Hi all.

I'm pretty new to these forums as I have only owned my 09 KLX 250 (UK Spec) for about a month now. I have read many posts on here and have found a lot of great info but I have read through a lot of posts also to get all the info I needed. Many of the posts on here relate to the Carb'd US spec bike so I thought I would do one to help for UK owners all in one place.

As we all know, the stock KLX 250 is a great bike but it needs to be woken up a little in order to get the best out of it. Here is a list of what i have done so far to mine with the effects of each.

First off, I am 5ft 11 and I weigh 13.5 stone (189 pounds) and I own this bike for mostly off road riding, I only ride on the road on the KLX to get to the off road destinations. These mods are all done to make my bike much better off road whilst still giving reasonable performance on road .

Here are the easy mods to do.

1. Derestrict the top end of the bike by unplugging the clutch switch. A link on how to do it can be found here -- How to soup up KLX250 EFI the easy way - Bike Chat Forums

As stock the UK KLX 250 is restricted in its top gears to 7500rpm but the bike is built to rev to 10,000rpm, this mod fools your ECU into getting rid of the top gear map, meaning you have great accelleration in the top gears to enable overtaking. This mod will NOT damage the bike in any way and is excellent, it gives the bike much better performance at higher speeds, will enable you to go 80 mph and takes 5 mins to do!!!.

2. Change the stock tyres ASAP as they are rubbish for UK off road. We mostly have muddy conditions wherever we go and the stock tyres will make you crash!!!! They are brilliant tyres on the road but have very little grip when riding off road. You can read endless posts in endless forums about tyres but you will mostly find people mention tyres that are not availabe in the UK (Kenda's, D606's). After much reading on the subject I have gone with a pair of Michelin AC-10's - Front 80/100 21, Rear 100/100 18. So far I can highly reccomend them, the grip is excellent in pretty much all off road conditions and they are not that bad on the road (For Knobblies). I have ridden at 70 mph with these tyres on and it felt OK. Once you get used to the knobbly wobble, they are fine. I don't know how long they will last but I don't care for the grip I am now getting.

3. Adjust the suspension settings for your weight. If you know about race sag read on if not view this. Set your Race Sag

I measured my race sag first then adjusted the suspension clicks to set the best sag. For my weight (189 pounds) I am currently using Rebound - 8 Clicks out and Damping - 10 clicks out. This gives me a race sag of 93mm. This was a bit of trial and error but these settings seem to be right. Finally adjust the fork damping for yourself. The fork suspension is very soft as standard and if you weigh above 150 lbs you need to adjust it. After trial and error I am currently set at 2 clicks out from the hardest setting on the forks. These settings feel pretty good and have made the bike handle alot better. I am more confident now of hitting jumps without the worry of bottoming out.

4. Our bike in stock form has a 14 tooth front sprocket and a 42 tooth back sprocket. Change the front sprocket to 13 teeth ASAP. This gives much better accelleration in the lower gears and is a must if you are ridng off road alot. The bike does not have enough power in 1st or 2nd to spin the back wheel without riding the clutch so this mod is needed to give more low down power. This mod will not effect top speed too much, I was still hitting 75mph ish with the 13t so I would do this as a minimum. This mod makes a HUGE difference. I personally am still wanting a little more power low down so am going to put a 45 tooth back sprocket on the bike too (for those that dont know, removing a tooth on the front sprocket is the same as adding 3 teeth on the back sprocket). This will then make me able to spin the back wheel in 2nd gear on tight hairpin type corners. Even with the 13 / 45 sprockets I would still imagine the bike will do 70MPH anyway (with the first derestricting mod done). I will update when I have it fitted some time next week.


These are the 4 basic mods to do that will completely change the bike. Obvioulsy there are more to be done but then we start getting into more expensive territory (Exhausts, Suspension springs, Re-valves etc etc).

If anyone else has done any extra mods they think are worth a mention let me know, I am always up for modding my bike further

Thanks

Ledgini

 

Hi Ledgini, nice to welcome another efi klxer to the forum!

Big bore kit & a programmable ECU or piggyback controller....the low end torque & high end power is absolutely night & day!

I was astounded last week when I swapped my bike for a mates & we went for a long ride, he has a 2bros, clutch connecter trick & a juice box fitted with softer stock suspension....OMG it was such a big difference & made me so happy with my mods, it immediately made up for all the money & time spent with one big on my face.

this thread went on forever, with 4 of us efi guys using different controllers to get our bikes running fast:
https://www.kawasakiforums.com/forum...-klx250-36083/

 

I have that same bike EFI.
I could tell you 100 items for improvement, but I'll tell you the simplest and cheapest.
1 - Inside the throttle body there are two gates: it eliminates that is held by a single screw. Watch out, leaving the wires connected to keep it running the servo and no error in the ECU, simply remove the screw that holds-care, Loctite, and has removed the lid. This bike will go up even better than rpm.

2 - If you can make the change complete Marcelino cam, exhaust and intake. In your 250cc is totally recommended. He has no contraindications, except the mechanical complexity, and provides more power than any exhaust or fuel injection system. If you're afraid to make modifications to the exhaust cam because of the ACR, at least do it in the intake.

3 - Buy a used KLX300 airbox and replaces the original EFI. It is a bit tricky to fit because the nozzle touches the shock absorber spring, but it is doable, I have it and I'm not Superman. It is much more aerodynamically efficient. Removes all gas recirculation system, but retains the sensor making the ECU data in the airbox. The intake noise without the airbox snorkel + Marcelino change is greatly reduced.

4 - If you install a UNI air filter + exhaust system + plug iridium are small improvements that also contribute to greatly improve the bike.

With only the changes you say you will already have a more powerful engine than a XR250, for example.

 

Welcome to the forum Ledgini.
Keep us posted on that 13 45 sprocket combo when you do it. I am about to make a change and would apreciate some users feedback. I am using a 13 42 combo on my EFI 300 and need some more low down. Top speed I am not bothered with as the island is one big mountain. Anything over 120 kph will land me off the edge and in the ocean.

 

Hi Graham. I have already done the back sprocket Mod, I actually went for a 44 tooth back sprocket in the end. It is much better than just the 13 front alone, the acceleration of the bike is excellent, although you do need to short shift. Top speed it will still do 70mph although it is at 8000rpm there so a little buzzy. With the AC10 tyres on, you don't really want to go over 60 ish anyway due to the wobble. I would highly recommend it. I wont be changing back

Since posting the first post I have also put the Edge tail light and tail tidy on, short levers & renthal race grips. In the next few days I am changing the suspension springs as they have both just arrived from the states. 5.8Kg Racetech Shock and 0.46 MotoPro fork springs. Once this is done this bike will be awesome.

I will let you know next week when the springs are installed.

 

.46 Springs are the way to go. Gets rid of that ridiculous dive each time you touch front brakes. Easy install as well. Do it the cheaters way. Put the bike on a centre stand. Remove bars and move them forward out of the way, leaving all the levers in place.
Do 1 fork spring at a time. Loosen 2 upper clamp bolts and loosen cap. Get a spanner in between springs and remove cap. Need an extra pare of hands to help with a long nose plier to hold the rod so it does not slip back down, as well as to hand you the new spring. Just wind the old spring out with the spanner in place, and wind the new spring in while holding the piston rod with the long nose pliers.

If you attempt both at the same time you will need more hands, as well as the fact that the if you remove both cap bolts the front end collapses, then you need some way of lifting the front end to extend the forks again and compress the springs.

Back to the rear sprocket, what brand did you use, how much clearance is there with the chain gaurd. Did your stock chain still fit?

 

^^^^ THAT is a damn good idea on how to change out the springs without alot of headache. Thanks for sharing.

 

For the back sprocket I think I went Sunstar, its just a general steel sprocket. Decided against the likes of Renthal Aluminium as I would rather have steel for longetivity. As for stock chain, no, it had to be changed. It has plenty of clearence on the chain guard though. I bought the chain and sprocket from wheeling cycle supply (as well as some other cool stuff)
If you are thinking of doing it graham, just do it. It really is the way to go if your bike is mostly used off road. I dont care about top speed, as long as I can go 60mph to the trails I am happy.


I have my CBR600 for going fast

 

I went for the SuperSprox Stealth rear sprocket, it's got a hardened steel outer & a light aluminum center. There a bit spendy but ultra long lasting & have got the bling factor. After 5 months it still looks & feels brand new!!

 

You got a bunch of bling going on there Joel. Love that chain guard. Will it fit a larger sprocket?