03 vstar 1100 lots of backfire
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  1. #1
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    03 vstar 1100 lots of backfire

    Hey Easy Rider, Sinical, you out there? I'm the guy that had all charging problems last year and changed out the stator. I've talked to you guys before about deceleration backfire, popping and spit n' sputter. The carbs are the stock BSR37 Mikuni, I put Hypercharger intake, Cobra exhaust and a Dynatek 3000 ignition module. I put in new stock coils and BPR7ES spark plugs. Front carb jets are 125.0 main and 17.5 pilot, the rear has 122.5 main and 17.5 pilot. Bike starts and idles ok after it warms up, but if I bring rpm to 1500-2000, it spits n" sputters then smooth out a few seconds then stutters again, runs smooth, then spits n" sputters again. On the road when I slow down or have to come to a stop it backfires, not good! The last time I had this problem I was in a truck, it backfired and came to stop. The timing chain had jumped and bent all the valves! I've tried synchronizing the carbs, no change. One of you said this is a symptom of a lean condition, okaaa lean huh? Vacuum leak? Well I put new carb mounting boots in, figured their old, maybe cracked, no change. Bikes old but so am I, I hope I out last the bastard!

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  3. #2
    Super Moderator

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    So.....after all those modifications that you did, it really runs better now, doesn't it ??
    NOT.

    Sorry couldn't resist.

    Yes, what you describe are the classic symptoms of a lean condition due to improper changes to the fuel system.

    While loud pipes are illegal and obnoxioius, I won't dwell on that.......too much.

    Try running with the choke partly closed and see if it improves.
    If it DOES, then you have a couple of choices:
    Put a stock airbox and filter back on it.
    Put some baffles in your pipes.
    OR....
    Research what jets you need for your present setup.
    You do not have the option for an adjustable "fuel controller" like fuel injected systems have.

    Unless you have a vacuum leak, those are about your only options.......other than just live with it and be easy with the throttle, that is.
    Don't believe everything that you think.

  4. #3
    Ditch Magnet
    My Bike(s)
    2002 SV-650N, 2007Yamaha 1100 custom
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    NW Pa.
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    https://sites.google.com/site/vstar1...-modifications there's some info here about hyperchargers.lots of other info to

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  6. #4
    In Training
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    99 xvs 1100 vstar custom
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    land of 10,000 lakes
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    Quote Originally Posted by 031100 View Post
    Hey Easy Rider, Sinical, you out there? I'm the guy that had all charging problems last year and changed out the stator. I've talked to you guys before about deceleration backfire, popping and spit n' sputter. The carbs are the stock BSR37 Mikuni, I put Hypercharger intake, Cobra exhaust and a Dynatek 3000 ignition module. I put in new stock coils and BPR7ES spark plugs. Front carb jets are 125.0 main and 17.5 pilot, the rear has 122.5 main and 17.5 pilot. Bike starts and idles ok after it warms up, but if I bring rpm to 1500-2000, it spits n" sputters then smooth out a few seconds then stutters again, runs smooth, then spits n" sputters again. On the road when I slow down or have to come to a stop it backfires, not good! The last time I had this problem I was in a truck, it backfired and came to stop. The timing chain had jumped and bent all the valves! I've tried synchronizing the carbs, no change. One of you said this is a symptom of a lean condition, okaaa lean huh? Vacuum leak? Well I put new carb mounting boots in, figured their old, maybe cracked, no change. Bikes old but so am I, I hope I out last the bastard!
    you are running lean at speed. Hyperchargers are hard to tune for. They act as a ram air. So as your speed increases it forces more air in. The cobra exhaust is baffled. https://sites.google.com/site/vstar1100kb/home/tuning if it spits and sputters your dynateck isnt advancing timing like it should. is it on the correct setting? Try the factory cdi box. decel pop is the fuel burning in the exhaust. It happens even in factory exhaust, it just isnt heard because of the baffles. its unburnt fuel in the exhaust. When you ritchen the mixture it makes it so the fuel cannot burn in the exhaust.

    So first, adjust the valves, then sync the carbs. Did you add a shim under the main needle? and pms screw to 2 turns.
    Last edited by DivineChaos; 06-19-2019 at 10:27 PM.
    We gain knowledge by watching, doing, listening, and teaching. Not by insulting. We all can say mean things nicely.

  7. #5
    Ditch Magnet
    My Bike(s)
    2002 SV-650N, 2007Yamaha 1100 custom
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    NW Pa.
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    the hypercharger uses the stock airbox. so idle and lowspeed putting around town you would not have to change any settings.but it does act as a ram air so you have to tune accordingly.the mains only come on at half to wide open throttle so do not come into play at casual riding.i would put things back to stock and get it running good before doing the hyper charg, again. 17.5 pilot jet is good at stock. the pms screw should be about 2 turns out for stock setting. don't mess with the air screw until your ready to install the charger then follow the instructions that came with it.if you changed the needles put the mikunis back in.usually jet kits come with dyno jets and needles which are calibrated different. you can google dyno jets verses mikuni jets for a reference.your backfiring suggests something's not together right so go back and start over... a little popping is workable but back fire says something is far out of adjustment
    Last edited by nickbehavin; 06-20-2019 at 07:00 AM.

  8. #6
    Super Moderator

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    Quote Originally Posted by nickbehavin View Post
    the hypercharger uses the stock airbox. so idle and lowspeed putting around town you would not have to change any settings
    Does it also use the stock air FILTER ??
    If not, there will be a bit less restriction and that usually shows up most at idle with a leaner mixture.
    When there isn't much volume of air flowing, small differences can be important.
    Don't believe everything that you think.

  9. #7
    Ditch Magnet
    My Bike(s)
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    your right about small adjustments. my suzuki sv was popping on decell so i backed the screws out 1/4 turn now i have a different set of problems. i have to pull the carbs and turn them in 1/8th of a turn. and then check the plugs after a couple hundred miles.its very delicate i'm having to get the screws and sinc to work together

  10. #8
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    DivineChaos, you hit the nail on the head. I adjusted the valves earlier. I checked for leaks in (they have an internal diaphragm that operates butterfly gates) and around the hypercharger. I pulled the seat and checked the Dynatek ignition module. These things have 8 switches on the back that can be activated according to the way the bike is set up. This was set wrong, nothing said about settings for hyperchargers exactly, just if a switch has been made to a higher air flow intake, and yes Cobra exhaust is baffled, and I needed to jet accordingly for this also. I made all these changes at the same time. Bike ran good. Then I had all the charging problems. Along with changing the stator and r/r out and puting it all back together I must have put the ignition module back and somehow flipped some of the switches on back to the on position. These switches change the timing of when to send the electrical charge to the plug(advancing timing), with settings of basically stock all the way to if the bike is running nitrous. Set the module correctly, sync the carbs, intake and exhaust changes, pms had to be turned out 3 turns, ran the bike and checked the plugs. Plugs burning light tan, may bumped the jets up 1. NO popping, NO backfire and running strong. Thanks for the link on hyperchargers Nickbehavin.

  11. #9
    In Training
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    Quote Originally Posted by Easy Rider View Post
    Does it also use the stock air FILTER ??
    If not, there will be a bit less restriction and that usually shows up most at idle with a leaner mixture.
    When there isn't much volume of air flowing, small differences can be important.
    the hyper charger replaces the factory dog bowl air cleaner. The restriction in the factory intake is the air box under the tank. That is what restricts the airflow. the air filter is negligible. I removed the air filter in my stock intake just to check. maybe 1\4 turn more out on the pms screw.
    Last edited by DivineChaos; 06-20-2019 at 08:06 PM.
    We gain knowledge by watching, doing, listening, and teaching. Not by insulting. We all can say mean things nicely.

  12. #10
    In Training
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    Quote Originally Posted by 031100 View Post
    DivineChaos, you hit the nail on the head. I adjusted the valves earlier. I checked for leaks in (they have an internal diaphragm that operates butterfly gates) and around the hypercharger. I pulled the seat and checked the Dynatek ignition module. These things have 8 switches on the back that can be activated according to the way the bike is set up. This was set wrong, nothing said about settings for hyperchargers exactly, just if a switch has been made to a higher air flow intake, and yes Cobra exhaust is baffled, and I needed to jet accordingly for this also. I made all these changes at the same time. Bike ran good. Then I had all the charging problems. Along with changing the stator and r/r out and puting it all back together I must have put the ignition module back and somehow flipped some of the switches on back to the on position. These switches change the timing of when to send the electrical charge to the plug(advancing timing), with settings of basically stock all the way to if the bike is running nitrous. Set the module correctly, sync the carbs, intake and exhaust changes, pms had to be turned out 3 turns, ran the bike and checked the plugs. Plugs burning light tan, may bumped the jets up 1. NO popping, NO backfire and running strong. Thanks for the link on hyperchargers Nickbehavin.
    no problem. it seemed like ignition timing to me. glad i could be of service. And i advise removing the factory airbox and adding pods. Adding 150 jets pms to 3 turns. you will have more power than your hypercharger.
    We gain knowledge by watching, doing, listening, and teaching. Not by insulting. We all can say mean things nicely.

  13. #11
    In Training
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    land of 10,000 lakes
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    Quote Originally Posted by nickbehavin View Post
    your right about small adjustments. my suzuki sv was popping on decell so i backed the screws out 1/4 turn now i have a different set of problems. i have to pull the carbs and turn them in 1/8th of a turn. and then check the plugs after a couple hundred miles.its very delicate i'm having to get the screws and sinc to work together
    All syncing the carba does is make sure they are drawing the same vacuum. It has very very little to do with pms screw adjustment. If the cars arent pulling the same vacuum it will make it impossible to adjust afr correctly.
    We gain knowledge by watching, doing, listening, and teaching. Not by insulting. We all can say mean things nicely.

  14. #12
    Ditch Magnet
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    2002 SV-650N, 2007Yamaha 1100 custom
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    its funny my screws are the same amount of turns out, but it sounds like one cylinder is lean and the other rich. i have the sinc very close the bike runs very well. it's justwhen i'm between on and off throttle at any speed it's jerky, and pops a little. i'm going to turn the screws in an eighth.

  15. #13
    In Training
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    land of 10,000 lakes
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    Quote Originally Posted by nickbehavin View Post
    the hypercharger uses the stock airbox. so idle and lowspeed putting around town you would not have to change any settings.but it does act as a ram air so you have to tune accordingly.the mains only come on at half to wide open throttle so do not come into play at casual riding.i would put things back to stock and get it running good before doing the hyper charg, again. 17.5 pilot jet is good at stock. the pms screw should be about 2 turns out for stock setting. don't mess with the air screw until your ready to install the charger then follow the instructions that came with it.if you changed the needles put the mikunis back in.usually jet kits come with dyno jets and needles which are calibrated different. you can google dyno jets verses mikuni jets for a reference.your backfiring suggests something's not together right so go back and start over... a little popping is workable but back fire says something is far out of adjustment
    When traveling at 70mph my tach reads 3900 or so. Stock redline is 5800 unless im mistaken. So the mains are being used at highway speeds @nickbehavin. Could be wrong.


    Mine pops through the carb only when cold. Which is a result of the mods i have done.
    My decel pop sounds like backfire through the exhaust. It spits flames. under hard accel at night there is small flames at times. It is optimally tuned, just a bit loud. lol. Custom 1 1\2" baffled rag pipes, pod filters. 1 turn on pms. 150 mains and 20 pilots.
    We gain knowledge by watching, doing, listening, and teaching. Not by insulting. We all can say mean things nicely.

  16. #14
    Ditch Magnet
    My Bike(s)
    2002 SV-650N, 2007Yamaha 1100 custom
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    NW Pa.
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    175
    i'm about the same rpm at 70.i don't know much about the mains but at 70 your probably at half throttle, more or less. i'm running pods 20 pilots two shims and 3.5 turns on the pms. if i let the bike sit after a ride for an hour sometimes it spits back thru the carb. your lean on the screws with pods they should be 2.75 to 4 turns out.at 1 turn out your plugs must be white as senator Byrd, rip.

  17. #15
    In Training
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    Quote Originally Posted by nickbehavin View Post
    i'm about the same rpm at 70.i don't know much about the mains but at 70 your probably at half throttle, more or less. i'm running pods 20 pilots two shims and 3.5 turns on the pms. if i let the bike sit after a ride for an hour sometimes it spits back thru the carb. your lean on the screws with pods they should be 2.75 to 4 turns out.at 1 turn out your plugs must be white as senator Byrd, rip.
    dont know who that is... I suppose it isnt a backfire, more of a spit because it doesnt go bang.

    I monitor my temps. at 4 turns it is dog rich. like fouling plugs. I had run that setting with 17.5 pilots and 147.5 mains, found it was too rich up top. was getting 30mpg. and if the air temp gets up there i ritchen the mixture. Have rode 3k miles this year with this tune. Right now i average about 38 combined. at 70mph i get 40. at 60mph i get 45mpg. Probably should check my plugs. they will be eroded and ashy if too lean.
    They were black (and carbon fouling) before i changed jets. One of the previous owners had messed with the carbs. the diaphram slide was messed with also. There was 2 holes drilled in the bottom that were widened from stock, so i believe the needle raises higher than normal. Carbs synced, valves adjusted. id let you look at it if you ever made your way to the Iron Range here in MN.
    if there was a shop that did carb work on modified bikes, i would have them tune it.
    But, all the ones ive called either said if its modified they wont tune it, or they dont work on carbed bikes anymore. And the harley stealorship? $170 an hour. 1 hour minimum, plus a $80 service fee.
    We gain knowledge by watching, doing, listening, and teaching. Not by insulting. We all can say mean things nicely.


 
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