: CR 500 engine mods.I need a good site



arcrz
12-17-2003, 08:55 PM
Anybody know a good site that has some performance tips on the CR500? I`m gonna be building a 500 motor for a guy and would like to do a little research on it.

Thanks

Jumby
12-17-2003, 10:57 PM
What do you want to use the motor for? I have built quite a few of them for racing

R6 Jono
12-17-2003, 11:17 PM
he wants to put it in his RZ.. use the cb motor for the front wheel.. so he's gonna have a 1L :)

arcrz
12-18-2003, 08:33 AM
Originally posted by R6 Jono
he wants to put it in his RZ.. use the cb motor for the front wheel.. so he's gonna have a 1L :)

:laughing :laughing I gotta keep up with that ZX-10 somehow.

Jumby: He just put a 500 motor into a 2001 CR250 Aluminum frame and now he wants to freshen up the 500 motor and do a bit of hot rodding on it as well.He mainly uses the bike for riding with his buddies but wants to do a bit of motard racing next summer.The bike has a lot of pretty nice stuff done to it besides the A.F.More than anything he just wants to have a bad ass motor to suit the rest of the bike.

:laughing :laughing I`m still laughing Jon.That was a good one :thumbup

R6 Jono
12-18-2003, 10:32 AM
haha, now why worry about keeping up with the zx 10..

you have to pass me first :p

:laughing :laughing

arcrz
12-18-2003, 11:06 AM
:lolup He`s funny.......funny like an itchy nut.

Jumby
12-18-2003, 03:38 PM
I can give him all the specs needed to do the motor, I suspect he will still want it to be ridable in the trails. If you have ever been out to Mission and watched the racing, the #69 CR500 of Paul Ludwigs is my old bike, and I did all the work on that motor. I all so used to practice at the Tsawassen MX track with the very same bike, and I used it for trail ridding. It was an allround good motor, but you really had to be carefull with throttle control, one wrong move and it would spit you out real fast.

The work is real simple, raise the exhaust port 4mm, and the boost port 1mm, take the squish band down to .9mm CC the head to 73, and thats about it. I would run a ProCircuit pipe and silencer, you can allso run an FMF fatty pipe, those pipes will give you better usable power when doing MX or trail riding, and are good enough to race motard with.

I will warn you though, those specs will give you so much power that it will be difficult to race Motard on the small tracks, I know the beast is a handfull on tight tracks. You should get an easy 65+HP at the rear wheel with those specs, and you will have to run a mix of 50%VP C14 and 50% 94pump fuel. You can get much more power out of the motor with a topend pipe but you will have trouble finding one, there is 2 made in the UK, DEP and another I can't remember the name. I would only do the mods I gave you, cause the motor is so reliablethat way, i put over 100 hard hours on it with out a problem. If you need any more info let me know.

arcrz
12-18-2003, 08:03 PM
Thanks Jumby.That sounds like the type of motor I want to build.I dont know how he`ll feel about the C14 mix though.How will this build run on straight 94 Octane.I may have to tone it down a bit.

Right now the motor is stock except for an FMF pipe and a Rad Valve.So far my plan is to port match everything,give all the transfer ports and intake a good 120 grit cleanup without altering any heights, then give the exhaust port a good mirror finish polish.What do you think about the old trick of adding an extra base gasket.Its a pretty popular mod a lot of Europeans do with the RZ500.Any input is very welcome.

Jumby
12-19-2003, 12:25 AM
Well here's the thing about the CR500 motor, stock it makes most of it's power in 2000rpm, and this makes the bike somewhat difficult to ride on Supermotard tracks and on hard packed MX tracks. So what you want to do is make the motor rev out more, and to do this you raise the exaust port. Doing this gives the motor more topend (it reves out more) and spreads out the power delivery, which make the bike easyer to ride (wider power pand). You can use a few base gaskets to do this but you end up rasing all of the transfer ports and the boost ports the same amount, it's not what you really want. It is real easy to raise the ports with a file, thats how I do it, the barrel is so large on the 500 you won't have any problems getting in there. DON'T use a dremel tool unless your real good with it, it doesn't take much to fuck up a barrel with one of those. What you have to remember is by raising the exhaust port you have just lowered the compression, so now you put your attention on the head.

The head is where you will get all of your torque, and make our motor run nice at 8800rpm, (stock is 6400rpm). The CR500 has a huge combustion chamber, allmost 2mm this is insane. I have the head milled to .9mm of squish and then I have it CCed, to 72 or 73cc. You may have to have someone check this for you, unless you have the proper tool to check it, but make sure it correct, if not you will blow up the motor in a bout 10 minutes. The head work is the most important part of the mods, with out doing it you will lose power and eventually fuck your motor. The heads are cheap, I think there around $140. You were asking about fuel, you will have to run a high octane fuel, there is no way around it, if not the motor will detinate and burn a hole in the piston in a few minutes. You can run 50% C14 or any other 104+ octane fuel and 50% 94octane pump. High octane fuel will all ways be needed when you get in to mods on 2strokes, there is no way around it, unless you want very small performance changes. There is so much more I could tell about getting more power out of that motor but I hate typing, if you would like to call me, Pm me and I will give you my phone #

arcrz
01-02-2004, 07:45 PM
Thanks for all the info Jumby.I appreciate it.
After talking with the guy about what he really wanted and what the bike would be like if modded to what you suggested or something similar,he decided to keep it pretty much stock.

I`m just about finished the build.I decided to blueprint it then clean up all the ports & intake,match the case to the jug and then match & polish the exhaust port.That mixed with the FMF and a Rad Valve should give him a pretty decent motor.

If it were mine I woulda done the build the way you described with a DEP pipe and went and scared the hell outta myself.
I think I may try to find a 500 for myself by this summer :evilgrin.

:rider