Yamaha It175g
IT175G
CYCLE WORLD TEST
Serious enduro competitors have been building their own mounts for years. By adding lights, spark arrester, speedo and tool kit to a motocrosser the super serious come up with a bike that handles bet-
ter and is lighter than most stock enduro bikes. Some European companies have been offering similar bikes to the public the last couple years, now Yamaha has done the same with the IT175G.
The newest 175IT is based on the YZ125 motocrosser, starting with the same 'chrome-moly frame plus a rear frame loop. The rest of the frame is identical. A single front downtube starts at the heavily gusseted 28.5° steering head, splits into two smaller tubes under the engine, ending at the lower rear of the engine. A large backbone tube drops sharply to a point just above the carburetor where four lesser tubes begin: Two drop down, ending below the swing arm pivot, the others go straight back to form the seat rails and rear loop. Two more pipes tie the seat rails to the main frame, forming a triangle for the mid-section. Like the YZ motocrosser, the IT has a swing arm made from square aluminum stock. It is a well braced unit that pivots in needle bearings and has good plastic chain rub blocks attached.
Because the frame is based on the YZ motocrosser, the rear suspension follows the same pattern. The shock is made from aluminum, turned around and rear-set. An aluminum reservoir is mounted on the front downtube and damping and spring preload are easily adjusted. Adjusting spring preload requires the use of a large tool that Yamaha supplies with the bike. Damping is adjusted by turning a thumb knob just behind the spring preload nuts. Both adjustments are placed just above and in front of the rear wheel. Wheel travel has been reduced to put the ground within reach. Rear wheel movement is 9.8 in. compared to 11.4 in. for the YZ. The forks are also much like the YZ125G. They are leading axle jobs with good engagement, 9.8 in. of travel, air caps, accordion fork boots, and triple clamps with double bolts. The top clamp has rear-set handle bar pedestals so the long 36mm fork stanchion tubes can be adjusted up and down for steering quickness.
A Great Enduro Bike For Work or Play
The extra small-cased engine looks like the 125 and much of it is. Much is also different. Let’s start with the parts that are the same: The rod and crank assembly, the center and side covers, sprocket cover, clutch plates and springs, crank and transmission bearings, kick start lever, and reed cage assembly. The cylinder is different, containing an increased bore size of 66mm compared to 56mm for the 125. The increased bore is all that makes a 125 into a 175cc. But there is more to the transaction. The 175 ignition uses an outside flywheel CDI made by Mitsubishi, the 125 has an internal Hitachi flywheel. Strangely, the 175 has more timing advance than the 125, the 175 being set at 2.6mm BTDC, the 125 at 2.27 BTDC. Both sizes have six-speed transmissions but the internal gear rations are spread wider for the IT175. All internal gear ratios are changed except third. And the final gear ratio for it is different due to variation in final drive ratios (48:12 YZ, 44:12 IT), and primary drive gearing (62:18 YZ, 52:17 IT). This juggling of ratios means the IT ends up with a slightly lower low and much taller sixth. The difference in final gearing is substantial. Final gearing ratio for the YZ in sixth gear is 13.60, almost the same figure the IT makes (13.36) in fourth. Add fifth and sixth on the IT and top speed jumps dramatically. Both bikes use a hefty 520 final drive chain and combined with the rearset countershaft sprocket, ends most chain problems associated with smaller bike of years past. Both the 125 YZ and 175 IT use a 32 mm Mikuni carburetor but they are far from being the same. The IT has a different model carburetor that contains a power jet.
Great, what’s a power jet?
A power jet is a small jet, in this case the same design jet used for the pilot or starter jet, but placed at the top rear of the carburetor. A hose from the float bowl supplies fuel to the jet which feeds a rod that’s positioned in the center of the air intake bell. The vacuum from air rushing past the hollow rod sucks fuel and supplements the main jet. The system works mainly from half throttle up so the needle and main jet can be leaned out, giving better low and mid-range response. The power jet then adds gas at the top of the range so the engine doesn’t seize. It also adds another tuning dimension.
Both wheel assemblies are identical to the YZ. The front is a 21 in., the rear an 18 in. Both have aluminum rims laced to conical hubs by medium sized spokes. The rear is a new unit that has the drive sprocket and brake on the same side. Enduro features amounf to axles with pull bars, snail adjusters and a quick disconnect brake rod.
Other changes have been made to the basic YZ motorcrosser to make it right for enduro use. An aluminum skid plate wraps around the underside of the engine, the rear fender is longer and wider, the plastic gas tank holds 2.9 gal. of premix, the seat is wider, there’s enduro lighting combined with a front number plate and a rear fender mounted tool bag is standard. A speedo with a square shape, like the other ITs use, makes the feds happy by stopping at 80 mph, not really a problem on the little IT but annoying to us anyway. A large plastic knob is mounted on the left side of the unit and makes resetting or adjusting easy with gloves on. The unit can be reset to zero quickly and easily by turning the knob backward or adjusted forward or back by tenths by pulling the knob out first.
The high mounted pipe and spark arrester/silencer are also designed for the IT. The pipe tucks nicely under the gas tank and the silencer is mounted in double brackets, ensuring it will stay on the bike during the most severe conditions. When the exhaust noise starts rising, the inside core can be removed and repacked, a nice feature that is needed on motocrossers as well.
The IT airbox looks like the one on the YZ and it is very similar. The biggest difference is that the IT box only draws air from one side of the box, not both sides like the YZ. The general size and shape are the same ... meaning it also has the same limited space inside when trying to clean the dual stage foam filter. The cone shaped filter just barely fits into the box, and one is never sure the front edge is completely sealed. Liberal use of grease on the sealing edge is recommended and required. The filter is held in place by a round plastic knob that has four small ridges the installer is supposed to use to turn the nut... not an easy job when your hand is smeared with filter oil. The air inlet is well protected from water splash and the opening is high on the bike under the seat. Even with the air box modified (see section about filter box and silencer modification) which effectively lowers the air intake level, the bike will ford deep creek crossings without drowning out.
The excellent brakes on the IT are affected slightly by water crossings, losing a little power at both wheels, but drying quickly after a couple of stabs. When dry, the brakes are predictable, progressive, strong, and confidence inspiring. Although the rear isn’t a full-floating design—Yamaha opted for the quick slide out feature instead—we didn’t notice chatter from suspension lock up on rough downhills.
The handling that makes the YZ125G great also makes the IT 175 great. The light weight of the IT, (only 12 lb. more than the YZ’s 202 lb. with a half tank of gas) makes the bike a dream to throw around on mountain paths and if the rider screws up and misses a turn and has to carry the bike up a side slope to get back to the trail, it won’t be nearly as hard to pack as a 300 lb. bike.
The motocross frame and shortened suspension components provide the rider with the best steering enduro motorcycle ever. No one can ride the 175 IT fast enough on enduro terrain to flex the swing arm, frame or forks. Although the forks are only 36mm in diameter, the size is more than adequate for the light weight of the IT. And reducing the travel on the YZ forks was accomplished by increasing the stanchion tube/lower leg engagement, meaning strength and steering precision were enhanced at the same time. The wide seat has a respectable height for a modern enduro mount. All but the shortest riders will be able to touch the ground and paddie when necessary. Ground clearance might be a slight problem if your riding area is strewn with fallen logs and such, but we only experienced skid plate dragging a couple of times.
Blitzing down converted hiking trails in the mountains and winding trails in the desert is great fun on the little IT. Riding it like a motocrosser works best; go deep into the corner, brake with both brakes, pitch the bike into the berm or a downed tree, hit the clutch with the throttle opened fully. The bike responds by exploding out of the turn. It’s really fun and could easily be called a Mountain Motocrosser. Power delivery is somewhat pipey for an enduro bike, probably one of the reasons the bike works well when ridden like a motocrosser. Gear ratios are well chosen for the engine output and we didn’t notice any bogs or jumps in the ratios. Shifting is crisp and positive, no catches or hang-ups, and rider feel is perfect. The steepest hills can be climbed in low and sixth offers good top speed.
We took the bike to the mountains several times and to the desert once. It is a super fun bike to ride. The first time we went to the mountains the tester, an open bike freak, whined about having to ride a little 175 all day. After a couple of hours, he was going faster than he normally goes on an open bike. Once on to the hit-the-> clutch-in-the-corner riding style he began to enjoy the light and nimble 175. Balance is perfect on the IT; it doesn’t try to loop or nose dive, preferring to give neutral feedback. The rider never has to compensate for handling deficiencies as there are none. We used the bike for several hundred miles, enough to wear out the excellent IRC VE-21, 22 tires. Nothing broke or bent, not even a foot lever. The folding brake and shift levers were jammed into trees and rocks several times, but finished the test undamaged.
YAMAHA
IT175G
SPECIFICATIONS
$1399
Complaints about the IT 175 were few; gas consumption is a little high when ridden in an aggressive manner (we only got 56 mi. on a tank riding hard in the mountains) and the engine could have better low end. Yamaha has been doing some R and D on the IT 175 and suggested a couple of changes to the bike in the interest of torque and low-end power. We borrowed another identical IT and performed the modifications on it. That way we had a completely stock machine for comparison. The mods work; low end power is much improved and the bike becomes even more fun to ride.
We rode the IT at elevations above 8,000 ft. on several occasions. Like most bikes jetted for lower levels, the IT ran too rich. Rather than rejet the carburetor, we decided to experiment with the power jet. Since the power jet adds fuel from midrange through top revs, and the IT was too rich in this range, blocking the power jet should lean everything out. We slipped the hose off the top of the power jet, plugged it with a small stick, took the float overflow tube off and placed it on the top of the power jet and also plugged it.
The modification took less than a minute and corrected the richness. Next time we went to the mountains we took an alligator clip along and simply clamped it around the feed hose, (It’s the black hose that goes from the float bowl to the top rear of the carb) and presto, the bike was adjusted for the higher elevation. Anyone blocking the power jet for use at higher elevations should be careful not to use the bike at lower levels with the unit blocked, because the leanness could cause a seizure.
The little IT does almost everything well and it does a couple of things better than any other bike. We took the IT down a dry creek where the smallest rocks were the size of bowling balls and the larger ones were really big. The area is under a raging creek in the spring of each year, and the rocks are extremely smooth and tricky to cross. The 175IT was a breeze. It went through easier, with less effort on the part of the rider, than any bike we have tried in them. It stays straight, doesn’t dart off to the side and the low seat gives the rider the option of putting his feet down for balance when necessary or desired. A trials bike wouldn’t go through any better.
If it sounds like we are impressed with the IT175, you’re reading the test right. It is one of the most competitive and fun bikes available, and best of all, it only costs $1399.
