Topic: will this hurt the exhaust valves?

[Buffo]

I had to remove the centerstand on my 1978 CB750K8 yesterday and started it without the muffler (the muffler was in the way of the big shaft that held it to the frame). It has a 4 into1 RC brand header and muffler setup, it came from the factory with 4 into4.

It sounded AWSOME! Very very loud.

It was ran with just the header. I was wondering if I chose to run the bike this way, would it hurt the exhaust valves...I have heard that some engines can't be run with out a complete exhaust. I dont even know if that story is true or not but the story went with horrors such as burned, warped or other wise heat destroyed exhaust valves. Are there any other pitfalls that may occur if I go this route?

I realize that I may need to re jet the carbs.

Don

[number13]

There is the thought that cold air could rush in and warp valves after
shut down, but i don't think I've ever actually known anyone with that problem.
I think your biggest problem will be not enough back pressure, basically it will
run like crap no matter hoe much re-jetting you do.

[Killer Canary]

R.C. is Russ Collins Engineering, isn't it? Where the Hell did you find that?

[eldar]

Hardf to say if it will hurt. Depends on how stock the engine is and such. They make drag pipes for these bikes and those are straight through. No real performance gain though. The pipe is probably best left on though.

[kghost]

Right......loud pipes save lives...........

Due to the nature of sound its extremely difficult for drivers to discover the direction you are coming from.

Loud pipes sound cool, but generally just piss off the neighborhood.

But I bet you don't here cam chain noise or clutch rattle now.

[Philly550K1]

hey -- i've got one of those RC 4-1's, too (or at least the megaphone, for sure).  yes, i think it's Russ Collins (RC Performance/Engineering) -- they make fuel injectors still, I think).  hardly anybody seems to know or care much about these pipes except you and me.  got a pic of yours?

[Buffo]

Im not looking to "gain" anything other than a cool sounding pile (Bike). however, I DON'T WANT IT TO TAKE PERFOMANCE AWAY. Will it? It seemed to idle pretty well, just as well as with the muffler on.

What if one made a coller that went on the inside of the header at the end of it. What size would the opening have to be to achive the proper back pressure? I would lke to avoid a muffler...I really dont care for my neighbors anyway.

If a muffler is the only way to go...what would be the loudest, best sounding muffler I could get...
I realize that the "best sound" is in the ear of the beholder.

And no you dont really hear much engine noise.

Don

[eldar]

well for volume, I would stick with the individual 4 pipe set up and get drag pipes. Using just the header may caue problems, using drags will extend the length and usually cause not trouble, with the bike anyways.

If you dont like your neighbors just rev the crap out of it at 3 AM!

[kghost]

And we wonder why the sport is viewed with consternation amongst outsiders.

I'm all for: Do what thou will shall be the whole law. You gotta have loud pipes, Go ahead. I'm not the noise police.

Me? I'll be the "you meet the nicest people on a Honda" person.

You think the loud issue doesn't affect you? Example:

I was apartment shopping in Michigan the other day. Looking for a crew crash pad in Belleville. When to see a upscale apartment complex that advertized 3 bedroom apartments. I was given a floor plan and a list of rules of the complex.
 Number 1 on the list? No Motorcycles allowed on the property!
Why? Too many problems with noise.

Too bad it was a nice place. I kept looking. Interesting though.

[eldar]

O dont know if they could legally do that?! It is a running vehicle not a heap.

[Buffo]

I ran my bike today (up and down the block a couple of times) and it seems to run pretty good with no pipe on it. It takes the thing about 10 minutes of warm up to want to idle at no choke, with or without pipe.

I set the pilot screws back at 1 1/2 turns.  I need to get a dwell meter so I can adjust them and the idle set screw properly. I think that is part of my problem with my throttle response. When I twist the throttle from idle it gurgles a little, kind of boggs down for a second. It likes to be eased out of idle with a couple 'o twists.

Don

[cd811]

no ,it want hurt your valves.
yes, I think it sounds cool
yes, different header co. make inserts for the megaphone end.
one of many downfall...
on a long trip the noise(vibration) will cause excess wear on you...
it piss's cops off..
upside...
it piss's cops off
lol
 

[the_genrl]

hey i heard of that "valve warping" as well. bologna if you ask me  . 

the excessive noise is neat, but i guess that i wouldnt care if it was electric as long as it books.  buy hey, if you want to keep it off just to be obnoxious, or just your everyday garden variety village idiot...meh why not?   thats pretty much what i do (seriously) in my yuppie town. 


that'll teach'em 

[TwoTired]

I believe the valve warping danger is really only for running the engine with NO header at all.  Cold air can then readily get to the exhaust valves. It is also more prevalent where large diameter valves are employed and where the valve head cools unevenly.
I believe drag racers discovered this. They removed the headers to save weight and then immediatley shut down a VERY hot engine after a run and at speed, blasting cold air into the exhaust ports.  Next run, the valves burned cause they were no longer closing completely.

[oldbiker]

I like the Rolls Royce approach. If you can't hear it , it must be a wonderful piece of machinery.

[Bob Wessner]

I like the Rolls Royce approach. If you can't hear it , it must be a wonderful piece of machinery.

Aside from my 750 of course  I've always had an affection for the twin jug beemers for this very reason.

[Philly550K1]

don, if the whole unit is a RC piece, they probably optimized it for performance.  but in what rpm range, for what kind of torque curve?  i wish we knew these things. (anyone? russ?)

is there a bolt in the megaphone, whereby you could remove its guts?  some combination of cleaning, removing, or replacing what you find may be your ticket.   

of course, how matched it is to your jetting is a whole nother thing to be thinking about.....

as far as the valves, too lean for too long would theoretically risk valve burnage, and less restriction may well lean you out.  just keep an eye on your plugs, i would say.....