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Discussion Starter · #1 ·
The cross connect between the two mufflers held together with 6 (Band, Exhaust pipe) , 7 (muffler gasket) and 15 (bolt to clamp them? I think, it does equalise pressure (acoustic resonator or acoustic flywheel) between the two mufflers.

Does this get in the way when trying to raise the bike using the home made wood lift with and a galvanised pipe threaded into a a flange?

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I didn't know the answer to your first question, but this is from West End Motorsports blog.
"Crossover tubes provide another point of expansion and can broaden the rpm range over which the negative wave arrives during overlap, thereby improving the cylinder's ability to bring in fresh air and fuel faster...which in turn offers a more effient burn producing more horsepower and torque."
Your second question, no It does not get in the way.
I slide a (wood) 6×6 × 3' block under the muffler supports. Then tilt the motorcycle toward the kickstand side, & slip in a (wood) 2×3 ×18" until it touches the other muffler support. Then go to stand side, tilt bike up on the blocks & slide in a 8" 2×3. It doesn't damage the mufflers & is quite solid. If I need the front up, I use a single jackstand under the engine guard.
 
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Does this get in the way when trying to raise the bike using the home made wood lift with and a galvanised pipe threaded into a a flange?
Not if you position it correctly.
 

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Discussion Starter · #4 ·
I didn't know the answer to your first question, but this is from West End Motorsports blog.
"Crossover tubes provide another point of expansion and can broaden the rpm range over which the negative wave arrives during overlap, thereby improving the cylinder's ability to bring in fresh air and fuel faster...which in turn offers a more effient burn producing more horsepower and torque."
Thanks for your answer Emil. There is a lot of mumbo jumbo in automotive blogs. Sometimes the information is right but the reasoning is wrong or the terminology is sloppy, sometimes it's plain wrong and at others I am completely wrong or misunderstand them. They have given some handwaving arguments, and used terms that I don't know they understand. For example "negative" wave: Is it just the reflected wave regardless of the phase, reflected wave 180 degrees out of phase, or rarefaction instead of compression? On the other hand, the sense in which they use terms might be industry standard.

Anyway, I tried to do some back of the envelope calculations.
Speed of sound:1125 ft/sec. This is the speed with with compression or rarefaction waves travel along the exhaust. It is safe to say that waves of all frequencies travel at the same speed (unlike light of different wavelengths--colour-- travels at different speeds and disperses, like in a prism)
Length of the exhaust from cylinder exhaust port to the cross over. about 3 feet.
Engine RPM, 4800 (mid range) or 80 Hz 80 revolutions per second.
An exhaust compression wave goes out once every two evolutions. So we have 40 compressions per second or a compression wave goes out every every 0.025 seconds or 25 miliseconds. By the time a subsequent wave arrives, the previous waves is long gone. At 1200 RPM, it arrives every 100 milliseconds.
Now, how long does sound wave take to travel a distance of 3 feet? 3ft/1125 ft per second=0.00027 seconds or 2.7 milliseconds
Sound wave, which is also compression and rarefaction takes much shorter time to travel to the cross over than the duration between two successive outgoing waves from the exhaust port. even at 14400 RPM, the time between two successive waves is 8.3 seconds about 3 times longer than it takes the wave to travel do the cross over.
Would it make a difference, maybe, I doubt it.. For Honda Rebel? Probably not.

Thank you for sharing the method you use to jack your Rebel. I need to do that whether I do the tires myself or take the wheels to a dealer. The dealer charges $40 per tire t mount and balance (when I roll the wheels over to the shop) and $80 per wheel (when I roll the bike over to them). I am going to take a look under the bike again and measure the height of exhaust brackets on both sides when the bike is on the side stand. I seem to remember it's 5 3/4 inch.
 

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Correct on the height for all intents. A 6×6 is 5.5" so it just slides under. By adding the (oops I said 2×3 before) 3×4 (wide side horizontal), that puts the rear tire ~2" off the ground.
 

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No this isn't a sound wave this is a pressure wave. The pressure from the exhaust stroke.
 

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Discussion Starter · #7 ·
No this isn't a sound wave this is a pressure wave. The pressure from the exhaust stroke.
Yes, sound wave is a pressure wave. The only difference is that the pressure wave coming from the cylinder is in impulses, which can be broken down into many, actually infinite number, frequency components. The sound we utter, the pressure wave and a pure sound wave from a tuning fork are all the same except for frequencies. NO?
 

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I should have included the previous paragraph from the article I quoted earlier. It helps explain their reasoning.
"As the exhaust valve opens, a wave of pressure travels down the exhaust. When it comes to a point of expansion (when it reaches the muffler, or when it reaches the end of the exhaust), that wave of expansion also expands back up the pipe. Because positive and negative waves alternate in the pipe, at some lower rpm it is a positive wave that arrives at the cylinder during valve overlap. This reduces torque and power by pushing spent exhaust gas back into the cylinder, slowing down the intake process."
 

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I just changed the front fork oil on my bike and I figured I'd show 20210719_210419.jpg 20210719_210241.jpg 20210719_210254.jpg you the blocking as I do it.
 

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And the muffler isn't resting on the blocks?
 

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No. The brackets for the muffler take the load.
I've done this for years with no I'll effects.
 

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Discussion Starter · #12 ·
Correct on the height for all intents. A 6×6 is 5.5" so it just slides under. By adding the (oops I said 2×3 before) 3×4 (wide side horizontal), that puts the rear tire ~2" off the ground.
Thanks Emil. have some 6 x6 laying around. Why 3 feet?
3 x 4--will 2.75 x 4 do? I think you can only put it in wide side horizontal since the other side is a bit rounded. I used those to make a general purpose table to use in the carport as they were cheaper than 4 x 4. Just cut the rounded faces off with a table saw. They were $1:49 then. I haven't got an engine guard. I shall try using a scissors jack or a floor hydraulic jack with a 2 x 7 on the saddle and augment it with a jack stand provided I can find a place to put it under without damaging anything---to jack up the front end.
 

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I just took a very close look under the bike. I need to change my answer.
Yes, the weight is resting on part of the muffler. But, it is at the brackets & presumably the strongest part of the mufflers.
Again, this is an 85, I've done this the whole time that I've owned this. It has never become an issue.
Admitting when one is wrong resolves problems before they escalate.
 

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The reason for the length it is because at at times the the motorcycle tends to slip sideways. This avoids it's slipping off of the six-by-six.
Also yes, I am using the standard Numbering from lumber, not the actual dimensions.
 

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No offense Emil, but I wonder whether the entire bike weight on the muffler brackets is a good idea.

Yaatri, here's a thread on a home made lift that's similar to what you referenced earlier. Only contact points are on the frame. cheap floor jack | Honda Rebel Forum Unfortunately, Photosuckit deleted the pictures when the subscriber refused their ransom demand. Here's the site he got his idea from: $20 Bike Lift (nightrider.com)
 

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Discussion Starter · #16 ·
No offense Emil, but I wonder whether the entire bike weight on the muffler brackets is a good idea.

Yaatri, here's a thread on a home made lift that's similar to what you referenced earlier. Only contact points are on the frame. cheap floor jack | Honda Rebel Forum Unfortunately, Photosuckit deleted the pictures when the subscriber refused their ransom demand. Here's the site he got his idea from: $20 Bike Lift (nightrider.com)
Thanks FC. I have seen the site with $20 lift before. It won't be $20 anymore. So I decide to order paddock stands for front and rear. I need to change the tires. Even if I remove the wheels and take the wheels t a shop, I have almost paid for the pair.
 

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Shop prices for tire work (especially if you don't buy the tires from them), are why I learned to change and balance tires myself.
 

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FC you are wise to be cautious. Each must be alert to potential hazzards then decide what is right for them. This idea wouldn't be good for some with damaged or rusty mufflers to be sure. And probably not the best idea that has come up. The fact that it has worked without a problem however many years, doesn't mean it will not cause one in the future. Your critique has been noted.
 
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