I'm learning... I also find the whole timing numbers for what is needed to calculate the head pipe ID and length using rsmotorcycles.net to see which pipe I should use.

Is there any numeric ties between the cam specs and the predictability of where the horsepower peak should or could be?

 

that is sg very difficult to calculate, because there are other factors such as the exhaust and the carb. But generaly, when adding overlap moves the power band at more rpm. How much, depends on the overlap. Every cam manufacturer must give the power band of the cam, so i d suggest that you sould ask the cam manufacturer..

 

Camshaft spec info Hot Cams Products, Inc.


- It'd seem choices for the KLX250 are limited to a pair of Webcams or moving the stock cams per MCM aren't they? Agonizing over optimum cam specs isn't going yield a new cam option unless Zombie is going to start making KLX250 cams

Buuut going back over what we do have and looking for hidden HP could produce results?

Taking the time to determine air box efficiency, trying Bernie's timing mod maybe by elongating the pick up coil's mounting holes, fixing the air box's sharp edged spigot entry, and having the 36mm carb work even better via splitters on one or both ends are a few suggestions. Mostly things I've mentioned before but interest has been zero. Nothing new though really, just commonly done hot-rodding stuff and paying attention to details that goes on all the time in MX bike forums for example.

Most of these things could be limiting the effectiveness of the typical mods

Did Kawasaki design the air box to be a 100% efficient positive addition to the intake tract; or was it (as most are) just made to fit into the frame space left for it, and enclosed as much as possible to keep the air filter clean and dry? (Guess)

Same for all purpose environment and warranty friendly ignition timing

It's out there

 

Let Thunder Products speak for themselves:

Quad Flow Torque Wing
(Patent Pending)
Increased power across the RPM range, awesome throttle response.
Easy installation, no tuning required. Stainless steel construction, no moving parts





And Motocross Action:

MXA TEAM TESTED

THUNDER PRODUCTS KTM 250SX
QUAD FLOW TORQUE WING

WHAT STANDS OUT? Here's a list of things that stand out with the Thunder Products Quad Flow Torque Wing.

(1) History. Thunder Products Quad Flow Torque Wing is not the first winglet to be installed in the intake tract to improve air velocity. You might have heard of Swirl-Up, Power Now, FMF Snap, Tornado, Intake Twister or the Boyesen X-Wing. All of these ideas focus on realigning the airflow through the carb throat.

(2) Concept. Motorcycle engines are air pumps. Air is drawn in, compressed by force, expanded by the combustion and expelled by the exhaust. Contrary to popular belief, fuel does not explode in the combustion chamber. Instead, the engine processes air, mixes it with fuel and burns the fuel mixture in a controlled manner to expand the air, which in turn pushes the piston downward to draw more air in. Once you accept that an internal combustion engine is an air pump, you can begin to understand how important the transition of air through the system is.

(3) Winglet theory. Intake-tract winglets work like an airplane wing. They take tumbled air and straighten it out. Their goal is to achieve laminar flow. Laminar flow is the smooth, uninterrupted flow of air over the contour of the wing. The Quad Flow Torque Wing is designed to reduce drag at the air's boundary layer, reduce surface-friction drag, equalize the pressure gradient and increase air velocity.

(4) Differences. Virtually every intake winglet is different. Some, like the FMF Snap, mount in the air boot's velocity stack. Some, like Power Now, mount in the bell of the carb, and some, like the Boyesen X-Wing, extend deep into the carb's venturi. The Thunder Products Quad Flow Torque Wing is unique in that it mounts on the cylinder side of the carb's venturi instead of the airbox side. Why? Because it does not want to split the airflow at the fuel nozzle or disrupt the atomizing process at the source. Instead, the Thunder Products Quad Flow straightens out the air as it exits the carb. Additionally, it protrudes into the reed-valve area to keep velocity high and eliminate back-pressure turbulance from the flapping reed valves.

(5) Performance. Every test rider felt increased throttle response at low rpm, a smoother transition from the low end to the midrange, and a more flexible powerband across the range. Power take-up felt crisper, and, best of all, the dips in the power curve were ironed out. The benefit of increasing air velocity is that more air carries more fuel, which results in more effective combustion. It is a win-win.

(6) Installation. You have to send your carburetor to Dick's Racing to have some minor machining done to fit the winglet into the front side of the carb throat. NOTE: You can purchase from Thunder Products and install yourself.
__________________________________________________ _________________________

WHAT'S THE SQUAWK? You have to send your carburetor to Dick's Racing to have some minor machining done to fit the winglet into the front side of the carb throat. NOTE: You can purchase from Thunder Products and install yourself.

Motor Cross Action Magazine Star rating



From my standpoint, I have only been derided for any comments, but after your "chest thumping" I will say the following.

I don't have much options for the air box since I will be off roading and cannot cut holes in the sides allowing significant influx of mung and drool (for the benefit of those of you who remember that from Dirtbike!) or sacrifice the style of air filter in it for something that has not been proven for off road. I don't think you hit those limitations since you are playing with the supermoto aspect. By measurement and calculation the KDX200 inlet has an area as large as the inlet tube between the air box and the carburetor. Without sending the parts to a flow specialist I have no idea how much flow it will allow and considering what the costs may be I don't see that happening in the near future. I don't have any idea of how much flow the engine can actually utilize. Clearly there is a limit, but again the cost to learn it is prohibitive to me for my use.

So I work the odds by watching what works for others, following and trying what past experience says should work, all the while keeping in mind why I have the bike - off-road riding. The Marcelino mod was a good off road trick for more mid-range, the big bore even more enticing with that fat flat torque curve. Off-roading lives and dies with rideability - useable power, not peak power. I'm thinking a number of others here fit that bill too.

Of course there is the beauty of multiple bikes. If I want some horsepower the KLX650 does a pretty good job.

Honestly if I was looking for max HP I'd be researching what flat trackers are doing since they live at high rpm. Do they even bother with an air box or do they can it for a K&N, how long is their intake tract, who does their cams, what size/length exhaust do they use. That's what I did with the SR500 - what did they do on the flat trackers for horsepower that is within my means.

If there isn't any good information to be gleaned from the Thunder Products site and MXA, don't blame me. It made sense to me, I've used their product and may likely pick up on their splitter for the quality and research backing it up. My comments aren't for information, just why some of the grasping for the last horsepower straw may not have value to me and others like me. There are just too many other things like better suspension out there. I'm seeing the priority list as possibly the suspension first, big bore second, carb third. If I run into someone with a vacuum flow set up maybe they will test out the intake tract, but again, don't see it happening.

Best of luck with your intake work, I have looked and it is interesting. Maybe I have my air box off sometime I will take a look at what can be done. By the way virtually all off road/dual sport bikes have lousy inefficient air boxes. That has been pretty much acknowledged over the years, especially on some models that smash the air box - carb tube into some oddball shape. It is just plain near impossible to make a good air box within those limitations. Kind of a "do the best you can with what you got" thing.

 

KLX678, how bout a thread on the Dial-a-Jet. Install, use, and altitude compensation abilities...?

 

I am not sure how serious you are, but I will work on doing so in the event someone may want to consider using it. I'll have to tear the tank and stuff off again since I installed the Dial-A-Jet in June. It will take a bit of time. I've already posted on my experience with the 650 and noted some on my brother and my experience with the 250, but will do so again to get pictures and indicate how I installed it. Not a tough job by any means. The worst thing is putting the air filter duct (Kaw's name) back between the carb and air box.

 

I wasn't chest thumping, just admitting the mod ideas I'd listed were (except for Bernie's timing mod) suggestions I'd talked about or worked on before and I am still trying to stimulate member interest. It is the KLX250 thread afterall, so the idea of just riding a larger bike really doesn't address the owners who are looking for more power. Typically suggestions are made to the general population on a take it or leave it basis. It's not necessary for the average member to list at length why it doesn't work for him or his riding application.

There was discussion here in this MCM camshaft thread about options/effects regarding cam duration; I was reminding everyone that the cam options are limited, but there are other avenues to be explored. Why spend big bucks on cams if your air box can't get enough air? Or if the snorkel allowing enough air; regardless of measurements? I'd say it's not just measurements but demand that has to be factored in.

The 250cc engine needs almost 20 liters of air per second at high rpm, and the 351 need almost 30 liters per second. Calculate how much inlet time per cycle there is based on cam duration sometime?

If your snorkel can't access enough air because the path between the atmosphere and snorkel entrance doesn't allow adequate flow, then your snorkel measurements don't solve the problem. It's easy enough to pull off the seat and see if the bike feels faster or race against a buddy.

Even for the off road/river rider there are ways of admitting more air without sacrificing air filter protection. So some experiments with the air box's overall breathing ability are still valid for any type of rider wanting more power. The subject of more HP does come up regularly here so... for those who want to make their KLX250 more efficient instead of just hopping on another bike .. these are the suggestions. (there aren't many avenues left are there?)

Myself I wouldn't want that 4 sided torque wing in my carb. I think it'd play some havoc with the jet spray coming out of the floor of the carb. Maybe if I was attempting to climb Widowmaker it'd be something I would look at. Or maybe for use with the 40mm carb. I am so pleased with how my little splitter worked in 2 different bikes that it's actually satisfied my mod fever for the time being. It's kind of perplexing but I'll get back to it sooner or later.

Push yourself away from the keyboard and try the SNAP or QFTW and report back to us ?

 

Of course no knowledge or opinions I have are of any value...

But when it comes to the quad wing I'll take the testing of MotoCross Action (MXA) over your opinion pretty much any day. Seems they have a fair amount of experience on variety of motorcycles in their time. Thus the reason I figured to defer to their comments. They seem to have had a pretty high opinion of the IntelAjet too.

When it comes to the original Dial-A-Jet, I'll go with the guy with the Ph.D.

The Dial-A-Jet system was invented by Dennis Dean, Ph.D. (Doctorate in acoustics). Mr. Dean held over 120 world motorcycle drag racing records and several Bonneville records. The Dial-A-Jet concept was used on all of these machines."

There is enough media verification to back up the products. Along with my personal experience on the DAJ and possibly the quad wing soon.

As for more power, sure everyone wants more, but it has to be useful for their purpose. I want more power in my bike, not so much horsepower, but a fat band of high torque since tight trail riding calls for the ability to pull strong over a significant range. I'll take 25 horsepower with 90% max torque available from 3500 to 8000 over 30 horsepower with 90% max torque only available from 6500-8000 rpm any day. It has to be tractable power. One negative pointed to on the WR250 is the peakier power delivery for a new or more casual rider.

Others do have experience that may contradict to what you may believe to be possible. You want discussion allow for the fact that some of us have either done some of what you're playing with or been around it. I may include my background because it provides some insight into what and where I've learned. I've also admitted to being wrong before or commenting that I've learned something new. To learn is the reason for my following a number of the threads.

Again, I don't have the money to throw at every whim. I have to do the research to make as educated a choice as possible. I'm not going to have two or three shots. I don't have the time or money to cut up my air box for experimentation, nor do I see how I can do it and still have adequate protection in deeper water and such that may be an obstacle when riding.

As for the snorkel, if it isn't being crushed I doubt there is much issue with the seat, the stock snorkle is definitely smaller in cross section so it will have an issue, the reason I did the measurements - to see if the 220 snorkel had the same cross sectional area as the carb at its biggest point... it does.

By the way, since the 650 does no hard off roading there is no snorkel in it, the lid is cut open a bit bigger. It is too loud without any lid and borderline as cut. There was no noticeable performance change after cutting the lid. The intake roar is nearly as loud as the exhaust is when on the seat. The air filter is actually smaller than that on the 250, so it seems the 250 has a decent sized filter, both have lousy air boxes. Maybe I will talk with Foggy and a few others of the KLX650 group to see what a half tooth off on the cams does for it. Get with those with more experience before diving in.

That bike was one I did dive in, but knew what I had. In 2000 we rebuilt the top end, the mechanic had a Vulcan 1500 piston - same size wrist pin. So I did all the measurements to verify the valve pockets were deep enough relative to the wrist pin to clear the valves, the pockets were equal in positioning relative to the center of the piston, verify the squish band would be sufficient. I did, it was, and we took a chance having it bored out from 100 to 102mm. This was before anyone put out any information on it being done. Then I questioned doing another OEM automatic tensioner, asking the mechanics. We mulled it over and one said "drag racers use manual tensioners". So I converted the OEM unit to a manual unit. That was 34,000 miles ago. So you see, I do make some measurements, research, and take an educated leap of faith. There's a DRz400SM shock in the garage to fit to the bike sometime.

This summer I struggled designing the proper tensioners for a Hyosung long distance for a rider in Australia. Recently here I took a hint from a few riders and made a low cost air injection block off plate - $9.50 without the gasket. A low buck part for the guys that don't have the time, experience, tools, or desire to make the part can get a quality part, for less than a ten spot! Unfortunately now I have to take my bike apart and fit one just because, because I made it and own the bike. I hate to take a bike apart that is running fine.

I want badly to try an FCR37 on the 250, since they can be had for 1/3 the cost of the Mikuni but don't want to waste the money if it's going to be a pain in the butt. I'm not a glutton for punishment when it comes to my bikes.

I do push away the key board. I do actually work with stuff. Surprise!

 

hahahahaha!!!! If it ain't broke, fix it till it is.

 

Not yet..