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2021/06/21

MODEL

ITEM NUMBER

80458

R80458   PAGE 1/9

INSTRUCTION

Be sure to read and understand the contents before installing the product and use it properly.

Please keep this instruction manual in a safe place so that you can take it out and read it at any time.

When transferring this product or the vehicle on which this product is installed to a third party, be sure to also hand over this instruction manual.

DT125 Engine

(Narrow Pitch)

Finger-Follower DOHC 4Valve CylinderHead

UPGRADE KIT

Thank you for purchasing 

DAYTONA

’s product. Please read this instruction manual carefully before using this product. 

Be sure to check the contents of the product before installation.

If you notice any problem, please contact the dealer where you purchased the product.

Please read the following before the installation.

We are not responsible for any accident or damage caused by using the product without following the precautions in the instruction manual.

Indicates a potentially hazardous situation which, if not avoided, could result in personal injury 

or property damage.

Indicates a potentially hazardous situation that, if not avoided, could result in death or serious injury.

Warning

Caution

If you are technically unskilled or inexperienced, leave the work to an experienced store or mechanic.

Improper installation due to inexperienced skills or lack of knowledge may result in damage to parts or accidents.
Do not run the engine for long periods of time in poorly ventilated areas. 

Doing so may result in carbon monoxide poisoning.
Gasoline is extremely flammable, so keep the work area away from fire.
Evaporated gasoline may cause an explosion, so work in a well-ventilated area.

After having installed the new parts, place check each part installed and tighten all nuts, bolts and screws 

after having ridden 100km. Regular inspection of parts should be done on every 500km.

If anything unusual happens while test riding, stop at a safe place and check engine parts. 

The installing of this kit requires jacking up your motorcycle and must be done under trained hands.  

Inadequate safety precautions and professional help could result in serious injury.

Prepare appropriate tools and work equipment to avoid damage or injury to parts.

When working on the engine and muffler, be sure to do so when they are cool. 

Doing so while the engine and muffler are hot may result in burns.

Be sure to install an oil cooler and oil temperature gauge to control the oil temperature.(Keep under 110degree C) 

Continuous running at high temperatures may damage the engine.

This product has some related parts required. 

In this manual, the installation procedure is omitted for related parts products. Please note.

The price and specifications of this product are subject to change without notice. 

The same applies to the products introduced in the text. Please note.

For spark plugs, use the specified product, NGK ER8EH.
Be sure to use high-octane gasoline. Regular gasoline cannot be used because of the high compression engine.

Check and maintain the oil pump and the strainer (wire mesh) at the bottom of the pump.

Avoid sudden engine braking by downshifting. 

In the worst case, this will result in damage to the crankshaft and engine.

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Features 

Completely revised DOHC 4-valve cylinder head

Adopted finger follower rocker arms

Port geometry designed to increase intake volume and velocity

Ceramic coated all aluminum cylinder

Forged 2-ring piston, crankshaft with long connecting-rod

DLC coated piston pin

Summary of Contents for DT125

Page 1: ...losion so work in a well ventilated area After having installed the new parts place check each part installed and tighten all nuts bolts and screws after having ridden 100km Regular inspection of part...

Page 2: ...temperature gauge to control the oil temperature Keep under 110degree C Continuous running at high temperatures may damage the engine We recommend installing an oil cooler to keep the oil at the prop...

Page 3: ...1 14 JOINT SPARKPLUG CABLE 1 15 RUBBER PLUGCAP 1 16 SPARK PLUG ER8EH 1 17 GASKET CYLINDER HEAD 1 18 GASKET CYLINDER 1 19 GASKET CRANKCASE 1 20 GASKET R CASECOVER 1 22 O RING G65 1 23 GASKET 12MM RUBBE...

Page 4: ...worn parts replace them with new ones Perform the necessary work before assembly OIL OIL OIL 3 CRANKSHAFT ASSY 26 STUD BOLT A 197mm 27 STUD BOLT B 209 5mm 19 GASKET CRANKCASE STOCK STOCK 9 CAM CHAIN 1...

Page 5: ...ssemble the piston rings to the piston Assemble the piston to the connecting rod Pay attention to the direction Install the dowel pin 8x12mm into the crankcase Set the cylinder gasket and 12mm rubber...

Page 6: ...cylinder head cap nut When tightening the flange cap nut tighten it in diagonal order 3 CYLINDER HEAD LOCK 10N m Install the set screw on the exhaust flange of the cylinder head Set the dowel pin 8X14...

Page 7: ...the mark on the cylinder head with the mark on the sprocket Make sure the piston is at top dead center CAMSPROCKET MARK 4 VALVE TIMING SPROCKET Attaching the cam sprocket to the cam chain OIL Adjust t...

Page 8: ...e timing can be adjusted The standard fixing position is the one shown in the figure below Indicates the position of the bolt Advance the valve timing The engine characteristics will be slightly lower...

Page 9: ...NG G65 36 WASHER SEALING 6mm 39 SOCKET PLUG Install the spark plug to the cylinder head Do not exceed the specified torque Replace the rubber at the end of the plug cap with the rubber from the kit Co...

Page 10: ...Cylinder Head 1 1 2 21 22 25 24 25 24 23 19 16 10 11 9 8 7 6 4 15 18 14 13 12 3 17 20 5 10 11 10 14 13 12 9 8 7 6 1 CYLINDER HEAD UPPER LOWER 1 14 SCREW TRUSS M5x10 2 2 VALVE EXHAUST 2 3 VALVE INTAKE...

Page 11: ...NAME QTY SPECIFICATIONS ITEM STANDARD LIMIT Cylinder Head Warpage Valve Valveguide Rocker arm I D Valve spring free length Valve clearance Valve stem O D Valve guide I D Stem to guide clearance Valve...

Page 12: ...parts to ensure that they are reinstalled in their original locations Remove the tappet covers Remove the bolts on the head cover Remove the head upper cover Put the bolt in the position shown in the...

Page 13: ...cker arm shaft Remove rocker arm and spring Remove the shim Remove the circlip and remove the idle gear Pull out the shaft and remove the O ring Organize each part so that it can be put back in its or...

Page 14: ...t the beginning of this manual and if there is a problem replace the part with a new one Check that the bearing rotates smoothly and quietly by rotating it with your finger Check the surface of the pa...

Page 15: ...KT7 013 Install the valve springs with the tightly wound coils facing the combustion chamber Lubricate the valve stems and insert the valve into the valve guide Install the valve spring retainer Insta...

Page 16: ...the parts that come in contact Install the O ring on the idle gear shaft Install the idle gear shaft GREASE O RING P12 5 SHAFT IDLE GEAR Install the cam idle gear and circlip Apply oil to the bearings...

Page 17: ...GE 11N m Assemble the cylinder head upper Check the tappet clearance Tappet clearance Standard value INT 0 08 0 03 mm EXH 0 10 0 03 mm If it is out of the standard value replace the shim and adjust it...

Page 18: ...er head upper Torque value Hex socket bolt M6 Hex socket bolr M5 5N m M6X25 M6X25 M6X30 M5X25 M5X25 Install the cylinder head sidecover DOWEL PIN COVER HEX SOCKET BOLT M6 10N m M6X15 M6X15 M6X25 M6X25...

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