MXA PRODUCT TEST: Pro Circuit RM-Z250 T-4 GP System

January 15, 2009
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INSIDE THE PRO CIRCUIT T-4 GP RM-Z250 PIPE

WHAT IS IT? The Suzuki RM-Z250 (2007, 2008 and 2009) has a potent low-to-mid powerband. The Pro Circuit T-4 GP pipe makes it more of a mid-and-up engine.

WHAT’S IT COST? $749.95 T-4 (stainless), $899.95 Ti-4 (titanium)?(951) 738-8050.

WHAT’S IT DO? Team Suzuki rider Ryan Dungey runs a Pro Circuit pipe on his works Suzuki RM-Z250. When a factory team chooses to use off-the-shelf pipes from an aftermarket supplier, that is a strong endorsement?strong enough for the MXA wrecking crew to order a Pro Circuit T-4 GP system for our 2008 Suzuki RM-Z250.

WHAT STANDS OUT? Here’s a list of things that stand out with Pro Circuit’s Suzuki RM-Z250 Ti-4 GP System.

ÿÿ (1) Performance. No other 250 four-stroke is as good off the bottom as the RM-Z250. The RM-Z250 bursts out of corners and pulls hard through the midrange. If the RM-Z250 has a flaw, it is that the engine hangs and flattens out from 10,000 to 12,000 rpm. It revs, but it doesn’t pull. Thankfully, the Pro Circuit T-4 GP system provides top-end in spades. This pipe makes the RM-Z250 a gear better in every situation. Corners that you were straining in second to get to can be rocketed into in third gear with the T-4 GP pipe. It adds a healthy dose of top end and doesn’t hurt the bottom-to-mid one iota.

ÿÿ (2) Horsepower. From the very bottom to 7200 rpm, the Pro Circuit pipe and stock pipe are in a dead heat. From 7200 rpm on up to the 13,200 rpm rev limiter, the Pro Circuit pipe is one horsepower better. The peak power on the stocker is 35.9 horsepower, while peak on the Pro Circuit pipe is 36.9 ponies.

ÿÿ (3) Torque. Pro Circuit’s torque curve is a match for its horsepower curve. Starting at 7200 rpm, the Pro Circuit pipe makes and keeps a one-half foot-pound advantage over the stocker.

ÿÿ (4) Over-rev. The biggest weakness of the stock exhaust system is that it goes flat on the upper fringes of the rpm curve. In fact, there is a serious dip in the stock curve at 12,000 rpm (where horsepower drops off significantly). With the Pro Circuit pipe, the dip was erased and the top-end over-rev was significantly improved.

ÿÿ (5) Fit. Pro Circuit uses the same style head pipe flange as Suzuki, but adds two springs for more security. We didn’t like the springs (since Suzuki didn’t need them). The rest of the pipe needs a little muscle to squeeze through the RM-Z’s Delta Box chassis.

ÿÿ (6) Prices. Pro Circuit offers four versions of the RM-Z250 exhaust system. The titanium Ti-4 full system (head pipe and muffler) costs $899. The stainless steel T-4 full system retails for $749. The Ti-4 and T-4 have the exact same dimensions and performance; the extra $150 is for the lighter weight of the titanium. Additionally, the slip-on systems (without the head pipe) are available in both Ti ($525) and stainless ($425).

ÿÿ (7) Place of Manufacture. Pro Circuit’s Ti-4 exhaust is manufactured in Corona, California.

WHAT’S THE SQUAWK? Apart from leaning out the fuel screw, we had no squawks. Given our druthers, we opt to run the stainless steel system instead of the titanium system. Why? They run the same, feel the same and we think that the stainless version is more durable. Not to mention much cheaper.

This is a five-star pipe because the RM-Z250 is a bike that needs more power from the middle on up. For Pro Circuit, who makes the pipes that Ryan Dungey uses on his works RM-Z250, making more RM-Z power was like shooting fish in a barrel.

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