need help with exhaust

[lbo]

It's leaking and rusting.



I repacked the silencer about 2000 km's ago and it started to leak. So I took it apart and ran some rvt silicone sealant around the edges and gasket. This is how it appears after about 1000 km since I sealed it up and seems to come from the same spot as before. The inner packaging is still in good shape, should it be absorbing this grease? Also, noticed it doesn't rev WOT like before..... have lost 500-1000RPM's (sounds like) and wonder if this exhaust could be the culprit.

I want to paint the chrome with some hi-temp paint..... black. How should I prep it? Can I get a piece of sandpaper smooth it out, do I need some rustoleum or will that mess up the hi-temp paint?

[90GTVert]

If you are using copper RTV to seal the pipe and it is in good condition (it didn't get bent or otherwise damaged to cause sealing issues) I'm not sure why you can't get it to seal. Packing the silencer too loose or too tight can cause performance problems, it says that right on the packing material I used. It wouldn't suprise me to lose a little RPM from exhaust leaks given the nature of a 2 stroke.

When I frist started painting my pipe, it was because of rust as well. I've tried prepping different ways, but I get a similar result each time because of the temperature I suppose. A high temperature paint like the 1200 degree engine paint's you can get at auto parts stores or BBQ paint are your best bet for spray bombing it. I need to repaint fromt time to time to keep it looking good. THe main thing you probably want to do at this stage to prep, is sand out any existing rust.

[lbo]

Thanks man, it's dawg bone helpful.

I don't have an electrical sander/grinder.... I'll get what I can with 60grit? by hand. I didn't use the copper sealant (do for my nitro engines) I picked up some grey that works and met temp and grease oil specs. The leak is in the same area too, notice how it coats under the silencer tip. That's how it looked before I packed it with new filler, after new filler before sealant, and now after sealant. Not sure whats up. I'll just clean it and lay a thicker bead. Then follow up the inner bead with a ring around the outside.

Here's another shot of the leak and rust. How important is it to get most of the rust off? I just don't want it to mess up the hi-temp paint.

[90GTVert]

If you are just using one grit of sandpaper, I'd prob go with something closer to 200 grit. 60 grit will probably show a lot of scratches. I would say it is pretty important to get rid of as much rust as possible. It would take a long time to rust through or anything, but I just don't like the idea of sealing the rust in.

If that black stuff under the silencer is the oil... good lord. You must have one heck of an oil injection system or one oil rich pre-mix ratio. Otherwise, I wonder if it isn't something to do with the RTV itself melting or whatever. If it were oil from the engine, the packing material should be soaked judging from the way that ooze looks.

[90GTVert]

I guess I should note to clean the pipe well before paintung, using a solvent that will remove grease etc... I've used things like brake cleaner, alcohol, mineral spirits, and even plain old soap and water at times. Be sure the cleaner leaves no residue. Pretty basic and I'm sure you know that, but I hate to leave that out.

[lbo]

yeah, I think I will clean it first with denatured alcohol and/or brake cleaner. Then take CLR and some scotchbrite to get as much rust as possible.

I am confused with the silencer though. When I re-packed it I did it right, but it leaked. When I took it apart last time the insulation looked fairly new, it just wasn't absorbing anything. I sealed it up but must not have done a good job on it if it still leaks.

The Tecnigas Repacking kit shown here comes with 2 halves and some steel wool. I only use about ½ of the steel wool. Divide the half being used into two parts, laying one part into the recessed area of each piece of the fibrous material.

Position the stinger between the 2 halves of fibrous material containing the steel wool (like making a sandwich).

Slide the can over the stinger with new packing material, then place the end cap into the can. The end cap usually does not quite go back all the way into the can, but it will when you tighten the 3 nuts upon re-assembly.

So simple I doubt it's packed wrong, but something is causing it to leak and don't think it's running too much oil.... consumption hasn't changed that I can notice.

[90GTVert]

If it was injecting so much oil that it needs to run out like it is in the pics, your plug should foul or at least it should be incredicly obvious that you have a problem doing a plug read.

[lbo]

no, if anything my plug is on the white hot side which confuses me. I thought it was too lean a while back but it wasn't according to the local dealer, he said it was "normal."

This is how my plug looks just about everytime I do a chop;



On a side note I don't think the exhaust caused my performance problem. Got on it this AM and realized the rear tire was flat. I suspect I had a small leak, haven't check PSI in a while, and was losing some acceleration and top end.

[rallyrrr]

If you've been running your pipe for very long it may be advisable to de-coke it before cleaning and painting. Most people do this with a torch but certain solvents do okay. If you run wot quite a bit you might want to consider richening your mixture a bit. The tale I hear is light tan to cardboard colored for two strokes.

[90GTVert]

That looks too lean to me. I like light tan on a 4 stroke and caramel to chocolate for 2 strokes. I know other folks here have mentioned white plugs being normal. I'd rather see too rich than too lean. If it makes power on a racing engine, cool... but for daily street use it makes no sense to encourage running that lean to me. I'm no expert, I'm just paranoid about lean conditions after blowing about 5 head gaskets thanks to a lean condition (car not scoot).

[lbo]

^^^ yeah thats what I was thinking too. I had them open the main one size when I put the performance pipe on, that was 8000kms ago though. I am 500km short of 10K, I run it WOT most of the time and I take it for long stretches periodically too. Hoping I don't put a hole in the piston, been good so far and really impressed with Kymco quality.
looks for wood to knock on

[lbo]

Well I painted my pipe today!

I bought a spong sanding block and got most of the surface rust off, used CLR too. There was still a lot of rust the block wouldn't get off, it was smooth though.

I also re-sealed the silencer, learned there IS a difference between the copper and grey version. Both are high heat but the copper is 700 degrees, grey is 500. Also the copper should resist oils 2X as much, hopefully it's what I need.

Once my new rear tire arrives I will test it out. Thanks for all the tips/suggestions.

It looks better then the rusted oil covered chrome version posted earlier

[90GTVert]

Looks good. If you were worried about it, once the RTV is dry you can peel off the excess. Just makes it look clean.

[lbo]

yeah good call. I took a flat blade razor and trimmed up the edge. Now I am just waiting for that tire.