I had been getting a lot of movement in my pipes, quite possibly the reason I can't get them to seal! After spending hours cleaning up splooge after a large service I've decided I'll do my damnedest to make sure that I overcome it. This time it will work.

So, I noticed my exhaust mounting rubbers look a bit perished and sticking a rod in them and feeling the movement I can confirm there is a lot. How hard should these be? I am thinking of ordering some new ones. That, along with new engine mount rubbers, should hopefully help somewhat.
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MC21 Honda NSR250. TYGA 300 conversion.

Well, I just ordered a set. Hopefully they'll be a bit firmer.

The thing is the engine is going to move.
To a degree the pipes (if they're not bolted directly to the engine) are going to move seperately.

So if it's a roadbike (i.e. not apart every few hours of running) you need either top notch sealant or rubber rings on the inner flanges.

Charles is a clean freak and will be along shortly with pics of exactly what you need to keep the inner of your belly pan so spotless you can eat off it.
As for me I'll keep dropping the pipes and resealing them when they sound like they're blowing which in my experience is after less than one trackday.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

I am thinking, rather than putting an o-oring in there, I might try cutting some soft copper and using copper based sealant to finish the job off. Couple that with four springs per chamber and it should compress enough to give it a good seal, right?

Would this be better or worse than an o-ring? I figure it may give a better surface area.

Either that or machine two orings in? What would be better?

I really want to make sure!!! I spent hours cleaning splooge off the frame and engine and pipes and fairing etc etc.

Alright, so I've taken the flanges off that connect the TYGA pipes to the head. I inspected them to see where they were leaking and the definitive answer is EVERYWHERE that they could possibly leak, they are. That means both pipes were leaking between where the flanges mate with the head and where the flanges go in to the pipe.

So, my plan is to get two grooves machined to fit vitron o-rings between the pipe and flange and use a copper gasket between the flange and head.

I've got some sealant too. I haven't opened it so I can't confirm it isn't orange. It's called Permatex Ultra Copper RTV sealant, apparently it's good for use on turbocharged engines etc. to 700F/371C so should be good except for two things:

1.) It says "Not recommended for use on head gaskets or parts in contact with gasoline". This raises a few red flags as a two stroke exhaust is definitely going to be in contact with gasoline. Seems a bit stupid for something supposedly designed to seal exhausts.
2.) The word RTV is on there. Now, I don't know what RTV is supposed to mean but it was also on the orange crap that didn't do anything other than make a mess. So it this three letter acronym raised more red flags. I decided to wikipedia it. Turns out RTV is an acronym for Return To Vendor. I think that is what I might do.

They're thinking of things that see a lot of gasoline. The smear that is between your flanges won't be troubled. Most high temp sealants I've seen specify that, and they've been happily used on crank cases etc.

RTV stands for room temperature vulcanising. It just means that it's a silicone sealant that once you get it out of the tube, it starts to set. That's a good property for silicone sealer to have.

I'd say a two stroke exhaust sees a LOT of gasoline. Unburned fuel passes out in to the exhaust and is pushed back in by the returning pressure wave. Certainly a lot more gasoline passes through the exhaust on a two stroke than a four.

I just hope the copper stuff, if it is okay to use on the exhuast, is better than the orange poo. 100% failure rate with that stuff. Out of the six places I used it to seal the exhaust, it failed on every joint.

Anybody used it?

Anybody able to comment on my plan to use vitron and copper gaskets on the exhaust?

Don't use copper gaskets on the manifolds. Matt will confirm this for his pipe/manifolds. I have already asked him about this.
Just a thin smear of high temp silicon and bolt the manifold tight to the 300 barrels. Wipe off with your finger any silicon that squeezes into the exhaust.
I tried to cut an o-ring groove into my manifolds last week and failed, cut the groove too deep. I need more practice on a lathe. lol In my defense it was a pretty old crappy lathe and the chuck was way too big.
I've had a mate fill my failed groove with weld and dropped the exhaust, manifolds and o-rings into the machinist today.

Perhaps you did not read my post.

I have tried (more than once) with the orange RTV (Return To Vendor) silicone. It has leaked every time at all six joints (this includes the end cans). 100% failure rate. So I will be trying either copper gaskets or vitron rings unless someone has a better idea.

Did you clean everything spotless with alcohol, acetone or thinners before applying any silicon? Silicon doesn't stick to oily surfaces.

Yes, thinners. Three times each of the two or three time I refitted the exhaust. With a new rag between each of the three successive cleanings. So spotless, you could eat off it. I get asked this everytime I mention that the RTV doesn't work. Yes, I let it set for more than the time specified on the tube. Not interested in doing that again.

Really, there is no point in arguing that it works and I should give it another go. I am trying something different that has a chance of not blowing out in every single place that I applied it.


Last edited by anonymous.shyster on Thu Jun 16, 2011 8:37 am; edited 1 time in total

I had fairly good results with using just silicon. I am putting o-rings on my manifolds to try and get it 100% sealed.
My carbon cans started to slog out at the rivets, again. I have replaced the rivets with shiny mushroom socket head screws.
The inner perforated tube in my cans was also rattling about, wearing on the aluminum ends and causing a grey spooge to leak out of the exhaust end of the loose rivet joint. I used epoxy to glue the perforated tube into the end of the aluminum end cap to stop it rattling around. Hopefully another small problem solved.

Better quality silicon?
There has been a similar thread recently where i showed a picture of the silicon i use with good results. I'll find it.

This is the stuff I use.