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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 703182 times)
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wobblywalrus
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« Reply #735 on: March 25, 2012, 12:34:37 AM »

How does a person flow test a jet?

The local experts on jetting these flat slide carbs say "Jet for best power.  Do not jet for what you think is the best mixture."  The procedure is to increase jet sizes incrementally until the power drops.  Last year #140 jets were the best and power dropped when bigger ones were installed.  This year #145 jets are best.  I figure I have a few more horsepower based on this increase in jet size.  The mixture that produces maximum power is leaner than normal.  That is the nature of this engine and it has always been like this.

The power curve drawn on the graph for 2012 is an average of five pulls.  The bike makes four more horsepower.  That is reasonable considering it went up two sizes on the main jets.  The bike runs a lot better on the street in low to mid range rpm.  There was a lag in the power curve at just under 4,000 rpm.  The lag is much less now.

Changes since last year are the modified intake bells, larger air cleaners, polished and matched intake manifolds, and the ignition module.  The goofy jets and the clutch problems used up a lot of time and we did not get good runs in to test the intake mods and module separately.



* 2012 Dyno Session 7.jpg (150 KB, 768x1000 - viewed 115 times.)

* IMG.jpg (256.82 KB, 768x1009 - viewed 119 times.)
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wobblywalrus
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« Reply #736 on: March 25, 2012, 12:08:37 PM »

A lean condition occurs when the throttle is opened suddenly on a slide carb.  The engine stumbles and the bike does not accelerate.  One cure for this is to make the low speed mixture a bit rich so it is not overly lean when the throttle is opened.  This setup makes a polluting mixture and the extra fuel is detrimental to engine life.  Another cure is to open the throttle slower so the mixture does not go lean.  This works well.  The low speed mix can be set at a leaner ratio and the engine runs cleaner and lasts longer.  More solutions are constant vacuum carbs or fuel injection.  An accelerator pump on a slide carb is an option, too.  It squirts in a little extra fuel when the throttle is opened quickly.

These Keihin flatslides have an accelerator pump.  This engine does not like the rich mixture the pump provides and it runs best if the pump is disconnected.  I keep the pump operational for starting on very cold mornings only.  Twisting the throttle once or twice squirts in some extra fuel and this makes starting easier.  This is how I set up the pump.

The linkage is shown in the photo.  A little piece of bent brass welding rod is the linkage.  The rod is made long to start and I gradually grind it shorter until I get the length I want.  A shorter rod delays when the pump activates.  The fuzzy photo shows this.  The third photo is taken outside where it is safe to do this.  The fuel tank is on a picnic table above the photo.  The fuel line is connected to the carb and I turn the throttle by hand.  The rod length is adjusted until the pump goes on when the throttle is 1/4 to 1/3 open.  Fuel squirts from the little brass nozzles in the carb venturis when the pump is working.

There are various opinions about having the accelerator pump hooked up during dyno testing.  Some operators say they know how to ignore the pump's influence on mixture.  Others want it disconnected.  My assumption is I do not know, and if the pump richens the mixture during the dyno work, the selected jets will be too lean for sustained steady state running.  This could make an engine failure.  Disconnecting the pump during dyno testing seems to be the safer option and I do this. 


* 2012 Dyno Session 8.JPG (137.76 KB, 640x427 - viewed 106 times.)

* 2012 Dyno Session 9.JPG (123.38 KB, 565x480 - viewed 93 times.)

* 2012 Dyno Session 10.JPG (154.54 KB, 640x478 - viewed 116 times.)
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Koncretekid
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« Reply #737 on: March 25, 2012, 01:20:36 PM »

Bo,
Four more horsepower is a significant increase, especially considering the minimal changes you have made.  Unfortunately, you and I and most people end up making several changes between runs (dyno or salt flats), so we don't really know which change made the biggest, or any difference.  Such is life.

I, too, have a pumper carb, and was plagued with bogging between gear changes.  I blamed it on overly large intake passages (velocity too slow in ports?), but I don't really know.  I went from 36mm ports to 40mm, so maybe too much change at once. Such is life!

Tom
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Jon
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« Reply #738 on: March 25, 2012, 02:37:17 PM »

Bo; is the accelerator action pump spring loaded ?
Can you change the duration of the hit by putting different size jets in?

Bo & Tom; have you looked into quickshifters same as they run on circuit racing?
IMHO they're main benefit is not from the microseconds it saves from not having to pull in the clutch, I see 2 main other benefits.
Intake velocity and mixture, because you don't close and reopen the throttle velocity in the intake is maintained and your mixture isn't going all over the shop.
You engage the clutch once to get off the line then leave it alone which has to help it live longer.

My 2 cents anyway
jon
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wobblywalrus
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« Reply #739 on: March 26, 2012, 12:10:06 AM »

Jon, today I was monkeying around with the exhaust baffles and I cured the carburation problem.  Bikes are strange creatures.  It runs OK now.  Actually, it runs really good.  I will post what I did.

Tom, try adjusting the linkage to the squirters or their jets.  Maybe they are opening too much too soon or not enough and too late.         
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Koncretekid
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« Reply #740 on: March 26, 2012, 08:34:54 AM »

Bo & Jon,
If only I had my own test track! (or dyno) Pretty tough to try to tune out the carburetor issues on a bumpy 1/4 mile driveway with 100 feet of elevation change, especially with 15* of steering, 72" wheelbase, and no front brake.

As for quick shifter, probably a good idea, if I could find a reasonable solution that would work on the BSA.

Tom
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We get too soon oldt, and too late schmart!
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wobblywalrus
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« Reply #741 on: March 26, 2012, 11:46:30 PM »

Colorado has dynos in some cities that are near the same elevation as the salt flats.  Some sessions there might be helpful.  Seven feet long is shorter than some touring bikes I see now.

A big lesson was learned in 2007.  It was record inspection time and I needed to remove the cylinder head for the bore and stroke measurements.  It was getting late and I could not get it off.  It was hung up on the exhaust pipes.  I needed to remove the pipes.  This required pulling off the fairing.  To do that I needed to remove the forks.  The wheel and fender had to come off before I could do that.  The problem was solved by not removing anything and using a big hammer and prybar to bend things out of the way to extract the head.  The exhaust cross-over pipe was the problem.  There was not enough room to spread the pipes apart and to disconnect them so they could be moved out of the way.  I needed a set of pipes with no cross-over tube.

A few months later I was fondling a set of Arrow pipes at the Triumph dealer.  I could not afford them.  I liked to feel light weight and the smooth and sleek titanium.  The owner swooped in and made me an excellent offer.  Some bonehead customers dented these pipes and they could not sell them as new.  The dents matched all of the other dents on my bike.  Soon they were mine.

These pipes are made to work with the standard Triumph cams and they do this well.  I have racing cams and they would work great with the baffles out and the bike would barely run with them in.  I replaced the constant vacuum carbs with flatslides and this helped.  Then I cut the baffles apart.  The first picture shows the inside of the pipe.  A fixed baffle was in there.  I cut them it out and now there is a 1.5 inch diameter unobstructed tube down the middle of each muffler - like a straight through glasspak muffler for a car.  The removable baffles were cut in two.  One is in the second picture.  The little baffles work, barely.  There is bogging when I open the throttle suddenly, the engine runs a bit rough, and fuel mileage is in the low 40's.

The end of the tube in the little baffle projects into the exhaust flow.  This projecting end has the worst flow characteristics.  A hole with a tapered opening would flow much more gas with the same back pressure.  That was the first thing to fix - make the openings tapered in the new baffles.

A sound wave coming out of the pipe and passing through an open end reflects a wave back with the opposite polarity.  In other words, a pressure wave is reflected back as a vacuum wave.  A solid obstruction reflects back a wave with the same polarity.  A pressure wave is reflected back as a pressure wave.  The opening in the short baffle is small and it reflects a small wave of the opposite polarity.  The obstructed area is large and it reflects a stronger wave of the same polarity.  This same polarity wave discombobulates the carburetion and causes all sorts of problems.  That was the second thing to cure.  The baffle needs to be made so the tuned length reflecting the opposite polarity wave is where it was originally.  The baffle needs to have a different tuned length that reflects a wave of the same polarity.  Both the reflected vacuum and pressure waves need to arrive at the upstream end of the pipe at the a same part of the cam overlap cycle.  Picture 3 shows the new baffle from the side.  Note the different tuned lengths.  The opening that reflects the same polarity wave has a different tuned length than the opening that reflects the opposite polarity wave.   


* Exhaust Tuning 7.JPG (111.92 KB, 640x427 - viewed 99 times.)

* Exhaust Tuning 8.JPG (146.44 KB, 531x480 - viewed 89 times.)

* Exhaust Tuning 9.JPG (152.13 KB, 640x417 - viewed 99 times.)
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wobblywalrus
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« Reply #742 on: March 27, 2012, 12:02:53 AM »

This fourth picture shows the baffle from the upstream end.  Note the more efficient tapered opening.  The taper reflects the wave of the same polarity.  Its tuned length is shorter.  The fifth picture shows the baffle from the downstream end.  The opening that reflects the wave of the opposite polarity.  The internal diameter of the holes in both the long and short baffles are the same.  Do these new baffles work?

The bike runs much better on the street.  The dyno chart shows that both baffles cut down the power at the 3 to 4 thousand rpm range I use on the road.  The loss with the long baffles is less.  The long baffles work much better at mid range.  Both work about the same at top end and they are as good as the open pipes.  Strange.  A person would think that they would hurt power there.  Next year I will make baffles with different length tubes between the bells and the ends.  Then they will be compared on the dyno.

The pipe expert told me to start with a known good system, make incremental changes and test them, and do not assume anything.  He is correct.  Things in reality do not always work like we think they will.         


* Exhaust Tuning 10.JPG (114.63 KB, 496x480 - viewed 108 times.)

* Exhaust Tuning 11.JPG (125.49 KB, 638x480 - viewed 97 times.)

* Exhaust Tuning 12.jpg (161.8 KB, 735x1024 - viewed 106 times.)
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wobblywalrus
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« Reply #743 on: March 27, 2012, 10:25:56 PM »

These are the horsepower and mixture curves for the baffles.  This explains why the accelerator pump makes the bike run worse.  This carb setup runs richer when the throttle is opened rather than leaner.  The pump was not connected when this dyno pull was done.

Baffles inside of pipes are not an optimal way to quiet a bike down and make power.  A collector system with a can muffler would give me the correct tuned lengths, good noise control, and minimal flow restriction.  The baffles are a "make do with what I have" solution until I can fabricate something better.     


* Exhaust Tuning 13.jpg (138.04 KB, 737x1024 - viewed 95 times.)
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Koncretekid
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« Reply #744 on: March 27, 2012, 10:41:40 PM »

Interesting curves, but strange.  Just think how much more you could learn with some carburetor variations, several different exhaust systems, re mapping the ignition, changing the jets, and all the possible permutations of the above, and about 2 weeks of dyno time. Or 20 years of changes!
Tom
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« Reply #745 on: March 29, 2012, 01:14:41 AM »

The bike has 101 dyno runs on it.  It has paid its dues.

The primer was ordered from Freeman Manufacturing and Supply in Ohio.  www.freemansupply.com  It is Duratec VE Grey primer.  They recommend this for coating a mold over which hot plastic will be formed.  It look, smells, and acts like Kondar epoxy filler-primer I used previously for auto painting.

It comes in a gallon can.  I had it split into quarts at the local paint shop.  One quart is always not as full as the others.  He marked 1st on it.  I will use it first.  This keeps the paint good for longer than storing it in the gallon can.  I will use the quarts one at a time over the years.

This stuff is nasty and poisonous.  I mix it with a plastic disposable spoon in a disposable cup and paint it on with a throw away brush.  All is tossed in the outside trash can when I am done.  This is quick and I avoid cleanup.  Less time exposed to chemicals = less toxicity.

The instructions mention spraying this stuff.  A person needs to be spray-paint-superman to do it.  I never figured out how.  I use a brush.  The mold is a nice battleship grey color now.  Tomorrow I will sand it down.  The mold used to be on a board.  That was for vacuum forming.  The person doing the draping wants it elevated like it is now.     


* Fairing Rebuild 135.JPG (182.87 KB, 800x498 - viewed 112 times.)

* Fairing Rebuild 136.JPG (153.71 KB, 800x529 - viewed 145 times.)
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wobblywalrus
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« Reply #746 on: March 31, 2012, 08:59:18 PM »

Today it stopped raining for a few hours.  It was time for a trip to test hill.  The baffles I made several posts ago showed some merits for the idea.  I remade them in three lengths and all were tossed in the saddlebag.  The short baffles have female connectors on the ends.  The bike ran better than with the very short baffles I used the last few years.  The shorter extensions were screwed in and this made medium length baffles.  The bike ran better.  The longer extensions were tried and the bike ran best.  I will make some even longer extensions and try them.

This reversion was the last problem I needed to fix.  The street part of the 865cc/#813 cam motor is done.  It gets gas mileage in the 40's, runs clean at all rpm and throttle settings on el-cheapo gasoline, goes fast, and does not vibrate.  There is nothing left for me to do.  It runs perfect.  I could start on a ride to Maine tomorrow and be sure the motor would not break during the trip.  It is the best street engine I have built.

 


* Exhaust Tuning 14.JPG (205.3 KB, 741x600 - viewed 120 times.)
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Jon
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« Reply #747 on: March 31, 2012, 09:41:28 PM »

Got to be happy with that Bo.

Do you have markers on your hill that you roll on from one to another for speed comparisons.

Used to be a decent hill about 30mile away from where I lived just after I got my license, when I built a motor I used to drive it steady there and cane it up the hill and take it easy down the other side, turn around and repeat a dozen or so times.

Not the "proper" way to run in motor but I never had trouble with rings not bedding in.


Congrats on the build
jon
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« Reply #748 on: April 01, 2012, 10:35:10 AM »

Hi Jon.  The police around here are low on money and speeder tickets are a big revenue source.  They are aggressive.  Plus, the varmints confiscate vehicles during their drug busts and turn them into cop cars.  Almost any late model vehicle around here could be a police car.  It is an effective deterrent and this prevents and full throttle testing except for short bursts.  No longer can I blast up test hill.  The old days were the good ones in some respects.

Engine tuning is my weak point and I am happy to achieve this very modest success.  Work for next year is installing racing springs and keepers and building a racing exhaust system.  The 996cc engine will have hotter cams.  I was going to install them on the 865cc engine just to see what would happen.  Then I was going to install the hotter intake cam with the exhaust cam I am using now, and try it.  The mixed cam setup has worked for me in the past.

The board the mold is on is trimmed back like Kent Plastics wants so it will fit in the oven.  The mold was painted with primer and sanded smooth with 150 grit sandpaper.  Then I painted the mold with two coats of primer and one light coat of black engine enamel.  Now I am using 220 grit paper to sand the mold until none of the engine black shows.  The top of the mold is sanded this way and it is very smooth.  The sanded mold will go up to Kent Plastics next week.  A vacuum formed polycarbonate windshield is the goal.     


* Fairing Rebuild 137.JPG (152.28 KB, 800x533 - viewed 109 times.)

* Fairing Rebuild 138.JPG (194.33 KB, 800x533 - viewed 119 times.)
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« Reply #749 on: April 03, 2012, 01:01:16 PM »

Answer to Post 737.

How do you flow test a jet?

Marlo Treit told me that he made an adaptor that would hold the jet, and changed the size of

the receptacle that measures the quantity of fuel that was flowed. He uses the same flow bench as he does

for any other fuel system. He flows every jet that is used in a fuel system. The number is

disregarded and the amount of fuel flowed is the important number. He may also change the pump

so there isn't too much fuel.

The treatment of the end of the orifice can make a difference in flow as well as the diameter of the orifice.

In some manufacturers jets there is a significant difference in jets with the same number.

He questioned the efficiency of doing Triumph jets if the needle needed to be in place. 

Do the needles have steps in them.

Talk to him when u see him. He will share his procedure with you.


FREUD

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