TE 250/300 Rebuild Guide

Before You Start Tools, parts, fluids & safety ▸

This job is a top-end rebuild done with the engine in the frame — cylinder head, cylinder, piston, rings, power valve and reed valve. It also folds in the bottom-end inspection checks you asked for (crank runout, con-rod play, case bearings) even though those normally only get opened up once the cases are already split.

Hot / Sharp Let the engine cool fully before draining coolant or pulling the head. Exhaust flange, power valve and cylinder fins stay hot long after shutdown. Piston ring edges and the exhaust port are sharp — a fresh top end has bitten more than one set of knuckles.

Tools beyond a standard socket set

torque wrench 1–30 Nm range (small-fastener wrench helps for the 1–8 Nm reed/power-valve screws)
deck/timing tool Nihilo Concepts stainless Timing/Deck Tool — used in place of the Husqvarna setting gauge for X-distance and Z-distance, see callout below
feeler gauges 0.05–1.00 mm — still needed alongside the deck tool for ring gap, X/Z readings, and con-rod play
bore gauge / micrometer cylinder bore and piston diameter
dial gauge + V-blocks only if checking crank runout (bottom end, case split)
circlip pliers piston pin locks

Deck tool swap This guide uses the Nihilo Concepts Timing/Deck Tool (250/300cc 2-stroke version) instead of Husqvarna's own special tools for the X-distance and Z-distance checks in Reassembly — it replaces the OEM setting gauge (54829001100) and depth micrometer (T107S) with one laser-cut piece. Nihilo lists this tool against the KTM/GasGas 250/300 SX & XC-W 2-strokes by name; the TE 250/300 shares that same engine architecture and the same X/Z targets from Husqvarna's own spec sheet, but confirm fitment for your exact year with Nihilo or your dealer before you're mid-rebuild with the cylinder off. Read the instructions that ship with the tool for exactly how it registers on the deck and how to read it — that placement/reading detail isn't something this guide verifies independently.

Parts to have on hand

mandatory cylinder base gasket(s), cylinder head O-rings, new piston pin circlips
wear items piston + ring set, wrist pin, small end / upper con-rod bearing
check first reed petals, power valve O-rings and bearing sleeves, spark plug
bottom end con-rod + big-end bearing + crank pin kit, case bearings, crank seals — only if inspection below finds them out of spec

Fluids & sealants

Thread locker, generalLoctite® 243™

Thread locker, high-strengthLoctite® 2701™

Case sealantLoctite® 5910

Assembly oil (bearings, con-rod)15W/50 engine oil

2-stroke premix oil, tank~0.6 L

Gear oil0.80 L15W/50, shared clutch/trans oil

Note If you pull the piston or cylinder with the engine still in the frame, the auto-lube oil pump line needs re-priming before startup (fill the tank, cycle the pump with the diagnostics wake-up connector, or crack the pump-to-cylinder line until oil runs bubble-free).

Top-End Teardown Head → cylinder → piston → power valve ▸

Cylinder head

1Pull both injection valves (left and right side of the head).
2Remove the spark plug.
3Loosen the head screws in a crisscross pattern, then lift the head off.
4Peel off both head O-rings — replace on reassembly, don't reuse.

Cylinder

1Remove the two power-valve linkage covers on the cylinder.
2Pull the ball-socket retainer and ball socket, then the gaskets on both sides.
3Remove the cylinder base nuts — raise the cylinder slightly to clear the front nuts.
4Slide the cylinder straight up off the studs. Take off the base gasket.

Piston

1Stuff a clean rag into the crankcase mouth so nothing falls in.
2Pop one piston-pin circlip, drift the pin out, and lift the piston off the rod.
3Remove the upper (small-end) con-rod bearing from the rod's little end.

While it's open This is the point to also pull the reed valve housing and power valve assembly for cleaning and inspection — see the checklist in Inspect & Measure.

Inspect & Measure Decide what actually needs replacing ▸

Piston & rings

Piston bearing (skirt) surface free of scoring, discoloration, or scuffing — any damage means replace piston and check cylinder Rings move freely in their grooves (clean the groove with an old ring if sticky) and show no chips or broken ends Piston pin has no discoloration or wear signs; pin seats in the rod's small-end bearing with no detectable play

Piston diameter measured 50 mm up from the skirt, 90° to the pin bore — 66.340–66.360 mm71.925–71.944 mm

Diagram

Measure across the skirt 50 mm up from the bottom, at a right angle to the pin bore — 66.340–66.360 mm71.925–71.944 mm.

Ring end gap, measured 20 mm below the cylinder's top edge — max 0.60 mm0.40 mm per ring

Diagram

Push the ring square into the bore about 20 mm down from the top edge, then slide a feeler gauge into the gap — max 0.60 mm0.40 mm per ring.

Cylinder

Bore wall free of scoring or damage (if damaged, replace cylinder and piston) Bore diameter measured at several points on the X and Y axes to catch ovality — 66.400–66.425 mm72.000–72.025 mm Head sealing surface checked with a straightedge and feeler gauge — distortion max 0.10 mm Piston-to-cylinder running clearance (smallest bore − largest piston) — new-condition target 0.050–0.074 mm0.066–0.088 mm, wear limit 0.10 mm

Power valve (exhaust control)

Fully strip it while the cylinder's off — carbon buildup here is the single biggest killer of 2-stroke top-end power.

Control shafts, gear segments and bearing sleeves show no wear or slop Control flap (guillotine) moves freely, no cracking, no excess carbon binding it Return spring, linkage ball-head, centrifugal governor and its thrust bearing all move smoothly with no play All O-rings and bearing sleeves replaced/re-greased on reassembly

Reed valve & intake

Reed petals sit flat with no lift-off, cracking, or chipped tips at the seat Reed housing sealing face and intake flange free of cracks or wear

Sizing Husqvarna ships piston and cylinder in matched Size I / Size II pairs, stamped on the piston crown and the cylinder's right side. Keep the pairing — a Size I piston in a Size II bore (or vice versa) will throw your running clearance out.

Bottom-End Inspection Crank, con-rod & case bearings ▸

Scope check Everything below needs the crankcases split — it is not accessible with just the cylinder off. Husqvarna bundles this into "major engine service": the connecting rod, big-end bearing, crank pin and every case bearing get replaced as a set, not inspected piecemeal, because the crank has to be pressed apart to get at any of them anyway.

Connecting rod / crankshaft

Con-rod axial play (side-to-side slop at the big end), measured with a feeler gauge against the crank webs — target 0.60–0.70 mm

Diagram

The rod's big end should have a small, even side-to-side gap against each crank web — check both sides with a feeler gauge, target 0.60–0.70 mm total.

Con-rod rotates freely on the crank pin with no roughness or radial play at the big end

Crankshaft run-out at each bearing pin, checked on roller blocks — max 0.03 mm (re-true or replace the crank if it's out)

Diagram

Support the crank on V-blocks (or rollers) and read total indicated run-out at each bearing pin while turning it slowly by hand — max 0.03 mm.

Small-end (upper con-rod) bearing and piston pin fit checked for play — if loose, the rod, bearing, and crank pin all get replaced together

Case bearings & seals

Crank main bearings spin smoothly with no notchiness, noise, or axial play in the races Transmission shaft and shift-drum bearings show no play or roughness Crankshaft radial shaft seals (both sides) not hardened, cracked, or leaking — cheap insurance to replace anytime the case is split Shift-shaft, countershaft and balancer-shaft seals in the same condition check

Press job Pulling the con-rod off the crank pin and pressing a new one on needs the crankshaft pressing tool and matched inserts to keep the crank webs aligned — this is not a job for a bench vise and a socket. If the axial-play or run-out numbers above are out of spec, this is a specialist or dealer job unless you already own that press tooling.

Reassembly Piston → cylinder → head, torqued to spec ▸

1Oil the small-end bearing, seat it in the rod, position the piston with the marking on the crown facing the exhaust side, and slide the pin in by hand. Fit both new circlips with the gap away from the opening (6 or 12 o'clock).

Diagram

The piston crown carries a small marking that must point at the exhaust port — drawn here on the right just to show the idea. Confirm which side is actually the exhaust on your own cylinder before the piston goes in.
2Oil the bore and piston. Fit the rings so the anti-rotation pin in each groove engages the ring end gap, then lay a new base gasket down.

Diagram

Each ring's opening locates over a small pin cast into the groove so the ring can't rotate. Miss this and a ring end can catch a port edge and shatter on the first start.
3Compress the rings by hand as you lower the cylinder over the piston — go slow, don't let a ring end catch the port edge.
4Fit the base nuts and snug in a crisscross pattern to 35 Nm.

Diagram

Crisscross concept: snug opposite fasteners in numbered order, then bring all of them up to 35 Nm on a second pass. The count and layout here are generic — use this same opposite-pairs logic on your actual base nuts.
5Check X-distance (piston crown height vs. cylinder top, at TDC) with the Nihilo Concepts deck tool and a feeler gauge — target 0–0.10 mm. Out of range means swapping to a thicker or thinner (or stacked) base gasket and re-checking. Follow the tool's own instructions for exactly how it seats on the deck.

Diagram

With the cylinder clamped down and the piston at TDC, X is the gap between the crown and the cylinder's top edge — target 0–0.10 mm. Too big and compression drops; too small and the piston can kiss the head.
6Rebuild the power valve linkage, then use the same deck tool's timing/Z side (or a depth micrometer if you'd rather) to set the control-flap height to 49.0 mm49.5 mm before locking the adjuster nut to 8 Nm.

Diagram

Z runs from the cylinder's top edge down to the flap's lower edge, measured at the middle of the port — target 49.0 mm49.5 mm.
7Fit new head O-rings, seat the head over the dowels, and torque the head screws in a crisscross pattern to 27 Nm — use new washers.

Diagram

Same logic as the base nuts: opposite screws first, work outward, final pass to 27 Nm. Count and layout shown are generic.
8Fit the spark plug to 25 Nm (gap 0.6 mm, NGK BR7ES), and reinstall the injection valves.
9Re-prime the oil pump line before first start if it was disconnected. Warm the engine, then re-check for leaks at the base and head gaskets.

Break-in Treat a new piston/ring/cylinder combo like a new engine — vary the throttle, avoid sustained full load, and let it heat-cycle a couple of times before you lean on it.

Torque Quick-Reference Everything you'll touch on this job ▸

Cylinder & head

Nut, cylinder baseM1035 Nm25.8 lbf·ft

Stud, cylinder baseM1012 Nm8.9 lbf·ft

Screw, cylinder headM827 Nm19.9 lbf·ft

Spark plugM14×1.2525 Nm18.4 lbf·ft

Screw, cyl. head temp sensorM10×1.2512 Nm8.9 lbf·ft

Screw, injection valve holderM55 Nm3.7 lbf·ft243

Power valve / exhaust control

Nut, power-valve adjuster (Z-dist. lock)M68 Nm5.9 lbf·ft

Screw, exhaust flangeM68 Nm5.9 lbf·ft

Screw, exhaust control thrust bearingM68 Nm5.9 lbf·ft243

Screw, control flapM610 Nm7.4 lbf·ft243

Screw, bearing support / angle leverM56 Nm4.4 lbf·ft243

Screw, retaining bracketM56 Nm4.4 lbf·ft2701

Screw, exhaust control capM55 Nm3.7 lbf·ft

Screw, exhaust control coverM54 Nm3 lbf·ft

Vacuum connection, cylinder / breatherM62 Nm1.5 lbf·ft243/2701

Reed & membrane screwsEJOT1 Nm0.7 lbf·ft

Bottom end & cases

Screw, engine caseM610 Nm7.4 lbf·ft

Screw, bearing retainerM56 Nm4.4 lbf·ft243

Nut, rotorM12×160 Nm44.3 lbf·ft

Screw, balancer shaftM830 Nm22.1 lbf·ft243

Nut, inner clutch hubM18×1.5100 Nm73.8 lbf·ft243

Nut, primary gearM18×1.5 LH150 Nm110.6 lbf·ft243

Gear oil drain plugM12×1.520 Nm14.8 lbf·ft

Screw, shift leverM614 Nm10.3 lbf·ft243

Note the primary gear nut is left-hand thread.

Water pump (in the way of the cylinder)

Screw, water pump coverM610 Nm7.4 lbf·ft

Cap nut, water pump impellerM65 Nm3.7 lbf·ft243

Drain plug, water pump coverM610 Nm7.4 lbf·ft

Other 160-Hour Items What else is due while you're in here ▸

How this list was built Husqvarna's own schedule doesn't print a 160-hour line — its longest recurring intervals are every 40 hours (required work, or "used for motorsports") and every 80 hours (recommended work). 160 hours is exactly 4×40 and 2×80, so everything at those intervals is due now, plus anything on a 12- or 48-month clock if that much calendar time has also passed.

Due every 40 hrs · required work

Due every 80 hrs · recommended work

Calendar-based, if that much time has also passed

Change the coolant annual Change front/rear brake fluid and clutch fluid on the 12-month clock even if under 80 hrs

Heads up If you're not racing this bike hard, the "every 40/80 hours" columns are the motorsports/recommended pace — Husqvarna's required-work floor for trail use is every 20 hours for most safety checks. Ride type changes how often this list actually comes due; the 160-hour math above assumes fairly hard use.

Top-End Rebuild

Tools beyond a standard socket set

Parts to have on hand

Fluids & sealants

Cylinder head

Cylinder

Piston

Piston & rings

Cylinder

Power valve (exhaust control)

Reed valve & intake

Connecting rod / crankshaft

Case bearings & seals

Cylinder & head

Power valve / exhaust control

Bottom end & cases

Water pump (in the way of the cylinder)

Due every 40 hrs · required work

Due every 80 hrs · recommended work

Calendar-based, if that much time has also passed