Fuel spray back into air filter
Outstanding HDF Member
Joined: May 2007
Posts: 2,304
Likes: 31
From: Florida
RE: Fuel spray back into air filter
ORIGINAL: 2daking
I have a problem with my Mikuni HSR42 spraying fuel back out into the air filter when the throttle is cracked and during acceleration. Any thought on how toi correct?
You did not explain your set up so I'll tell you about mine with the same problem andthe fix. This was on a1997 FLHR Road King (EVO) with a Mikuni HSR 42, Andrews EV-46 cam, Jim’s lifters, etc...PlusPorker slip-on pipes NOT BAFFLED. When riding hard and alwayswhen the air got thinner (high altitudes) I would get gas spray-back into the air filter. This would eventually soak the filter and the filter oil which then would get the right sidecover & saddlebag buggered. This was not anoil blow-by/crankcase breather system problem.
The fix: I baffled the pipes and did a re-tune on the Mikuni. Note: minor adjustment on the main jetting only: Jet Needle, Pilot Jetand Accelerator pump nozzles are stnd.;Main Jet:162.5 The problem went away. I also talked to the Mikuni Rep at a bike show and he confirmed the problem/solution.
I hope this helps but thereare so many "problems"/set-ups so to find your solutiontakes troubleshooting, trial-errorand doing your homework - like reading this forum.Hey, thanks to the folks that started this one!
- Jim
[8D]
I have a problem with my Mikuni HSR42 spraying fuel back out into the air filter when the throttle is cracked and during acceleration. Any thought on how toi correct?
You did not explain your set up so I'll tell you about mine with the same problem andthe fix. This was on a1997 FLHR Road King (EVO) with a Mikuni HSR 42, Andrews EV-46 cam, Jim’s lifters, etc...PlusPorker slip-on pipes NOT BAFFLED. When riding hard and alwayswhen the air got thinner (high altitudes) I would get gas spray-back into the air filter. This would eventually soak the filter and the filter oil which then would get the right sidecover & saddlebag buggered. This was not anoil blow-by/crankcase breather system problem.
The fix: I baffled the pipes and did a re-tune on the Mikuni. Note: minor adjustment on the main jetting only: Jet Needle, Pilot Jetand Accelerator pump nozzles are stnd.;Main Jet:162.5 The problem went away. I also talked to the Mikuni Rep at a bike show and he confirmed the problem/solution.
I hope this helps but thereare so many "problems"/set-ups so to find your solutiontakes troubleshooting, trial-errorand doing your homework - like reading this forum.Hey, thanks to the folks that started this one!
- Jim
[8D]
When you baffled the pipes you stoppedSOME of the reversion through the carb during valve overlap, when you leaned out the carb less fuel was picked up by the pules wave which inturn gave you less STAND OFF, but believe me you didn't stop the pulse waves of an internal combustiuon motor by your fix....you only cut down the reversion frombad pipes and gave it less fuel. If you rode with out an air filter or did a couple of WOT runs on a dyno with outthe air filter you would see, smell, and feelthe plume of gas hovering out side the carb.....every internal combustion does this to a point....Harley just does it best....lol
6th Gear
Joined: Oct 2008
Posts: 13
Likes: 0
spray back
I also had the fuel spray back into the air fliter and I had a one foot flame shooting next to my leg.this is on an 08 screamin eagle soft tail springer.I took the bike to the dealer in trenton n.j. and they told me that their was nothing wrong and they told me that this was caused by the rider, can you imagin that rider error.I took the bike to east coast choppers and had the bike dinoed. it showed only 77 hp so they installed a power comander and and changed the pipes and came up with 113.32 hp and the bike runs great and no thanks to harley davidson.
Cruiser
Joined: May 2008
Posts: 117
Likes: 3
From: Milwaukie Oregon
I saw this on another forum but it is a good visual of what this thread is about
http://www.youtube.com/watch?v=m27xXVgg1nc
http://www.youtube.com/watch?v=tisZdCw7vd4
http://www.youtube.com/watch?v=m27xXVgg1nc
http://www.youtube.com/watch?v=tisZdCw7vd4
Last edited by cts1950; Mar 12, 2009 at 03:42 PM.
6th Gear
Joined: Oct 2008
Posts: 13
Likes: 0
ya i had the same problem with my 08 screamin eagle softtail with 110 cubic inch motor but a one foot flame would shoot out the air filter. and harley davidson said that their is nothing wrong. {trenton world *** harley in n.j. I had taken the bike to east coast choppers in tuckerton n.j. the man ray but my bike on a dyno test it showed only 77 hps. so ray installed a power commander2 and messed with the timming and a new set of pipes and came out with 113 hps. no more harley s lame excuse because they could not fix a bicycle
Stage IV
Joined: Aug 2008
Posts: 4
Likes: 0
another fix that i have heard about is to run sunoco premium fuel through the engine for a few hundred miles. what happens is that the valves will build up with carbon and not seat properly which also causes a compression loss. with the calves not seating all the way you will have a spray back of fuel everytime the piston is on a compression or exhaust stroke. because the piston is going up in the cylinder some compression will be lost and air will be pushed out of the intake valve and back out of the carburetor thus soaking the air filter with gas. i hope this helps
Road Warrior
Joined: Aug 2008
Posts: 1,306
Likes: 865
From: Sheboygan, WI
I saw this on another forum but it is a good visual of what this thread is about
http://www.youtube.com/watch?v=m27xXVgg1nc
http://www.youtube.com/watch?v=tisZdCw7vd4
http://www.youtube.com/watch?v=m27xXVgg1nc
http://www.youtube.com/watch?v=tisZdCw7vd4
Last edited by d_slat; May 22, 2009 at 11:03 AM.
Stage III
Joined: May 2009
Posts: 3
Likes: 0
just bought an o2 xl1200c has k&n air filter screaming eagle 2 pipes and i think stock carb. The problem is that during acceleration while riding and sitting in neutral the carb is spitting alot and bike tries to dye out. anyone with any suggestions or help to get it to run better
Road Warrior
Joined: Aug 2008
Posts: 1,306
Likes: 865
From: Sheboygan, WI
just bought an o2 xl1200c has k&n air filter screaming eagle 2 pipes and i think stock carb. The problem is that during acceleration while riding and sitting in neutral the carb is spitting alot and bike tries to dye out. anyone with any suggestions or help to get it to run better
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5th Gear
Joined: Jul 2009
Posts: 9
Likes: 0
Thanks for the info Doc, I was also wondering why this happens. I have an HSR 42 carb as well and have noticed this exact phenomenon. I took the bike for a SHORT ride one day without the air filter assembly on and noticed a light misting of fuel being sprayed all over my leg.
