Yamaha TRX850 Enthusiasts Forum

Hey Guys

I've bought a bit of dog on fleabay(more fool me), its an xtz750 with what the previous owner says is a trx850 engine. When I got it, the bike had no power low down and stalled a lot. I stripped the carbs and replaced all the usual but when reinstalled it wouldn't fire up and would just backfire. After playing around with carbs i checked the plugs for spark and it was tiny yellow spark or none at all.
I've fitted new plugs, new coils, checked pickup coil resistance 258ohms, checked continuity through kill switch, neutral switch, sidestand switch and all ok. It needs cut off relay which ive bypassed but not sure what to check next. Got 12v at the coils, earths test ok.
Can the cdi unit cause a weak spark?

Thanks in advance

Phil.

Replace the plug leads if you haven't already.
You seem to have done all the other bits, but as these bikes are getting on a bit more and more parts are reaching end of life.
Anything rubber (my fuel line split last week!) or plastic that can be exposed to the sun, such as the air cut valve cover on the RHS carb.
The CDI unit itself shouldn't be a problem, they either work or don't, but there are better replacements available from Ignitech.

Also, an XTZ! WooHoo!!! Take good care of that, it's rather special.

Cheers dude, Have come across some alarming bodges since getting it so will be doing a full frame up rebuild but this is doing my head in. I've ordered a new battery for it and a 2nd hand cdi and will see what happens.

Phil.

Valve clearance's ????

Ohhh sorry...i thought "weak intermittent spark" was a discussion about us older guys and the relationship with our wifes........
On the flip-side, my TRX sparks just fine.......