apex yooper
Expert
SpartaSXr recommended putting RTV on donuts when replacing. I sounds like a good idea. Has anyone done it, and what do y'all think of that idea?
LJ 452
TY 4 Stroke God
I understand the theory however. I looking a the failure mode of my sled it appears that it's not a bad seal or the heat that degrades the donuts but more the flexing. The donuts are basically a wire mesh saturated and coated with some heat resistant and sealant aid compound. Because the exhaust is fixed in two positions beyond the donuts, I think a great deal of flex is absorbed by the donuts. If the tunnel flexes upward (which it will over any bump) the heavy rigid muffler puts a downward force on the rear of the Y-pipe connection. This then transfers to an upward force on the donut connection because of the Y-pipe mounting. So as the sled flexs up and down over each change in terain the exhaust donut essential gets two or more abrasive and or crushing motions. While the RTV may help with the abrasive part, the bottom line is when the size or shape of the donut is reduced to the point were the header contact the Y-pipe your going to wear through the pipe in no time.
SpartaSXr
Veteran
- Joined
- Apr 14, 2004
- Messages
- 32
- Age
- 64
- Location
- Western Michigan
- Country
- USA
- Snowmobile
- 69 SL351 - 70 SS396 - 98 V-Max 600 XT - 99 Phazer - 06 Attak
RTV
Dealer told me to add the RTV. Said It should have come from the factory with RTV on them. They have added RTV to all doughnuts being replaced.
Dealer told me to add the RTV. Said It should have come from the factory with RTV on them. They have added RTV to all doughnuts being replaced.
ReX
TY 4 Stroke God
Considering that area is likely glowing at least red hot when riding wide open, I can't see how RTV would handle the heat.
I didn't put any on mine.
The idea of grinding off some of the spacer to tighten everything up might not be a bad idea though. I left mine stock for now, but haven't finished putting everything back together yet (I could grind the spacer down to tighten them up a little still).
Right now I've been side tracked with a bunch of non-sled stuff...
I didn't put any on mine.
The idea of grinding off some of the spacer to tighten everything up might not be a bad idea though. I left mine stock for now, but haven't finished putting everything back together yet (I could grind the spacer down to tighten them up a little still).
Right now I've been side tracked with a bunch of non-sled stuff...
RX1-er-2005
Expert
RTV silicone disapate and absorb heat very well, I'd give it a try, I'll be checking mine at the end of the season for wear...
On my 2 strokes I use to put RTV silicone on the exhaust springs to reduce breakage and absorb vibration and it really worked...silicone doesn't burn and acts as a HEAT sink.
On my 2 strokes I use to put RTV silicone on the exhaust springs to reduce breakage and absorb vibration and it really worked...silicone doesn't burn and acts as a HEAT sink.
PreciselyRX1-er-2005 said:
Just be sure to use the "Ultra-Copper" RTV that is designed for that high heat application. Worked great on the 2-smokes.
ReX
TY 4 Stroke God
SledderSteve said:PreciselyRX1-er-2005 said:
Just be sure to use the "Ultra-Copper" RTV that is designed for that high heat application. Worked great on the 2-smokes.
I used to use Ultra Copper on my 2-stroke exhaust springs also, but this is a lot hotter than that.
Ultra Copper is spec'd for intermittent use up to 700°F. I expect these exhaust headers are well over 1000°F when running wide open throttle.
I wonder if anyone who has checked the temperature of the exhaust in this area can post with their measurements.?
Good point ReX, thanks for the clarification.
ReX
TY 4 Stroke God
Also thought I'd mention that the head gasket and head/header gasket runs a lot cooler than the location where these donuts live. You can use Ultra Copper on the head.
The head is cooled very aggressively by liquid cooling, but the exhaust is at maximum temperatures and still combusting a little as it exits through the header.
The head is cooled very aggressively by liquid cooling, but the exhaust is at maximum temperatures and still combusting a little as it exits through the header.
AttakDog
TY 4 Stroke Junkie
I'm a little concerned now about trying the Ultra Copper. This may just take up space, tightening the clamps up initially the melting away like it does on my old 2 stokes allowing everything to loosen up later. This should be a solid joint for the most part, thats the reason for the flex pipes up front.
