[Munch]

A friend has a TRX 400ex, he checked the valve clearances (as far as I know) tightened them a little as they were loose.

Since the above the bike hasn't started, I've had a quick look at the manual and set clearances to 0.1 and 0.12 and it still won't run, it seems such an easy straight forward job I can't understand what has gone wrong? Am I missing something? It's the first time I have ever touched an ATV, I have worked on dirt bikes a lot. I am reading about a decompressor adjustment?

 

[Duck0fDeath]

It was running before the valve adjustment, I assume? You sure you had the timing marks set to TDC on the compression stroke and not exhaust.

 

[UnkleRaRa]

The exhaust valves should have .005 inches of clearance, and the intake valves should have .004 inches of clearance.

 

[Munch]

It was running before the valve adjustment, I assume? You sure you had the timing marks set to TDC on the compression stroke and not exhaust.

The bike ran great before he checked the clearances. I'm not sure about him but I personally turned crank anti-clockwise with 17mm socket until I saw the T mark and lined it up and felt free play in the rockers which is where it's meant to be? I then set it to the proper clearances.

The exhaust valves should have .005 inches of clearance, and the intake valves should have .004 inches of clearance.

I am using mm as I am in the UK sorry

 

[Duck0fDeath]

Sounds right. Start from square one, maybe? Got spark and fuel flow?

 

[Munch]

Sounds right. Start from square one, maybe? Got spark and fuel flow?

I know the stator is good as I have connected another plug to the lead and it sparks fine, unfortunately I haven't got a tool that will fit the plug currently but the chances of the plug going bad are very slim surely? It worked fine before he did the clearances!

One thing I have been wrong on is the year, it's actually a 2005 model. I am reading through the manual at the moment and clearances seem the same. I still can't find a good explanation on the decompression clearance!

 

[Duck0fDeath]

I can't help with the decompression. I can't imagine that would cause your no start condition though if your using the starter to crank the motor. Is it cranking good, or struggling? How's the fuel flow?

 

[XplicitRacing6]

Like what Duck said. Check fuel. Spark. Good voltage in the battery. Have you ever cleaned the carb? You need to "retrace your steps" as they say

 

[SlammedRanger]

Spray some starting fluid in the intake with the filter off and choke off and see if it fires for a few seconds on that. If it does its a fuel flow issue. Petcock could have gone bad when you turned it off to remove the gas tank. Check all the easy stuff. Kill switch and all that stuff. Cant tell you how many times i have missed something that just ended up being simple. Did the gas tank get set in a way that fuel could have ended up in the tank vent and be not allowing fuel to flow into the carb? Try removing the lid and see if it starts then. You only remove a few things to get to the adjustment covers so our options are limited. Try tapping the side of the carb. Maybe the carb float got stuck closed and isnt allowing any fuel to come in?

 

[LedFTed]

i want to say check for spark, what i dont want to say is, check the switch on the left handle that snookered me more than once

 

[Hondawasaki]

if the 400 ran prior to the valve clearance adjustment i would double check them b4 digging deeper .. also while at TDC pull and inspect the timing tensioner they are known to fail on 400ex's or 400x ( same thing ,one has a kicker) and being a bike guy if you ever had a XR400 it is the xr400 motor for the most part i is like the later model xr400's the early model ones had 2lobe cams and different rocker setup
.
and like others stated the decomp has caused lots of folks problems