S3 Race Custom Modified EC250 Complete Rebuild

[Jakobi]

Originally Posted by dmcca

Jake post up a pic of the underside of the piston.

With the ignition the stock advance is only about 20-22 degrees at lower rpm from memory. There's room to go higher by a 2-3 degrees but then as the curve retards in the higher rpm you'll be left with a little too much advance, should still be safe with correct squish, etc but you'll lose a little top end and over rev. Have a play going from +2 to -2 and see how it feels with the mods you've got. There's no single best curve, it's all relative to the individual setup. That's why programmable ignitions are so good cause you can set it exactly how you need it.

I'm about to start working on it again now. Just finsihed making sure the work area is clean and laying out fresh rags again. I'll pop the pin out and snap a few more shots of the piston. I expect to see some colouration on the underside. Probably not as much as last top end though. The bike has consistently ran richer jetting, but it has had a few runs at some pretty lean needle positions when first evaluating the needs of the 250. As above the mark in the center of the piston dome is from the plastic plug I used to stop the engine turning over TDC when removing the flywheel nut. I don't think I want to cut down the top end anymore so might just leave the timing initially. I'm definitely interested in shuffling some shims and getting the pv open a bit sooner.

[Jakobi]

When installed the rings were as follows
Top ring: 0.27mm
Bottom: 0.33mm

After 100hrs they have both worn but the top ring seems to have showed considerably more wear than the bottom. The gaps where measured at
Top ring: 0.88mm
Bottom: 0.63mm

The crank feels like it has no up anddown play but it does feel a bit like it can rock side to side. Actually side clearance when pushed up against the thrust bearing/washer is 0.8mm.

Here are the piston pictures. She sure has ran on the ragged edge from inspection of the underside. Will probably trade out the 175 main for a 178 or even a 180 as the colder months come upon us. The piston dome has been wiped down with a clean rag now and the little carbon on top wiped off easily. There are some harder carbon deposits sitting in the transfers and I would say these would have occured during a testing phase. Basically I have been running 40 N3CW#3 175 for the majority of the top end, but had run as lean as 42 N3EJ#1 178 for a small time. Obviously everywhere in between too. Interestingly, the piston underside has more carbon buildup on the intake side of the dome where you'd typically expect the exhaust to be the hotter part. The skirts look good and you can still see the remains of the coating on the piston in many places.

Wiped down


Underside (exhaust side at top)


Intake Side


Exhaust Side

[Jakobi]

A bit of excess blow by on one side.

[Jakobi]

Here's the cylinder. Its still got loads of cross hatching visble. It hasn't been cleaned or deglazed yet. Appears to be markings in areas but nothing that I can feel and should clean up well. I think the rings were stretched out a bit too far at 110hrs.

[Jakobi]

I think the trainee at the factory must have had a go at bending the tabs up on the retainer for the clutch basket.

[Jakobi]

Ok after couple of loads of washing I decide its time to delve into the unknown. Of course this is when the fun and games (read sweat and frustration) begins.

Of course I had to miss one of the bolts holding the cases together even after being sure I had them all! It just had to be done. No wonder the cases wouldn't part and it felt much harder than I imagined it would. Luckily I didn't perserver too much. I admit I was stupid enough to work on it longer than I should have though. I'm just gratefull I didn't crack the cases or anything stupid.

Next up cases split. Gee that was really easy with all the bolts out. Apart it comes nice and evenly. As I'm lifting the top off and watching what I'm doing carefully I notice the gears want to stay with the top half, so I let them do just that. Everything is still nicely meshed together and sitting in the other half of the cases. Fair enough.

The main bearing on the flywheel side of the engine decided it wasn't playing the game and is still on the crank, with no bearing in the case. Is it ok just to use some heat and hold the bearing in the vice while pushing the crank back out?

And.. The other side of the crank needed to have the keyway removed before it would press back out. The manual makes no reference at all to this. Is it just a press fit back in at the end? I'm worried it'll fall back out.

So after all that, I am where I want to be. A little wiser to the whole process, and ready to go and drop the crank in at the shop tomorrow morning.

[Jakobi]

And cases once split




Heres some close ups of the rust on the governor spring.




In regards to the gearset, is there anything I should be looking for in terms of wear or damage? I'm not sure what they should look like originally so hard to know whats normal or not.

[twowheels]

Originally Posted by Jakobi

Of course I had to miss one of the bolts holding the cases together even after being sure I had them all! It just had to be done. No wonder the cases wouldn't part and it felt much harder than I imagined it would. Luckily I didn't perserver too much. I admit I was stupid enough to work on it longer than I should have though. I'm just gratefull I didn't crack the cases or anything stupid.

You won't do that again


The main bearing on the flywheel side of the engine decided it wasn't playing the game and is still on the crank, with no bearing in the case. Is it ok just to use some heat and hold the bearing in the vice while pushing the crank back out?

Sure, or use a split bearing puller ... but heat will help in any case.

And.. The other side of the crank needed to have the keyway removed before it would press back out. The manual makes no reference at all to this. Is it just a press fit back in at the end? I'm worried it'll fall back out.

The key should be a snug fit in the keyway. If not, replace or perhaps use a dab of bearing retainer.

So after all that, I am where I want to be. A little wiser to the whole process, and ready to go and drop the crank in at the shop tomorrow morning.



Watch that the little plastic shift bushing in the lower rear part of the case is still there when you re-install the shift shaft.

Awesome progress and better reporting

[dmcca]

You're certainly not the first person to try splitting cases without removing all the bolts! You'll never do it again, that's for sure!

That piston has run really hot, thought it'd look like that based on the build up on the crown. I wouldn't go any more advanced with ignition just yet. Definitely go up one on the main.
The comp is on the high side and most likely causing a bit too much heat. I know you love the way it runs but if you want to go down half a point on UCCR then just send the head back and ill take some volume out... Then you'll be able to jet down and may unlock some extra power, at least up top anyway.

With the transmission just look for scoring, discolouration, wear marks, etc on the teeth, shift forks and dogs. Some minor wear is normal, a lot of wear or discolouration is not.

[Jakobi]

Originally Posted by dmcca

You're certainly not the first person to try splitting cases without removing all the bolts! You'll never do it again, that's for sure!

That piston has run really hot, thought it'd look like that based on the build up on the crown. I wouldn't go any more advanced with ignition just yet. Definitely go up one on the main.
The comp is on the high side and most likely causing a bit too much heat. I know you love the way it runs but if you want to go down half a point on UCCR then just send the head back and ill take some volume out... Then you'll be able to jet down and may unlock some extra power, at least up top anyway.

With the transmission just look for scoring, discolouration, wear marks, etc on the teeth, shift forks and dogs. Some minor wear is normal, a lot of wear or discolouration is not.

Cheers Dave. Thanks for your input and guidance, and also for the offer to take some more material out of the head. I may take you up on that yet. We'll see. I always felt that the 175 main might have been a touch on the lean side of the spectrum. I'll always welcome more top end too

I had a quick go at removing the main bearing from the crank using some heat but didn't have much success. I'll do it in the dealers workshop tomorrow morning when dropping it off. He'll then have Griffo rebuild the crank.

You are totally right about the splitting cases too. I'm still banging my head that I spent the time I did dicking around with it. As soon as I felt resistance at the puller I should have realised what was up. It won't happen again! Part of the learning experience too. I also had some fun cracking both the 30mm nuts for the crank pinion and the clutch basket. Used the electric impact on both of them but they took quite a bit of work to rattle free, even when holding the basket and blocking the pinion.

In regards to the plastic spacer, already taken care of and back on the shift shaft where it belongs. Lots of tupperware and takeaway containers filled with parts in snappy bags.

Next stage, cleaning up the cases and getting the old bearings out and the new ones in. Maybe not tomorrow, but will at least get a start on it before heading back to work for another tour.