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ET: Engine (Twin) Twin e-starter options?

peter holmes

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Francois Grossett fitted my starter a couple of years ago, and so far it has worked fine, but I run a pretty soft 998cc engine, Francois definitely does not recommend the use of the decompression lever, or any decompression device, I believe that Trevor Southwell developed the Grossett starter along with Francois, I think Trevor drifts onto this forum now and then, perhaps he could inform us why it is considered better not to decompress, since mine was fitted I have not used the decompressor and all is well, does gradually easing the decompressor of during starting predispose the engine to back fire, which we all know is considered fatal.
 

macvette

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VOC Member
Francois Grossett fitted my starter a couple of years ago, and so far it has worked fine, but I run a pretty soft 998cc engine, Francois definitely does not recommend the use of the decompression lever, or any decompression device, I believe that Trevor Southwell developed the Grossett starter along with Francois, I think Trevor drifts onto this forum now and then, perhaps he could inform us why it is considered better not to decompress, since mine was fitted I have not used the decompressor and all is well, does gradually easing the decompressor of during starting predispose the engine to back fire, which we all know is considered fatal.
I had a 1600 cc 1999 Yamaha Roadstar carburettor model, it had solenoid operated decompression and currently own a 1990 Honda GB 500TT which has an automatic mechanically operated decompression acting on the OHC.
It seems these companies have no problems using decompression with electric start so maybe its the timing of the release of the manual decompressor which causes the problem.
 

Comet Rider

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A friend in my section has a Shadow on 8.5:1 pistons c/w Grosset starter and uses the HD style automatic decompressors all the time, and has had no problems to date,
 

greg brillus

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When discussing this topic with Ken Horner he and I both agreed that the less number of cylinders on an engine the harder it is for an electric starter........But a big "V" twin is particularly bad because the power pulses are close together and this makes the engine similar to a giant single. By opening the throttle you instantly increase the volumetric efficiency of the engine, so this makes cranking very difficult.........Mac has made the most valid of points that most makes of modern bike engines do in fact use some form of decompressor in their valve train, usually some centrifugal weighted device that throws out upon engine start to regain full compression on that cylinder. The large capacity Harley/ S&S engines use a solenoid in the head.........On Terry's newer top end kits they have prevision for one of these solenoid valves to screw into a 12 mm thread with a tiny hole that passes through into the combustion chamber between the two valve seats......This seems to work quite well, i installed one of these kits on a Comet a couple of years back, and chose to use a horn button on the left side handle bar as a compression release........It worked very well for turning the engine just over TDC for starting, although it wan't quite big enough to effectively stop the engine like a stock valve lifter, but it had coil ignition anyway so that needed to be switched off to kill the engine.
 

Oldhaven

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Greg,
Just curious as I will be using a HD solenoid CR on my TPV top end Comet project. Do you recall if the bike would kick start and run while continuing to hold down the button rather than just using it to get over compression? I would like to use the CR in a similar way as the valve lifter lever. Of course if I just got my act together and finished it I would already know this...

It worked very well for turning the engine just over TDC for starting, although it wan't quite big enough to effectively stop the engine like a stock valve lifter, but it had coil ignition anyway so that needed to be switched off to kill the engine.

This question does have some relevance to e-start. I have a chain saw with a push button CR and after it starts it will continue happily running at low compression until I rev it and the CR closes. I would think that this way of not completely decompressing the cylinder, effectively lowering the compression ratio by a small leak, would make it easy on the starter system by not releasing the solenoid button until after a start.
 
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Bill Thomas

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VOC Member
We fitted a 14mm thingy to Ron's Comet, You just push it open and Kick, It's like we left the piston out !.
Ron didn't get on with it at first, But that was with a Mag' , That we think was not good,
After we fitted a "D" Distributor it was fine.
 

Glenliman

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VOC Member
Greg's description of the backlash makes me glad I went thru the effort to fit the Newby belt drive and rear wheel cush drive. I wasn't thinking about e start and backlash at the time, so it's luck rather than good management.
Another type of compression release, one that may not have been mentioned yet, is the type used on the 490 Maico MXer. This engine is at 12 to one CR and very difficult to kick over without the compression release. The compression release is a manual type, but does not release all of the compression.
It effectively reduces the 12 to one to about 8 to one for starting.
The engine starts nicely on 8 to one and then you release the lever to get going. Really get going!
I wonder if this type could be used on a big bore hi compression Vincent engine to reduce load on the estart? Or to negate the need for estart. This would really appeal to me as I really don't want to add the complexity and weight of an estart to the bike.
Would the bike still start easily with some of the charge bled off? Probably only one way to find out!

On edit- I see now that Oldhavens chain saw has a similar compression release, but automatic rather than manual.

Glen
 
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greg brillus

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The solenoids that David posted a picture of above are the exact ones to use, only you need to make up a simple banjo arrangement to move the gases away from the cylinder head.........I don't really see the gases as being an issue, but it can make a slight mess of either fuel or oily residue coming from the valve assembly. Indeed the Royal Enfield cable operated ones that Tim and I know and have used, can tend to do this as well. To answer Gene's question, No sorry I don't remember trying to start the engine holding the decompressor in whilst cranking the engine..........I feel this would tend to work where an electric starter is involved.........Generally once you get the piston just over TDC then a good kick will start the engine no problem. Of course if you are using a Norton AMC gearbox you generally need to turn the engine more past TDC for a good start on the kickstart lever on account of the different kick/crank ratio within the gearbox. The fear factor of using the stock valve lifter on a twin with an electric start is minimal in reality verses the strain on the starter..........It seems obvious that reducing the compression load will definitely help the engine/starter combination even if the reduction in compression is only a partial amount.
 

stu spalding

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VOC Member
The fear factor of using the stock valve lifter on a twin with an electric start is minimal in reality verses the strain on the starter.
It also helps if a lithium iron battery is being used as these batteries need "waking up" a bit before applying full load. Switching the headlight on is the usual ploy but if an LED headlight is fitted spinning the motor over with no compression does the job. Cheers, Stu.
 

Dave61

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VOC Member
A friend in my section has a Shadow on 8.5:1 pistons c/w Grosset starter and uses the HD style automatic decompressors all the time, and has had no problems to date,
I'm fitting my Grosset starter & like the idea of these Automatic Decompressors, but wondered about only using the ignition to stop the engine running or do you leave the existing set up in place.
Vibrac did post about backfiring when just turning the ignition on & I'm sure someone mentioned the engine can spin backwards if you just turn it off on the switch.
Don't want to break it prematurely, believe me, if it can go wrong expensively when I'm doing it it will ! :)
Cheers
Dave
 

Oldhaven

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VOC Member
Here is a picture of the solenoid installed and of the small hole in the combustion chamber. I suppose it would be possible to “tune” the starting compression for easier starting by fitting a metering jet in this small hole. The location does make removal of the UFM and head brackets necessary for servicing or cleaning the device and I will have to machine a clearance recess in my aluminum head bracket, since it has a flat bottom. Looking again at the pictures I can see that Greg’s advice about a banjo fitting would be possible. I believe the HD’s run this off the starter circuit and vent the gases internally into the exhaust.

 
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greg brillus

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On the 600 Comet I did a year or so back I just used a small horn type button on the bars to operate the solenoid whilst turning the engine just over TDC.........With the AMC type Norton box you needed to turn the engine more than past TDC for a one kick start. No big effort needed and start readily with a good carb and ignition. The 600's go really well when set up correctly, they make for a fun ride.
 

Comet Rider

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VOC Member
I'm fitting my Grosset starter & like the idea of these Automatic Decompressors, but wondered about only using the ignition to stop the engine running or do you leave the existing set up in place.
Vibrac did post about backfiring when just turning the ignition on & I'm sure someone mentioned the engine can spin backwards if you just turn it off on the switch.
Don't want to break it prematurely, believe me, if it can go wrong expensively when I'm doing it it will ! :)
Cheers
Dave
Hi Dave,
He has a BT-H on his bike, so uses the ignition kill button.
The beauty of the automatic de-compressors is that you push the button down, and when the bike fires the pop closed. It's much easier to buy the 10mm ones, as they are used by both HD and many chainsaw makers. The 14mm ones are very expensive,.

Neil
 

Bill Thomas

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The Bloke who sold me the Expensive 14 mm ones :D , Told me the cheap chainsaw ones can fall apart !!,
 

Little Honda

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VOC Member
After re-reading all of this Ive decided, for now, to continue overeating and doing lots of leg curls on the home gym.

Glen
I did several 100 miles testriding of Ernst Hegeler´s home made Norvin with his own home made engine. He
does not make bigger engines, than 1000cc. You can find his starter system pictures within this subject. The
problem of his solution is the price. Interested ones do not value, that his starter is in the place of the original
dynamo, so causing the purchase of his dynamo/ignition solution as well. His dynamo delivers safe 150W in
place of the original magneto, being gear driven and having an electronic ignition in place of the original
ATD by 2 wearfree pick-ups, feeding a black box for both single or double ignition.
Starting goes easy by pulling the decompression lever, when pressing the starter button, keeping the lever
pulled app. 2 seconds, until the engine winds at a continuous sound, then releasing the valve lifter and continue starting. The engine starts immediatly after closing the valve lifter with the throttle untouched all the time.
The system operates dead reliably, the engine starts every time like any car engine. The starter motor used
is a Volkswagen manufactured starter which can be bought world-wide at low prices from any Volkswagen
dealer. The only problem is, you have to order according to Volkswagen business terms, ie. delivering an
identity number of the car, the order is related to.
Regarding the fact, that the Hegeler solution is a complete unit for starter, ignition and dynamo, it is not
expensive at all. It is simply the best in reliability, but not separable into its single parts: ignition, starting and
generating Voltage, it´s a unit.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I'm fitting my Grosset starter & like the idea of these Automatic Decompressors, but wondered about only using the ignition to stop the engine running or do you leave the existing set up in place.
Vibrac did post about backfiring when just turning the ignition on & I'm sure someone mentioned the engine can spin backwards if you just turn it off on the switch.
Don't want to break it prematurely, believe me, if it can go wrong expensively when I'm doing it it will ! :)
Cheers
Dave
My own experience of fitting, using and thoughts about the Grosset electric start on a Rapide:-
  1. It is not a big deal for an average home mechanic to fit the Grosset starter. Most of it is disassembly and reassembly with new parts in the kit. The only modification that needs some machining is the part of the kickstart ratchet mechanism. There are pictures of two suggested way of doing this in the instructions. The kick start quadrant needs thining a little and this can be done with an angle grinder or a bench grinder. The gear cover modifications can be done with a hacksaw and file to make the cutout for the narrow transfer gearbox and a sander to relieve the inside of the gear cover to create a bit of extra clearance. The battery platform may need a mod to accommodate whatever battery you decide to use. The starter solenoid fits nicely out of the way under the battery platform.
  2. My engine as I have already mentioned elsewhere has 8:1 pistons and Mk 1 cams. The battery is a Lithium Shorai. The starter turns my engine over without using the valve lifter. If for whatever reason the battery was getting low I see no reason not to use the valve lifter to get the engine spinning first before dropping the lifter lever. Before I fitted the electric start I always held the valve lifter in and released it near the bottom of the swing so the spinning flywheel momentum did the work of getting over the compression. It almost always started first or second kick. I can never understand why people spend time listening to the inlet suck to find the long gap between compressions position and then ease it over compression, at least not on a fairly standard motor. (That might provoke a little feedback in this thread.)
  3. Regarding the reluctance of some people to use the original valve lifter equipment due to perceived fragility. Mine has been OK, not fallen to pieces or lost one of the little needle rollers and it has done tens of thousands of miles in my hands. How many people actually have personal experience of the standard valve lifter mechanism failing if it has been assembled correctly? (Do we need a poll?)
  4. Stopping the engine. The sprag clutch doesn't like attempts to make it go backwards as happens if the crankshaft turns backwards. (François stresses the importance of correct ignition timing so there is no chance of a backfire. I use a modern BT-H magneto, auto advance and never once had a backfire when starting. Maybe people with manual magnetos might be most likely to have this problem if they don't have the adv/retard lever in the right place?) If you use the valve lifter to stop the engine then there should be no chance of the crankshaft going backwards as there is no compression that a piston might bounce back from and as there is no compression there should not be any chance of a backfire. If you use a kill button there should be no spark so no chance of a backfire. There is still some compression so there is a chance that a piston coming up to TDC on the compression stroke could bounce backwards. I don't know how much force this would have or how much strain it would put the sprag clutch under. My guess is probably similar or less than the strain experienced when the engine is started without using a valve lifter.
Well, that may have given you something to think about or at least some targets so you can shoot me down in flames.:cool:
P.S. My right knee likes the electric start and I have (bravely\foolishly?) removed the kickstart.
 

greg brillus

Well Known and Active Website User
VOC Member
All good stuff Eddie.......Yes i have found little in the way of issues with the Grosset starter with stock or near stock engines........It is the larger capacity, or more highly modified engines where the trouble starts.........I think a few on here mentioned about the TP squish band heads causing possible grief as the compression characteristics seem to be more adverse than the stock Hemi heads.........I started up this 600 Norvin I built a couple of years back today, and it definitely has some serious punch to the exhaust note........ From memory it runs a Mk 2 cam and 36 mm Mikuni carb, but everything else is quite normal.........(Normal......that's not a Vincent word is it........???.......)......... ;).
 

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