Yamaha TRX850 Enthusiasts Forum

Hello,
Fitted a pair of remus end cans this week and although I had suspected it was backfiring the cans have made it very obvious. The bike only does it very occasionaly on tickover but sounds like a fire work display on over run (but only when dropping below 3k)

I changed the emulsion tubes not long after getting the bike and before that changed one of the coils, will try putting the old coil back on. Also have a tapping valve but can't tell if the backfiring is one or both cylinders

Where else should I be looking?

Thanks

After firing, which is the correct term, would suggest a little rich on the jets maybe. Someone with moire knowledge should be able to give a better answer though.

check to see that they are fitted right and that no air is getting in. Where they bolt on to the stock headers make sure its a tight fit. My tls used to do it all the time the rear gasket would wear and let air in and i would get big back fire's on the over run.

no gasket where the cans fit the headers, just slip-on with an allen bolt to tighten up.
not checked the valve clearences (15k miles) could they contribute?

I know I found the best thing to seal the headers that use to just push into the head in the old thiumph bonnie I had was roofing silicone sealant..(brilliant) Try smearing a healthy coat around the header before sliding the can on and wiping of the residue...

not convinced its the new cans. the bike was backfiring on the yamaha cans but because it was so muted i thought the engine was missing.

replaced the pattern coil with the genuine one i took off (poor running was the emulsion tubes) but not had chance to run it yet. baby is in bed and i really don't want to wake him.

wondering if the nrp emulsion tubes are not machined to as fine a tolerance as the yamaha ones.

had a bit more of a look today.
Refitting the old coil (left side) didn't fix the problem but didn't make it any worse.
Popping is only happening from the right can, left is ok.
Took the plug out the right cylinder looks good, tiny amount of soot on the base of the threads but the insulator is a nice tan colour gave it a clean and out it back. Have also put the pattern coil on the right just to confirm no coil issues.

Not had chance to fire her up as only just finished

Could an air leak cause popping, thinking of squirting wd40 around the airbox/carb/engine rubbers to see if the revs change. Maybe check the fuel tap and fuel pump vacum hoses.

bbb

BBB wrote:had a bit more of a look today.
Refitting the old coil (left side) didn't fix the problem but didn't make it any worse.
Popping is only happening from the right can, left is ok.
Took the plug out the right cylinder looks good, tiny amount of soot on the base of the threads but the insulator is a nice tan colour gave it a clean and out it back. Have also put the pattern coil on the right just to confirm no coil issues.

Not had chance to fire her up as only just finished

Could an air leak cause popping, thinking of squirting wd40 around the airbox/carb/engine rubbers to see if the revs change. Maybe check the fuel tap and fuel pump vacum hoses.

bbb

A lean condition on fuel screw/slow jet on mine made it pop like crazy when closing throttle after a run.
...but there are different scenarios on back fire and forward fire...

fired her up earlier, still exactly the same. Tried spraying GT85 round the carb rubbers but no change in revs so guessing no leaks and no coil issues.

Mixture screw next then. What are factory / best settings?

Thanks
BBB

Killerwhale wrote: A lean condition on fuel screw/slow jet on mine made it pop like crazy when closing throttle after a run.
...but there are different scenarios on back fire and forward fire...

Genius

Checked the idle screw today, wound almost fully in. Guess the previous owner had tried to 'fix' the emulsion tube issue. Backed it out 2.5 turns (and put the genuine coil back in) put it back together and started it up. No popping on tickover let her warm up a bit and gave it some revs and again no popping when closing the throttle. I've yet to try a proper chunk of over run on a long downhill but all looking positive so far.

Mucho Thanks

BBB wrote:

Killerwhale wrote: A lean condition on fuel screw/slow jet on mine made it pop like crazy when closing throttle after a run.
...but there are different scenarios on back fire and forward fire...

Genius

Checked the idle screw today, wound almost fully in. Guess the previous owner had tried to 'fix' the emulsion tube issue. Backed it out 2.5 turns (and put the genuine coil back in) put it back together and started it up. No popping on tickover let her warm up a bit and gave it some revs and again no popping when closing the throttle. I've yet to try a proper chunk of over run on a long downhill but all looking positive so far.

Mucho Thanks

Well, there´s a first for us all
Glad it helped!!

Rode to work yesterday and no popping on over run down some long steep hills . Pipes are a bit loud though . Don't know whether its the pipes or the idle screw or possibly both but the bike pulls from much lower revs. Used to judder at anything below 3k but now pulls cleanly.

is that rust i can see on the disk bolts ??

steve speed wrote:is that rust i can see on the disk bolts ??

Probably what i have: GOLD NUTS.....

anyone with gold nuts is ok in my book ,,, is that a bit of gold on the chain as well ??