Kelum Posted November 15, 2011 Share Posted November 15, 2011 Hiya guyz, Been offline for a while was tied down with work...so hope all the guyz doing well.. Would you guys tell me how would you identify faulty plug caps with a multimeter or any other means? My engine's got a lazy start, a heavy misfiring going on in front cylinder..like it fut futs doing well at lower gears. However you can still ride, the issue starts to appear right after you slower the bike in order to turn or at a zebra crossing. I have to accelerate greater than usual in order to make her move right after some stop. I checked spark plugs and the front cylinder had sooty black carbon build-up but the sparking points were clean at the gap, carbon build-up was around 20% which I think is normal? The rear cylinder had no carbon at all and the combustion seems to be good. Both spark plugs are new and genuine NGK made for Yamaha. I saw on the net there is a resistor in plug caps, may be its damaged, I tried to check continuity in caps but no reading came out in multimeter. Is it possible misfiring to come with bad plug caps? The misfiring comes all the time right after washing the bike or riding in the rain. In that case also engine starts to fut fut at low gears but sometimes at the 1st when I accelerate more the bike moves speedily. May be faulty ignition coils? How can I check them with multimeter? There is a sudden brightness increase in the headlight also, it comes on and off, sometimes the brightness remains for several minutes and reduces... Does my bike having a serious issue, have you guys come across the same? can oxide buildup in plug caps or something cause this? Faulty rectifier? or battery? Please help me..thanks guyz! Link to comment Share on other sites More sharing options...
Kelum Posted November 15, 2011 Author Share Posted November 15, 2011 Plus when I accelerate the bike at neutral...I get heavy smell of some oily/petrol vapor...is that normal, its coming from the exhaust pipe opening behind rear cylinder for sure..does this mean improper combustion? probably misfiring causes unburnt gas vapor to emit from pipes? My bike doesnt have a sidestand switch too, how can I locate switch connectors? Am lost please help.. Link to comment Share on other sites More sharing options...
neversaydie Posted November 15, 2011 Share Posted November 15, 2011 Hi Kelum, hope youve been keeping well. Just a couple of quickies to start off with. Check the plug is screwed in tight, check that the plug gap is set correctly, if there is a small screwed cap on the plug make that that is is nice and tight. Try swapping the plugs over, does the fault transfer with the plug? Try swapping the leads, does the fault transfer over? Link to comment Share on other sites More sharing options...
Kelum Posted November 15, 2011 Author Share Posted November 15, 2011 Hi buddy, will check all and tell you..I did this today, I swapped the plug caps and the miss grew wilder I couldnt ride her even...then I changed caps back again and worst became bad. I read this article too..anyway will try and see tomorrow better and update u..please be there for me.. http://www.viragoownersclub.org/Dr%20Piston/ignition.htm Link to comment Share on other sites More sharing options...
Moderator Airhead Posted November 15, 2011 Moderator Share Posted November 15, 2011 resistor plug caps are often 5000 Ohms, if you want to check take a reading with your meter set to 20k Ohms, why not compare one plug cap against the other. Theres definitely something going on to have a sooty plug...not good! Link to comment Share on other sites More sharing options...
Kelum Posted November 16, 2011 Author Share Posted November 16, 2011 resistor plug caps are often 5000 Ohms, if you want to check take a reading with your meter set to 20k Ohms, why not compare one plug cap against the other. Theres definitely something going on to have a sooty plug...not good! OOooh buddy u just killed me, would this relate to piston rings etc? I hope not..yes I will compare two and see, sooty carbon wasnt very much, but yes something's wrong..am scared.. Link to comment Share on other sites More sharing options...
Kelum Posted November 16, 2011 Author Share Posted November 16, 2011 Guyz just checked resistance in both caps at 20k setting on multimeter. The standard being 5k I'm getting 10.52 and 10.12k for plugs. The 10.52k reading comes from the cap with the sooty carboned plug... What the hell is going on...the resistance is almost twice, does this mean the voltage plugs getting is way too low? what should I do? and Ray one cable is not long enough to reach other cylinder so swapping coils not possible. Like I mentioned swapping plug caps worsened the issue...there was copper oxide at coil wire - plug cap (screw) end which scraped off... Link to comment Share on other sites More sharing options...
Moderator Airhead Posted November 16, 2011 Moderator Share Posted November 16, 2011 nahh dont panic kelum, i said 'often 5000' it seems yours is 10000 resistor caps, try cutting 12mm off the HT wire where the cap screws on, (assuming you have enough length to do so) Link to comment Share on other sites More sharing options...
Kelum Posted November 16, 2011 Author Share Posted November 16, 2011 Why does it have to be 12mm? I cut off some in other cylinder, will do in the front too, but what if wire shortens by and by, will I be able to buy one and hook it up to the ignition coil...even today I noticed missfire is very prominent when you slower the bikey.. Link to comment Share on other sites More sharing options...
Kelum Posted November 16, 2011 Author Share Posted November 16, 2011 I cut around 12mm off the front cylinder wire, holy shit all the copper wires had pale blue stuff along them...I think the wires should be replaced and may be they resist current flow? according to this replacing is a piece of cake. http://www.ehow.com/...virago-535.html Can I use any set of wire or is there some particular amperage for xv125? After cutting off still there is a slight miss I think because copper oxide running along the total length of wire thats why? I have never been able to keep bike running at idle, I mean let engine run without me having grip on accelerator. (hope I gave the idea, how do you say that?) Link to comment Share on other sites More sharing options...
neversaydie Posted November 16, 2011 Share Posted November 16, 2011 You need to buy a set of leads for the bike, should come with the proper caps on both ends. Its an easy job to replace the leads, pull old ones off , push new ones on. Make sure plugs are clean and gap is correct Id check other electrical connections too for cleanliness/dryness, as I recall that you ride the bike in tropical downpours, and muddy roads Link to comment Share on other sites More sharing options...
Kelum Posted November 16, 2011 Author Share Posted November 16, 2011 Thanks Ray and all...buying leads what amperage etc I should consider...? yes Ray you have a good memory..thanks! Link to comment Share on other sites More sharing options...
Moderator Airhead Posted November 16, 2011 Moderator Share Posted November 16, 2011 amperage doesnt matter mor to the point it is HT (High tension) cable and must stand thousands of volts, thats why the insulation is so thick. on many coils this lead isnt supposed to be removeable and is glued into the ignition coil...how about yours? Link to comment Share on other sites More sharing options...
Kelum Posted November 17, 2011 Author Share Posted November 17, 2011 When I was dealing with cables I felt like they were rotating at the coil end, so I think they are removable, will do that anyways...I think I should put some glue after fixing in order to avoid moisture get in..thanks mate Link to comment Share on other sites More sharing options...
Kelum Posted November 18, 2011 Author Share Posted November 18, 2011 I connected new wires to ignition coils, removed faulty plug caps and put NGK new ones. Gonna have a ride n see..the wires were not glued to coils.. Link to comment Share on other sites More sharing options...
Kelum Posted November 18, 2011 Author Share Posted November 18, 2011 Had a ride, bike feels powerful, still at times I feel misses, plus when u decelerate engine stops. What would be the areas I should look into? Link to comment Share on other sites More sharing options...
fireman fez Posted November 18, 2011 Share Posted November 18, 2011 sooty plug, deffo fuel, Link to comment Share on other sites More sharing options...
Kelum Posted November 19, 2011 Author Share Posted November 19, 2011 sooty plug, deffo fuel, Now am thinking the same, I must remove petrol tank and check filters if they are blocked and water trapped. Plus must check coils too. You can ride for around 100 meters and there's some stop in the engine and the speed maintained due to previous pushes and it starts again, seemed this miss was periodic, anyways if it were a fuel issue the miss shouldnt have been periodic..? am wondering if there is a problem with current flow to ignition coils or they themselves behaving naughty? how would u normally check coils with a multimeter anyway? Link to comment Share on other sites More sharing options...
Kelum Posted November 19, 2011 Author Share Posted November 19, 2011 The engine mercilessly cuts down power specially when u slower the bike in low gear..its like both cylinders stop together..yes it is because bike suddenly becomes silent and again she runs..silent because both cylinders stop..this happened several times now...am thinking of carburetor checkup by myself, can someone guide me, may be with some photos? tell me what I should do and what I shouldnt..? plus I think I must adjust tappets too, is there O-rings with the bolt caps on tappets? for this I must completely remove gas tank and keep it away I guess...no room otherwise..any help appreciated.. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted November 19, 2011 Moderator Share Posted November 19, 2011 I would get a new ignition coi / coils if you can kelum sounds to me that yours have 'had their day' the test is usualy checking the coil resistances both LT coil and HT coil, LT is the (orange?) to ground, and HT is end of HT lead to ground (possibly with cap removed) the problem is...knowing the spec figures . That will be in the manual? Link to comment Share on other sites More sharing options...
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