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Found 23 results

  1. I was riding my 2015 yz250fx at a local MX track and I came out of a corner slightly lugging the motor out of 3rd and the engine power dropped immediately and began backfiring with the compression over and over and would not gain power until I down shifted and it took off like a rocket. Only happened 2 times over a 3 hour span. But I'm scared it might randomly happen going up the lip of a jump. Bike has fresh gas and about 70 hours on it any ideas?
  2. Just tightened my valve lash to spec after having terrible clacking noise when idling. It would start before when cold with no choke at all but would click and clack when idling. But now, with the correct valve adjustment, the engine does not want to start. It will backfire and damn near break my foot so I know that it is definitely getting fuel. What is the best way to adjust the carburetors on these bikes? I know there is the large screw on the right side to adjust both of the slides for idle speed, but where is the air-fuel mixture screw on the carbs? I suspect this is my issue now that the valve lash is adjusted correctly. Any info or advice would be greatly appreciated.
  3. So I have a 2007 Yamaha YZ450f that I bought a few months ago. I took the bike out to desert for the first time, it was running PERFECT I was riding it for about 30 minutes and then all of a sudden it just started popping and was backfiring no matter what RPM I was at. I came to a stop and it just died, I started it up again, and I found the only way to keep it alive was by using the throttle. When I got home (sea level) I looked at the carb and noticed that the fuel screw fell out and was MISSING! I figured it must have fallen out while I was riding, So right away I bought a new Factory Effex fuel screw. When my new fuel screw arrived I installed it, and adjusted it 2 turns out. When I started the bike up with the new fuel screw, NOTHING CHANGED the motor wouldn't idle unless I had my hand on the throttle and was constantly backfiring on every RPM. So now I have the carburetor removed and taken apart, I could clearly see all the jets were clear. There is one thing that I noticed, a piece inside the carburetor was chipped off. When I took apart the carburetor the chip never fell out so I'm assuming whoever was working on the bike last must have dropped the carb and chipped it. After that I unscrewed the sparkplug, the sparkplug came out WET with fuel, figure this is due to such a rich mixture. I'm beginning to think that when the fuel screw fell out a piece of dust may have gone in it's hole and gotten into the circuit. Here's a picture of that chipped piece I was talking about. The fuel inlet needle looks good
  4. I recently purchased a brand new 2015 CRF250X. Since purchasing I installed the JD jet kit, and completed the air box mod. I live and ride in Kentucky, between 800 - 1200 feet above sea level, with the temperatures ranging from upper 70's to high 90's. I followed the JD jetting instructions and replaced the stock main jet with a 158 main, the pilot jet was changed with the 42 that came in the kit, and I replaced the stock needle with the red needle, with the clip in the fifth position from the top. I also removed the stock air mixture screw and replaced it with a R & D racing flex jet fuel screw backed out 1 3/4 to 2 turns. The bike has completely stock exhaust, with the OEM air filter. The bike seems to run alright, but there are a few things that I have some questions on. Before doing the mods to the bike you could pull the hot start lever all the way in and the bike would die. But now since doing the mods the bike will idle faster once the hot start lever is pulled in all the way. The same thing happens with the choke lever. Once the bike is good and warm if you pull the choke out the bike at first doesn't really do anything, but once you give it some throttle it will idle faster. The bike now has a backfire problem, which I never noticed before I did the mods. The backfire isn't necessarily a high pitched loud popping sound, but more of a low sound, almost like a large amount of air is being forced out. I've noticed the backfiring mainly happens when decelerating, or when dropping gears too quickly. My 250X does have the smog equipment attached. If I stall the bike while out riding it seems to be very hard to start, and most times I have to pull in the hot start lever to get the bike started. Before the mods I never used the hot start after I stalled the bike. As I try to restart the bike back it makes the same backfire noise like it does when I am out riding. The idle speed seems to not stay consistent. I'll warm the bike up and check the Works Connection hour meter and it will be reading around 1800-1900 RPM. Once I've been riding for some time, and come to a stop, the RPM meter will be reading more in the 1700 range. The RPMs at idle don't stay constant, I find myself adjusting the idle screw a few times while out riding. I am also having the problem of the bike randomly stalling. For example, I could come to a stop with the clutch engaged, sit still for a few seconds, and when I give the bike a little rev it will stall and die. The throttle doesn't even come open when it stalls, I just barely give it a turn and it will die. Like stated before, when this happens the bike is hard to start back, and backfires when trying to be started. I have tried playing around with the fuel mixture screw, but nothing seems to correct the problems I am experiencing. The bike seems to run fine other than the stalling and backfiring. I am not sure if changing jet sizes or clip position would correct the problems I am having. I have tried researching these topics, but nothing seems to be like what I am experiencing. Any advice would be greatly appreciated.
  5. Hey everyone, I just installed the GYTR FMF slip on exhaust today and got a few different problems. First thing I noticed was after turning the bike off, the exhaust started smoking out the back. Not a whole lot, but a noticeable amount of white smoke. When installing the exhaust I replaced the header gasket, and I also but Ultra Black Sealant on the slip on part of the exhaust. I'm assuming I used the wrong type of gasket sealant and that's what burning and creating smoke? It doesn't smell like burning oil or coolant, kinda smells like burning plastic if I had to describe it. Not very worried about this though, I guess i'll just let it all burn off or if it doesn't stop smoking, I will take it back off and try to clean it and use the right stuff. My big problem is the amount of backfiring; It only happens on deceleration. I did a quick check for exhaust leaks right after installing and didn't find any. I will do a more thorough check tomorrow. The exhaust that was on it before was a super heavy Lexx exhaust that was really quiet and probably very restrictive. Also the current map set is for super smooth and slow acceleration, all 0's and -'s (See picture below of the map). I'm assuming this smooth of a map is where my backfiring problem is? This is making me run lean correct? How safe is it to run the bike like this? Because I need to ride the bike tomorrow and my tuner won't come in until later in the week. Picture of my current map (middle one) & video of crazy backfiring:
  6. Hey all, Any help is very much appreciated. I have a DRZ400SM and was experiencing a few flat spots on the highway, meaning that when I hit 40mph the bike just lagged and then returned to normal at 45mph, happened again between 60-65 and 70-75mph. After doing some research on the the web I thought it might be a dirty carb. I watched a few tutorials and took the carb out. It was clean from what I could see, so I put everything back together. After getting the bike put back together it wouldn't start. Finally when I put it the petcock on Prime it started up, but when it started it was revving pretty high. I thought the revving was because I needed to adjust the throttle cable. So I adjusted the cable and started it again. After starting and sounded right it stalled. I figured it stalled because it was cold or there was only a little fuel in the system. I left it for a couple days and started it again. Everything seemed fine for the first couple blocks to the gas station, but then I noticed the bike wanted to stall. As I rode back home the bike struggled to make it and was back firing like crazy. Once home I noticed that the couple days I left the bike sit, it was in the Prime position. Ok, a few questions: I'm questioning whether I put the carb back in properly, thats why it didnt start initially. How can I check? It does start, but only in Prime. Wont start in On or Reserve position. Did leaving it Prime flood the carb? Why is it back-firing so much? I know these might be big broad questions, but ANY help is greatly appreciated! Thanks!!!
  7. I have a 2008 ktm 250sxf and I'm having a lot of problems with it. I missed yesterday's race because it wouldn't run right. It's idling really rough. Every few kicks it will back fire really loud when I get it to run it will idle rough and when I give it gas it will bog then when I release the gas it will rev high and is hard to come down. I will give it the smallest bit of throttle and it will stick at a really high idle and I have to rev it hard and quick a few times for it to come back down. When I put it in gear and try to ride it slowly it just tries to take off and it doesn't even feel like a high idle. I have to ride the front and rear breaks for it to not take off. I can let off the throttle and put it up to 6th gear and it still keeps going. I just had the entire top end replaced. Cylinder piston rings etc. I cleaned the carb several times cleaned all of the jets and still nothing. Replaced the throttle cable even disconnected it and still nothing. If I disconnect the throttle positioning sensor it runs a little better but is still pretty rough. I used a multimeter to test the tps and it seems fine other than when it's at "idle" it's at 1.14 on 20k I give it a little gas and it sticks at 1.17 until I rev it hard a few times. No idea what it could be. Needle and seat seem fine I'm stumped on it. Please help!
  8. sup guys, i got a bit of a story. a few days ago i bought a 2004 crf250r for 800 bucks off a guy who didnt know much except a few things... 1. has an oil leak (shift linkage seal was half out ) 2. had a 'full rebuild' by the previous owner 3. had a hard time starting so i snatched it up, hoping it would be a quick fix. its not exactly going that way. i brought it home, cleaned out the carb, and fired up after several kicks. the idle was pretty high, but wouldn't come down without completely dying on me. so as the bike is running and im trying to get the idle down, i noticed two things; 1. the thing backfires practically every 2-3 seconds and 2. the exhaust pipe was so red-hot, it looked like it was about to turn into a damn puddle of molten metal. realizing there was something seriously wrong with the bike, i shut it off. this brings us to my first question. why in the frick is my pipe getting red hot and shooting flames after 60 seconds or running ? and whats with the back firing ? now for part 2 of story time. with a bit of research my dad's opinion, i assuming that there was some sort of problem with the exhaust valves. long story short, the exhaust valves were perfectly fine. my next thought was to check the timing. take a look at the pictures in the link below and let them speak for themselves. https://www.pinkbike.com/u/Ziggypop14/album/nothing/ as you can now see, the notch on the magneto cover does not completely match up with the notches on the flywheel. i noticed there are two notches on the flywheel, where should the notch on the cover versus the two on the flywheel? im assuming in between the two? i researched and found a few things that could be at fault. 1. the cam cog slipped on the shaft. which really cant be it since at TDC the two notches on the cam cog are still completely level, and if the cog slipped, the notches would be off. Right? 2. the flywheel slipped on the crankshaft. this one makes the most sense because how else can the flywheel notches be off while the other notches are dead on. but how the hell is that even possible? the flywheel nut is so tight that i cant even get it off to see if the keyway is still intact. (still trying to get it off, jamming sockets in gears) unless the idiot who rebuilt the bike didnt put the keyway in (which is entirely possible), i cannot see this as the solution. this brings us to my 2nd and final question. Why aren't the flywheel notches lined up even with the piston at TDC and everything else lining up ? any help is is appreciated, i need my garage back!! cheers, Riley
  9. Hello everyone, I recently picked up my second KTM dirt bike, a 2015 350 XC-F after coming off my older 2006 250 SX-F. It kept having issues where the bike would completely die on me while riding. I sorted this out by putting new in fuel filters both in the tank and the small inline filter. It fixed my engine quitting problem, but then I realized I had a decel backfire and poping problem that to me sounded like it was because the engine was running too lean. I checked my valves to rule out a valve problem. Then I looked to the TPS on the bike. I read somewhere where someone said you could turn up the TPS to get it to quit. I incrementally stepped up the adjustment until the backfire went away completely. The problem is that it is turned all the way CCW. With the adjustment turned all the way up it runs like a champ. No back fires, no flameouts, pulls really really hard and the plug has that nice tan color to it that I would expect from a FI bike. The only thing that worries me is that if I put the sensor back at the .60-.70 voltage range where people say that they have been running them, the bike hardly idles and stalls at the crack of the throttle, but when I turn it back all the way up CCW it fires up and is unstoppable. My concern is that it isn't running at the stock voltage or even close to it. Also, I cleaned the injector using a 9v battery and aerosol injector/carb cleaner. I got some small pieces of dirt out but nothing big and it didnt change anything. I am new to these FI systems, but I thought they adjusted the fuel mixture automatically so to me it doesn't make sense why turning up the TPS changed the backfire. And I dont think it is a valve problem because of how it fixed it when I turned up the TPS. My question is 1) what is wrong with the bike to where it won't run at the stock voltage and 2) Am I hurting anything by running it how it is? Am I burning more fuel? I have been trying everything and I am pulling my hair out trying to figure out why it is doing this. But I have a new Lexx Exhaust with spark arrestor coming so I can ride in the mountains and if I have to turn the TPS up anymore to adjust for the new pipe I am up a creek because it is already maxed CCW. Thanks in advance for all your help, Josh
  10. Howdy, This coolster has run rough since I got it and I have not been able to figure it out. Basically it only runs clean at idle if the choke is left on. If you turn off the choke you have to turn up the idle a lot. Even with doing that it bogs, pops, spits. When riding it stumbles and pops then goes again. See video: Let me know if you all have any suggestions thanks!
  11. I have a 2014 DRZ400SM with about 28,000 miles on it. I have had it since last summer. Since then, I have done the 3x3 mod with a JD jetting kit and added a K&N Air filter. I have been running a 155 Main Jet, the Blue Needle with the clip on the 3rd slot, a 125 pilot jet, etc. Basically, exactly as recommended by JD. The bike was running fine until recently. It started sputtering, backfiring, and missing around 5k rpm, especially in higher gears. I thought maybe this was due to the weather warming up, and I was too rich. I tried swapping out the main jet to a 145 (the next smallest size I had handy), but it was doing the same thing. I tried then switching to a 160 main, and it seemed a little better, but then it was doing the same thing. I thought maybe it was something more complicated than just the carb, so I checked the valve clearances. They all looked good and were in spec. In the process, I checked the sparkplug and it looked suspect, so I replaced it. No Dice, still sputtering at 4-7k rpm. I was riding it, trying to further diagnose it, and I noticed some white smoke coming out the exhaust (coolant?). The Oil looks normal (no milkshake of death) on the dipstick, so maybe not a head gasket issue. Would that even cause the problems I've been having? I also noticed a screw had escaped from the top of the carb (that holds the black cover on). Surely that must be the problem! I replaced it and... still the same issue. I tried recording the issue, though apparently didn't have much space on the memory card, and the sound is not as clear as I expected. I can try re-recording some footage to demonstrate the issue. Anyone have any idea what could be the problem? I may just try to revert as much back to stock as I can (don't have the stock exhaust). I am beginning to wonder if the issue is not related to the carb at all. Thanks in advance.
  12. I read a lot about some people having problems with their TE 310 but I guess I thought "that surely will not happen to me, right?". Well I took my new/demo 2012 TE310 for its first real outing. We did some technical trail riding today and I started having problems after the bike heated up. First, the electric starter just quit working, not sure if it is a problem with the starter or with the battery (supposed to have a new battery in it when I bought it). When I would turn the key on you could hear the pump still kick on even though the electric start would not work. Then sometimes when I would kick it over it had a weird feel to it, like when I kicked it over the starting was trying to turn as well. The bike would not start, but if it caught at all it would backfire very loud. Then I could kick it over and would usually start. After I rode for about another 45 minutes I noticed the bike did not want to idle. I had to really stay on the gas and the clutch to keep riding. Engine seemed really hot and the cooling fan never turned on. Bike then did not want to stay running, if I slowed down it would not idle and would shut off. When it was still hot I would try to kick it over, I could get it to start but would not stay running and sometimes would backfire (again loud) not start. Do not know what to tell the dealer, what to look for, and what I might try. Dealer is a long way away, very disappointed and frustrated. Any help and/or suggestions would be greatly appreciated. Thanks,
  13. I own a 2009 kx250f and recently rebuilt the motor. I put a new top end in and replaced the valves and shimmed them to spec. The bike ran great for roughly 12 hours then one day at the track in the middle of riding it started to bog and backfired really loud. I continued my lap and it repeated the same thing then the bike just died. It then wouldn't start so I bump started it and it ran for about 3 seconds then died. I took the bike home and rebuilt the carburetor and put a new spark plug and fired it up and it ran for about 3 seconds again and died. I don't know where to go from here except taking it to a shop. If anybody has any ideas i'd highly appreciate your opinion!
  14. I bought a lean running '03 CRF230F. The previous owner had swapped in a high compression piston, removed the baffle, but did not adjust the carburetor or jetting (to my knowledge). The bike would regularly backfire on deceleration. Anyways, I did the fuel screw procedure and I have adjusted the fuel screw to 2 3/4 turns out because that is where it idles the best and the bike now only backfires when shifting into 2nd occasionally. However, acceleration in high gears feels a bit delayed and boggy. Too rich? Too lean? Should I bring my fuel screw in to 2 1/2 turns instead (bike seemed to idle just as good at this adjustment, with a little bit more popping while riding). My spark plug looks good to me, but I'm open to different opinions. Bottom line: Slight popping when shifting from first to 2nd, high gear acceleration feels delayed but I can't tell if it's a lack of fuel (lean) or a bit too much (rich). What's the next step? Thanks!
  15. Hello, new to the forums and been wanting to join for awhile. Anyways, down to the problem. I have a brand new 2018 Honda Recon and everytime I get it into the high RPM's it always seems to backfire. Not sure if this is a good thing or bad, but I used to ride a dirt bike and it rarely backfired. Just curious, maybe its not a big deal either way I'd like to know. P.S I didn't really know where to post this, forgive me if it belongs somewhere else.
  16. I noticed my 17 KTM 250 SX-F backfires regularly when letting off the throttle. Is that normal?
  17. Hey all, Just installed my yoshimura rs2 full system and have been having alot of backfire on deceleration and engine breaking. The bike has a 3*3 mod and jd jetting. The kit says to use the 165 vs the 155 if you have full exhaust. Could the issue be having the 155 installed and not the 165? Or could it be a header leak. It looks like the flange on one side is just barely not flush but it will not tighten anymore than it already is. If you think it is a header leak what is an easy way to test that? Im thinking its the jetting, but thats just my amateur opinion. Any thougts?
  18. Hi so I just changed the timing chain on my YZ450F 2005, I used the dot on the flying wheel as reference for T.D.C. as in the pictures, and adjusted the cam shaft accordingly but when I try to start it only back fires after a few kicks. I have checked the spark plug and I have spark and the plug is vet with petrol, and I for sure have compression (did not need any work out that day) I have double checked that the fly wheel is in the right position accordingly to the spline on the crankshaft. Thankful for any suggestions on what the problem might be! Cheers.
  19. i have a 140cc with 23mm/27m Big Valve Head engine from Orion Power sports that came with valves not tuned properly i got that tuned and had my old 22mm carburetor on it and it runs rich when full throttle it backfires and slows down and when kicking it i need a boot because it backfires and the kick starter comes back up with a good amount of force it also doesn't have any compression a lot of the time so i have to find it. The website recommend the 24mm Mikuni carb tho and it runs way too rich with smaller jets and adjustment.are my problems with the carburetor or something else?
  20. I have a 2006 Yamaha TT-R 230. For the past year or 2 I have had to clean the carb a lot. Recently, after cleaning the carb, it still would not idle without the choke and sometimes even with the choke on and would backfire on deceleration. Very hard to start. I have done the air box mods and removed exhaust baffle. I have the 130 main jet and 38 pilot jet along with the mixture screw turned out 1 full turn. I have checked valves and they seem good. My float bowl O-ring is done for but I don't think that would make that big of a problem. Gas should not be the problem. Just want advice before I start buying a bunch of stuff to repair.
  21. First off, thank you everyone for your input to this site, it took an issue for me to make an account but I have been getting info off of this site for well over a year. So I have an ongoing issue on my '01 DRZ400S. The bike on two occasions now will run fine, then after 10-40 miles start acting as if low on fuel, backfires several times and finally dies. It will take a few minutes, but then will start fine and once again dies after a mile or so. After the first time, I took off the tank, petcock, carb and lines, cleaned them out with no obvious issues found. I took it out for a 27 mile ride with no issues. Then took the second trip where it died after about 40 miles. This bike has had the CA emissions removed, free power mod completed, and I had put in a new stator before this issue came up with loctite fixes. Otherwise the bike is stock. After the second time it died, I have checked the spark plug, cap, ignition coil resistance, stator resistance, pickup coil resistance and signal coil resistance. Everything is within specs. I have been told it may be the CDI, but then saw here its not an issue on this bike. Just need some input as to where to go from here. I don't want to start throwing money at it if I don't have to.
  22. Thanks for taking a look. I hope someone can point me in the right direction to get this headache solved. I'll try and be as detailed as I can without bombarding you all with a wall text.. My bike is a 2005 DRZ400S with over 20,000 miles on it (mostly highway but lately more dirt). I just recently brought the bike in (after a good 3 hour ride in the mountains) to a local motorcycle service shop (Cycletune in Portland, OR). They did a list of maintenance work as well as replaced the tires, relocated my ignition switch, removed side stand switch, etc. I took the bike back home and it died after about 15 minutes on the highway. Now, my bike is experiencing intermittent loss of power, backfiring, stalling, etc. The mechanics working on my bike threw up their hands and told me they tried and couldn't figure it out. They said they did not believe that they caused the problem and did not know what was causing it. They said that they could "start throwing parts at it" and charge me hourly to try and figure it out... Before my bike died on the highway and was towed back to the shop, I got their "level 3 service" (highest service package available). This service included: Oil and filter change, Battery check, Wheel & tire inspection, Cooling system check,Inspect/clean air filter,Lube/adjust all cables and pivot points,Clean and adjust chain/belt,Inspect brake system,Check electrical system,Inspect clutch components (external),Fastener check,Set tire pressure,Safety check,Spark plug replacement,Carburetor/throttle body synchronization,Inspect/change transmission fluid/driveshaft fluid,Inspect steering head & wheel bearings,Cooling system check & flush if needed,Brake and Clutch,fluid flush. After they took my bike back in and couldn't fix the intermittent problem, they gave me a handwritten letter saying the following: "Level 3 service was perfored. All fluids changed. Valves checked (within specs) side stand switch eliminated. Bike had intermittent stalling problem and was towed back to shop. Problem was eventually replicated on test ride. Intermittent cutting out, loss of power. Eventual stalling was experienced. Fuel petcock was checked at the time of stalling - appeared okay. Correct level of fuel was found in float bowl at time of stalling. Pick up coil was replaced. New pick up coil did not solve problem. Intermittent problem still exists." Here's a sound clip of the problem (it starts around 0:14). Bike was warmed up for about 10 minutes before the audio was recorded. The bike idles just fine. Any ideas on what is causing this? I'm somewhat mechanically capable so I'm going to try and fix it myself (partly because I lost faith in the shop I went to for a variety of reasons and don't trust that they will fix it and partly because other local shops have a wait time of 4+ weeks to get my bike in). Thank you!
  23. Hi All - I'm new to this forum. I have a 2009 KTM 250 SXF and it's backfiring somewhat violently when engine braking/decelerating. (I am not actually engine braking to slow me down, just when I'm decelerating and RPMs go up. I will just use the term "engine braking" for the rest of this post even though it's mostly decelerating). It revs great and has no backfires then, only when engine braking. I rebuilt the Keihin 39 FCR carb and it has a R&D Power Bowl 2 on it as well as an adjustable fuel screw and leak jet. I also redid the valves and checked the timing. The timing was perfect but the valve clearances were a little off. I put in new shims and everything is perfect up there now. The plug and piston are clean and the carb is in mint condition after the rebuild and there is still a backfire when engine braking. I adjusted the carburetor to stock settings and it won't start with the fuel screw at 1.25 turns out. I have to turn the fuel screw out 2 turns to get it to start but there is a backfire when reving. At 3.25 turns out, it revs without any backfiring but is way out of stock settings; it still backfires when engine braking at this setting though. I'm running around a 45 leak jet and all of the other jets seem to be somewhat normal sizes; my elevation is about 6000 feet. My idle seems to be dialed but something is definitely wrong if I'm having the screw almost 3x stock settings. I don't think it is a lean backfire/bog unless something in the carb isn't functioning correctly because I'm already running so rich. The squirt from the accelerator pump is perfect and I don't know what to do anymore. Any Ideas? Does anyone know what's wrong? Thanks!
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