jan 27, 2005)
Vincent Motorcycle: 1.) Electric starter info and 2.) Instructions by Frances Grosset

1.) Vincent Electric Starter Information:
Four different designs of slip clutch and electric motor were tested during the development of the Vincent electric starter. The Mark IV version has been selected after a test period of 1000 starts which consisted of 50 starts per day for three weeks.
An 1100 Watt starter motor,located under the gearbox,is mounted on a special “G50” alloy pivot plate and is quite inconspicuous. The power is transmitted to the gearbox mainshaft via a reduction gear (400 RPM at crankshaft). A specially designed slip clutch is used to disconnect the starter motor when the engine is fired. The original kickstarter remains operational;
G46 rachet pinion needs an easy modification with a lathe. A 12 volt 12 amp/hour jelly battery fits into the original battery carrier.(Yuasa YTX 14BS), only a longer anchor stud and modified clamp strap are needed.  The extra weight to the machine is approximately three kilos.

No alteration to the crankcase is necessary. A slot must be machined into the kickstart cover. This modification is reversible. Should you wish to return to the original design, weld a piece of alloy to fill in the machined slot. The conversion is delivered as a kit including all the necessary parts exept the battery which is available from any modern bike shop.The kickstart cover and rachet pinion may be sent to the address below and will be returned ‘ready to fit’ with all the parts.The assembly can be done by any good Vincent enthusiast mechanic in a standard workshop.

Price :    1400 Euros the complete kit with a second hand checked starter motor,
                             available for positive earthed machine only.
              1500 Euros the same complete kit with a brand new starter motor,
                            available for any positive or negative earthed machine.

               Prices do not include postage or shipping charges.   (please check on these prices as they were given to me in 2003..)

Contact: Francois Grosset, Le Pont Ricoul,
             35720 St Pierre de Plesguen,
             FAX: 33-299-73-94 17                 E-mail:

2.) Frances Grosset's Electric Starter Instructions:

Starter Requirements, important to read before fitting


 The fitting of an electric starter is not a cure to start a poorly maintained or badly tuned engine.
 Backfire is not allowed.
 Initially, retard the ignition timing for full retard to be no greater than 2 degrees BTDC, and ensure that the ADT return springs are full strength. This is critical. The return of the ATD to the retard stop must be firm.
During the development of the starter, various incorrect settings have been used to try to find out the failings of the system. These have shown that weak return springs and excess ignition advance at full retard have been the most probable cause of a backfire, because of this, the main gear on the drive train has sometimes lost a tooth. This can be seen as a fuse in the system, but it is an expensive fuse, and can be avoided by ensuring that the ignition system is set correctly.

 Two degrees of advance is enough to start the engine.
 Be sure that the primary drive is in good condition. During the starting cycle the primary chain force is on the lower half of the chain, so a good chain tensioner is needed. Replace chain and tensioner if they are found to be defective.  Also replace your final drive sprocket, G21, if it not in good condition. Bush, PD2, is something else to check whilst in this area.  Check the bushes of the kickstart and shaft rachet pinion, also.
 A YTX14BS (or larger) maintenance free battery is required and should be used.  The maintenance free type of battery has more starting power than a standard battery and 12 amp. hour is the minimum capacity battery that should be used to provide sufficient starter motor speed and prevent slow, erratic or uneven starter speed.

1/- Put the bike on the rear stand and secure it with pieces of wood or a jack under the swinging arm pivot.  For “D”s, temporarily fit a rear stand and secure the stand to the machine.  Remove the exhaust, FT 108 plate, kickstart G1 cover and G50 plate with its components and battery, battery platform and footrest hanger shaft.

2/- Unscrew the sprocket nut, G23. Remove the felt carrier, G22, and modify it by reducing the height by 5mm (0.20”).  Replace and check that the face is just below the crankcase face of the G50 plate.  It is also possible to reduce the height by compressing the G22 between two plates under a press, to achieve the same result.  This is preferred to cutting., or punch it against the G21 sprocket groove (see sketch1).Cut approx. 3mm(.11”) off the felt so that when in place into its cup it is just compressed by the G 50 plate.
3/- Read step 7/- first and fit the sprag clutch to G3 mainshaft. Clean the splines with a file if required and push the clutch assembly (ES10AS) over G3 (a piece of tube 3/4”x1” is helpfull to gently drive it) until it is possible to insert the circlip, ES V5, in place with the help of two small screwdrivers. Adjust if needed by cleaning the splines so that it seats in the right place.If necessary to remove it, use a puller or two big screwdrivers at the back of the large pinion.
When it is fitted correctly remove the sprag clutch assy and leave it untill step.7/-.

4/- Transfer the following parts from G50 to G50/ES2:
 -FT 41/4, kickstart spring G87/1 and G116
 -Bearing, G41, and pawl carrier,G40/1 and G61/1
 -Kickstart bush G 84: check that the flange of the bush is not over 1.5 mm (.059”) thick. Reduce it if necessary.The flange must not protude the kickstart quadrant groove.
 Fit  G50/ES2 to the engine, taking care to not push the engine studs, ET109’s, too far otherwise you will have to dismantle clutch and primary drive to push them back in place. Replace nuts G72 and 142, screws E121 (check that the heads of the screws are not protruding above the surface of the plate; if so, adjust or file), and push dowel ET163 in place.

 Use a lathe to reduce the thickness and diameter of the kickstart pinion and bush, and also the diameter of rachet (already done if sent with G1 cover to machine).  See sketch 4 on page 8.
 Push G83 kickstart shaft out of its G82 quadrant and push the longer one in.  Sometimes the quadrant must be ground on its external face (spring anchor face) to get 8mm  (0.32”) thickness of the teeth.  The measurement from the G50 plate to the outside face of the quadrant must be 4.1mm (.16”) maximum., or it will touch the inside face of the sprag gear.  See G82 on drawing, page 10, and grind where marked xxxxxx.  An angle disk grinder is useful  for this work.
 Fit G83AS in place, G87/1 kickstart return spring and spacer G86. Sometimes the quadrant contacts the G50/ES2 in the region of the boss around the adjacent stud before striking the return stop; This happens when a non-original quadrant is used and this can be solved by grinding a bit of this part to clear the alloy plate boss. If you renew the kickstart shaft bushes at the same time, be sure that they are well in line. To check it, screw the G1 cover in place and give more clearance in the bushes for it to work properly,use a reamer if required.
Try using the cup (G26) with the spring(G48), rachet pinion (G46) and sprag clutch fitted in place to be sure that when you use the kickstart , the rachet works properly during the return sequence, otherwise don’t fit the G26 cup or eventually reduce its outside edge thickness .You could also make a bigger groove in the G46 pinion for the edge of the G26 to go into it and get some more clearance.
  More about G46 pinion: Check carefully, when the assembly sprag, G46 and spring are in place, that the kickstart rachet works well. There are some different lengths of G4 final drive shaft (and if it is too long ,there is less space for the kickstart pinion movment), differents G3 mainshaft designs,and the shimming inside the gearbox adapted to each engine... If necessary, machine more the back of the kickstart rachet pinion, G46, and/or cut the spring so it doesn’t become coil bound. The face where the spring seats on the G46 must be very smooth and polished if the spring cup G26 is not used any more, to allow the spring G48 to rotate when changing through 1st, 2nd and 3rd gear.
If,in spite of these suggestions, there is no room enough to make the rachet work, there is an alternative using a wave washer so ask for it if necessary.

6/- Modify G49 with a saw blade and a file and put it in place, (see sketch 2, page 7.)

Because it has been fitted on mainshaft in step 3/-, it should fit easily.  Take care when pushing it over the mainshaft that the large pinion meshes well with the small pinion of the reduction gears. To do this, when the teeth are just touching, turn the large pinion anticlockwise and push the sprag clutch assy at the same time. The best method to check that the sprag assembly is right in place, is to use a piece of material or a drill, or anything else used as a gauge of 4.2mm  (0.16”)maximum) thickness between the G50 plate and the back of the large sprag gear to be sure that this large gear and the small reduction gear mesh correctly.
If necessary use wheel bearing shims, H17, under the circlip to obtain this dimension and only when perfectly located , install the circlip with the help of two small screwdrivers.
ALSO,if you have been curious to have a look into the sprag or if for any other reason ,check very well that the large gear oil seal is correctly located....its lip pushed inside,not over the rachet otherwise the lubricant won’t stay for long inside....which is not recommanded at all !

8/- Actuating arm assembly, G66AS:Grind 2mm(.08”)off of the front of the centralizing spring anchor (peg) to clear the outside diameter of the sprag clutch and check that this anchor doesn’t touch the sprag in any up and down movment.An angle grinder disc is useful for this ajustment.
Check inside your G1 kickstart cover that the actuating arm bush is not longer than its housing.The std mesurement from the cover face to the bush housing(machined or “as cast”)is 31.10mm(1,225”)deep.
Install the actuating arm so ajusted, the spring, G70, shortened per sketch 3 page 7,over its anchor and the two G71 helper springs.Check that the inside face of the actuating arm doesn’t foul against the outer face of the sprag clutch; if needeed mill or grind it until you get enough clearance(0.2mm,.008” is correct).Put the gearchange mechanism in place and adjust it as usual (refer to Richardson ,etc.)

9/- Insert the starter motor in place at the back of the G50/ES2 plate by rotating the sprag clutch large pinion anticlockwise to help the gear teeth to mesh,and tightn the 3 allen screws to fix it in place.  If the motor adaptor fouls against the casting boss of the lower stud, ET109,under the crankases, file the adaptor.

10/- Final fitment of the G1 cover: Check that the sprag assembly does not touch the machined area inside the cover by using some plasticine between these two parts. 0.3 mm (.012”) of clearance is a minimum. Grease the gearchange components. Use the nipple to pump and fill some good grease into the reduction gearbox. Remove the dowel, ET163, from FT109/1 spacer and insert it into the reduction gearbox cover. Put spacer FT 109 in place over the swing arm shaft and replace FT108 footrest support plate.  Fit gearchange pedal, indicator lever, kickstart, exhaust, etc.
11/- Unscrew the 5/16” nut from the upper stud of the FT5R rear left hand pivot bearing plate. Remove any rust and paint, apply some grease, fit the earth wire  ESW3 and tighten the nut. Direct the wire upwards (see sketch 5, page 9).

12/- Drill the plate of the battery platform to fit the relay bracket underneath with a countersunk screw, M5, or two rivets (see sketch 6, page 9).  Position the hole so that the bracket and relay will not interfer with anything.
Connect the relay wires:
 Heavy-cable to the battery phase (power*) terminal (big ESW2)
 Heavy-cable from the starter motor (big ESW1)
 Wire (any colour) to the starter button (to handlebar)
 Wire from the phase (power) of the electric circuit, after a switch.
Insert the relay into its bracket and at the same time.....
........Put the battery platform in place and install the longer anchor, ES32.
Position the recommended battery (maintenance free YTX14BS) , adjust the battery strap and the longer anchor to the battery carrier.
* “Phase” is the power terminal, i. e.: the one that does NOT go to earth.
Be sure of a good insulation of all the connections. Protect the wires and cables from any contact with a metallic part to avoid a short circuit or a fire.


 When cold, use the choke, and enrich petrol only if necessary.
Turn the twistgrip just to tighten the outer cable.
Don’t open the throttles too much.
Push the starter button.  At the first attempt to use the electric starter, don’t persit if you feel that the starter motor doesn’t turn the engine easily, and be sure that there is no friction anywhere (sprag against cover) and that the blade tensioner of your primary drive is not too deformed or bent at the tongues by the adjusting screw.  Because the starting load is applied on the lower run of the primary chain, this tensioner should be as flat as possible to avoid damage to the starter system. All the power can be lost because of this and can be the cause of a gear teeth breakage. Also, some people use too weak of a battery which is not recommanded because it also causes some shocks in the system.  A correctly and fully charged YUASA YTX 14BS, or larger capacity battery is definately needed to avoid any problems.

IMPORTANT NOTE : If you start a newly build engine for the first time, it would be best for the first attemps to disconnect the starter motor from the G50 plate, or only remove the starter motor gear ES5 and so adjust your engine tuning, carburattor and ignition to be sure that there is not any backfire and that the idle speed is high enough.
Only refit it when you are sure that all is right.
 Adjust the idle speed so that the engine starts without touching the throttle.
During tests, the valve lifter was not used, but you can use it to make it easier for the starter motor for the first few engine revolutions.
It’s preferable to stop the engine with the valve lifter and not with the switch.
If the engine doesn’t start after about 5 second check ignition, petrol, etc.

Backfires are felt at the kickstarter when the kickstart lever is not fully in the top stop position, and therefore not disengaged from the ratchet pinion, also when the engine is suddenly stopped due to the choke lever being opened before the engine is warm. These are things that are not usually noticed, but the electric starter system will get a strong shock that needs to be avoided. So, keep your mixture rich whilst warming up the engine, and hold the twistgrip open on a fast idle until the engine is warm.

Point to note: Incorrect setting on modern japanese big singles and twins, also Ducati Pantah engines equipped with similar sprag clutches has caused the sprag cage and bearing to fail.  So to avoid broken teeth in your starter system.................................................


Pump some good grease into the starter gear reductor box via the grease nipple at every oil change or once a year minimun.

Sprag cluch.
Every 5000km (3,107 miles)or once a year,
Dismantle it from the mainshaft, turn the large pinion anticlockwise and pull it at the same time. With two small hooks, pull the cam roller cage out of the races. Note its position. Grease the inner and outer races with the special synthetic grease (yellow) -not too much because if the roller cams stick together, that could cause a malfunction of the sprag clutch.
Remove the needle bearing and fill it with some good bearing grease.
Carefully refit the cam roller cage into the outer race and afterward the inner race by turning and pushing gently the large pinion.Take care at the end of this push, that the rachet does’t damage the oil seal lip.


 A car battery charger is forbidden for this type of battery (Yuasa YTX 14BS).  Use a special electronic motorbike charger (optimate or similar) that can be left connected and controls the battery voltage without any risk of overcharge. Allowing the battery to become discharged (long winter or switch left on) is detrimental  to the battery.
 A battery, not fully charged, makes the engine turn erratically and allows some shocks due to the engine not rotating smoothly.   This is detramental to the system.

A shear pin is fitted to lock the starter motor gear to its shaft.  If your engine has too many backfires, this pin will break so you will hear the starter motor turning when pushing the starter button but it won’t turn the engine.
If this happens, first check your engine tuning ajustments, and afterwards only, replace the pin as follows:Remove the 3 allen screws at the bottom of the G50 plate and take the motor off.  Pull the clip wire against the gear teeth and push the old pin parts (3 pieces)off with an appropriate punch.  Insert the new pin and push the clip over it.

      Don’t jump over any step of the instructions and understand what you are to do at each stage of the fitting.  If in doubt, ask somebody more experienced ,fax (33) 299 73 94 17 in France,or e.mail :

Special kickstart cover  G1/ES1
Special alloy pivot plate G50/ES2
Big reductor double gear  ES3
Small reductor double gear  ES4
Starter motor gear  ES5
Sprag large gear ES6
Rachet spacer ring ES7
Rachet plate  ES8
Rachet oil seal   ES9
Sprag clutch assembly  ES10/AS
Sprag cam cage ES11
Gear spindle ES12
Gearbox reductor cover  ES13
Sprag needle bearing  ES14
Starter motor assembly  ES20/AS
Motor adaptor   ES21
Motor ball bearing   ES23
Motor brushes (pair)  ES24
Starter motor   ES25
Starter solenoïd  ES26
Starter solenoïd bracket   ES27
Special felt carrier  ESG22
Longer battery rod anchor  ES32
Longer kickstart shaft ES33
Additional kickstart shaft spacer  ES34
Special actuating arm  ES66AS
Modified G70 centralizing spring  ESG70
Modified G49 lever stop  ESG49

Motor to relay cable   ESW1
Relay to battery cable   ESW2
Earth cable   ESW3
Starter button  ESW4

Sprag clutch screw ESV1 6 per
Gearbox cover screw ESV2 2 per
Gearbox cover & spindles screw ESV3 2 per
Starter motor assy screw ESV4 3 per
Sprag clutch circlip ESV5 1 per
Starter gear safety pin ESV6 1 per
Sprag clutch special grease ESV10

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