[winterstarranch]

Greetings everyone, I recently purchased a trx at a garage sale. The seller said it was running when parked. She also said she thought it needed a wiring harness. I have done the easy stuff. replaced the chewed up wiring , cleaned the grounds checked for battery voltage at the cdi with switch on. Switched out coil with a known good one off my 87 250. Alternator creates voltage when cranking. Pulse coil has only 3 ohms resistance to ground. I suspect the pulse coil, does anyone have any advise? Also what is a good manual for that model? I'll need to get one if I have to disassemble to replace the pulse coil. Thanks.

 

[shadetree]

Greetings everyone, I recently purchased a trx at a garage sale. The seller said it was running when parked. She also said she thought it needed a wiring harness. I have done the easy stuff. replaced the chewed up wiring , cleaned the grounds checked for battery voltage at the cdi with switch on. Switched out coil with a known good one off my 87 250. Alternator creates voltage when cranking. Pulse coil has only 3 ohms resistance to ground. I suspect the pulse coil, does anyone have any advise? Also what is a good manual for that model? I'll need to get one if I have to disassemble to replace the pulse coil. Thanks.

stator does 2 things..well..it has two sides..one side charges the battery..works the lights..the other side fires ( sends power to c.d.i )..then to spark plug...you really don't need a service manual to work on your bike for the pulse generator ( more known as the pick up coil )..buttt..it's always a good idea to get one !!..you need to check your stator..pulse generator...make sure battery is fully charged, spark plug is good..kill switch is in the run position..all ground wires are hooked up..spark plug coil is ok...and after all this..and you still don't get spark at your plug...replace the c.d.i with a good known working one..and it has to be for the same year and make..you cannot interchange the c.d.i's from different years and models.

 

[winterstarranch]

91 trx no spark

Shade tree thanks for the reply. I don't have my notes just now but I checked the (source coil) side of the stator. it has 25 ohms of resistance and generates when cranking. The ignition coil has .1 to .2 ohms resistance on the primary side and an appropriate (from elsewhere on this forum) amount of resistance in the secondary. I switched out a known good coil from my 87 250 no spark. The plug is new and attached to a head fin with a vice grip, Coil and chassis ground, battery grounds cleaned and good. I am using a good automotive battery with trickle charger attached. Battery terminals clean. Pulse coil has 3 ohms resistance and I cannot tell if it has voltage when cranking. The mice were in the wiring but I have removed the tank, seat, dash and all bodywork and have inspected and replaced anything that was suspect. The electrical system fuses test good. At key on the neutral light is lit, oil temp light does not light for a moment prior to start as it does on the 87, engine cranks freely with switch. The cdi shows battery voltage at the correct wire. I didn't expect component failures as it "was running when parked" however I have found that sometimes memory is not always accurate, mine certainly isn't. I ordered a replacement pulse coil and will replace it when it arrives. If I purchase a replacement CDI unit do I also need to purchase the (companion) box? Thanks for your help.

 

[shadetree]

Shade tree thanks for the reply. I don't have my notes just now but I checked the (source coil) side of the stator. it has 25 ohms of resistance and generates when cranking. The ignition coil has .1 to .2 ohms resistance on the primary side and an appropriate (from elsewhere on this forum) amount of resistance in the secondary. I switched out a known good coil from my 87 250 no spark. The plug is new and attached to a head fin with a vice grip, Coil and chassis ground, battery grounds cleaned and good. I am using a good automotive battery with trickle charger attached. Battery terminals clean. Pulse coil has 3 ohms resistance and I cannot tell if it has voltage when cranking. The mice were in the wiring but I have removed the tank, seat, dash and all bodywork and have inspected and replaced anything that was suspect. The electrical system fuses test good. At key on the neutral light is lit, oil temp light does not light for a moment prior to start as it does on the 87, engine cranks freely with switch. The cdi shows battery voltage at the correct wire. I didn't expect component failures as it "was running when parked" however I have found that sometimes memory is not always accurate, mine certainly isn't. I ordered a replacement pulse coil and will replace it when it arrives. If I purchase a replacement CDI unit do I also need to purchase the (companion) box? Thanks for your help.

before you go buy a c.d.i..pull your diode out of the wire harness..it looks like a fuse..put a paper clip in it..use this as a jumper ..dont clamp the spark plug to the cylinder fins..just hold it about 1/8 inch from the engine as you crank it..see if you get spark then.

 

[Helmut]

Pulse coil has 3 ohms resistance and I cannot tell if it has voltage when cranking.

Just to be sure, I have to ask, are you sure you had the range set correctly on your ohmmeter when you checked the resistance? The reason I ask is because the resistance should read closer to 300 ohms and if the meter isn't set to the correct range, it could just read 3 ohms instead of 300 ohms. If you had it set correctly, the pulse generator is bad and I haven't seen that many pulse generators go bad on a Honda. On Yamaha, yes, but Honda not many at all.

If I purchase a replacement CDI unit do I also need to purchase the (companion) box?

If you're speaking of the box beside the CDI, which would be the alarm unit, no you don't have to replace it with the CDI. Although, that might be the reason that your oil temp light doesn't come on when you turn the key on, but I don't think a bad alarm unit will keep the ATV from running.

 

[shadetree]

Pulse coil has 3 ohms resistance and I cannot tell if it has voltage when cranking.

Just to be sure, I have to ask, are you sure you had the range set correctly on your ohmmeter when you checked the resistance? The reason I ask is because the resistance should read closer to 300 ohms and if the meter isn't set to the correct range, it could just read 3 ohms instead of 300 ohms. If you had it set correctly, the pulse generator is bad and I haven't seen that many pulse generators go bad on a Honda. On Yamaha, yes, but Honda not many at all.

If I purchase a replacement CDI unit do I also need to purchase the (companion) box?

If you're speaking of the box beside the CDI, which would be the alarm unit, no you don't have to replace it with the CDI. Although, that might be the reason that your oil temp light doesn't come on when you turn the key on, but I don't think a bad alarm unit will keep the ATV from running.

..no..it won't keep it from running..the c.d.i will keep it from running if the bike doesn't know it's not in nuetral..this i do know.

 

[Helmut]

On the '98-up, they did away with the alarm unit and combined it with the CDI, so it's possible that the '98-up wouldn't run when the oil temp light comes on. That's just a guess. I've owned some of the '98-up 300s, but the oil temp light never came on, so I don't know. I've seen the oil lights come on, on the '88-'97, and they would still run.

 

[shadetree]

On the '98-up, they did away with the alarm unit and combined it with the CDI, so it's possible that the '98-up wouldn't run when the oil temp light comes on. That's just a guess. I've owned some of the '98-up 300s, but the oil temp light never came on, so I don't know. I've seen the oil lights come on, on the '88-'97, and they would still run.

when they had the alarm unit on them..they tried to copy the design from the trx350d foremans..by having the alarm unit ( control unit as per mine )..shut the bike down when the fan stoped working..i don't think thats what is going on here though..as you said..they done away with the alarm units..and simply combined it with the c.d.i. yes..the 300's will run with the oil light on..matter of fact..i think sub had this problem not long ago ??..i think so anyway ??..sooo..even if his oil light isn't working..or even staying on for that matter..it won't keep it from running..not that i know of anyway ??.

 

[Helmut]

yes..the 300's will run with the oil light on..matter of fact..i think sub had this problem not long ago ??.

It was Fourtrax that was having the problem.

 

[winterstarranch]

Thanks everyone for your help and feedback, I forgot to say that I checked the diode with my VOM no continuity in one direction shorted in the other but I will try the jumper. I had the same thought about the ohms range on the 10 ohm resistance range of the VOM and thoroughly confused myself using several different meters reading the resistance of the pulse coil. I finally replaced the batterys on 2 simpsons and the fuse in another radio shack and they all agree 3 ohms (3 on the 10 scale) ohms resistance to an engine case ground on the pulse coil. I read somewhere that a UJM pulse coil is 300 ohms. I had the same thought that I was on the wrong scale so I tried all the meters that I own and even went back and read the meter manual. I may find that I have made another mistake but I don't think so, I hope not, O heck when the new one arrives I will check it against the installed one before I replace it. Thanks again WS. Back posting in the next few days.

 

[jeremysierra]

Thanks everyone for your help and feedback, I forgot to say that I checked the diode with my VOM no continuity in one direction shorted in the other but I will try the jumper. I had the same thought about the ohms range on the 10 ohm resistance range of the VOM and thoroughly confused myself using several different meters reading the resistance of the pulse coil. I finally replaced the batterys on 2 simpsons and the fuse in another radio shack and they all agree 3 ohms (3 on the 10 scale) ohms resistance to an engine case ground on the pulse coil. I read somewhere that a UJM pulse coil is 300 ohms. I had the same thought that I was on the wrong scale so I tried all the meters that I own and even went back and read the meter manual. I may find that I have made another mistake but I don't think so, I hope not, O heck when the new one arrives I will check it against the installed one before I replace it. Thanks again WS. Back posting in the next few days.

just wondering if you got this working... i am having the same problem with my trx300 but its a 1992 model. I am getting a .340 ohms reading when testing the pulse coil?

 

[toyota]

Back to basics, you haven't mentioned a new plug??? could be a dead short in the old one, as shadetree suggests, hold the plug a short distance from a good ground point, don't worry, you won't light up!!