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About Mark_Cantrell

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  1. Mark_Cantrell

    wheel torment

    I know this thread was dead but I just ran into the same thing. My rear spokes were almost all frozen, may 3 or 4 turned. I put WD-40 on the a few times, PBlaster on them a few times and tried to use some ViceGrips on a spoke and they still wouldn't budge. I ordered some Aero-Kroil and Sili-Kroil and put a drop on each nipple, three times, about 8 hours apart, and all but one freed up. I'll know about that one later. I had to old some spokes with ViceGrips and some I had to rock back and forth but it saved relacing the wheel. In a month or so I'll know if the ViceGrips did any damage. Mark
  2. Mark_Cantrell

    2007 Model Will Be Fuel Injected!

    Almost all EFI adjusts for temperature. There are three ways they can adjust for altitude and barometric: (1) use an absolute pressure sensor (like a MAP sensor on a car), (2) use a mass air flow sensor (like a hot wire or hot film MAF on a car), or (3) use an O2 sensor for feedback or closed loop control. A pressure sensor is somewhat likely, they're cheap and effective. A MAF sensor isn't, they're pricey, well over a hundred bucks, and require a low turbulence intake duct. An O2 sensor for feedback control is modestly costly, somewhat fragile (hanging over an inch off the exhaust header), and works best when running at steady throttle and what CRF450R does that? An often overlooked benefit of EFI is that it doesn't have a carb vent that dumps fuel when jostling or tipped over. A HUGE benefit in emitted HCs. I'm not a green, but I don't see the sense in dumping fuel just because you dropped the bike.
  3. Mark_Cantrell

    Bike smokes when started

    skipn8r is right. Along the same lines, black smoke is rich, blue smoke is oil. Blue smoke on (from first noticed symptom) startup after sitting overnight, startup after sitting briefly, on closing the throttle, and on idle is most like valve seals. Blue smoke when under heavy load, under load, and eventually just when running is oil past the rings. Someone earlier mentioned blowby. Blowby and oil consumption past the rings are related, both are caused by worn rings. Blowby is combustion gasses escaping from the combustion chamber into the crankcase. Oil consumption is oil smeared or sprayed on the cylinder walls and not getting wiped off by the rings getting into the combustion chamber. Normally, you take the head off to replace the seals. Not that big a deal on this bike. But you could probably use a pneumatic valve hold fitting (maybe $5) to hold the valves up while replacing them (just an air fitting with spark plug threads). Even just roll the cylinder to the top and the valves won't fall down. It's tight enough in the frame that it might be easier to pull the head.
  4. Mark_Cantrell

    Too rich, too lean, or just right? (pic included)

    The center ceramic is what you look at for mixture. Pure white is too lean, dark or black is too rich, a nice tan is just right. Yours looks OK. Pulling a plug out of a bike after a ride doesn't tell you squat. Find a jetting article but the gist is with a new or clean plug, find a long preferrably uphill straight. Start, ride WOT up the section and kill the engine and clutch before you let off the throttle. Then read the plug. That's only good for main jets. Mark Cantrell
  5. Mark_Cantrell

    Hesitation of full throttle - too rich or too lean?

    The main jet is the principal factor in mixture at wide open throttle. If it runs fine on open throttle but only hesitates when you first open the throttle, it is the accellerator pump instead of the main jet. There are several ways to combat this but changing the leak jet is the most common. I have a post on the YZ250F forum from a few years ago that describes how to adjust the leak jet. Mark Cantrell
  6. Mark_Cantrell

    Jetting Settings

    First, the bottom end means the throttle closed. Not the speed of the bike or the RPMs of the engine. If you lug up a hill at low RPM but full throttle, it is not the bottom end for jetting descriptions. The throttle closed to 1/8 throttle position is controlled primarily by the pilot circuit. The pilot circuit is the pilot jet and fine tuned (after selecting the right pilot jet) by the fuel screw (aka pilot screw) in the bottom front outside of the carb. For completeness, the midrange (throttle from 1/8 or so to just over 1/2 open) is controlled primarily by the needle taper and clip position. The full throttle or Wide Open Throttle (WOT) is controlled primarily by the main jet. For nitpickers, the throttle slide cutout is also a big factor in the throttle nearly closed position. This is how I envision it, smarter people may clarify this, but with the throttle closed, there is high intake manifold vacuum in the front (cylinder side) of the carb. This is because the cylinder trys to suck in air and the carb slide is mostly closed. The pilot circuit is in the front of the carb, you'll see this because the fuel screw and pilot jet are toward the front and when you clean the carb, squirting carb clearner in either comes out in front of the slide. So when the manifold vacuum is high (higher the more closed the throttle), the manifold vacuum pulls fuel up the pilot circuit and feeds the engine. As the throttle opens, the manifold vacuum drops and the pilot circuit supplies less fuel. In fact, as the throttle opens, two factors make the pilot circuit less of a factor, the manifold vacuum drops and the fuel coming through the main jet is very large compared to the fuel the pilot circuit flows. Most carbs have a butterfly valve that lets air through the carb as you open the throttle. The flat slide is more like a guillotine that opens as you open the throttle. There is a needle, maybe 4 inches long and tapered that slides down the flat slide and into the main jet. When the slide is closed, it either completely or almost completely blocks the main jet. As the throttle opens, the tapered needle pulls up out of the main jet allowing more and more fuel to be drawn into the carb. Both the needle and the slide open together. At some point, the needle is entirely out of the main jet and it doesn't get any larger with more throttle position. At this point to WOT, the main jet is the only control of the main circuit. The main circuit is made up of the main jet (in sizes from 130ish to 180ish), the size and shape of the needle, and the clip position of the needle. The needle is held in position by a circlip type clip at the top of the needle. The needle has several grooves around it that the clip can be placed in. Selecting a high clip position puts the needle lower in the main jet and makes it leaner. Selecting a low clip position moves the need up higher in the main jet and makes it richer. Remember the needle is tapered so moving it higher puts a thinner, less blocking part of the needle in the main jet. Moving the clip is the normal way to jet the midrange but needles with different tapers or shapes are available. Both the pilot jet and the main jet hang down into the fuel in the bowl of the carburetor. Vacuum draws the fuel up through the jets into the bore of the carb. For the pilot circuit, this vacuum is the manifold vacuum due to the engine sucking against a closed (or mostly closed) slide. For the main circuit (main jet and needle), the vacuum is venturi effect caused by the pressure drop of the air as it flows through the narrowest part of the intake tract. The more air that flows, the stronger the vacuum. Since the fuel has to be sucked up from the level of the fuel in the bowl to the bore of the carb, the lower the fuel level in the bowl the less that flows for any given vacuum so low level leans the mixture. A high level richens the mixture. The fuel level in the bowl is controlled by bending the tab on the float. There are two air jets, a pilot air jet and a main air jet. They supply emulsifying air for the pilot and main circuits. This sounds odd but a pure liquid stream of gas is hard to control because of surface tension, capillary action, and inertia. By mixing just a tiny amount of air, just enough that if you could see the fuel flowing in the jet, it would be maybe 1/8" of fuel, 1/8" of air, 1/8" of fuel etc. Like the flow through a straw as you suck up the last of a milkshake. The amount of air is neglible (1/2 by volume, maybe 1/100th by weight) so the air doesn't directly affect the mixture but it changes the weight of the stream delivered through the jet which affects the speed it comes out and the portion of air to gas that comes out. Again, this is just to make the fuel stream easier to control. Although it is useful for jetting, it was added to make the carb more predictable. There are three other circuits. The choke circuit is another jet that drops down into the fuel and is only operational when the choke is out. Richens for starting and cold. The hot start circuit just dilutes the mixture with additional air (pirate air for you auto techs) to lean it when hot starting. And the accelerator pump to enrich on accelleration. The accelerator pump is literally a little diaphram single stroke pump bolted onto the base of the carb that pumps gas into the carb when the throttle is opening. One the throttle stops turning, the pump stops pumping. The pump is designed so it can pump enough for any application and is then limited for the exact application by letting part of the pumped gas leak back into the bowl instead of all of it going into the carb bore. This is controlled by the leak jet. A bigger leak jet will reduce the accellerator pump volume and a smaller one will increase it. A fuel pump is required on a non CV carbs because the vacuum falls rapidly as the open slide lets in a rush of air to fill the manifold and then stagnates briefly until the engine starts rev'ing to pull in more. Hope that answered your question about the pilot and leak jet. Several years ago I wrote some long posts in the YZ250F/WR250F side called Jetting 101 and Accellerator Pump 101 that may still be there. I thought I was smarter then than I do now, so if someone can clarify or correct this, please do. Mark Cantrell p.s., just bought a 2005 CRF250 to replace an aging 2001 WR250F that is now for sale.
  7. James Dean, I've been away for a few years. Read some posts and have a question. In cars, the A/F ratio read with either a narrow or wide band sensor is all screwed up by either exhaust manifold leaks (air eduction) or by high overlap cams (raw air/fuel scavenged directly from intake to exhaust valves). Either would give a (perhaps dramatically) false lean. Any car mechanic can bore you about false leans. On my beat up '01 WR250F, the header never looked leak free at the head. And if I advanced the exhaust cam back to YZ250F specs (it's been a while, I used to change cam timing back and forth, hope I remember this right), I expect I had quite a bit of overlap. In fact, I'm sure that's common on dirt bikes. Cars with 50 state legal street cams have almost no overlap (or squish, or performance for that matter) but the O2 sensors work just dandy. Would an O2 sensor really do any good? With a 4 or 5 gas EGA, I could monitor rich with CO even with the raw air educted or scavenged, but with O2? And on a 2smoke, wouldn't scavenging be even worse? Also, I fooled with jetting forever with my bike. When I had it running snappy and not fouling, it was on the lean side. After running at high revs on a track with tons of corners (2nd gear short sprints) for about 30 minutes straight on a hot day, it froze the connecting rod to the wrist pin. Coincidence or self inflicted? I backed off the main and needle to richer and have a less than satisfactory condition with plugs that foul at idle. Any ideas? While I'm bending your ear, trying to divine some meaning from small voltage differences on a narrow band sensor seems iffy. I totally rebuilt my son's Volvo with CIS and tuned it with a narrowband sensor but I used a variant of the toggling rich/lean method all OBD-I and OBD-II cars use in closed loop. I introduced a vacuum leak (tee'ed off the booster vacuum line) with a needle valve back into the cabin. I started out rich for the engine's safety and for this strategy. Driving along, I would lean it out by cracking the valve slightly, watch the voltage go from ~.8V to ~.1V, then close off the valve until it would go rich. I would then lean the injector distributor (damn Bosch for peddling that damn CIS system) and try again. When it took almost no air to go from rich to lean, I plugged the tee and was done. This would be very easy to do between the carb and head, but I've never thought it was worth doing because of the exhaust header seal and scavenging (above). War story, but do you have any faith in narrow band sensors, regardless of what you think of O2 sensors on dirt bikes in general? Thanks, Mark Cantrell
  8. My degree is Civil Engineering at UT (yes, the orange one). Try this to help understand the issue. The shape or type of structure connecting the two endpoints and the fulcrum do not matter. The structure could go from the left of your diagram to the end of B back to the fulcrum and the results would be the same. The easiest was to visualize this is to extend the force vector (the direction of force) and find the shortest path to the fulcrum. Use the full force and that distance. For instance, if the force on the right were vertical, draw a line in that direction (vertical) and find the shortest (normal or perpindicular) line to the fulcrum. That is B on your diagram. The fact the endpoint were higher (parallel to the force) would be irrelevant. If the force were horizontal, the distance C would be used. If the force were at a 45 degree angle, down and to the right, you would draw a line through the endpoint at 45 degrees and find the right angle distance (or the shortest distance) to the fulcrum. How did you draw that picture, I would do a much better job with a drawing. Good luck, mwc
  9. For a motorcycle lift (or anything involving gravity which is all vertical) on both sides (you on one, motorcycle on other), it is the horizontal distance from the fulcrum that matters, any vertical distance is irrelevant. Machoman#618 got it right. The perpendicular distance from the force to the fulcrum. Or, as I stated, the shorted (normal or perpendicular) distance (sic) from the force. The perpendicular from a vertical force (gravity) is the horizontal. You do have an odd situation with your diagram, since you have a vertical component, the weight at that point will get close to the fulcrum faster (as you press down on the left) than if there were no veritcal component, therefore, you will have a lower force required as you depress the left side. You might even reach an over center condition in which the left lever would be depressed less than 90 degrees and the weight being lifted roll over to the left of the fulcrum. In that case, the bike would fall on the leg of the lifter. Be careful and put a stop in it. Good luck, mwc
  10. Mark_Cantrell

    Beware of Dealers' Service

    RCannon, I thought the shuttle blew up because of an O-ring that was temperature sensitive. If there's more to it than this, let us know. mwc
  11. Mark_Cantrell

    Need advice for '02 250F

    I'm dubious. First the head would strip at probably < 20ft.lbs. That is just a default tightness, ever notice there are probably 50 to 100 bolts with the same torque specs? I am more suspicious of the oil. The top of the head is oiled by the external oil line. Did you ever loosen the gallery bolt to see if oil was getting to the top of the head? Check the external oil line all three ways. When you put it back together, be sure to check the oil gallery bolt. Good luck, mwc
  12. Mark_Cantrell

    Watered out 250f

    Part it out? Unless used parts are worth more than I think, it would make more sense to fix it. The engine might be worth a few thousand but only if it ran. Assuming that is the only problem, the parts list is pretty small. I think Moose makes a bottom end gasket kit for the odds and ends little stuff. Moose kit (pure guess) $100 Prepressed crank and rod $270 Piston w/pin,clips, rings $114 Cylinder $217 That's about $700. You can save $110 if you press your own crankshaft. I have a press but have never tried it. If you need main bearings, it is another $92, I have a set you could get cheaper. There is a tiny chance you won't need a cylinder. Most people will give at least 10%, maybe 20% on a rebuild order like this. Give NorthCounty Yamaha a try. You could end up for under $500 bucks. There are few tools you need that aren't in your toolbox already (assuming reasonable set of wrenches/sockets/torque wrench). A clutch holder, a flywheel holder, a harmonic balancer puller for flywheel (on WR anyway) and if you have to press timing sprocket through left main. A 3/8ths 5mm allen for retorquing the case. If its your first time in, figure 20 hours. That should be conservative. Good luck, mwc
  13. Mark_Cantrell

    Beware of Dealers' Service

    I have just one word for you, sandpaper. There is no reason to buy shims that I am aware of. The valves always get tighter, not looser. 100 or even 220 and a micrometer, or vernier, dial, or digital caliper (any for less than the cost of 3 intake shims) and you're done. No trip to the dealer, no ordering and waiting, just done. Good luck, mwc
  14. Mark_Cantrell

    motor filled with sand

    free, Bear with me for a minute here. You don't even have to take the engine off the bike to get to everything that oil goes through. I think I'm right here. From the right side cover you can get to the clutch, the oil pump, the oil pipe to the left side, the hollow end (oil supply for lower connecting rod bearing) of the crankshaft, the right main, CB, transmission bearings, the various drive and driven gears, and the hollow (oil supply for gears) transmission shafts and the various oil supplies from the oil filter cavity. From the left side cover you can get to the left CB and crankshaft bearings and the sump (where the strainer for the oil pump scavenge side pickup is). You can reasonably flush the crankcase, through any of the available openings or through the cylinder opening. It will run out through the sump opening inside the left side cover and/or the oil pump opening inside the right side cover. You could reasonable flush it with a garden hose, then change the oil after 5 or 10 minutes. Only a few ounces would be left after simple draining, compressed air would reduce that even further. For sand (nonsoluble in anything), the volume, pressure, and velocity are worth more than any chemical. The only parts you wouldn't hold in your hand are the counterbalancer shaft (nothing there), the crank (you have access to the hollow end and without pressing it apart you wouldn't have access to any more of it), and the transmission shafts/forks (but you do have access to the hollow shafts of the transmission. You would have to still get the supply and return oil lines and the external oil gallery line to the head. This might only be a 3 or 4 hour job (head, cylinder, side covers, stator, clutch, and oil pump) instead of 12 or 15 hours (pull engine, everything above, plus split cases). Unless you pressed the crank apart so you could flush it better (and I'll bet you wouldn't anyway), I don't see the downside. You can still lay bike on left side, fill crankshaft hollow with oil, and blow it out lower connecting rod bearing with compressed air a couple dozen times to flush it. Just do that before flushing crankcase with water or whatever. I will get some heat here for suggesting water. I'll stand by it with the caveat that you do this in one sitting so oil flushes the water before it sits overnight. At worst, no worse than drowning the bike in clear water. At best, you can flush the he!! out of it, with more volume and more pressure than anything else. Sand doesn't dissolve, you have to move it. Oh well, I've been thinking about your problem at work and came up with that thought. Good luck, mwc
  15. Mark_Cantrell

    motor filled with sand after powdercoating

    Free, Sorry for the long post then, I mistook your tired of being in the bike for reluctance. That is quite a bit of sand in the filter recess. I just hope it all looks OK inside. Good luck, mwc