Yamaha TRX850 Enthusiasts Forum

Hi all,
Im in the final stages of getting my TRX ready for the road after 9 months of gathering parts and numinous mods. But I hit a stumbling block when the bike failed to start...now ill explain as best I can..
Fresh petrol... I removed a spark and when I go to start I have one spark and only one spark, if I leave off the start button and press it again immediately I will again only get one spark. I can get a spear ECU to check if that's what's at fault but that ECU has been seating in a box in a damp shed for the last eight years....
Any info would be greatly appreciated.
Thanks in advance,
Ger.

Have you eliminated everything back to the box? Iridium plugs can be a painin the arse. Tried a seperate plug in each lead to see if there is spark??I had one pair fitted with one plug die within 500km .. So a couple of runs... Check terminals for signs of corrosion , Change coils around and see if the same cylinder is still not firing.

cobbadiggabuddyblooo wrote:Have you eliminated everything back to the box? Iridium plugs can be a painin the arse. Tried a seperate plug in each lead to see if there is spark??I had one pair fitted with one plug die within 500km .. So a couple of runs... Check terminals for signs of corrosion , Change coils around and see if the same cylinder is still not firing.

Mostly the cdi will be encased in a hard jell to protect the electrics and all..its all inside the cdi case, but they can go wrong...a quick answer is to like Cobba said, note which plug is fireing..then chang the coil packs over [ emery paper to the coil mount bolt surfaces ]..and try it again.
Alternatively, find another member and swap the CDI over..
OH and another thing..there is a small hole on the left side of the head below the cam cover,..make sure it is clean as it allows water from the spark plug recesses to drain when the bike is on the side stand..if the wasps have built a home there, your spark plug might be shorting out.

alextrx850 wrote: OH and another thing..there is a small hole on the left side of the head below the cam cover,..make sure it is clean as it allows water from the spark plug recesses to drain when the bike is on the side stand..if the wasps have built a home there, your spark plug might be shorting out.

I wondered what that was for, mystery solve, thanks

Thanks guys, but its the two spark plugs will only give one spark when I crank the starter...The reason behind my thinking its the ECU or CDI is I fitted an alarm immobiliser and when I activated the alarm the alarm box shorted out in a cloud of smoke ...sorry should have told ye that in the first place . I have seance removed all wiring belonging to the alarm and alarm itself. Another thing I have removed the original clocks and replaced them with digital unit.

STREUTH..!

Okay tonight I tried a mates CDI box and no joy...same story one spark then nothing....

gereen50 wrote:Okay tonight I tried a mates CDI box and no joy...same story one spark then nothing....

Ok. maybe try your mates bike with YOUR.. cdi...keep going until you find a miss match...
Put the OEM speedo set back on...never know..?

Tried putting the original clocks back on with no joy... Unfortunately my buddy only has parts for a TRX and not a running one
My next step is to swoop out the coils and try to get my hands on a starter relay just to eliminate those parts... All wiring looks fine so its a bit of a head scratcher.

Try isolating the side stand cut out switch, get a test light or meter and find out if you have power/ (check 2 main fuses 20 or 30amp?) then signal going to the black box then from to coils. If you have signal all the way it may be an earth issue

Should be home tomorrow night and Ill try isolating the side stand switch...fuses are fine. Ill let ye know how I get on.

Thanks for the help...much appreciated.

I dont see how sidestand switch could cause ONE cylinder to not fire. Change coils side to side to see if problem moves with coils (clean coil earths while you have them off). Check spark trigger coil resistance and wiring to dead cylinder.

as he said one spark then none... something has robbed him of both spark now... I hate electrical problems... at least when you piss into the wind you can see it and turn out of the way to stop the problem

Just to get you thinking, could it be the pickup? Why it would only take once i cannot see...but i would have a look anyhow.

Sorry to borrow your thread, but I am still chasing a lost spark too.
Does anyone have great experience with the Yam / TRX style ignition pickup?

As I understand it (said with large gaps between words,,,,,,,,,,,,) the ignition pickup has only one coil. The rotor has 3 triggers, 2 small and 1 large.
I assume the large one tells the CDI to reset (or similar) and the two smaller ones ask it to send a spark to their respective sparkplug.

Soooooo,
if the actual pickup was faulty, you couldn't really drop just one pot as it would not send a spark to either plug, as it is using the same pickup coil for both sparks.

To drop just ONE spark by using that system you would only have the option of a failure from the trigger "dot" on the actual rotor.

Ergo, that not being the issue, any one-sided loss of ignition spark MUST come from somewhere between the CDI and the sparkplug itself.

Can someone affirm this?

cheers