Author Topic: KX250 Woods Conversion (Read 11472 times)

Dan_AKAL · « **on:** August 12, 2004, 09:49:21 PM »

I've got this 99 250 and I'm just gonna turn it into a woods bike this winter. There is a method to my madness here. I'm trying to get cross country racing started up here in the frozen tundra and plan on putting together a hare scramble next year. I bought this 250 from one of the guys who races MX and I am using it as a bench mark for the rest of the racers. Anyone here will recognize this bike from the MX track and when I am finished they will know what they need to do to get their bikes off road worthy. Anyway I have a few questions maybe you guys can help me with since this is my first Kawi. My previous experience is Yamaha and KTM.

I've read all of the stuff a KaToMer's web site. Thanks! This has been a big help. Now things like hand guards, skid plates, rotor protectors, radiator guards, and tuning the suspension are must haves. I'll put on an 11 oz. fly wheel weight and then see what I need to do with gearing. I already have Procircuit pipe, triple clamp, and shock linkage. The bike runs good but it is definately an MX bike. The throttle is more like an on/off switch than a throttle.

Here are some specific questions.

Anything I need to do to the Power Valve? At present it hits hard and a little early for my liking. However, I'll need to make more of a determination on this after I get the FWW.

How about reeds? Should I look here for different ones? I mean other than making certain they are functionally sound.

Someone please tell me about a torque spacer. I have no first hand experience with these. Only read about them. Besides going between the reed cage and the engine what do they really do?

Any comments on this would be greatly appreciated.

Dan

Rick · « **Reply #1 on:** August 13, 2004, 08:13:59 AM »

Dan,

The hard hit on power delivery is probably a manefestation of the pipe more than anything. Most motocrossers use a pipe that does not work as well for off road, so first thing to do is find out what pipe you have.

Next, you need to make sure your power vavle is working properly, so pop that cylinder off and clean the power valve. This may be your only problem.

To continue, DO NOT add a flywheet weight to a 250, as I don't think you will like the result. The reason it works for some (old guys, right Paul) on a 500 is because the 500 has the power to run the weight. While I do run one on my son's KX125 in some situations, it is meant for to solve the complete lack of bottom end on a 125 for deep sand corners, a problem that is not present on a 250.

Run a NGK BR8EVX plug in the 250. More expensive, but you will not be disappointed.

You don't need a reed spacer on a 250, so save the money.

In a nut shell, the 1999 KX250 works well without spending a lot of money. Focus on suspension, getting the power valve cleaned up, running the right pipe, and installing a stabalizer and you will be happy as a clam. (hand guards, skid plate, etc. are a given)

Good Luck

Rick

mikesmith · « **Reply #2 on:** August 13, 2004, 08:38:33 AM »

Good points,but with the pipe you can run a longer silencer (you need a spark arrester any way),the longer the silencer will soften the hit some.Id give yourself some time on the bike after you try Ricks tips and you will probally grow to like it.My 500 is ridden in everything (including very tight single track) and I only canged gearing,pipe,v-fource, power-now and I love it to have a "hit".

Dan_AKAL · « **Reply #3 on:** August 14, 2004, 12:34:43 AM »

Thanks for the info. There isn't much wrong with my bike as it is. However, getting it somewhat tamer would help. I could race it like it is but it is pretty snappy.

My bike currently has a Pro Circuit pipe and silencer. From my best determination it is a Works pipe and I'm not too sure about the silencer other than it is difinately a PC. I thought about a FMF Gnarly pipe as I think the PC Works is more of a MX pipe. However, I don't know that there would be that much difference. Seems as though PC has a lot of experience with Kawi's so I think that I would rather stay with PC but other than the Works pipe there doesn't seem to be a lot of options for my bike.

Rick you are the first person I have heard say not to add a FWW on my KX250 for the woods. Sure seems like it would stablize things some. Speaking of stabilizers you mentioned installing one on my bike. I am assuming that you mean a steering dampener.

I'll do a top end this winter so that will encompass the power valve. It probably is dirty.

Although I may not add a reed spacer just what does this thing do? I have heard them called torque spacers. Not really sure that I understand what would be gained by lengthening the intake on the downstream side of the reeds.

Thanks Again

Dan

mikesmith · « **Reply #4 on:** August 15, 2004, 08:20:24 AM »

Well as far as the reed spacer you already said what it does, increase the intake area for more crankcase volume resulting in a better charge.I think pulling the tips of the reeds back helps flow somewhat,there $27.00 or you could make one.I have only run a fly wheel weight on my wifes 85,not sure Im putting one on my 250.But unlike the 500 you have options on differnt weights for the 250,Id try like an 8oz,if you dont like it sell it.As far as the pipe Id run it,I think its a good pipe for most any type of rideing.And a Scotts stabilizer is on my 250 wish list!You know what works for one guy may not work for another, so get ideas from other riders,but go with what works for YOU!

Dan_AKAL · « **Reply #5 on:** August 17, 2004, 01:35:46 AM »

Mike,

I think I can understand how moving the reeds back can help with flow. By getting them further away from the engine there is less of an arc for the air to make as it enters the crank case. I know they are pointed down at an angle but I still can understand how it would improve the direction of air flow as well as allow the reeds to work a little easier. All of this adding up to less work the engine does to get the air in.

Most folks it seems are pretty happy with Scotts steering dampeners. I looked at the WER but I think that I like the Scotts better.

The pipe I'll run for the time being. Maybe after it gets bashed up some I might think of a Gnarly. However, will probably make a call to PC to see what might be available for my bike.

Thanks Again,

Dan

KaTooMer · « **Reply #6 on:** August 17, 2004, 06:05:04 AM »

Dan - just a few thoughts after spending the last year (most of it, anyway) in the woods on my '03 KX250. Many of the aftermarket mods available for MX bikes seem to be designed to make them work better on the track. I've not tried any Pro Circuit exhaust products, but my impression is that they attempt to improve what most MX'ers claim is a comparatively weaker top end than the other MX bikes out there. For a woods guy like me, I don't need any more top end on my KX. To smooth out the power, I'd look closer at FMF products, particularly the Gnarly pipe since it's designed for woods use. The Turbine Core or "Q" silencers will probably also help smooth things out. I just picked up a used "Q" on eBay...haven't put it on yet but judging by the size of that thing, it just HAS to tame the hit.

I haven't tried out any aftermarket reeds/blocks, again because my impression is that they add power where I don't need it. As for flywheel weight, I'm a believer. I rode it one time without any weight and that was it. You do give up some of the snappy throttle response with more weight on the flywheel, but in the woods I haven't missed it.

One thing I've been liking recently is the Braking over-sized front rotor. It was another eBay purchase...pretty amazing how much stopping power it gives (and the front brake was good to begin with).

mikesmith · « **Reply #7 on:** August 17, 2004, 06:52:16 AM »

As far as Pro Circuit,they have the MX pipe that you have now,and the platnium2 which is like the FMF gnarley pipe.Correct me if Im wrong,but after the fuel leaves the reeds its stored in the inlet track/crankcase under slight preassue from the underside of the piston coming down,then the fuel leaves the crankcase to transfer ports to the cylinder to fire,theres more of fuel/air available with the spacer.

Dan_AKAL · « **Reply #8 on:** August 18, 2004, 12:43:32 AM »

A couple of days ago I didn?t have any idea what a reed spacer might do. Now after a lot of research I think that I am getting an idea of what is going on here. By installing a spacer between the reeds and the crankcase a larger volumetric area is available in the case. The gain is pretty large considering the size of the case. Not only does it gain the area of the spacer but also moves the reed cage further out of the case. In addition to gaining the area the aerodynamics of the mixture flow is improved. Without a spacer when the reeds open the first thing the air mix would hit would be the cylinder wall. I would think this would vary from one engine design to the next and I expect that a great deal of research has gone into how reeds are placed and the design of the intake manifold. Anyway, by moving the reeds further back with a spacer the airflow into the case isn?t quite as restricted. What are the benefits and where would they be noticed? Without first hand experience I can?t determine this. One thing that comes to mind quickly is that the longer air and fuel are mixed together the better the saturation. By increasing the area the mixture would remain in a suspended state longer thereby increasing saturation. The saturation gain I believe would result in better overall engine efficiency. This would probably be noticed more so at lower speeds and immediately off idle. However, I could understand how it would be seen throughout the entire engine RPM range. I can?t believe that any manufacturer would size their cases where there would be a marginal volumetric area. Carb size, intake manifold size, and case size would play a very big part in this. However, I can see the benefits of the larger volume of air mix in the engine. Maxima has a very good diagram at their web site of oil migration through a 2 stroke engine. Have a look. It is very informative.

As for the pipe and silencer I am somewhat limited on availability for a 99 KX250. It is sort of stay with The PC stuff I have or get a Gnarly. Since I already have the PC stuff and it works I?ll probably give it an honest try. If I am unhappy then I?ll look at the Gnarly.

Thanks again for all of the info. I?m sure there will be more questions before I get finished with this.

Dan

teamgreen500 · « **Reply #9 on:** September 27, 2004, 12:34:32 PM »

Later model cylinders fit the 99-00 motor with astounding results. Team Green has built motors using your bottom end and '02 cylinders. This makes a motor that's unbelievable from SX to X-Country.

The best help for your scoot is in the susupension department. You need to get the spring-rates and dampening right for your "Off-Road" conditions.

Good luck,

Manny

mikesmith · « **Reply #10 on:** September 29, 2004, 07:44:43 AM »

Any one run or know someone thats run the PC 2 pipe on the 03 or 04 250?

Rick · « **Reply #11 on:** October 01, 2004, 09:10:34 AM »

Manny!?! Where you been? We all thought you jumped over to a red ride.

Rick

mikesmith · « **Reply #12 on:** October 02, 2004, 07:17:34 AM »

Hes been on Thumpertalk,seems to like his little KLX.

Bandit9 · « **Reply #13 on:** October 31, 2004, 01:16:01 AM »

Dan, when are going to make another SERA race down here in the south? I am looking forward to the Perry Mountain Enduro this weekend. My 310 is going to eat up those little hills.

Get the FWW, it is the ticket. I have an Eric Gore 310 kit w/ a 12oz FWW on mine and motor is so smooth and torquey it is like a 4 stroke. Except it starts first kick every time and it is light. This thing will destroy the tight woods. I am running the stock pipe w/Turbine Core II Spark Arrested Silencer. Pipe is uneccessary w/310 kit. Running 14/49 gearing. Looking at putting on an EFM Auto Clutch in the near future, just to make the bike even more idiot proof. Scott's stabilizer is going on next though.

Dan_AKAL · « **Reply #14 on:** November 17, 2004, 01:40:34 AM »

Bandit I raced the Rockford Enduro and was there for the Clanton HS but Hurricane Ivan rained it out. Rockford almost did me in with a knee injury and I don't know how competitive I would have been at Clanton. Heck, I almost didn't finish Rockford but just sucked it up and rode as hard as I thought I could. I flew 4000 miles to race that enduro and I wasn't going home a quitter! Hard to ride those things when you have to keep one foot on the peg. I must confess that I don't have a green ride down there. I ride a KTM 300 EXC when I go south. I would like to have made it for Perry Mountain it being the stomping grounds of my youth. Maybe next year.