Yamaha TRX850 Enthusiasts Forum

Hi All,

I'm not great on all the electrical "thingies" so I'd really appreciate some help.
Picked up a cheap TRX last weekend to use as a daily commuter whilst I finish my project TRX.
It rode OK for a week but now won't start.
The facts:
Was a little hesitant and rough on cold start, would not idle when cold and had to keep blipping the throttle, but once warm it was fine.
During the week 120km per day, struggled a little to kick over as the week went on.
On the weekend started tidying it up a bit.
Lifted the tank to find air box all drilled and snorkel removed.
Fitted a standard airbox and K&N filter I had from my other REX and presto, kicked over and idled fine, but the kicking over was still a bit week. That afternoon the battery died whilst testing the beam pattern of a few different aftermarket H4 globes.
Bought and charged a new Yuasa battery, but bike won't start. Sounds strong when you hit the starter but the engine doesn't fire up.
If I keep trying to turn it over I get a whirring noise.
I'm thinking the starter motor just happened to crap out as well.
Does that sound right or should I be looking elsewhere?

Thanks
Stu

OK - I'm the least mechanically-able here - but ..... plugs?

Fuel??? as in nearly out of, or flow as in the tap may be wonky (wonky? is a mechanical term you understand)

As it was running fine after the airbox change and the only issue after that was that the battery went dead so I was working on the theory of something electrical or connected to.

It is getting fuel, and no bent or damaged fuel or vacuum hoses or the like, also double checked for vacuum issues by switching the fuel tap to prime and still won't start.
I'm off work tomorrow so I will start pulling other bits apart for inspection and I have some new iridium plugs handy so I will put those in anyway.

Hi Stu99!

Not starting when cold and running fine / better when warm sounds typically for to narrow (i.e. non existing) valve clearance(s).

Check or let it check and I bet (at least) the inlet valves are (near to) 0 clearance.

Advising greetings from Munich!

You say it was running rough at low revs, especially when cold, Emulsion tubes?? Put new plugs in and see if it will start, if it does, then as above

Dave E

After I replaced the butchered air box it did run fine cold and low revs hence I was thinking the problem was more directly related to a battery or starter issue or the like. New battery so that shouldn't be the problem.
As it was then running fine before the battery died I am inclined to think that a plug(as mentioned I will change them tomorrow anyway) or carb issue would not turn it from running to not running overnight whilst the new battery charged.

Is there a floor a flaw in my thinking here?

Can't vouch for valve clearances yet as only having picked it up last week haven't had the chance to get that far into checking everything over.

By the way the previous owner had the carbs done with a factory pro kit and new emulsion tubes also.

Battery round wrong way ? as in reverse polarity ? Just trying to hear your whirring as opposed to thumpeta thumpeta

Hi Guys,

Thanks for all the suggestions.
I can't really work on my bike during the week as I get home late from work but also my garage is too dark for any fiddly work. I have to rely on a good amount of sunlight. Hence wanted to arm myself with ideas to get to it today.

Found the following:
Cracked plug on one cylinder and a poorly fitting lead on the other. Starting issues solved along with the new battery previously mentioned.
Poor running to approx 4000rpm solved by removing the modified air box and fitting the standard air box an K&N filter from my other REX.(New plugs helped also of course)

I was expecting to have to find a bigger issue(ie more expensive), it just felt that way, so I have never been so happy to find a faulty plug and lead. It did surprise me a little though as before it died it didn't misfire and went well under load where I have found on my other REX that a poor plug/s usually makes it misfire and/or drop a cylinder under load. Mind, not complaining though.

Thanks again guys,
Cheers,
Stu

Result then

it's always good when it's an easy solution (and amazing that I got it right!!!!!)

^^^^ mistic jak,,, or lucky guess

you mean you don't think it's my natural mechanical talent shining through.............

jak your theory of ,, "if it cant be fixed with a hammer it cant be fixed " wont work

You only got the mechanical bit wrong in there Jak!

Dave E