good together or does it matter? I dont want to for example put a 55 pilot and a 188 main jet and bog it out or starve the engine. What am I getting into here?

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Technical / 91'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Kx500 trouble running. HELP!

« on: January 11, 2013, 02:41:03 AM »

To check if the float height is set correctly, you will probably need a manual, or find one online. Once you get the proper float height, adjust accordingly by setting the small metal tab to the correct hang height for the floats.

PS. I think it's an air leak. Does it idle, or rev really high when you first start it up for the 15 seconds it runs?

I set the float height so that it shuts fuel flow off when the float is level with the part where the bowl and the carb meet up. Should I go lower on the tab so the fuel cuts off at a higher fuel level? Once it starts up it will set at a higher type idol. I peg the throttle out and it barely goes what a normal 1/8 throttle would be.

11

Technical / 91'''''''''''''''''''''''''''''''' Kx500 trouble running. HELP!

« on: January 11, 2013, 02:37:00 AM »

Piston in backwards?
Carb passages blocked?

Didn't know you could put a piston in backwards...
Carb was completely dissasembled and cleaned 3 times. Found some junk but it's clean as a whistle now. Needle is set to the third rink. Carb is a 39mm Kehinin. Not sure what the main jet size is, no marking on it but I've been running it for years before this rebuild. Same with the pilot jet.

12

Technical / 91'''''''''''''''' Kx500 trouble running. HELP!

« on: January 11, 2013, 02:33:36 AM »

Almost sounds like you've got a big air leak some where. Did the piston grenade?

Used piston and top end but plenty of compression.

13

Technical / 91' Kx500 trouble running. HELP!

« on: January 11, 2013, 12:26:30 AM »

I have a 1991 Kx500 which hasn't ran in about 3 years due to a blown piston and me being away in the military. I'm rebuilding it and getting it in running shape now.

I got a new top end and piston along with all new gaskets for top and bottom end. Long story short it's rebuilt and mounted on the bike. I've done 3 top end rebuilds so I'm not new to this but I'm stumped on this problem: The bike will not start without having 1/4-1/2 throttle open. When the bike finally turns over and starts I have no throttle control and it will only run for about 5-15 seconds and then sputters out. I know the problem can be one of three things; spark, air, or fuel.

1. Spark - There is spark but I'm not sure what my best gap setup should be, any suggestions?

2. Air - I'm not sure what would keep it running and I've messed with the pilot air screw anywhere from 1-5 turns out in 1/2 turn increments with no luck. I ordered a new intake boot because of dry rotting (possible leak) and new reed valves because I can't tell if they're bad. Not too sure how to tell if they're still good. Would the reed valves or boot cause this problem? Both parts on order.

3. Fuel - Petcock knob is broken but fuel still flows. On order. How do I tell if my float is shutting off fuel flow too early? Could this be my problem?

Please name everything you can think of so I can order parts or continue my troubleshooting.