Silencer help needed....

[SQUIRLEYMOFO]

On my 1990 KDX I decided to clean out the factory silencer. It came off easy enough the back portion came out easy. From the diagrams in the manual you push the front thru the rear? This is the problem. Any suggestions? Also is this supposed to be packed?

 

[twocycle]

I am just doing my 89. Each part comes out from different ends. I had to pry
gently with a screw driver to get exhaust pipe side out. There is packing inside
but I still do not know what can be used for replacment. The manual refers to it as wool.

 

[SQUIRLEYMOFO]

Maybe the 89 and 90 are different ? my aluminum part does not come apart on the exhaust side just the very end.

 

[twocycle]

I looked at kawasaki and the parts look the same. The whole thing is a
hollow tube with the parts inserted from either end. There 6 screws that
hold it together.

 

[SQUIRLEYMOFO]

No mine is not a hollow tube. Looks like a can open on the back closed on the front with a 1" hole drilled in the front where the pipe goes in. It is a factory spark arrest if that makes a difference.

 

[CaptainObvious]

Squirley, it sounds like you have the stock unit. If you have a lot of spooge in the silencer it bakes the silencer until all of the internal components are stuck. We’ll get you unstuck.

Disassemble by removing ALL of the 8mm bolts, the six in the back, the three on the front and the ones (I think there are four) on the side. Use pliers to remove the end-cap by twisting the exhaust pipe. There is a rubber seal behind this cap and, if the person who reassembled it last did a good job, some RTV as well.

After the end-cap is off the first section should slip out. You might need to give it a twist with your pliers. Getting the rest of the guts out is simple, but crude. Put the silencer on a bench with the open-end facing down. Place a wood block on the pipe and hit the block with a rubber mallet or something similar. This should cause the internals to brake loose and fall onto the workbench. If it is real spoogy in there get some carb cleaner and soak the inner walls of the silencer and let it sit for about 15 minutes. Then give it another whack. There is a rubber seal on the closed end as well.

Give it a good cleaning with oven cleaner and repack the silencer. I use red RTV on all of the mating surfaces including the bolt holes. This way it won’t leak.

If you are real ambitious, you can shorten the unit by 5 3/ 4 of an inch by removing the reverse flow area. It will give you as much power as any aftermarket silencer without getting much louder than stock. Best of all its FREE.

 

[SQUIRLEYMOFO]

Thanks! when you shorten the silencer do you lose the spark arrest ?

 

[CaptainObvious]

I would assume so. It still isn't a direct-thru exhaust since you are left with the vanes. It still says "Spark Arresting" and "Forest Approved". Once you get that thing apart and you see how much power is lost to the reverse flow section you'll run for your hack saw!

 

[twocycle]

Can insulation be used in place of the stock silencer material? They call it
wool in the manual.

 

[mcoker]

Originally posted by twocycle
Can insulation be used in place of the stock silencer material? They call it
wool in the manual.

yep

 

[twocycle]

Thanks!

 

[beefking]

I don't know about using home insulation, if that is what you are talking about. It is kinda loose, blows apart easily. I know the stuff you buy at a motorcycle shop works the best (generally) but if you wanna give it a shot go for it, I guess just pack it in really tight.

I just hacked my silencer apart today on ye old 89. Pretty easy actually! Just had to hack off the whole reverse flow section, cut 5.5-5.75" off the front of the alum. tube, then just drill 2 more holes for the connecting pipe in the aluminum canister. Easy squeezy! I can't wait to try it out, but I need a new piston first. :think:

 

[SQUIRLEYMOFO]

Alright I'm felling stupid do you cut the front or rear of the cannister and do you put the rear section back in? what are you calling the reversal chamber? do I elminate it or is it just the dead space? Thanks John

 

[CaptainObvious]

I knew I should have taken pictures of my silencer the last time I repacked it...

You are going to cut 5 3/4 inches from the open side. Actually, the amount of aluminum casing you are going to remove is the measurement between the screw holes. Mine was 5 13/16 I think. You will have to drill new holes in the aluminum casing. The holes that are now in the center section of the aluminum casing become the end holes.

The reverse flow section is the section closest to the pipe end. If you put the pieces on a bench you will see that the exhaust gasses enter the silencer, hit a baffle and then flow back towards the pipe end again. The gasses then enter another two pipes and travel into the forward chamber, again hitting a baffle and exiting a single pipe on the way towards the section that you pack with (for lack of a better term) packing material. This is the screened pipe section.

So lets label these parts so we’re clear on what you are cutting;

Entry Pipe – this is the pipe that comes from the exhaust pipe. It has the entire reverse flow section welded to it.
Baffle 1 – baffle section closest to where the entry pipe enters the silencer
Baffle 2 – baffle that contains the reverse pipes
Baffle 3 – screened pipe connects to this end
Vanes – heavy section that has a turbine look inside
End Baffle – holds the exhaust pipe

1. Cut the pipe at the inside flange of Baffle 1. Leave about 1/4 “ remaining. As you can see, this pipe is curved. By cutting the pipe at Baffle 1 real short you are removing the curve from this section.

2. Cut a section of pipe between baffle 2 & 3. You will use a straight section of the Baffle 2 & 3 pipe to connect Baffle 1 to the screened pipe.

3. Mark the outside aluminum casing and drill holes to secure the Vane section to the casing. This is the same distance as your original measurement. Use a small file to elongate the hole just as the section you removed.

4. File everything smooth. Remove all burrs from the cut pipes.

5. After you confirm that everything fits well together, repack the silencer and reassemble. The End Baffle will line up with the side holes that the factory drilled in the casing.

6. Use red RTV at all screw holes and at the end cap.

Let me know if you have any questions.

 

[SQUIRLEYMOFO]

Thanks! now I understand.

 

[NYkdxer]

I plan on doing something like that on my 89. The reverse flow section has to be taking power away. Instead of cutting the casing, I want to keep it stock looking. Does anyone sell perforated tubing? I want to replace the reverse flow section with perforated tubing and wrap packing around it.

As for the spark arrestor...Is it the turbine section? And is it really necessary (just wonderin, so don't bite my head off lol)? I can see why a 4-stoke may need one, but not a 2-stroke. MX bikes don't have s/a's right?

RV6, was there a noticeable increase in power? How much louder was it compared to stock?

 

[CaptainObvious]

It’s not much louder than stock. It seems to have a bit of an “edge” to it. It's quieter than my friends 220 with a FMF pipe! As far as noticeable power, I can’t comment because I did the modification while I was waiting for my cylinder to come back from being bored and ported. The bike now makes power everywhere but I can’t tell you how much of that is from the silencer. I’d guess very little.

I don't know what portion of the silencer provides the spark arresting. It most likely works as a complete system.

 

[mlhend1]

I found my KDX 200 overall power very noticeably increased when I removed the silencer material and everything within the shell of the silencer. I ran a cooper pipe (exact fit) through the silencer exit, through the silencer and connected to where the silencer meets my FMF Fatty pipe. I secured the cooper pipe to the end/exit of the silencer via steel Rivets. Without the cooper pipe added within the silencer my KDX ran poorly.

 

[mlhend1]

I also found the silencer/pipe combination not to be nearly as loud as some KTM with PRO CIRCUIT silencer.

 

[DeSeRt_KaW]

Can I ask a question?

I just bent my Stock pipe so badly that im going to get a new ProCircuit Platinum Pipe, Can anyone tell me how much power This new pipe will help me compared to the stock one?

 

[JasonWho]

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