Yamaha TRX850 Enthusiasts Forum

Help !!
Fired my TRX up yesterday after being sat in the garage for a week.
It started on one cylinder then the second chimed in briefly. It's done this before but usually clears and runs normally after a minute or two or a blast up the road.
(I normally put this down to an oiled plug … and cleaning and checking the gaps usually fixes it) … but not this time.
It will not tick over below about 2000 rpm and sounds and feels like it's only running on one cylinder .. but both pipes and silencers are getting hot.
Carbs were fully rebuilt with all new jets, needles, tubes, etc last year at 37,000 miles.
Anyone got any ideas or suggestions. I have very limited workshop space or mechanical knowledge.

Hello !!
Check the valve clearence ... i beg the inletvalves are too tight.
Greets !!

Hi Red Rex, had exactly the same symptoms as yourself to the point of not clearing itself after a minute or so, My entrusted mechanic advised me to NOT use 98 Ron fuel and use a hotter heat range spark plug, Problem solved completely and plug colour now a tan instead of black!

Hi Red Rex!

I would also put my money on the (too tight) valve clearances.

When were they checked last?

Guessing greets from Munich!

spiritedride wrote:Hi Red Rex, had exactly the same symptoms as yourself to the point of not clearing itself after a minute or so, My entrusted mechanic advised me to NOT use 98 Ron fuel and use a hotter heat range spark plug, Problem solved completely and plug colour now a tan instead of black!

I’ve never heard that one before. Please elaborate?

Hl Tarwetijger, Theory being that high density fuels used in motors with some nominal wear ( mine has 55,000 ) can cause minor plug fouling,supposedly only hi compression ratio engines can give a clean burn to 98.The hotter plugs also aid in the burn,I was at the point of getting him to do a motor strip down ,but his theory has definately put that off for some time.

Thanks guys for all your replies.
When I spoke to my local mechanic and described the symptoms he gave me a very competitive quote to strip down and check / reset all valve clearances.
Then he advised to fit some new plugs (not just clean and re-gap the existing ones)
Did that …. Problem solved (and saved a couple of hundred £££'s into the bargain)
PS. Currently running NGK DPR9EA-9 plugs ,,, What do you recommend as a 'hotter' alternative?

Hi Red Rex!

A quick search at louis.de brought the type NGK DPR8EA-9 for our TRX.

The number on NGK plugs for the heat rating (i.e., the first number after the letters) are decreasing with the higher rating.

Following this, you are running a colder "9" spark plug at the moment as the recommended hotter "8".

Note that other manufacturers (BOSCH, BERU, ...) use higher (and other!) numbers for higher heat rating.

Hottest greets from Munich!

HI Redrex, good to hear you have overcome the problem, I only went 1 heat range hotter than standard,forgot to mention that mechanic also said that the high humidity we have been having in my part of the world was also a factor with black plug colour and fouling.

Thanks for all the help guys.
I'll run her on the "9"'s for a while and then when I fancy loosing some more skin off my knuckles, will swap out for a set of "8"'s and see how that goes.

https://briskaustralia.com.au/BOR12LGS
Used to run the BOR12LGS plugs . No shrouding to stop fouling and multiple earth straps.
$18 each so around the same price as an iridium plug too.
If fueling, humidity and atomisation is an issue with a std plug your dictated by the 1 single direction the earth strap faces plus creates shrouding and the Brisk plugs give no shrouding and denser fuel molecules will give less resistance so it’s open at 360* to find that within the chamber.
Easy 40,000km life span too .

https://m.youtube.com/watch?v=yBWjzo2Zfw4