Does the klx 250 S come with a governor from the factory? We could not get the motor to even come close to redline. We made some mods per some of the post on this website, and it has had a dramatic change. Expecting a new slip on from two brothers today. We will install and do some carb mods as well. I am also changing the front sprocket to a 13 tooth. Appreciate all the experience here. It is fun to read all the ideas.

 

Great question. I'm looking into this myself. If there isn't another problem, the KLX motor will spin to the redline, then it will hit the ignition cutout rev limiter, but power seems to taper off above 8,000 rpm. It's almost like a soft approach to the limiter. The dyno supports this theory, but I haven't gotten to the bottom of it yet. I would like to see an ignition curve throughout the rpm range on our bike as compared to, say, a KLX 300. I have questioned Jerry Leighton about this as well, but most of his experience is with the 300. He doesn't have a '06 or newer 250 to test. My 331 mods are geared for a smooth power delivery throughout the rpm range, but should continue to build to the redline. I thought being undercarbureted was the issue, but that has not proven to be the case. That narrows it down a bit, most likely to the ignition system. I hope to get to the bottom of is myself, so any real data or experiencial insight would be appreciated.

Bill Dragoo
Norman, Oklahoma
Kustom Kraft 331, Lukesracing porting, Web Cams, Bill Blue TM 34/FCR 35 carbs, Muzzy with insert, no airbox lid. Dyno runs are almost identical with FCR 35 and TM 34. Falls off above 8000 rpm. Makes me wonder what's lurking between 8000 and 10,500. Could be very good if I can find the key to release it.

 

I'm running the HMF pipe with the Yosh quiet tip that I've got wrapped with Moose fiberglass, KDX200 snorkle and the TM34. I changed to the shorter pump rod, and acceleration from above 6000 is much better. I still have a bit of surging at steady state throttle, with high load, such as 6th gear at 70 mph. It's still lean in some spots. I'm moving from a 137.5 MJ to the 140 MJ. I'm at full rich (lowest notch) on the TM needle, I've ordered the next richer needle, but so far no luck. We're not sure of the #.
I wonder if at the higher rpm's if the header pipe is the restriction. But the first thing that comes to mind, at least with the carb change, the TPS being out of the loop. I wonder since it's unplugged, if the default setting doesn't deprive the ignition from doing something at those types rpm. Just thinking out loud..?

 

Has anyone thought about the bike isn't getting enough gas from the tank @ WOT ? I thought on this because me kl250 Sherpa has a very blue head pipe. I'm running a 132 main,A/F screws out 1.5+- turns,i think,everything else is stock. I haven't had a chance to pull the plug yet.
It's been while since i tinkered with it.

 

Good thought, Transman. I hadn't considered a fuel flow issue. But I don't think that's it, mostly because the mixture doesn't show to go lean on the dyno runs. It maintains a good balance all the way up, even as the power drops off. I'm sure that you would have come to the same conclusion had you been able to see the chart. I'm trying to post it, but I keep getting a message that says, "Document not supported." Once I figure out what I'm doing wrong, I'll put it up for everyone to see. Meanwhile, I still need to learn how the ignition is mapped out. It's just a hunch at this point, but I have a strong su****ion that we're losing advance above 8 grand. Anybody have any data to contribute???

Thanks,
Bill Dragoo
Norman, Oklahoma

 

Shadetree what was Jerry's answer for the 300 timing? Did he say it was losing any advance at high rpm? A couple people have figured out the 300 cdi conversion wiring issue. Since the 300 doesn't have a tps using that box would rule out any sensor issues. Somewhere on the forum there is a chart stating the bacis ingition timing specs of the 250s, 300r, 250r, and 250sr cdi boxes.If you ask nice tremor38 may talk to his dealer about what is going on at higher rpm inside the different boxes, he seems to have first hand knowledge on some of them. Shadetree when did you go to the fcr35? Could you tell any difference on "seat of the pants dyno" between the two? Did they flow bench your head when they were finished with the porting? I am wondering if there might be something causing some turbulance at higher rpm's that could be traced back to the port job. Also what is the grind of the cams? Were they for low to mid range hit, or were they supposed to be for the top end?

 

Jeff,
The cams were the "Larry Roeseller" grind. There were two to choose from that Larry had used on his race bikes. One required replacement of the valve springs due to higher lift than his earlier version. I got the earlier version. It is designed to come on at a lower rpm with strong midrange, but it still shouldn't sign off quite so soon. To my knowledge, the head wasn't flowed, but Lukes Racing has vast experience with race motors and deemed valve size and porting to be more than adequate for the 331 at redline.

Jerry didn't have any timing specs, but your idea of getting Tremor to track down those specs is a good one. Tremor, if you can here me, please call...

I put the FCR on two weeks ago. I did a seat of the pants jetting before the dyno run. I knew it was still a little lean at low rpm, but thought it was ok at wot. That turned out to be spot on. It makes a little less power up to 4000 rpm,in the range where it's lean,than the TM34, then overlaps almost exactly with the Mikuni curve.

As for "seat of the pants" feel, it feels a bit stronger with the FCR. I raced a friend with a DRZ 400, modified with a FCR 37 and exhaust upgrade...don't remember which pipe, and beat him soundly. We did a 200 yard run in a field first, then again on the street with the same results. We tangled last month on the Hillbilly tour and he pulled me by about a lengthon two or three scraps on gravel roads. I attributed the difference to the FCR, but my bike was not broken in at the Arkansas ride like it was last weekend.

It's a mystery so far, but I intend to get to the bottom of it before it's all over. Meanwhile, it runs and rides pretty danged nice as is. Thanks for your input.

 

Here is a cut-n-paste of a previous post I made. The info you seek on the rev limiter is near the end of the post in red letters. I don't think any type of 'governor' is coming into play at the RPMs your are talking about because the soft limit doesn't kick-in until 10,500RPM (hard limit at 11,000). When my bike hits the rev limter on the dyno, it's very definite. You can hear it, andthe curveturns into a cliff. I have no problem getting up there either. My carb is a little bit different animal, but I'm not sure if that accountsfor thedifference.

イグナイタ種類

点火時期（BTDC)


KLX250SR
5°/1700rpm
40°/5000rpm


KLX300R
5°/1700rpm
40°/3000rpm


KLX250ES
10°/1300rpm
35°/5000rpm


KLX250 prior torev limit
10°/1300rpm
35°/5000rpm


KLX250 withrev limiter
10°/1300rpm
25°/5000rpm[align=center][/align]Just some added info on ignitors for those who are interested. Above infoUSED to be in table format but I lost that during the cut-n-paste. It shows where minimum and maximum advance happens for the various igniters available in Japan. The ignitor of choic for the KLX250/D-trackercomes from the KLX250SR, which I think is pretty much the same as the old KLX250R in the U.S. According to this chart, the KLX300 ingnitor is has already advanced the timing to 40 deg BTDC by 3000RPM. The website I got these figures from was throwing aroundan acronym called MBT (Minimum advance for Best Torque). If you notice the figures next to the 250SR ignitor, you don't reach 40BTDC until 5000RPM which -according to them- is to optimize the low-end torque/responsiveness at low revs. That's probably not as important on the KLX300 because the larger displacementprobably off-setsany loss of low-end grunt. The documentation also goes-on to say that the rev limiter on our bikes, begins to cut back on the spark at 10,500RPM and completely kills thespark at 11,000RPM. With the KLX250SR/R or KLX300, there is no rev limit.[/align][align=center][/align]That's about all I have for trivia right now. The site had dyno graphs prior to letting their domain expire. Now all I can get is the cached text. The largest gain they had was about 1/2hp. [/align]

 

Thanks, Tremor. Do we know if that info relates directly to the US KLX 250s? It should of course, but I can't help but wonder. I may contact Web Cams again and see what their take is on it.

Bill

 

They all come from the same factory in Tailand and all have the H6/H7 in the model number, so I would guess they are the same.

I just looked-up ignitor part numbers and they arethe same on both JN an US models (21119-1579). I also can tell you that the engines and fuel systems have the same PN's, minus the carb deicer.

Here's my dealer's (and my) take on the large bores when dealing with thise bike. It doesn't rev quite as high and the power curve tapers off quicker than the 250. I don't know whether that is a result of the higher piston mass or what, but that's what we've seen at the dyno with the 315cc kits available here in Japan. That's not to say that the large bores don't make more power, they do. The biggest change is on the low endthough uppermidrange though.Maybe someone who's had more experience withoversquare boring canjump-inand enlightenus as to whether thechange in the power curvemight be related to that. I do know what I've seen though.