Topic: Using drag pipes temporarily

[Cevan]

The resto of my K1 500/4 is complete but for the exhaust.  The Delkevic 4 into 4 I ordered has been delayed a couple of months now and probably for another two months.  The exhaust that came with the bike was a 4 into 1 that was badly rust at the collector and muffler so I cut the pipes just before the collector, making my version of drag pipes.  I used these pipes when I ran the engine on an engine stand and now on the bike.  I haven't ridden the bike more than a few hundred yards as I sort out some electrical issues. 

Question: Any harm running these now with stock carbs and jetting?  (other than to my ears)

[pjlogue]

Buy earplugs!

I suspect you may need to jet the carbs differently.  Most "stock" four stroke street engines need some back pressure to run properly since they are designed for a street legal muffler.

-P.

[Tracksnblades1]

The resto of my K1 500/4 is complete but for the exhaust.  The Delkevic 4 into 4 I ordered has been delayed a couple of months now and probably for another two months.  The exhaust that came with the bike was a 4 into 1 that was badly rust at the collector and muffler so I cut the pipes just before the collector, making my version of drag pipes.  I used these pipes when I ran the engine on an engine stand and now on the bike.  I haven't ridden the bike more than a few hundred yards as I sort out some electrical issues. 

Question: Any harm running these now with stock carbs and jetting?  (other than to my ears)

You’ll know how good your points are set and your carbs are..?

[HondaMan]

Check you sparkplug's color after 50-100 miles to see if they are still chalk white. If so, it's running pretty lean. In the short term you can up the octane in the gas tank (run premium grade fuel) which only helps about 3% or so, but it might restore some color to the plugs and cool down the exhaust valves a bit.

Still: in the 500/550 I have not ever seen a burned exhaust valve. In 1973 my brother and I took off on a tour together: he had the 500 then. About 40 miles from start, the #3 pipe on his bike launched the entire muffler guts out onto the interstate (causing the car behind him to become quite testy!) and while I was about 200 feet ahead of him, I thought someone was shooting off fireworks near us - or something. We stopped: he walked back and (uh-oh...) picked up the silencer parts out on the hiway, immediately throwing them straight up in the air, and when they landed he kicked it off to the side of the road. I was about 100 yards ahead of him watching this comedy: when he caught up with me I asked him what he was doing, and he showed me nasty burns on both hands from the silencer parts!

Yeah, they were hot...

But, we rode almost 4000 more miles like that and then he rode almost 1000 miles more to get back to Missouri. When he got a new set of mufflers (they were all getting similarly rusty) he did a compression check: the #3 cylinder was still like the others, all within 5 PSI of each other - no burned valve occurred in the whole trip, despite the noise. He rode that bike until 1979 when he bought a CB650 SOHC4 instead (which he soon traded for a Gold Wing).

[Cevan]

Here's a picture of the bike to give you an idea of the length of the pipes.  I don't want to deal with re-jetting if these are just temporary.  I don't plan on doing much more than riding around my immediate area to just sort the bike out. 

[seanbarney41]

I would guess that will run poorly with stock jetting and there is not a wide enough array of turning parts for the 550 to get that acceptable.  But without some rather complex formulae and the data to plug in to them, there is no way to know other than just riding and see.  In my experience the length of the pipe has a much greater effect on jetting than the baffling (or lack thereof)  So if you have problems, any length you can add will change the situation.

I don't think there is any danger of damaging the engine UNLESS you get very lean plug readings and/or work the engine very hard.  Please don't enter the bike in any tractor pulls lol

[HondaMan]

I don't think there is any danger of damaging the engine UNLESS you get very lean plug readings and/or work the engine very hard.  Please don't enter the bike in any tractor pulls lol

..or roadraces!

[Tracksnblades1]

She’ll tell you if she wants a change by turning them deep blue first…😏

[Don R]

 We used to adapt VW beetle exhaust tips to some cut off pipes. They're harder to find these days but it made the bike a little easier to live with.

[willbird]

On a V8 we might call those "zoom tubes" or "zoomies". To keep my basic understanding simple in a normal header part of the intake charge of fuel and air goes from the intake through the cylinder, passes down the exhaust pipe, then a return pulse draws it back into the cylinder before the exhaust valve closes.

A short tube like that means that that fuel air never gets to turn around and go back up the pipe....it just dumps out into the atmosphere. A pipe that short might be "tuned" for about 20k rpm maybe :-). In the more primitive days the tuners looked inside a "too long" pipe and described how to see that reversion point in the soot inside the pipe and then would cut the pipe so it was some distance like 1" longer than that.

People sometimes use zoom tubes now with a centrifugal supercharger on car engines, with 40-80 lbs of boost tuning the length of the header tubes is a rounding error LOL as far as adding horsepower.




Bill

[HondaMan]

We used to adapt VW beetle exhaust tips to some cut off pipes. They're harder to find these days but it made the bike a little easier to live with.

I'd forgotten all about that! It was a popular mode, on lots of the Hondas. It sounded much like the OEM upswept pipes on the CL77, too.