TM 125 Why 2 plug holes?

[crafty]

Hi

Sorry if this seems a stupid question but what is the purpose of 2 plug holes in the head?

Mine has a plug in each one although I understand that some people have a bolt in one.

Thanks

[Andrew L]

I think it was so you could run different plug heat ranges in each plug hole and change them easily out on the track , I may be wrong though.

[mick25]

The Yamaha ag bikes in nz 100cc & 175 cc of the seventies had the two plug heads I throught it was a spare if one played up while chasing sheep etc 

[John Orchard]

If I remember back to 1974 correctly, my TM had a long-reach and a short-reach plug hole?  I guess you have the option of different reach plugs, I ran an 8 in one and a 9 in the other.

[mick25]

If I remember back to 1974 correctly, my TM had a long-reach and a short-reach plug hole?  I guess you have the option of different reach plugs, I ran an 8 in one and a 9 in the other.

you have just shocked my memory back John , I think the yamaha had a short plug and long I think we used a old 149 or 186 hr Holden long plug for the farm bikes back then 

[mick25]

Hi

Sorry if this seems a stupid question but what is the purpose of 2 plug holes in the head?

Mine has a plug in each one although I understand that some people have a bolt in one.

Thanks

i would leave a spare plug in it , instead of a bolt because the compression may very some between the two , but depends on the bolt length to .

[brent j]

I seem to remember that the TM shares the same head as the TS. The thinking of the day was to have a second spare plug or one of a different heat range. The main problem was that second plug was getting covered and it wasn't burning it off. When you needed that spare it was worse than the one you were running

Use the centre plug hole and there should be a plug in the side one. The plug was fitted standard

[pokey]

Correct. it is for a different heat range plug not a spare nor reach.

Suzuki lists the plug suggestions to run for each model based on heat.

[brent j]

Yeah that figures Pokey I seem to remember my mate's TS125 had a short reach plug and it went in the left side, short reach plug hole
where the TM125 used the centre long reach plug hole

[pokey]

It all depends on which Suzuki manual you read.
In the TS185A manual it states

the second plug hole for decompression has been removed (TS185A has single plug).
in the TS/TC125 manual it states its for a cooler plug depending on the terrain.

 ive never seen a genuine decompression valve fitted to a suzuki 2T and only a few after market ones so i would go with the heat range of the plugs

i do have a list somewhere of the suggested spark plugs for each model from Suzuki but I cant track it down just now.

[80-85 husky]

bikes were sensitive to mean temp variations back then and it was there to provide a spare for a different heat ranges. I used to swap them over every soften to keep the spare clean!

[Iain Cameron]

Going back I always thought it was for when your plug loaded up and fouled you could just switch to the other one .Iain

[Slakewell]

So you can carry the head like a six pack?

[Lozza]

Hi

Sorry if this seems a stupid question but what is the purpose of 2 plug holes in the head?

Mine has a plug in each one although I understand that some people have a bolt in one.

Thanks

Basicaly at the time it seemed like a good idea (streakers excuse)

[Canam370]

Going back I always thought it was for when your plug loaded up and fouled you could just switch to the other one .Iain

That's the way i figured it too. Problem was that if you managed to foul the plug you were running on then the 'spare' was going to be fouled as well - probably before the other one failed because the electrode wasn't been burnt clean by a spark.