1991 Kdx 200 and Ken O’Connor racing

[JZ05220r]

So I’m getting ready to drop my 91 Kdx engine off to Ken O’Connor racing to be gone through. I am having trouble deciding if I should keep it a stock build or not. I really don’t want to create a headache by going all out. Anyone got any input? Are these e model bikes still plenty strong enough stock with a full fmf? Thank you

[SS109]

You don't have to get crazy to get really great performance from a KDX. Make sure it's in great mechanical condition and dialing in jetting is a huge step. Then, adding regular bolt ons will add even more. The only non-bolt on thing I would have done is to get the squish on the head corrected. It adds power everywhere and helps make jetting easier.

I've done about every mod that can be done short of porting and I'm very happy with the power my bike has. I'm running Boyeson RAD valve, FMF desert pipe with Turbine core silencer, RB carb and head mod, air box lid removed, and my own custom CDI ignition. The only other thing I did was to gasket match the crankcase to the cylinder and removed some minor casting flashing on the cylinder intake and exhaust being very careful not to change any of the ports to the cylinder at all. Notice that every mod other than the head squish mod gasket matching/flash removal is a straight bolt on. You can check out my vids to see and hear how my bike runs and sounds while riding with way more modern, and hugely more powerful, bikes.

[JZ05220r]

You don't have to get crazy to get really great performance from a KDX. Make sure it's in great mechanical condition and dialing in jetting is a huge step. Then, adding regular bolt ons will add even more. The only non-bolt on thing I would have done is to get the squish on the head corrected. It adds power everywhere and helps make jetting easier.

I've done about every mod that can be done short of porting and I'm very happy with the power my bike has. I'm running Boyeson RAD valve, FMF desert pipe with Turbine core silencer, RB carb and head mod, air box lid removed, and my own custom CDI ignition. The only other thing I did was to gasket match the crankcase to the cylinder and removed some minor casting flashing on the cylinder intake and exhaust being very careful not to change any of the ports to the cylinder at all. Notice that every mod other than the head squish mod gasket matching/flash removal is a straight bolt on. You can check out my vids to see and hear how my bike runs and sounds while riding with way more modern, and hugely more powerful, bikes.

Thanks for your response I didn’t realize RB did the head mod for the e series. I didn’t like the rad valve very much on My 220 but I’ll give it a go on the 200. It’s looks like RB only offer their head mod for the 220 now. I think I’ll have KOR “set the squish to run safely on 93”... does that sound like an ok way to word it? Thanks again.

[SS109]

RB still does the head as far as I know. However, he is semi-retired so he doesn't do as much as he used to. I would contact him if you want him to do it but Ken O'connor should be able to do the same service and is probably the better way to go since your engine is already going to be there. Yes, your wording explains exactly what you want done.

[KDXGarage]

Look into an R1173N needle instead of the stock thickness. I can't remember the Keihin translated letters, but it is the next step thicker. (same length, same taper, just thicker for leaner at 1/8 - 1/4 throttle). My 1994 imroved after that suggestion from Fredette.

[JZ05220r]

Look into an R1173N needle instead of the stock thickness. I can't remember the Keihin translated letters, but it is the next step thicker. (same length, same taper, just thicker for leaner at 1/8 - 1/4 throttle). My 1994 imroved after that suggestion from Fredette.

That’s exactly then needle I plan to run. That’s what fmf recommends as well.

[JZ05220r]

Thank you SS109 and KDXGARAGE for all the help with all of my questions and concerns. Their are others on here as well like John S for example. You guys are always coming through when I have questions and it is definitely appreciated.

[KDXGarage]

All the people on here pitching in is really quite amazing.

Thanks to all of you!

[JZ05220r]

You don't have to get crazy to get really great performance from a KDX. Make sure it's in great mechanical condition and dialing in jetting is a huge step. Then, adding regular bolt ons will add even more. The only non-bolt on thing I would have done is to get the squish on the head corrected. It adds power everywhere and helps make jetting easier.

I've done about every mod that can be done short of porting and I'm very happy with the power my bike has. I'm running Boyeson RAD valve, FMF desert pipe with Turbine core silencer, RB carb and head mod, air box lid removed, and my own custom CDI ignition. The only other thing I did was to gasket match the crankcase to the cylinder and removed some minor casting flashing on the cylinder intake and exhaust being very careful not to change any of the ports to the cylinder at all. Notice that every mod other than the head squish mod gasket matching/flash removal is a straight bolt on. You can check out my vids to see and hear how my bike runs and sounds while riding with way more modern, and hugely more powerful, bikes.

I’m going a very similar route as you in terms of engine mods but I’ll be using a 36mm carb. Although I know it’s personal preference did you stick with 32:1 on your mix ratio? I know frp recommends 50:1 for the e series.

[SS109]

I’m going a very similar route as you in terms of engine mods but I’ll be using a 36mm carb. Although I know it’s personal preference did you stick with 32:1 on your mix ratio? I know frp recommends 50:1 for the e series.

I run 40:1 in all my 2T bikes including my old E-series KDX I had. I run my bikes pretty hard for an old slow guy. A little extra oil doesn't hurt anything as long as you're jetted properly and can help ring, piston, and bearing life.