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jrutkows

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About jrutkows

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    Colorado
  1. jrutkows

    stumble

    Yes, the level was above the idle knob. I know that it's not the way to set it but, but obviously the method in the manual is not working since the pin in the needle valve has no spring left. Once I get a new needle valve I'll see if going back to the 8mm setting does the trick. I'm riding at 8000ft, running a 162 main, second clip from the top of the needle, 40 pilot, and 60 leak jet. Right now the bike is running better than ever, actually picks the front tire up now. Which year yz needle would you recommend trying? Might order one when I order the new float needle.
  2. jrutkows

    stumble

    update: So I double checked the float height and it was at 8mm, per the book. Did not help. Pulled the plug an it looked pretty black, obviously running rich. Went for an other test lap and all of a sudden the bike was running great and then shortly after it died. Tried for 5 mins to get it started and then I realized that I forgot to turn the gas on. After some trial and error I could get the bike to run well by turning the gas off and riding for a short bit. I pulled the carb again and reset the float height to something like 15mm and now the bike is running awesome, more power than it has ever had. When setting the height the first time I notice than the spring for the pin in the needle valve seemed really weak. If I tilted the carb much more than horizontal the float would compress the pin all the way. I remember in the past being able to tilt the carb almost 45 degrees before the pin would compress? Seems like I need a new needle valve? Has this happened to anyone else? Why would the spring get weak?
  3. jrutkows

    stumble

    There was a bog it is now it is gone, replaced with a stumble or rough running at partial throttle. The bog was not really relevant other than to say I had the carb apart and cleaned everything since the diaphragm disintegrated, and I might have screwed up the float adjustment. The bike was running fine in the summer, sat a good long while, and then I did a top end. I have not changed any jet sizes or needle/clip position. Everything is as it was when the bike was running well. Seems like a fuel issue to me, so what could it be? I've adjusted the float per the manual before and it's difficult to get an accurate measurement at the point where that tab is just contacting the pin in the float needle, seems like someone should be able to tell me if the level is way to high from the picture that I posted?
  4. jrutkows

    stumble

    If I hold the throtle open 1/4-1/8 and ride down the road for a bit it is still stumbling, not during the AP squirt. I have an o-ring on the AP linkage and the the squirt was good and strong, spent a bit of time flushing out the nozzle and check ball passages, made sure it was working well. Does the float height look right? Float got pushed on when I had the float bowl off, so I re-set it but might have done it wrong, level seems high?
  5. jrutkows

    stumble

    Just finished a new top end, (rings and piston and YZ cams to get auto decomp) on my 01 WR250f, bike had a terrible bog so after tearing down the carb I found the AP diaphragm was coming apart. Got that replaced along with a new pilot jet and now there is a bad stumble. The bike is running real strong at WOT, much better than before the topend so I don't think there is any mechanical issue. The jetting before was good but it seems like it's running rich. I used to the drain line from the float bowl to seem where the float height is and it seems really high to me. It was repeatable with the following procedure 1) turn gas off 2) open drain bolt and drain float bowl 3) lift end of drain line above carb 4) slowly turn on gas I though it should be level with the top of the float bowl? Is my float way off?
  6. I have a 2001 WR250, I put in new rings & piston and since I had it apart a switch to a YZ auto-decomp cam the other night. Got it started, took a few hot-laps, but now there is an off-idle bog? I put a fresh o-ring on the AP linkage, and a new pilot jet, but didn't have time to check much else. My next step is to pull the carb and check the AP for any blockage, but any other thoughts on things to check while it's apart? After the bog, it seems to pull strong, so it's running well. I've never done the cam timing before but assume that if I got it wrong it run awful? The bike was jetted fine before the cam switch switch (maybe a bit lean for cold temps), but seem like it's really lean now? Is is possible that the jetting would change with switching to the YZ exhuast cam? I wouldn't think so, and I'm reluctant to change the jetting quite yet. Any thoughts would be welcome, as I'll tear into this in a few days , thanks everybody, j-
  7. FYI: steel will contract ~7 ppm/degree F and aluminum ~12ppm/degree F, (ppm = parts per million)
  8. "So if you change the the pipe eg: yz pipe, would you go up in jet size with the main? but just leave the pilot? also i just really noticed(just had a ride) when the engine is hot it doesn't like to keep idling" go to the top of the forum and find the sticky about adjusting your fuel screw (pilot circut). You need to learn to do this or you will always be unhappy. good luck, j-
  9. Here is the way I think about it: The piston goes down, intake valve is open and that creates a vacuum at the carb. This is why the engine sucks in air and gas. You open the throttle and in comes more air and gas. To first order, the vacum your engine makes has nothing to do with your exhaust because most of the time that the sucking is happneing, the exhuast valve is closed. Now, stricktly speaking there is a lot of fluid dynamics going on, some valve overlap, and your exhuast could have a small affect on the amount of vacuum created. Changes such as elevation and temp create a much bigger difference than changes to your exhuast. I think this this explains why minor to moderate exhuast changes have little to do with your jetting. Now, if you changed your cams, or other parts of your engine you could imaging that you might need to re-jet because these would effect the vacuum generated durring the intake stroke.
  10. jrutkows

    GYTR and JD jet question

    Assuming you bike runs well now, unless you are dropping 5000ft+ in altitude and going from summer to winter riding, there is no justification for switching 2 jet sizes. My guess is that you are too rich already, I have an 07 set up like yours and it runs perfect with a 42 pilot and 155 main at ~6000ft (you are suggesting that you need to be 7 jet sizes larger on the main?, make no sense to me). You paid a ton of money for the the JD kit, the jets are cheap. You really paid for his printout with proper jet size for temp and elevation. Why did you pay all that money if you are going to ignore it? What does the sheet say? Every bike is different, and the only way to properly jet is through slow tedious comparisons of jet sizes vs. performance. Most people do not have the time or patience it takes to do this right, which is why the JD kit is so popular. He has done the experiment for you, and sold you the result. I'm no jetting expert, but my experience is that when you go one size too lean the the change is really noticable, when you go one size too rich it's harder to tell a difference. If you want to experiment, then drop a jet size and see what happens, if you can't notice much then there is no reason at all to go bigger. If the bike runs like @#$%^ then you might consider going up one size. good luck, j-
  11. jrutkows

    GYTR and JD jet question

    The only thing different about JD is the needle. All other jets are the same (i.e. the 160 main in his kit is no different that one you would order through yamaha), though I belive because of needle design you wind up using a size or two larger main jet that you might otherwise. The leak jet affects the AP squirt volume, I don't think the JD kit came with a different leak jet. The leak jet has a little more to do with how you ride than anything. There is no magic to jetting, if it's running well there is no reason to change out jets. Do a search if you want to fine tune your AP, there is a ton of stuff on here to help.
  12. Striclty speaking your carb has different circuts that function at different throttle positions, with some degree of overlap. The numbers correspond to the size of the opening in the jets. The Main jet affects wide open throttle, and the pilot jet along with the fuel screw affect the idle circut (pilot circut). The needle affects mid-throttle mixture. When you crank the thottle open rapidly, the accelorator pump is in play. It's been my perception and experience that these different circuts of the carb seem to overlap more when things are way out of wack. In other words if you have a main jet that is 5 sizes too big then you might also get a bike that idles funny and has less power at WOT, so then if you start changing the pilot circut to compensate you can lost in a hurry. My jetting was way off from the PO, and this made it hard to figure out exactly what was going on. http://www.zrxoa.org...jetting-diagram The hesitation or bog that you describe sounds like something in the carb, (i.e. either jetting or the accelerator pump). You need to be patient and come up with a systematic way to isolate and evaluate each circut so that you don't make something that is already fine worse, like the original poster had done by going huge on the main jet size. good luck, j-
  13. jrutkows

    07 yz250f wont start been sitting up

    no, probably not, but you never know. If it were me and I wasn't in a hurry, I'd do it right, I'd pull the carb, swap the pilot jet for new one, clean and check everything. Sometime I am in a hurry, I just want to get out and ride, and I'm just saying that I've used a squirt of carb cleaner and gotten my bikes to start after sitting for a long time. Sometimes they run fine once I get the started and sometimes they don't. A few squirts of carb cleaner costs almost nothing, takes only a minute, and give me some idea where I'm at. Who knows, maybe your buddy remembered to shut the gas off and the carb really isn't in that bad of shape. Maybe it's horrible and needs to be totally dismantled and thoroughly cleaned, really hard to say. You said you didn't have any experience with carb work and that the bike did not belong to you. You need to decide for yourself how rigorous you want to be and how much effort you want to put into your buddy's bike. Just offering options to you. Search the forum and you will find a detailed procedure for setting the fuel screw, it's not that hard and makes a huge difference on these bikes. good luck, j-
  14. jrutkows

    07 yz250f wont start been sitting up

    There is a 17mm cap on the bottom of the float bowl, if you don't want to remove the Carb and float bowl, you can losen and rotate the carb and you will be able to get to the pilot and main jet with the cap off, pilot jet comes out with a straight screwdriver. If you take out the carb and take off the float bowl I think you need to remove the fuel screw (I could be remebering wrong). If you remove the fuel screw count the number of turns to seat it before you take it out so you have a good starting adjustment. Also, be sure not to lose the washer, spring, and o-ring that are in there. One thing you might try before you take the carb apart is spay a bit of carb cleaner in the airbox/filter. If my 250 has been sitting for months this will let if fire right up. I don't quite get why since you would think simply twisting the thottle a few times would squirt in some gas a do the the trick, but it doesn't. The carb cleaner startup has worked for my 01 250f and my 07 450f without fail. Once you get is started and running, the pilot circut will affect how well it starts up but also to some degree the off idle performance. You will need adjust the fuel screw to fine tune everything. good luck. j-
  15. jrutkows

    AP tuning for altitude

    Bike runs good, but excessive black on the tailpipe means it's running rich at some point, somewhere. This may not mean that the jetting is wrong, or that it can even be fixed given the constraints of carburation, but it's valid information. My truck is fuel injected and does not exhibit this issue. Under hard acceleration, it seems that it would be difficult or impossible without some very special tools to know if you are slightly rich or lean. You could be both during the time the AP is in play depending on the initial intensity and duration of the squirt. I have to believe that the AP comes dialed for sea level, so it only stands to reason that it needs tweaking for high altitude, leaning out. Now I have a 60 leak jet and have tweaked the timing, no bog, pulls hard. So the initial intensity of the squirt is probably right but what if the duration is still too long? I realize that at some point you go with good enough, but at the time of my original post I hadn't yet spent any time tweaking anything so was looking for any experience that people had. I'm happy with it now, runs fine, could always be better though.
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