Update on the update on the 350/390 SXF

Turns out I do have an overheating problem at least when I ride real tight (2nd 3rd gear) trails at altitude (5000 +) and plus eighty five degrees. All that plus little air movement through the radiators was perhaps causing the fuel to overheat making pop stalling an issue. I’ve been running waterless coolant which can be a benefit on one hand but can also be potentially a big problem on the other. No radiator boil over can give you a false sense of security and the heat just continues to build.

I decided to install a fan kit but found out apparently no one sells a kit that will work with an IMS over sized tank installed on a 350SXF. (I would assume the same would go for the XCF as well) Accerbis does make a tank that will work with a kit, but in order for me to install a standard fan kit I’d have to buy a new gas tank, which on one hand isn’t bad because disconnecting the fuel line to either remove the fuel tank or to change the little micron fuel filter is difficult with the IMS tank. Well, turns out replacing the IMS gas tank to install a fan kit isn’t the only problem, seems the output of the SXF stator isn’t enough to properly charge the system with a fan. At this juncture I wasn’t willing to spend the time researching a fan that uses very little power that I can cobble together into a system. With an electric start only and a Rekluse I don’t relish the idea of adjusting the clutch so I can bump start it if I forget to turn off a fan. Spending five hundred dollars plus for a tank, fan kit and stator for a problem that may only occur occasionally didn’t make sense to me.

I did decide to try the higher output water pump KTM sells and see if that would solve the problem. The kit was about $100 and was easy to install. I’m not sure how much it increased the water flow but looking at the difference between the stock impeller and the new one I’d say at least double perhaps triple. 

I’ve now ridden the same tight trails without experiencing the same problem, it wasn’t quite as warm though but hopefully this solved the problem, only time will tell. Installing the water pump kit would be a good investment for anyone having KTM borderline overheating issues.

Doug 21J



KTM 350SXF long term report  

Back in August of 2011 I wrote an article entitled “KTM 350SXF could this be the ultimate MX/Trail bike?”  Well three years later I have some answers.

Yes I still have the bike some one hundred sixty plus hours later. I can tell you one thing it was not for me, and that’s a motocross bike. The handling was not the issue the way I ride and the power was. I’m a bigger guy at 210 plus gear and it just didn’t have enough power down low to mid range for me. The bike needs to be ridden more aggressively like a 250 in order to get 450 like power out of it in those high RPM ranges, I’m more of a torque it around rider. 

But as a trail bike, cross country race and enduro bike it has been nothing short of great. I usually only keep a bike a year or so, but I haven’t gotten tired of this bike and quite frankly haven’t ridden anything else that would make me want to sell it. Because of KTM’s new generation frame the 350 feels very light and nimble, the four stroke motor has little fly wheel effect so when you back off the throttle for a corner the motor doesn’t push you into the corner, but it still has more engine braking than a two stroke. And like most four strokes it feels very planted especially in the rocks and going up hills.

I bought the SXF over the XCF model because of price, the XCF was just being introduced at the time so there weren’t any deals or used ones around. SXF’s were and still maybe easier to find, have less hours on them and cheaper to buy. And for the type of riding I do the five speed close ratio transmission works very well, you have a motor that rev’s to the moon so you’ll have more than enough top end in short bursts unless you need to run it wide open in the desert.

I’ll recap the things I did to it initially in 2011.

Rekluse Core EXP (I found for me the bike was extremely hard to ride in real tight terrain where you needed to use the clutch a lot)

Enduro Engineering Tall soft seat (I’ve actually gone back and forth between the tall seat and the stock seat I’m currently back on the tall seat)

Factory Connection Suspension (Expensive but a great investment)

Scotts Steering Damper (Pretty much a must for a KTM)

Rear brake rotor guard

Works Connection (Rubber dampened) skid plate

IMS 3.1 gal gas tank (Today I would purchase an Acerbis, much easier to install)

Pro Moto Billet kick stand.

And after having the option of trying out two different brand exhaust systems Dr. D and Leo Vince (Headers and mufflers) I settled on the stock set up, with a Pro Moto billet spark arrestor end cap, it was quieter and I couldn’t feel much difference in power.

Since 2011, I’ve installed a set of Air Cells, (They help soften the initial few inches of travel and work especially well in real tight technical sections). A KTM odometer /Speed odometer and I am still using the original 19” rear wheel. I came up with a hand operated rear brake by using another hydraulic clutch and with time found the right position for all this to fit and work; I still have the foot operated brake as well. I have a couple of friends who have hand operated rear brakes only and swear once they learned to use it can go faster especially in the tight stuff. Personally I don’t want to give up the security of the foot operated brake. I also didn’t give up my clutch either even though I have the Rekluse. There are many times when the ability to use a clutch comes in handy. Rekluse now sells a kit that will allow you to keep the clutch and have a hand operated rear brake as well.

Another thing I’ve experimented with is a set of Fast Way foot pegs the kind you can install in a back and down position.  I’m over six foot tall and for me they made a huge difference, it puts me back and more centered on the bike especially when I stand up. It also makes it easier for my size thirteen boot to shift the bike. When sitting it makes me feel more like I’m sitting in the bike as opposed to sitting on top of the bike especially when using the tall seat. And the ability to stand up is much easier no real effort. I’m not sure this set up would work at all for shorter riders and riders who stand up and like riding over the front end of the bike. The other concern was because of the lowered position would they hit rocks etc, for me the answer has been no.

My bike has always smoked on cold start up and has always used a little oil but after one hundred fifty hours I thought it was time to look at the motor besides I had decided I wanted to make a 400 out of it. After researching kits I decided to go with the Thumper Racing 390 kit. It was a simple exchange of cylinders.  The kit came with a piston, rings and gaskets. For an extra forty dollars they changed the mapping to match the new power output. One of the things I liked about the Thumper Racing kit was the cylinder was bored and coated which means better heat transfer and dissipation that you wouldn’t get with a steel sleeve.

I was curious when the motor was torn down what condition it would be in. I’ve used non synthetic Rotella oil since I installed the Rekluse (Rotella is designed for diesel motors is good, inexpensive, making frequent oil changes more affordable) The motor was in excellent condition, it didn’t need anything other than valve guide seals. Unfortunately the bike still smokes on start up and still uses a little oil.  After a few tests the conclusion was it’s a valve guide and at this juncture I’m going to put up with the start up smoking and a little oil use. As a side note my riding style of lower RPM never on the REV limiter no doubt has contributed to the longevity of the motor but it just goes to show that even smaller displacement four stroke motors can and do last a long time. 


So why the 390 kit?  First of all I was happy with the  350 power for my riding purposes I just wanted a little more torque out of the corners because of my size. My initial impression was wow more low and mid range power and it still revs to the moon. I didn’t feel any more vibration than before.  It didn’t change the engines pulse and as a result the nimble handling is the same. I’ve experienced only upside not a single down side to this point, the only thing I can see is it perhaps generates more heat. Its summer time and I’ve ridden the bike on real tight trails first with a stock coolant mixture and had some overheating issues. I’ve since put in waterless coolant and haven’t experienced and issues.

Before I went with the big bore kit I looked into just updating my 2011 motor with newer motor components because they are supposed to have seven or eight more horsepower than mine, turns out that’s wasn’t possible even the cases are different.  A friend of mine bought a 2013 350SXF to convert into a trail bike like mine and I was anxious to compare the two horsepower and torque wise. Before we were able to hook up I had the chance to ride a new 2014 350SXF on a MX track. I was anxious to see if the new bike had more low end power than my stock 2011 350. For me anyway it felt as though it didn’t have much or any more down low power. I also had the chance to ride on the same day a 2013 350SXF with a steel liner 390cc kit. That bike was a different story it had a lot more low end torque and I came away feeling I could use this bike for MX.

Wayne and I finally hooked up, he rode mine and I rode his and the results were interesting. Just like my rides on the MX track with the new 2014 350SXF and the 2013 350SXF with a 390 kit my  2011 350/390 has so much more low end torque than his 2013 350SXF it just reinforced my decision the make mine a 390 a good one. I won’t have to be thinking about buying a new bike again for awhile. The next thing I want to try is a tubeless tire set up. I recently bought a 2012 KTM 500EXC and it came with a Tubeless set up and I’ve been very impressed so far. I have a few friends who use the tubeless set up on their race bikes and swear by it. They race cross country, enduros and desert. One of my friends works closely with the Tubliss people testing various tire combinations. He rides almost exclusively in the woods and has gotten his set ups down to as low as two to five pounds front and rear and he rides a 450 and is like six four and 230. I tried a trials tire on the back of my 350 in the woods and it didn’t work for me for two main reasons I only had my 19” rear wheel to put a trials tire on at the time and the choice of tires was very limited. I’m a rear brake dragger and tend to steer with the rear end. For me the trials tire didn’t stop nearly as well and tended to push the bike into the corners.

Who knows what will happen in the next three years, hopefully I’m still riding and maybe I’ll write another article about the long, long term KTM 390SXF.

Doug 21J


The Ongoing Saga of 21J's YZ250FX

2015 Yamaha YZ250FX Part 8


The tinker couldn’t leave well enough alone, I put 81 hours on the bike in 2015. That’s 81 absolutely trouble free hours at that. Although I must say I didn’t really expect to have problems and would have been very surprised and disappointed if I had. Yamaha’s have a well deserved reputation for their toughness and longevity in the motor department. I know the old motors were considered bullet proof and the new backwards motor seems to be cut out of the same cloth. 

Late last fall I started talking with Travis at Thumper Racing about the possibility of increasing the bore, I wasn’t  really interested in making a 270 out of it I wanted at least a 290. From what I understand staying with a 270 allows the motor to rev as freely as a 250 and going bigger doesn’t allow it to be quite as free. But I’m not a rev it to the moon kind of rider in the first place so having a motor that takes a little longer to rev out but gives me more low to mid torque is ok with me. 

Turns out Travis hadn’t yet had the opportunity to have a 250 around long enough to make a kit for it, which meant he had to start from scratch. I dropped the bike off in September so they could take it apart take measurements to have the sleeve and piston made for it. They sent the cylinder and head to the manufacture so they could make molds in order to produce a piston. Some weeks later I picked the bike up and finished out the Cross Country series for the year.

When the piston arrived I took the bike back up so they could tear the motor down and bore the cylinder and send it off to be plated. That process took several more weeks and by the time they wrapped it all up it was the first of the year. While the motor was apart they took the time to check the motor and valves install new valve guides seals and the newly bored and plated piston and rings.

The plan was for me to pick it up the first of the year, but if you’ve read any of my other articles you know I basically broke my back the 2nd of January. So here I am the end of February finally picking it up. The good news about this I’ll be able to ride it.

When I got home I couldn’t wait to try it so I did a dyno butt test in my drive way (I have a fourth gear driveway) and the results of that were very encouraging. The real proof will be out on the trails but initial feel is that it’s going to do exactly what I hoped it would do, increase low and mid range power. 

My first real ride on the new 290 at Mammoth Bar was everything I’d hoped it would be. They have a short tight MX course and before I would ride the bike between 2nd and 3rd today I could ride it in third period. Up top on the trails there’s a couple of sections where you can open it up (6th gear stuff) I could feel the bikes new power pull me along from 5th to 6th maybe it felt like it took  longer to build the revs, maybe not, never the less it was pulling. There is a single track cross trail that goes between the two down hills, in the past that would be a 2nd 3rd and 4th gear section today it was 3rd and mostly 4th gear across that section. Being able to pull a higher gear across the section means the suspension works better. The other plus was with more low to mid range pull, the front end was much easier to lift up when you needed to. I didn’t notice any more vibration than before which was virtually none. I have very little time on it but I see absolutely no minuses. I’m not sure what the fuel consumption is going to be time will tell. 

I’ve put almost nine hours on it now most of them up on the trails out of Georgetown. It’s been very wet and slippery and being able to ride in a higher gear because of the new power helps with traction. And so far the fuel millage looks good. The pictures show a Pro moto Billet side stand I installed. My #13’s kept hitting the stock side stand so that’s the reason for it. One picture shows the electronic controller installed between two pieces of foam on top on the battery the other with the top foam removed.

I’ll write a part nine sometime down the road. 

Doug 21J


PS I installed a 390 cc kit in my 2011 KTM 350SFX that I owned a few years ago and used a Thumper Racing kit. I was extremely happy how that turned out so when I thought about making my 250 into a 290 I called them again. Since they didn’t have an off the shelf kit ready for the 250 I was the guinea pig so to speak. It took a lot of time and effort on their part to produce the first kit. But I couldn’t be happier with how it turned out and all the people at Thumper Racing have been great to work with. I highly recommend them.

The kit is $775.00, at present you’ll need to send your cylinder to them so they can bore it and have it coated. (Two to three week process) In the near future they will have cylinders already in stock ready for immediate exchange. The kit comes complete with piston rings and a gasket kit.

You will also need to purchase a programmable controller to set the proper air fuel mixtures, the big bore needs more fuel. They use an EJK (Electronic Jet Kit) that will come from them preset for the big bore kit. The kit is $225.00. You can contact them at


You can contact Thumper Racing at or 775-309-4956.



New YZ450FX Diet!

2016 Yamaha YZ450FX part 2 

After weeks and weeks of looking at my wadded up and dirty 450FX I was just chomping at the bit to at least clean it up while patiently waiting to heal up I finally got to clean it and look at the damage which turned out to be minimal.

While waiting to heal the Rekluse, Scotts steering damper along with the kick stand removal kit arrived. I couldn’t believe how heavy the kick stand bracket was. The other thing I’m going to remove is the kick starter with the help of a GYTR kit, that will save almost two more pounds. (I’m all in, the electric starter either works or it doesn’t)

My first ride with my recently healed body and all the new stuff on the bike was at our SOTMC (Sierra Old Timers MC) ride day at Est. I stayed on the Vet track in the back except for one brief foray on the front more difficult track. It felt good and I started out slow. After riding twice I thought the suspension felt a little hard then realized I hadn’t checked the tire pressures, I had pumped air into them the day before and thought I’ll remember to check them before I ride (Not) they both had over 30 pounds in them, needless to say everything worked much better after lowering the pressures. After having tried a fifty two tooth and a fifty one tooth rear sprocket I’ve gone back to the stock 13/50 combination. My thought was to close up the wide ratio gearing for MX, but I ended up making it easier for the motor to get to the real horse power which invites whiskey throttle. (Not a good plan) The 450 has plenty of torque and with the stock gearing have a longer steadier pull in each gear. 

Bucky of SBB who did the suspension rode the bike to check out his work. He rides a 2015 YZ450F so was the perfect guy to try the 450FX. He said he liked it a lot and didn’t feel much difference in power between the two. One thing I noticed between the two bikes was the vibration, the 450FX has very little vibration I’m not sure why exactly but it does have a new counterbalance and the motor mounts are totally different.

After removing the kick starter I decided to weigh all the stuff I’ve taken off, my hope was to have taken a good honest ten pounds off the bike to bring to an honest 252/254 pounds with fuel.

So as a recap I’ve replaced the stock battery with a Sherai, removed the kick stand and the bracket, removed the kick starter gears and replaced the stock muffler. And all the stuff added up to 10.7 pounds less the weight of the Sherai battery and the foot peg bracket. Not bad, the only things you probably wouldn’t normally do are remove the kick stand and bracket and the kick starter gears. Those kits are around $30 each.

I don’t think you could find enough ways or dollars to make the FX as light as the KTM, but it’s now 10 pounds closer than it was. A couple of riders who have ridden the FX and currently ride Yamaha 450F’s didn’t mention anything about the weight.

So now that I have it set up it’s now a matter of riding it and getting use to it like any new bike. I’ll do an update on it latter.

Doug 21J



21J Looks at the New YZ450FX

2016 Yamaha YZ450FX Part 1

The overwhelming success of the 2015 YZ2250FX led to Yamaha’s duplicating that effort only this time in a 450cc version. I thought for sure Yamaha would have come out with an electric start motocross model for 2016 but they didn’t. They’ve had an electric start bike competing in the World FIM European motocross championships for the past few years. Personally I believe part the reason is the weight. KTM has raised the bar way up there with their MX bikes that weigh around 240lbs with fuel and electric starter. The new 450FX weighs according to Yamahas specs is 262 with fuel and electric start. Obviously you can save weight by removing the kick stand add a light weight battery, remove the kick starter etc. etc. but you’re still not going to get near what a KTM weighs. Yamaha is going to have to do what KTM did which was to look at every component to see where they can save weight.

Having said all that just how does this new bike stack up; first of all I want to use this bike primarily for motocross, there are times when I’d like to have the grunt a 450 and only a 450 can offer, which means riding it in some Cross County events and the occasional desert outing. I had for a short period of time a 2015.5 KTM 450 Factory Edition (Dungey) so I can compare the two a little. I decided I wanted a bike I could do more things with, the Factory Edition is like a work of art and I couldn’t see myself flogging it around where it could get scratched.