[NMKawierider]

The other day when I was testing the new clutch setup the last thing I did was take it to some straight roads so I could test the top end. By the way it still got 62mph. Anyway, after the last run I noticed the engine running different and what sounded like an exhaust leak. I assumed I had blown an exhaust gasket somewhere.

So last night I decided to find it- so I started it and put my hand over the exhaust outlet and sure enough it wouldn't build pressure at all and I could hear a bad leak. With one hand covering the exhaust discharge I used the other to see if I could feel where it was coming from. It was one of the two spring-loaded pressure couplings and it was from the bottom side. I grabbed the pipe and muffler and gave it a little twisting action and it popped back in place and sealed well. No more leaks. Thought the muffler bolts were loose so checked them. They were tight...springs all good..head piped all tight. So the only other thing I can think of that could cause them to push apart is pressure from within. I was up there pretty high in the RPMs to get that 62mph so the question has to be...how much back pressure does it take to overcome the forces of those four springs. I'm sure it's pounds..not ounces ...and that can't be good.  You guys with the aftermarket mufflers will probably never encounter this situation. I'm going to make a few "adjustments" to the muffler to help it flow a bit better but looks like an aftermarket unit is in my future.

Just thought I would share.

[emersonsc]

The other day when I was testing the new clutch setup the last thing I did was take it to some straight roads so I could test the top end. By the way it still got 62mph. Anyway, after the last run I noticed the engine running different and what sounded like an exhaust leak. I assumed I had blown an exhaust gasket somewhere.

So last night I decided to find it- so I started it and put my hand over the exhaust outlet and sure enough it wouldn't build pressure at all and I could hear a bad leak. With one hand covering the exhaust discharge I used the other to see if I could feel where it was coming from. It was one of the two spring-loaded pressure couplings and it was from the bottom side. I grabbed the pipe and muffler and gave it a little twisting action and it popped back in place and sealed well. No more leaks. Thought the muffler bolts were loose so checked them. They were tight...springs all good..head piped all tight. So the only other thing I can think of that could cause them to push apart is pressure from within. I was up there pretty high in the RPMs to get that 62mph so the question has to be...how much back pressure does it take to overcome the forces of those four springs. I'm sure it's pounds..not ounces ...and that can't be good.  You guys with the aftermarket mufflers will probably never encounter this situation. I'm going to make a few "adjustments" to the muffler to help it flow a bit better but looks like an aftermarket unit is in my future.

Just thought I would share.

Every ZForce 800 i've sold so far, EX or not, has had an issue where they start to leak where the muffler connects to the head pipe section. I have yet to find what is causing it. I believe the springs are getting weak due to heat. I also think the exhaust doughnuts they use are too small and dont form a tight enough seal.

[NMKawierider]

The other day when I was testing the new clutch setup the last thing I did was take it to some straight roads so I could test the top end. By the way it still got 62mph. Anyway, after the last run I noticed the engine running different and what sounded like an exhaust leak. I assumed I had blown an exhaust gasket somewhere.

So last night I decided to find it- so I started it and put my hand over the exhaust outlet and sure enough it wouldn't build pressure at all and I could hear a bad leak. With one hand covering the exhaust discharge I used the other to see if I could feel where it was coming from. It was one of the two spring-loaded pressure couplings and it was from the bottom side. I grabbed the pipe and muffler and gave it a little twisting action and it popped back in place and sealed well. No more leaks. Thought the muffler bolts were loose so checked them. They were tight...springs all good..head piped all tight. So the only other thing I can think of that could cause them to push apart is pressure from within. I was up there pretty high in the RPMs to get that 62mph so the question has to be...how much back pressure does it take to overcome the forces of those four springs. I'm sure it's pounds..not ounces ...and that can't be good.  You guys with the aftermarket mufflers will probably never encounter this situation. I'm going to make a few "adjustments" to the muffler to help it flow a bit better but looks like an aftermarket unit is in my future.

Just thought I would share.

Every ZForce 800 i've sold so far, EX or not, has had an issue where they start to leak where the muffler connects to the head pipe section. I have yet to find what is causing it. I believe the springs are getting weak due to heat. I also think the exhaust doughnuts they use are too small and dont form a tight enough seal.

I was out again today and tached it up only to about 6500 on a few situations and the other one (upper) became un-set..meaning it was not in the socket correctly. That one I had to loosen the muffler and wiggle it to reset it. It did seal though and I re-tightened the muffler. I only have 300 miles on this but you might have something on the heat and springs. When I noticed it I grabbed leather work glove from the box to do some wiggling and when I touched it to the discharge pipe, it burned right through it...like it was red hot. That means it may be even hotter back by the springs.

[NMKawierider]

Well, after taking a look I did find one issue. The parts list shows all the exhaust springs to be the same, and the springs on the lower Y coming from the rear cylinder are very well stretched..20% of their 76mm length as recommended, however, the upper four, going into the muffler itself are hardly stretched at all...in fact I removed them with a pair of plyers. There is 77 mm between the two hangers and the spring is 76mm so they are stretched a whapping 1mm. That connection isn't tight enough so I just ordered two sets of Moose Racing 63mm exhaust springs at 13.95 per set for that joint. That will fix that connection.  What next?..

[Sockman]

Old thread, but I'm having a louder exhaust as well.  Pipes to the head are all firm.  Wonder if I have the same issue you had.  I'm also getting a lot of popping on deceleration.

[NMKawierider]

Old thread, but I'm having a louder exhaust as well.  Pipes to the head are all firm.  Wonder if I have the same issue you had.  I'm also getting a lot of popping on deceleration.

I don't recall if I ever mentioned it anywhere but when I was testing the exhaust back-pressure while doing my exhaust mod, with everything stock when I put it to the floor I got just over 4psi on my gauge..not oz..psi! That's way more then enough to push a spring-loaded joint apart...especially with those cheap Chinese springs. The Moose springs...although not cheap...have never let me down.

[Sockman]

That does seem like a high number.  So, was it difficult getting those 63mm springs on?  And how many do you need total - 4?

Thanks

[NMKawierider]

That does seem like a high number.  So, was it difficult getting those 63mm springs on?  And how many do you need total - 4?

Thanks

Eight total(I think) for the two flex points on either side of the heat deflector.. prior to the muffler. I forget if there ware any on the muffler itself but if so I didn't replace them. You will have to measure between the hook points on the spring mounts then order the springs 20% shorter to get the right ones...CFM's consistency on manufacturing needs some work. It is important to get the right size so as not to over...or under stretch the springs. As for installing I could have bought a hooked spring tool but I just bent a hook in the end of a nail and gripped it with some vice-grips. Some pics:

[Sockman]

Awesome!  Thanks.

[Sockman]

Welp, never question the master!  NMK right again.  The front joint had the gasket completely gone, and the springs stretched out.  No wonder it was making noise, and popping on decel.  Not to mention not having the oomph it used to have.  Now to find some new gaskets and replace the front 4 springs.

Makes me wonder if the gasket fell out, or ended up in the muffler/silencer.

[NMKawierider]

Gaskets probably broke in half and fell out. Don't trust that CFM used the right size springs. Measure where they go and buy springs 20-30% shorter.

[Sockman]

Gaskets probably broke in half and fell out. Don't trust that CFM used the right size springs. Measure where they go and buy springs 20-30% shorter.

All 12 springs look to be the same length, at least they started out that way.  76mm inside length.  The rear 8 springs were fine (4 coming from the rear cylinder, and 4 going into the silencer), just the 4 coming from the front cylinder were stretched.  Makes sense that it would get hottest there since that's where the exhaust from the two cylinders meets and then the rear cylinder exhaust has to make nearly a 180 to go towards the silencer.  Plus the front of the Y-pipe (held on by 4 springs) is constantly fighting against the rear of the y-pipe (8 springs), so you do the math.  I ordered all 3 new gaskets and a set of Moose springs for the front.  The other 8 look fine.  Hopefully that'll do it. 

Think I'll take the spark arrester out and inspect the innerds of the silencer while I'm at it.

Thanks for the help.

[Sockman]

New springs and gaskets installed.  Not a cheap fix.  About $100 for the springs and new gaskets.  Hopefully that's the end of that issue.

[Sockman]

All fixed.  Forgot how quiet this thing was.  Sounds good again, funny how I got used to the louder exhaust.

[NMKawierider]

Good. Glad it's fixed.