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Based on previous exhaust system comments (from Vmax maillist)
I would say most people would select:
#1: Hindle 4-1 Exhaust.
Sounds nice, Excellent power gains, clears center stand but
reduces right hand cornering clearance slightly
#2: Vortex 4-1 Exhaust from
Holeshot. More expensive version of Hindle but is jig fitted and
jet coated
#3: Kerker 4-2-1. Good
Power. Louder than hindle when equipped with 2"+ baffle. (3
baffles avail), Requires removal of center stand
retaining tabs.
#4: Slip-ons; e.g. Supertrapp . Loud or quiet
depending on style. Note: Be careful of some
slip-ons since they eliminate the stock collector box which
provided some equalization of exhaust pressure for each port. No
rear pipe cross over = less h/p. Check out one of the best
looking (to me) slip-ons with a full
collector system.
#5: Drill stock muffler out - 5 holes of approx
1/4". Okay sound but greatly reduces value of the exhaust.
No weight savings.
Some more thoughts....
right from Hindle..."The new version [pipe design] offers
more ground clearance and a slight loss in top end horsepower.
The older version does not offer the great ground clearance like
the new one but offers a little bit more hp."
IMHO, The Kerker has a smoother power curve but slightly less up
top end than the older Hindle and kiss your centre stand tabs
good-bye which may or may not be a small price to pay for
clearance.
There are a number of nice 4-2 systems on the market like BSM and
Over USA. Some offer slightly larger primaries than stock and a
collector pipe.
Most systems work well on a stock engine. As for the gain in
horsepower, a pipe alone should give up to 6 ponies (with tuned
carb), combined with a jet kit you are looking for a total of
8-12 depending on kit. This is your best hp bang for
the buck, after this it starts to get expensive.
On a big bore, the production pipes will work well, however the
engines can benefit from slightly larger (diameter) custom made
systems especially if any head work has been done.
Regardless of system , the restriction at the can has the most
dramatic effect. A single 1.75" or smaller bore is
likely worse than the stock exhaust, a 2" provides a
reasonable power gain, 2.5 is loud and proud...Twin systems offer
the best chance to reduce restriction while keeping the db's low.
Flow and noise do not have to be synominous. According to my calc's, for best performance a muffler on the Max should be able to flow at over 300 cfm with a backpressure of no more than 0.2 psi.
Unfortunately, the straight through perforated bore with absorbtion wrap (eg glass wool jacket) that appears to be the most common free flow performance silencer is also one of the poorest designs for a motorcycle. This is due to the intermittent nature and high velocity of motorcycle exhaust.
To improve the effect of this type of exhaust it is recommended to have a smaller outlet than inlet. This encourges the wave motion in the jacket. It is also recommended to have a minimum of 1.25 inches of absorbtion material surrounding the bore. This equals at least a 4.5" can diameter for a 2" bore. If the reduction is kept reasonable (8% or less) there should be no noticeable loss in performance. So if considering a new exhaust, you might want to match the bore close to your collector/ tail pipe and chose a size of outlet tip slightly smaller to match the desired noise level. You then have the option of switching out tips vs. cans for performance changes...
If noise is a real problem, for now keep on the stock dual exhaust vs. restricting the single can. Yamaha did a good job on its design despite having to keep within noise restrictions. The collector box fools the engine into thinking the primary pipes are dumping into open atmosphere and smooths out the pulses allowing a more continuous flow through the mufflers. The stock exhast is heavy but it works fairly well....better than a choked off single can by far...(Creating just a single (1) additional pound of pressure, eg with too small of an silencer outlet, would reduce hp by 10 to 15%).
Having said all this, there is a real need in the motorcycle world for a free flow low noise silencer. A lot of work is being done in the automotive field directing exhaust sound waves through a muffler in a manner that they cancel each other out. Although more difficult some of this techology could be used for a m/c. As a minimum, a dual silencer system will provide the best opportunity to combine performance with real world daily street use.
The topic of m/c exhausts can fill books, but here is my
theoretical two bits to the 4-1 vs 4-2-1 discussion.
There are two primary considerations involved in
designing/choosing an exhaust. The first deals with the exhaust
gas that travels at 200-300 feet per second. Here we are
concerned with reducing the back pressure while maintaining flow
velocity to get the best cylinder exhaust purging. The
second is exhaust pulses or finite-amplitute pressure waves which
travel the speed of sound or at about 1700 feet per second.
These pulses can be tuned to create an effect known as scavenging
(sucking additional exhaust out and intake charge in, with a
properly timed negative pressure pulse).
Exhaust gas...general rule of thumb, a narrower
diameter pipe will improve low rpm flow hence torque but may
limit top end. A wide diameter pipe will enable top end
power but have poor low end velocity (eg great for the track but
lacking on the street). So choose the where you want
your power band and set diameter accordingly. Increasing or
decreasing pipe diameter 1/8th will move the torque peak about
500 rpm up or down. Varying the length of the pipe will
fill in the power curve around the torque peak. Shorter
pipes fill above and longer pipes below. A good starting
point for exhaust pipe area is the circumference of the valves
times the maximum lift plus about 15%. A good starting
point for the length of the primaries is 28-32 inches.
Exhaust pulses--when a positive exhaust pulse traveling down the pipe reaches an opening or increased diameter it is reflected back as a negative pulse. This negative pulse can be timed to reach an open exhaust valve to provide scavenging. The rpm's that this occurs is at peak torque and contiunes in the upper portions of the bike's power range. However, there is a trade off. In the lower rpm's the valves are open longer and thus also allow a positive wave to hit. This usually occurs around 2/3's - 3/4's of the torque peak (between 4000-5000 rpm range on the Max) and is why you see a lot of dyno dips in the power band in this range. The positive wave pushes exhaust back into the cylinder and in some cases, if there is enough valve overlap it will travel up the intake track and cause triple loading of the intake charge (air is drawn through, pushed back and drawn through again.) Here is where the 4-1 versus 4-2-1 make a difference. The 4-1 will have a STRONG tuned pulse. Therefore it will have a higher top end (strong negative wave) but a bigger hole in the mid range (strong positive pulse hits while valve is open). A 4-2-1 will soften and lengthen the pulses, as the 4-2 connection provides an interference wave in addition to the primary waves. A similar effect can be done with stepped pipes. The top end effect won't be as great but it will be longer. The mid range dip will also be shallower hence, the adage that a 4-2-1 improves mid-range.
In a nutshell, the biggest decision for power is the diameter of the pipe and then the length. Choose these based on where you want your power band. Tuning the exhaust pulses with a 4-1 or 4-2-1 then should be done with the idea to compliment your first choice....and of course always have a highflow muffler.
As a bit of a disclaimer...one of the problems with exhaust and intake pulse tuning on the Max is the 70 degree timing difference between the front and rear cylinder banks. In line fours and of course the venerable V-8 fire in 180 and 90 degree increments respectively which enables matching the cylinders and pulse timing...
Many Maxer's complain of a hot running bike with the temp needle up in the 3/4 range (in slow traffic) before the fan comes on. This IS normal, especially for a new tight engine. However, if this bugs you, there are a few remedies.
1) Put in Water Wetter and good anti-freeze
2)Put in a toggle switch connection which allows manual fan activation.
3) Change out the stock Thermal Switch (as first suggested by Ol'man Don Smith I believe-and detailed here by Mario Aguiar).
The replacement switch is the thermal fan switch from BORG-WARNER TFS-545. It is used to replace the stock Yamaha, which usually activates the fan at 236F, (way too hot). This new switch will open between 198F and 208F, so your temperature will not go over the half way mark on the temp gauge.
The original is located on the conduit, behind the right side air scoop, just cut the wires from both plugs (the one in the bike, that goes to the fan, and the one on the new switch), solder them or use crimp/on connectors, NOTE: replace the O ring on the new switch, with the one from the stock one, because the new one is too thick.
A couple of cautionary notes: Go gentle on the tightening, don't forget the housing is made of aluminum. Also, a couple of people have found that the fan runs too much on their machine and have gone back to the stock switch. This may occur due to manufacturing tolerances (eg bike's thermostat opens late and the new switch comes on a little early. So...don't do this mod if your machine does not usually raise the needle more than half way...
Note: in addition to the BorgWarner switch you can use a WELLS-SW537 switch or even NAPA carries their FS-147switch, all about $30.
OK I dynoed my bike like I said I would today and was not dissapointed in the Hindle Pipe. Currently my bike is stock except for a K&N filter, pilots adjusted to about 4 turns out, needles shimmed up, and the Hindle Pipe. The mains are stock. Before I put the Hindle on I had Dynoed the bike. It made about 110 with the air horn on and about 112 with the air horn off. It was too lean on the top end and lost a lot of power down low with the air horn off. Today the bike made a little over 120 with the air horn off or on. Peak Power was about the same either way. It is still too lean on the top end and putting the air horn on smoothed out the curve considerably. I am going to go up on the mains and I will let you know the results of that once I do. The power curve is much higher the whole way up though. Since the dynojet doesnt show RPM I will give you MPH in 3rd and some comparisons
As you can see the bike pulls harder the whole way up the
scale and pulls further without even touching the jetting. I cant
wait to change the mains. Now the question is "to kit or not
to kit?" Roy
... the best thing about the 1300(86up) motor is that the cases are built heavier, great for big-bore motors. This info was courtesy of John at PCW a few years back. Venture-VMAX and vice versa swaps are easiest if you have both bikes fairly intact to swap shifter linkage and the like; all differences are minor and bolton. The other thing I like about the Venture motor(1300 only, the early ones 83-85 were junk) is the wide ratio trans; the prototype VMAX had a Venture trans, and in stock form, smokes other stock MAXs in the higher gears-there's some food for thought, huh? Yes, the prototype MAX, complete w/billet pieces and one- off parts(pre-production) is alive and well, thanks to a Yamaha rep, and licensed and driven regularly, here in the States.
At TDC (which is where they tell you to measure clearance) the cam lobes on intake & exhaust for that cylinder will both be pointing away from the valves at about a 135 deg. angle (valve closed). As I recall the rear two cylinders' lobes end up looking like this \ / (both pointing up) and the front like this / \ (or it may be the other way around). I don't think it's all that critical as long as the valve you are measuring is fully closed, cam lobe pointing away.
If any clearances are out of spec, you'll need: Metric feelers (lotsa luck) OR feelers with at least a .0015 or .0025 leaf so you can measure to closest .0005 - Measuring only to the nearest .001 will result in having to do some valves twice
Valve depressor tool - Yamaha's is a piece of crap but better than nothing. There's gotta be a better one from K&L or whatever.
Supply of shims or good quick source - These are expensive, the best answer is if you can find someone who will trade with you for $1 apiece or whatever.
A magnet on a stick for the shims, otherwise they are difficult to remove & replace.
A 32mm socket to turn the crank. DO NOT turn the crank by the smaller bolt (17mm?) in the end unless you are prepared to retorque it to spec if it comes loose.
Pitfalls:
Careful removing the timing cover (if you haven't already) the screws are tight & easy to strip. Make sure you are using a REAL METRIC 5mm allen wrench & not a 3/16 inch (which is very close but too small).
Do NOT turn the crank unless ALL shims are in place!
Here is how to figure out what shim you need (this is going in my FAQ when I get time to work on it). Note the EXHAUST table in the shop manual is WRONG (at least in my edition ca. 1992) :
Go through all the valves and see which ones are out of spec (Intake: .004 inch fits .006 does not; Exhaust: .010 fits .012 does not). Then put the tool on those & pull the shims out & write down what they are & put them back in. Then you'll know what you need, some of them you may be able to reuse. I drew a map of the valves and wrote the (existing) clearance and shim number on the map. Then I took it in the house to do the math to get the new shim numbers. Some of the ones I needed were already on other valves.
Metric conversion:
Biggest feeler Approximate Biggest feeler Approximate that will fit metric clearance that will fit metric clearance .001 .03 .011 .29 .0015 .04 .0115 .30 .002 .06 .012 .31 .0025 .07 .0125 .32 .003 .08 .013 .34 .0035 .10 .0135 .35 .004 .11 .014 .36 .0045 .12 .0145 .37 .005 .13 .015 .39 .0055 .15 .0155 .40 .006 .16 .016 .41 .0065 .17 .0165 .43 .007 .18 .017 .44 .0075 .20 .0175 .45 .008 .21 .018 .46 .0085 .22 .0185 .48 .009 .23 .019 .49 .0095 .25 .0195 .50 .010 .26 .020 .51 .0105 .27 .0205 .53
Now for desired clearance, pick the number halfway between the minimum and maximum from the manual: Intake .11-.15mm (use .13) Exhaust .26-.30 (use .28).
Now take the existing shim 2.70
Add the existing clearance + .06 (.002 fits .0025 doesn't)
_____
2.76
Subtract the desired cl. - .28 (.13 intake .28 exhaust)
_____
Desired shim = 2.48
Use the closest one available to this number. They come in .05 steps so you would use a 2.50. The factory also uses 2s and 8s, so if you had a 2.48 you could use it.
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