This may be a stupid question but, does the pumper carb not require a choke because of the fuel jet it squirts when you open the throttle? Just curious as my bike requires a healthy dose of choke to fire it up if its been sitting for a few days, also what's this "hot start" that I've heard about? The other guy with the pumper on his KLX was it the 300 or 250?

 

The pumper will still have a choke, its job is to richen the mixture for starting by shuting off the air supply. I guess I haven't checked but assumed that our carbs have a accelerator pump that squirts fuel. Most CV carbs to have and I just assumed that this one does too. As far as the "hot start" goes, that is something comonly used on MX bikes. It actually leans the mixture to aid in starting when the engine is hot. ie when you're racing and for some odd reason you kill it and need to start really quick. The hot start is a lever located on the clutch side of the handle bars with a cable going to the carb. The carb must be set up for this.

 

My FCR does not have a choke. You can get it with the choke, but Jerry said the version of the carb that includes the choke simply will not fit in the KLX300 or KLX250 becuause it is too large. I was a bit concerned about this because I usually need to choke the CV to get it to start but Jerry assures me that a few twists of the throttle then crank and it will fire right up.

On the hot start - Jerry also said that's a lot less important if you have electric start so he said is wasn't really necessary. He did say it has been prepped for hot start so it can be added if needed, but he didn't seem to think it was necessary for us.

 

No AP on our CV. [&:]

 

Brian,

Excellent report! Of course, I'm kind of getting antsy now to order my stuff and follow your lead. More so every day.

I do have a question and a couple of comments.

First off, the question.


In the above picture, what is the modification on the water line for? Just an easy way to get all the liquid out of the system to remove the cylinder?

On the low end grunt or pulling power - a pumper carb is going to make a big difference. If you don't believe me, find a car with a Rochester carb on it. You can disconnect the the accelerator pump. Now drive the car - it loses all the ability to "jump" when you hit the accelerator! When you want throtle response, shoot the juice in the motor and hang on! Manufacturers have gone to the constant velocity type of carb to help meet increasing EPA restrictions and also to make the motors run at much difference altitudes. I mean a bike only needs one jet setting to work all over north America. Didn't say it worked good, it just works.

What gearing have you gone with? I'm very interested in that. I know when I was up at "Tour de Pisgah" I ran the bike from 4500 to 7500 rpm all day long and that seems to be it's "sweet spot". I'm kind of hoping that with the 331 cc displacement I can stop spinning it so fast when 'cruising' down the road. I would like to be able to cruise along at 75 mph at perhaps 6000 rpm in 6th.

I keep looking at the "Larry Roeseler's Favorite" grind for the KLX over at Web Cams Inc. I know the biggest difference you could make in a V-8 was by changing the camshaft. I'm thinking that still holds true. Of course, if you go too much lift or too much duration or too much overlap, it loses it's drivability niceness. I remember I put an "RV" grind into a 6 banger one time and it was an awesome little street car. The "Larry Roeseler Favorite" grind looks similar to that camshaft. Not a lot of lift, not a lot of duration and makes mid range power. The kind of riding I do - actually most of us do without realizing it - depends on mid range power. That 3500 to 7500 rpm band is where you spend the majority of your time.

Do you have a dyno in your area? I would love to find out what kind of power you are making. I'm betting close to 29 horses. Considering that you started with about 18, that's quite a good improvement.

Looking forward to hearing more.

 

That's the sensor for the Trail Tech Vapor's coolant temp. You have to cut the coolant line and insert their sensor section.

I'm running stock gearing - 14:42 for the reason you state. I don't like the high RPM buzzing at highway cruising. With stock gearing, you'll see 1000 RPM for every 10 MPH in 6th gear. I.e., at 75 MPH it shoudl be around 7500 RPM or pretty close. Note that this is actual speed according to GPS or Trail Tech as opposed to the stock speedometer which can be off by a lot. Mine was off by 10% so if I thought I was going 80, I was really just going a little over 70.

We do. I called them up a few months back for a price check and they charge $35 for a run. I plan to do that once I get the bike dialed in a bit and the cylinder loosened up a bit more. It would really suck to sieze up on the dyno.

 

First of all, I'm a new member to this forum and I just have to say that it's kick-butt! Thanks to all of you for such great information!

I had a KLR250, but traded it in on my KLX250, so I'm going to be modding up my bike real soon. However, I've been down the big-bore road before with my DR650 (644cc's to 675cc's) and more than a few small and big block Fords (my Mustang has a 351W stroked to 427ci). The secret to low-end power is in the head and the cams. The only problem is that changing cam profiles usually takes power away from one spot and adds it to another. So if you want more low-end torque, you'll probably lose some power from the top-end.

I did roughly the same mods on my DR650 that you would also do to a KLX250, but I wanted more. I got the big-bore kit, rejetted the stock CV carb, and experienced the same thing Nobrakes did - better, but not a great power increase. I then went to www.webcamshafts.com and ordered a new cam (there's only 1 on the DR650), and did a simple home polish job on the intake and exhaust ports. Nothing extreme here - just put a sanding roll on a Dremel and smooth out the rough casting.

All of that probably added 30-40% more low-end torque. On pavement, I can whack the throttle in 3rd gear and pop the front tire up. In the dirt, I simply can't get the big DR to hook-up, and if I did, I'd probably hurt myself! That's why I got the KLX250. After about 7,500 RPM, the power falls off, but with that much bottom-end, who cares.

Even if all you do is swap cams, you will definitely notice more low-end torque. It doesn't matter if the engine is 250cc's or 331cc's - but more cc's means more power. I checked the Web Cams website, and they make 3 different grinds for the the KLX250. You can check them out here. For low-end power, you'll want the middle cam.

I'm not trying to push Web Cams or anything, but right now I think they might be the only company that makes cams for the KLX250. I've used them before, and I have 6k miles on my DR650 with no reliability or rideability problems (starts right up, no lumpy idle).

Anyway, I'm telling you all of this to answer the question of "What next..." So if you thought you were all done spending money because there was nothing else to buy, well, don't turn down any overtime just yet. [sm=insomnia.gif] I'm just glad I actually had something to add to this forum. Thanks!

 

Wouldn't you know it! As soon as I posted, Marty already beat me with the same suggestion. Ah well, at least Marty and I think alike...

 

I think you will be very happy with the FCR carb. I have one now and it is completly different than a CV carb. It should do what you have been wanting all along, pop a big wheelie when you nail the throttle. Looking forward to your reaction to it.

 

You are correct. A choke is less critical on a pumper carb because you just twist the thottle to get that extra shot of fuel. With the CVK, you MUST increase vacuum and take away some air to richen it up enough. We have no direct control of the fuel slide and difinitely don't have an accel pump. All our throttle does is open and close the butterfly valve in the carb throat. The diaphram and jets do the rest.

A choke will help a pumper, but is an absolute necessity on the CVK.