Wilsons Sandbox

  Mark, thanks for asking. I'm playing with this in my spare time (work is the curse of the cycling class), learning a lot about the machine but not resolving the problem. Still have the miss. It first started on the freeway home from a very dusty, hot weather ride. The miss starts within two miles of when I start cruising at 4800-5000 rpm, whether I'm in 3d, 4th, or 5th. It's almost imperceptible at first, but after 4-5 miles it's bucking like a rodeo bull. Once it starts it keeps missing unless I back off to around 4000. Below that, it's smooth. NEW CLUE: the miss clears up completely when I accelerate, starts in when I level off, as long as I level off at 4500 or faster. Stuff I tried: New air filter (K&N, which I gather is not the best in dirt, but I had it handy). Switched to the gravity feed petcock. Checked fuel flow (one gallon in five minutes). Changed spark plug (the NGK Iridium one, thanks Fred); gap .033-.034". Checked plug wire resistor. Trimmed plug wire (just on general principles, it looked fine), dialectric-greased it. (I put the resistor back in first, then the little spring, then the screw; maybe it's supposed to be spring-resistor-screw, but the way I did it seems to work fine.) Replaced CDI unit (on a hunch, and because the consensus seems to be that the test drill in Clymer's is non-dispositive). Checked diode unit. Checked ignition coil. Checked exciter coil. Checked pickup coil. I bought another (used) diode unit ($10), but haven't put it in, having no reason to think that's really the problem. I guess I'll try that next though. One local mechanic thinks it's the valves. Though they're a tad overdue for adjustment, I'm getting none of the symptoms of too-tightness I've read about here. And though I can't recall his explanation well enough to repeat it, it didn't sound plausible at the time. I did a half-assed check of the carb, which looked fine, no clogged jets or other obvious problems. I don't know if it matters, but I got curious about what throttle positions I was in when the miss happens. At 5000 rpm in 5th I'm at 3/8 throttle, and at 5000 in 4th I'm at 5/16. I may pull the carb off and do a more thorough check, but the consensus seems to be that the problem's electrical. I bought a timing light and will check the timing but I don't see how that could be it. So the doctor tells the patient, "There's good news and bad news. The good news is, they've named a new disease after you...". Aagh! -James #ygrps-yiv-809357250 #ygrps-yiv-809357250yiv8145505875 #ygrps-yiv-809357250yiv8145505875 -- #ygrps-yiv-809357250yiv8145505875ygrp-mkp { border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;} #ygrps-yiv-809357250 #ygrps-yiv-809357250yiv8145505875 #ygrps-yiv-809357250yiv8145505875ygrp-mkp hr { border:1px solid #d8d8d8;} #ygrps-yiv-809357250 #ygrps-yiv-809357250yiv8145505875 #ygrps-yiv-809357250yiv8145505875ygrp-mkp #ygrps-yiv-809357250yiv8145505875hd { color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;} #ygrps-yiv-809357250 #ygrps-yiv-809357250yiv8145505875 #ygrps-yiv-809357250yiv8145505875ygrp-mkp #ygrps-yiv-809357250yiv8145505875ads { margin-bottom:10px;} #ygrps-yiv-809357250 #ygrps-yiv-809357250yiv8145505875 #ygrps-yiv-809357250yiv8145505875ygrp-mkp .ygrps-yiv-809357250yiv8145505875ad { padding:0 0;} #ygrps-yiv-809357250 #ygrps-yiv-809357250yiv8145505875 #ygrps-yiv-809357250yiv8145505875ygrp-mkp 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  Mark, thanks for asking. I'm playing with this in my spare time (work is the curse of the cycling class), learning a lot about the machine but not resolving the problem. Still have the miss. It first started on the freeway home from a very dusty, hot weather ride. The miss starts within two miles of when I start cruising at 4800-5000 rpm, whether I'm in 3d, 4th, or 5th. It's almost imperceptible at first, but after 4-5 miles it's bucking like a rodeo bull. Once it starts it keeps missing unless I back off to around 4000. Below that, it's smooth. NEW CLUE: the miss clears up completely when I accelerate, starts in when I level off, as long as I level off at 4500 or faster. Stuff I tried: New air filter (K&N, which I gather is not the best in dirt, but I had it handy). Switched to the gravity feed petcock. Checked fuel flow (one gallon in five minutes). Changed spark plug (the NGK Iridium one, thanks Fred); gap .033-.034". Checked plug wire resistor. Trimmed plug wire (just on general principles, it looked fine), dialectric-greased it. (I put the resistor back in first, then the little spring, then the screw; maybe it's supposed to be spring-resistor-screw, but the way I did it seems to work fine.) Replaced CDI unit (on a hunch, and because the consensus seems to be that the test drill in Clymer's is non-dispositive). Checked diode unit. Checked ignition coil. Checked exciter coil. Checked pickup coil. I bought another (used) diode unit ($10), but haven't put it in, having no reason to think that's really the problem. I guess I'll try that next though. One local mechanic thinks it's the valves. Though they're a tad overdue for adjustment, I'm getting none of the symptoms of too-tightness I've read about here. And though I can't recall his explanation well enough to repeat it, it didn't sound plausible at the time. I did a half-assed check of the carb, which looked fine, no clogged jets or other obvious problems. I don't know if it matters, but I got curious about what throttle positions I was in when the miss happens. At 5000 rpm in 5th I'm at 3/8 throttle, and at 5000 in 4th I'm at 5/16. I may pull the carb off and do a more thorough check, but the consensus seems to be that the problem's electrical. I bought a timing light and will check the timing but I don't see how that could be it. So the doctor tells the patient, "There's good news and bad news. The good news is, they've named a new disease after you...". Aagh! -James

  The new clue wherein the miss disappears at full throttle indicates to me that the ignition system is NOT the problem.  Rationale: it takes a higher voltage to jump the spark plug gap at wider throttle openings. Mike Martin Louisville, KY [b]From:[/b] "'James W. Flower' jwflower53@... [DSN_KLR650]" DSN_KLR650@yahoogroups.com [b]To:[/b] DSN_KLR650@yahoogroups.com [b]Cc:[/b] nomad59@... [b]Sent: Sunday, June 15, 2014 2:24 AM Subject:[/b] [DSN_KLR650] Re: HIGH RPM MISS .......... ANY UPDATES??? [b] [/b] [b] It first started on the freeway home from a very dusty, hot weather ride. The miss starts within two miles of when I start cruising at 4800-5000 rpm, whether I'm in 3d, 4th, or 5th. It's almost imperceptible at first, but after 4-5 miles it's bucking like a rodeo bull. Once it starts it keeps missing unless I back off to around 4000. Below that, it's smooth. NEW CLUE: the miss clears up completely when I accelerate, starts in when I level off, as long as I level off at 4500 or faster. [/b] [b] . [/b] [b] [/b] [b] [/b] [b] [/b] [b] [/b] [b] [/b] [b] [/b] [b] [/b]

  The new clue wherein the miss disappears at full throttle indicates to me that the ignition system is NOT the problem.  Rationale: it takes a higher voltage to jump the spark plug gap at wider throttle openings. Mike Martin Louisville, KY From: "'James W. Flower' jwflower53@... [DSN_KLR650]" DSN_KLR650@yahoogroups.com To: DSN_KLR650@yahoogroups.com Cc: nomad59@... Sent: Sunday, June 15, 2014 2:24 AM Subject: [DSN_KLR650] Re: HIGH RPM MISS .......... ANY UPDATES???  It first started on the freeway home from a very dusty, hot weather ride. The miss starts within two miles of when I start cruising at 4800-5000 rpm, whether I'm in 3d, 4th, or 5th. It's almost imperceptible at first, but after 4-5 miles it's bucking like a rodeo bull. Once it starts it keeps missing unless I back off to around 4000. Below that, it's smooth. NEW CLUE: the miss clears up completely when I accelerate, starts in when I level off, as long as I level off at 4500 or faster. .

  Full throttle enables more air to charge the cylinder and be compressed.  This makes the cylinder pressure higher when the spark plug is supposed to fire.  Higher cylinder pressure requires higher voltage across the spark plug gap to produce a spark. The temperatures of the ignition system components are just as hot when James opens his throttle wider, so the ignition system produces a good spark at these temps.  That's why I believe the ignition system is OK. Warmer temps could cause a rubber component to soften and allow an air leak to lean the mixture and produce a miss-fire.  The amount of air leakage would actually be reduced at larger throttle openings because the intake tract would then be closer to atmospheric pressure. Fuel flow capability checked out under idle conditions and is evidently good at wide open throttle. I think there's a mixture problem at part throttle. Mike Martin, Louisville, KY From: "RobertWichert robert@... [DSN_KLR650]" DSN_KLR650@yahoogroups.com To: DSN_KLR650@yahoogroups.com; Michael Martin mmartin36@...; James W. Flower jwflower53@... Sent: Sunday, June 15, 2014 10:21 AM Subject: Re: [DSN_KLR650] Re: HIGH RPM MISS .......... ANY UPDATES???   Well, it might take more spark to ignite a lean mixture and the full throttle mixture may be richer, but set that aside. If full throttle fixes it, then it's not fuel related is it?  I mean, there is no doubt that it takes more fuel at full throttle. Robert Wichert P.Eng. LEED AP BD&C HERS I/II CEPE CEA BPI CERTIFIED SF/MF GREEN POINT RATER +1 916 966 9060 FAX +1 916 966 9068 =============================================== On 6/15/2014 7:10 AM, Michael Martin mmartin36@... [DSN_KLR650] wrote:   The new clue wherein the miss disappears at full throttle indicates to me that the ignition system is NOT the problem.  Rationale: it takes a higher voltage to jump the spark plug gap at wider throttle openings. Mike Martin Louisville, KY From: "'James W. Flower' jwflower53@... [DSN_KLR650]" DSN_KLR650@yahoogroups.com To: DSN_KLR650@yahoogroups.com Cc: nomad59@... Sent: Sunday, June 15, 2014 2:24 AM Subject: [DSN_KLR650] Re: HIGH RPM MISS .......... ANY UPDATES???  It first started on the freeway home from a very dusty, hot weather ride. The miss starts within two miles of when I start cruising at 4800-5000 rpm, whether I'm in 3d, 4th, or 5th. It's almost imperceptible at first, but after 4-5 miles it's bucking like a rodeo bull. Once it starts it keeps missing unless I back off to around 4000. Below that, it's smooth. NEW CLUE: the miss clears up completely when I accelerate, starts in when I level off, as long as I level off at 4500 or faster. .

  I am obviously wrong about everything. I give up. Robert Wichert P.Eng. LEED AP BD&C HERS I/II CEPE CEA BPI CERTIFIED SF/MF GREEN POINT RATER +1 916 966 9060 FAX +1 916 966 9068 =============================================== On 6/15/2014 8:00 AM, Michael Martin mmartin36@... [DSN_KLR650] wrote:   Full throttle enables more air to charge the cylinder and be compressed.  This makes the cylinder pressure higher when the spark plug is supposed to fire.  Higher cylinder pressure requires higher voltage across the spark plug gap to produce a spark. The temperatures of the ignition system components are just as hot when James opens his throttle wider, so the ignition system produces a good spark at these temps.  That's why I believe the ignition system is OK. Warmer temps could cause a rubber component to soften and allow an air leak to lean the mixture and produce a miss-fire.  The amount of air leakage would actually be reduced at larger throttle openings because the intake tract would then be closer to atmospheric pressure. Fuel flow capability checked out under idle conditions and is evidently good at wide open throttle. I think there's a mixture problem at part throttle. Mike Martin, Louisville, KY From: "RobertWichert robert@... [DSN_KLR650]" DSN_KLR650@yahoogroups.com To: DSN_KLR650@yahoogroups.com; Michael Martin mmartin36@...; James W. Flower jwflower53@... Sent: Sunday, June 15, 2014 10:21 AM Subject: Re: [DSN_KLR650] Re: HIGH RPM MISS .......... ANY UPDATES???   Well, it might take more spark to ignite a lean mixture and the full throttle mixture may be richer, but set that aside. If full throttle fixes it, then it's not fuel related is it?  I mean, there is no doubt that it takes more fuel at full throttle. Robert Wichert P.Eng. LEED AP BD&C HERS I/II CEPE CEA BPI CERTIFIED SF/MF GREEN POINT RATER +1 916 966 9060 FAX +1 916 966 9068 =============================================== On 6/15/2014 7:10 AM, Michael Martin mmartin36@... [DSN_KLR650] wrote:   The new clue wherein the miss disappears at full throttle indicates to me that the ignition system is NOT the problem.  Rationale: it takes a higher voltage to jump the spark plug gap at wider throttle openings. Mike Martin Louisville, KY From: "'James W. Flower' jwflower53@... [DSN_KLR650]" DSN_KLR650@yahoogroups.com To: DSN_KLR650@yahoogroups.com Cc: nomad59@... Sent: Sunday, June 15, 2014 2:24 AM Subject: [DSN_KLR650] Re: HIGH RPM MISS .......... ANY UPDATES???  It first started on the freeway home from a very dusty, hot weather ride. The miss starts within two miles of when I start cruising at 4800-5000 rpm, whether I'm in 3d, 4th, or 5th. It's almost imperceptible at first, but after 4-5 miles it's bucking like a rodeo bull. Once it starts it keeps missing unless I back off to around 4000. Below that, it's smooth. NEW CLUE: the miss clears up completely when I accelerate, starts in when I level off, as long as I level off at 4500 or faster. .