How to get better acceleration??

Does anyone know a good way to get greater acceleration...such as leaving a stop sign from a complete stop,and going faster at the start?

Re: How to get better acceleration??

Ben Hunter /

I adjusted my timing and got alot better accleration

Re: How to get better acceleration??

I forgot to mention it is a Tomos Targa LX 2000

Re: How to get better acceleration??

what timing>>>>>

Re: How to get better acceleration??

what do u mean by that ?

Re: How to get better acceleration??

I'm going to suggest you shave some off the head and hope Fred comments on whether I'm an idiot for suggesting it or not. I believe I am getting a slight increase in acceleration from shaving .020" off the head.

Re: How to get better acceleration??

soo i just shave the rounded off part off of the head

Re: How to get better acceleration??

Fred Melonhead /

Assuming there isn't anything WRONG with the ped .. (clogged carb or previous bore seizure?)

Then ...

I suppose the easiest way for more acceleration is a smaller front sprocket.

But most people aren't willing to give up the top speed they lose by doing that.

So ... shaving the head is probably a fairly easy way for a little more 'punch' off the bottom .. (and everywhere actually)

But most people don't know how or where to get it done .. (call an auto parts place that advertises .. 'machine work'.

Take the head to them and aks them if they can take .020" off .. and how much ?... (maybe $20 to $40)

However ... small 50cc motors like these aren't really ever going to be REAL strong off the bottom .. most have to get going 10mph or so before they start pulling better.

Re: How to get better acceleration??

Fred Melonhead /

You take it to a machine shop and have them take .020" off the side of the head that in next to the piston.

Re: How to get better acceleration??

The local machine shop is charging me $20.00 to shave a head. The machine shop's primary service is grinding and reseating valves on auto engine heads. I get same day service. I believe I am getting 1 mph per .010" shaved. However, I had the Peugeot head shaved .030" and am now having a few issues with the engine. .030" may be too much.


Fred Melonhead /

What kind of issues ?

Done right .. .030" isn't too much at all for these kinds of motors.

If its a 'running problem' .. you either need a colder spark plug or higher octane ..

.. or if its a mechanical prob (lack of clearance) .. then you need to have the edge of the combustion chamber relieved on a lathe to match the piston contour.

If its a compression sealing problem .. you need to 'lap' BOTH the cylinder and head sealing surfaces on a surface plate.

Re: issues

Wow, That's some good info Fred. I refered to "issues" because I'm not sure what is going on. The symtom is, will not idle when the engine is hot. The ped is a '80 Peugeot 103 with 70cc kit, 15 mm carb, stock intake, and .030" shaved off the head. The outside temperture has been mid 40's everytime I have ridden the ped. The ped runs great at all speeds. After riding twenty minutes or so I can't let the ped go to an idle. If I do it dies. I have learned that if I hold a slight choke the engine will idle, however, when I begin to accelerate to ped has no power for a few seconds. Then it takes off and runs great again... until I try to idle. My guess is it could have something to do with the amount I have shaved off the head, or the outside temperature, or it isn't getting enough fuel at idle (with engine hot). Does any of this make sense?

Re: issues

Fred Melonhead /

The problem is only at idle ?

... I think its just carburetion.

If it was a Jap carb with changeable pilot jets .. you would just try a richer pilot and see what happens.

Or .. if yours has a idle mixture screw .. you should richen that up and try it.

If plug chops on the top look good .. the compression increase isn't the prob.

Re: issues

The problem is only at idle with the engine hot from running hard. On a cold start the idle is set to a nice rpmk. The ped idles great until I run it long and hard. The plug chops look good. The carb is a Dellorto. Could it be the stock intake isn't allowing enough fuel and a larger intake would. I can improve the problem by holding the choke in 1/4 to 1/3. My logic is, it isn't getting enough fuel so holding the choke restricts the air and causes a mixture that can idle. Hell, I can keep the problem from occuring by never slowing down, run the hell out of it, full throttle, balls to the wall... LOL Maybe I should just keep riding it that way!!!!. Seriously, I'm considering replacing the intake. Do you think a larger intake would have aby effect. Is my "logic" illogical?

Re: issues

Fred Melonhead /

sooo ... you don't have a changeable pilot jet ?

.. and... you have tried adjusting the idle mixture screw ?

I think if its too lean with one intake tube .. it'll be too lean with another intake tube.

Re: issues

Freeman Montgomery /

I know We're Talking Tomos' her, but I just got some info from a Cosmo/Avanti mechanic about the bogfrom dead stop problem most seem to suffer from. The washer in the cluch pack in the tranny is also a shim. I you have a machine shop shave it down a little. It changes the point the clutch pack 'grabs' and also changes the the shift point for the tranny. If you're planning on fixing up your bike for more top end, this would be very helpful. If you increase the rpm point where you are making max power, and where you start making power, say from a better pipe, bigger carb, port work, ect... this would be VERY helpful.

Re: issues

The main jet is changable. If I increase the idle screw then it idles too high under "normal" conditions. I was thinking that a larger intake tube would allow more fuel to move to the cylinder. I think you are suggesting that a larger main jet would allow more fuel into the intake at idle. If that is what you are suggesting, it makes sense. I understand that the main jet limits the maximum amount of fuel, but at an idle a larger jet would also allow more fuel.

Re: issues

Fred Melonhead /

Well no ... I asked if you had a changeable PILOT jet ... Jap carbs have pilot jets that affect the carburetion at idle speeds.

(aside from the main jet).

So you can tune the idle mixture independantly.

So .. I will assume you don't have one.

.. and .. is your 'idle screw' a MIXTURE screw ? ... or ajust an idle SPEED screw ?

and ... whatever that screw is .. CAN you adjust it to idle while hot ? .. (aside from what it does to the idle while cold)


and I wasn't referring to the main jet.

I am not saying a richer main will help your idle (though it will) .. but then the top end will be off.

I am not really going to be able to help you if your carb has none of these 'fine-tuning' features.

(aside from possibly changing ignition timing)

orrrrr .. if it is a slide carb .. you could possibly buy a richer 'cutaway' slide (if they make them) .. or if they don't .. machine the bottom of the slide off a little (draws more vacuum at idle and richens the idle misture).

All hard for me to say without seeing it.

Re: issues

I'm learning all the time Fred!!! I appreciate your input. I was not familiar with the term "pilot jet." I will remove the carb and determine what I actually have. I believe it only has an idle speed screw. I will see if I can adjust the idle screw when hot to get an idle. The timing is right on.

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