I bought this quad over seven years (new) ago and never had a problem with it until now.

Here goes... Cranks over but will not run. I got fuel and spark but the spark seemed a little weak to me, so I replaced the coil and new plug (.030" gap). I also adjusted the exhaust valve to .004", it was at .007". Still wont start, even spraying some starter fluid in it too. Cleaned air cleaner, drained carb bowl, I put in a used CDI and tried it again, nothing. I noticed a wire going to the front cooler sending unit was rubbing on the cooler and exposed the copper wire. Is it possible that it shorted and killed the black box that this wire goes to, therefore causing it not to start ??? This box says... SURE POWER INDUSTRIES, INC. 4010697 2X4 S/N 02003126 It has raised fins on the outer part of the box Thanks

 

that box is the voltage regulator and fan control module its very unlikely that just that is bad and your not getting your boss to start. but this is a dc assist bike where it needs battery voltage to run and if your battery is dead or not in the cdi wont send enough or no spark to run. there could be a couple other options low compression? these trail bosses have some wacky problems sometimes.

 

So does the spark still seem weak? If the spark seems good, check the compression.

 

Do you want to sell the extra cdi? I have one that I thing will need one. Thanks Tony T

 

I let the quad sit in my shop for 4 years after i tried pretty much everything. Now I am starting all over again.
The Trailboss has spark and fuel but am not sure if its enough pressure. Will remove the fuel pump and fuel selector switch and clean.
I have replaced the old oil sensor at the cooler ($100.00 ouch), rebuilt the carb, new plug, oil & filter, and replaced the pull cord on the recoil.
When I crank it, it pops out through air intake but does not want to run.
I thought it might be my valves so i adjusted them. Still no start.
Any ideas guys?

Tony, I do still have that spare part you were asking for. I know its been a while. If you still need it, send me a private e-mail.

 

Valves set at .006 for intake and exhaust. Had a few 500s and 325/330s jump timing over the years. Mainly because the slotted nut behind the stator that holds the crank timing gear tight on the keyed crank shaft backed off which threw timing off.Could be source of the problem. One thing you can check out. If it's not that then best to get the 330 manual and do an electrical check.Plus the finned module is the ecm and they have had problems. You're model is not on the original recall,but should have been.Plus this module part number has been changed to #4010944. Controls mainly the fan and charging,but can cause other problems. Item#18.Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse

 

off topic question the scrambler 400 i got runs fine but when u wind it out and full throttle rid when u let off it wants to die but u can play with the choke it trys to run what the problem the mud bog is comeing up and i dont want it to hie in a mud hole

 

What year model?? Most have a rubber dampening block under the carb mounted on the tranny to stop it from dumping a load of fuel into the crank case after coming down from a high speed run.This lead to bogging or trying to die down until the fuel could catch back up in the carb bowl. Plus if you haven't been through the carb,could be a worn needle and seat along with a worn float pin and float arm that could be sticking. This can cause the same symptoms.Plenty of carb kits on ebay. If float pin and float are needed,you can get one from here as they're not in the kits.Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse

 

its got new gaskets new same size jets new choke plunger needle and screws havent been able to notice the problem till i rode it on the road and it hits the rpm limiter before it hits top speed the cdi i got a wile back they sent a sportsman 400 DL cdi when it was listed under the scramblers parts they wouldnt exchange or refund so i chopped the old one apart and re soldered a new cap on it and it runs fine and the the electricals work every so often idk why but the 4x4 works and the 2 gear lights work and the handlebar control light works but it needs a new solenoid and a rebuilt starter but it runs fine wide open till u come down its a 99 400 4x4 its got the rubber thing

 

If you have to play with the choke as it comes down off a high speed run to keep it from dieing,still sounds like it's either emptying the bowl fuel into the crank case like the old 94 models did,fuel may not be loading back up quick enough in the bowl.Still sounds like either fuel supply or carb related.As much as these engines vibrate,carb parts wear out fairly quick especially the float pin and float arm and needle and seat. All it takes is for it to stick a little,not allowing enough fuel to refill the bowl quick enough. You can check the reeds,pull the line off the carb and see if it has good fuel flow,plus check that the carb vents are clear.Don't know if that helps any,plus on a different subject, pull the black wire off the reverse limiter as they all go out.They can cause limiting problems in forward range also.