Dolmar Chainsaw Repair Manual

SERVICE MANUAL

SAW CHAIN

Saw Chain, Guide Bars and Sprockets SAW CHAIN

CHAIN TYPES

CHAIN NOMENCLATURE

The two common types of chain cutters are chipper and chisel. Note in Fig. CM4 that cutting edge of chipper cutter is round while cutting edge of chisel cutter is square. Different configurations of chisel and chipper cutters may be used to meet specific cutting requirements. Refer to subsequent CHAIN SHARPENING section for procedures and tools used when sharpening chipper and chisel chain types.

Anti-kickback saw chain uses drive links or side links which extend as they travel around tip of bar thereby preventing contact between cutter link and wood. Refer to Fig. CM5. Possibility of saw kickback is lessened if cutter contact is prevented as chain travels around bar nose.

Note component parts of chain shown in Fig. CM1 exploded view. The cutters remove material being sawed while saw chain is driven by engagement of drive links with engine sprocket. Side links connect drive links and ride against bar. Special chain types such as anti-kickback or ripping chain may use components designed as a safety feature or for specialized cutting.

CHAIN SIZE Saw chain size is determined by chain pitch and gage. Pitch is the distance between alternate chain rivets divided by half as shown in Fig. CM2.

Common pitch sizes are lk, 3/8, 0.404, 7/16 and Vz inch. Gage is the drive link thickness measured at the tang as shown in Fig. CM3. Common gage sizes are 0.050, 0.058 and 0.063 inch.

Chain size must be matched with engine drive sprocket and bar sprocket, if so equipped. Mismatching chain and sprocket will result in damage to both components as well as possible damage to engine should chain break.

SIDt LINK

CHIVE IINK

5. Recheck tension until chain is fully broken in.

6. Keep chain well lubricated when in use.

7. Keep chain sharp.

8. Correct chain tension, especially on bar lengths of 32 inches and over, is important to prevent the chain jumping the bar and causing damage to the equipment and loss of time to the operator.

CHAIN BREAK IN, TENSION AND LUBRICATION BREAKING IN A NEW CHAIN. As

with any machine or accessory containing moving parts, the first hour or so of operation can make a great difference to the length of life. Careful attention to the instructions for breaking in and making tension adjustments can greatly add to the- life of the chain.

The following instructions are important and will add to the life of saw chain: 1. If possible, soak chain in oil bath before use and between uses.

2. Install chain properly with recommended chain tension.

3. Run chain at slow speed for about 5 minutes, giving it plenty of oil.

4. Stop engine and readjust chain tension.

Fig. CM4—Vlew of chipper and chisel cutters.

Fig. CM1 — Exploded view of typical section of saw chain.

Pitch" = this distance divided by

oo the drive link

Fig. CM2— Chain pitch Is measured between rivet pins as shown above.

Fig. CM3—Saw chain gage size Is thickness of drive link tang (T).

Fig. CMS—Protruding drive links of antlklckback chain prevent cutter contact with wood as cutters travel around bar nose.

CHAIN SAW

SAW CHAIN by removingl damaged Links and installing new links which requires disconnecting chain (chain breaking). Use of a chain breaker is the preferred method of removing llchain rivets when disconnecting a chain. When a chain breaker is not available, such as at the work site, file off lithe rivet head and drive out the riven using a sharp punch. A small chisel or screwdriver may be used to spread side links if rivet is not completely cleared.

Rivet spinning tools are available to install rivets when assembling chain links. If a spinner is not available, then a ball peen hammer may be used if special care Is taken. DO NOT strike the rivet heaa too hard. This can cause a fracture in ihe rivet drum. The rivet can be peened over on the outside circumference with light taps of the CHISEL. Refer to Fig. CM4 for view hammer. The rivet should not have a of chisel type saw chain. To sharpen flat appearance caused by pounding the chisel chain a bevel or round file is used, rivet and making it spread from the depending on manufacturer. Hold file at center. Rivets that are pounded flat a 10° angle as shown in View B of Fig. will not have enough strength around CM21. Note top and side plate angles in the circumference. See Figs. CM24 and Fig. CM22. Refer to CHIPPER CHAIN CM25. section for depth gage settings.

CHAIN TFflOUBLE DIAGNOSIS GULLETS. The gullet is the open area between the depth gage and the If the chain] is not performing satisside plate. The gullet should be cleaned factorily: out with a round file before every fifth 1. Remove dhain from bar. sharpening. This will keep the gullet 2. Clean wjith solvent to remove open and allow better chip clearance pitch and resii and more efficient side plate cutting 3. Compare I chain with the illustraaction. Hold file level as shown in Fig. tions and list||shown in accompanying CM23 and at a 20° angle with cutter. table.

4. Repair as|| indicated.

REPAIRS information can be used as a guide.

A. On larger horsepower saws and saws with slow chain speeds, the depth gage distance may be increased, which will allow the cutter to take a larger chip. The depth gage distance should be decreased on small saws and direct drive saws.

B. When cutting continually in soft woods, the depth gage distance can be increased somewhat.

C. When cutting hard woods, frozen or resin timber, the depth gage distance should be decreased.

When sharpening the cutting edges on the saw chain, the drive link tangs should also be sharpened to keep the guide groove clean, and any burrs on the sides of the drive link tangs should be removed.

special equipment for re-hardening the rails.

Small kinks or bends in guide bars can be removed by laying the bar on the large true anvil or other similar work surface and using light hammer blows to bring the bar back into shape.

See Fig. CM26. Technique is very similar to straightening other flat metal pieces.

Use a file to funnel the entrance to the guide rail groove of the bar as

Fig. CM23—Before every fifth sharpening, clean out gullets with round file. Hold file level and at 20 degree angle to cutter.

GUIDE BARS

Saw chain repairs are accomplished

SOLID NOSE BARS 10°

Fig. CM21—Hold file level for chipper chain as shown In View A. File must be held at 10 degrees for chisel chain as shown In View B.

Guide rails sometimes split from the bar being (inched while the saw is hung up in a it. Splits of two inches long or less c« be repaired by using ordinary welc methods on bars with non-hardened ils. Repairing splits on bars with hardened rails requires Fig. CM24—Rivets can be Installed using a ball peen If carefully done.

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CORRECTLY PEEKED RIVET

INCORRECTLY PEENED RIVET CRACKED DRUM

Top Plate Filing Angle 20°. Gradually increase angle as cutter is filed back.

Side Plate Angle 90°.

op Plate Cutting Angle 5°-55°.

Fig. CM22—Vlew of top and side plate specifications t r chisel chain.

NO CLEARANCE BETWEEN LINKS RIVET HEAD TOO SMALL

RIVET DRUM SQUEEZED

Fig. CM2S—Views showing correctly Installed rivet and rivet damaged by Incorrect Installation.

SERVICE MANUAL

SAW CHAIN

common problems found with CUTTERS and LINKS FAILURE

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REMEDY

Chain run too tight Insufficient lubrication Cutters dull.

Decrease chain tension Check oiler, file cutters

Heel wear on cutters ana side links.

Cham run too loose Too much joint Cutters dull

Increase chain tension Maintain basic 025" joint.

File cutters

Slight heel wear cutters and side links.

Back slope on cutters— chain slightly tight Cutters dull

Concave side link and cutter bottoms

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CAUSE

FAILURE

CAUSE

REMEDY

Abrasive cutting condition

Check for grit m timber being cut Lubricate well.

Back nicked.

Cham run too loose.

Increase tension

Back rounded to bottom

Worn sprocket Cham run too loose.

Increase tension Renew sprocket

Back and front of link peened

Worn or wrong pitch sprocket

Rene* sprocket Increase tension

Back peened

Worn sprocket Dull cutters.

Renew sprocket.

File cutters

Side wear

k

(o~o)

Remove back slope Decrease chain tension File cutters

^ (o^§>

Excessive bottom wear on cutters and side links

Insufficient joint— chain run tight, filing blunt— no undercut, cutters dull

Increase iomt to 025" Decrease tension— refer to filing instr File cutlers

Severe side wear and abrasive damage

Caused by striking stone or nails, etc Cutters dull

All visible abrasion must be removed by filing cutters back File cutters

Crack under rear rivet.

Cutters dull or hooked.

Refer to filing instructions

(p~o)

Bottom peened and worn

Crack under front rivet

Insufficient joint

Increase joint to basic 025"

(o~o)

Bottom point rolled up

Link bottoming in worn sprocket Dull cutters

Renew sprocket File cutters

Cracks under both rivets.

Cham run dull and

Refer to filing instr Increase joint to basic .025".

(o~o)

Bottom rough and broken off.

Cham run too tight causes stretch and climbs up on sprocket teeth

Renew worn chain or sprocket Run chain with less tension

<p

Lin.; riding on bottom of bar groove Bar rails worn Dull cutters

Renew bar File cutters.

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joint.

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Bottom peened and burred

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dull— no undercut causes chain to pound on rails

Eliminate hook.

Refer to filing instructions.

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front peened

(o^g)

Cham run too slack— crowds at bar entry

Increase tension

Clearance notch peened

Sprocket teeth worn

Renew sprocket

angle of cutters causes side thrust

Drive lugs worn on one side.

Excessive face angle of cutters on one side

Cutters must have equal face angles.

Cham jumps out of bar groove

Uneven filing.

Chain run too loose

Increase chain tension Refer to filing instructions

-V

^l ^^ -8

V

(2^2) I A

^1

Refer to filing instructions.

on sides

(cTo) fj

CHAIN SAW

SAW CHAIN shown in the "right" view in Fig. CM27. If the guide rails are as in the "wrong" view in this illustration, damage to the chain can occur as the chain enters the groove.

Check the fit of the chain to the guide bar as shown in Fig. CM28. If the tangs of the drive links touch the bottom of the guide rail groove, poor cutting and damage to the chain will result. The side links of the chain should ride on the rails and the tangs should clear the bottom of the guide groove. When replacing a chain or a guide bar, the length of the tang and the guide bar groove depth should be checked.

If the guide rails are worn or rough, they can be ground smooth and the groove deepened on a special bar grinding machine.

ROLLER AND SPROCKET NOSE BARS LUBRICATION. The precision bearings in the roller and sprocket nose bar must be lubricated regularly for efficient operation and long life. Grease nose bearing every time saw is refueled. Always grease the bearing after

a day's use. G oil hole and ii good type h needle nozzle, center of rolle and pump gui rim of roller grease may operation,

ease bearing by cleaning serting grease with any id grease gun with a nsert nozzle into hole in as shown in Fig. CM29 until grease flows from or sprocket. A lighter necessary for winter

ROLLER SIDE PLATE CARE. Re fer to Fig. C .30. Remove burrs that form on side ate of roller with a flat file. Pump bei *ing full of grease before filing. File aw from slot so filings will not get into b taring. Wipe filings from inside and o tside of roller before mounting chai ROLLER ND SPROCKET RENEWAL. Roll* r and sprocket may be removed by rilling or punching out retaining rive in end of guide bar.

Remove roller or sprocket and install new roller or rocket with new retaining rivets. Ca should be taken not to damage rivets or mounting holes when peening or driving out rivets.

NOTE: Be ure sprocket size is matched to hain size. Mismatched sprocket and lain will cause excessive wear.

Fig. CM26— Use steel shim 0.004 Inch thicker than drive link tangs to close spread bar rails.

Fig. CM27— Cut tunnel shaped opening to guide groove with tile.

WRONG

SPROCKETS AND CLUTCHES SPROCKETS Two types of chain drive sprockets are used: The integral star and the self-aligning rim sprocket shown in Fig. CM31. The integral star sprocket is permanently attached to the clutch drum. The self-aligning rim sprocket assembly shown in Fig. CM32 consists of a splined hub fastened to the clutch drum and the rim sprocket is located over the splined hub. The sprocket is permitted to float on the splined hub and automatically align with groove in the guide bar. Sprockets for gear drive saws fit on the output shaft instead of a hub on the clutch drum.

FAILURES AND CAUSES. Drive sprockets are, like any moving part subject to extreme friction, subject to wear. A worn sprocket can quickly damage the bar and the chain. The illustrations in Fig. CM31 are typical examples of worn sprockets which should be renewed to keep from damaging the bar and chain. Wear on the sprocket teeth can be caused by any of the following: 1. Wrong pitch chain.

2. Insufficient chain lubrication.

3. Excessive chain tension.

4. Improper chain filing and jointing.

5. A badly worn and possibly stretched chain has a slight varia-

Flg. CM29—Lubricate roller or sprocket nose bar.

RIGHT

Fig. CM28—Guide groove too shallow In cross section view ot left. Tang must clear bottom ot groove as In cross section view at right.

Fig. CM30—Remove burn from roller side plates.

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SERVICE MANUAL

SAW CHAIN

tion in pitch which will contribute to rapid wear of sprocket teeth.

6. A badly worn bar will contribute to rapid wear of the chain which will cause the sprocket to wear.

Rapid deterioration and wear on chain drive lugs, side links and cutters will result from installing a new chain. Never install a new chain on a worn sprocket or bar.

Fig. CM31—Vlew of self-aligning sprocket (left) and worn integral star sprocket (right).

CLUTCH CLUTCH BEARING. The clutch drum and sprocket can rotate freely (or stop) when the clutch is disengaged. A caged needle roller bearing is located between the clutch drum hub and the shaft. The bearing on most models uses the shaft as the inner race and the clutch drum hub as the outer race and can be removed by hand without any special tools.

Clutch needle bearing failure is often caused by storing the saw after operating under extremely wet conditions.

The water will penetrate the needle bearing, form rust and cause the needles to become locked. It is recommended that the clutch drum be removed periodically (depending on local conditions) and the bearing repacked with a good grade of water-resistant grease (not water pump grease).

CLUTCH DRUM AND SHOES. Rapid clutch drum wear, shoe glazing

Bar-\M I.

NEEDLE

Chain—

or I

OILITE

BEARING

Rir Fig. CM32—View of typical self-aligning sprocket and clutch assembly. Note that sprocket can float on splined hub to align with bar groove.

or grooving may be caused by any of the following: 1. Improper filing. Hooked cutters and excessive joint will especially cause the clutch to slip.

2. Chain pinched in cut causing clutch to slip. Throttle should be

released immediately when chain becomes pinched.

Oil soaked or worn clutch shoes.

Clutch shoes should be inspected periodically. Glazing can be removed by wire brushing or other similar method.

OFF-SEASON STORAGE When storing a chain saw for periods longer than 30 days, the following storage instructions should be followed: Drain all fuel from the fuel tank. Start and run the engine until it stops to remove fuel from carburetor. Drain oil from oil tank. Remove guide bar and chain and clean them thoroughly. Store the chain in a small container with engine oil covering the chain. Apply light coat of oil to guide bar and wrap it in

paper. Clean exterior of the saw. Remove the spark plug and pour one teaspoon of two-cycle engine oil or a rust inhibitor product into the combustion chamber. Install spark plug and pull starter rope slowly several times to distribute the oil over the cylinder. Store the saw in a dry, well-ventilated place away from corrosive agents such as garden chemicals and fertilizer.

To remove saw from storage, remove spark plug and pull starter rope several times to clear cylinder of excess oil.

Clean and gap spark plug or install a new spark plug. Install guide bar and chain and adjust chain to proper tension. Fill fuel tank with fresh fuel/oil mixture. Do not use old fuel that has been stored more than 90 days. Fill chain oil tank with clean chain oil.

11

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