Taming Suzuki’s TM400

tm400_flywheel_051Came across this 1972 test in a DIRT BIKE magazine to tame the 71 – 72 TM400 Cyclone motors, I have heard of other solutions using the TS400 ignition systems but I have not found any written tests on that yet. Not sure if the 74 model needed the same treatment as the 75 TM400 was said to be ok but by then the RM series were out and that was the end of the TM’s.

A BOLT-ON SOLUTION for TM400 sweaty palms?

Some people have this healthy fear of snakes. Others cringe inwardly when they find themselves alone in a dark room. Yet others can’t stand being up high, or even worse-flying in an airplane. All of these fears pale by comparison to the fear-inducing potential of a stock 400 Suzuki MXer. This is one of the truly Frightening Machines Of All Time.

What makes it increase your pueker power? Part of the problem lies with the frame. another part with the suspension—but the bulk of the guilt lies with the power band of the engine.

There is no such thing as “just a little more” from the twist grip on the TM 400. Nosirree. You either get a giant handful or the engine stalls. This phenomenon is, of course. caused by the lack of flywheel weight. A logical cure, then, would be to bolt on some weight to slow the rev buildup down to a more usable level. Remember, power that does not get to the ground is wasted power. And slower building revs mean that the bike will be easier to ride. At least in theory.

And that’s why DIRT BIKE decided to test S0me of the bolt-on flywheels currently on the market. Woodland Hills SportCycle supplied the bikes and the equipment for our controlled testing. Along with our intended test of the 400, a flywheel was also bolted on the 250 MX. Even though this model doesn`t have the jolly gruesome of the larger machine, Woodland Hills SportCycle claimed that it makes the 250 into an easy to-ride trailbike.

The bikes were ridden in standard trim first, to get the feel of the stockers. If you read the test in the October “72 DIRT BIKE, you’ll remember that we were favorably impressed with the power band of the 250, so we really couldn’t see why SportCycle offered heavier wheels for this bike. Their reasoning was that some people might want to take the 250 trail riding or something of that nature. They claimed that the addition ol their flywheels would allow the rider to bog the engine down to very low r’s. Would we test the 250 also? Sure. Why not?

Our other machine was a brand-new, totally stock 400 Cyclone MX. For this machine, we had two separate flywheels to try. A 2-pounder and a 4·pounder. We chose the heavier item.

Off to the trails went the DIRT BIKE Wrecking Crew, with two Suzukis in tow. Both, as previously stated, were first ridden stock. The 250 was as we remembered it—decent power and very rideable. It could be ridden at very low revs for a racing machine low gear would let the machine move forward at a walking pace with the clutch out, just above idle. Any slower than this and it was necessary to slip the clutch to keep the engine from stalling.

A 2-pound flywheel was then bolted on the 250 (after a trip back to the shop). The 250 will not accept the 4-pounder—2 is the maximum.

An immediate difference was felt in the engine performance characteristics. Not all of it desirable. While the engine would lug down lower and smoother, engine response was sluggish. Not only did it take too long for the revs to build, but it also took a great deal of time for the engine to return to idle when the throttle was shut off. Much like a trials machine.

One additional factor made itself felt: The rear brake was less effective and had difficulty slowing the bike down. This will always be the case where heavy flywheels are working against brake shoe efficiency. In the case of the 250 Suzuki, however, it never had a giant reserve of brakes for starters, so this cannot come under the category of a Good Thing. No way. A rider who installs a heavier flywheel on the 250 will find his lap times on the motocross course getting slower. For trail riding? Even though we feel it makes the engine more tractable, the undesirable side effect on the rear brake makes us hesitate to recommend its use on the 250. Unless the rider modifies the rear brake to be more efficient.

Our attention turned to the 400. First a ride on the bike in standard trim. Culp. The merest tweak on the throttle produced a spinning rear wheel. Or if there was a modicum of traction available, the front end would leap for the nearest cloud. If contact was made with a series of harsh bumps, the machine would slither and hop sideways in an instant. Coming out of a corner under heavy power was a true adventure, indeed.

Back to the shop and zip-bam-boom—there we were with a heavy wheel bolted on. This one a 4 pounder. Back to the riding area, and a pleasant surprise. That 4—pound slab of steel did astounding things for the 400 racer. No kidding. Without taking a single iota away from the top end of the Cyclone, it made the power band almost pleasant. Additionally, much of thc tendency for the rear wheel to lock up under braking was eliminated. Unlike the 250, the 400 had an overly sensitive rear brake.

This is the best thing, the single best thing a rider could possibly do to a stock 400 Suzuki. In Fact, there really ought to he a law requiring the installation of the 4-pound wheel before the bike can be sold.

Much of the sideways hop disappears and the machine is infinitely more tractable. The bad handling is still there, but even this is helped considerably because of the more predictable throttle reaction. One can almost trail ride the bike—but not quite. We would recommend that the rider go for the 4-pound flywheel rather than the 2 on the 400.

Woodland Hills SportCycle offers these wheels either mail order or at their high-rolling shop. The address is 22726 Ventura Boulevard, Woodland Hills, California 9136-1. Phone number (213) 340-2191. Tab for the items is $19.95 For the 2-pound wheels and $23.95 for the 4-pounders. They pop for the postage if prepaid and you get burned For the tab on COD stuff. If you stop by the shop, they’ll install the wheel For Free. Providing, of course, you bought it there. Don’t expect much more than a nice smile if you bought yours in Wilmington, Delaware. Oh yes. They have all manner of trick items for the Suzuki line of dirt hikes and will send you a free brochure if you want to gamble a stamp. It’s your stamp.


22 Responses to Taming Suzuki’s TM400

  • Hamish says:

    Come across a TS 400 and a PE 250.Which of the two would be an ideal resto project.Should I grab both?

    Would appreciate your feed back.

  • Rich Freeman says:

    Bought a new, off the showroom floor, TM400 just exactly like the one in the flyer…Best bike I ever had but some jerk stole it…Great balance vs. power band…Could ride a comfortable wheely all the way through the gears…I would love to find another one to buy…Any suggestions as to where I might find one for sale???


    • Admin says:

      Not sure where you are located, these bikes dont come up often but a good place could be vmx club websites, even try a wanted ad on them which should be free to place. You will also see one on ebay every now and again but unless you monitorng it, you wont know.

  • Mopeds says:

    Recently I discovered this blog and have been following along steadily. I thought I might write my opening comment. Im not sure what to say except that I have really loved perusing. Nice blog. I will keep coming back to this blog very often. I have also taken the feed to get any updates.

  • richard says:

    The real problem with the TM 400 are two mostly. The swingarm, which is made of cooked pasta and the ignition, advancing too quickly. Replace the swingarm with either an aluminum one or a chromoly one. You can buy the swingarm either off ebay in either chromoly or aluminum. As for the ignition you can use ponts off of the TS 400 set at the recommended stock setting for the TM 400. You can have the crank end turned down to use a PVL pick-up and rotor. Another option for the ignition is to use the stock rotor and mount a PVL pick-up set at the stock ignitiontiming. Change the rear shocks as they are made of cheap junk and bend rather easily even if you change the swingarm. Get rid of the oil injection system and mix it using 32:1 belray, hondalube, etc. synthetic stuff. Doing this I promise you will smoke most bikes out there.

  • Joe says:

    I just reconnected the oil lines onthe TS 400 we just bought for the son- in- law, after reading rumors that the rod and mains need this system to stay lubed over the long haul. Am I wrong?

    • Anthony says:

      your exactly right, you never want to unhook the oil injection system on the TS or TM series, doing so will cause premataure engine failure.

      • ZOOM says:

        Gee Anthony I removed my automatic oil system on my Suzuki TM400 in 1971 when I bought it new and it still runs great. I hope I didn’t cause the motor to wear out too soon as I ride it every Sunday and have done so since 1971 give or take a couple of Sundays. It has been running great for 41 years with a mix of castor oil and 108 octane at 20:1. One of the main problems that blew the engines on my friends bikes was the auto oiler getting plugged. I mix my own fuel so that I know it is right and am still running on the original piston and rings. My Cyclone still clocks at 0-60 in less then 5 seconds and uses one gallon of fuel for every two miles. It smokes a little but the new 250’s leave me alone after seeing my bike run. The suspension isn’t great but once you have sat on a Cyclone at full acceleration you realize that it is the greatest feeling that money can buy. There are no words to describe the feeling of instant unlimited power. You stare death in the face each and every ride. I am not kidding. I have several new dirt bikes and nothing compares with the feeling that the Cyclone gives me.

        • David Burns says:

          Hey Zoom, My name is David, but my friends call me Haji. I started riding motocross back in 73, and now at the ripe old age of 52 I want to get into vintage MX…That said i rerally want an RN72, who doesn’t right? I would however probably find a TM400 and do what I can to trick it out. You know drop about 10-15 pounds, move the rear shocks (both of them) forward, stiffen up the front forks (maybe even put a set of Maico forks on), then even perhaps a new swing arm. That all said, I will still have a Cyclone power plant. We have all heard the stories of lining up at the start and seeing all riders quickly shift their starting position to be far clear of any Cyclone. The power band, not the power is a problems, for Christ sake it only makes 40hp, that is about what a 2005 CR125 makes. It’s allin how the power hits. So my question to you is, how do you make that on/off switch in your right hand work? Have you done a flywheel kit, changed the porting….what works. You obviously love your Cyclone, as you should. I want one, but I need info from guys that have experience with that bike…anyway keep her running well and have a good ride this Sunday….Haji

      • zooker says:

        The 400’s injection system could be unhooked without causing any harm to the engine. All the rest of the TM line had main bearing(s) which were directly oiled by the injector pump, received no oiling from pre-mix. I knew several racers who minimized the injection systems output and then ran pre-mix, but this meant still having the injector hooked up. On my TM250, a hole was drilled in the cases to allow pre-mix to reach both bearings ( if I am remembering it right, only one bearing was isolated ) and the injector was removed entirely. It’s been a long time, can’t remember exact location anymore, but a google search turned up a few threads with instructions, don’t know if this will work on the 125/100.

  • Kirk C, says:

    Ive got a 74 elsinore, really cool bike , fun to ride,
    I like to have a TM 400 too,
    i dont nthink it handles that bad,
    and i think It’d go uphills reaally good without having to downshift alot,
    Ill use the autolube on mine too,
    alot simpler than premix and if you get stranded,
    you just go to a pump at a gas station,
    and then ride it home, or whatever,
    Really cool idea,
    alot better than an RM too as lower to the ground,
    and simpler to work on,

  • Glen says:

    have a complete yellow TM 400 mX (not street registerable) maybe for sale/restoration. have owned since 1980. was always a bitch to start, but did some of the best mono’s ever on it even having owned several Yamaha TT500 and XT 500’s and a TTR 600.

    In shed hasn’t been started for over 10 years. will take a picture if interested

  • Kirk C, says:

    I like Honda elsinore 250 M s
    and TM 400s in 74, or 75
    they got everything worked out by then and it was nice to ride,

  • Kirk C, says:

    Ive got an 85 Honda CR 250,
    The bike is too tall for me in the seat,
    I like the lower 70 bikes
    easier to get on,
    I was gonna get a 74 Elsinore 250,
    but i like the TM 400 alot better,
    more bike, and alot more stable due to it’s weight,
    Im redoing a 76 RM 250,
    but i need a few parts for it,

  • Doug says:

    Anyone have a 1971 TM400 airbox/boot? Front fender or Petty fender or like in orange.

  • wayward wayne says:

    just picked up a 74 cyclone 400 today. 150 bucks. getting it ready for flat track racing tomorrow. I truly hope it doesnt put me in the wall or jump out from under me. should be interesting. Perhaps i can find a 4 pound weight around. Thanks for the great info!

  • Tom Williams says:

    I flattrack raced 1972, 73 and 74 TM400s back in the early to late 70s and won a Colorado State championship on one in 1974. I also had several hillclimb (like Pikes Peak, not traditional hillclimb) records on one. The 1972 and 1973 state championship and Pikes Peak Hillclimb in 72, 73, 74 and 75 were won by friends of mine on TM400s. This was the good old days when you had 200 riders at every race and had to race 3 times a week to even be close in the points! Now, either Colorado riders are of a much heartier breed than the rest, OR, we figured something out about these bikes to make them work. Trust me, if you want to win on one, don’t add a 4-pound weight to any part of that bike! Just mill the head 10 thousandths to raise the compression a bit, maybe run a Wiseco piston, add a 36mm Mikuni carb, a good pipe, and gear it to run above the 5K or so rpm point where the timing jumps to full advance, and they are great rides. Oh, and if you remove the autolube, also take the engine apart and remove the oil fling ring on the crank…that will keep them from siezing main bearings when you remove the oil lines! AND…if anyone knows of a good clean 74 for sale, please let me know!!

  • Michael R says:

    I am 17 and have just bought and is on it’s way to my place a 1971 tm400 I will be restoring it stock bar different shocks and racing pre75 on it can’t wait to ride it thanks Michael.

  • Frank Parker says:

    Where can I buy the heavier flywheel and igntion parts to tame my 1972 TM400? Please reply to my e-mail, parkerf@deminglaw.com. Thanks, Frank

  • OlderMX7 says:

    going to get a 75 Suzuki TM 400 with aftermarket pipe like a circle F.
    last and best of the TM’s, thought about an RM 400
    but bike is too tall for me.
    back road’s,and vintage Race’s.

  • dmb says:

    i’m 62 saw the first orange tm 400 at the desert races in so.cal i remember people saying no one said they were down on power.

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