2018 EC250 squish, jetting & pistons
 

Posted this on DBW (I?m Or-strayan, moite)

I rode the bike after Dave at Two Stroke Performance, Victoria, (twostrokeperformance.com.au) re-cut my head - power was noticeably up down low & spooge was greatly reduced. The bike was, however, running on a little.

Jetting - NEDW #3, 45p/175m, a/s 1.5.

Squish - was 2.31mm, now 1.35mm. With squish like that, no wonder she?s a spooge-machine!

Note to all ?18 EC250 owners - before you get your head sorted (use TSP, Dave & Jason are awesome) you will need to accurately measure your piston crown height by taking the barrel off the bike, or find a way to measure piston outside edge to piston crown while the barrel is in situ.

Why? There are confirmed reports of 2 different pistons in the marketplace, one with a crown height of 3.77mm & one with a crown height of @ 4.5mm. This obviously greatly affects compression & therefore (combined with an accurate squish reading) your tuner?s ability to set compression as per order.

I incorrectly assumed, as the bike hadn?t been apart, I had the lower crown piston - as another rider had the smaller piston installed from new.

This consequently gave Dave no chance of setting a reasonable compression ratio as he was going on an incorrect assumption. Stock is around 13.6/1 but with the incorrect crown height factored in, it was actually closer to mid-high 14?s; too high for my jetting. And, too high for my riding style, reasonable fuel consumption (was going to have to go 48p/180m ) & motor service life.

Currently waiting on a solution - either retrofit the smaller piston (preferred, as the head is set up for it) or have Dave re-shape (at no cost) to suit higher piston.

Option ?a? is preferable for obvious reasons.

I must say, this bike is so much fun to ride & easy to work on but has been an absolute shit to jet. Now we know why! My mates mostly ride GG300?s & no-one?s had these issues.

Also, there were a couple of ?Friday arvo build? niggles to be found when I pulled it down, too - pv arm lock nut, rhs cover, had backed out all the way down & while checking for air leaks, found the reed block bolts were not quite tight enough.

Hopefully, I am close to getting this fabulous motor to it?s potential. On the ride post-head cut, I was climbing rocky lines in 2nd that would usually need first. And that was with a lean condition!

It?s instructive that, being the pragmatic person I am, I have kept the faith (I?ve had moments when I wanted to ?fix? the bike with a hammer..) - because, as anyone who?s ridden an ?18 Gas Gas EC will happily tell you, the frame, suspension, handling, steering & balance are worth it!

Interesting, do they come with different crown heights from the factory? Isuppose you cant let a little thing like a supplier slown down the production line haha.

I am about to embark on the jetting crusade on my 300. I just got mine back after my teething problems too.

Did i read earlier that you had fitted a NGK BR8ES plug?

While my dealer was changing a dodgy set of head O rings they installed the same plug. I just noticed it while i was rerouting some cables and hoses.

Yep, BR8ES, gapped at 0.8mm.

Measure your squish, mate - if it?s 2mm+, get TSP to sort it for you.

Yep, I have already been in contact about it. However its only just on its second tank of fuel. Was thinking to get her properly run in before i send it off. I am blown away by the power it has now and i am pretty happy but i am not a 2 stroke tuning guru. I need to get someone involved who knows what they are doing with the tune. I am happy to do the spanner work, just need tuning help...

Lowering your squish clearance & reshaping the combustion bowl to keep your compression reasonable - which is what TSP will recommend for trail riding -, will improve fuel economy, reduce spooge caused by inefficient combustion, give you a boost low/mid & enable you to run lower octane fuel if you wish.

You cannot jet out these in-built inefficiencies - I know, I?ve tried!

However, if you?re happy with the power, economy, jetting & spooge just ride it.

Could the pistons be different between the models?? EC/XC/GP? Checked parts fiches?

On the first tank i believe the dealer mixed it at 45:1 and i am not sure what oil they used. It was a spooge fest. I mixed up a frsh batch of 98 ultimate and Maxima K2 Synthetic at 50:1 and the spooge reduction was immediate. Its a fraction of what it was.

I have been following TSP for a while now and i like the look of what they do. I will most likely get the head done in the next couple of months.

Following your thread closely.

Now that RB-Designs (USA) no longer does Gas Gas (or Beta) head mods, we'll have to find a trustworthy machinist.

We generally have 91 octane here in Arizona, so maintaining compression ratio by opening up the combustion chamber is important.

Fieds, if your bike is a GP it has a different head to my EC. We would all love to see how it?s shaped by S3! My barrel has the S3 logo stamped on, too.

Rick D - Dave at Two Stroke Performance has said with appropriate jetting, there?s no reason why my bike won?t run well on 91 octane fuel. I am lucky enough to have good 98 around the corner from my house, though..

I have no fear of 91-Octane with a loose squish.

Just after a squish band mod (which would also require opening up of the combustion chamber).

I don't know who to go with on that, now.