[ChrisWarne]

Hi, new to the board but have had my TRX350 FM since buying new in 2002. Great machine, used weekly in the summer to grade a horse arena and the occasional trip across some local fields. In the 10 years I've owned it, the engine has clocked up 128hours only. I had it serviced by Honda at 40 hours, then I've done it myself at the start of each summer since then.
Last autumn I forgot to fill the fuel tank to the brim (as I usually do) before putting the quad away for winter, and due to the wet weather in the UK, I didn't start to use the quad until 2 weeks ago. In effect, it had sat in the garage for 7 months with 1/3 tank of fuel.
Started fine, let it warm up and went to grade the arena as normal. Everything was perfect for 10 minutes towing the grader around (mostly 2nd gear work) and then the engine just quit. No strange noises or anything - it was just as if the kill switch had been pushed across. I tried to restart and after a few atempts, she fired up and carried on, but then died again soon after. My quad has been doing this ever since, but the symptoms follow no pattern:
1. Will start from cold & idle perfectly, but at completely random times the engine just stops. It restarts immediately 99% of the time.
2. Can ride the quad/pull the grader and it will work fine for 10 minutes, then it will cut out. Restart immediately, good for another 'random' minutes then stops - restart & carry on.

There is no connection between placing any load on the engine or it just idling, although it does seem to die more frequently when I'm on the move. Sometimes, the engine will cough/splutter a little, but then go back to normal running. Lastly, this past weekend, I ran it in neutral for 20-30 minutes at varying idle - medium revs, as I thought it might be water (winter condensation) in the fuel (I topped the tank up after this problem started) so wanted to try and clear it. When it did cut out, I restarted immediately, but on 1 or 2 occasions (out of 15 or so restarts) I got a small backfire - probably nothing, but thought I'd mention it.

I suspect that I had (have) water in the fuel tank as a result of condensation & it's now sitting in the float chamber, but before I start taking anything apart, draining the tank, etc... do the symptoms indicate I'm on the right track here?
I've completely rebuilt WW2 Willys Jeeps & a White Halftrack in my time, but these were 70 year old technology and about as simple as you can get.....!

Thanks in advance for any assistance,

Chris, UK

 

[Here 2 help]

Have you changed the spark plug yet? My CRF dirt bike had run flawlessly since 2004. I had done the routine maintenance, but it was running on the original plug. One day about 1/2 hour into a race it suddenly started misfiring, stalling in turns and touchy on the restart (had to crank longer than normal). I had just adjusted the valves the day before, so I didn't suspect valve clearence to be an issue. My first thought was water in the fuel. I had filled up from a gas can (not my regular way of gassing up) with gas purchased from a different station than I normally use. We have Alcohol in our fuel so I really suspected water was the culprit. I drained the carb and made another lap, but no change. I pulled into the pits, pulled the seat and tank, installed the new plug that I had carried in my toolbox for 7 years and when I got back out on the race course the problem was cured. That was about a month ago, haven't had a problem since.

 

[ChrisWarne]

Thanks for the reply and suggestion. I check the plug every 'service' and it appears fine, no fouling, gap correct etc.... although it is the original and now 10 years old. Thing is, the engine starts fine, from cold (2-3 turns), warm, hot (1 or less turns).

That said, 1 in 10 times after it's cut out, it might take 2-3 spins to get it running again, but most of the time it starts in under 1 turn of the starter, which is why I suspect fuel contamination.

I'll change the plug anyway - it's due after 10 years I think!

 

[Here 2 help]

Spark plugs are more intricate than an external physical inspection can reveal. Break a spark plug apart sometime and inspect the internal components or do some online research. The internal construction can cause failure of spark at the tip. This is something I was instructed on early in my training as a mechanic, but I like to push the limits. When I am being paid to keep an engine running at peak performance, I change the spark plug without question.