S3 Race 250 Port Matched Cylinder and Head

[Jakobi]

This post is starting to compete with Brent's posts as the reality show enthrall of the year, hurry up and ride it...... Actually don't hurry, the suspense is just awesome!

Should I start blending the suspension talk into this thread too? I think I'm going to have to run the Ohlins 888 for at least a test run once I get the engine stitched back up and broken in.

Picked up some new bearings for the powervalve assembly and also gave the powervalve a bit of a clean up and polish. Will be spending the time to ensure the exhaust spigot matches the port 100% as well. Have to test the preload on the powervalve yet too, and if required will pull the RHS engine cover and adjust as neccessary.

Dave has also been kind enough to machine up 3 x 8mm spacers for the LHS powervalve cover which he'll send up at a later date. I'll be able to experiment to determine which provides the best bottom end.

And.. I still need to pull the carb and check the reeds over. They were replaced not that long ago so expected to be in good working condition. While in there I'll remove the spacer which is meant to boost snap and response on the bottom. She'll be like a new bike!

 

[GMP]

That spacer does not boost anything, it softens it from my experience. Its a case volume adjustment for the 300 as its based on the 250. Remove it for a 250 for sure.

 

[Jakobi]

I think we're saying the same thing re the reed spacer. I said removing it is meant to boost bottom end snap a bit. You said the spacer softens it if anything. Check! Removing it based on what you'd advised previously

I'm not sure how I'll like the larger powervalve volume, but with 3 spacers I'll be able to try different volumes and worst case I just run stock again.

 

[Jakobi]

So I have all the parts back from Dave now, and have a few days off. Just finished cleaning and assembling the powervalve. Will set the ring gaps and probably button up the top end this arv. Still need to get the carb sorted and remove the reed spacer and then throw the swing arm, shock and wheel back on for the moment of truth..

 

[Jakobi]

So the powervalve came up pretty spiffy after a light sand back and a polish. New bearings both sides should see it happy for some time. The exhaust spigot got the same treatment, however I didn't bother matching or polishing the exhaust port as I felt it was near enough already. The fit is much better on the 250 jug than on the 300.

 

[Jakobi]

Daves handy work looks great! I didn't take the time to confirm the squish again as the only change to deck height was made by reducing the gasket stack 0.8mm. You can see the piston sits above the exhaust port at BD. I set the rings up with only some light adjustment to the bottom ring gap. Everything snugged up without headache and the C-clipper worked a treat!! Highly recommended!

 

[Jakobi]

The powervalve governor didn't require any adjustment and pushed up against the stop under the current preload. Couldn't be happier about that! Even the head o-rings were playing the game today and more than happy to sit in position without jumping out.

 

[Jakobi]

The pipe is still in top shape for 165hrs too! The P3 guard shows some decent gouges where its been dumped and tumbled. Very happy that no damage has been transferred through. Surface rust was present under the carbon but thats to be expected.

Quick question regarding the last image. You can see the reeds have polished the intake as there are no reed stops. I have since removed the reed spacer so the reeds will sit in an extra couple mms. There is a defined edge from where they used to seat in the cases. I thought about sanding this edge smooth but don't really want any filings etc anywhere near the crank cases. Whats the odds that this little edge will eat up my reed petals? They are in fantastic condition currently. Opinions?

 

[GasGas]

I had to clearance for reed cage screws on my daughters 85 one time. I just stuffed the port with a rage against the piston, tapped over the rage and did the job with a Dremel tool. Then vacuumed the port out and wiped it with brake clean before I removed the tape and rage. A bit risky I suppose , but we never had any trouble. That RM 85 was bullet proof! I expect that you would not want an edge across the reeds.

 

[Jakobi]

Sigh.. This morning giving the bike the entire going over again I double checked the ignition side. Grabbed the flywheel and there is a very slight play up and down in the bearing. It is enough to feel but takes a good bit of force to move it. From all the research I have done it seems the 2010 uses a caged ball bearing which should have ZERO play. Looks like it might be coming apart again and more tools being purchased.

I've never had to split the cases and am not really stoked about having to do this.

Is there a tolerance for this or is it a must do right now? Its starting to feel like one thing after another and the learning curve is steeper than I would have liked for this week. If it needs to be replaced I think I'll take the whole bottom end to a mechanic. The only head ache then is finding someone repuatable who I trust won't screw something else up. I just want to ride now

 

[gasmonkey]

WELL RIDE IT NOW.Just keep an eye on it.It's easy enough to check at intervals later on.That bearing will let YOU know when it's about to fail.
Come on fire that sucker up and report back.

 

[Jakobi]

WELL RIDE IT NOW.Just keep an eye on it.It's easy enough to check at intervals later on.That bearing will let YOU know when it's about to fail.
Come on fire that sucker up and report back.

After going and having another round at it thats the conclusion I have come to as well. Using a large screw driver or piece of wood for leverage under the flywheel I don't get any movement. Using my hands I can't feel any movement or see any movement either at the flywheel or inside the cases (looking in from the reed block), but I can certainly hear movement inside the cases. Maybe its a normal tolerance, maybe when I grab it and move it back and forwards with some force its enough to slightly rotate it and I can hear the piston rocking in the bore.

What kind of symptoms will the main bearing give when its about to fail?? You are right though that its an easy part to keep an eye on.

 

[gasmonkey]

They get rumbly.Noticable when you turn engine over not to run.Extra noise when running.Seals leak giving inconsistant running.
An 05 I had did 350hrs with me(2 top ends) and as far as I know still rippin on those original bearings.
They don't like water though.

 

[Jakobi]

I believe the 09 and up use a different bearing on the ignition side. Sealed ball bearing like the pre 02 models did. The 02-07 used a 2 piece caged roller needle which had more tolerance and some movement was to be expected.

It turns over really smoothly by hand and showed no signs or symptoms prior to the pull down. A bit of vibration before the pipe (which it has since the day I bought it) and a bit of a whirr on deceleration at high revs which is I attribute to the engine turning over under no load. Not a sickly whine like a blown bearing.

I'll get it together and take it for a run to see how it sounds.

 

[(F5)]

Sounds normal to me.
Hard to say without feeling it, but C3 bearings do have a tiny amount of play, they have to, & will get tighter in operation anyway. Bigger the bearing the more tol comparatively. Generally when they go you will feel a knock-knock when moving up & down.

 

[Jakobi]

Sounds normal to me.
Hard to say without feeling it, but C3 bearings do have a tiny amount of play, they have to, & will get tighter in operation anyway. Bigger the bearing the more tol comparatively. Generally when they go you will feel a knock-knock when moving up & down.

What if you hear a knocking sound when moving it? Here's a vid http://youtu.be/87yovgws65I

I went and put everything back together and set the jetting at 45 N3CJ#3 178. The bike fired second kick and ran like a champ. Too big on the pilot but the needle felt pretty good. Better than it would in that clip pos on the 300. Tomorrow I will lean off the pilot and go half a clip leaner on the needle.

The bike felt fantastic. Very managable off the bottom with a sweet hit in the mid. Top end felt on par with the 300 and the bike felt much more inclined to rev up into the range. I'm definately very happy about that.

I seemed to be focusing alot on the engine due to the flywheel though which took away from the fun. The bike definately has a whirr to it when the revs fall away, but it always has (or has as long as I can remember). I have listened to it at idle in the past and thought it was pretty noisey too. Being my first 2 stroke its hard to tell whats right and whats not. It didn't feel anywhere near as vibey in the hands as the 300 did either! Another bonus! Here is a video (http://www.youtube.com/watch?v=kjFprYTZJZE) describing the sound I speak of. Its from when it was a 300 still and the sound is very much the same as a 250. Like a brrrr. Using a screwdriver as a stethiscope you can hear the sound everywhere. Flywheel, head, cylinder, and exhaust. Its really hard to tell whats abnormal and whats just vibration as well.

Tomorrow I will endevour to take the bike for an outing and run it through its paces and get some video.

 

[GMP]

If its bad, you will know it, trust us. It will get LOUD, and vibrate a lot more. Know anyone with a new late model GG with the sealed bearings? grab the flywheel in one of those for a referance. I never have, but I know the roller bearings feel real sloppy in both GGs and KTMs when new, but they run more clearance then a ball bearing.

 

[Jakobi]

Good thinking Glenn. I have a mate here with 2011. I don't think he's got too many hours on it though and last time I swapped his felt much quieter than mine. His was almost new at that point though and I was around 70hrs.

Looking forward to taking it for a ride somewhere tomorrow and seeing how it handles the dirt. Stumbled across a blown up rear wheel bearing so they've been changed out. Motosportz damper installed. TMD chain roller and guide installed. Talon pegs installed (after mods to RHS).New pro taper pillow top grips installed. I didn't end up making any changes to the cases where the reeds go. I ran my finger over it a few times and while there is a ridge its not sharp. They will sit in another 5mm now that the spacer has gone so should just start wearing the cases again further up. Also had to cut the ends off the reed bolts as they were too long without the spacer. All in all a bloody big day in the shed! Time for a beer before bed!

 

[(F5)]

All I saw was someone shaking a camera up & down like a hi tech peeping Tom. All I heard was a Gallah or whatever squawking in the background. Nothing looked obviously bad, I'm sure its just fine & you're panicking.

I've met people who really don't like those Pro Taper pillow top grips. To me I think they're the best thing to happen to dirtbikes since they put a similar shape tread pattern on the tyres!

 

[Jakobi]

I could hear a rice racer in the back ground and a bird of some sort too. The noise is kind of hollow. You could hear it more at the end when I give it a good shake. I set up something from the top of the flywheel to the engine case and there is indeed some play in there but its very minimal. I might add a dial indicator to the tool kit and just keep an eye on it for now. I have no doubt I panicked when I saw it I have a tendancy to do that. Thanks again for all the help and feedback from everyone.