S3 Race 250 Port Matched Cylinder and Head

[shawbagga]

Just another update on the sexy beast!

As most are aware my TTX shock had a 'failure' and has been repaired and revalved by Ohlins USA. I will have it back early next week/late this week and will post an update in its respective thread once getting a ride on it.

The engine is still running strong with loads of compression under foot. The jetting specs of 40 N3CW#3 178 have been running fine with very snappy power and good grunt down low. I feel it might still be a bit lean in the middle as it kind of buzzes up sound wise without as much pull just before it comes on song and then hits super hard. I like it but I have gone a half a clip richer on the needle and dropped a size on the main to see if I can get a bit more torque in the middle where theres a little hole. I've switched between a 175/178 main several times now and both respond well. The 175 feels a bit crisper and I can get a bit more overev out of it so will stick with it for a while.

I need to check the hour meter to be certain but I believe I've got around 60hours on the top end now and moving towards 250hrs total on the bottom end. I have a new piston kit and gaskets ready to roll but not sure if I should try and stretch another top end out of her or pull it down for a complete rebuild. Thats new terriroty for me and I'll need some of the advice of others here to get through that job for sure. Any opinions?

The TTX forks are also due for a service and I'll likely do that when the top end comes down. I'll regrease the headstem at the same time.

I've only attached one pic today. Hard to believe I could put any power to the ground with the old tyre! Sure think the new one will make a small difference this weekend!

mate you need to hang the rear end out a bit more to even up ya tyre wear!

 

[Jakobi]

I think you should be OK if you kept a clean filter in it, just check the rod big end side clearance. Actually 60 hrs isn't a lot for a top end, I've been going 85 - 100 hrs and things are still fine.

I'm going to build my '07 into my first ever GG300. Head mod and I'll play with the Suzuki needles as I wan't smooth on this one. KYB forks will eventually go on too. This will be my hell trail bike, my '12 250R my race bike.

Thanks Glenn. I always went around 85hrs on the 300 top end and the pistons always came out well within spec. Air filter is always clean.

mate you need to hang the rear end out a bit more to even up ya tyre wear!

You know I haven't got any mad drift master skills.

 

[nambo-trev]

I've just ordered the same S3 conversion, going to turn the nambo into a 250!

 

[GMP]

I thought you were a die hard 300 guy Trevor?

I picked up a 300 top end to try on my '07, but that is not my race bike now and will be used for hell trail duty.

Its funny, but my '12 cylinder is marked with an "S3" in ink on the gasket surface, nothing in the casting. The ports are very smooth though and the bike has very good top end. I wonder if there is anything too this?

 

[nambo-trev]

You know Glenn I've had a lot of seat time on the 2 strokes over the last 3 years and what initially brought me over was riding my buddy's 250. Last year I had to ride a buddies new 250 up a few hills for him and was like "wow" this is so easy to climb with even with my 300. I also find as I've become a Better rider and am riding with expert and pro level riders I'm understanding that its not all about power. The 250s I've rode lug just fine and climb great but the BIG difference to me is the fitness part. These guys ride on a totally different level and a 4-5 hour ride chasing them I need to keep as much of my energy as I can I feel like the 250 helps me with that. The 300 gets very exhausting on big hills and tight single track from all that power pulling on me. I tried to fight it thinking the 300 was the weapon of choice but for me in order to reach that next level I feel a different weapon is required. I guess time will tell and hey if it doesn't work out the way I wanted someone here will get a great deal on a s3 cylinder kit!

 

[GMP]

Now you get the point of less is more, welcome to the club.

 

[Jakobi]

I don't think you'll be disappointed Trev. The only time I ever miss the 300s grunt is when I'm being lazy and running too many gears high into a hill and then get out of shape. Nothing that changing back down to the right gear can't fix.

With the 250 engine, and TTX suspension I honestly can't see things getting any better than this.

Glenn, I'm almost certain some of the newer bikes are using the same S3 cylinders. Next time I have mine off I'll check if its also stamped on the underside. The finish on the ports between the S3 and my stock cylinder were worlds apart.

I think I'll be having a go at doing my first bottom end some time this year so no doubt will just continue to add to this thread.

 

[alta redneck]

Hey Trevor where are you ordering your s3 kit from? I've been thinking of getting a s3 head for my bike.

 

[nambo-trev]

I ordered mine from gofasters, you'll need the cylinder kit and the head with inserts though. I already have the head and jakobi off the forum sent me a spare 250 red insert

 

[alta redneck]

I wasn't thinking of doing the 250 conversion, just a 300 s3 high comp head.

 

[nambo-trev]

Ya you could do the head with a high comp insert but from what I've read it will be of little benefit without the new s3 ported and honed cylinder

 

[alta redneck]

Ok good to know. Prob just hold off for a while then.

 

[GMP]

I'd just get the cyl. and have the stock head modified, then it is really corrected.

Sent from my C771 using Tapatalk 2

 

[Jakobi]

Hey Trevor where are you ordering your s3 kit from? I've been thinking of getting a s3 head for my bike.

Basically Trev already has the S3 outer head so by having the 250 insert I sent he can just pull the head, change the cyl, piston, and insert and thats all it takes to swap between the 250 and 300.

If you just want to get some more oomph out of your current 300 then the S3 head is really just a waste of money (but it does look good). I went this route myself and basically all the S3 does is increase compression by decreasing squish, the same way a simple shave of the stock head would do. As Glenn said, the best results come from modifying the stock head. It'll be cheaper and get you the best clearances and the CR to suit your needs, where the S3 will still end up having large clearances and then need to be modified for the real performance increases. Read more $$$.

If you were going to do the 250/300 combo you need a new head anyway, so the S3 becomes a much more viable option (unless if you already have an S3, then you just need a new insert).

 

[nambo-trev]

Looky what I got in the mail today!

 

[Jakobi]

Very nice Trev!

When are you looking at starting your build? I think you'll be pretty stoked with it mate! If you need any help crunching numbers and deciding on the gasket stack to use I'd be more than happy to help out.

 

[nambo-trev]

Thanks jake, I'm hopefully going I do it this Friday. I have rads to replace as well and my shock is out for a rebuild so I should have the time this week, Ill let you know how it goes

 

[Jakobi]

Because of the porting on the race cylinder you can get away with running the piston above the floor of the exhaust port at bdc without losing too much top end. I'm pretty sure 1 x 0.5mm gasket got me 1.25mm of squish with the black insert. Not sure where the red insert will land you with the same base gasket stack. If you take your time and lightly do the 1 base gasket and then measure up your squish we should be able to calculate the compression ratio. I have all the piston dome measurements and everything from mine somewhere in this thread. With any luck the red won't be too high on comp and you'll get away with only having to run a little bit more squish clearance than my setup.

 

[nambo-trev]

My original s3 race cylinder only ran one .5 base gasket as well with the high compression insert(not the very high) so that's what I was hoping to get away with here. Ill find out soon

 

[erniebearskin]

Really REALLY interested to here how this turns out as I also would like to go down for 250 for harescrambles. Wife wont green light a new bike for at least a couple more seasons.