Engine

Testing Terms: Engine/Suspension *Updated*

If you learning more about your motocross bikes and also getting the lingo down, there is some help for you below. Here are some common terms that we use within the R&D industry that can help you explain what your bike is doing to tuners. Even if you just want to sound cool when you’re talking to your buddies, these terms will make you look like a regular factory test guy.

Suspension:

Pitching: This word is used when the rider lets off the throttle and the weight of the motorcycle forces the front end down. This usually happens when there is a lot of engine braking or the fork is too soft. The 2021 YZ450F was notorious for having a lot of this pitching when coming into a corner. Pitching can upset the chassis balance and can cause some oversteer through area 1 and 2 of corners. Pitching can also mean that a certain bike can squat (shock) too much under throttle out of corners causing the bike to have too much movement fore and aft. Pitching can make the machine seem unstable and cause the rider to not set up properly for corners. 

Hold Up: Hold up is mostly used when the fork or shock is riding too low in the stroke. When a rider is asking for more hold up he is usually wanting a stiffer compression setting so the fork or shock isn't “blowing through”. 

Harsh: This term has got to be the worst feeling to a rider. A harsh feeling is when the suspension is either too soft or too stiff. Yes, it can actually be both! If the suspension is too stiff the rider will complain about a harsh or firm feel through the handlebars. This stiff/harsh feel is caused by the suspension not being able to use all of its stroke. If the harsh feel is coming from the stiff side, opening the compression or the rebound can help alleviate some of this feeling. If the harsh feeling is coming from a soft sensation it’s because the suspension is riding too low in the stroke. Riding too low in the stroke can cause a harsh feeling because you are now in the mid stroke where the valving starts to ramp up to get stiffer. By stiffening the suspension a little you are now stiffening the initial part of the stroke which can actually make your bike feel plusher because your machine is riding higher up in the stroke around the track. “Harsh” is a tricky term because the cause of the harsh feeling can be from a too soft or too stiff of a setting.

Plush: I have never been a huge fan of this term, but the word plush means soft or supple feeling. If I hit something at speed most riders want their bike to feel plush and not harsh. However be careful when using this term to suspension techs as they may want to set your suspension up too soft. Plush can also mean the same with frame feel. For example, the KX450 has a plusher feeling to its frame than the of the Honda CRF450R. I like to use the term “bump absorption” more than the word plush. When the Kawasaki KX450 hits a certain square edge at speed, it has a better bump absorption feel than the Honda CRF450R. Off-road riders look for that plush feeling because they have less jumps to deal with and can hit roots/bumps at higher speeds. A softer compression setting or a faster rebound setting usually leads to a plusher feel.

Crust: We can thank air forks for this term. I came up with this term when I was at home during thanksgiving and I was watching my wife make a french apple pie. I always liked the middle of the pie more than the crust, so it immediately made me think of air forks. In order to get to the gooey goodness of the pie, I have to break through the crust right? Well air forks are the same thing! The top of the stroke of almost any air fork is called the crust because it’s usually has a hard/harsh feel initially and then you have some comfort. The crust usually gives you some deflection and a harsh feeling through the handlebars on small chop. We use the word crust because air forks usually feel like you have to break through the stiff portion of the travel in order to get to the softer/more forgiving portion of the stroke. WP has improved the air fork feel over the years so let's hope they continue down the path of a less crusty initial stroke on their air forks.

Empty: This term can be used when talking about engine character or suspension feel. When talking suspension empty usually means there is not a lot of damping feel. If you say “I feel like my end stroke is empty”, it means that it blows through or simply doesn't have any damping feel.  

Rigidity Balance: Rigidity balance is an important term when testing any chassis. If the bike has a firm feel and its rigidity balance is too firm it could mean that it corners excellent, but feels very harsh and has deflection on rough/fast straights. If the rigidity balance is too soft the bike can have a wallow feeling when under throttle as well as give the rider less confidence on braking bumps because of its unpredictable feel. Rigidity balance is something that every manufacturer works a lot on when developing their machine. A bike has to corner with precision, but also have enough comfort in order to have good bump absorption. A machine that has great rigidity balance is a Kawasaki KX450 because it turns well and can hit bumps at speed with a consistent feel.   

Performance: Performance is a word we used in the testing world when a rider is looking to ride at a higher level as well as be able to push the motorcycle without having it be too soft. Getting a chassis or suspension package to have better performance is basically asking the tuner that you understand that you’ll sacrifice some comfort, in order to get a machine that you can slam into obstacles harder without getting blow through. Usually riders that are faster or heavier want a performance based setting so they can hit jumps as well as bumps at a faster rate. 

 Comfort: A comfort setting is something most vet riders want so they don’t feel every little bump on the track. A comfort setting usually involves a softer setting that moves more in the stroke, but also can bottom out when hitting bigger jumps or larger bumps at speed. The 2021 YZ450F’s suspension package is a great example of blending both performance and comfort together. 

 Blow Through: This usually happens when hitting bumps/jumps hard and the suspension just dives without much damping force feel. If your suspension feels like it’s blowing through then you need to try and get a stiffer setting through clickers or internally with valving.  

Vague: Vague is usually a term used by describing front wheel traction. Front wheel lean angle traction can feel vague when the fork setting is too stiff, have the wrong offset triple clamps, or if you have the wrong compound front tire. A vague feel means that you will be washing your front tire out under lean angle and the bike may have less of a contact patch. Running too much air in your tire can also give you a vague feel.

 Damping Feel: Damping feel or force is the feeling of the suspension when moving down. Damping feel is used when explaining to tuners that you either have a soft feeling and need more of a stiffer setting. Damping feel can also be helpful/used when asked if the action of the suspension is too fast or too slow. 

 Deflection: Deflection happens when either a suspension setting is too stiff or a chassis setting is too rigid. Deflection happens when your front or rear end hits a bump/square edge and your bike simply doesn't absorb it. It’s like a pinball bouncing around from some side to side and can cause you to roll the throttle off in a hurry. Deflection also causes you to have less contact patch and makes the bike feel less planted. Going to a softer setting with the suspension or chassis usually alleviates some of this feeling. 

Contact Patch: Contact patch is a feeling of how much tire is felt underneath you. Contact patch can be increased by running less air pressure in your tires, running a softer suspension setting, chassis setting and/or increasing/decreasing offset. I like using this term a lot with my evaluations because without the feeling of a wide contact patch it will feel like you are running bicycle tires on your dirt bike. Having a wide contact patch feel gives you more confidence to roll the throttle on sooner when exiting corners. 

Engine:

Empty: This term is shared with the suspension side of things as well, but when a rider says that at a certain point that his power feels empty, he could mean that it’s a little lean or it just feels flat. Empty refers to a feeling where there is no more pulling power, or the power just simply feels flat (not exciting). 

Dirty Feeling: When a machine has a dirty feel to it that usually means the ECU/jetting is rich. A dirty feel means that the bike sputters, coughs, misses, etc., and most of the time it is due to a rich setting. Getting a dirty feeling delivery can also mean that your air filter element is clogged. You should clean it.

Recovery: Recovery describes how quickly a rider can get back into the meat of the power when missing a shift or when the machine is being lugged. Recovery is important because it gives the rider the confidence to know that if they make a mistake, the machine can get back up in the RPM’s and move down the track in a quick manner.

Excitement: Excitement is usually the initial feeling of the crack of the throttle anywhere in the RPM range. The Honda CRF450R is known to have a lot of excitement down low, but that excitement can also be a handful when rolling  corners. If a machine doesn't have enough excitement it also can suffer from poor recovery. See what I did there?

Lethargic/Lazy: This term is used for a machine that revs heavy or is slow to rev/spool up. A rich feeling can cause bottom end to feel lethargic/lazy feeling. Lethatgic can also mean that you will have to use the clutch a lot to get the engine into the meat of the power. 

Pulling Power: Pulling power is similar to torque feel. Pulling power is usually felt when the machine is exiting the corner or when driving up hills. The initial pop out of the corner usually reveals how much pulling power a certain bike has.

RPM Response: RPM response is the initial crack of the throttle anywhere in the RPM range. Excitement and RPM response can share the same meaning at times except when talking about having a lazy feeling engine character. Having good RPM response in an engine is important because it can help the machine feel lighter and more flickable.

Bottom End: Bottom end delivery usually refers to the power feel once immediately out of corners or when getting off the gate.

Mid-Range: Mid-Range delivery usually refers to the power feeling once exited from the corner and the rider is starting to make his shift into third gear. Mid-range feeling can be experienced in any gear but is only categorized by throttle position in the production testing world.

Top End: Top end is felt when a rider is full throttle and is accelerating down a straight. Top end can be felt in any gear but is most recognized in third and fourth gears on a moto track. How far the bike can pull each gear is usually categorized as top end.

Over-Rev: Over-rev is a term used by most testers as a sign of when the engine falls off its peak horsepower/top end. Having an engine with good over-rev means that the engine can pull each gear farther down the track without having to shift up a gear. Having an engine with a short over-rev means that the engine likes to be short shifted (up to the next gear early in the RPM range) and can't pull its gears very long.

Connectivity: This term is used when a test rider is trying to explain the feeling he has from this throttle hand to the rear wheel. Does his throttle and rear wheel feel connected to the ground or does the bike break loose or slide out? Good connectivity to the rear wheel allows for an easier-to-ride machine and can help the chassis settle down on rough tracks.

2022 Yamaha YZ250F GYTR High Performance Engine Kit

There aren’t very many OEM manufacturer accessory divisions out there that offer actual engine mods for their machines. Oh wait, there isn’t one! The only manufacturer that offers anything engine related is Yamaha. KTM used to have KTM Factory Services but that has been shut down yet GYTR is still going strong with a long heritage in the off-road world. I recently had the chance to test GYTR’s newest high performance YZ250F engine kit (which pulled me around to win the Keefer Vs. Keefer Part Two race) and thought why not dive into what is involved in the kit as well as how it differs from the stock 2022 YZ250F on the track. The 2021-2022 YZ250F GYTR kit comes with fully assembled cylinder head, high compression piston, air filter airflow kit, OEM gasket kit and a pre-programmed Vortex ECU for 3,199.00. GYTR also offers cams for this kit for an additional $699.99.

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Durability Criteria: 

Being that I used to work for the GYTR YPAD division (Yamaha Parts Accessory Division) in the early 2000s I have had some experience with their criteria for the durability of these types of engine parts. When the engineers decide on a power that they are satisfied with on the dyno, the Yamaha R&D team will build up a machine and proceed to take it out to a few tracks to see if it is in fact better than the stock. Not only will it have to be better, but also make sense for the cost right? After the decision is made that the engine kit is deemed worthy for resale, the durability begins. Japan usually requires all accessory parts endure 1000km of life before it can be passed for quality control. I have been a part of other manufacturers durability testing procedures and have found out that none (so far) have been as detailed as Yamaha’s. So the good news is that when you purchase a GYTR engine performance kit, you’re getting something reliable and tested. 

On The Track:

I will say that when I first hopped on the GYTR YZ250F, I wasn’t blown away by the power. That is until I rode a stock YZ250F back to back. Once I rode the stock YZ250F is when I appreciated what the team over at GYTR did with this kit. I will not say the high performance engine kit has more low end RPM response as I think the stock YZ250F still has more initial response down low, but coming out of corners is when you’ll be able to appreciate the GYTR power. You can shift later in each gear and even allows this old guy to ride third gear in more corners than the stock YZ250F. This is huge especially for a rider that is coming off of a 450 which might have too much power, yet still wants to ride his 250F like a 450F. The stock YZ250F is one of the few 250F’s in class to allow some third gear cornering, but with the GYTR kit it can increase that window even more. Mid range pulling power is more meaty gives you the feeling of more torque in soft conditions. The GYTR engine feels freer revving than the stock engine and also has less engine braking which helps the chassis on rough tracks. Top end pull is not a huge difference over stock but you can feel the GYTR kit pull harder on top with a little more over-rev per gear than the stock engine. 

Things I Would Like To Improve: 

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Even though I tested the GYTR High Performance Engine Kit with stock cams I think this engine could benefit from a longer top end/over-rev feel, which the GYTR cams can provide (tested them on last year’s engine). This engine likes to be short shifted, which is great for lugging or lazy riders, but for faster B class kids that love to rev each gear out extremely far, I still think the KTM and Honda have better top end over-rev capabilities. The GYTR engine package will reward you if you short shift which took me a while to pick up on, but once I did, this YZ250F was a weapon! I also would like to try the GYTR/FMF muffler system with the insert in, instead of with it out (like I tested). The insert in can give some added back pressure, which can give me some added low end rpm response. The FMF system could use some more bottom end and that could be the reason why the GYTR YZ250F lacks some of that low end RPM response. 

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Is It Worth The Money?:

That is the reason why we do these articles and videos right? Of course this question is only good for people that are actually interested in doing some engine work. Do you NEED this kit if you just want to race local and have fun? Absolutely not! However, if you want to get a little more serious against your 450cc’d vet buddies or maybe want to get a little more competitive in the amateur racing world, to me this kit is worth the money. Going to some private engine builders to build your motor can cost anywhere between 2500-5000. Along with that, your bike will be down for at least a couple weeks, so getting a complete high performance engine kit that is tested in house at Yamaha is worth the money in my opinion. I do wish the GYTR engine kit gave some more top end/over-rev, but I am pretty sure you can get more of that with some cams and another map on the Vortex ECU. 

2020 Suzuki RM-Z250 Blue Collar Project Part Two

Kris recently assigned me the 2020 RM-Z 250 to test and do a little project with. I have to say I’ve been having a blast riding it and trying to make it better. It’s a super fun bike to ride, despite the sometimes bad reputation it gets. If you haven’t read Part 1 of our build, check it out here: https://www.keeferinctesting.com/motocross-testing/2020/6/3/2020-suzuki-rm-z250-tipstricks-part-1

For a little recap of Part 1, the RM-Z is known to be a bit down on power in comparison to its competitors. Our goal was to find more power, without breaking the bank. Often times moto media outlets tend to throw the book at bike builds and I get why, but it’s fun to build a badass bike with all the exotic parts, but it’s not very practical for your real world rider, that is working 9-5. With that being said, we were able to find more power and make the RM-Z a little more exciting to ride, just by opening up the airbox and installing a pipe. 

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Continuing with the trend of giving the RM-Z more air, I tested the Super Flow Air Filter Kit from No Toil. The kit comes with a new air filter cage that eliminates the stock backfire screen and also comes with a high flow air filter. On the track I noticed more throttle response and an overall quicker revving/more free feeling engine character. In stock trim, the RM-Z feels choked up, like it’s starving for air. With my no cost mod of opening up the airbox, the No Toil kit completes the mission of getting more air through the intake. I was surprised at how big of a difference it makes in mid corner (area 2) recovery and overall excitement across the RPM range. Expect to find yourself upshifting sooner exiting corners as the engine revs up much quicker allowing you to pull taller gears sooner. 

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My next mod was installing Rekluse’s Torq-Drive Clutch Pack.  It’s a low cost alternative to their complete Torq-Drive kit. I’ve raced with Torq-Drive clutches for years in SX. They are an absolute must have for Supercross whoops, as it’s almost impossible to make them slip, but I’ve never tested a Torq-Drive back to back on an outdoor track and on a 250F for that matter. The clutch pack is easy to install as it fits directly into your stock clutch basket/hub and it’s almost a third of the price of their complete kit. 

The very first thing I noticed was how easy the clutch pull was. I’ve never been picky about an easy clutch pull, but I have to say, it’s nice having a buttery smooth feeling at the lever. On the track you’ll feel improved bottom end exiting corners and an increase in pulling power throughout the whole RPM range. It’s an interesting feeling, because I wouldn’t say that the bike makes any more power with the Rekluse, but it just does a better job of putting the power you already have to the ground. As Keefer would say “more linear”.

I tested this clutch kit at Glen Helen and where I noticed the biggest difference was down the deep tilled start straight and up the hills. I felt like I could rev the bike less yet still get more forward drive. Rather than revving high and getting a slight amount of slip with the stock clutch. I’d imagine as I continue to make mods and find more power that the clutch will make an even bigger difference. Where the stock clutch would slip under a heavy load, the Rekluse hooks up and drives forward. With a couple pretty simple mods we’ve  been able to find some more power and make the RM-Z motor more competitive, and for a relatively low dollar investment.

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My next goal was to improve the chassis. If you’ve ridden the stock 2019-2020 RM-Z250 you’ve probably noticed the forks are STIFF. I’m a 180 lbs Pro and they are too stiff for me, so I can’t imagine a normal weekend warrior type of rider. Unless you’re 200+ lbs or just want an extra stiff setup, expect to have your suspension re-valved or at the least re-sprung. 

Of course we sent the suspension to Race Tech where they re-valved it with their Gold Valves and installed lighter springs front and rear. I’m usually very picky on my suspension setup, and I have to say Race Tech nailed this one first try. The chassis on the RM-Z is still slightly on the stiff side, but it’s very predictable and corners like a dream. Race Tech’s mods gave me more comfort in the front end end and overall calmed down the chassis. I truly have no complaints about the suspension (which is super odd to me), I found the comfort I was looking for, but still retained good bottoming resistance and hold up on big hits. Having a softer setting helped the bike settle more and turn even better than stock, and also gave me a little more stability through high speed chop. 

I’ve truly been having a blast riding the #RMaRMy. Being a 450 guy for the last few years, it’s been super fun to ride and the few mods we’ve made, have made a huge improvement in making the bike more fun, as well as more competitive. I have a few more things in mind that I think will make to 2020 RM-Z250 even better, so stay tuned for a Part three coming soon.