CRF250R - Mulders Motoren

CRF250R - Mulders Motoren
Model updates: The CRF250R gets a substantial top-end power boost from a new HRCdeveloped cylinder head, piston and con-rod, with stronger bottom-end torque and no loss of
mid-range performance. Showa’s SFF-TAC-Air forks receive upgrades to reduce friction and
improve response and damping; Showa rear shock has new settings to match.
There’s no tighter competition than the elbow-to-elbow MX2 class, at amateur or professional
level. And Honda’s CRF250R has long been a potent weapon to take into battle thanks to its
fluid power delivery and honed chassis that balances lightning-fast agility with sure-footed
stability. It shares the same aluminium beam frame and mass-centralised design philosophy as
the CRF450R and turns as well airborne as it does on the ground.
Honda CRF250R 2016
1. Introduction
2. Model overview
3. Key features
1. Introduction
The 15YM CRF250R received 49mm Showa Separate Front with Triple Air Chamber (SFF-TACAir) fork, to fully exploit the chassis’ ability. It also got the same Engine Mode Select Button
(EMSB) as its larger-capacity sibling, giving a choice of 3 riding modes – standard, smooth or
aggressive – for the rider to select from the right side of the handlebar.
But nobody rests when it comes to MX2 development and the smallest improvements can
make the biggest differences when combined. For 2016 Honda has dialled in an array of
upgrades to the CRF250R’s engine and suspension, driven entirely by what Team HRC learn
racing week in week out against the world’s best in MXGP.
2. Model Overview
The main focus of the 2016YM CRF250R revolves around a completely revised cylinder head,
piston and con-rod. And the result is power – and a good deal more of it up top, with no loss of
bottom end response, throttle feel or delivery. In fact low-rpm torque is improved, as is highrpm over-rev. The exhaust downpipe now features a resonator chamber and the twin rear
mufflers redesigned internals. The airbox, too has been revised to improve air flow.
Showa’s SFF-TAC-Air forks receive a host of internal changes plus an extra 5mm length in the
top tubes to enhance traction, suspension reaction, rider feel and adjustability. The rear shock
setting is also adjusted to match. Other changes include a reduction in final drive chain roller
diameter and improved mud-clearing ability for the footpegs.
3. Key Features
3.1 Engine
The CRF250R’s 249cc four-valve Unicam engine retains a bore and stroke of 76.8mm x
53.8mm. Peak power is now 29.4kW @ 11,500rpm (from 28kW @ 11,000rpm) with peak
torque of 27.1Nm @ 9,000rpm (from 26.5Nm @ 8,500rpm).
The new engine is smoother and stronger off the bottom, maintains its mid-range punch and
as revs rise makes not only more power and torque, holds onto it at higher rpm and for
noticeably longer – useful for stringing sections or corners together without changing gear.
The increase in peak power and torque – with zero sacrifice anywhere else in the rev-range –
is due to extensive HRC development of the cylinder head. It starts, however with a new,
lighter piston which also delivers a compression ratio of 13.8:1 (up from 13.5:1). It’s matched
to a lighter con-rod, with revised shape, that contributes to the power gain.
On the intake side the airbox features an added air intake duct plus revised inner duct length
and insulator. Both the intake and exhaust ports are redesigned to HRC-specification and the
25mm diameter exhaust valves are now titanium (rather than steel) matching the 30.5mm
intake valves. A brand new camshaft profile operates redesigned valve lifters; both intake and
exhaust valve lift has been increased. The inlet valve spring material is also new. The PGM-FI
Dual Fuel Injection – with 46mm throttle body -– features new settings to match the engine’s
new free-flowing head.
Honda CRF250R 2016
The exhaust employs a resonator tucked away between the pipe and engine which helps
improve drivability. Both mufflers use new connector tubes and inner pipe punch pattern, plus
larger tail-end diameters. The left hand radiator is larger to cope with extra heat generated by
the power boost and the gearbox now has a bearing-type shift drum stopper for improved feel
at the gear lever. The chain roller diameter has decreased, from 38mm to 34mm.
Honda’s EMSB makes an already very usable engine even more adaptable. This is a plus for
the club racer in particular; rather than set up during the week and hope for matching
conditions at the weekend, the rider just has to stop with the engine at idle and press and hold
the button for just under a second to select the next map in sequence.
A highly visible LED built into the lightweight button signals the map in use with a quick press
and number of subsequent flashes. If a new map is selected the choice is also confirmed to the
Mode 1 uses the standard combination of ignition and fuelling maps to present a balanced
power and torque delivery. Mode 2 is designed for use in slippery, muddy conditions and is all
about throttle control, giving easy-to-manage feel that hunts out every last scrap of traction.
Mode 3 hits hard with aggressive and responsive top-end power to drive through soft sand.
Mode 2 and 3 can be further tailored via the existing HRC mapping hardware and software.
3.2 Chassis
The 49mm SFF-TAC-Air forks were developed specifically for the CRF250R by Showa to unlock
the frame’s performance potential and save over 1kg in weight compared to conventional
forks. The fully adjustable right fork leg controls both compression and rebound damping force
while the left fork leg compresses air using a damper-less structure. This distribution achieves
a controlled right/left balance.
Three chambers are used by the left fork leg to manage suspension reaction (or effective
‘spring’ rate). The Balance chamber operates from the off and at low speed; the Inner
chamber is responsible for the mid-range stroke and the Outer Cylinder chamber is used as
the forks near their bump stops.
Both fork legs employ the same stroke and internal dimensions as employed previously but
have received extensive development – the two main goals to reduce friction through short
strokes, improving suspension reaction speed and also to increase reaction force at midstroke, boosting control during pre-jumping and landing. Both rebound and compression
damping characteristics have been increased to suit the new set-up.
The top tubes are 5mm longer above the top yoke, and to reduce internal friction – by approx.
25% – the construction, shape and number of inner air seals has been finely adjusted. 80kPa
air pressure has been added to the Outer Cylinder chamber; previously this contained 0kPa. It
also receives a dedicated air valve for adjustment. Both the Inner and Balance chambers now
use 1075kPa, from 1200kPa/1125kPa. The damping adjustment range increases from 4
click/rotate to 8 click/rotate.
The compact Showa shock mounts low within the frame spars. To balance the changes up front
– and maximise rear-wheel traction – -it now uses a heavier spring rate in the early part of its
stroke. Rebound damping remains unchanged but compression damping increases (compared
to 15YM) from mid-stroke on as the piston speed rises.
Fully adjustable, the rear shock features 17-position rebound adjustment; compression
damping is separated into 13-position (low-speed) and 3.5 turns (high speed). Honda’s ProLink rear suspension linkage operates CRF250R-specific ratios and allows 31.7cm of travel. The
aluminum swingarm features deep beam height in the front and centre sections, minimising
rut deflection and improving rear tyre traction on corner exit.
Honda CRF250R 2016
The CRF250R’s aluminium twin-beam frame – in its sixth generation – was designed from the
outset around the use of air forks and with mass centralisation at its core. It is unchanged for
2016. Rake is set at 27.23, with 117mm trail and wheelbase of 1,489mm. All-up kerb weight is
105.6kg. A CRF250R-specific lower cradle houses the engine.
The 16YM CRF250R’s bodywork is also unchanged and maintains Honda’s man
maximum/machine minimum ethos that’s built around the need for a rider to move freely;
efficient riding ergonomics are at the heart of the CRF250R shape. The radiator shrouds, side
covers, lightweight seat and fuel tank offer a slim, smooth and continuous transition allowing
the rider huge freedom and flexibility of movement. Detailed improvements to the footpegs
and their mounts make it much harder for close-packed mud to jam the footpeg in an ‘up’
A 260mm wave-pattern front disc delivers superb heat dissipation, power and feel from the
two-piston brake caliper working it; a matching 240mm wave-pattern disc and single-piston
caliper is at the rear. Lightweight aluminium rims wear Dunlop MX52F/MX52 80/100-21 front
and 100/90-19 rear tyres.
Honda CRF250R 2016
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