08 suzuki rm 125 squish help

My figures say it should be about .030" on the outer edge of the piston and then have about a 5 degree increase in incline towards the spark plug hole for your flat to piston.
Remember that all squish is , is a place where the fuel mixture is cooler and thus burns slower so as to not develop the pitting around the edge of the piston. Now I don't know what the OEM spec's were for the squish in your engine, but these figures come from a 2 stroke tuning guide. It will require a good 93 octane fuel mix, but not race gas.

Paw Paw

I've found using a soft solder wire to be the best way. You will want to remove the head, then bend the wire through the spark plug hole and ensure it comfortably reaches the edge of the cylinder head. Then reassemble, gently turn the engine over (works better if you turn the engine on the flywheel nut, a lot smoother than using the kick starter) with the wire in place and measure the tip.

As you are in the UK I would recommend Tesco/Esso Super Unleaded 98 octane, I've ran that for years with 0 issues. Shell premium is also good.

A cheap way to make small changes to the squish measurement is via the base gasket.
I bought several from Athena (http://www.athenaparts.com/eng/models/view/4115-section-33/suzuki-rm-125) when doing my RM250. Actually surprisingly cheap and quick postage.

It is worth researching what raising/lowering the barrel will do to your bike before doing this though as it may not be what you are looking for power wise.

I'm not sure to be honest, I got given a piece by a friend. I will find out for you.

As long as it is soft and easy to compress then it should work fine. 1.6mm will be perfect as you will be expecting a squish measurement of anywhere from 1-1.5mm

Are your pistons cracking skirts? Scuffing? Are you outright seizing them?

You could be running it a hair lean, reducing the overall life. You could have an air leak causing more air into the mixture, again running lean.

What oil are you running?

Generally speaking you can not get away with pump gas in a 125 with an aftermarket ignition. There's too much advance in the mapping and you'll get the detonation you're seeing. If I were you I'd contact the company that makes the ignition you have and ask them to verify.

I would venture to say the at .039" you are allowing too much hot burning fuel to get to the edge of the piston and thus it is over heating. Remember that the squish design of your engine is to keep the hot burnt gases away from the edge of the piston at .030" and with the squish being almost 1/3 higher that could cause the issue. Also if the angle towards the spark plug is too shallow and if the squish band does not total about 1/2 if the piston top surface, these too can add to the issue at hand.

Paw Paw

I'm from the uk and have 2 rm 125's one of which is highly tuned and runs a vhm head and runs well on pump gas! It's around 37/38 Hp at the wheel. Justin at Gibbs performance built that engine for me and I can't fault it! I've also heard good things about Roland at hardcore racing.

This Might Help You.

http://www.vitalmx.com/forums/Race-Shop,42/Rm-125-enduro-build,1296503


Engine mods actually came with the bike when I bought it, VHM Head( used a thicker basegasket to set the squish to 1mm, to prevent detonation), Vforce Reedcage, Procircuit exhaust(makes a little more overrev), jetting.

Piston change every 20 hours, Pistonring 10 hours, crank bearings and rod 50 hours..

Be sure to change these items to prevent damaging more geardogs:
25355-37F00, 09440-04003 x2, 09209-05023 x2, 25323-34201, 25324-34201.
These were the parts I changed when i replaced worn gears and a worn "Shaft, drive".. Bike is shifting 100% correctly and is super smooth.

Since you are doing a enduro build you should send away either your cylinder or your head so the bike gets more bottom end because what i´ve felt there is no power down low at all ( a shorter silencer should help a little bit with more "pop" out of the corners)

I think that if your looked on line you will find a downloadable copy of the "Two Stroke Tuners Hand book by Gorden Gennings" and it will help you a lot in understanding of these things and how to get to where you want to be.
The answer is not always adding more octane. Too much octane will hurt performance as it will burn too slow.
Also squish is explained in great detail.

Paw Paw

I've had a bunch of rm125s and that squish sounds reasonable and if you' are getting detonation I would bet it's fuel or jetting.

If you are getting blow by on the piston, maybe you need to hone the glaze of the cylinder to get the ring sealing better?

Don't forget, the rm125 runs that expensive spark plug because it's got quite an aggressive ignition.....run a regular plug at your peril.

1mm squish is fine for a 125.
The thing you may be overlooking is piston to bore clearance .
You need to get an engineering shop to check this.
Here's what i'm talking about.

https://www.youtube.com/watch?v=r7KaxX1lC78

Oh & here's how to check the squish

https://www.youtube.com/watch?v=NDnZk53AxA4

Hope this helps

You would be surprised.
I have known main dealers on the phone that dont have the equipment or understand the concept.

I don't think that is the correct plug. I ordered mine (2006 RM125 which I believe is exactly the same) from Rocky Mountain ATV using the OEM parts diagram, and this is what was on the order/delivered:

SPARK PLUG NGK, R6918B-8