New CVK40 convert
Posted January 29, 2006 - 03:28 PM
145 Main Jet
N1TB needle (from KLX650) w/clip and spacer (installed at 3rd clip)
Choke plunger (I got the one used on a KX250 part 16016)
Drill out the vacuum hole on the slide to 1/8" (later drilled to 3/16" for much better throttle response)
Remove the return throttle cable since it is not needed
These are the parts I ordered from ronayerscom:
1 16009-1794 NEEDLE-JET,N1TB 1 $15.67 (the order was delayed to get this in stock)
2 16016-1068 PLUNGER, STARTER 1 $21.33
3 223C0416 SCREW-PAN-WS-CROS 4 $1.64ea (new float bowl screws)
4 92037-1401 CLAMP,JET NEEDLE 1 $1.64 (clip for needle)
5 92055-1222 RING-O,FLOAT CHAMBER 1 $8.08 (the carb I got needed one)
6 92063-1017 MAIN JET,#145 1 $6.14
7 92143-1667 COLLAR 1 $2.11 (plastic spacer goes on the needle)
Item Total $61.53
Standard Shipping +$8.00
I also had to get a replacement slide/diaphram from Harley dealer for $50:
slide/diaphragm assembly, part number 27585-88, for Kehin CVK40 carbs.*
And here is a website with more info on the CVK40:
Modify the throttle cable bracket on the carb - cut off the return cable mount, then I'll quote Dave's instructions: "The reason to modify the main cable bracket is to get rid of the extra slack in the main cable ... The area that the cable mounts to the bracket is what needs to be modified ... You have two 10mm adjusting nuts that clamp to each side of the bracket ... The area on the bracket where the bottom adjusting nut clamps ( where the cable leaves the housing ) has to have material removed. There is about a1/2 inch of space in the bracket that the nuts clamp the cable to the bracket. Take a hack saw and remove half of the space about a 1/4 inch from the bottom side of the bracket. This will allow the cable to be raised that 1/4 inch you removed ... and take the extra slack out of the cable. Run the bottom nut right to the end of the threads on the cable and clamp the top nut down ... do your final adjustment on the cable at the throttle housing"
Installing the carb was a bear for me. It was a tight fit, and the carb is slightly larger where the boots attach. I had a really hard time getting the airbox boot on, even with the rear subframe pivoted away to get the carb in. The front boot clamp needed a longer screw, and the rear clamp was flipped over to allow access to the clamping screw. I don't want to ever have to pull the carb again :-)
The bike fired up immediately with the choke, and once warm idled very high. The easy way to access the idle screw is from behind the coolant reservoir, with a long flat blade screwdriver. It adjusted easily down to a smooth idle. Dave tells me he took the flexible idle adjuster from the stock carb, and used it with the CVK.
I just got back from a 2 hour ride. The bike runs great! The re-jetted stock carb would lift the front wheel slightly on a drop throttle roll on in 1st, but this time it came up quite a bit, and surprised me! Bike runs great everywhere especially mid to upper rpms. It pulls well in 5th thru 90mph then tapers off. It was very windy today, and in one section I could hit 100mph (could only do about 96mph with modified stock carb) with the wind coming at an angle behind me. Pulling the clutch and chopping the throttle from a high rpm run, the engine drops to idle immediately.
Edited today, since I drilled the vacuum hole in the slide to 3/16" per Dave's suggestions. Much better throttle response. I've added "E" cams too, and am very happy with this setup.
Overall I'm a happy camper :-)
Thanks again Dave!!!!!
Posted January 29, 2006 - 04:08 PM
Posted January 29, 2006 - 04:10 PM
Posted January 29, 2006 - 05:15 PM
anythere else i could read about this? your mid list is about exactly what im planning. stock exh. with end cap drilled or billet fleabay cap, 3x3 and damn near sea level. this has got me thinking more of focusing on this and saving the money twords a jet kit and investing it in this. need to read more.
If I had to do it over again, I'd of gone this route first, rather than spending the money on the SM specific jet kit. The FCR is reportedly the true way to go, I just can't afford one...yet.
Hopefully Dave will jump in here to offer his experience with the CVK.
Posted January 29, 2006 - 05:32 PM
P.S. the above is my bias opinion as I have a CVK40 on my S.
Posted January 29, 2006 - 06:04 PM
it's the headpipe that is the real restriction on the drz.
So do people ever swap out just the head pipe and continue using the stock muffler?
Posted January 29, 2006 - 07:07 PM
I checked the carb site on ebay but didn't see any. Possibly under KLR/KLX???
Does it have an acc pump??
Posted January 29, 2006 - 07:13 PM
Keihin IIRC, bike is in storage at the moment.
OK stupid question. Who makes the CVK40?
Could be I have never tried this mod, I do know that on my tengai (klr 650 based bike) it is more responsive than the carb on the S
A lot better?
YES, I would think so, it couldn't be better then a pumper for responsivness.
somewhere in between the stock carb and the FCR?
Posted January 29, 2006 - 07:28 PM
Is there a web site that would explain the differences between carb types?
Posted January 29, 2006 - 07:48 PM
Understand FCR flows better then CVK 40.
Do you think that 4 cfm difference ( if that is actually what it is) between BSR 36 CV and CVK 40 is a decent change. Low buck fix - possibly around $200 - has advantage of CV for elevation changes, fairly easy change. Equal possibly to 3x3???? Might be better then the stock 36 if a guy could swing a couple hundred $ or less now then move up later.
Or not worth the effort???
Thanks - LBM
Posted January 29, 2006 - 07:54 PM
the cvk conversion is cheaper.
any one that plans to do a cvk local to please contact me for free dyno tuning.
on side note,its MM not CFM.
Posted January 29, 2006 - 07:59 PM
Thanks - I hope someone takes you up on the carb tune so we can have a good base line for jetting.
Posted January 29, 2006 - 08:44 PM
The merit of the CVK40 carb is that for less than $200 you get a real power increase to your bike that you can feel by the seat of your pants. FCR may produce more power and better throttle response, but it costs about 2 to 3 times more. The CVK40 is certainly a better investment than a slip-on exhaust for those with stock S and SM seeking cheap power.
P.S. the above is my bias opinion as I have a CVK40 on my S.
Looks like 2 have done it so far - question is what bikes does the CVK 40 come on - KLR/KLX - any others??? Suzuki DR 650???? Any Honda's????
Thanks - LBM
Posted January 29, 2006 - 10:17 PM
Posted January 29, 2006 - 10:33 PM
freewheelers : I've now done over 12 40mm CVK Keihin conversions on DRZ400/475 locally ... I don't have a dyno to work with ... However I have alot of DRZ's locally to compare against ... "S" and "E" ... From my experiences ... In drag racing down the road ... and cutting laps in the woods ... The 40mm CVK appears to have the same power as the FCR on the "E" ... With the vacuum port enlarged ... it also seems to have equal throttle response ... I'm sure the FCR will show an advantage on the dyno ... However ... in the real world ... I really have not seen an advantage in the FCR ... I don't want to start a family feud ... It's just one mans observation ... based on alot of real word comparisons both on the street, track, and trail.
Thanks - it's sounding like more and more of an option. Were these new carbs direct from Keihin or take offs from a wrecking yard - or?? Still trying to find out what they come on other then KLR/KLX. So I can keep an eye out for a low cost buy. Any idea on jetting for 3000-8000' elevation?????
Appreciate the input - if anyone in Colorado does the mod and gets it to Burned it will be interesting to see what the dyno says but so far it looks like your seat dyno says it's looking good.
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