Mods To 2T Motors To Make Starting Easier

[bigbird2]

In my search for easy starting 2t trials bikes some have suggested motor mods to ease kick starting.

The items that have come up so far are lowering compression and/or adding a compression release for starting (like was used in the 70s as a brake assist) by adding another hole (like a spark plug hole) in the head? Is this even possible with water cooled motors?

Does anyone have any knowledge or experience with these mods? OR any other ideas?

I'm interested in anything but wondered about the "optimum" compression ratio to get a good balance between starting ease and maintain sufficient power? And/or ideas on how low one can go without really messing up the motor performance?

Also pros and cons of just adding to base gasket thickness VS removing metal from the dome of the combustion chamber in the head (to avoid messing up the "squish" area around the perimeter of the pistion/head?

Also does anybody know of a trials bike that one could add an e-start from a related enduro motor to?

THANKS for any help!

[feetupfun]

I do know that there is usually no place to fit a compression release on modern water cooled two stroke motors because the coolant space encircles the spark plug. I suppose it could be dome with a lot of machining and welding.

An old trick you might consider (but feasibility depends on the design of the cylinder casting) is drilling a small hole from the top side of the exhaust port and through the top end of the cylinder wall. If the hole size is chosen well, it will make it easier to kick over but make negligible difference to the way it runs.

Another option is the Beta Alp (4 stroke 200cc Suzuki motor) which is electric start, but not really a competition trials bike

[mattylad]

longer kick start for less effort

Buy a bicycle?

[motovita]

I have seen a compression release added to a Gas Gas head. the coolant passage was sealed by O rings. I don't recommend it.

Shimming the cylinder up not only increases the combustion chamber volume but raises the exhaust port as well, further lowering combustion chamber pressure. It also changes port timing and will alter the way the engine runs. It is easily reversible though. I would recommend a 1mm shim if you decide to try it, I have a Gas Gas Pampera that came with a 1mm aluminum spacer under the cylinder.

What this world really needs is an electric start Trials bike for gimpy riders like me. The weight and size of modern batteries and starter motors is negligible.

Edited October 23, 2013 by motovita

[t-shock 250]

I found retarding the timing made my 05 sherco easier to start.

[0007]

Maybe a couple of things, retard the timing and add a base gasket

If you don't like it you can back up a step, try the timing first

I wouldn't be drilling into the cylinder

[tltel]

Hi Bigbird2, Just thought I would add my opinion, I have an old GasGas 350 and ride it regularly in competition, two to three times a month most of this year, It is so reliable and will always start first kick, hot or cold. (unless it's been upside down) When I bought it about three years ago it had a broken kickstart.

I fitted a new kicker and found it was almost impossible for me to kick normally without getting a massive kick back.

I fitted an extra base gasket, I think it was two 1mm ones but it was a while ago so can't be sure which raised the squish clearance just above the recommended clearance. It still runs fine and pulls like a train and starts brilliant. I know it alters the port timing a bit but there is so much power that I couldn't notice any difference, it did however make it smoother.

When I start it I always use my body weight, kind of stand on the kicker and thrust down and it doesn't kick back.

Three years on and the kickstart lever still looks like new and I have lost count of the times people have come up to me at a Trial and said, " I used to have one of those, kept breaking kickstarts"

hope this is of some help.

TLTEL

[dadof2]

Do you mean easier to start or lowering the force needed on the kickstart?

[lineaway]

If you were interested in easy starting why a 300 at sea level? The only reason to have a big bore is at high altitude!

[zerorev3rev4]

Scorpa 125 4t could be converted to electric start

[bigbird2]

THANKS for all the good input! I JUST bought a 2007 Beta 270! So now I'll be embarking on making it easier to kick.

I will definitely retard the timing - one guy I talked to suggested 5 degrees - does anyone have other advice?

I will also either add base gasket(s) or try to make a head spacer.

IF I do the head spacer out of say 2mm aluminum - would I want to have a normal head gasket on each side of it?

Adrian at Lewisport told me they had added head spacers to Gas Gas big 2t bikes of 1mm to 3mm with success.

Although getting it to tuck in might be a problem - the idea of lengthening the kick starter seems like it would help too?

If anyone has more ideas/input it will be appreciated. I'll report back after I've tried some stuff.

[beef706]

Congrats on the Beta, I am the proud owner of an '04, and I love mine. I have had a hard time adjusting to the LH kick though. As the posesser of 2 gimpy knees, I have to angle the bike just right and kick backwards and down to get her going. I will follow your progress on this with interest, as this bike has plnty of oomph for me even at altitude, and I would consider some easy starting mods myself.