| Author | Message | ||
     Buellzilla |
Thanks Aaron, I'm a complete neophyte when it comes to the world of carburetion, jetting, tuning etc.. What is "HSR42", a carb? I do understand how jetting size will vary in proportion to displacement & #of cylinders. How does altitude affect the jetting? Higher altitude equals smaller or larger fuel jets? I would think that thinner air with less oxygen would require smaller size jets, but I'm not sure. | ||
| Xgecko |
I'm not Aaron but I'll answer some of you ?s HSR42 is a Mikuni 42mm carb Jetting does get smaller at high altitude. less air requires less gas | ||
| Aaron |
Yes, Tony is right. But my point about multiple cyls is that, at least where these bikes are concerned, it doesn't change anything, because only one cyl at a time pulls on the carb anyway. That's why the Blast has a 40mm carb, same as an M2 with over twice the displacement. | ||
| Xgecko |
I remember taking to Brian Nallin about jetting changes for the 515cc kit and he said something like starting one size up from where the engine is with present mods. Even with my present set up that puts me below stock jets for a M2 which given the displacement difference makes sense. | ||
| Buellzilla |
Thanks Xgecko/Tony! I understand you Aaron. I was thinking of engines in general, i.e. V8 where more than one cylinder is inhaling at the same time. Maybe this doesn't apply to any motorcycles, most 4 cylinder bikes have multiple carbs don't they? I just got back from my local Buell dealer here in Burlington, VT with the 170 and 45 jets. He, of course, told me that I needed the full Dynojet kit treatment and a new air intake system or I would be blowing valves, drowning the engine in excess fuel, exploding into a human/motorcycle fireball and generally eliminating life on earth as we know it. I'm sorry I haven't been around lately but I don't see any mention of an aftermarket air intake system. The K&N drop-in doesn't seem to do didley judging from the Dyno results posted further back in this topic. If the 2003 model Blasts come with 170 mains and 45 pilots, I should be safe at 320 ft above sea level, you think? I'll check the spark plug anyway. BTW I have the V&H exhaust. Substance abuse aside, there's no place in my home state of Vermont as high as you, Aaron. | ||
| Xgecko |
2002 blast jetting is 42pilot 170 main. Yes I get to 320 above sea level all the time I live at 130 and go up the hills/mountains to 2K often. | ||
| Ezblast |
185 a little rich - heavy burble and sight accel. at letting off of wot. So back to 180, however I'm still thinking about doing the needle upgrade. Waiting for it now. However, when I'm done tweeking the Force intake and put it on - i'll probably go back up to 185 and check it out all over again. Just Blasting on the Dark side! EZ | ||
| Buellzilla |
Thanks again Xgecko I haven't spent any time around dynos and I'm curious. How is the air/fuel mixture measured? Do they drill a hole into the exhaust pipe to insert a sensor or something? Am I going to need to adjust the idle-screw after replacing the jets? Thanks for putting up with all my questions. | ||
| Buellzilla |
Too Bad Dann never got back to us with the details on his accelerator pump from a Sportster floatbowl mod. Anybody else experimented with adding an accelerator pump on the Blast carb? Sounds to me like installing the Dynojet kit and adding an accelerator pump might be the secret to killer carburetion. | ||
| Xgecko |
Yes that pump idea sounded cool. I wich he would post back his results, CV40 carbs with pumps are $20 on Ebay, Anyone here shim their Stock Needle? (0.01" like the twin?) Along with doing the normal jetting changes??? | ||
| Blake |
EZ, First... The M2 comes stock with a 200 or 195 main jet. I don't know about an XL883. They reportedly seem to run best with a 190 or 195 near sea level. I agree, the Blast, even your 515cc big bore, will not require as big a jet as a 1200cc twin. Now here's where I'm getting confused. You say "185 a little rich - heavy burble and sight accel. at letting off of wot." The behavior you describe would indicate a lean condition. You mistakenly diagnosed it as the opposite, a rich condition. I don't know what an "exhaust burble" would indicate wrt carburetion. A pronounced burbling indicates a leaking exhaust manifold gasket. | ||
| Blake |
The A/F meters I've seen simply use 1/4" diameter copper tubing inserted well into the muffler/tailpipe with clear plastic tubing to carry the fumage to the actual sensor. The meter pumps/sucks the fumes with vigor. | ||
| Ezblast |
OK Blake - I'll just have to put it on the dyno and find out - I did'nt notice any improvement in performance though. And the bike is going on a long trip in a couple of months so getting it dialed in is a priority to me. Just - Blasting on the dark side! EZ(what numbers should I be paying close attention to and what level area should I be aiming at?) | ||
| Buellzilla |
thanks Blake for explaining how they measure A/F on the dyno. I just installed the 170 main and 45 pilot jets on my Blast this morning. I was surprised at how easy it was. Castlehead's post at the beginning of this topic had me convinced I was in for a nightmare, but it was real easy. I had no trouble at all with the 4 phillips-head float bowl screws. One word of advice though, is to make sure you have a good assortment of screwdrivers. The pilot jet can be tricky. You need a driver with a shank that is the same width as the blade. I'll have to include a picture to explain it. The pilot is recessed about 5/8" inside the bore. I didn't need to take the carb off. I just loosened that outer band clamp around the hose that connects the carb to the engine and turned the carb counterclockwise to get better access to the bottom end. This, of course after fully removing the airbox. I just got back from a test ride. The deceleration popping is gone and the mid to high range acceleration is noticeably improved, however, it seems to bog a little during low range accelerating. I'm using a stock air filter element and a V&H exhaust. I'll need to ride it a while longer to get a better handle on what has changed. Any thoughts about spark plugs? I'm still running on the factory plug at 5250 miles. Screwdriver 3/16" wide blade:  | ||
| Ezblast |
Blake - you've seemed familiar with the dyno set up I will be using again - what types of numbers should I be looking for in the o2,hc, and co2 levels? Blasting on the dark side! EZ | ||
| Buellzilla |
I've been out for another ride today after changing my carb jets to 170 main and 45 pilot. The bogging down I mentioned is still there until the engine gets hot. This problem pre-existed the jet change, but it wasn't as pronounced. I think it may get worse as the weather gets colder. Has anyone else experienced this? Once the engine is up to full operating temperature, the performance improvement is remarkable. I pulls hard into the rev limiter 48 mph in 2nd and 65mph in 3rd. I haven't tried to hit the limiter in 4th yet, but I'm confident it'll have no problem. Compared to the way it ran when I first got it with the boat anchor and factory jettng, it's fricken amazing. Even after it's warmed up, there still seems to be something slightly amiss with low rpm and low throttle angle performance, maybe a needle change would help? In the 3to4k rpm range with something like 20-30% throttle, the engine seems to run a little rough and if I gently roll on the throttle, it seems to bog down a little. | ||
| Ezblast |
good question Buellzilla - I've noticed a simular problem - will the sporster needle cure this? Anybody know? Just Blasting on the dark side! EZ | ||
| Blake |
EZ, I'd have to relearn Thermodynamics to give you specific guidance on the EGA report. Obviously more O2 (Oxygen from air) means more lean and more HC (Hydrocarbons from unburned fuel) means more rich. I don't know the optimum ratio in EGA results. The dyno operator should be able to tell you how the numbers relate to air/fuel ratio though. If he does, let us know. Interesting stuff. | ||
| Buellzilla |
Some useful links pertaining to tuning the Keihin CV 40 all kinds of carb parts from chopperscycle.com more parts from rageperformance.com http://www.gis.net/~manjo/BUBF_rejetting.htm http://www.nightrider.com/biketech/carbadjust.htm | ||
| Buellzilla |
Some more interesting info on carb design and function http://www.easternillinoisabate.org/tech_talk.htm Another parts source | ||
| Buellzilla |
Here's a must read for beginner tuners like me! http://www.f6rider.com/VRCC/tech/carb101.htm | ||
| Blasted |
Hi. Just a question to throw at everyone. I have a 2000 Blast modified with a Vance&Hines exhaust and a dynojet kit. Mods have been on for a year. It has 15,000 miles on it. Recently, it will hesitate at slower speeds 30-45 mph, like you left your fuel valve closed. However, it stutters until you crack the throttle open, then all the horses let go. This runs in 125 mile increments that almost go away when a new spark plug is installed. Then it progressively gets worse until around 125 miles. The Harley dealer I bought it from says he can't find the problem and has been through the carb and timing and everything. I have heard that it could be the auto enricher malfunctioning. I am ready to take it to another dealer as I am getting nowhere. I have to carry sparkplugs in a bandolier while riding my bike. Any help would be appreciated. Al Metzke | ||
| Buellzilla |
I'm not as expert as others on this board, but I think some extra info will be needed to attempt an online diagnosis. What does your old spark plug look like when you remove it (coloration)? What exactly did the dealer do with the carb? Did he remove it, take it all apart and clean it? If your enrichner is bad then you should have an abnormally high idle speed. When the enrichner is working properly, your idle speed will drop after 2-5 minutes from a cold start, but it could still be leaking a bit. May want to check the fuel tank vent system and vapor valve. Don't ask me how. | ||
| Buellzilla |
Blasted; 2000 service manual, in fuel system troubleshooting lists possible causes for poor acceleration: 1. Throttle cables misaligned 2. Inlet system air leak 3. Restricted fuel tank vent system. 4. Restricted fuel supply passages. 5. Plugged bowl vent or overflow 6. Enrichener valve not seated or leaking. 7. Worn or damaged needle or needle jet. 8. Vacuum piston malfunction 9. Plugged jets or passages 10. Fuel level too low. You ought to be able to remove most of these from the list if you assume that the dealer checked these items when "going through" the carb. He should have properly adjusted the float so #10 is gone. He should have thoroughly cleaned the carb so #9 & #5 are gone. He should have checked the needle so #7 is gone. By his removing and reinstalling of the carb #1 & #2 should be eliminated. The behavior you describe doesn't seem to indicate a shortage of fuel supply from the tank, so #s 3 & 4 don't seem likely. The enrichener valve and TPS are supposed to be removed for cleaning of the carburetor, so the dealer should have inspected the condition of the valve. It should be easy enough to connect the leads to a 12 volt power source and observe the plunger action. Have you tried removing the airbox cover and observing the vacuum slide/piston to see if it opens and closes properly during throttle up and throttle down? The service manual also mentions valve guides and seals as possible causes for plug fouling but I don't know if this commonly comes into play at only 15,000 miles. | ||
| Xgecko |
Good reading thanks (where were you 3 months ago???) and now I probably know enough to be dangerous. Now that I understand more I'm more eager to play with shiming the needle...anyone done this yet??? | ||
| Buellzilla |
I'm sorry I wasn't paying much interest 3 months ago Xgecko. I just discovered the information myself. I think I may need to shim my needle a touch as well. First I'm going to give it a good cleaning and double check my float adjustment. One thing that really caught my interest was the explanation on how airbox size can effect performance. The Blast does seem to have a generously proportioned airbox and perhaps that's why adding a K&N filter element shows no gains on the dyno. This might also be the reason why Force Motor products gave up on developing a Forcewinder for the Blast. They may not have been able to show any real horsepower gains. Why sacrifice all-weather rideability for 0.25 more horsepower? Did you get a gander at those turbulators? I wonder if one of those is compatable with the Blast? | ||
| Blasted |
Hi. Thanks for the reply Buellzilla. The plug is a dark grey, almost black. The dealer said it looked ok. The carb was disassembled, cleaned, and checked. The vent lines were checked. The last mechanic didn't say whether he checked the auto choke or not. It seems to run pretty good at higher speeds (55 and up) even though its hesitating at low speeds. That's my story and I'm sticking to it. Thanks, Al Metzke | ||
| Buellzilla |
You're welcome Al. I'm sorry I can't be more helpful. How is your air filter element? You could try warming the bike up and, somewhere in the middle of a ride, taking the airbox cover off and see what effect that has on the problem. This will lean out your mix, so if you're running too rich in the low and midrange, you should see an improvement, but this won't tell you why. How many miles were on the bike before you installed the Dynojet? How many miles after installing the Dynojet, before things went sour? | ||
| Xgecko |
I was only kidding that was great reading I really feel dangerous now. Where would one find a Shim except for buying a Jetkit I'm scratching my head. At present I'm in a work on the Buell kick because A) I'll be without it for a few months and B) I'm waiting for Bruises on my knees to heal so I can go skateboard Pools with my childhood Skateboard Hero (If you have seen the movie Dogtown: Legend of the Z-boys Jay Adams lives here and I have had the luck to skate a few sessions is some local pools with him...sorta like walking on the moon with Neil Armstrong). I skated with light pads and beyond my abilities hence the bruises. I have switched to my regular pads and a helmet | ||
| Ezblast |
Chill Xgeko - I used to do pools in Palm Springs and Arcadia,also loved the L.A. river. Still thrashing hu - last I did was teach my nephew a few switch kick backs and some 180s, curb stuff. AHHH Cadilac Trucks and Rolls Royce weels and a hand lamented double curved wide board - sweet times(and a few wrist breaks)lol - Thanks for the tip on the primary adj. - Just blasting on the dark side! EZ |
