LocostUSA.com

By the way, motorcycle drive trains have lash in them, not because of having straight-cut gears, but rather because they are constant-mesh dog-engagement style transmissions. The straight-cut gear pairs are always in mesh, and slide back and forth on the shafts, with large tabs (dogs) on the sides of the gears sliding into engagement with mating dogs on the adjacent gear pairs. There are large clearances between the dogs, and that is where the lash/snatch originates from.


Is there any way to cushion the dogs to lessen the lash/snatch in the transmission?

Are you running any sort of cush drive?

Not that I know of, looking at a donut in the drive shaft, but not sure yet I want to hack up the drive shaft to fit one. I would like to lessen the bang, when going into first gear.

There should be no bang if the clutch is fully released and the idle speed is not too high.
More pedal travel allows for more finese by the driver to ease engagement.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

It's the typical clang going into first gear, I guess that everyone with BEC seems to experience.

It's true that that "CLANG!" is part of the BEC animal, but I've done 2 things that have helped lessen it.. First (and most importantly in my opinion) is to fab in a Giubo (aka 'rubber donut') into the BEC's driveshaft.. your bike transmission will thank you for this.. it will both help protect your bike tranny and greatly reduce that 1st-gear 'BANG!' that you'd otherwise get.. I originally built my Honda N600 BEC without a Giubo, and I hated it; hated that Bang!!-shifting so much that I tore the driveshaft out and fabbed in a much-needed Giubo- totally changed the driving experience, and I'd do it all over again

The other thing I've done is a little cheesy, but it works.. I've cut two strips of Dynamat (about 4" wide by 12" long each), and I've stuck them on the driveshaft (like rings) at 1/3 intervals the length of the shaft (essentially offering a sound deadener in two separate places on the shaft).. I then installed a few zip ties on each of them to make sure they don't come flying off at high rpms.. These light, unseen strips really help absorb/ eliminate that awful clang that BECs suffer from..

At very least the Dynamat strips are worth a try- easy to pull back off if you see (hear) no benefit.. Both of my last 2 BEC projects are running both a Giubo and Dynamat on the DS with great success

--ccrunner

_________________
Dean

1972 Honda N600 Restomod "ccrunner's N600 VFR800 repower"

1963 Volvo P1800 Restomod
http://locostusa.com/forums/viewtopic.php?f=36&t=16309

1959 Berkeley SE492 Restomod...
viewtopic.php?f=36&t=19397

"ccrunner's 1960 MGA coupe Restomod" found on MGExp.com

It's worth a try, did you have to grind down anything off the driveshaft, to fit the donut? Did you buy an off the shelf one and mod it for your motor?

The donut I used was just an off-the-shelf BMW/Saturn/Pontiac piece.. It's a hassle, but you'll need to make or have made an adaptor to go from your bike's output shaft, then the donut, then your driveshaft going toward the rear of the car (that is if you put the donut on the motor side)... If you want the donut on the rear end side, which may be easiest, then it's rear end mounting flange, custom adaptor (likely aluminum), donut, then driveshaft going forward. It's not that complex, but it must be done right and perfectly balanced as a unit; that donut/driveshaft are spinning right next to you the driver! (I put 3 separate DS hoops around my DS as I'm paranoid about having this thing grenade right next to me..

If it helps, a Saturn Sky/ Pontiac Solstice DS will have most of what you'll need (for the donut install), but you'll have to have it modded to fit your car of course.. In the above pic, most of the DS that you see was sourced from a Pontiac Solstice, just lengthened for my needs..

Fair warning, it's a bit of work and a hassle to fab in a Giubo, but in my experience, it's essential for a BEC

--ccrunner

_________________
Dean

1972 Honda N600 Restomod "ccrunner's N600 VFR800 repower"

1963 Volvo P1800 Restomod
http://locostusa.com/forums/viewtopic.php?f=36&t=16309

1959 Berkeley SE492 Restomod...
viewtopic.php?f=36&t=19397

"ccrunner's 1960 MGA coupe Restomod" found on MGExp.com

Thank you, Sir, good info

Well, I don't agree but the great thing about a good forum is we don't need to.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

No cush drive. Obviously you can induce oscillations with any manual car. The r1 will oscillate if you meet some conditions, but so will my c5 Vette.

True, but the consensus is that it's far more likely to happen in a BEC. I can invoke it in my mid-engine Seven, because first gear is good to 60mph, and has a light aluminum flywheel. A BEC has a long first gear as well, little or no flywheel, making it very easy to get into bucking even with an owner who expects it.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

No disagreement - its definitely easier to do in a bec.