Wheelz: intake, and best performance bang for buck

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Wheelz: intake, and best performance bang for buck

Postby Wheelz » Thu May 14, 2020 19:18 19

Here I will discuss an area where there is some, but still limited information for our bikes. Keep in mind I have a MKIII Tmax 500. There are differences going newer, what I say may not fully apply.

When it comes to air intake there are few performance items available, solely from Jet Prime (Malossi offers velocity stacks, throttle bodies, and an open air filter kit for the 530 but not the 500). I am not concerned here about the variety in air filters: stock, K&N, Sprint, or whatever other variants are out there. The controversies around which of those work or don't is limited to the filter. Jet Prime has pretty complete coverage, from velocity stacks to bigger throttle bodies to a complete airbox replacement. Concerning Jet Prime's stuff, I will say the following:
1. It's expensive.
2. The airbox is designed to encompass the throttle bodies, themselves, and as such has dubious sealing on numerous points of entry. It might be good in practice, but the design is questionable.
3. I have my personal peeves with Jet Prime's customer service. Unlike Malossi they do not have their install manuals available online (if they even exist, at all), and their tech support is obtuse (I've dealt with them concerning the velocity stacks and their Superlight clutch, it was exasperating to get pertinent details, and info was incomplete or incorrect).

However, Jet Prime were the motivation for me looking into the air intake for our bikes, as they claim there are significant gains to be made in this area.

It makes sense. On most every vehicle I've owned opening up the intake has yielded benefit. The most dramatic was on a Suzuki DR650. The snorkelectomy with a shimming of the slide needle is a popular stage 1 mod. Before: no throttle wheelie. After: throttle wheelie. The benefit might be super minimal, but in some cases only a minimal increase is needed to give that extra amount of snap that equates to actually getting the front wheel off the ground or spinning the tire accelerating out of turns.

What's the compromise? Intake noise/honk. Another mod on the DR650 is to remove the fire screen immediately before the carb entrance. I did this and was subjected to a painful hammering noise in the midrange. Screen went back in, noise disappeared. Same for the SV650 I had. There is a center snorkel on the air filter that can be cut out. Too loud for me.

Noise is very subjective. Noises affect different people differently. Hence, when I talk about honk below, know that it is my subjective experience.

On to the experimenting. I will make this short.

I got a great deal on a stock airbox off Ebay. I will talk first about the second mod I did: homemade velocity stacks. Velocity stacks are not hard to find. They are simple intake cones that come in various diameters, lengths, and shapes. Jet Prime's are computer engineered and fancy. The more you look at velocity stacks it seems that the more you pay the more subtle the engineering seems to be. I'm not mocking the engineering, but I am saying the obvious differences are subtle. I thought I could do as well as Jet Prime for a lot less. I got some stacks off Ebay and modified them to fit in the original, cut-off manifolds.


You may notice the IC-2000 rubberized cyanoacrylate. Phenomenal stuff. I can't rave about it, enough.

Bottom line for this mod is that the intake honk was significant, super obtrusive, and power increase was not noticed. Does that mean Jet Prime's velocity stacks don't work? I'm sure they do, but in my experience the intake noise for my particular ghetto version was a major deterrent. Even if there had been a power increase the intake honk was too much for me. As in, anytime I accelerated I regretted it. I may revisit this mod in the future.

Concerning Jet Prime's obtuse tech support I was told their velocity stacks were replaced via access through the airbox. Somehow the expectation is that, without removing the airbox, one can stick one's hand into the airbox filter opening and remove the existing rubber manifolds from both the throttle bodies and the airbox. I'm going to call bullpoop on that. The stock rubber manifold/velocity stacks are practically glued to the airbox. Any modifications to the existing velocity stacks will require airbox removal. Which I found is a lot easier than I expected. The front fender needs to be removed but not the front wheel. The clamps on the manifolds to the throttle bodies should be rotated, so that they can be accessed from above and not the sides (which unfortunately necessitates removal of the side bodywork). In order to rotate the clamps for future ease there is a rubber nub on each manifold that keys to the clamp. This needs to be cut off, then the clamp can be rotated "properly."

On to the best performance bang for buck.

Cut the airbox lid open.


Airbox lid.jpg

Airbox lid1.jpg

Reasons why this rocks:
1. It's an easy mod to do. Perhaps you don't need to cut out as much as I did, you could simply use a hole saw to drill two big holes, not sure. But, cutting out the plastic is easy. I drilled holes and then used a tiny saw. A hacksaw blade would even work. Just make sure to file everything clean so you don't have plastic chips contaminating your air filter. The amount I cut out is the max, possible. No more of the lid can be removed without it affecting its ability to hold the filter.
2. It's reversible. Don't like the mod? Just tape the lid back up.
3. It's noticeable. I'd done numerous back to back tests, since I had both my original lid and the modified one, and the difference was noticeable. Sometimes it was subtle, other times it was obvious that my bike was running so much better.
4. Besides the fact that you don't need to buy anything (assuming you have tools) there is nothing further that needs to be done. I didn't change anything else on the bike. No changes needed to the fuel, etc.

What's the downside? Increased intake honk. How much? For me, the benefit outweighed the downside. One way I combatted the honk was by gluing a piece of yoga mat to the inside of the cover that goes over that area. It did take off the edge. More recently I've gotten a newer, nicer helmet, and now the honk isn't even noticeable anymore.

If you want more character from your bike and don't want to risk getting an exhaust that is regrettably loud do this mod, first. Fully stock muffled our bikes do lack visceral character. Add some induction roar and now we're cooking.

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Re: Wheelz: intake, and best performance bang for buck

Postby kjlars5 » Sat Jun 13, 2020 20:40 20

I too have a 3rd Gen, but a 2011. Really appreciate your posts. Had bought mine almost 3 yrs ago with 13k miles & now have 23k. Like you, I've had many bikes over the years. My '99 SV650 tons of mods, tons of fun. I replaced my belt last summer with apprx 22k miles. At the time I also installed Dr Pulley 16g sliders. HUGE change in performance, although on my Burgman 400 the sliders made more of a change. I'd probably go to 17g on the TMax if I was to do it again, reducing RPM.
Regarding your airbox mod, you say it made a difference in power-
Was it just at full throttle, or did the mod help at low end too? I had a Burgman 650 that I did similar to & that noticeably reduced the low end torque, & also the bike sounded like a vacuum cleaner too.

I rented a 2018 BMW C650GT over the winter & really enjoyed its high speed, heated seats/grips & power windshield, but when I got back on the Tmax, it felt like home.
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Re: Wheelz: intake, and best performance bang for buck

Postby Wheelz » Wed Jun 17, 2020 1:34 01

Hey Kjlars, nice getting some response, here.

The answer is tricky. Very tricky. I will try to be succinct, here, as this could become a long discussion.

I am running Malossi's Sport variator. I've run it for more than a couple thousand miles, and it's been great. Recently I did some more fiddling with my variator and reinstalled the stock one with Dr. Pulley 16g sliders. I hated it. Very few on here have run non-stock variators, and the Dr. Pulley sliders are popular. Short opinion: the improvement with an actual performance variator makes any slider/roller changes to the stock variator seem meaningless. IF you value highway riding/cruising a performance variator is a compromise. I typically see 5,500 rpm at 70 - 75mph, fuel economy is around 42 - 46 mpg if pure highway use. I do a lot of around town riding and off-line starts, I would almost consider the stock variator a liability, it feels that slow in comparison.

Hence, upon acceleration I spend very little time below 5,000 rpm. When I'm accelerating my revs go to about 6,000 rpm. If I accelerate off the line I rev up to 6 grand. If I'm cruising at 25mph and get on it I go up to 6 grand. Hence, for me, there is no such real thing as low end. This is one of the most tricky things regarding our cvt's. On any other bike with a manual transmission it's easy to distinguish between low, mid, and upper range powerband characteristics. On our bikes, not so. The variator setup can obscure what's going on in the engine.

My simple answer to you is that I felt the power increase was overall. I did not feel any impediment to the low end.

I will add two things, here. I have been considering getting an FZ-07. Hordpower has done dyno development of that bike, and he checked various intake setups. Long runners gave the best low end but choked high end, shorter runners gave minimally less low end while giving increases throughout and up into the high end. Point being that intake changes, in my experience, have never taken away from the bottom end. If the bike has a bottleneck in the intake opening it up will be noticeable, as it was in the case of my DR650 and also in the case of our Tmaxes.

The second thing I will add is that there is an area that will indeed impede and take away from the low end: a big ass, free flowing exhaust. Skutorr talked about this when he got a Yoshimura exhaust and lost acceleration, he ended up with a Mivv and it worked better than stock. I will concur that a free-flowing exhaust will take away from the midrange. I've experienced it on our Tmaxes, and I also experienced it on my DR650. With my DR I even had the 790 kit, and even with that extra displacement going to the FMF Powerbomb header I experienced a loss in low end compared to the stock header. Whoever the head honcho is at Procycle disagreed on the forums, saying there was no loss and only gains, but MXRob showed dyno charts that confirmed what I felt: a loss of snap going to the bigger header. Everybody thinks going bigger and removing "restrictions" is guaranteed, it's not. Some combinations are magic when you get them, and then you want to go further and you lose the magic. I've done it many a time. Hence, the reason why the airbox mod is so good: if it doesn't work for your setup just tape it back up.

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