Why doesnt MXA or Keefer do a simple weight test

I guess it depends on where the weight is. 

For example if the weight is added to the skid plate 7-10lb probably doesn’t feel too bad, might actually help in some areas. Adding 5-10lb to the top of the engine would change the bikes center of gravity and feel very different on lean angle and change of direction.

I know it’s a very different beast but I’ve done a lot of testing with weights and tuned mass damper on mountain bikes. My current downhill bike has 4lb under the bb and 1.5lb on the fork. The bike is in total 41-42lb and it’s the most planted bicycle I’ve ever ridden.

Some dh pros put lead ballast in their crank spindles. 

Yeah, I have that. I melt it down and pour in the spindle. Lots of places to hide it, but personally I don’t think it’s enough, so I just strap lead scuba weights under the BB.

Back to the topic, when we did some of the vital shootout bikes tests I don’t remember any riders saying one bike or another felt heavier or lighter on the track from physical weight standpoint.  But I think good and bad mapping can do more to make a bike feel heavy/lethargic or lighter/flickable.

Agreed, qMapping / engine character effects a bikes weighted feel more in my opinion. For years when KTM was chasing having the lightest 450, I commented that the Kawasaki that weighed nearly ten pounds more felt lighter in action, due to the connected feel and response of the engine at that time. The KTm then just felt like a tractor…

Swing a 8lb. sledge and a 12lb. sledge, that would seem to be a good test. More weight is harder to start and stop, but hits with more force. Or as RC would say push a wheelbarrow with 100lbs of dirt through mud and then one with 150lbs......

It depends where you take and add weight on the bike? Im not good by any means but I can tell weight and how the bike reacts to and o-Ring chain vs a stock chain, a Tusk rear rim to an OEM

I could not tell you the difference between a case cover or a steel exhaust vs titanium in matters of weight.

In terms of rider weight it also goes to riding style, body proportion, just adding a weight to a guy wouldnt do anything also bikes are meant to be tuned and set to weight

Because the lap times wouldn’t change.

Same reason they don’t post lap times with exhausts

Or ecus

Or clamps

Or tires

Or anything.

They rave about how massively improved certain things are and they never show you. It’s all feeling.

These guys can’t feel 5 seconds a lap faster or slower by going onto a 350 450 or 250 let alone 2lbs.

It’s all bullshit.

Well.... its not alllll bs.

The average guy can feel old tires vs new,  a new bike vs old, or fresh suspension vs worn.

A few years ago a dude on Instagram built a lightweight KTM 2 stroke. 

It was cool to follow. Dude spared no expense and get pretty creative. Even had a bunch of custom machine work done to lighten stuff up. 

I can’t find the account now unfortunately. 

Everything is a compromise. Making a bike as light as possible with no other consideration will not result in a great bike to ride. enduro_builds on Instagram did a 150 build (fuel injected non-linkage bike) taking as much weight out as possible, but without much regard for anything else. The bike ended up at 186 lbs with fuel, but I bet it rode like hot garbage. Super flexy, smaller tires than it should have, 3d printed plastic levers, holes drilled in everything, etc. 

The right thing to do is make the bike as light as possible without compromising performance. You still need durability, good tires, good suspension, etc. My 150 build (carbureted linkage bike) was just that and ended up at 201.2 lbs full of fuel and ready to ride. Stock is 203.6, so not a lot of weight dropped, but I also added much more durable wheels, a spring fork, skid plate, Honda damper, billet ignition cover, etc. For comparison, my previous 150 build was about 10 pounds heavier than stock as I just added all that on without thinking about the extra weight. The current build is also around $30k all added up, though! 

Improvements may not show up in single lap times but over longer moto......Even then it is impossible to get accurate data because of the thousands of variables in MX. The track is so dynamic that even lap times become irrelevant after a certain number of laps. Take F1 for example, they claim how 1 kg (2.205lbs) of weight can add 4.4 seconds to the total time of a Gran Prix. The tighter the track the more the extra weight is a penalty.

A lighter bike will accelerate quicker and brake quicker (all things equal) because of, ya know, physics. 

I guess another variable for weight test is how much mud and dirt is sticking to your bike. If it cost $10k to drop 5lb off your 450, then you go out in first practice and add 10 lbs of mud vs stock bike and you go out later in the day when it’s dry and no dirt clings to your bike.

Doing a lap time test with different weights is an interesting idea, but difficult to implement. Adding the weight in different spots will have different effects. If the weight was added right at the center of gravity, the bike would probably feel about the same to ride as it doesn't change the moment of inertia much at all. But if that same weight was added spread out over the bike, it will definitely change the feel. And it would be entirely different if all the weight was added to the rims as you have rotating and unsprung weight. You'll also have to adjust suspension for the added weight, and even change spring rates once the weight change got high enough.

If weight was added near the center of gravity and lap times were compared, I bet you wouldn't see a huge time difference in a single lap, but the rider will have to work harder to make it happen. 

If you were to run a 30+2 moto with two identical bikes, one heavier than the other, you'd definitely see a difference in time and/or rider fatigue. It's just simple physics. The rider has to deal with moving that extra weight around and it's going to wear them out faster, which will result in longer times. They can minimize the time hit if they're in amazing shape, but they will be more fatigued at the end. 

That’s the guy I was thinking of. 

I remember he even had the spacers that are inside the hubs milled down to make them lighter. 

Motocross,  the only motorsports where the laws of physics don't apply. 

And one of the most grueling physical sports where performance enhancing drugs don't work.

Apparently....

Do four laps with a 1/4 tank of fuel and then do four laps with the tank topped up. Should be around a 10 pound difference in a less than ideal location for added weight. 

enduro_builds is new IG name. KTM 150 starting weight 97kg/213lb --> ended 79,6kg / 175lb so weight lost total was 17kg / 38lb

Back in the day I rode my buddies KTM 450 - it felt 50 lbs lighter than my ‘15 YZ450. This was especially noticeable in the air..That is when I switched to KTM.

I think weight is way more important than engine with a 450. 450 already has more power than most of us need, its weight I need less of- mostly after a moto trying to put it on the stand full of mud..😆

A gal of gas weighs 6+ lbs.  I feel a difference between 1/2 or full.  On a 125 i don’t worry about wt.  just sag,clickers and jetting .  Your body wt is more important than the bikes.  Not sure why but I,m not 172 anymore as my regular wt.  I,m 162 ish.  I notice the difference riding. Wayy f ing faster 

Don't for get that brilliant shock linkage ratio they came up with so they could put on a lighter shock spring to save weight! Even though that linkage was horrible. I fought that thing with various valving changes to the shock (light LS compression and lots of HS compression shims to try and valve around it). I wasn't getting the feel I wanted.... lt wasn't till I ran into this guy down the street that had a garage full of Alta motorcycles that I got a clue what was going on. l stopped by one day and started talking to him.... Ask him where did he get all the Altas'.... he told me he was the chassis engineer (as was his room mate) for them up till they closed. He bought a few on the cheap as the doors were being shut. I said ... "interesting" and started talking to him about the shock valving challenge I was running into on the KTM. He said "oh - here is what happened" and he pull out a felt marker and some cardboard and drew the linkage curve of the earlier KTM linked bikes and the 2016 + ones. Told me Alta adapted the 2015 ish curve for their bikes. I said interesting... how does he know this about KTM ... He said "You know who Dave Arnold is?" I said the guy from Honda? He said - "yes - we hired him as a consultant and I worked with him on the chassis and linkage curves. He did some work for KTM before we hired him". 

In your experience, what kind of adjustments would you make to counter weight added to the front of the radiators? I added some nice cast aluminum supports to my 250 xcf, but the downside is they added 4 lbs. I thought about maybe sliding the forks down a line or adding more compression, but just really just taking guesses to improve balance. 

It was interesting Mosiman comparing lap times from KLX 230 to a KX 450 to a CRF 150R in MXA's video. As far as weght goes, I ride a lot of off road and my bike with a lot of body armor, heavy tubes, the big fuel tank, is no where near as agile or nimble as without that stuff. Might be just as fast, but I can feel every extra pound as cumbersome.

Because weight doesn’t truly matter… A bike can be heavy but feel light depending on ecu setting/how much excitement is has. Look at the Kawi it doesn’t have and hit and feels heavy but it’s not. Weight can also be good, look at the first gen 450X it weighs 270 but honestly corners like a dream and is so stable. IMHO I don’t mind weight. I’ve owned a couple of WRs and would choose one of those to go race a GP vs my 24’ YZ450. 

They should do a blind test with adding a 5 or 10 lbs skid plate and record lap times. Weight could be added higher up under the seat and hidden for a blind test. MXA dosent need to do it; VITAL!!!

Haha the Ricky bit made me laugh. Nice work

What would be really interesting would be to pick a few points on the bike, may something like under the frame rails (where a skid plate would go), in the air box, and on the swingarm as points to add or subtract weight.  Then, create a 5lb weight as well as a dummy weight that looks exactly the same for each point.  Have the test rider ride the bike in a certain configuration, then without telling them what the change is or allowing them to see you work on the bike either add or subract the weight from one of the points on the bike.  Send them back out, and see if they can detect a change (if there was one made at all) and where on the bike it was located.

This would be an interesting test of how in tune some of these test riders are, and how much weight actually matters in the grand scheme of things.

Imagine a world where shootouts would be won by a bike with the fastest laptime (and not a bike some test geezers prefer)...

I feel like weight matters to some degree, but like ML mentioned above, like around '17-'18 or so, the KTM/Hus 450s were really light but didn't really feel like it, to me. Also, I think back to when Roczen was on RCH and there was an article on that bike. And the RMZ was much heavier than the KTM at that time. But the RCH bike supposedly wasn't that much lighter than stock. It was lighter but they didn't go crazy to chase that low limit because they felt like weight balance was more important than the actual number itself. So I always found that interesting. I do think where the bike carries the weight does matter though. And the engine character does play a big role into the feel of the bike.

Meth is good for weight loss.