flapper valve

[ron frisco]

I did the demo ride today in Florida, I love the bike, I put a deposit on the street version, is anybody bothered by the popping sound under deceleration from the flapper valve inside the catalytic converter? The sales rep from Triumph says its for emissions. Yamaha has one they call a ex-up valve, but you don't here it working.

[blacktiger]

I'm ready to be corrected but I don't think the popping is from a "flapper valve" or anything mechanical. Going from experience on my Scrambler with "secondary Air Injection" known simply as AI, the popping comes from unburnt fuel being burnt off within the exhaust.
The other thing I'll note here is that my Tiger955 burbles and pops on overrun (most likely due to gaps in the exhaust joints) and I like it because it adds a bit of character to the ride.

[Bixxer Bob]

Ok, just to add a bit of science....  it pops because it's lean on closed throttle, not rich (I know, no-one said it was rich, just being clear).  What happens is the mix is too lean to burn completely before the exhaust valve opens so the unburnt fuel goes into the hot exhaust with the exhaust gases.  When the oxygen / fuel mix in the exhaust is just right the hot exhaust ignites it and it burns.  The expansion of gases from the burn is restricted in the pipe, so it pops or bangs.  The cure is to add a little fuel to the bottom of the fuel map but not too much or you'll get tickover problems.  

[AK Tiger]

I asked the Triumph rep during my demo ride about that.  He stated that it is a valve in the exhaust used to vary backpressure in order to increase torque at low rpm.

[JetdocX]

Doesn't bother me one bit.  My Aprilia snorts and bucks way worse than this one on decel.

[KildareMan]

I asked the Triumph rep during my demo ride about that.  He stated that it is a valve in the exhaust used to vary backpressure in order to increase torque at low rpm.

That's BS, on the sales guy's part, since there's no control of the "Valve" There is no valve.  The most common thinking is back pressure rattling the cat.  Fit an aftermarket free flowing exhaust and it reduces dramatically or disappears altogether.

[radioactive slime]

My 800 pops, tocs, tangs and bangs out the stock exhaust under sudden closed throttle / engine breaking; awesome, sounds like an F1 car. What troubles me is the recent - 3000km in - rattle from the front of the engine area when the bike is ridden when cold after sitting for some hours. There is a noticable ticking sound that becomes an angry baby rattle sound under low speed, low RPM throttle down, 2nd to 1st. After a few minutes of warm up the sound goes away only to return when the engines cold again. Any thoughts? Is it just another "character trait"?[/quote] :?

[blacktiger]

My 800 pops, tocs, tangs and bangs out the stock exhaust under sudden closed throttle / engine breaking; awesome, sounds like an F1 car. What troubles me is the recent - 3000km in - rattle from the front of the engine area when the bike is ridden when cold after sitting for some hours. There is a noticable ticking sound that becomes an angry baby rattle sound under low speed, low RPM throttle down, 2nd to 1st. After a few minutes of warm up the sound goes away only to return when the engines cold again. Any thoughts? Is it just another "character trait"?

I'd get the cam chain tension checked. Don't know 100% but I think I read that oil pressure does something with the tensioner so until the pressure gets up to spec you'll get some rattles.

[radioactive slime]

I had my local dealer take the bike for spin and he was able to hear the rattling, chattering sound.
His diagnosis was very much the same as the one put forth in this forum; a hydraulic cam chain tensioner not up to pressure when cold. He didn't seem overly concerned. I am still concerned as this is new, the sound was never there before. That would indicate something has come adrift would it not?
Any thoughts on the long term effects of a sloppy cam chain on the perormance and life of the engine?

[Bixxer Bob]

Sloppy chain? Sloppy dealer too by the sound of it. It's a warranty fix, pure and simple. If he argues, ask him to start up a showroom bike an hear whether it does it. If not he puts yours right. End of.

[Sin_Tiger]

+ 1 the 800 is even quieter than the 675 , sticky tensioner, warranty.

[blacktiger]

Agree that it's a warranty job.

Seems that the tensioner is purely hydraulic. There is no spring in it.