| Author | Message | ||
     Dave_02_1200 |
When I replaced my Mikuni HSR 42 and the Race Pipe with the stock, but rejetted, CV 40 and stock exhaust the bike ran pretty well. Yesterday I did the one thing that I had read about but not done: I drilled the vacuum port in the slide to 1/8". Now it responds instantly like the Mikuni and delivers the power smoothly all the way from idle to red line. It even cruises in the midrange without misbehavior of any kind. If you have a CV 40 on your bike, I highly recommend this simple but very effective "product improvement" (a tip of the hat to Buellistic) | ||
| Psyclown |
Can you forward me that "INFO"? | ||
| Dave_02_1200 |
It is really simple. There are two holes on the bottom of the slide: The center hole is the one where the needle comes out. Don't drill that one. The other hole is the vacuum port. Drill this one. The stock vacuum port is too small and the resulting restriction damps the slide movement when you open or close the throttle causing slow throttle response. Drill the vacuum port out to 1/8" diameter, blow off any shavings, and reassemble. That simple change will give much quicker and more controllable throttle response. | ||
| Psyclown |
Just found this instructional link ---> http://www.google.com/imgres?imgurl=http://www.yos tperformance.com/faq/images/cv40figure.gif&imgrefu rl=http://www.yostperformance.com/faq/cv40.php&usg =__s7t-G_csITfADMv3O-RsjHGijV8=&h=794&w=600&sz=84& hl=en&start=1&sig2=pXqW0x3NFBxjgGjG7WDd8Q&zoom=1&t bnid=RbRr0KnHoMMmYM:&tbnh=143&tbnw=108&ei=9m1STvaH HNHE0AG40OSPBw&prev=/search%3Fq%3Dcv%2B40%2Bcarb%2 6um%3D1%26hl%3Den%26sa%3DN%26rls%3Dcom.microsoft:e n-us%26tbm%3Disch&um=1&itbs=1 I'm gonna try this. Thanks for the info. | ||
| Buellistic |
Psyclown: You have E-mail !!! | ||
| Littlebuggles |
Can this be done with cables still connected or is it better to remove the carb completely? My Cyclone starts and responds better than my XB throughout the entire rpm range, but is a bit choppy under steady throttle around 3000 rpm. | ||
| Fahren |
Psyclown, those Yost instructions have you drilling out both holes to 1/8" (needle hole and vacuum port). Also, I looked at a Yost tube and an intake splitter for my Blast, when I still had it. Are these worth considering for the CV on an S1W? (Message edited by fahren on August 22, 2011) | ||
| Fast1075 |
Drilling the slide was one of the first mods I did to my Blast! (they also use the CV40 carb)...what a difference that made!!! | ||
| Dave_02_1200 |
The cables can be left on the carb but you will have to loosen the cable mounting plate from the carb body to get the top off so the slide can come out. Also, do not drill the center hole! The Yost instructions are for their needles, which must be larger. I did not drill the center hole and I am using a stock needle with about .066" in shims (3 x .022" from Radio Shack) | ||
| Psyclown |
How do you figure out what size needle shim you need? | ||
| Jayvee |
Niggling difference, but some sites say 7/64ths is the size to use. You didn't happen to try that one first? Can always go bigger, but can't drill it smaller, is what I mean. | ||
| Buell_bert |
Buellistic what are your thoughts on this and what about others that have done this. Performance, mileage etc. ???. Hate to just start drilling holes with out good positive info to back it up. | ||
| Buellistic |
Depends how fast you want the slide to pop up ... 7/64's is 1/64 over 1/8th and "i" guess the -99 slide spring would make it pop up even sooner, "BUT" you have to be careful or you will mess up drive ability !!! (Message edited by buellistic on August 22, 2011) | ||
| Buell_bert |
Buellistic I meant drilling it at all not the 1/8 or 7/64 difference. Also listening for other peoples opinions. Thanks. | ||
| Jdodd |
Did basically the same thing to the slides on my kawasaki zzr1200 when I installed an Ivan's jet kit. Big improvement in throttle response. like jayvee says, drill the first oversize, you can always make it bigger later if you feel the need. | ||
| Dave_02_1200 |
"Depends how fast you want the slide to pop up." That's it exactly. My stock CV 40 seemed a bit sluggish and it responded too slowly for my liking. Now it responds without any lag and it seems more connected to the throttle - like my HSR 42 Mikuni did. | ||
| Buellistic |
You must remember the QUICKER the slide goes up the QUICKER the gas mileage goes away !!! | ||
| Dave_02_1200 |
I hadn't considered the possible effect on gas mileage. Looks like I'll have to keep track for a while. | ||
| Buell_bert |
I believe I will ponder on this for a while as I get good enough response presently. It is also very easy to lift the front tire if needed. I would hate to change my mileage to much. I don't worry to much but last I checked it was 40-45 which is fine. | ||
| Natexlh1000 |
I think they made it the way they did from the factory is to try to damp out oscillations caused by two big lungs inhaling at irregular intervals. Imagine if the hole was too big. I bet the slider would flop around at low RPM cruising speed. Don't go TOO crazy drilling holes in there  | ||
| Jim2 |
I did this mod and I'm getting about 38mpg in the city and 48mpg on the highway. Can't say for sure what I was getting before but it was better. I am still glad I did the mod. | ||
| Psyclown |
"How do you figure out what size needle shim you need?" Can anyone give me some incite on this? | ||
| Buellistic |
Psyclown: "i" tune with a FUEL/AIR GAUGE in the real world riding down the road ... The gauge indicated 0.050(depends on how your engine is set up,ie: timing,cams,sparkplugs& gap,valve size's,how your intake flows,sxhaust ports flow,exhaust system(header/muffler), and air cleaner)of an inch worked best for the fuel/air ratio that "i" wanted to tune for which was 12 to 1 fuel air ratio ... There are those that say that is TOOO RICH, "BUT" my engine will run a little cooler to ... (Message edited by buellistic on August 24, 2011) | ||
| Hootowl |
"7/64's is 1/64 over 1/8th" You mean under? | ||
| Someday |
If you want real perfection install a Yost Power Tube! Got this info from the late "Battle 2-Win" magazine. I've had one in my tuber for over 10 years and it was the single best improvement I ever made. Here's a link with some good reading too: http://www.yostperformance.com/ | ||
| Buellistic |
Hootowl: You are correct, "BUT" it is not possible to correct my post: Monday, August 22,2011 - 09:36 pm "THANKS" for seeing my mistake so "i" could "CMA" !!! | ||
| Fahren |
Someday, I had asked about the Yost and also about an intake splitter in a post above. Both of these are good mod's for a Blast, as discussed by EZ in the Thumper section; don't know if both would be good also with a CV/Tuber combo. | ||
| Someday |
Sorry, I missed that. Again I'll say the Yost Power Tube is money well spent. The carburation on my '98 S3T is as good as my '08 Uly with the Erik Buell Racing ECM. | ||
| Fahren |
Here is a link to the splitter I was talking about. Some on thumper board have fabricated their own, too, instead of buying for $120. http://www.scaryfastracing.net/harley.htm | ||
| Buellistic |
IMHO is better to re-work the INTAKE MANIFOLD or buy a BETTER FLOWING INTAKE MANIFOLD than STICK an OBJECT in the INTAKE TRACK ... Any BUELLer do a DYNO RUN on a before and after on this INTAKE CHOCKER ??? |
