Back fire when coming up to stop signs?? 06 apex gt

[Firecat_Freak]

I've put on just about 1,500 miles since i've purchased this machine, it has about 6,900 mi total now. I've developed a new problem that has come up in the last 600 miles or so and progressively gotten worse. When i come up to the stop signs under decelleration, I'll get a back fire. Sometimes it's a little one, sometimes a pretty good crack. Other times it won't do it. I can tell it is doing it basically upon primary clutch release and idle down. I'm also noticing that my WOT rpm's initially are at 10,500, but then settle down to approximately 9,500-9,800 rpms. My top speed that i'm seeing with two teeth ground off the pick up is approximately 103mph. I talked to the previous owner and he says it should be climbing from 10,500 to 10,800. Obviously, dependent on snow conditions. He has it clutched with the stock helix, but clicker weights and a different spring in the primary. I only recently got a real good feel for the top end rpms, and don't know what it was doing 1,500 miles ago. I can say that I did not get this backfire 1,500 miles ago.

Another thing i've been noticing, is once in awhile, the engine will quit at idle. Like the idle rpm's have gotten lowwer. Typically it idles at 1,500 when warm. When it dies, it's after i've just blurped the throttle slightly and was idling at 1,200 rpms or so.

I've asked around a bit, and have been told that the donuts are probably shot causing the backfire. I'm not sure if all the problems are related or not. I've covered the exhuast outlets with my gloves to see if I can see the exhaust exiting somewhere else, but have not. The engine may lowwer it's idle rpm's some when the outlets are covered, but it does not quit after holding it closed for about 10 seconds or so. I'm not sure if that is a good test or not. I can also say that the previous owner has changed the donuts before, but i don't know the exact mileage that happeend.

There isn't much season left, so i will likely just drive it as is for the last ride or two, unless someone says i'm damaging something every time i take it out.

Looking for some more opinions. Thanks.

 

[DoktorC]

Sounds like donuts to me...change them ASAP or you'll be doing your Y-pipes too. If you plan on keeping the sled for any length of time I'd go with the copper donuts and buy new clamps...then you're done. If everything come undone ok you can do the job in an evening...

 

[Firecat_Freak]

What if the y-pipes are bad? Is this also what is referred to as the flex pipes? Can they be repaired?

 

[actionjack]

If Y pipes are bad get a set of stainless or get aftermarket header pipes. The flex pipe are the short stacks that bolt directly to the motor. The donuts are between the flex pipes and the y pipes. Check the sticky thread out.

 

[Murse]

Definitely donuts check the whole exhaust too you may have other damage I had to get 2 cracks welded. Dealer fixed and stainless oem Ypipes cost 615$ plus 100$ for copper donuts.

 

[thor452]

100% dounuts if you cover the exhaust the sled will stop like you hit the kill switch

 

[Firecat_Freak]

Interesting, I certainly don't have that happen when I cover the exhaust.

What kind of a power loss will I see with this leaking like it is? Enough to justify my 600-1000 rpm loss on the top?

 

[thor452]

some times if the leak is bad enough you will have no back pressure

 

[Firecat_Freak]

Who do I get the replacement y-pipe from if needed? Yamaha part or aftermarket?

What's the consensus on the donuts, copper or OE?

 

[yamaha1973]

Definitely the copper donuts, aftermarket pipes will get you slightly better performance, not sure how they rank price wise

 

[Firecat_Freak]

I saw mbrp on eBay had some y pipes, and excell had them as well. Not sure if there is really any power gains with either of those or not, can't seem to find any specs.

 

[thor452]

no gain with y pipes the silencer when that goes you can save 200 bucks and gain up to 5 hp