All about reed spacers -

[fullbore55]

I installed the torque spacer and the boyesen pro reeds today.   I definetly think that for well under $100 for both items, this is the best mod for the kx500!   I think this site is awesome and I wish it was available 25+ years ago when I was just getting into the sport.  Thanks to everyone!

[stock500]

I don't want to have to mess with the jetting or anything.  My bike is 100% stock, and I like it.  If I get a reed spacer will it affect my jetting?  I thought about adding a little weight to the fly wheel to smooth it out even more, but if I can get some results with a spacer, maybe the fly wheel weight is not needed.  Any information would be Great.

[alan]

I put on a reed spacer and a FMF Gnarly pipe and never changed the jetting at 4000 Ft. No problem! I just was easer to start, stopped fowling plugs and could run 1 gear taller in the boondocks without bogging down.
I really don't think jetting is a major issue, just watch the color of the plug and don't let it go to light brown.

Alan

[Dutch-K5 Fan]

Why Reed Spacers?

Basically, reed spacers allow you to move your power band around depending on placement.

The most common installation for street use is to mount them between the reed block cage and the engine. This will effectively move your power band to a lower rev range and allow you to make better use of the power available for street riding.

The second type of installation is to mount them between the manifold and the reed block cage. This will move the manifold back further and raise the power band for better midrange and top end.

And what if you do both options???
A 1/4" between the reed block cage and the engine, and a 1/4" between the manifold and the reed block cage???
MORE power from bottom to top

[Danger4u2]

When you add 1 reed spacer it moves the carb back against the frame.  No room for 2 spacers unless you change how the carb mounts.

[stroke.n.smoke]

I bought a spacer kit, came with two different thickness spacers, I wanted to use the thicker one, which was about 1/2 to 3/8 inch thick.  I ended up using the thinner pacer, which was around 1/4 inch thick because the airbox/carb was hitting the shock...  You can't get away with using a very thick spacer becasue of that problem...

I never really noticed a difference anyway.

[BDI]

After about 80 hours of dyno testing I found that a six and a half inch spacer was good for a 25 horse gain.

[3Razors]

Did anyone notice a loss of top-end power when doing this mod on the KX500?  I am contemplating doing this but I'm steered away at times knowing that this mod (usually) takes away top-end power.

[don46]

While I think the spacer mellows the bottom, I personally don't see the deal, I know most swear by them. In my case I use the 250 carb bored to 40mm, the idea being that the slide is moved closer to the piston, the shorter distance helps improve throttle response, this has been a tuner trick for a long time. the 250 carb is much shorter than the 500 carb, so then you add a spacer and it would seem that it would take away response and maybe thats why people like them, they smooth out the "hit". For my money I want instant response.

[don46]

After about 80 hours of dyno testing I found that a six and a half inch spacer was good for a 25 horse gain.

If I use a 13 inch spacer can I get 50 hp or a 191/2" and get 75, there you go I wouldn't even need a motor just a spacer and I'd have apretty hot bike.

[Hillclimb#42]

so then you add a spacer and it would seem that it would take away response and maybe thats why people like them, they smooth out the "hit". For my money I want instant response.

I agree with you guys 100%. They mellow it out and that is perfect for most people. Its when you want to start shaving tenths or even hundreths or add another 200 rpm's to you rev that real power is gained. The adverse side of that is that alot of people would consider it too hard to ride. When people say its like riding a bright green rocket with no brakes, it doesn't paint a mental image of alot of controlable riding. The key might actually be to start with a flywheel weight and a spacer and then progress to the after market pipe, lose the weight and spacer. The trick is to tweak the way you intend and to set it up so you can rip as fast and with as much control allowed by that bad a** bike that you have there.

[don46]

At this point in my life (50) I enjoy riding the 250f, I don't get into much trouble, well at least to much. My son competes on a professional level in hillclimbs, I build bikes for him, and I want the most competitive that I can come up with. Like BDI and Stewart I have piles of parts that didn't prove out like I'd hoped, you keep plugging away and hope you hit on something. Like I've said I use the 250 carb on the nitrous bike and the Lectron on the gasser. Personally, for the riding we do, Reed spacers are not in the cards, WE want quick HP and all through the power band. I think spacers are great for trail riders, but wouldn't think they would be good for duners or anybody looking for all out HP. By the way we did use spacers on some of our 125's to pick up a bit of bottom end torque. At the end of the day, I think it depend s on the power curve your looking for, and as an individual you need to tailor it to your needs.

[3Razors]

I ride wide open dunes and drags where top-end is really important.  I didnt want to run this spacer if it took anything off the top.  I had heard a rumor that the stock KX500 cage sticks too far in and pulling it out a little made more power everywhere, again just a rumor but I wanted to see if anyone on here can verify this.  Also which reed assembly gives more top-end power v-force or rad valve?

[kaw rider]

stock cage= spacer
v-2,3 no spacer

[BDI]

If a guy really wanted to make his kx500 have more power on the bottom and be more like a tractor and did not care about sacrificing a little top end what I would do is weld in the bottom corners of the main exhaust port and make it smaller and then bore and  replate the cylinder. Take the main exhaust port from being a big square and make it more like a upside down triangle. If you did this you would turn the bike into a billy goat for sure. It would have low end like a harley.