May: Clutch Comparison & Evaluation

We currently stock four different brands of drive clutches for the Briggs kart classes. Let’s take a moment to discuss the different clutches that CRE currently offers.

First, there’s the old reliable Noram/Ratech shoe & drum design clutch. This clutch is almost indestructible, and perfect for “low-buck” or beginner karters and backyard enthusiasts. Because the clutch is very affordable, at around $60 complete with different spring sets, it has gained a lot of popularity. At One time this was the preferred racing clutch, believe it or not. Oh, for the simpler days. With the low price, however, comes few bells and whistles. The Noram does have a few features, which include: adjustable rpm engagement, and snap ring drum/gear replacement. This is the simplest design clutch on the market and because of its lack of number of precision parts, it makes the Noram clutch the clutch of choice for yard karters wanting to step-up from the El-Cheapo brand that came OEM on their backyard burner.

The next step up might be the Stinger clutch by Avenger. This is now the only clutch allowed for WKA racing in the stock Animal classes. WKA has felt that clutch technology, and the price that it brings with it, were making too much of an impact on entry level karters wanting to race at the national events. With a clutch claim, and a fairly inexpensive clutch option for those that choose the new stock overhead valve engine classes, hopefully entry level karters will attend more national points events, and stimulate the growth of this new overhead valve engine class. Unfortunately or fortunately, however you wish to view it, most local tracks have not adopted the clutch claim rule, and allow any clutch on the market to be used, blueprinted, or otherwise. We continue to stock and retail the Stinger clutch for around $125 simply for WKA racers wanting this particular clutch for their Animal engine application.

Clutch number three is the most popular clutch in sales in the karting industry. It is the Greased Lightning by Horstman. This multi-disc clutch was unveiled just a few short years ago to replace the aging MDC clutches that Horstman offered. It was also a credible response to a growing number of smaller companies jumping into the clutch manufacturing arena. Horstman has always had the business sense to build a product and mass distribute it through it distribution network, so that availability and replacement parts are on the shelf at a kart shop and race track near you. That is the one thing that the “one-off” smaller manufacturers struggle with to be competitive in the ever growing karting market. The Greased Lightning’s availability of parts nationwide make it an easy seller to the entry level or local racer. The “GL’s” disc performance is far superior to the formentioned brands, but only costs moderately more. Retailing at a new lower price of around $185, the “GL” clutch has literally taken over the clutch scene. The Greased Lightning also is attractive to the kart racers because they could take their existing MDC clutch and "convert" it for much less than buying a whole new clutch. Since the GL clutch uses the same drive hub and floater disc, the only parts needed were friction discs, a couple wafer bearings and the basket drum itself.

While the Horstman Greased Lightning clutch is a great clutch for the average racer, it fell somewhat short of the expectations of the serious and pro racers. Some drawbacks of the “GL” are it’s relatively fragile aluminum basket design and snap ring placement for changing gears. Another problem that wasn’t addressed was the old MDC pressure plate and backing plates warping due to excessive heat. These parts are stamped out of thin steel, and are placed under tremendous load and heat stress during usage of the clutch. This results in damage of the clutch which can include warpage of the plates which can be expensive to have rebuilt. And while the racers were excited about the hard hitting engagement of the “GL” clutch over it’s competitors and predecessors, there was still room for improvement.

Clutch number four: The Bully by Kermit Buller. Nebraska’s Kermit Buller has been a mainstay in karting for a number of years. Kermit has a knack for perfecting products to his level of expertise. Hence, the Bully clutch. The Bully utilizes a machined pressure plate and weight levers, making them considerable more accurate and durable than a stamping process. The Bully also comes with matched spring and is pre-set-up for your clutch stall recommendation from the factory or is customizable. Each clutch is meticulously assembled before it leaves their shop. Essentially, it is blueprinted right out of the box. Kermit addressed the weakness of other brands of clutches available on the market and superceded everyone’s dreams of how a clutch should set you back in the seat. Price wise, the Bully will definitely set you back though as well. Performance doesn’t come cheap, as these clutches retail in the $295 range. The Bully is not only a very high performance minded clutch, but also extremely durable. Many of our weekend warrior racers prefer the Bully clutch due to its durability and dependability. Low maintenance is by design, as the discs and pressure plates rarely need attention. Simply blowing them clean with a compressed air hose will suffice for most local racers. Between races, the clutch can be cleaned rather easily with a can of brake clean, and does not necessitate a complete teardown and deglazing each and every race day. Although proper maintenance should never be dismissed, we have had customers run their Bully clutches an entire season without touching them! No discs replaced, no springs, weight lever pins, etc, replaced in 20+ races during the season. That is worth some money in the purchasing decision alone.

Now for the newest clutch in our growing inventory. In response to the demands of the serious (high-end) racer, Horstman has unveiled it’s all new Reaper clutch. The Reaper uses much of the same design aspects of the original MDC clutches, but that’s about as far as the comparison dares go. The all new Reaper clutch features a smaller basket design for lower rotating mass and quicker acceleration. The weak links of the Greased Lightning clutches have all been covered. The plates are now machined out of heavier billet stock, with the addition of cooling fins to aid in heat dissipation. The weak snap ring groove of the “GL” clutch has been replaced with a square lug, (bolted in), drive gear. The basket wearing problem has been eliminated with the addition of replaceable wear pads - which will become an option on GL clutches now as well. Even the weight levers are machined. No stone was left unturned. While the clutch is cnc machined from heavier and more durable materials, in reality, it weighs about the same as other competitive clutches. With the reduction of diameter of the clutch, and all its internal moving parts, the rotating mass is considerably less! This clutch is very easy to work on from the average local racer to even the most experienced professional. It adapts very well to higher horsepower classes as well. It performs tremendously on a limited modified or stock Briggs Animal class engine. And the good news continues…price-wise, the new Horstman Reaper is right in line with its competitors retailing at around $245. Horstman has indeed done their homework, and brought a very strong competitor to the track. The Reaper is destined to revolutionize the clutch industry once again.

Brian goes indoors

Horstman Reaper evaluation: For some indoor racing I got the chance to do some clutch testing and comparisons. Since we stock most of the Horstman line of products already, it was only sensible to really put their new Reaper clutch to the test. We were fortunate enough to have a weekend that we could actually go and “play” with some karts for a change. Our summer schedule is normally so hectic, that it simply doesn’t allow us much time to prepare a kart for racing competitively anymore. While Brian has plenty of opportunities to drive other’s karts, nothing quite compares to being able to put together a kart of your own and putting it through its paces. It seems like every time we get a kart built for Brian to race indoors, someone comes knocking on the door looking for a kart…and you know how this story goes…Everything in our shop is for sale if the price is right. Yep, the customer is now the proud owner of a kart race-ready, and we are here at the shop working all weekend long trying to keep up with demand. (Not that I’m complaining, mind you.) We decided to take in a few indoor races this year and needed to put together something fast and fun. Brian decided to take out an older open engine that had been lying in the back. Of course it had to be on one of our own Vector chassis. We decided to also take a used kart that had been sitting here in the shop all summer with not even a nibble as far as sales are concerned. We built that one up as a stocker and started with the new Reaper clutch on that kart. We were fortunate to be able to run from about 7am to 10am as a practice session, which was perfect for dialing the kart in and really testing the clutch. The clutch was installed and run just as we received it from Gary at Horstman. Right out of the box it hooked up hard. Usually a new clutch needs to be broke in a little to seat the discs, but the Reaper came on hard right from the beginning. For a few hot lap sessions we went kinda easy on it, doing our normal clutch break-in routine. Brian always likes to heat cycle the clutch a few times and wear the discs in a little to gain a little better knowledge of how the clutch will perform under race conditions. After the clutch was run a couple hot lap sessions, the spring heights were rechecked and air gap was referenced. Brian decided that the clutch needed to stall (or lock-up) a little later (higher rpm). Each spring adjuster screw was turned in ¼ of a turn and spring heights were remeasured and all made exactly the same height. The clutch had originally been coming in at 3800-3850, but with the cam and pipe combination on the engine we were testing on, a higher engagement of 4000 was required. The ¼ turn adjustment was just the ticket. The clutch was tested a few more hot lap sessions, each time checking clutch stall speed, and it was very consistent. This was terrific news, as a clutch that repeats its performance time after time is exactly what the racer needs. Brian has been a strong supporter of Kermit Buller’s Bully clutch over the past few years, and was more than a little hesitant to try yet another new clutch that has came on the market, let alone start stocking it and all the related parts to accompany it. “Kermit has always built a very nice clutch, but this new Reaper clutch from Horstman has raised the bar yet another notch,” Brian said. The nice thing about dealing with a huge company like Horstman, is that their presence is everywhere. Every kart shop in the country stocks Horstman parts, even if they don’t stock their complete line, they have access to the parts you need. “Brian was very impressed with the performance of the Reaper. Brian will scrutinize every product that we stock to make sure that it lives up to his stringent expectations. If Brian is impressed with something after a hands on “seat of the pants’ trial, that’s good enough for me. Horstman’s new Reaper clutch is a welcomed addition to our stocking inventory ,” Sarah Carlson noted. “This gives our customer yet another great option to choose from,” Carlson continued.

Customer follow-up

Recently, a customer emailed asking why he should invest in a new Horstman Reaper clutch - and here was Brian's response verbatim.

"Personally I really like the Reaper clutch.
For the price difference between it and the Greased Lightning, it's a no brainer!

The Reaper hits harder even over a "good" Blueprinted GL clutch.
The Reaper is smaller in OD, so reciprocating mass (weight) is less.
Reaper is built MUCH tougher, so it will withstand abuse much better (not that we abuse race parts or anything!)
Reaper has matched springs (you pay an additional $24 for that on a GL blueprint).
The springs and internal parts are cryogenically treated to help them last longer and be more consistent.(Not that I am a big believer in cryogenics, but at least it shows an effort on Horstman's part to give us a better part.)
Everything is CNC machined, not stamped on a press like previous parts.
The pressure plate and backing plate are both thicker and vented to help keep the clutch cooler.
The basket has replaceable steel inserts (BIG PLUS) where the friction disc typically wore into the GL baskets. (This saves weight over replacing the aluminum drum with an all steel one.)
They are easier to work on and maintain.
The gear bolts in with a four bolt - four lug square design that doesn't come loose like the thin snap ring and breakable snap ring land on the GLs.
The friction discs have more "meat" on them, so they will wear longer.
That's just off the top of my head - I'm sure if you visit the Horstman website - they can brag about more. :)

Bottom line, Horstman did their homework before releasing this clutch. I think the GL clutch will be a memory as far as the racers are concerned now. Kinda like the MDC clutches became. They're simply too close in price. Horstman originally wanted to sell the Reaper clutch for $275 neighborhood to be competitive with the Bully clutches. That's who all the serious racers were getting their clutches from last year. Hopefully Horstman will regain some of that lost marketplace with their new Reaper clutch.
I honestly like the Bully clutch very much. I really appreciate all the work and attention to detail that Kermit puts into his clutches. And they hit hard too. Problem is, they're too small of an operation to keep up with the huge demand they saw last year. I like his clutches, I like the people, but you can never get orders from them. That's the bad part about running their clutches - you better have enough spares to get you through the year, cuz noone else will have them either.
On the other hand, every kart shop in the country is a Horstman dealer. Parts availability has never been a problem there, and won't be when you need a part for your clutch at the racetrack. For us, it was a pretty clear business decision as to which clutch to actively promote. We stock and sell both, but the Horstman will outsell the Bully 10-1 is my guess at this point.
You will LOVE this clutch. I ran it indoors over the winter, and found it very consistent, whether hot or cold - and that' s the real test for a clutch I think. If you can get a clutch to come in a 4000 on a restart after running 10 green flag laps, you can't ask for anything better. I've found the rpm chart provided in the package is a little on the low side. You might run 1 or two less washers than what they recommend - depending on how you like your clutch to come in. Follow their maintenance and you can't go wrong. Call or email if you have ANY questions after you get this clutch in your hands - or when you get out on the track. We'd be more than happy to help you.
Thanks again, and please do take a look at our website at your leisure.
Keep us in mind for all your karting needs.



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