typeone's Beta build (250RR)

[typeone]

sweet! nice that you have precision control like that. i geek out on that shit. every tiny bit counts!

[Paul_E_D]

KTM engineers in Easter Eggs all over the place. Some of this stuff isn't even published in their manuals.

[typeone]

i believe it, especially with the size of the community. i got heavily into that stuff with the XB and SXV... EcmSpy, MegaLogViewer, TuneBoy, etc. jesus i wasted a lot of time logging > studying > tuning > testing > repeat. was always worth it though.

oh the days before dependants

[typeone]

welp, pretty uneventful disassembly, everything looks great in there. barely any carbon buildup on piston, just like last time i peeked, tiny bit of blow-by and tiny bit of coating wear on the skirt. not bad for ~120hrs. cylinder walls look new. (pic was fuzzy)

will reassemble tomorrow.. .

[Paul_E_D]

Hmm, interesting. No carbon pattern at all indicates fuel washing. Are you running it really rich? I was always looking for a butterfly pattern on mine with dry areas near the intake and exhaust ports.

That rod looks ready for some knife edging, cases stuffed, piston skirt shaped... lol

[typeone]

Hmm, interesting. No carbon pattern at all indicates fuel washing. Are you running it really rich? I was always looking for a butterfly pattern on mine with dry areas near the intake and exhaust ports.

That rod looks ready for some knife edging, cases ported, piston skirt shaped... lol

thnx for input... it was on the rich side for most of it's life but not by much really. first time i checked the piston the carbon pattern was in the center, like the attached image below.



when i buttoned it up last spring (after cleaning most of the carbon off) the piston looked exactly as it does today. i ran a race gas mix for a while and went leaner on jetting. need to check my logs to see how many hours i put on it last season but i tend to average 40hrs or so per season. now that there is daylight i'll check the plug more carefully, it did look rich.

my float has been set too high for it's whole life too, i corrected that so i guess i'll run the new top end and peek halfway through the season to see how the piston looks.

on more motor mods, i expect this bike will last quite some time so i'm sure i can fuck it up somehow

[typeone]

btw, knife edged rod? is that a thing? i've had ports knife edged before but have never heard that for a rod.

i would love to get the crank balanced though, thing has some pretty decent vibes to it. finally going to loosen all motor mounts and re-tighten in an order that was recommended to me. vibes aren't crazy bad but seem a excessive for a 250.

[Paul_E_D]

balancing the crank/rod assembly will simply push the vibes one way or another since it has to be balance at a specific RPM. My fully balanced race motor was startlingly vibey until 12k, at which point it felt like it would rev without limits. hahaa.

Absolutely on knife edging the crank. It is straight in the path of airflow. so is the piston skirt...

[Paul_E_D]

Dirtbikes for general use are much harder to read/optimize. You are using a motor with a narrow tuning window for a broad range of conditions. It may be spot on while ripping, but rich and washing the piston while lugging, or vice versa, and that may be OK. ride-ability is key here, not perfect jetting for max HP.

[typeone]

balancing the crank/rod assembly will simply push the vibes one way or another since it has to be balance at a specific RPM. My fully balanced race motor was startlingly vibey until 12k, at which point it felt like it would rev without limits. hahaa.

Absolutely on knife edging the crank. It is straight in the path of airflow. so is the piston skirt...

hmm, that makes sense. i really only notice the vibes on the low end like idle and light throttle. guess i'll do the bolts and not think about it again.

Dirtbikes for general use are much harder to read/optimize. You are using a motor with a narrow tuning window for a broad range of conditions. It may be spot on while ripping, but rich and washing the piston while lugging, or vice versa, and that may be OK. ride-ability is key here, not perfect jetting for max HP.

true, this bike spends a shitload of time in the low revs with the torque it has. only gets wound out on open straights. it's always felt jetted very well but a hair on the rich side. i went a bit leaner on the early part of the needle taper, richer on the pilot, same main at the begining of last season.

[Imbeek]

Absolutely on knife edging the crank. It is straight in the path of airflow. so is the piston skirt...

Huh? What is knife edging and why would you want to do it to anything not in the fuel delivery or exhaust path?

[Paul_E_D]

on a 2 stroke the rod is right in the middle of the fuel delivery path. knife edging is exactly what it sounds like. lightening the rod by shaping the leading/trail edge. Combined with stuffing the voids in the cases with epoxy and shaping that you reduce the volume of space in the intake tract and optimize the SPEED of the intake charge. This allows a knock on effect for tuning. If you can stuff more charge in faster, you can run higher compression without the normal loss in efficiency.

[typeone]

2-strokes are awesome

[Paul_E_D]

I meant to say rod, not crank. edited.

[typeone]

so i'm reading around a bit on Beta piston coloring... apparently what mine looks like is common when using Amsoil Interceptor/Dominator and stock jetting. i've read about others with "very little to no carbon buildup on piston dome and PV", "no hint of carbon buildup anywhere on the internals" and "piston dome and exhaust ports are spotless." third bike was at 100hrs and used for racing.

my PV has a bit of buildup but nothing exessive. guess i'll keep my jetting intact and run it!

[Paul_E_D]

If it ain't broke...

[typeone]

...try and break it?

[number9]

Knife-edging is done on four-stroke cranks, too, though typically only in large-horsepower builds in the race car world.

[Paul_E_D]

Cranks are a bit dfferent as it is done to reduce windage. The rod on a 2t is for air flow.

Sent from my SM-G930V using Tapatalk

[typeone]

top end is all buttoned up. felt sacrilege to throw a Pumpkin heart into my Eyetalian beauty's chest (same piston+ as the 250SX)

the gasket kit came with 3 thicknesses, 0.3, 0.4, 0.5 (stock). i'm trying the 0.3 for added grunt, easy enough swap if i experience ping or don't like it. with the torque wing, thinner gasket and shorty pipe, the low > mid should be quite fun. hope i don't lose too much top end but i rarely ride it up there. thing was stupid fast with stock setup and gearing. i was a little sad to lose some of that upper speed when i swapped to a 50T rear but got over it on the first few steep ascents.

today's adventure is installing an oversized clutch slave from the '14 350RR Racing model. i already love the MME lever, but the larger cylinder and piston of the 350 slave should slather in a lil more budder. (yes, i know, every other dirt biker on the internet has stronger hands and never changes the feel of their clutch. not interested.)

side note: i didn't realize how well WD-40 will liquefy thick globs of 2T spooge. magik.

[loudbeard]

top end is all buttoned up. felt sacrilege to throw a Pumpkin heart into my Eyetalian beauty's chest (same piston+ as the 250SX)

Queso we riding this weekend?

[typeone]

Queso we riding this weekend?

yessir, HVD you in?

[loudbeard]

yessir, HVD you in?

Oh fawk, they're open now? Well I'm 50/50 then, I just ordered the hitch for the Dad Wagon yesterday and it won't be in. I have a local buddy who might be interested, between my trailer and his tow hitch we might be able to make it. I was going to suggest a session at the Rehoboth training grounds but it's definitely no HVD.

[typeone]

Oh fawk, they're open now? Well I'm 50/50 then, I just ordered the hitch for the Dad Wagon yesterday and it won't be in. I have a local buddy who might be interested, between my trailer and his tow hitch we might be able to make it. I was going to suggest a session at the Rehoboth training grounds but it's definitely no HVD.

the rangers are cleaning up flood debris this week, tentative opening is 4/22.

would def hit the RTG but have to stay fairly local this wknd. plus i'd like to do a few shakedown runs to make sure the winter maint is good to go. might jam out back before the weekend to test, which would be ideal.

[Paul_E_D]

If TTD gets canceled due too cold rain, I'm up for an HVD day!