Exhaust tape??!

[Squishman]

I am buying a 2021 Royal Enfield Interceptor 650 on Wednesday. It has very low miles. 600 ! But he has wrapped the exhaust all they back to the mufflers. I don't like the look so much. My questions are why? Does it benefit anything besides looks (in some people's opinion!) I cannot imagine performance. But someone here might know. And finally, with the very low miles, if I removed the wrap, would there be much or any staining. It may have been on for 3 years though.
Edit... I just noticed that I will have to change my profile photo! I'll wait until I get it this week.

 

[Jim]

My questions are why? Does it benefit anything besides looks (in some people's opinion!) I cannot imagine performance. But someone here might know. And finally, with the very low miles, if I removed the wrap, would there be much or any staining. It may have been on for 3 years though.

I don't know of any advantage on bikes. In a cramped engine bay, probably... but out in the open, I can't see any advantage.

Far as staining, you'll just have to pull it off and see. Iirc, the headers on a RE 650 are stainless, so they should polish out if there is any.

 

[Squishman]

That's good!

 

[Wingedwheel]

I used it because my stock exhaust was dented and rusty but very solid and I’m a cheap ass that would rather spend $20 than a few hundred until I know what I actually want. No advantage other than looks and oh yea, do not handle them without good gloves on…..

 

[Squishman]

Do you guys think this looks ok, good or heinous or this bike?

 

[Jim]

Do you guys think this looks ok, good or heinous or this bike?

Ugly as sin.

 

[Jim]

The wrap, not the bike. Love the bike...

 

[40north]

Yo Squishman!

By wrapping pipes the temperature of the exhaust gas is maintained better. This lowers the viscosity of the gas and improves flow and scavenging. Better seal with spray silicone and leave it alone, imho, provided the cat did a nice job. I would. I do not think wrapping right up to the head is smart...4 or 5 inches of steel chrome right next to head should show. My opinion, but hardly unique.

There are valid reason not to wrap, especially if not sealed, water and corrosion and the chrome goes way south. The headers are probably double wall - to take advantage of the heat conserving wall to wall plenary space, and keep the outside surface at temperatures consistent with the chrome stayin' pretty. I wrapped my 1340 Evo because those pipes are not double wall. I got a mess of cans of Si spray @ Pep Boys.

If your pipes are double wall, there's less advantage to wrapping. But it may prevent pain when the bike drops on yer leg, a little

Interesting site may be helpful...sleuth 'round there> http://www.nightrider.com/biketech/calc_exhaustlength.htm

 

[DogBunny]

The local highly and truly knowledgeable XS650 guru (Chris Kelland) thinks that wrapping an XS650 leads to burnt exhaust valves because of the heat retention. He claims to have seen this more than once. On the other hand, mine has been wrapped for years (for cosmetic reasons, rusty headers). One key, on a double-walled XS650 in any case, is to not cover the little vent holes on either end of the header.
On your mostly black, mostly non-chrome RE, I think the black wrap looks okay, except the wrap job is terrible. Take it off, and if the pipes won't acceptably polish up, you could always re-wrap them, and do a better job of it.
Although the bike looks great, who knows what you'll find under the wrap. Maybe scrapes and/or dents.

 

[Jim]

The local highly and truly knowledgeable XS650 guru (Chris Kelland) thinks that wrapping an XS650 leads to burnt exhaust valves because of the heat retention. He claims to have seen this more than once.

I'd respectfully disagree. Exhaust valves cool through heat transfer across the valve face, into the seat. In other words from the valve itself into the head. From what I've always been taught, the main reason valves burn is from carbon buildup preventing or limiting that metal to metal contact and heat transfer.... letting the valve overheat.
Any excess heat buildup in the header would be downstream of that anyway and have little or no impact on the metal to metal transfer, so I fail to see how it would be a factor.

 

[DogBunny]

I'd respectfully disagree. Exhaust valves cool through heat transfer across the valve face, into the seat. In other words from the valve itself into the head. From what I've always been taught, the main reason valves burn is from carbon buildup preventing or limiting that metal to metal contact and heat transfer.... letting the valve overheat.
Any excess heat buildup in the header would be downstream of that anyway and have little or no impact on the metal to metal transfer, so I fail to see how it would be a factor.

I agree with you, and my own case study backs this up. Just passing along Chris' belief.
Yours is a good explanation, I'll share it next time I see him. Maybe he thinks it happens on shut down? And that the wrap keeps the heat in, and I guess if you had an open valve the heat transfer cooling into the head wouldn't occur? Sounds crazy to me, and I'm just speculating on his thoughts, but I'll see what he says.

 

[Its been a long time]

I have seen a good number of header pipes cracked under wrapping. The wrap causes the steel to overheat and that causes cracking. The only justifiable reason I can think of for wrapping a bike's header pipes is to hide damage. Personally, I would insist the wrap is removed and I'd inspect the pipes carefully before buying. If that's not possible, factor a set of head pipes into the purchasing budget.

 

[40north]

I wonder if the wrapped pipes under which cracks were found don't work the other way. If they were cracked maybe some fella wrapped them to conceal the cracks? Yeah, probably not. In any case, weld up the cracks and re-wrap? At one time I was in the foundry racket. Union steelworker. Made steel, made iron castings, also bronze and aluminum...brutal work. Great men! Heat did not cause cracking, simply softening and melting. However rapid cooling did create cracks. So did incipient stress when Fe alloys were heated... it was not the heat, but the hidden stress pulling the soft metal apart as it weakened. This is verifiable with a torch applied to a piece of steel in tension...as the transition temperature is approached crack will appear. Ok...headers, double wall or not, are bolted solid and they expand and shrink - thus they are in stress, and they are hot. Mechanism of cracking is obvious. Double wall and the stresses get complex. The inner wall expands faster and more than the outside wall, and in a rapid shut down? Perhaps the inner cools faster, rarely. Anyway the double wall fights itself. See, if you like "The Knight Foundry" on YT... it's all gone now, and the videos are from after I left. Most of the work is getting ready. Pouring is fun, but it's not where the hard work is. 4 days work, one day pour...go to bar. Kaiser Fontana? Brutal. Finks sold it to China, laid everybody off... Gone like the East Wind blows.

Can you describe the cracks you have seen, please? Radial, axial, both, etc? These ought to tell their forensic history by inspection. Has anybody seen the inner wall crack? I imagine a jet through an inner wall crack might burn a very hot spot, with the result a profound weakening in one area, in a pipe under tension.

To prevent melting of my shoes I made a pair of stainless shields covering the pipes at area of foot pegs on the old street tracker. I left clearance for wrapping from 5" away from head to the snuffers on the short tail pipes...over a pair of very nice 10" mufflers, engineered mufflers not ad hoc... I studied. There are 2 matters going on in exhaust, supersonic shock wave and also elastic flow. These go all over the map on a motorcycle engine. It's complex...well, it'll hurt your head. Mine workd out nicely...and took 2 weeks to complete. LOFW !

Kudos for mentioning the vent holes in DW pipes. I forgot that.

The Si coating I used, and keep, came from Pep Boys, iirc...PN 010301 "D I Engineering HI TEMP SILICONE COATING" It's black. 12 OZ per can. I got a dozen, spendy for old feller. Ya never know what will be prohibited in our eversofree zone! It cures very slowly at STP, better in oven...but most fellas cure it on the scooter...carefully...you can fubar the job if you don't take time to cure by increments.

Other than esthetic, art, mostly, none of this matters very much outside the engineering and production departments @ Luckup Motor Co. Just ride and live happy. The question was a pregnant one. Ah rekon y' got more than you expected! Best! 40N

 

[RC4MAN]

Seems to be popular among the Brat and Bobber types, several on the V-Rod forum have done it, many to bad result. Seems in some cases it causes cracking of the head pipes near the port exit due to excess heat causing metal embrittlement and fatigue.
A buddy who got out of riding a few years back because he was no longer confident on 700 lb cruisers picked up a used Kaw EN500 which the PO had wrapped. I removed the stuff, USE GLOVES, and it had ruined the chrome on the pipes, he managed to find some used take offs on ebay which he bought and I swapped out for him.
BTW, nice looking ride.

 

[40north]

Seems to be popular among the Brat and Bobber types, several on the V-Rod forum have done it, many to bad result. Seems in some cases it causes cracking of the head pipes near the port exit due to excess heat causing metal embrittlement and fatigue.
A buddy who got out of riding a few years back because he was no longer confident on 700 lb cruisers picked up a used Kaw EN500 which the PO had wrapped. I removed the stuff, USE GLOVES, and it had ruined the chrome on the pipes, he managed to find some used take offs on ebay which he bought and I swapped out for him.
BTW, nice looking ride.

Embrittlement in steels is generally due to hydrogen. Source being water, steam, dissociation of the H20, atomic H gets into the crystal structure. Re-heating tends to remove the H, but over time...and small cracks are part of the oxidation, rusting, process.

Agree! fiberglass is nasty. Gloves. Do not breath the bits-dusts...well, not if you are young...they get in lungs and stay there making woopie. Tumor removal from lung is great fun, I assure you.

 

[AUTOMAN]

Yo Squishman!

By wrapping pipes the temperature of the exhaust gas is maintained better. This lowers the viscosity of the gas and improves flow and scavenging. Better seal with spray silicone and leave it alone, imho, provided the cat did a nice job. I would. I do not think wrapping right up to the head is smart...4 or 5 inches of steel chrome right next to head should show. My opinion, but hardly unique.

There are valid reason not to wrap, especially if not sealed, water and corrosion and the chrome goes way south. The headers are probably double wall - to take advantage of the heat conserving wall to wall plenary space, and keep the outside surface at temperatures consistent with the chrome stayin' pretty. I wrapped my 1340 Evo because those pipes are not double wall. I got a mess of cans of Si spray @ Pep Boys.

If your pipes are double wall, there's less advantage to wrapping. But it may prevent pain when the bike drops on yer leg, a little

Interesting site may be helpful...sleuth 'round there> http://www.nightrider.com/biketech/calc_exhaustlength.htm

Wrapping the pipes insulates.
More heat is retained. So viscosity goes UP! Density goes down.
This maintains velocity of exhaust more evenly to tune the pipe easier.
Little tuning tweaks for race bikes.

 

[WideAWAKE]

Usually on a bike it’s on there for 1 of 2 reasons - hiding something or trying to look cool.

Works good for hiding stuff - doesn’t look cool haha.

If it was done properly (usually none of them are) then it would be water dipped and after it’s dry sprayed with a silicone heat wrap paint, which if used, it would leave black on the pipes. It would also most likely clean off.

Heat wrap and flat black just seems to scream EbayRacer.

 

[40north]

Wrapping the pipes insulates.
More heat is retained. So viscosity goes UP! Density goes down.
This maintains velocity of exhaust more evenly to tune the pipe easier.
Little tuning tweaks for race bikes.

Well, I would like to agree. And you may be correct. I think, in fact, that old feller misremembered, it's the speed of sound that I was confusing. I see>" The speed of sound depends on the state of the gas--more specifically, the square root of the temperature of the gas. The speed of sound (a) is equal to the square root of the ratio of specific heats (g) times the gas constant (R) times the absolute temperature (T)." (bold as found, not mine

There's flow, and reverse flow, and supersonic wave as well as pulsing flow, some slugs back through open exhaust acting as supercharge.. man long long time sine I studied this. Memory...

 

[AUTOMAN]

Well, I would like to agree. And you may be correct. I think, in fact, that old feller misremembered, it's the speed of sound that I was confusing. I see>" The speed of sound depends on the state of the gas--more specifically, the square root of the temperature of the gas. The speed of sound (a) is equal to the square root of the ratio of specific heats (g) times the gas constant (R) times the absolute temperature (T)." (bold as found, not mine

There's flow, and reverse flow, and supersonic wave as well as pulsing flow, some slugs back through open exhaust acting as supercharge.. man long long time sine I studied this. Memory...

Juxtaposition in time warp. A turbo encabulator should help resolve time/phase shifts on the spheroid valve.

 

[RC4MAN]

Juxtaposition in time warp. A turbo encabulator should help resolve time/phase shifts on the spheroid valve.

Blame it on the flux capacitor