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  1. I have very little experience tuning carbs so I need help getting pointed in the right direction.. My 98 yz250 is hard to cold start and fouls plugs every once in a while when I'm trying to cold start it. Just need some advice on where I should start with changing jets and how to know when to stop. Normally I would just start with factory settings but I don't think that's a good baseline since I put a 2001 kx250 pwk carb on it to replace my pwm as I was told that it was a decent upgrade to the pwm and I was having trouble with the pwm anyways Currently my specs are: Air screw 2t out 168main 50pilot Br8es Pro circuit pipe Fmf shorty recently repacked. 40:1 Lucas semi synthetic Unsure of needle size or height but likely it's stock from the kx. (Mids feel normal to me anyway) I live and ride at about 3500ft and usually only ride if Temps are 50°F -100°F and normally 40% humidity And I blocked off the "pump jet"? On the pwk with a bolt. The bike runs really good other than starting cold and every once in a while it will take 5-6 good kicks to even hot start right after shutting off the engine. Also I've noticed it will "cough" as I'm hitting the kill switch every now and then. Haven't actually measured compression but it feels strong on the starter and the bike is scary fast so should be good there. Also I'll attach some pictures of the plug with about an hour of runtime on it total. I know I probably just need to go down a few sizes on the pilot, main, and maybe adjust air screw a bit, but no idea by how much on either so any help would be greatly appreciated! I'd rather ask than blow stuff up.
  2. Hello there everybody.. new to ktm bought an 09' 300xcw and it ran great for about 10 hours then all of a sudden as I was riding in the yard she acted like she's running out of gas when the power band starts to hit nice and good... put a fresh air filter in it and I pulled my carb and cleaned it good and blew compressed air in every hole.. but still same issue.. before I just take the dang thing into the dealer can anybody point me in the right direction what else could possibly cause this? Found a similar thread that may point to the stator and it came with what looks like an old stator in a box notnsurenifnits related but not sure doesn't sound right to me seems like a carb/fuel issue figured maybe you guys would have a better idea? I will be cleaning my fuel petcock next but running out of options here Symptoms: lots of torque down low just acts like it runs out of fuel once the power band hits and recovers immediately once out of powerband... kind of stumped here. Temps have been about the same so I don't think jetting is an issue either because it ran perfect and starts 1 kick cold.
  3. New to all of this currently my bike (xr200r) is jetted for high altitude being in Colorado but I'm moving back to sea level cape cod. a new carb is less than 30$ so I'll probly just do that rather than have to rejet every year i go out and it old anyways. But what's the thought on this just adjust the fuel air screw or what i was also trying to ride a few spots close to i80 omw home if anyone has any ideas on that.
  4. Hi fellow thumpers, firstly if there is other threads on this topic I apologize. i have a 2009 KTM 450 exc. I live at 5500 feet. I have a keihin carb. I currently have it set up with green needle (jd kit) @ 4th from the top main #175 pilot #42 in setting it up for some desert riding I plan on doing next month (LAB2V). Right now I’m getting a bog if I rack the throttle a few times. I’m reading this is semi normal as the accelerator pump has a hard time refilling. i have put a new diaphragm, spring, lean jet is at #40 and air fuel acre 1 and 1/8 out. im planning on going back to 172 main, red needle 5th from the top and #45 pilot. i normally ride the trails around lake arrowhead and Big bear in California. The trails are single track from 5000-10000 feet. Anyone see any issues with either set up? how about the big if I get on it a few time ( not really noticeable when riding) sorry for the questions. This is my first carb I’ve ever worked on. Thanks in advance
  5. Hey guys I've been using the forum for advice for a long time, usually just searching but I've created a weird enough problem for myself I had to make an account and post. I have a 1998 WR400, bought it used and abused. Last season I got her running well enough, drilled the exhaust, and opened up the air box but didn't change anything else. Getting it ready for this season I was getting into it and found that the slide in the stock carb was cracked, and the inside was all gummed up. After a bit of searching it sounded like the consensus was that you can just throw a WR450 carburetor in no problems. So I bought this https://www.ebay.com/itm/Yamaha-WR-400-F-WR400F-Carburetor-Carb-1998-2000-NEW/123166146174?hash=item1cad463e7e:g:hmcAAOSwZKBZJcS1:sc:USPSPriority!93446!US!-1 and popped her in. I blocked off the old hot start hole with some vacuum plugs but I cant get it to start for the life of me. I've tried kicking it a billion times with settings on the fuel screw from about 1/4 to 2, with no success. I did get it to start once at about 1.5 turns, but it died fairly quickly and I couldn't replicate it. I threw a new plug and air filter in as well, but no other changes. Anyone able to point out what stupid thing I'm doing?
  6. I recently found this advertisement around my area on kijiji for a keihin carb for 50$ canadian. The owner states it’s off a 1984 cr 250. I was thinking for this price it would be worth it to have a spare. I’d obviously have to change the jetting and tune it. The carb itself looks exactly like the one on my bike at the moment. I was looking for a float for my yz 125, called the dealer and they said it was going to cost 90$, so I’m thinking it would be worth it to buy this carb for my yz 250 If it fits.
  7. My fuel air mixture screw fell out a few months ago, I did get a new one from a shop a few months ago from Yamaha but it doesn’t fit? Any help appreciated, Going to college and need to sell.
  8. Hey Guys, I hope somebody can help. I have a 2003 DRZ 400E with a Keihin FCR39 carb. The bike starts easy, idles well and pulls nicely. It really runs well, but it dies instantly at WOT. Doesn't matter when or how fast I am going. If I open the throttle all the way the engine dies. If I am riding and close the throttle a bit, then she fires up again and i can keep going. I'd say she has full power and pull all the way up to 95% just that last bit is missing.
  9. I have a 2002 wr250f with stock cams ,manual decompressed, I just received my stage 1 hotcam exhaust in mail, before I took out stock exhaust cam I counted the pins on chain, I came up with 13, the dots on cams lined up flush with cylinder head, i installed the new exhaust hotcam pulled all the slack from front of chain. The dots line up flush with cylinder head, but now I count only 12 pins, I have enclosed a couple pictures, my flywheel mark lined up perfect with mark on engine case, does this look correct, I'm thinking the hotcam might have slightly different cam dots, it only has 2 verses the 3 dots that stock cam has.
  10. I have a 2019 Kx100, completely stock. I am looking to put an Fmf fatty expansion chamber as well as an fmf shorty silencer. Stock from the factory, the Kx100s come slightly rich, which is true on my bike. Spark plugs are black, and I have fouled one already. I am waiting to put the pipe on to mess with jetting, but the real question is that if my bike is rich already, and I add a new chamber and silencer, would that possibly make the bike leaner, or would I still have to go down in jets or needle clip? If so, recommendations on what jets or needles I should change to? All jets are stock, with stock NAPF needle. Thanks
  11. Hello. I bought my son an 06 klx 110 with a 143 big bore kit on it. It ran crappy for the first summer and I knew it was probably the wrong size/jet carb (has an OKO currently). After sitting the last year...it would only run on choke so I knew we had some clogging issues. We cleaned it out and it now runs off of choke but it still has issues. If you slowly roll on the throttle it is ok but even the slightest blip and it totally dies out. I'd like to just get a new carb all together since the current one seemed to run very lean anyways. I know knock off carbs are frowned upon but he rides the bike in a small circle in our front yard so i dont want to spend $100 on a Mikuni vm26 just for 2nd gear putting. Does anyone have a recommendation on a cheap carb that is sufficient for the 143 kit that's on it? All of the vm26 knockoffs I see for around $40 have a bolt on intake end and the bike has the rubber intake with hose clamp setup. Is there a cheap carb that has the hose clamp on both ends or can i take the bolts off of the rubber intake and directly bolt the new carb to where the rubber intake now bolts on? Any help is appreciated!
  12. I have a 07 rmz250, full yosh exhaust mild ported and polished head. I run 91 non oxy fuel. What jetting should I run? My bike is a Franken bike. I took 2 bike and built 1. My carb came off a 07 that had the yosh exhaust and a high comp piston. I did not change the carb jetting. I'm curious if I should. Ot seems to run fine. Any info is appreciated
  13. Another topic on my rm125 project. I finally have my bike rideable. However it is to rich and plug's are expensive for this bike. I have stock jetting with a FMF gold series pipe and shorty spark arrestor. The needle is set halfway. I was considering dropping the needle down one knotch to lean it out but I was wondering if anyone else has gone through this problem and had any suggestions. Thanks in advance
  14. Due to the large amount of phone calls regarding this topic, it is prob a good idea to post up some "information" regarding this. highly debatable, subject(s). Not going to get real indepth but touch on a few basics that constitute what is required in order to have true elevation and temperature control with ANY carburetor. A few "concepts" on carb function:Again, not 100% encompassing, just basics. 1) ALL carburetors function on a pressure differential (Delta P) between the Carb Float Bowl and Engine. 2) This Delta P is what will,largely,determine how much "signal" is present to "pull" fuel up the needle jet into the engine. 3) Larger Delta P will equal more fuel flow and vice versa. 4) The engine will always be the low pressure side and the carb will always be the high pressure side. 5)We can consider the engine side a constant vacuum in terms of pressure (even though it varies) 6) The Carb float bowl pressure will vary with elevation. As you raise in elevation, the atmospheric pressure will lessen (usually) and the pressure of the float bowl will lessen as well. 7) Lesser ATM Pressure will equal lesser Delta P and equate to less fuel flow. 😎 IF your carb float bowl vent lines are vented ANYWHERE but into their own dedicated pressure chamber, your float bowl pressure WILL be at atmospheric pressure (or very close to it) 9) ANY and all Carbs will lessen flow as you raise in elevation. Meaning... ALL carbs have a built in elevation control simply as a result of its design and function. __________________________________________________ ___ OK.. Now that the "Basics" have been touched upon.. let's dive into what it truely takes to have control over elevation and temperature: 1) VERY SIMPLE--> Control Delta P and you can control the fuel flow! How do we control Delta P? You can control Delta P via altering engine side pressure or carb side pressure. Simple as that. It is possible to control either but controlling the carb side is WAY easier than controlling the engine side. How does one control the float bowl pressure? The only sure fire method to control the float bowl pressure is to have it vented into it own dedicated pressure chamber. This method has been used in the snowmobile world (huge elevation and temp changes) for many decades! They would connect ALL the float vent lines together and connect them to a dedicated pressure chamber that is controlled via the ECU and an Atmospheric Baro Sensor. Basically, they would sense the ATM pressure (baro sensor) and adjust this chamber volume based on this sensor. They also had a temp sensor that would add to the mix and adjust even further using the temp sensor's input. NOTE: this was a "programmed" function based on sensor inputs and the mechanical circuitry to implement it. It required dedicated electronic and mechanical circuitry. If ANY of these circuits failed (and they would occasionally) the jetting got "incorrect" in a hurry. Worked pretty well. We could run the SAME jets at 10,000ft that the sleds at sea level were running. Pretty impressive! So... How do you know if you have elevation and temperature control with your carb? Simple--> does it have a temp and baro sensor and a dedicated float bowl pressure chamber? IF it does NOT, then you do NOT have compensation outside of the built in mechanical compensation present with ANY carb.
  15. Need the bowl to a 2008 TTR 230 carburetor ASAP. Pls let me know or text me at 9038184854
  16. Im the "Latest Owner" of this bike, its a 2003 CR125R and its been a bit of a basket case. Im currently working on the spooge issue, and leaking fuel from the over flow. So, I have the FSM, and I pulled the carb apart to clean it, and check the float level and jetting. But... This Carb is NOT listed as one that is stock with the bike. The FSM lists the TMX-02 as the carb in the CR125R, this bike has a TMX-03A. ALL that I can find online says that its a carb for the CR250R of the same years, but that may be misleading. I don't want to screw with the jets needles, or air screw until I get the CORRECT info on this carb, or if I have to replace it with the appropriate (Or better) carb. I am hoping that I can jet it appropriately, cure my spooge, and get better throttle response and idle out of it. Any thoughts on this?
  17. Did a top end and right side crank seal put it all back together and the fuel pours out of carb on overflow tube when riding full throttle then stopping. Rebuilt the carb, pours constantly. Its been apart 12 times cleaning and checking float level amd i just dont know what to do
  18. Hey all, First post be gentle. Working on my friends kids bike. Need a replacement carb (prefer Mikuni) the internet seems to point me in many different directions. Has anyone done this and if so which carb is it? Thanks in advance. Jeff Burrows
  19. Hello all, My TTR125 has had a leaky carb ever since I bought the bike. It’s not just a drip, it’s a constant flow even after the bike is turned off. I have adjusted the float level numerous times at different settings and nothing does the trick! Could it be that adjusting the float isn’t enough, and I have to actually replace parts? Could I need a new float needle? Or which other parts should I try replacing first?
  20. I picked up a 2001 YZ that had the stock carb replaced with a Mikuni TM34 http://www.mikunipower.com/TM01.htm The stock jetting is vastly different from stock. The bike runs but I haven't had time to do any testing as of yet. I was hoping that someone has done this already and has some baseline jetting that worked for them.
  21. Hi, I already posted about this a few months ago. I wasn't sure what the best option was to upgrade my pretty stock DRZ400sm (only has aftermarket exhaust for now). I'm definitely going to be doing the 3x3 mod in the next few weeks but I'm still hesitating between buying a JD jet kit for the stock Mikuni carb or buying a used fcr39. I have 2 questions the answers of which should help me decide. On the local classified, there is currently a 2002 ktm 400 exc FCR39 for sale for much cheaper than the price of the kit on TT (also I'm in Europe so anything I buy on this website is going to be really expensive to ship my way). Does anyone know if the 2002 exc had FCRMX or the older model? Will it fit the DRZ? If I decided to pull the trigger on a used FCR39 (mx or not), are you guys aware of anyone doing a decent conversion kit? On TT I only see the entire kit including the carb, that I would obviously not need if I got a used one. Thanks!
  22. Hi , seem to be having issues with my Gas gas txt 280 stalling when turning left down hill in trials sections ( going slow) . Carb is clean and jetted well . Any ideas?
  23. Hello all, trying to get my 350 running right, but I’ve always had trouble with it since I bought it. It would always backfire on deceleration bad. It has some weird aftermarket muffler, that’s more like a straight pipe than a muffler. It still backfires bad and I can’t get it to idle well, no matter how I turn the pilot jet. It constantly misfires at low throttle too. In the upper end of the throttle it’s fine. I figured it’s a lean condition so I moved my needle all the way rich. That didn’t help at all. The exhaust pipe has no holes in it either. I’ve never checked compression or timing, but I’m thinking a carb issue. It’s a tm33, the carb found on the dirt model dr’s? I’m not sure what jet sizes are in it now, but I’m usually riding at 4000-6000 ft and ~70 degree days. Let me know what you think, thanks !
  24. I received the package with the rebuild parts for my 2004 KTM 250/350 EXC-G Racing four stroke. This is the bike is a 250 but has a 350 kit in it from the dealer. Before tearing the whole carb apart I wanted to see how dirty the bowl was and find out if there was anything obvious to notice in there. I have a question or two about what I found when I opened the bowl. The main jet was loose and laying in the little plastic cup that surrounds the jets. Not even attached to the needle. I obviously know that is a huge problem, but I don’t know if that is my whole problem that I was trying to solve. The problems I wanted to solve were as follows: the bike would fire right up and idle fine but when I went to use the throttle after it was warm enough to idle fine off choke it would stumble. This happens even when fully up to temp when trying to take off from a stop light. It stumbles so much it will die sometimes if I don’t really rev the heck out of it. When out on the road at full temp and at a constant throttle it would “surge” for lack of a better way to describe it. Almost like it was running out of fuel and then picking up fuel again at a rapid pace back and forth. While having the bike cruising down the road at that constant throttle, if I was to whack the throttle open heavily no more “surging” and had all the smooth power you’d want. So, I guess the question is do you think that the main jet being off and just giggling around in the little plastic cup could cause what I am describing? There is more info below that might help in making any recommendations. I also checked all the jet numbers while I was there. Main jet = 160 (I believe this is stock for a 250), Pilot jet = 50 (stock is 42 for a 250 from what I can tell but didn’t know if this larger pilot jet would be because of it now being a 350 or if that would even make sense to have the pilot jet that big compared to stock even with it being a 350), Starting Jet = 85 (which I believe to be stock for a 250). So, it looks like they kept it stock except for the pilot jet. Would this make sense, or should I get something more towards stock on the pilot jet? Any recommendations that you could make would be greatly appreciated.
  25. What's up guys looking for some info on jetting the mikuni tmx 38 for a 125 enduro, maybe get some tried an tested settings, at the moment the temps in my area are between 5 and 12 degrees Celsius and I ride from 0m to around 500m above sea level, I've ordered a jet block gasket kit as I still have the crappy original gasket so that should help, my current settings are 43-75 needle 480 main 30 pilot and 2 turns on air screw anyone know if this can be improved? Also have vforce4r reeds fmf fatty and shorty silencer Thanks in advance
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