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About sbest

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    TT Gold Member

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  • Location
    Nova Scotia
  • Interests
    KTM 125-380, Yamaha Blaster, CRF100, Husaberg 450, Yamaha DT200

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  1. The single body math and vector diagrams go out the window when you put an intelligent reactive suspension (muscle and bone) between the COG of the bike and the COG of the body incarnate. The muscle and bone can apply force, mass and acceleration in many ways to create an apparent shift of COG. Have a look at trials riding.
  2. sbest

    Yz250 Engine Questions

    Hey Shown, I ride a KTM 125 on the street and am very familiar with motors, at least KTM anyway. As JoeRC51 mentioned, there are no marks on your piston so those marks on the head are from a previous engine bearing destruction. Not from detonation, although detonation can cause a bearing to grenade. You can see where the black carbon deposits on the piston are "washed" clean. This is from a rich, possibly over rich fuel mixture. It is quite possible to have one jet rich and another too lean. Since the main is used at full power, it is essential for it to not be too lean. Read up on "Plug Chop" for the simplest and most exact way to jet the main. It will cost you a few (2-4?) spark plugs but you will know for certain if your full power jetting is right. On the road we run mainly on the pilot jet and needle. A 52 pilot sounds rich to me also, I am running 42 or 45 in most of my 38/39PKW 2 strokes. A lean pilot or needle will seize a 2 stroke just as well as a main will, so read up on jetting these. 160psi compression does not sound to bad. It would be on the low side if you were racing but for trail or street it is fine. I actually cut my head for lower compression so I can run pump 87 octane fuel if I have to, since that is often all backwoods stations carry. As for what piston, I always measure a worn bore instead of trusting the A/B/C/D stamp. 32:1 oil mix is fine. I ran 50:1 for a while and experienced excessive bore wear. I am a believer in 40:1 or even better 32:1 oil mix now, even with the "50:1" synthetics. So, where did the oil spooge on the pipe and plug come from? Both had to be loose to leak oil. A new properly tightened plug and an "O"ring and good springs should seal the pipe if it is not bent. Too rich a fuel mixture (jetting) is a worse problem for spooge (oil drip) than an overly rich oil ratio, believe it or not. The smoke might be from your right side crank seal leaking under high vacuum conditions (closed throttle coast) and sucking oil out of the gearbox. The seals often harden up or wear out after 10 years. Sometimes when running at low rpm the bottom end will load up with settled oil and smoke profusely when you next open the throttle. This is normal, not a worry. Good luck. Any guy who likes 63 Pontiac Catalinas or 73 Novas can figure out a 2 stroke, and is the sorta guy I'd share a few beers with.
  3. sbest

    Should I change tire?

    You really gotta get out riding more often. I thought so. I take rides longer than 10 hours. In the real life, we ride them until they are done. Winter and Springtime require a lot of tread for snow and mud, so new tires go on. By Summertime the tread is half wore but the ground is harder so we suffer through. Rear treads can be sharpened up with a knife, hacksaw or cutting disk by cutting off the front edge. The front tire wears the top of the blocks tapered, so flipping it is the better answer. As far as back braking with a flipped rear, it is a non-issue. They still brake fine. Here is a siped and screw studded tire still being used for wet woods winter riding. It has actually been flipped yet again looking at the lay of the sipes. This is not going to throw loam like a new one, but it will see a lot more than 10 hours use before it is finished. Ride it!
  4. sbest

    Where the dr do I start

    RIDE, just ride! Forget all the mechanical modifibations, just ride.
  5. sbest

    Should I change tire?

    Sweet cheeses, that tire looks like a week's use in my woods. If you've got the money to swap'er out, fill yer boots! I run them until they look like that, cut a sharp edge on them for a big run, then cut them again when I need to. For the front flipping it over seems to work the best. For a while I had a Husaberg that ran the opposite side chain so I could swap rear rims between the KTMs and the Husa. When the tread is down to 6mm or less I've often siped them for hard and wet stuff. How many hours have you got on that tire? I'm guessing not many?
  6. Man, i hit it hard today, gonna sleep great. Last night i got 9 hours solid. Endorphins rule! Ever try snu-snu?
  7. sbest

    2 stroke oil and ratio trail riding

    Pretty darned good information here. Stick with it and you won't go wrong concerning use and ratios. Willie, good insight on the effect of air filters, thanks!
  8. Yeah, epoxy and most glues do not stick to the tank material. I don't know P-Tex, I use polyurethane like "Gorrilla Glue" or LePage PL Premium construction adhesive.
  9. Sheesh, 300 lbs is light? Dang! KTM 250F? What is the oil change interval on that? Is it long enough for me to do a 3 day weekend of riding? Some of the lighter bikes are nice, but I'd really like to do at least 60mph to keep up with secondary highway traffic. This is my answer, KTM 125 EXC: I've kind of messed it up with some oversized fuel tanks and a lead/acid battery and tools in the toolbag so that fueled up weight is about 255 lbs. For this summer I have the EXC tank back on and a lithium battery with full fueled weight being about 235 lbs. With the 45 T rear sprocket top speed is about 75-80 mph with 65 mph easily sustainable for long distances. I often take it on 100 mile trips, usually taking secondary roads, but not afraid of the interstate type highways when I must. Maintenance is a couple 1 litre oil changes of ATF a year, or reasonably after any deep fording, tighten chain and spokes once a year and pads and plug every couple of years. Fuel consumption is about 55mpg on the highway so about 125 mile range on the stock tank. This is not a good bike for 2 up riding or extended highway riding (although I've done it), and is not completely town friendly. Mixing fuel is quite easy once you get used to it. The 125 has good torque and sufficient power. A 200 KTM has loads of power but may sacrifice rpm range. The earlier KTM 250/300 do not have the wide gear spread of the 125/200 and may not have the flexibility, and well as an absolute overkill on power. I always found the KTM 125 had plenty of power when it came to dual sports. If there is a better (lighter/highway capable) dual sport bike, I want to know about it! I bought a KTM Duke 390 for 2 up highway cruising with some limited off-road capability.
  10. I see the foreign tourists in Banff using "bear-bells" to scare away the bears. Funny thing, when I show up they stop ringing the bells and huddle closer to the "big rugged Canadian" like I got some sort of superpower to keep bears away. An important thing I am told is to know what sort of bear you are dealing with. The black bear is more shy and is easily identified by its droppings that typically contain berries, small animal bones and fur. The more ferocious Grizzly bear is easily identified by droppings that contain bells, sneakers, hiking boots, and often smells of pepper... Now some useful information. Most flare guns are available with Bear-Bangers or "screamers". These are a flare shell that makes a loud bang on firing and lobs a round that explodes a few yards away or screams as it is fired. It is usually enough to deter a bear, although I am sure the odd flare gun turns up in Grizzly droppings.
  11. Ha! I've done it too. That is where the block under the skidplate and blocking the wheels will help. I haul my quad inside my van on occasion. Never a problem with fuel smell as long as the petcock and needle valve are in working order.
  12. sbest

    1989 yz250 resurrection

    Yeah, it doesn't have to be a perfect restoration. It's your bike, do as you like. My first bike was a 1967 so I don't think of a 1989 as an antique, in fact I remember drooling over them in the showroom! Good luck.
  13. sbest

    1989 yz250 resurrection

    I could give you a bunch of reasons why it is a better idea to start with a running bike, but I too have a weak spot for basket cases. Many times I could have bought a running bike for what I paid for the missing/worn parts. There is a satisfaction I get from putting a box of parts together into a living entity. Like building a model kit, only it is full sized and I can ride it. Dr Frankenstein would understand. Parting these out would seem like sacrilege, when you have the ability to resurrect them.
  14. This looks like a pretty solid setup but you are still relying on the bike suspension for the compression force to hold the bike in place. This still stresses the suspension and leaves the bike liable to bounce during bumps. If the tires move sideways on the bed, the bike will still fall over. The grooves in the bed make it not likely except in the most extreme cases. Note the other examples have the wheels in a trough, good idea. Another good idea is to have a block under the bike just large enough to side under the relaxed suspension, then compress the bike down onto the block. This saves the suspension so the bike can be left connected for months if need be without hurting the springs, or bouncing during transport. I like holding by the pegs as you are doing here. It is quick, strong, well leveraged and uses short straps or chains with little stretch. I prefer to use one fixed chain and one short HD ratchet strap to apply tension onto a block under the skidplate, and of course, to have the wheels in a trough.
  15. sbest

    Help with new tires for drz400s

    I've used enduro bikes for daily transport for many years. XL500, XT600, KTM 125 EXC, Husaberg 450. The DRZ 400 is one of the better long distance commuters. Enduros are wonderful around the city. Not so great on the highway but I feel the DRZ400 is a better highway commuter than any of the bikes I just mentioned. As for SM tires, I have run on 21"/18" tires for many years. A wild variety of tires are available at all price points. The 17" tires I am running on my Duke are bloody expensive in all types. I also notice the lower 17" tired bike cannot clear curbs and other obstacles like the 21"/18" tired bikes. As you can see, I am using the Duke out of its element, but with good adventure/touring tires it will handle it, but these 17" tires cost $200 each, as opposed to $120 each for 21"/18" tires. Stick with your stock rims. Yes, the big rotors do give the brakes more leverage. Are you racing, or looking to commute? The stock DRZ400 brakes will do fine for commuting. These adventure/touring Kendas have been my go-to for many years as a street tire because they last a long, long time. Everything is a compromise. Long wearing means a harder rubber that does not grip pavement or wet logs as good as softer compounds. I've often siped the big tread blocks to get better grip in wet conditions. While not the best in muddy conditions, they certainly will let me explore off-road and will corner amazingly on pavement. While the SM look is stylish, it is expensive, and doesn't accomplish much that cannot be done on stock rims, plus they give up the "go anywhere" utility of an enduro.