Piston hitting spark plug?

nick dildine /

I recently bought a tomos sprint that someone else had been working on. i believe it has the a55 engine, but it looks to have the a35/puch high compression head. i took the head off and there’s a little spot on the piston where it looks like it’s been hitting the plug. what spark plug should i be running? Any help appreciated!

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Re: Piston hitting spark plug?

I don't know what the stock plug is, but if your plug has a long reach, meaning the threads extend into the combustion chamber, that's bad.

Also, some aftermarket heads need an extra base gasket, or head gasket, or even some Dremel-ing in extreme cases.

Another thing, is rods "stretch" under high rpms. As metal expands, if you have the minimum amount of clearance when spinning it by hand, that can change when you're riding.

Not giving you definite answers to your problem, just giving you more to think about. Like, if you think it's good and you here some tapping or clanking, stop immediately.

Re: Piston hitting spark plug?

nick dildine /

you can hear it hitting when turning over by hand if that helps?

Re: Piston hitting spark plug?

Overpriced Parts /

I do know what the stock plug for a a55 is, its long thread br8es Resistor plug,

A55 engines require resistor plugs

That’s not a a35 head it’s a hi hi puch head,

The hi hi Puch head takes a short plug But hi hi head has too small of a combustion chamber, too high of a compression as well as less cooling capability you’ll destroy your engine using it so remove it immediately,

The hi hi head in this picture is 65c head not 50 cc so the 50 cc one is 50cc is even much smaller

Best bet is to put the old head on or sanded it down a little bit more compression first if you more compression

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Re: Piston hitting spark plug?

nick dildine /

i don’t have the stock head. the person before me did all the work, i’m just trying to figure out what everything is. so i’m thinking my best bet would be a stock head correct?

Re: Piston hitting spark plug?

> nick dildine Wrote:

> -------------------------------------------------------

> i don’t have the stock head. the person before me did all the work, i’m

> just trying to figure out what everything is. so i’m thinking my best

> bet would be a stock head correct?

Or just buy the short reach spark plug for $2 instead...

Re: Piston hitting spark plug?

I was expecting to see a picture of the piston with the evidence of the plug hitting or a picture of a plug with a mashed down side electrode. Having said that, my first thought was that someone used a screwdriver down the plug hole to help to find TDC.

Re: Piston hitting spark plug?

You need to run what ever the manufacturer of the after market head says to run. Its not stock anymore so stock plug does not apply to your motor.

Re: Piston hitting spark plug?

Overpriced Parts /

> nick dildine Wrote:

> -------------------------------------------------------

> i don’t have the stock head. the person before me did all the work, i’m

> just trying to figure out what everything is. so i’m thinking my best

> bet would be a stock head correct?

Yes and remember it has to to be resistor plug otherwise you’ll blow your ignition

Re: Piston hitting spark plug?

♣Slew Foot♣ /

Ngk 6hs. Idk but I think non resistor plugs are extinct.

Re: Piston hitting spark plug?

> ♣Slew Foot♣ Wrote:

> -------------------------------------------------------

> Ngk 6hs. Idk but I think non resistor plugs are extinct.

Non-resistors can still be had .

And , if you want to make a resistor plug into a non-resisitor plug , that's pretty easy to accomplish , too . ;)

The spark plug doesn't have to be a resistor type , but , there does have to be resistance somewhere in the line between the spark coil and the spark , if the system is designed for it . That resistance could be the HT wire , cap or plug .

Generally 5KΩ resistance is plenty .

Re: Piston hitting spark plug?

Overpriced Parts /

> ♣Slew Foot♣ Wrote:

> -------------------------------------------------------

> Ngk 6hs. Idk but I think non resistor plugs are extinct.

Did you see the plug box in the picture ? I got it only a month ago.

please don’t post information that is wrong! Resistor plugs is the normal nowadays

Re: Piston hitting spark plug?

Are you just hoping to argue with people?

He said "non resistor" plugs you dip. Which they are harder to find these days. What could he possibly be wrong about?

> Overpriced Parts Wrote:

> -------------------------------------------------------

> > ♣Slew Foot♣ Wrote:

>

> > -------------------------------------------------------

>

> > Ngk 6hs. Idk but I think non resistor plugs are extinct.

>

> Did you see the plug box in the picture ? I got it only a month ago.

>

> please don’t post information that is wrong! Resistor plugs is the

> e normal nowadays

Re: Piston hitting spark plug?

Leave the lights on so they can hang up right when you just get the ped runnin perfect.

Re: Piston hitting spark plug?

♣Slew Foot♣ /

Tomos have resistor caps.

2 resistors doesn't work. Fry's box or Condensor.

Re: Piston hitting spark plug?

Overpriced Parts /

> ♣Slew Foot♣ Wrote:

> -------------------------------------------------------

> Tomos have resistor caps.

>

> 2 resistors doesn't work. Fry's box or Condensor.

I give up! you guys know more about spark plugs then my Tomos a55 owners manual and my tomos a55 repair manual!

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Re: Piston hitting spark plug?

♣Slew Foot♣ /

Or equivalent a resistor cap with the Ngk 8 hs. But e10 gas needs a hotter plug. 6hs works great I've had squish band problems when shifting cylinders dropping the gaskets and using kits a6hs works in just about any moped.

Re: Piston hitting spark plug?

Dirty30 Dillon /

100% none of this has to do with the spark plug at all, so you're all just blowing hot air.

The marks on the piston are DEFINITELY from using a piston stop to disassemble. Smooth them and leave it.

Run an HS plug and continue riding.

Re: Piston hitting spark plug?

> Dirty30 Dillon Wrote:

> -------------------------------------------------------

> 100% none of this has to do with the spark plug at all, so you're all

> just blowing hot air.

>

> The marks on the piston are DEFINITELY from using a piston stop to

> disassemble. Smooth them and leave it.

>

> Run an HS plug and continue riding.

You know this to be fact exactly how ?

Re: Piston hitting spark plug?

Dirty30 Dillon /

> P D Wrote:

> -------------------------------------------------------

> > Dirty30 Dillon Wrote:

>

> > -------------------------------------------------------

>

> > 100% none of this has to do with the spark plug at all, so you're all

>

> > just blowing hot air.

>

> >

>

> > The marks on the piston are DEFINITELY from using a piston stop to

>

> > disassemble. Smooth them and leave it.

>

> >

>

> > Run an HS plug and continue riding.

>

> You know this to be fact exactly how ?

Power of deduction. I used the wrinkles in my brain.

If the plug wasn't mashed or stopping the motor from turning over, than it's not the plug.

Re: Piston hitting spark plug?

Ha . You may be right . But , stranger things have happened . ;)

Re: Piston hitting spark plug?

Dirty30 Dillon /

> P D Wrote:

> -------------------------------------------------------

> Ha . You may be right . But , stranger things have happened . ;)

True

Re: Piston hitting spark plug?

> Dirty30 Dillon Wrote:

> -------------------------------------------------------

> > P D Wrote:

>

> > -------------------------------------------------------

>

> > Ha . You may be right . But , stranger things have happened . ;)

>

> True

I've seen bikes that call for a short reach plug but a long reach will fit, once the piston mashes the plug gap closed a little bit. In those cases it's definitely the wrong plug, but it will fit and the motor will turn over with some difficulty at first before turning over fine.

Re: Piston hitting spark plug?

> Nick MBC Wrote:

> -------------------------------------------------------

>

> I've seen bikes that call for a short reach plug but a long reach will

> fit, once the piston mashes the plug gap closed a little bit. In those

> cases it's definitely the wrong plug, but it will fit and the motor will

> turn over with some difficulty at first before turning over fine.

My Simplex takes a short reach plug . I tried a protruded tip plug with the same reach and I could feel the piston 'tap' when turned by hand .

I never tried running it like that , so I don't know if it would have run or not .

Re: Piston hitting spark plug?

Dude said you can hear it hit when you turn over by hand.

OP: what plug is in there now? Likely the Tomos long reach. Pull the head and see how far the plug is sticking into the chamber and how the tab looks at the tip. Did it get smashed and close your gap up? You can likely just get the short reach plug that fits that Puch head and call it a day.

Don’t know what hydra is talking about since there are no pics to “deduce” from.

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