| Author | Message | ||
     Jim2 |
Today I finished my CV40 mods that many here have endorsed. I installed a 45 slow jet. I drilled the idle plug and set it 2.5 turns out. Shimmed the needle .050", drilled the slide venturi hole 7/64", radius'ed the slide. Runs like a top. Starts easy with less choke and doesn't require 5 minutes of run to put the choke back in. No more popping at cruise and not popping on decel. Smoother and more power. I will see what happens to my gas mileage in time. Right now I couldn't be happier. Thanks to all of the Badwebbers that provided this information and thanks to Buellistic for pictures of the radiused slide. (Message edited by jim2 on November 29, 2009) (Message edited by jim2 on November 29, 2009) | ||
| Snp304 |
what is radius'ed the slide? Not sure I know what you are talking about there... | ||
| Daveswan |
NICE! | ||
| Bluzm2 |
Snp, I was wondering the same thing.. | ||
| Richsm2 |
just found it here: under slide mods http://nightrider.com/biketech/hdcvcarb1.htm | ||
| Richsm2 |
some parts http://www.johnsmotorcycleparts.com/catalog/ | ||
| Jim2 |
That's a good write-up of what I did. I took a Badwebers advice and used a 7/64" bit instead of 1/8". He cautioned that going too big may result in hurting the gas mileage. Also that writeup suggest a 1/8" washer. That may work for a stock Sportster needle but the 2000 M2 came with a different needle (so I'm told). It is advised to shim it .050" which is almost 1/16" of an inch, but less still. I used two #4 brass washers and borrowed a micrometer off the shelf. I would guess that 1/8" would make your low to mid transition way too rich. I doubt I'll ever get it on the dyno but my butt tells me it's a lot better. A friend of mine rode it before and after and says "it's like a whole new bike, way better than before". thanks again Badweber's. (Message edited by jim2 on November 29, 2009) | ||
| Buellistic |
The M2 NEEDLE PN 27241-95(NOKK) is the "BEST" needle ... Running this needle in my 1997 S3T and 2000 BLAST ... Also took off the "ACCELERATOR PUMP" as you do not need it !!! (Message edited by buellistic on November 29, 2009) | ||
| Dave_02_1200 |
Lafayette, Do you know how the PN 27341-95 needle compares with the PN 27241-95 needle listed in my 2002 Parts Manual? Is there a difference? Or is it just an updated number? Thanks, Dave | ||
| Buellistic |
Dave_02_1200: THANKS for PROOF READING for me !!! The correct part number is PN 27241-95 as in your M2 PARTS BOOK ... | ||
| Daveswan |
Drilling the slide makes it rise quicker when you hit the throttle, contributing to quicker response. I've read 2 things with regards to drilling the slide 7/64" versus 1/8" - it's just a hair smaller anyways. Drilling it too large (larger than 1/8") may make the engine surge while cruising, plus it may also create a flat spot. If the slide rises too quickly - since it's controlled by vacuum and not the actually linkage - it can contribute to the lean condition you're trying to get rid of. When I was going to drill it, I planned on 1/8" but noticed I had 7/64" so that's what I used as a safety cushion after all. I tend to err on the side of caution given the option. | ||
| Jim2 |
Only got 28.5 miles per gallon. That's pretty crappy. I did not fine tune the adjustment on my idle after setting it 2.5 turns out. I guess I'd better. Maybe I need to drop the shim to .025"? I think it is rich on the low-mid throttle section. I still have the complete stock airbox setup and muffler. I believe I was getting between 38 and 48 before. | ||
| Jim2 |
Just realized my mileage values may not be accurate. I had the battery disconnected. Doesn't that reset the trip meter? Maybe I really had more miles on. Can't remember when I filled up before this time so I'll just have to wait and get an updated mileage value. I hate waiting. | ||
| Richsm2 |
fill it up again,or 2,and check. | ||
| Buellistic |
You can not have he best of both worlds at once ... It you tune it to run, then gas mileages will decrease proportional to the amount of throttle you twist !!! | ||
| Jim2 |
Don't get me wrong; I wouldn't go back for the world. I still did not fine-tune the idle setting or re-check the timing. I thought I read a recent post that inquired about what gas mileage we've all been getting. I thought that most were getting in the high thirties and low forties even with these mods. My riding is mostly city, stop-light to stop-light and that might explain it. I'm definably ON the throttle. I'm sure I'll calm down in time. | ||
| Psyclown |
Any idea why that article insists on replacing the needle when doing the mods? What is the expected life a needle? | ||
| Snp304 |
that site is the site that I used to modify my carb, but I used the CV Carburetor Modifications For EVO and Twin Cam engines page. It does not talk about the radius'd slide on that page (http://www.nightrider.com/biketech/hd_cv_mods.htm) | ||
| Jayvee |
Almost every 'article' on tuning this carb says to replace the needle with the N65C (pre-accelerator pump Sportster needle.) | ||
| Buellistic |
It was found that the M2 needle NOKK preformed better on the DYNO than the N65C, "BUT" it did not say if the accelerator pump had been removed ... "i" have my accelerator pump removed because it makes the jetting act too rich when re-jetting the CARB. ... "AND" "i" tune my CARB. with a FUEL/AIR GAUGE in the real world(IMHO, the DYNO is not close enough !!!) to 13 to 1 fuel air ratio(it is not too rich) ... | ||
| Richsm2 |
Buellistic,what did you do to blockoff the pump? I want to save some gas from my twitching right hand. | ||
| Buellistic |
Richsm2: Removed the ROD and plugged the hole ... Removed the spray jet and plugged with JB WELD(pictues if you want them, just e-mail me) ... | ||
| Richsm2 |
thanks for the info. | ||
| Daveswan |
It's going to be 6 and 1/2 dozen. If you block the pump you'll have to increase the size of the slow speed jet (45 to a 48) to compensate for the new lean condition you'll be introducing to the slow speed circuit. Unless you're puffing black smoke or bogging, it's not getting too much fuel. Each circuit has an effect on the other in order to create a smooth transition from idle to full throttle. They all sort-of overlap, where one circuit tapers off the next one takes over.  graph doesn't show he effect of the pump but it's right off idle. I'm used to working on Holley carbs and adding 50cc pumps and controlling the effective shot of fuel with a combination of cams and nozzle diameter to compensate for the off idle stumble due to the lack of a slow speed jet circuit that could be adjusted like that. Plus with car engines and hotter cams, they don't draw the same vacuum so you need a mechanical shot of fuel. When I first got my M2 I was looking to add a larger pump! Then I found out about the slow speed jet setup. So essentially I think you'll be trading one for another and nothing is going to really be a gas saving move. To do that you'd have to put the old exhaust back, plug up the intake, go back to a 42 slow speed jet.  | ||
| Richsm2 |
the a/f ratio will be more constant than the fuel enriched stream from the pump.many -most old school carbs were without pumps.mine squirts (raw gas)at any slight movement of the impatent wrist.the placement of the fuel height in the bowl will be of importance to transition between the secondary and main fuel systems. | ||
| Daveswan |
that's true... closer to fuel injection precision in a way. The least amount of fuel that's absolutely needed while maintaining a constant air fuel ratio between the transitions of each circuit. I was adjusting my throttle cable over the weekend. Each time I turned the throttle a little shot of fuel got injected. They do add up over a period... but to radically alter MPG...? Whatever I'm getting is much better than my Jeep so I've actually been happy -- More fun to drive too! |
