A dangerous *poof* on a carb' 88"
A dangerous *poof* on a carb' 88"
MY bike will randomly "poof" and hesitate, it nearly seems like a backfire through the carb but it doesn't "POP" The first few times it happened I figured it was because the bike wasn't warmed up, it would "poof" only when I twisted the throttle. Or so I thought, but the more I ride the more random it seems. Well today it happened at a very inopportune moment, here is the story (short version):
I was going for a leisurely ride, in the foothills of Sonoma county, I decided to step it up a notch and take on a road I have driven many times, in fact my parents live up it. Anyways it is a few miles of climbs, a few hills and twists pretty good here and there. The moral of the story is this: As the bike and I leaned left and followed the road, I was half way though the uphill 120 degree corner when I gently rolled the throttle and "Poof!" a split second of lost power during exactly the wrong time. Luckily it was only momentary and the power regained quickly enough to where all I had to was straighten my spine a little, and change my shorts.
The symptom is random, sometimes when I first roll the throttle other times my wrist wont rotate, the engine speed will be between 2k-2,800 rpm (happened again on a straight, flat road while heading home from the curvy cruise, apprx. 50mph)
The bike is a 2002 dyna low rider cv carb'd 88" factory everything, newer air filter, currently has 7,900miles, serviced at 7,781miles less than 2 months ago, which included new plugs, fresh fluids and oil filter, also "cleaned out carb and plugged slow jet, flushed out fuel" -Harley dealership, they also did what they call an "open 0603 carb needle jet recall"
So do any of you guys have actual experience in the matter and some advice that will help me out?
I would really appreciate it!
I was going for a leisurely ride, in the foothills of Sonoma county, I decided to step it up a notch and take on a road I have driven many times, in fact my parents live up it. Anyways it is a few miles of climbs, a few hills and twists pretty good here and there. The moral of the story is this: As the bike and I leaned left and followed the road, I was half way though the uphill 120 degree corner when I gently rolled the throttle and "Poof!" a split second of lost power during exactly the wrong time. Luckily it was only momentary and the power regained quickly enough to where all I had to was straighten my spine a little, and change my shorts.
The symptom is random, sometimes when I first roll the throttle other times my wrist wont rotate, the engine speed will be between 2k-2,800 rpm (happened again on a straight, flat road while heading home from the curvy cruise, apprx. 50mph)
The bike is a 2002 dyna low rider cv carb'd 88" factory everything, newer air filter, currently has 7,900miles, serviced at 7,781miles less than 2 months ago, which included new plugs, fresh fluids and oil filter, also "cleaned out carb and plugged slow jet, flushed out fuel" -Harley dealership, they also did what they call an "open 0603 carb needle jet recall"
So do any of you guys have actual experience in the matter and some advice that will help me out?
I would really appreciate it!
Stock is pretty lean, they are known for that carb fart. You can adjust idle AFR pretty easily, a quick google will show you the way.
I don't really care for the CV carb throttle response, I'd say get a Mikuni HSR42
I don't really care for the CV carb throttle response, I'd say get a Mikuni HSR42
Outstanding HDF Member
Joined: Nov 2010
Posts: 2,250
Likes: 36
From: Montana
your carb is running lean. either get a jet kit for it. (easy to do ) or buy a mikuni HSR 42 or an S&S Super E. I think the mikuni has better throttle response. A little harder to tune but once dialed in they run like stink.
Road Warrior
Joined: May 2005
Posts: 1,301
Likes: 24
From: Minden LA
Yea, raise the needle. pull the slide and put a washer under the stock needle. Don't do the sportster needle. At 96k I had piston slap and when I pulled em the Teflon coating was gone on the skirts, too lean. I went up a jet size (and a little bit) when I put in the 95s and all of the carb farts were gone except on cold mornings and not fully warmed up. When she's fully warmed up I can make any throttle movement I want and no farts. Of course with 9.5/1 and 211 cams it runs a bunch better too--still can get 48mpg, being nice, 37 at 80mph, 34 tooth front sprocket---cheers
Outstanding HDF Member
Joined: Dec 2012
Posts: 2,557
Likes: 235
From: Texas
Yea, raise the needle. pull the slide and put a washer under the stock needle. Don't do the sportster needle. At 96k I had piston slap and when I pulled em the Teflon coating was gone on the skirts, too lean. I went up a jet size (and a little bit) when I put in the 95s and all of the carb farts were gone except on cold mornings and not fully warmed up. When she's fully warmed up I can make any throttle movement I want and no farts. Of course with 9.5/1 and 211 cams it runs a bunch better too--still can get 48mpg, being nice, 37 at 80mph, 34 tooth front sprocket---cheers
Last edited by skinman13; Oct 16, 2014 at 07:54 PM.
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Outstanding HDF Member
Joined: Oct 2013
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Likes: 700
From: St. Clair Co., MO
CV40's are EASY. Clean it thoroughly, replace the diaphragm if necessary. Start with a 45 pilot jet & the stock main (190? 195?) & yes, the '88 XL needle. Pop the cover over the idle mixture screw, gently run it all the way in, then back it out 2 1/2 turns. You'll be very close to ideal at that point. I ended up with a 46 pilot & 2 turns out on the mixture screw. That's with a Ness Big Sucker a/c & Cycle Shack slip ons. No sneeze/fart thru the carb, warms up quick & good throttle response.
Don't drill the slide, don't put a lighter spring in it & don't waste your money on tuning kits. You'll get better results for less money using less expensive OEM parts. Takes an hour, drinking a beer & taking my time.
I know why some don't like the XL needle. I've have great luck using it in 3 different bikes. All 3 ran great & got/get great mileage.
Don't drill the slide, don't put a lighter spring in it & don't waste your money on tuning kits. You'll get better results for less money using less expensive OEM parts. Takes an hour, drinking a beer & taking my time.
I know why some don't like the XL needle. I've have great luck using it in 3 different bikes. All 3 ran great & got/get great mileage.
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