Chuck, there's 2 theories here, 1, is that it detonated which means it got hot enough to melt the plug, or 2, a possible ignition problem that may have "welded" the electrode to ground, and after what John just said it's looking more like ignition. "Findin TDC can only really be don properly with a long travel dial indicator"? Geese, I guess all the motors I've degreed cams in were all wrong! Chuck, sorry but another engine theory refresher. The least accurate way to find TDC is how you described, there's a thing called dwell with crankshaft revolution and is related to the rod length ratio. What happens at TDC is that the piston stops it's up/down movement as the rod swings over the top of the crank for a couple of degrees, the longer the rod, the more the degrees. So the best way is to use a piston stop and a degree wheel, you'll be off several degrees every time with the dial indicator.. CR
Chuck Voboril <[EMAIL PROTECTED]> wrote: Chris, I'll try to answer your questions ...except for the welder-this may be more like heating a part to melting in an oven and seeing which way it flows. But I could be wrong. The piston moving creates quite a breeze, I suppose :-> This is a mag fired ignition, not battery. It has a stator coil to charge up the CDI and another stator coil to trigger the discharge. 4 moving magnets. 2 for each cylinder, one of each pair charging, the following one triggering. ...and there is something diffferent from one side to the other before this happened-the bad side has(had?) higher compression. Last, the only way or him to check timing left vs right is to make 2 marks on the clutch after finding TDC for both cylinders. Findin gTDC can only realy be don eproperly with a long traveldial micrometer. At that point, he should also know if one crank throw is off or not too. Chuck >From: Chris Reinhardt >Reply-To: [email protected] >To: [email protected] >Subject: Re: [F500] Help I don't know what to do anymore >Date: Wed, 27 Sep 2006 20:07:19 -0700 (PDT) > > Hmm, the gravity thing... Chuck I'm a welder, and cerified in overhead, >if your theory was correct, I could only weld with the electrode pointing >down... You can weld an electrode at any attitude, if it can jump a spark, >have enough current, it can weld. > Well the loose rod will tell the story, but if not I would shotgun the >whole ignition system. Hey just a thought, anyway that an engine builder >down the road stuffed a longer rod on 1 side? If it were a factory f$%# >up, like .020" or so, you probably wouldn't know by the looks of it... > I assume these are battery fired ignitions and not mag? Another theory >I've seen in the old Triumph bikes. If the voltage to the coils goes A/C >it will drive the spark timing nuts. I know, why is it just the one >cylinder, I could see a whole barage of bad wiring. > There's obviously something different from the good cylinder to bad, >either mechanical or electrical. > > John, keep it simple. Check the cylinder/piston for damage, check >compression on both cylinders, when you get it running again, check timing >left to right. > > CR > >Chuck Voboril wrote: > John said: > >"I have seen electrodes bent/welded, and severely burnt." > >So, the question now is whether or not the bending you see is responsible >for closing the gap enough to burn things also. > >Or is the bending the result of melting? > >The ground electrode is upside down in the cylinder, so having it melt and >bend upwards against gravity sounds impossible. > >Is it just the center electrode? > >That would have to still flow uphill even to go to one side of th eplug. >Gravity still exists. > >Still sounds like a rod with a lot of clearance or debris in the chamber. > > >This may be a chicken or egg situation. > >It could be that the one cylinder with higher compression is the one >suffers >most due to always overly advanced timing. > >When any motor gets hot it is less tolerant of too much advance. > >I would not move my CDI unless you want to risk trouble with it running >even >worst due to excessive inductance problems. As an electrical engineer, I >would not recommend lenthening these leads more than a few inches. > >I have run these ignitions and coils in AZ for 12 years always in the >factory locations at outside temps of over 116 degrees. > >Never had a hint ever of an ignition problem. These are dirt simple little >units with no microprocessor and about 2 transistors in the CDI box. >Coiuld probably tolerate an A-bomb going off nearby. > >There is always the small chance that you do have one that malfunctions >when >hot, but I have trouble seeing it able to put out more energy or more >advance !!! > >I suppose that anything is posibble. > >But you would be covering up a bad unit if you kept it cold all the time. >They don't need to kept cold if they are OK. > > >Chuck > > > > > > >From: "John Vriesinga" > >Reply-To: [email protected] > >To: > >Subject: Re: [F500] Help I don't know what to do anymore > >Date: Wed, 27 Sep 2006 16:44:18 -0400 > > > >>Richard, it is not clear what the story is with the electrodes, ground > >>smashed against center or center melted. I wish that John could send > >>some > > > >On different occassions, but always on the same cylinder, I have seen > >electrodes bent/welded, and severely burnt. > > > >>pictures or describe more fully > >> > >>Any sort of detonation or overly advanced timing would pretty much have >to > >>show specks on the porcelin, even if run only for a short time. No > >>feedback from John on that yet. > > > >I haven't been out to look at that yet Chuck. I need to find a magnifying > >glass. > > > > > >>It seems like it would take a really really long hard pull to melt a >plug > >>down in a Solo event, but I could be wrong. > > > >Our average track time is about 50 sec. so there are no long hard pulls. > > > >>He has not said he is turning it back and forth like you describe, but > >>going in one direction. > > > >I am rocking the engine back and forth by hand, and it feels as though > >there is a lot of slop inside. I hope in the next few days to be able to > >get out and work on it. Been a bit sick lately. > > > >Thanks for your help guys. > Everyone is raving about the all-new Yahoo! Mail. --------------------------------- All-new Yahoo! Mail - Fire up a more powerful email and get things done faster. ________________________________ FormulaCar Magazine - A Proud Supporter of Formula 500 The Official Publication of Junior Formula Car Racing Subscribe Today! www.formulacarmag.com or 519-624-2003 _________________________________ _______________________________________________ F500 mailing list - [email protected] To unsubscribe or change options please visit: http://f500.org/mailman/listinfo/f500 *** Please, DO NOT send unsubscribe requests to the mailing list! ***
