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Message started by DragBikeMike on 07/21/21 at 19:40:47

Title: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:40:47

This is the sixth in a series of reports intended to document the results of progressive modifications to the LS650 engine.

Part 1 outlined the project, set the rules, and established the baseline performance values for a box-stock LS650. You can find Part 1 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1620523526

Part 2 examined the airbox. We improved performance dramatically with a few simple and inexpensive modifications. It was a lot of bang for the bucks. You can find Part 2 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1621150483

Part 3 took a hard look at the exhaust system. We tried a Dyna muffler and a hybrid muffler (home-built). We also tried the larger Mac header pipe. The exhaust modifications provided significant improvements in acceleration and fuel economy. You can find Part 3 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1623048749

Part 4 installed a performance carburetor and revisited the air filter. You can find Part 4 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1625732492

Part 5 installed a new camshaft with higher lift and duration. The results were gratifying and informative. With some valve overlap, the exhaust header took on a new role. You can find Part 5 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1626391255

Part 6 installs a lighter flywheel. Reducing the weight of the rotating assembly should consume less horsepower, leaving more power to drive the motorcycle. We’re looking for quicker acceleration. It will also reduce the weight of the motorcycle which will provide a modest improvement in the horsepower to weight ratio.

What I am about to describe worked good for me. If you decide to try this stuff on your own, you assume responsibility for the outcome. If you don’t have the skills, don’t do it. If you don’t understand something, STOP and get help. Get a manual. Read up. Comply with ALL the safety requirements outlined in the manual. Make sure you know what you are doing before attempting any of these modifications.

Let’s get started.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:42:08

In Part 5, we kicked the power up a notch by installing a camshaft with more lift and duration. The new cam worked great. Now that we have some valve-overlap the engine breathes much better. Up to this point, we have relied on improved airflow to increase horsepower and torque.

The next item on the to-do list is the flywheel. The stock flywheel is big and heavy. It is 6.5” inches and weighs 6 pounds. It must take some horsepower to accelerate that 6-pound mass up to 7000 rpm.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:43:40

I know from experience that installing a three-inch flywheel does not seem to adversely affect operation. The engine runs fine with the smaller flywheel. Seat-o-da-pants it feels like it’s a bit faster. Now it’s time to measure performance and compare. Will the lighter flywheel improve acceleration? What effect will it have on top speed?

The 3” flywheel only weighs 15 ounces. If nothing else, it reduces the curb weight by 5 pounds. It should also improve acceleration. Less rotating mass should spin up faster.

To get your hands on one of these, you need a lathe, or you must pay someone to machine off the excess material. Take the O.D. down to 3.000”, maintain concentricity within .001” TIR. Here you see the difference between the 6.5” flywheel and the 3” flywheel.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:44:31

Replacing the flywheel requires some special tools. You need a special puller to remove the alternator rotor.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:45:31

You can find the puller on Amazon or eBay. It costs about $50 bucks. BikeMaster 152481

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:46:18

You need a 46mm deep socket. I made this one for Harley Davidson drive pulley nuts. With a simple modification, it works on the LS650 flywheel nut. A bona fide 46mm six-point deep-socket is a better choice.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:46:54

A 36mm wrench comes in handy for holding the alternator rotor when you remove or torque the rotor bolt. There are ways around this wrench, but life is much easier when you have one of these.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:47:33

You need a tool to hold the flywheel when you remove or torque the flywheel nut. I made this contraption. It bolts to the stock flywheel using the 8mm threaded holes in the flywheel. It also works on the 3” flywheel. There are no threaded holes in the 3-incher, so the tool incorporates a clam-shell clamp.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:48:43

The flywheel resides behind the alternator rotor. To remove the alternator cover you must remove the drive pulley cover. There’s only three bolts that hold the pulley cover on the engine.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:49:32

The pulley cover has these rubber washers. It’s resiliently mounted. Don’t mix up the rubber washers. The washers on the inside are thick, while the ones on the outside are thin. Mix em up and the pulley rubs on the cover. Makes one helluva racket. See, thick inside, thin outside.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:50:38

The left side footrest assembly must be moved out of the way. Since the side-stand switch is attached you need to free up the wires to the switch. If you don’t free up the wires, you may damage the switch when you try to move the footrest. Remove any zip ties that restrain the wires running along the left side frame rail.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:51:21

The wire bundle from the alternator runs in a groove on the engine case. The wire bundle is held in place with a clip.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:51:57

Loosen the small bolt and swing the clip out of the way.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:52:46

To move the left side footrest assembly, the motorcycle must be held upright. The side stand is part of the footrest. You need a way to hold the bike upright. I use a simple wooden device that allows me to hold the bike upright with tie-down straps.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:53:29

There’s not much to it. Just a few chunks of scrap lumber. It’s versatile. Allows working on the bike without fear of dumping the whole shitteree on it’s side.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:54:08

It also permits leaning the bike over for those jobs where you don’t wanna drain the oil.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:55:04

Now that the wires are free from the frame, and the motorcycle is supported properly, remove the nuts that hold on the right-side footrest. Tap the bolts toward the left until the right-side footrest can be removed and lowered to the ground.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:56:07

Remove the shift-shaft lever from the shift shaft.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:56:51

Remove the hidden bolt that secures the left-side footrest assembly to the frame.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:57:48

Continue to tap the front engine mount & footrest bolts toward the left until you drift the left side footrest clear of the alternator cover. Be careful, watch the wires on the side stand switch. Don’t stress them.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:58:28

Place a drip pan under the alternator cover to catch any oil that dribbles out. Also lay some clean cardboard on the ground so you have a nice place to set the alternator cover once it’s removed.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:59:16

Remove the alternator cover bolts.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 19:59:51

There are nine bolts.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:00:30

Carefully remove the alternator cover. It will resist. The magnets in the alternator rotor will be pulling on the stator. Once you clear the magnets, it will be easy to move the cover. Be careful with the wires. Lay the cover down on the cardboard.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:01:34

Immediately start looking for this washer. It goes on the starter torque limiter assembly. Very easy to lose.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:02:29

Each side of the torque limiter assembly has a washer.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:03:39

When you remove the torque limiter assembly, the inner washer may stick to the engine case.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:04:25

Sometimes the washer falls between the starter clutch gear and the flywheel. The washer usually ends up here.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:05:20

If the washer falls between the flywheel and the starter clutch gear, immediately take action to capture the washer. Don’t continue until you have captured the washer. A long piece of wire works good. Carefully thread the wire through the washer and tie it off. Now the washer can’t get lost (i.e. fall into the engine).

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:06:11

You’re gonna lose a bit of oil when you remove the alternator cover. That’s why you want a drip pan.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:06:59

Loosen the alternator rotor bolt. Hold the rotor with the 36mm wrench and loosen the bolt using a 17mm socket. I use an impact gun. Some experts advise against the rattle wrench. Seems there is concern about damaging the magnets in the rotor. I have never experienced a problem, but who knows. You’ll have to decide on your own which tool is best. The bolt must remain in the crankshaft, don’t remove it completely. Just back it off several turns so that there is at least a ¼” gap between the rotor and the bolt flange.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:07:34

There must be a gap between the bolt flange and the rotor. Like this.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:08:36

Remove the rotor using the special rotor puller. Lubricate the jack bolt threads and tip before installing the tool on the rotor. Thread the tool onto the M50 x 1.5 threads on the rotor, then install the jack bolt and screw it in until it touches the alternator rotor bolt. You must be sure the tool is completely threaded onto the rotor before you install the jack bolt. Back the body of the tool off about one-quarter turn, then hold the tool with a large crescent wrench while you turn the jack bolt in (clockwise). It takes quite a bit of force to pop the rotor off the crankshaft taper.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:09:13

Once the rotor has been removed, you can see the drive key. The key will prevent the starter clutch gear from coming off the shaft.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:09:58

The key fits tight in the keyway. You have to break it loose. Wrap the key with tape so you don’t loose it. Then lightly drive the key straight in with a punch, as shown. Use very light force, keep the punch off the crankshaft taper. Tap just hard enough to move the key.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:10:41

Once the key is out, remove the starter clutch gear.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:11:21

The taper is critical. Don’t damage it. Keep it looking like this, free of blemishes.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:12:08

There are two 8mm tapped holes in the stock flywheel.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:12:52

Install the special flywheel holder on the flywheel. The two 8mm bolts screw into the tapped holes in the flywheel.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:13:45

Use the 46mm deep socket and an impact wrench to remove the flywheel nut. It’s a thin nut. There won’t be much engagement between the socket and the nut. I like to use a scissors jack to help stabilize the tools. Applying force on the socket with a pipe wrench, in conjunction with the impact wrench, helps to break the nut loose.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:14:23

Remove the flywheel nut. There is a Belleville washer between the nut and the flywheel. The washer outside diameter edge goes against the flywheel. The inside diameter edge goes against the nut. Make sure it is oriented correctly when you reinstall the washer.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:15:23

Remove the stock 6.5” flywheel and install the 3” flywheel. There are no threaded holes in the small flywheel. You can tighten the flywheel nut using an impact wrench. That will probably be sufficient, but I prefer to torque the nut to the prescribed value (about 105 ft-lbs). That requires holding the flywheel. The special clamp tool comes in handy.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:16:10

Ready for reassembly. The new flywheel doesn’t take up much room.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:16:42

Reassemble the starter clutch gear, alternator rotor, alternator cover etc. It’s just the reverse order of the disassembly process. Use the manual, follow good mechanical practice. Don’t forget the alternator rotor key. Don’t forget the alternator cover dowels, wire clip or zip ties. Pay attention to the starter torque limiter washers (one on each side), and the pulley cover rubber washers (thick inside, thin outside). As mentioned, flywheel nut torque is 105 ft-lbs. The alternator rotor bolt torque is also 105 ft-lbs. It’s a good idea to put a drop of red Loctite on the alternator rotor bolt before installation.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:19:07

How does it run? Just fine. Starts right up, idles smooth, revs about the same. With the gearbox in neutral, snap the throttle open and everything seems the same as it was. Vibration levels feel about the same. Noise is the same. Clutch action seems about the same, might take a little more finesse to get underway. Very surprising, you would think this thing would really snap, but there’s no perceptible difference.

Time for some acceleration tests.

Let’s look at the setup. Stock engine with DR 650 cam and 3” flywheel, stock cylinder head, stock piston, stock bore & stroke, stock compression ratio (8.5:1), modified airbox with K&N RD-0710 cylindrical filter element, PWK38 carb, stock exhaust header, LCGP high flow muffler.

The flywheel isn’t going to affect air/fuel ratio, so I left the jetting as-is, a #35 pilot jet, #145 main jet, and the needle clip in the fourth groove (rich).

Second Gear 4K to 7K: 2.92 seconds 0.05 seconds faster than stock flywheel (a wash)

Third Gear 4K to 6.5K: 5.13 seconds 0.11 seconds faster than stock flywheel

Third Gear 4K to 7K: 7.53 seconds 0.12 seconds faster than stock flywheel

Fifth Gear 3.5K to 5K: 5.04 seconds 0.02 seconds slower than stock flywheel (a wash)

Fifth Gear 3.5K to 5.5K: 7.96 seconds 0.21 seconds slower than stock flywheel

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:20:45

Acceleration improved slightly in the lower gears, but slowed down a bit in fifth gear??? In addition, maximum rpm in 5th gear dropped by 250 (6050 rpm vs 6300 rpm). What’s goin on here?

This is a big single-cylinder engine with a power curve that flattens out right about 5500 rpm. My previous dyno pulls with this cam show the engine makes good power past 5500, but that power really isn’t increasing. It’s flat from 5500 to almost 7000.

Aerodynamic drag goes up by the square of the bike’s speed. The amount of horsepower required to power the bike increases by the cube of the increase in speed. We have a flat power delivery struggling against an exponentially increasing power demand.

With a single cylinder engine, you get one shove (power stroke), followed by three parasitic strokes (exhaust, intake, compression). That one shove, the power stroke, must provide enough motive force to sustain rotation through the remaining three strokes, plus overcome all the parasitic losses (friction, valve springs, pumping exhaust, compression, etc.), plus overcome the exponentially increasing counterforce presented by the wind. Without the energy stored in the heavy flywheel, the rotating assembly can’t maintain forward motion, it loses ground to the wind.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:22:15

Is the light flywheel worth the effort and expense? Depends what you are looking for. If you are into stop-light drag racing, you might like the small flywheel. If you spend a lot of time on the open road where you want the best top gear performance, the heavy wheel is for you.

I was surprised that the 3rd gear acceleration numbers didn’t show a bigger improvement. We took a lot of weight off that rotating assembly. Seemed like it should have made a bigger difference. But the stopwatch don’t lie.

It will be interesting to see what happens when I add more compression or displacement. I don’t know if these old bones have enough gas in the tank to get into the regimen of swapping flyhweels with every engine combination (head, cam, & CR). We’ll see how things shake out.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/21/21 at 20:24:45

This completes the flywheel portion of the project. The 3” flywheel was a wash. It provided a small improvement in the lower gears but a slight loss of performance in top gear. The 3” flywheels don’t grow on trees; you won’t find one on Amazon or eBay. It was not hard to install but required some special tools. I would say that most of the Savage crowd would find little benefit from this modification, and some would be disappointed.

Performance remains about where we left it at the conclusion of Part 5. Moving forward, I will leave the small flywheel in place until circumstances dictate another look.

Next stop on the Power Train? Cylinder head. Let’s see what happens when we slap on a head with significantly better flow-bench numbers. Part 7 will install a ported head.

At this point, I have done 174 WOT acceleration pulls to dial in the different combinations. There’s a little over 2450 miles on the engine since it was restored to box-stock configuration. The old girl is still holdin up good. No leaks. No ugly noises. Not using any oil. Just a bit of oil accumulating in the catch-can. It’s still a solid motor.

I hope some of you find this project informative and can use the data I collect to help make decisions on your own project. If you have suggestions or comments on my test methods, post a reply so we can discuss. As mentioned earlier, if you have a particular component or modification that you would like to see included, let me know and we can collaborate.

Best regards, Mike

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by zevenenergie on 07/22/21 at 03:39:07

Great howto...

I'm not really surprised at the result.
I did the same with a 70cc 2stroke engine.
I replaced the steel centrifugal coupling on the crankshaft with an aluminum one and made the flywheel 70% lighter.

It gives a better throttle response in neutral.
But with acceleration on the road no difference at all.

What was clearly noticeable was that the braking distance became shorter.

The acceleration is mostly determined by power and the weight of the bike and various resistances.
The engine therefore accelerates too slowly to be bothered by the inert flywheel.

The braking decereration take place in a shorter period of time. And especially at high revs there is a lot of energy in the flywheel.
Which then has to change relatively faster in rotation than when accelerating.

(Sorry for my poor englisch).

I'm curious how your flywheel brakes.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by Armen on 07/22/21 at 04:30:37

Thanks for the detailed write up!
Have to say, I'm surprised at the results. I remember Dave got some significant measurable improvements with the lighter flywheel.
Hmmmm

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by LANCER on 07/22/21 at 10:08:45

When doing your timed runs how do you start and stop your stopwatch ?

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by Dave on 07/22/21 at 12:41:58

As Armen stated, my timed runs did show a pretty big drop in my 0-60 mph time. I did about 5 runs with each flywheel using my GPS that records 0-60 times. I did the runs with the big flywheel in the morning and the runs with the small flywheel later that same day. My times with the larger flywheel were around 5.5 seconds, and I got them down to around 5 seconds with the lighter flywheel. Perhaps some of that difference was me just getting better at leaving the line and shifting gears.........with my tall gearing I only have to shift once as I reach 60mph in second gear.

The weird thing was that my 1/4 mile times were almost identical with either flywheel. I did not understand if my data was accurate....or if I could not leave the line as aggressively - it was weird as it just didn't seem to be logical.

In order for my 0-60 times to be better - but my 1/4 mile times to be equal.....that would require the bike to be slower somewhere after I got to 60 and was going to the from end of the 1/4 mile! (I am not home right now where I can see what my MPH was at the end of the 1/4 mile).

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by DragBikeMike on 07/22/21 at 15:52:51

Zevenenergie I think you articulated the braking issue quite nicely. That's something I hadn't considered, but it is certainly a valid point. The absence of flywheel should most certainly improve compression braking.

Lancer I do the timing off videos. I record my runs using a GoPro camera and then do the timing in the comfort of the climate controlled DBM laboratory. It works great. All the pulls are done on the secret DBM closed-course test-track, in exactly the same location for each gear. I try to always do the tests under similar atmospheric conditions. Not perfect but the best I can come up with.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1577664388/0#5

Armen I agree. I was actually very surprised. I figured the lighter wheel would make a big difference. After I did the timing pulls, I decided to see what I could dig up on Google. I kept finding discussions where gearheads spoke about other gearheads loosing top speed when they installed a lighter flywheel, but I could never find a direct link to the source. The discussions always wandered around with a bunch of theoretical back & forth. I could never find the "horse's mouth". Apparently, there are others who have experienced the same phenomenon. Dave's experience, in a way, mirrors mine. His 0-60 dropped, but 1/4 mile ET remained unchanged. That indicates he accelerated faster in the low gears, and slower in the high gears.

Dave it would be great if you could find that old MPH.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by zipidachimp on 07/22/21 at 21:31:44

DBM: really appreciate all of the work you are doing to develop this engine. Here's my quandary: going through my 10 years of 'motorcycle classics' , I constantly wonder why 500 singles, GoldStar, Manx, G50, Velo, 2-valve heads, are shown with higher HP and much higher top speed, compared to our 4-valve head, higher volume lump?
All of these bikes are internationally known, S40 not so much.
The only modern single with greater output is KTM, especially the '390r' which is leading the MotoAmerica novice class against Ninja 400s.
What makes these older singles so powerful?
It's not all due to CR !
Cheers! 8-)

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by Fast 650 on 07/22/21 at 22:37:05

Don't get fooled by the HP numbers of older bikes. They used to measure HP at the crank instead of at the wheel so those numbers will be higher than if they were measured at the wheel.

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by zipidachimp on 07/22/21 at 22:46:37

Manx 500....130, 140 mph ?
1. https://en.wikipedia.org/wiki/Norton_Manx

1961 Matchless G50 specifications
Type: Air-cooled SOHC single
Capacity: 496cc (500cc)
Bore & Stroke: 90mm x 78mm
BHP: 51 @ 7200rpm
Maximum speed: 135mph
Cheers! 8-)

Title: Re: Evolution of a HotRod - Part 6 Flywheel
Post by Dave on 07/23/21 at 04:09:36

6A79607974717378797D60100 wrote:

Manx 500....130, 140 mph ?
1. https://en.wikipedia.org/wiki/Norton_Manx

I just finished reading a book about the Norton Manx 350 and 500 race bikes. The factory worked very hard trying to get more performance out of the bike, and each year they seemed to find one or two more HP. The book stated that in 1961 they were up to 53HP. The bike was a true race bike and had a very narrow rpm range where it ran well - it had to be wound up to make power and be competitive. They were able to find a few more HP - but only a few riders could use the extra power productively and keep the engine revved up where it made the extra power.....most riders were faster around the track with the 53HP engine.

The Manx engine is not an engine that can be ridden on the street from what I have read. It is a race engine and it has horrible manners when out in public. The engine has to be kept up in the power band to run well.

I believe the cylinder head is the limiting factor in the design of the Savage. When I look at the intake and exhaust ports of engines that make big HP they are smooth and straight in comparison to the Savage.

The DR650 engine is very similar to the Savage engine - but it was able to make 46HP in some countries (in some countries it was detuned to 34HP likely to comply with restrictions).

I believe Suzuki was engineering a small capacity Cruiser type motorcycle that was not a performance bike, and they intentionally designed it with good torque values and made it easy to ride. It is likely the Savage was designed to be a low HP entry level bike that was in compliance with the restrictions on power/size that are required in the places where the bike is sold in larger numbers (The US is only a small fraction of the world motorcycle sales). It is also very likely they didn't want to make if faster than their bigger and more expensive V-Twin bikes.

The Savage engine can be made to run really nicely and be noticeably more powerful if you follow Drag Bike Mikes excellent threads - but it will never be able to make the kind of HP that a modern performance engine can make. My Cafe' bike has a Wiseco Piston, Stage 3 cam, some head work, intake and exhaust improvements, and a lightened flywheel. The bike weighs about 320 pounds and accelerates about the same as an 883 Sportster up to legal road speeds.....and that is quick enough to satisfy my speed needs. Sport bikes can easily leave me behind - but I still have plenty of power to keep my happy and with my increased power and taller gearing I can cruise at 75mph easily.