street legal 2-strokes

[breakdirt916]

REVELATION:

I ran that bigger dome head for 2-3 years and I didn't even realize it

ebay title: "1993 YZ250 cylinder head with good dome"



^^ this pic was from 2017 when I had the motor rebuilt

I had no idea when I took that pic they were different

so yeah...you guys are right.

just send it

but now I'm very curious if this head + woods port would have been a good combo.

weird thing is I feel like the higher compression heads have a wee bit more low end

[breakdirt916]

ahh, back to "normal"



low compression head FTW

smoother off the line - you can just gently roll on + let out the clutch with minimal to no feathering

it made the bike behave 10% less "jerky"

easier to just "cruise" 40-55mph on pavement to Cook's Corner; off the pipe



(4.5 miles, 11 min ride)

was a hot one today too...93-102 while I was out

after 25ish mins of 55-65mph it fluttered around 175, and parked engine off like this:



not a single overflow drop



I like it!

now follow me:
-experiment with timing adjustments
-11oz Flywheel weight
-Keihin PWK36 or Smartcarb (currently a Mikuni 38mm flat side)

is that the ultimate trail tune for a '94 YZ250 2-stroke without compromising longevity?

I'm also tempted not to futz with it as-is

I may just add the coolant reservoir for insurance, then move on to ergonomics and cosmetic

[Kurlon]

I'm a big fan of coolant reservoirs, not much of a reason to not run them unless you're shaving grams off the bike for competition? On the carb front, I'm a lil torn, on one hand the Smartcarb did big things for my 92, that bike fires up hot, cold, no questions, no excess kicks, every time. On the flip side it replaced a W O R N out Mikuni VM36 so it didn't have a high bar to clear to be better. I have a 36mm SmartCarb new in the box that I bought for my 150 SX to replace the 'horrible' Mikuni on it and... I can't find fault with it. I'd say if the bike is behaving, I don't know as I'd suggest throwing that money at the bike for what may not be much of an upgrade?

[breakdirt916]

yup, I do remember how clapped out the VM36 was for you...so the gradient likely equivalent to running a worn out tire to a new one. They always feel better.

and maybe if it ain't broke, there ain't a real need to fix it...for $600

maybe I'll consider a SC if I was planning to replace the Mikuni anyways

priority re-arrangement:
-post ride maintenance (air filter clean/oil, chain clean/adjust, fastener check)
-coolant reservoir
-hour meter
-compression test
-ignition timing adjustments (likely need to re-advance after I slowed it down before)
-cosmetics
-ergonomics (bar risers + tall seat)
-mail out [woods ported cylinder + head] to EG for cylinder inspection/repair and/or hone + head work for squish band adjustment

still *very* curious if the woods port just needed a big ole' dome for a head and been alright. Advance the ignition to make it wind up a little more quickly, then just add a flywheel weight. Boom. As good as I'd get.

also - the good news is, I went 3 years on a cylinder, just did a hone, and now running the same cylinder again

as long as the bike isn't overheating, not running a high compression cylinder, a new piston/rings + hone every 3 years isn't a lot of maintenance

I just need to be extra careful for air filter cleanliness and I can probably safely go years

tentative zip on Sunday evening

[Kurlon]

Hah, in my case it was more like replacing a three time plugged, weather cracked, worn to the cords tire in the wrong size with a brand new knobby. I seriously think a windex bottle loaded with premix would work better than that old carb.

[typeone]

good to hear she's runnin' smooth ! carb talk reminded me i have a TMX38 oval slide w/RM needle and Hall's tweaks if either of you is interested. comes with a spare rebuild kit and divider plate as well. it's just sitting on a shelf.

[number9]

Hah, in my case it was more like replacing a three time plugged, weather cracked, worn to the cords tire in the wrong size with a brand new knobby. I seriously think a windex bottle loaded with premix would work better than that old carb.

When it comes to dome, I'm a firm believer that more is better

[Kurlon]

good to hear she's runnin' smooth ! carb talk reminded me i have a TMX38 oval slide w/RM needle and Hall's tweaks if either of you is interested. comes with a spare rebuild kit and divider plate as well. it's just sitting on a shelf.

If I can ever find dyno time for the 92, I may take you up on that... Dyno time, a repairable stock bore cylinder... my quest for things never ends.

[breakdirt916]

did a quickie after work Sunday



rode w' out earplugs, and man is the engine noisy



at certain RPM's it just vibrates

but finally getting some cooler temps

she definitely runs a little smoother when it's cooler

55-65mph cruising was no prob w' the 13/49 gearing too...*just* enough for me to ride from home to the local spot (17 miles/30 mins of pavement)

hoping to get a ride in every 1-2 weeks again

[breakdirt916]

did a 1 hour ride after work to get sanity back after work



man that Baja designs low/high beam works very well in the dark ass canyons

definitely next step: sit down and inspect the bike's fasteners. It's possibly vibrating something loose a little more than usual.

getting a little dark too early for after work rides though....ugh...I liked midweek dirt rides...maybe track under the lights?

power valve is definitely working - bike picks up!

[breakdirt916]

Breakdork916: I need to do more maintenance and put on an hour meter before riding again.

Also Breakdork916: 100 mile desert ride



Was itching to ride this weekend so badly that I had the bike loaded with gear on Thursday a Buddy offered to join, so we did our usual loop. 100 miles of open desert trails, mostly hard pack, some rocky hill ridges, a long sand wash, whoops, ruts, and some desert roads

Bike: pro’s: started and ran great! Highest coolant temp on the radiator cap was only 175ish. At one point (5th gear/40ish mph) it even dropped to 140 high today during the ride was 89 and it was fine.

Cons: it “skips” a fire when on the pipe WOT and blasting through the gears when it’s wide open. It almost feels like a minuscule “miss”. Jetting and plug match what I ran before, but my timing was retarded and not corrected. I will start with the proper timing as a baseline, then go to spark plug and jetting if necessary. Once it’s all good, add a flywheel weight.

Engine is still a little noisy for vibration at a certain RPM. Whatevs I think I had this before. Send it.

Riding position is still a little cramped while standing - bar risers should help.

Battery may have gotten disconnected when I cleaned the air filter.

one or the seat bolts backed out the last 2 rides. Threads in the subframe may be stripped, or I may need to put some loc Tite on it

[Kurlon]

Skipping, or detonating? Pull the plug, take a peek with a boreoscope and make sure things are happy in there.

On the seat, drill out the frame, helicoil. Had to do both sides on mine.

[breakdirt916]

Damn, I don’t have anything heli coiled, so I guess it is time



Forests are cooling down...reminds me of fall on the east coast

Man is that bike fun in the crisp cooler weather

Prob gonna do a night ride Sunday after work then use Tuesday as a full day off for wrenching and inspection and ignition advancement

edit: taillight LED is bouncing around in the assembly

I may try to glue it, but it may be time for a new taillight

[breakdirt916]

passed out Sunday after work

but another forest road re-opened after 3 years, so I thought I'd check it out today instead



views were ok, but meh...it wasn't worth driving 55 miles for 11 miles of dirt road. There's another forestry entrance 17 miles from me.

it was, however, kind of neat to see the peak (where those radio towers are) from the other side



^^usually I'm looking down from up there^^

some small sections of the road had the east-coast feel to it



the last 5 miles were 40ish mph pavement



^^ not bad

tentative scout ride this Saturday at Ocotillo Wells

planning a 40-50ish mile loop around a State Vehicular Recreation Area w' points of interest

front left turn signal stalk broke

I can't have ANY dual sport bits near any moving parts or it eventually breaks. The plate can't be under the fender, no turn signals near the front brake line, no speedo stuff on the forks, etc.

Edit: I need to order:
-2nd air filter
-extra OEM O ring head gaskets before checking the top end again
-new front turn signals
-flywheel weight

[breakdirt916]

Saturday Ocotillo Wellllllssssssss



3 hours of driving

it's a fairly large sized SVRA, but all the "main roads" or sand washes with groups of SxS and kids on dirt bikes whizzing at you

the fun stuff for dirt bikes are in the hills...



I just wished I knew where all the "good hills" were so I could link them together

main roads link you to points of interest




^^ the "pumpkin patch"

ridge riding through the hills on a small bike is rad





it was 90-93 and dry, and riding solo (with a satellite SOS) I still felt stressed out

up on a hill, the bike didn't start...so I bump started to get going

and on the long sand washes, I was worried the bike was "losing power" and the coolant temps were creeping into the 190-200 range

bike made it back to camp, and it could be that:
-long sand washes are hard on bikes
-being WOT in 5th and on/off the pipe will creep up coolant temps
-90-93 is somewhat of the upper limit to sand riding...it's going to run the bike pretty hot

I'm going to do a coolant drain/fill, top end inspection, and plug check tomorrow to be sure

but man that stress was not a good feeling. Super hot days may just be best in elevation within the forests (cooler up there), shorter rides, or coastal street bike rides on the 690

not sure I'd go back to Ocotillo anytime for dual sport riding when there's great high desert riding 2 hours from me. SVRA's are great when you have a group with mostly OHV's/SxS's, and camping out

[Kurlon]

Your bike has a radiator cap that keeps the pressure above 14psi, 200 deg isn't boil over, so I wouldn't be overly concerned about the temps you hit.

[backinthesaddle]

Friend of mine just did a fully street legal KTM300XCW-TPI or whatever the whole nomenclature is for that oil injected/fuel injected 2 stroke. Got a set of Warp 9 and Q3+ for track days and pavement fun, along with a larger front rotor and smaller from sprocket. Then goes back to the dirt set up for, the dirt or street/trail. Guessing his next step is dual sport tires.

[breakdirt916]

300 TPI is a perfect 10! Best dirt bike ever!

Wish I could CA plate that...alas not in my lifetime.

Good news @Kurlon - you are correct! 200 was not boiling temps:



(Full capacity 1.2L)

Piston had some carbon build up:



Did not look like any hot spots though...so detonation issue is solved

Cylinder head came out with a oil film, but it wiped right off.



Cylinder also looked generally ok:



Vertical lines are smooth to the touch. No snagging. Cross hatching still present.

This is good news! Everything looks generally good!

I still need to advance the timing but forgot my impact driver and flywheel holder tool at my other storage unit. D’Oh!

I also couldn’t button everything up anyways since the inner O-ring deforms during every tear down.



Might as well order spare inner and outer rings for insurance.

Alright then. No riding this weekend...next ride sometime next week.

Might as well clean the carb, new plug, new air filter, radiator Louvers to hold a coolant reservoir, clean the chain, and hand clean the bike.

[typeone]

i don't like to reuse o-rings but if they're recently fresh, sometimes a little grease will hold them in place while you reassemble.

spares are always good to have.

[breakdirt916]

yeah I bought four



seems like cheap insurance knowing it's sealed tight

and knowing the OEM gaskets expand under heat means it will seal even better after it's all snugged up

the tusk gasket looked exactly the same shape as when they it went in

went ahead and ultra sonic zapped the carb





and started "clean" with a 2 filter system



bike is still a wee bit harder to start w' the low compression head

took another ride



it's 98% good, but 2% of the time with sudden WOT it "skips" (?) a spark or misses for part of a second. It's not a completely smooth WOT/on the pipe behavior

at least I know it's not a dirty carb...test each system at a time

maybe a new plug

maybe advance that ignition back forward since I retarded it before to battle the detonation

ONCE THAT'S ALL AT 100%...then I'll start tinkering with cosmetics, and a FWW

I'd really like to see how it changes the bike when riding here:



I was always too scurred to try the nearby ST...but I did aight

it's all 1st gear mid rpm's, I stopped once or twice. lots of stress/forearm grip

[breakdirt916]

finally got a chance to advance the ignition



no rhyme or reason; no dial gauge, just twisted the stator forward

and it helped

starts a wee bit easier, on the pipe the power delivery felt more "full"

little bit more low end power too

it did not help here:



you never get out of 1st or you'll overshoot...constantly wobbling bars left/right to find balance

guess I just need more practice...ish is stressful...one foot was down 4-5 times

got into one pickle at a rocky uphill road...got stuck and wiggled my way out while bike was idling



lesson here: if you're stuck, and just wiggling your way with your feet/bars (no engine), just shut the bike off it's not that hard to start



couple drips

but once I got going, coasting down the mountain:



also, most of CA: guardrails here, guardrails there, we have guardrails everywhere

also CA:



"we're low on funds and can't build a guard rail at this location"

[breakdirt916]

did a general inspection for a 100 mile ride tomorrow

-5-6ish rear spokes were loose, 3 of them kept spinning without tightening
-the oil drain plug needed 1/8" turn to get torqued to spec...hmm
-tank shroud bolts needed a re-snugging

-the air filter didn't look too bad after 2 local rides:



it's hard for me to believe that the dirt from 4 of these local rides + 20 miles of the Mojave road destroyed the 690

something is definitely up w' that KTM

that rivit spooges a little



so I wiped it down...will check post-ride to measure the spooge rate

never did that until I had the can re-packed - anyone know if I can I put a dab of sealant in there?

decided to try a fresh plug to see if it cleans up the wind up "miss"



couldn't really tell on pavement...will find out tomorrow

we're also running race radios tomorrow instead of Cardo for the range since there are repeaters out there...ugh...wires

next steps:
-surface mount signals onto headlight
-coolant reservoir (I didn't see any raditor louvers?)
-flywheel weight
-new plastics + graphics
-custom rear plate mount on top of the edge of the rear fender, angled down
-moose rear fender tail pack- move most of my tools here, so I'll have a relatively flat tail pack that doesn't bop me in the butt
-dirtbikegear.com's front fender tube bag
-mail the woods ported cylinder + head to EG
-rox risers
-hand guards
-figure out which company made my skid plate and find a hardware kit for it.
-mail woods port to EG w' a cylinder head so it can be milled for pump gas w' out detonation
-time to service the 19" rear wheel - it needs a new tire, but consider getting the loose/broken spokes fixed, trued, new bearings + nitro mousse
-new front tire - I may go back to a Motoz tractionator. They lasted a super long time...maybe pair this with a mousse

[Kurlon]

Usually you smear some rtv around the pipe where you re-rivit it to seal it up after repacking.

[typeone]

^ +1

[breakdirt916]

70ish mile ride?



dunno if you can hear it:



it's almost like a stutter...only when WOT on the pipe

otherwise the day was friggin great

got stuck on one 1 hill climb

does this look hard packed?



nope, it was loose rocks almost like thick sand. Back tire started digging when I got around here



I still want the bike to be better on low rpm rocky hill climb ish.

Desert season is