top end

[2strokeforever]

i took my reed off to look at the bore and saw this, felt it and it looked like a crack

soi tore it down
the motor has 9 pints of oil(5of 927 and 4 of super m) thru it at 40:1 jetted decent, so thats 80 gallons (320L) of gas thru it, heres what it looks like, i like the high precision casting on the dome

looks familiar, look at the stuff roosty sent bob, and the untouched OEM part of the cyl

looks like a bit of stop sign action, wonder if torquing the head studs has anthing to do with it, its never been bored, or touched





its not cracked, it just looks and feels like it, its marks from where the piston stops at the port

poped the head while i was on 927 and foud lots of carbon on the piston .5mm i guess(i had jetting issues then so it might not be the oil) and i chipped a bit off then switched to super m, and the castor gunk is still there, and you can see the clean bit where the super m didnt gunk up

but the castor left the head spotless, like it was just washed in solvent, and the super m left a bit of color


little black spot



got a mint PC works for sale 5 months old only $200

crank big end side 28 thou, piston cly I could get a 4 thou feeler in without forcing it, front/back/bottom with the piston 1 inch from the top
just posting it up to see if theres something im missing, or is it just getting broke in?

[AlisoBob]

.... or is it just getting broke in?

It looks kinda hammered for such little use.... Heres some photos from my recent teardown on a motor thats 4 years old, with about 100 gallons of gas through it , on 927' 100% of the time.


Hardly any carbon on the piston, parts numbers still quite visable.



Zero blowby, skirt looks 90% of new.



Lotts of heat in the crown.

I think once you get it back together and lean the thing out, the new found power will really get your attention.....

[kdizzle]

man that topend looks like my first 500 teardown. Looks like you had a loose piston in there, maybe just a couple thousands extra. mine was at .007 and looked just like that.

nothing some proper machining cant take care of. Also throw that prox in the trash. I personally have had awesome luck with Wiseco. Im too nervouse about those brittle cast pistons, and always run forged. my 2 cents...

[AlisoBob]

...i like the high precision casting on the dome

As Service Honda " hand assembles" every engine, I would think they would have taken a sanding roll to that.....

[2strokeforever]

when i first got it while wrestling with the airboot, it popped 1 inch of the boot out of the airbox(behind the airbox door), it was for only 1 ride tho, that let some dirt in, i glued it and i check it every ride now

i dont over rev it often, but when i do im usualy in first WFO, with no traction, how bad is that for it?

I think once you get it back together and lean the thing out, the new found power will really get your attention.....

its kept close right now, but even with the jetting right on 927 thru the trails where im hardly on the gas sheed fill right up with oil
ill use 927 when i know im gonna be wfo for a while tho, like a climing day, ya and adjust the jetting too... with my intelajet

[AlisoBob]

That piston crown didnt get all funked up with crisp jetting...

[2strokeforever]

ill give it another go then and see if it carbons up

[NightBiker07]

i dont over rev it often, but when i do im usualy in first WFO, with no traction, how bad is that for it?

you cant really "over-rev" a 2 stroke.....it will just run up to its MAX rpm and stay there. the max rpm is usually determined by the pipe, and the motor physically cannot rev farther than where it maxes out when you hold it WFO.

i wouldnt hold it at redline for miles, but its perfectly OK to run her out in-between shifts or while riding up a hillclimb......

[pstoffers]

...i like the high precision casting on the dome

As Service Honda " hand assembles" every engine, I would think they would have taken a sanding roll to that.....

You really think they are going to mic a new cylinder then keep micing a piston tell they find a piston to fit the cylinder...... let alone fix a brand new head. I'm just say-n

[pstoffers]

here is a VERTEX piston that has 6 rides on it. The cylinder was brand new as well as the piston.

[Roostius_Maximus]

that sucker is beat!
wtf?

[pstoffers]

that sucker is beat!
wtf?

Wait till you see the cylinder when you get it..

[100hp honda]

thats what i like about ktm. 100x better attention to detail than honda. like a fine rolex watch you could say . everything is perfectly machined and cleaned up at the factory. no goobers in the cylinder ports, no funky casting shit in the head. squish, ignition timing, crank end float, piston clearance... all perfectly set before it rolls out the door. cases are matched to the cylinder as well. dude on the assembly line scribes his number into both cases, designates them a matching set i guess. these heads dont use a gasket, machine to machine fit. think glen could pull that off ???

[bearorso]

I started, about 20 years ago, putting quite a pronounced radius on the rear inlet port at the vertical/ horizontal join point, and radiusing the edge of the piston skirt at that point, plus getting rid of any stress raisers on the inside of the inlet (indeed all of the piston) skirt.

It effectively stopped that sort of cracking, even with me using up all the std pistons I've had in storage for years, with them going in with large clearances on both the piston / bore and big ring gaps. Just up to 500hrs, and I've run out the std pistons, so a re-bore , with a Vertex piston, that up till now I've seen nothing but good reports on, is on the cards - I think I'll have to go to at least a .5mm overbore, or more. I've been running the CRE very much on the cheap for the last 4 years .

[Roostius_Maximus]

ok, you have to look at the bikes that were in production, the service hinda stuff is all on moulds that are getting worn, you should see a new cylinder compared to the old ones
Ktm took their tooling and made it into something else long ago. I'm sure if they were making parts, the same amount of parts that the honda moulds have pumped out we could expect the same.
No one has ever said the honda machine work is off, i checked the new cylinder for dubious to make sure it was strait and on size, that sucker is within .0002 top to bottom.
If anything can be said positive about the new castings, i guess they're getting thicker

[dubious01]

see thats quality with integrity and professional workmanship.

That is the reason I sent my stuff to him.
He is the only one I trust that will give as much a fuck as I do about my stuff... even more maybe, and with much more experience, than me.

[2strokeforever]

well im gonna slap it back together till i have enough $$$ to send it to roosty in a 2 months or so, ill be getting the full deal from roosty, and surf n turf crank balancing

ill be checking for cracks every ride, and taking it easy too

[NightBiker07]

Dont tell me that slug is out of that new S/H bike you just bought???

[2strokeforever]

ya, but to be fair dirt went through that motor, i dont know how much
anyone with an af keep an eye on the airboot/airbox connection, mine sliipped out while prying on it to get the carb in

[bearorso]

I've worked with KTMs, both privately and in dealerships. In dealerships I've run workshops and been the warranty manager. So I've dealt with numerable problems with them. KTM are even worse than Honda in not recognising a problem and rectifying it, and that's asking something with Honda's track record.

You're kidding yourself about them being better made. Just like any other mass produced bikes, corners are cut everywhere. It's the way it is.

Paragons of engineering, they are not.

Just check the endless discussions on KTM Talk on the 'X' measurements for barrel/piston/head heights and clearances, for a very basic and simple quality control issue. A continual inability to get consistency in these components (or add in conrod / crank to that to get correct 'X' measurement) is not particularly impressive.

Don't get me wrong, I like KTMs, and when and if we finally see the long rumoured DFI 2ts, I'll be hankering after one. I'd like to have a 011 300XC, if it were available here, AND without the crazy price difference we have from the US prices. Well, that IS the primary reason I don't have one at the moment - the rest of the world seems to get reamed on KTM prices - we seem to be subsidizing the lower US prices. Fuck that for a joke - Leask and Co have more than enough money.

[bearorso]

2 strokes,

I just looked closer at the piston etc, this time with my glasses on .

To me, it looks like it has ingested a shit load of dirt, just by the markings on both piston sides. And the lower edges - either the piston had very bad finishing along the lower, outer edges, or the visual inconsstances along the arc / edge is alloy pulled/skuffed down.

I'm a bit of a cheapskate at times, and can appreciate that you might not want to spend money just before you spend big money for engine work, but even I would be wary of just slapping it back together. At least have the cylinder honed / cleaned, check clearances as best you can on the bottom end, and check the prep on the ports. From the picture, that could be misleading, it looks like the rear inlet has had no radiusing / clean up, and some of the others as well. It looks like they are that sharp, lint ,from perhaps, a rag you've wiped it with has been caught on the edge of the port.

That , and the state of the head, really shows that SH are just slapping these things together, with no real attention to detail or care. Perhaps it's a rare 'Friday arvo ' bike - I sort of hope so. But when people are paying so much for an SH bike, and the way SH tout them, you'd rightfully expect premium and expert prep and assembly. I think the last time I checked their 500 crate motors, they were priced at $6500 (I very much accept I could have that wrong). It's a lot of money, but, if it were put together with the care and perfect prep and set up I'd expect for that price, I could, to a certain extent, understand it. But not after seeing your pics and others.

And how in hell do they make an airboot / airbox junction that so readily fails, just during the re-fitting of the carb.

Very disappointing to see. I'm not ripping into you, or your, undoubtedly, much loved bike - just bad/unacceptable assembly and engineering from a company that should not be letting this out to a, well paying, public.

The more I see of the paid for conversions, the more I hold respect and enthusiam for (most) of the home builds.

[2strokeforever]

At least have the cylinder honed / cleaned, check clearances as best you can on the bottom end, and check the prep on the ports

havent honed it but the rest is done

crank big end side 28 thou, piston cyl I could get a 4 thou feeler in without forcing it, front/back/bottom with the piston 1 inch from the top

It looks like they are that sharp

, not sharp just a really linty pair of underwear were used to wipe excess wd40 off

And how in hell do they make an airboot / airbox junction that so readily fails, just during the re-fitting of the carb.

i assume its the same as any af conversion (kz3r) and i was cranking the crap out of it learning how to put the carb in the easiest way, that was my fault

it would be nice to see a boot made specificaly for conversions tho...


ill be sending it out as soon as i can afford it, shouldnt have bought winter tires for my truck... and ill check the piston for cracks EVERY ride

[AlisoBob]

and ill check the piston for cracks EVERY ride

I think your being a little dramatic...

[AlisoBob]

The more I see of the paid for conversions, the more I hold respect and enthusiam for (most) of the home builds.

I've been saying the very same thing for years....

[britincali]

Just pulled my 3 year old top end (bored 1 over and a new oversize OEM oversize piston) and guess what....