Lighter flywheel effect?

[andyvh1959]

We've all ridden bikes that seem to "snap" to our twist of the wrist. Some just seem instantly connected to our brain that when we twist the grip the engine responds with that crack of power response. Other engines, well, they seem to respond as "yeah, yeah, yeah, we'll get there, just take it easy bucko." Some v-twins like a KTM have the "crack" response, some v-twins like our beloved Vulcans are a bit more of the "hang on, we'll get up to speed." Engine response of a big v-twin relates a lot to spinning weight in the engine, flywheel effect. But also, a lot of flywheel effect also makes an engine smoother.

So, MAS and DL, does the typical Vulcan 1600 have a lot of flywheel effect? Can the major spinning parts in the 1600 be altered in a manner to produce sharper response and still not make for a buzzy edgy feel? I once rode a friend's FXRS-EVO Harley with an engine built by a drag race boat engine specialist. It had the "crack" of a big NASCAR engine, spun up quick, great throttle response, yet was easy to ride in town. Whack open the throttle and HOLY CRAP!! It dyno'ed at 100hp at the rear wheel, but was still easy to ride. It's a Harley I would love to own.

[MAS Tequila]

If you want a sport bike, then get a sport bike.

Your Vulcan will NEVER perform like they do.

You have 2 pistons of 750-800cc's each.

It will NEVER rev out like your talking about.

A lot can be done, I've seen Meanie engines with flat track Ford 5.0 pistons in them, that doesn't mean anyone without engine building experience should try.

The shorter stroke 1500 does rev out quicker than the 1600.

Enjoy your bike, it will never be something else.

[Mechaniac]

I ordered a spare Mean Streak Flywheel. It looked heavy in the pic and was really heavy, when passed around everyone commented "Holy Shit". A non-scientific bathroom scale reading was 19 lbs. I've installed flywheels in cars that weighed less with excellent results. So I took a ride over to a good friend who has an race car business. He has lathes and balancing equipment. At first look he didn't have a cone quite small enough to chuck it on a lathe but told me it wouldn't be a problem and he could modify one or get something. It's been a week and he just sent me a pic of the results and said "It's ready". One look at the pic and "Holy shit, sweet."

Factory VN1500-1600 flywheel vs. lightened :

MSOEMwheel (2).jpg

MSlightwheel1 (2).jpg

I'll see about getting a accurate after weight and a report on how it turned out once installed.

Vernon

[andyvh1959]

Curious to read about the results and especially the ride-ability.

Only other bike I have experience with a lighter flywheel is my 1976 BMW R100RS. The stock flywheel was very similar to one out of a mid-60's Volkswagen, heavy heavy. The lightened flywheel let the engine rev up quicker, more responsive. But a flat twin 1000cc BMW is a lot different than a 1600 V-twin. BMWs like to rev, and will be running great all day at 4500 rpm. A Vulcan 1600 starts feeling real busy at anything much over a steady 3500 rpm even with the heavy flyweel. Usually a heavy flywheel is key to that smooth steady highway feel. A lighter flywheel can result in a buzzy feel to the engine.

[Mechaniac]

Update, I picked it up from the machine shop and damn it was still heavy. Despite a visually dramatic reduction in outer mass, it only dropped about 4.4 lbs. It was in the most effective place to reduce inertia but based on current experience levels I don't think this will be a negative impact. There are still 15 lbs. of steel there for a relatively light weight 1600 with fuel injection that's mostly ridden solo.

Vernon

[andyvh1959]

I agree 15lbs is still a heavy flywheel, but it was almost 20lbs originally? Did the machining remove more mass out near the circumference? Where the weight is removed also has impact on the results. Also, does the Mean Streak flywheel weigh less than the Nomad flywheel? These diagrams show different part numbers for the Classic and Mean Streak flywheels. By appearance the Mean Streak rotor looks lighter than the Classic rotor. If the Mean Streak rotor fits the dual stator setup of the Classic then it would reduce the flywheel effect and weight.

Really curious to read your results after the engine is back together. A 50 degree V-twin will react to a lighter flywheel different than that say for a flat twin like my 76 BMW. The bore on the VN1600 is 4.03" and on my 76 BMW its 3.70", so much more piston mass. But the stroke on the VN1600 is MUCH longer by almost a inch. Generally speaking a long stroke engine produces less secondary vibe force than a shorter stroke engine. Plus it is a much lower revving engine than a BMW flat twin. Also being a V-twin the secondary vibes move in a more fore-aft plane than the vertical plane of a flat twin.

The flywheel for my 76 BMW R100RS was lightened down to about six lbs. It did result to shift quicker and rev quicker, but the big flat twin is buzzy, which was typical for the big airhead of that era. That bike is also carbbed, and being a flat twin it has inherent good primary balance. But secondary vibes are present when the engine nears mid stroke and the crankshaft flyweights are nearing their upper/lower positions.

[Mechaniac]

Installed and tested, it's all good.

I finally had a weekend without anything else to do and the wife running an errand with her sister most of the day so I started in on this flywheel/generator rotor swap.

I had read through the factory repair manual a few times and was expecting to have to remove the generator inner cover which required oil drain, tank removal, and front mounts disconnect, loosen rears and raise up the engine to get the inner cover out of the frame. I pleased to say that wasn't necessary at all. The repair manual for some reason assumes that while you've have the generator off you will disturb the engine timing and then need to go about retiming it in order to line up the rotor correctly. Fact of the matter is that if you're just changing the rotor all you need to do is take it off and put it back just like it was. To do this all that needs to be removed is the chrome outer cover and the small generator outer cover.

Once I had the smaller outer cover off I could see that the rotor should be able to come right out at this point. So I rotated the crankshaft until the "R" mark on the rotor was at TDC and removed the bolt by putting the gear box into 4th and standing on the rear brake pedal while backing the bolt out with an battery impact gun. After the retaining hardware was removed it just lifted right out with ease.

I spent the most time cleaning off the stuck on Graf foil gasket material and cleaning any of these debris out of the crankcase.

The crankshaft end and rotor hub have one large spline so they only mate one way. So the timing procedures are for making sure the other bits are lined up and not the rotor itself. The large mechanical diode that Kawasaki calls a Ratchet is splined the same as the others so it needs to be placed on first without the washer and bolt so it can be properly lined up. I had to improvise a way to hold the crankshaft rigidly in order to apply the proper torque. Tightening the bolt standing on the brake again wasn't cutting it and this turns the crankshaft backwards which can cause all sorts of tensioner problems on the chain drives. After getting some excess turning holding the brake and hearing a tensioner pop noise that had me freaked out until the engine was thoroughly wrung out several times I looked at what I had to work with. There's not much to grab onto and what is with the inner cover on requires a stout strap wrench that I don't have, the smaller plastic oil filter kind wasn't going to hold that much torque. Kawasaki has a "Flywheel Holder" special tool that grabs two sides of it in machined in divots that were still below the cover I hadn't removed yet. The balancer gear that the service manual is so worried about timing is the only other thing (partially) exposed besides the outer drum of the rotor. The balancer gear has many small holes so I grabbed a 6-8" punch about the same size, like a pencil, and stuck it into the most available hole with the Rotor R mark at TDC and without any further fiddling it held rock solid while I torqued down the bolt to 58 lbs./ft. . I don't know what it found and wedged but it worked like a charm without anything sketchy occurring. I've been doing this for 35+ years and I endorse this. Your results may vary, proceed at your own risk, LOL.

I was optimistic at this point but hoping I hadn't done any damage with the pop noise. So I put the gear-box back into neutral and turned the engine in the correct direction many times using the same bolt. I never had any indication of a problem so I sealed it back up and put all the outer stuff back on, chrome, shift-lever, and left foot peg. I fired it off and it started right up and did the usual stuff and quickly quieted down and started idling low and a little rough, same as normal. I adjusted the fast idle up to about 1200 RPM and watched and listed for a about a minute. Then I blipped the throttle a couple of times and it seemed to rev up quicker but not the sport-bike style instant rev-limiter bouncing non-sense. I shut it off to do a couple of other minor things. replace a tank drain hose and install a charger plug harness. After I was done and everything was back together I put my truck in the shop and pulled the bike out and went for a ride.

Pulling away from a stop, out onto the road and in traffic wasn't any more difficult than before. There were no stalls at all today without any further ado. Once accelerating the engine just revs up much easier and smoother. Meaning less throttle than before to achieve the same rates of speed in traffic. Less throttle equals a little less noise and a significant drop in Noise and Vibration Harshness (NVH). So far I was really liking it and grinning. Once I got on the highway leaving town and going to my house I was able to start doing some WOT acceleration runs. Wow, the gear changes are coming super fast. Used to I would try to time shifts so the engine would always fall back on it's torque peak but today it was all I could do to keep shifting at the 6K red line knowing that the torque peak was past but the bike was accelerating so fast I couldn't keep up with it. I found myself doing over 55 in 4th gear and not 'knowing it' a couple of times. Usually I can be in 5th and occasionally try to shift another gear. Not anymore, it's so smooth and requires less throttle that I keep having to reduce my speed because it wants to run.

On a dead stop hard launch WOT drag strip type of run the bike launches well and I can get wheel spin by being heavy handed on the throttle in first gear. When I do a hard performance shift into 2nd gear on this bike at redline in first it always broke loose the rear wheel for an instant and the rear suspension bucked. Now under the same conditions the rear bucks twice. Then it's shift shift shift, holy cow this things moving out shift.

The speedo is way off and it gets worse as you gain speed. I have a Garmin motorcycle GPS and I had put a mount onto this bike a while back. I didn't think to check the 'trap speed' at the known quarter mile mark from my favorite stop sign because I was so intrigued by the incredible increase in acceleration that I was watching the GPS speed and didn't note exactly when I passed the 1/4 mile mark culvert that I normally check my junk's mods against. Just earlier when I have attempted to top speed the bike it started surging at 110 like it was having a fuel volume issue but this time it was still pulling hard so I tucked in and held it to see where it would go. It achieved 115 on my GPS (about 120-125 on the speedo). I realized that I was approaching my street corner at this high rate of speed and would be better off passing it and coming back than do a full tilt stop at this speed just because I could. (this is a straight section of country highway with good visibility).

So I decided to use the fire station lot to turn around just past my road. Wouldn't you know there's John Law hiding just in the tree line who had to have been hearing and watching my shenanigans with interest. Yes I was already slowing as I got close but I had just been clocking triple digits with all the exhaust noise to go with it a few moments earlier. Out of caution I sped back up and passed the fire station. He wasn't moving so I didn't know if the SUV was manned or he wasn't planning on talking to me so I decided to use the next street corner to turn around. I pulled in an made a U-turn and rolled back up to the stop sign. Sure enough here he comes with a full head of steam. I'm like fuuuggggeee. Just then two 19 year old looking guys come over the rise from the other way towards the cop and low and behold these clowns are riding dirt bikes without lights and plates AND doing marathon wheelies at about 50 MPH. I'm not sure if the cop even saw me sitting there as they passed each other just past me. The two guys set their bikes down as the black SUV with COP equipment passes them and they jam the brakes and pull into the street I'm sitting at. They stop and the guy in the lead says to me "Holy *Y^%" was that a COP?" I'm like "Yeah, but I just passed him at 110!" They laugh and we watch him further speed off into the distance. and I said, "I guess he's sick of us and is getting out of here, we all get motor bikes and don't know how to behave." We all laugh again and mutually talk about let get out of here before he changes his mind. I pull out and zoom back to my street and they take off down the one we are on.

CONT.

[Mechaniac]

I changed into social clothes and rode about 15 miles to a favorite biker bar. Some light rain here and there going and coming back about an hour later. The lighter flywheel is actually easier to modulate. For instance, when slowing down rapidly, like when seeing a cop at 115, the back wheel used to lock up and make a short skid often as the clutch was released in a lower gear. The engine was resistant to revving up to let the rear wheel maintain road speed. But now with the lightened flywheel this never happens, the engine just jumps up in revs and provides smooth delivery of compression braking without causing the rear wheel to skid.

Like any time I've installed a lighter flywheel overall drivability is improved, smoother shifts and easier to modulate throttle.

I like to come to a complete stop at say a stop sign just for a moment and keep the engine revved up a little so the flywheel acts as a gyroscope and helps me maintain balance so I don't have to put a foot down then take off quickly. I can do this like in a bike rodeo slow race and it just makes driving around easier. I can still do this even though the flywheel weight is significantly less, but I already have gotten good at this so there's a little skill there.

More vehicle weight may add to a reduction in drivability but I can't see it at this point. I'm 200 without my boots and gear, prolly 215 fully dressed and helmet. My wife is about 115 without gear and she rides with me quite often. If the next time she rides on back I find any issues I'll update but I can't see anything now that leads me to believe there will be a problem. A full dresser Nomad with two heavier passengers would be the test for this.

So overall I can't find any drawback or compromise from this and can recommend it fully. The bike runs better and seems at least half a second faster in the quarter mile grand prix. This doesn't require much money to duplicate and you all already have the part you just need to take it out have it turned down and put it back on, reap benefits. Just a gasket and machine shop fee. Mission accomplished.

I wouldn't be surprised if the one arrogant guy with the big engine Hogg is within even acceleration with me on this bike now. When Racing Ray gets through with the compression/bore increase and cylinder head work with the 1500 MS cams I think I will be able to embarrass him and deservedly so. He's one of those guys who doesn't know where the turns are and keeps passing them but then turns around and makes sure to pass me with that GPS on the right path before he misses the next turn.

I just think a bike named "Means Streak" should be ornery as Hell. This is a solid step in that direction that seems to be a no loss mod.

Vernon

[andyvh1959]

Thanks for the details and report. May be something for my build. The 1600 will never rev like anything close to a sport bike, or for that matter not even close to how my BMW R1200 revs (which it likes to do). But if the 1600 can feel a bit more responsive, then I am for it.

[mick56]

Originally Posted by Mechaniac

I changed into social clothes and rode about 15 miles to a favorite biker bar. Some light rain here and there going and coming back about an hour later. The lighter flywheel is actually easier to modulate. For instance, when slowing down rapidly, like when seeing a cop at 115, the back wheel used to lock up and make a short skid often as the clutch was released in a lower gear. The engine was resistant to revving up to let the rear wheel maintain road speed. But now with the lightened flywheel this never happens, the engine just jumps up in revs and provides smooth delivery of compression braking without causing the rear wheel to skid.

Like any time I've installed a lighter flywheel overall drivability is improved, smoother shifts and easier to modulate throttle.

I like to come to a complete stop at say a stop sign just for a moment and keep the engine revved up a little so the flywheel acts as a gyroscope and helps me maintain balance so I don't have to put a foot down then take off quickly. I can do this like in a bike rodeo slow race and it just makes driving around easier. I can still do this even though the flywheel weight is significantly less, but I already have gotten good at this so there's a little skill there.

More vehicle weight may add to a reduction in drivability but I can't see it at this point. I'm 200 without my boots and gear, prolly 215 fully dressed and helmet. My wife is about 115 without gear and she rides with me quite often. If the next time she rides on back I find any issues I'll update but I can't see anything now that leads me to believe there will be a problem. A full dresser Nomad with two heavier passengers would be the test for this.

So overall I can't find any drawback or compromise from this and can recommend it fully. The bike runs better and seems at least half a second faster in the quarter mile grand prix. This doesn't require much money to duplicate and you all already have the part you just need to take it out have it turned down and put it back on, reap benefits. Just a gasket and machine shop fee. Mission accomplished.

I wouldn't be surprised if the one arrogant guy with the big engine Hogg is within even acceleration with me on this bike now. When Racing Ray gets through with the compression/bore increase and cylinder head work with the 1500 MS cams I think I will be able to embarrass him and deservedly so. He's one of those guys who doesn't know where the turns are and keeps passing them but then turns around and makes sure to pass me with that GPS on the right path before he misses the next turn.

I just think a bike named "Means Streak" should be ornery as Hell. This is a solid step in that direction that seems to be a no loss mod.

Vernon

Why would you change down so many gears, that the back wheel locks up ? That's what the brakes are there for.

[RACNRAY]

Great job Vernon, sounds like the amount of weight removed was spot-on with no negative affects.

Got ur cylinders cleaned up at the top and bottom flanges and ready for the new sleeves when they come in, The bottom o-rings were not as bad as I have seen in the past!

The heads are blasted so today I will be taking numerous measurements to determine where and how much to remove/reshape the ports.

I am surprised at how thin the margins are on these valves. I ground the valves from the rear head, 2 were bent/warped and no good, the 2 that refaced well had dangerously thin margins, thus the need for new valves.

In checking spring pressures seat and full open were a bit low, so shimming up the springs got me where I wanted for pressure and keeping the springs .100" from coil bind. The H.D. spring kit that is available has some seriously high pressures and I saw no benefit for the cost.

I tried to upload pics but the files r too big!

RACNRAY

[Mechaniac]

Thanks for the update Ray. 10-4 on the valves and springs.

I had my wife on the bike with me most of the day yesterday, no difficulties were noticed with the lightened flywheel despite another 125 lbs. load.

Vernon

[andyvh1959]

All good info, I see a lightened flywheel in my future for my pumped up VN1600TCMS, Tour Classic Mean Streak.