wild iguana

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About wild iguana

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  1. Should the starter jet size be decreased after installing a big bore kit due to increased vacuum from the larger piston? Bike in question here is an '05 yz250f which has been bored 3mm over to ~270cc. Stock starter jet is a 72.
  2. Cold starting procedure is turn on gas, pull choke, move starter lever to point of resistance, move back and then kick. No throttle. If its below 50F i twist throttle twice. Usually starts by 3rd kick. Valves where checked yesterday and are in spec. Tried the choke out of desparation. I tried the 1st 50 kicks with the hot start lever.
  3. This is an '05 yz250f. Won't restart worth a damn if I stall during a harescramble. Hot start button dosn't help, choke doesn't help. Kicking with throtttle wide open about 10 times (or until it catches) then kicking with throttle closed sometimes helps. Jetting is a 178Main, 40 Pilot, 1 1/2 on the screw, stock needle #4 posit, spark plug is fresh and has good spark, air cleaner fresh and valves checked and within spec, float level in carb is correct. Runs great with good throttle resp and no bog, starts fine cold. Any suggestions on what else to check or try? I'm at a loss on what to do next.
  4. I just ordered some aluminum bar to make the ICS spacers from. If anyone is interested I'll make them some while I'm at it. They will be done in early Feb as I will be out of town till end of Jan. PM me if interested, cost will be $10 + 2.50 for shipping.
  5. I'm not going to make Sumter this year, have to go out of town for work. It's not the Thumper kit. Picked up a cylinder that had been bored and plated 3mm over by Millenium Tech, a Vertex piston and some Cometic Gaskets. Same end result, just cost less.
  6. I finally got my 270 kit installed and rode the bike with it. It was a gorgeous global warming induced 70F January day if you can believe that! Anyways took it to the mx track. Few easy laps without hitting the jumps to break it in then let it cool down a couple times. Then took it out and got on it. Needed some air screw adjustment. Could definetly feel an improvement. To make a long story short, after break in, I experimented by going richer and leaner with the main jet just setting the air screw to optimal for each main. I was expecting better performace with the smaller main but in fact found that I got the best performance by going up one size to a 188 main 1 1/4 on the screw. It pulls hard all the way to the limiter and is strong and respnsive from down low. I'm really pleased. I can't really tell if it revs slower, i don't think it does, just hooks up better, more power and more useable power without losing the top end. The leaner jet let it rev freely but it had that hollow tinny sound and would'nt pull strong in the low to mid. It was unquestionably happier with the bigger main. I think there is more power/response to be had with some more jetting work, probably a more optimal needle. I suspect there may be more power to be had on the top end also, my stock pipe or the head may be too restrictive, but there is no loss of power. Now we'll see how it holds up. So far very, very pleased with the results and can't wait to get it off road in a hare scramble where I think it will really shine.
  7. I'm doing mainenance on my forks which are twin chamber Kayabas from an '05 yzf250. I'm having trouble getting the inner cartridges bled properly since the rod does not fully return after being compressed. I'm doing the followingto fill/bleed them.... 1- Vertical in vice, fill to 130mm from top, move rod up/down ~ 1in 30 times.Wait 10 min. 2- Insert cartridge. Tighten. move rod up/down ~ 1 in 30 times. Wait 10 min. 3- Put near horizontal in ice ~15 deg with holes in cartridge body at 6 & 12 o'clock. move rod up/down ~ 2in 30 times. 4- Very slowly push rod in fully. - Air escapes out of top hole about 1/2 way through stroke, excess oil comes out bottom of hole. 5- Check by pushing rod in fully. Action should be smooth and rod should fully extend. I have the problem on step 5 where the rod only comes back about 3/4 of the way. I've tried different variations on stroking the rod up/down slowly, vertically,horizontally etc. Still get same result. Is there another better way to bleed the forks? Is it really necessary for the rod to come backon its own? (I would think it is) (I should also mention that I forgot to backout the compression clicker during this, could this be a contributor or the culprit)
  8. How do you interpret those results? I assume speed is proportional to rpm? You snick it up to 5th gear and turn on the data acquisition from low to hi rpm? How do the drum rollers on the trailer dissapate energy and measure it? Way cool experiment!!!!
  9. Tell us about your dyno. Is it something you made or purchased? Any pics? Something you have access to through work or just renting time on one? I toyed with the idea of making one but it was beyond my discretionary budget after checking into it. I would test different main jet & needle sizes also.
  10. smcdonn Thanks for the jetting explanation!!! Thats the most plausible theory I've heard so far.
  11. Well after calling several of the shops which sell/specialize in the big bores for the yz250f I decided to give an 80mm (270) a try. Peterson is the only one proclaiming doom, two other shops claim no probs, unable to find individual report of problems with the 80mm. Have confirmed that no-one stands behind the 81mm bore any longer. I now have the parts in my possesion, a vertex piston and Millenium plated cylinder with the cutouts. I'll be curious to see how the jetting pans out, all the shops say richer 1-2 sizes on the main, lots of posts say it will need to be leaner. I guess I'll find out, seems no two bikes like exactly the same thing anyways. For kicks I'm going to take some cylinder bore measurements new and then ~40-50 hrs assuming its running good enough to make it that far. Hope to have together next week and ready (jetted) for race in mid Feb.
  12. I'll take the brake rotors if you part it out
  13. Could you expand on this? Not intuitively obvius to me. If fuel/air is at stoichiometric optimum and then cylinder size is increased it needs to be filled with more fuel/air at the optimim ratio. If the flow through the main jet is choked it will need to get bigger to keep up with the airflow. What would explain why it needs to get leaner?? 262 kit is only ~5% bigger so maybe it doesn't matter I also noticed that Wiseco specs different pistons for the '05/'06 application vs the '01-'04. Also some differences in compression ratio. Does anybody know what is different on the '05/'06 piston or is it just comp ratio diff between the years. What are the cut-outs in the '03 and newer for? To reduce the amount of backpressure the piston has to fight on the downstroke? Do the '05/'06 run a slightly lower CR and this is why? I've had an adult beverage and my math was never good.... thanks for correcting me, I meant to ask if people had problems with the 270 kit (80mm), I screwed up my post title. I took down my '05 after ~50hrs and the piston/cyl all checked within spec. I wish I had measured the wall outside diam like you did on your scrap cylinder. If the OD on an '02 cylinder is 85mm and it gets bored 3mm over to 80mm (270cc) wouldn't the wall thickness be 2.5mm? To your original point, still a significant reduction from the OEM 4mm. So far a few positive reports on the 3mm (270cc) overbore, no negative reports yet....the 262 kit sounds like a no-brainer, just have to figure if it isok to do on the cylinders with cutouts
  14. Was wondering if people who have tried going to an 80mm overbore (280 kit) have experienced any problems? Reading some of the posts, Rick Peterson seems emphatic that the bores will go out of round at this size after 20 hrs of use or so depending how hard pushed. Anybody experience this? How about rod/bearing failures from the increased piston weight? Overheating problems? Also, when going overbore, can a cylinder from an '04 or newer be used? These have the cutouts. I'm wondering if you can only go +2mm (262cc) on the cylinders with the cutouts or if the cylinders with the cutouts should not be bored at all and you need to get the older type cylinder if you want to bore it. I'm guessing that when they design the cylinder it has enough margin that you can go 2mm over without a problem and thats why so many outfits offer the 262 kit. Going 3mm might be pushing it but it would be nice if you could get away with it. Both Vertex & Wiseco have pistons available. Cost would be the same between the two. Also, what sort of jetting changes are required. I've had a few people tell me none but seems to me that if you up the displacement and make more power you need more fuel in there and a bigger main jet to deliver it. Wonder if this is why some are reporting loss of top end, if they are not jetted rich enough. Thanks for any feedback. I'm going to try this over the winter and need to decide 262/280. I don't want to lose the topend rush my '05 yzf250 has but would be happy if it got stronger everywhere.
  15. What kind of experience have folks had with these? I've been of the school of thought that a forged piston was superior to a cast. Vertex claims to be gravity cast while Wiseco are forged. http://www.vertexpistonsusa.com/whyvertex_000.html http://www.wiseco.com/default.aspx