Exhausting afternoon

comnoz · Jul 5, 2015

I got tired of looking at my old dented up pipes so I pulled out the stainless header kit I picked up on e-bay a couple years ago.

And started tacking things together

key stock and hose clamps work great for aligning pipes till tacked up.

Now to get that last joint lined up.

One side down -one to go

Looks a little different now. I think I am going to like it.

madass140 · Jul 5, 2015

what diameter Jim? I just made a set "S" type style 1-1/2" Dia.

comnoz · Jul 5, 2015

madass140 said:
what diameter Jim? I just made a set "S" type style 1-1/2" Dia.

They are 1 1/2 inch.

The old ones were 1 3/8th inch for 18 inches and then stepped up to 1 1/2.

The motor is bigger than when I designed the old pipes so hopefully I will not loose to much midrange. Jim

cjandme · Jul 6, 2015

comnoz said:
I got tired of looking at my old dented up pipes so I pulled out the stainless header kit I picked up on e-bay a couple years ago......
Looks a little different now. I think I am going to like it........

Looks good, Jim. That's quite an E-Bay find !

MikeG · Jul 6, 2015

Looks Nice Jim...two questions: can you still fit a center stand?? and what is the hose coming from your crankcase breather for? I eliminated that when I put on a really slick unit that screws into the sump plug

comnoz · Jul 6, 2015

MikeG said:
Looks Nice Jim...two questions: can you still fit a center stand?? and what is the hose coming from your crankcase breather for? I eliminated that when I put on a really slick unit that screws into the sump plug

No center stand. I do have a re-enforced sidestand and carry a piece of rope so I can pull it over to a post and change a tire if needed.

The hose to the end of the cam is oil to the rifle drilled cam. It feeds oil out through the lobes. Jim

CanukNortonNut · Jul 6, 2015

Jim,
Is it a 2 into 1 back into 2? Pictures? 8)
Cheers,
Thomas
CNN

comnoz · Jul 6, 2015

CanukNortonNut said:
Jim,
Is it a 2 into 1 back into 2? Pictures? 8)
Cheers,
Thomas
CNN

It is the same from the flexible coupling under the engine on back as it has been for a long time. I just replaced the headpipes. It is still two into one and back to two.

acotrel · Jul 6, 2015

Jim, Looks good. How will you keep the noise down without stifling the motor ? I've found that to get the most out of the system. the cross-sectional area if the tail pipe has to be at least the same size as the total cross-sectional area of the two header pipes. A restrictive muffler seems to kill off the top end of the rev range. I use an absorption muffler with no baffles, and the bike is far too loud for street use. The benefit is that the bike pulls like a train.

comnoz · Jul 6, 2015

The two headpipes feed into a venturi style collector of 1 3/4 inches diameter. From that it tapers back up to two 3 1/2 inch pipes feeding into glass packs of 2 inch ID. It is actually pretty quiet.

I played a lot with different collectors on the dyno before I settled on what I have. I originally built the collector with the ability to use an insert of different sizes. After testing I welded the insert in place. Jim

acotrel · Jul 6, 2015

When you did the dyno testing while changing the collector ID, did you find that some changes gave an overall drop in power, or were there changes in power over certain parts of the rev range only ?

comnoz · Jul 6, 2015

acotrel said:
When you did the dyno testing while changing the collector ID, did you find that some changes gave an overall drop in power, or were there changes in power over certain parts of the rev range only ?

I went just large enough to get peak power. Going smaller reduced power at the peak. [ the peak was 7600 rpm with the 880 motor]
Going larger didn't make much difference in the peak power but hurt the power at 5000.
This was done with my old 880 cc motor -It may not be optimal now with the 914cc motor. Jim

Hobot · Jul 6, 2015

I have head Comnoz Cdo a couple of times and its distinctly louder than average but also deeper so more pleasant louder than obnoxious louder. Just saying in case others think peak power exhaust system can be quiet as factory.

jim I do hope you took into account stoppie level breaking with cargo or big speed bumps or water rut cut so fork bottom so mudgaurd missing could strike the headers. If steel mudgaurd it may adapt to clear fine afterwards...

acotrel · Jul 7, 2015

comnoz said:
acotrel said:

When you did the dyno testing while changing the collector ID, did you find that some changes gave an overall drop in power, or were there changes in power over certain parts of the rev range only ?

Click to expand...

I went just large enough to get peak power. Going smaller reduced power at the peak. [ the peak was 7600 rpm with the 880 motor]
Going larger didn't make much difference in the peak power but hurt the power at 5000.
This was done with my old 880 cc motor -It may not be optimal now with the 914cc motor. Jim

That is pretty much what I suspected, however I've never had the means to measure the response to changes in the exhaust system configuration. When I made the exhaust for my 850, I simply built on what I'd learned when trying to get more torque out of my 500cc short stroke Triumph. I find it interesting that your system, Bernds and my own have ended up looking very similar - same large diameter tail pipe. I've seen a few with the same diameter tail pipe as the header pipes,- I don't think that works very well. Also, I think for best, the header pipe length has to be the tuned length to suit the cam timing and the revs.

comnoz · Jul 7, 2015

Here are some better shots of the exhaust system details

Here is the flex coupler. You can see how it is mounted to the bottom engine case stud. The large brass nut compresses a graphite/asbestos rope packing that allows the headpipes and muffler to move independently.

Here you see where the two pipes join in a merge collector that goes into a tapered pipe that has an ID of 1 3/4 inches. The collector has an outer shell covering that is welded on for strength. The inner pipe is quite small.

The collector dumps into a 3 inch diameter U-shaped pipe that is hollow up to the last 10 inches where there is a glass packed muffler.

worntorn · Jul 7, 2015

The exhaust looks great.

Is that a MK3 rear wheel hub you have used?

Glen

comnoz · Jul 7, 2015

worntorn said:
The exhaust looks great.

Is that a MK3 rear wheel hub you have used?

Glen

Yes, it's a mk3 hub with my own cush drive and sprocket hub. jim

brxpb · Jul 9, 2015

Jim, are your silencers mounted similar to Ludwig's headsteady loosely on those nylon washers, if they're rigid how do they not vibrate off?

comnoz · Jul 9, 2015

brxpb said:
Jim, are your silencers mounted similar to Ludwig's headsteady loosely on those nylon washers, if they're rigid how do they not vibrate off?

I made the Z-plates with a 1 1/2 inch hole in them. There is a rubber biscuit with a steel spacer in the center and a teflon washer on each side. Kinda like an isolastic muffler mount. Jim

Son of Siredward · Jul 13, 2015

Jim, did you happen to put it on the Dyno before heading out. I see you have a pretty good radius right off the head. We discussed that you found in the past that when you have done this you picked up a few HP. BTW I like the routing....

Exhausting afternoon

comnoz

madass140

comnoz

cjandme

MikeG

Mikeg

comnoz

CanukNortonNut

comnoz

acotrel

comnoz

acotrel

comnoz

Hobot

acotrel

comnoz

worntorn

comnoz

brxpb

comnoz

Son of Siredward

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