| Author | Message | ||
     Ratbuell |
Took the ol' "2" out for a ride today. Last couple times I've ridden...it's felt "flat" at higher RPMs. Today, it went into full-blown cut-out. 5k rpm and it was like the ignition was hitting the rev limiter...but it's not. The bike: 95 S2 with Thunderstorm top end, X1 cams, S1W race ignition (I want to say 6800 rev limit but not sure; it's a Buell box), stock coil, stock pickup. Jets are 45/190, 2.5 turns out. Stock filter. Good intake seals. Good system voltage all the time (I have a Kuryakyn voltmeter on all my bikes, and it doesn't drop volts at all). I just pulled the Supertrapp off and put on a Kerker "System K" pipe. Looking at it, it should flow a little better than the 'trapp, so I upped from the 'trapp's 180 main to the 190 in it now. Good low/mid power. Even decent running at 5k+...until I go from 3/4 throttle to WOT. Then, it starts that cutout thing. I can keep it in cutout and pull the choke all the way out, no change. Plug wires are tight. Connections are tight. I haven't dug into the bike yet because it's still hot from riding, but I will. Things I'm thinking: 1. VOES could be wonky, but could it cause this? 2. Jetted too rich? It does NOT ping so I'm guessing its not too lean... 3. Coil could be going out? If I'm getting weak spark that could explain the flatness...but not the cutout change from 3/4 to full throttle. I'm stumped. Been so long since I made a change to a carb bike, I forgot how to troubleshoot! LOL Once it cools, I'll pull the tank and poke around a little bit. | ||
| Sanders |
190 seems a little big to me but I'm by no means an expert. I have a thunderheader on my S3 which is essentially an open header and I run a 165 main jet in my Mikuni. Runs smooth and took first place at a recent dyno shootout. 86hp, 85 pdft of torque. Probably not the VOES. If it was you would probably have the problem throughout the rev range. Same goes for the coil. I would bet your jetting if off... | ||
| Phelan |
The jet sizes are not similar across different carbs. I had a CV on my '03 XL1200S and it came from the factory with a 190 msin jet (mind you, this is motor is dual plugged with lightning heads and a map sensor instead of a VOES switch), so I don't think the carb jetting is the problem. | ||
| Ratbuell |
I run 48/190/2.5 in my S1W with a full Buell race exhaust, and it freakin' SCREAMS. Basically the same engine, but with the lighter flywheel. I seriously doubt there's THAT much difference between the race exhaust and the Kerker (or the 'trapp, for that matter). Bike ran great with the 180 and the 'trapp. I may just go back to that for a baseline, and see what I get. Gotta troubleshoot a Jeep a/c system first though. (over)full charge of R134 but the compressor won't kick on, and my Haynes book doesn't have a clutch troubleshooter...grrrr..... | ||
| Kilroy |
I had the same symptoms. My main jet was clogged with crap and was about 75% blocked. | ||
| Xl1200r |
I'd say it sounds jetting-related, but not jet-size related (a la kilroy). You don't hit that main jet util you start to open it up, and it takes a LOT of extra fuel to get a miss from a rich condition. 190 main is big, but not too big I don't think. If it were ignition, you'd get it all the time, regardless of RPM, generally. I'd put the 180 back in and see how it does or see if the 190 is mucked up. | ||
| Ratbuell |
It was just as flat with the 180, which is why I stepped up to the 190 thinking it might help. I do clean both my emulsion tube and all my jets before I install, and clean the jets before I stow them in my little tacklebox thingy, so I don't *think* it's a dirty jet, but I could have gotten some crappy gas or something. I'll go back to the 'trapp and the 180 and see what that gets me. I need to drill and tap for my new buttonhead cap screws to hold the bowl on anyway, I'm sick of farting (was going to use another word that starts with the same letter) around with those "I strip if you look at me crosseyed" phillips screws... | ||
| Bigslug |
How old are your plug wires? My M2 did the exact same thing a couple of years ago, and I was sure it was carb related. After removing the carb, cleaning and rejetting a few times it still had the miss. Finally I threw an old set of wires on I had laying around and no more miss! Bought a new set of wires and no problem since. Might be worth swapping wires with one of your other bikes and see if it goes away. Mike | ||
| Sportyeric |
Is fuel getting out of the gas tank OK? As a long shot, could the float bowl vent be plugged? (I had a spider nest in mine that stopped air from getting out of the float bowl, hence stopped fuel getting in. That was after leaving the carb hanging from the bike for five years, though.) | ||
| Bluzm2 |
Check the relays behind the battery. Had the exact same thing on my S2. I replaced all the relays and problems went away. It's a vibration thing. Runs fine a low RPM's falls on it's head mid to high. I replaced all the relays since the were all original. I got the replacements at NAPA. Brad | ||
| Buellistic |
Nobody has said spark plugs yet ??? Nobody has mentioned the diaphragm on the slide yet ??? Nobody has said drop the float bowl and check the high speed jet hole("i" run a 200 High speed jet in my 1997 S3T) ??? | ||
| Ratbuell |
Slide diaphragm is good, checked it today. Plug wires test good, no signs of arcing. Jets are totally clean. Fuel is flowing. I can cruise-throttle at 5k and it does fine. Whack it WOT, though, and the break-up starts immediately. Roll to WOT, and it still breaks up once I hit like 90% throttle. Found one problem, though. Bottom needle came out of the carb; top needle is the OEM out of my jets box. I swapped them...it's a little bit better, but still not right.  That, and the fact that I can see odd wear on the slide itself, makes me think the carb *body* might be warping or going bad? What're the chances of that? Weirdness continues...anybody got a decent used CV carb / carb body?  | ||
| Jim2 |
Looks like the bottom adjustable needle has a lot of shim on it over the stock. Maybe you need to shim the stock one you just put back in a bit. | ||
| Ratbuell |
I'm not so worried about the shim height, as I am about what happened to the "needle" end... | ||
| Ratbuell |
So dumb question of the hour...CV40 is stock, right? |
