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jg97986

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About jg97986

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    New Hampshire
  1. jg97986

    DR350 HELP PLEASE!! Continued

    Turns out I had two problems. I solved the issue of loss of power & chronic backfires - The piston & rings were badly worn. So bad in fact, that when I took the cylinder off I noticed scorch marks on the right side of the crank (where the explosion was getting past the piston). The cylinder tollerance was fine. So I honed it, and replaced the piston & rings. Now that problem's gone. A leak down test would have easily/quickly detected this (but I don't have the equipment). I did a compression test, and it was very low (about 60psi). That's what lead me to remove the cylinder. However, I'm never totally convinced by compression tests on these 4 strokes with automatic decompression systems. After replacing the piston & rings I still have lower than expected compression (about 80psi). I suspect this is the auto decompression system (there's a little cam on the exhaust cam that keeps the exhaust valve slightly open at very low revs). I think the lesson is that if you have loss of power & misfires, get it to a tech. for a leak down test. Shouldn't cost much (30 mins labor). The other problem (that I still have) is a carburetion issue. And this was complicating/confusing the diagnosis of the above issue. I have slight hesitation at 1/4-1/2 throttle position. Really noticable if I crank the throttle open quickly. Not too bad though (I just spent 6 days having a great time riding in Moab). I have an after market muffler, K&N filter & opened up air-box. I need to some needle height adjustment & maybe some re-jetting.
  2. I have a '97 Suzuki DR350 (off road) with a misfire problem (it was bought used with the problem, so I don't know what happened to cause the issue). It starts fine, idles fine, revs fine and pulls fine up to about 4000 rpm. But just doesn't have any power past that. At which point the exhaust note is really load crack/popping noise, and I get backfires & flames out end of exhaust (I have a straight through aftermarket muffler). It's like I'm getting very retarded ignition (igniting the gas as it's on it's way OUT of the cylinder) or the exhaust valve timing is out of whack. I don't think it's valves since I've checked the alignment & clearances, they seem to move freely enough & there's no adverse noises from the top end. Plus everything is fine up to about 4000 rpm (if it were valves I'd expect problems throughout the range). Plus If I hold the throttle open on a long straight, I get short periods (a second or two) where it picks up & runs OK. Then back to the lack of power & backfires. I also put an ignition strobe light on it and the light seems to get very erratic past 4000 rpm when the problem occurs. I know it's not carburation, ignition coil, plug, or CDI as I've replaced all these with ones from a working bike and I still have exactly the same problem. So I suspect a faulty pickup coil (there's 2 on the '97 off road). Trouble is I have the stator off, I've checked the resistance of everything and it's all fine!! Both pickups are around 490 ohms (350-700 is the spec. for the '97) and the power source coil is 470 ohms (spec. is 350-650). So I'm reluctant to replace the coils and/or stator if they all test OK (although I suspect one could still be intermittently faulty & test OK). Is it possible one of the pickups is faulty but still showing the correct resistance? I'd be very interested to know opinions on pickup vs. valves (before I throw anymore money at my bike). Thanks.
  3. jg97986

    '97 DR350 (off road) misfire

    I have a '97 DR350 (off road) with a misfire problem (it was bought used with the problem, so I don't know what happened to cause the issue). It starts fine, idles fine, revs fine and pulls fine up to about 4000 rpm. But just doesn't have any power past that. At which point the exhaust note is really load crack/popping noise, and I get backfires & flames out end of exhaust (I have a straight through aftermarket muffler). It's like I'm getting very retarded ignition (igniting the gas as it's on it's way OUT of the cylinder) or the exhaust valve timing is out of whack. I don't think it's valves since I've checked the alignment & clearances, they seem to move freely enough & there's no adverse noises from the top end. Plus everything is fine up to about 4000 rpm (if it were valves I'd expect problems throughout the range). Plus If I hold the throttle open on a long straight, I get short periods (a second or two) where it picks up & runs OK. Then back to the lack of power & backfires. I also put an ignition strobe light on it and the light seems to get very erratic past 4000 rpm when the problem occurs. I know it's not carburation, ignition coil, plug, or CDI as I've replaced all these with ones from a working bike and I still have exactly the same problem. So I suspect a faulty pickup coil (there's 2 on the '97 off road). Trouble is I have the stator off, I've checked the resistance of everything and it's all fine!! Both pickups are around 490 ohms (350-700 is the spec. for the '97) and the power source coil is 470 ohms (spec. is 350-650). So I'm reluctant to replace the coils and/or stator if they all test OK (although I suspect one could still be intermittently faulty & test OK). Is it possible one of the pickups is faulty but still showing the correct resistance? I'd be very interested to know opinions on pickup vs. valves (before I throw anymore money at my bike). Thanks.
  4. jg97986

    DR350 HELP PLEASE!! Continued

    I have a '97 DR350 with exactly the same problem (it was bought used with this problem, so I don't know what happened to cause the issue). It starts fine, idles fine, revs fine and pulls fine up to about 4000 rpm. But just doesn't have any power past that. At which point the exhaust note is really load crack/popping noise, and I get backfires & flames out end of exhaust (I have a straight through aftermarkey muffler). It's like I'm getting very retarded ignition (igniting the gas as it's on it's way OUT of the cylinder) or the exhaust valve timing is out of whack. I don't think it's valves since I've checked the alignment & clearances, they seem to move freely enough & there's no adverse noises from the top end. Plus everything is fine up to about 4000 rpm (if it were valves I'd expect problems throughout the range). Plus If I hold the throttle open on a long straight, I get short periods (a second or two) where it picks up & runs OK. Then back to the lack of power & backfires. I also put an ignition strobe light on it and the light seems to get very erratic past 4000 rpm when the problem occurs. I know it's not carburation, ignition coil, plug, or CDI as I've replaced all these with ones from a working bike and I still have exactly the same problem. So I suspect a faulty pickup coil (there's 2 on the '97). Trouble is I have the stator off, and I've checked the resistance of everything. It's all fine!! Both pickups are around 490 ohms (350-700 is the spec. for the '97) and the power source coil is 470 ohms (spec. is 350-650). So I'm reluctant to replace the coils and/or stator if they all test OK (although I suspect one could still be intermittently faulty & test OK). Did you ever solve this issue? I'm very interested to know if it was the pickup or valves (before I throw anymore money at my bike). Thanks.
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