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street legal 2-strokes

  1. #1076
    Lifer typeone's Avatar
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    Re: street legal 2-strokes


    bummer ... did you take compression readings before / after? i would just pop the cyl off and inspect at a high level first, engine builder is just gonna say, 'uh, you ride this thing on the street' ... 80:1 mix makes me cringe that puppy should live on 32 ... could be something simple like dirt ingestion or premature ring wear so i wouldn't freak out yet. if you don't want to take cyl off, could pull pipe and peek into the exhaust port as a first step.

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  2. #1077
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    If you want to be REALLY lazy, get on Amazon and buy a cheapie bore scope, pull the plug and take a peek in that way. Detonation can absolutely screw things up in VERY short order. Ask me how I know!

    And yeah, I'd want to be 40:1 on the street, with a fatter pilot jet. The bike issue is partial and closed throttle, when decelerating, etc. Engine speed is still up there, but now you're barely spitting any fuel/oil in to keep things wet. Two stroke cars typically had one way bearings so you the engine could drop to idle when you lifted the throttle without pulling the clutch for that exact reason.

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    Mistake - 1992 WR250ZD / 2000 LS650P / 2019 KTM 150SX / 2016 KTM 250XC / 2016 KTM 500XC W

  3. #1078

    Re: street legal 2-strokes

    Posted on the YZ250 Facebook group

    Tear down and inspection to start

    One suggestion is: the head will look worse if it’s detonation...the cylinder will look worse if it was those 4-6ish hours on 80:1

    Take it apart and inspect

    Tomorrow finishes 9 days straight...ughhh...but Saturday: 690 Canyon Run through Angels Crest Highway. Sunday: Universal Studios. Monday work and Tuesday tear down

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  4. #1079

    Re: street legal 2-strokes

    holy cow...just called Eric Gorr and he answered

    he suggested to:
    1.) inspect and figure out if I had a top end or bottom end issue
    2.) I can ship everything to him if I wanted; although shipping would be expensive - he's still happy to do it
    3.) the Millennium woods port cylinder could have caused the detonation - by changing the compression & port timing, so he said by trimming the head it could be setup to run on pump gas

    I told him I'd ridden an 250 XCW TPI and liked the light, linear, "torquey" feel, and wondered if there was a way we could tune the YZ to feel like that.

    He suggested that yes, it can be, depending on how the bike's setup.

    so...if I wanted this done "right"...how crazy would it be for me to mail Eric Gorr the whole motor...and maybe the carb?

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  5. #1080
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    I have that motor feel now, and don't want it.

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    Mistake - 1992 WR250ZD / 2000 LS650P / 2019 KTM 150SX / 2016 KTM 250XC / 2016 KTM 500XC W

  6. #1081

    Re: street legal 2-strokes

    Quote Originally Posted by Kurlon View Post
    I have that motor feel now, and don't want it.
    I kinda feel you...if I'm understanding correctly, a "woods port" or big bore actually gains 10% down below but loses 75% up top...it almost makes the top flatten out. Yuck.

    Maybe what I need is stock + FWW + FMF Gnarly + SmartCarb + saddle time

    I'm going to send EG the current setup; and also a stock cylinder. After his inspection; if we discuss that what I really want is stock, I may just have him setup both cylinders and send it back to me. I'll try the woods port for a month or two, then just swap the cylinder if I hate it, and sell the woods port on ebay as a low hour cylinder.

    Meanwhile: I can get the motor out in 1hr and 42 mins



    toolkit on fleek. This + breaker bar + 22mm socket + hammer = compete teardown tools

    uh, yeah



    yeah



    uh huh



    safe to say I had a top end detonation issue.

    my bottom end may actually be okay

    going to show the shop that built the motor first

    then send to EG

    Also - only 200ml of coolant came out!

    feel like I need to have it rebuilt, then run it, then tear it down (& inspect coolant level), then re-assemble and ride again. Then tear down & inspect to verify, then I'll be okay to go.

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    Last edited by breakdirt916; 07-13-21 at 07:31 PM.
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  7. #1082

    Re: street legal 2-strokes

    brought it to the shop that built it: he asked if the cylinder (which I had plated and brought to him) had the head sent with it. oopsie - nope.

    He also said there's a few different reasons why detonation happens. Lot of variables.

    I then showed him my previous (used) stock cylinder to see if I could run it:



    w' some cleanup & a ball hone, even with those vertical stripes, I could just get a new piston/rings and run this cylinder

    gonna bolt that onto the bottom end...going! going! back, back...to stock baby!

    gonna send the woods port cylinder + head to EG to get the head milled to match it up. I'll give the woods port one last shot. If an EG milled head doesn't give me what I want, I'm going back to stock for sure...I've got one additional (stock) cylinder to get re-plated for a total of three cylinders so I can fully experiment on this one.

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    Last edited by breakdirt916; 07-15-21 at 05:00 PM.
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  8. #1083

    Re: street legal 2-strokes

    old school machine shops: don't usually call you when it's done

    oh well...head and cylinder look good



    will probably put the motor back in with the stock cylinder and new piston by next week.

    going to do some testing. I want to drain/fill the radiator a few times to make sure it's not overheating...maybe add a coolant reservoir.

    once everything is groovy and ready to boogie, some local rides, then time to hand clean everything and move onto new plastics/classic graphics, and 2 gallon tank. Nitro Mousse and FWW, bar risers, and FMF Gnarly. It will be fully converted to small bike duty.

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    Last edited by breakdirt916; 08-11-21 at 02:48 PM.
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  9. #1084
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    Just add the resi now. Motion Pro bottle, ziptie it right to the radiator louvers, cheap and easy.

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    Mistake - 1992 WR250ZD / 2000 LS650P / 2019 KTM 150SX / 2016 KTM 250XC / 2016 KTM 500XC W

  10. #1085

    Re: street legal 2-strokes

    ordered

    finally got around to re-installing the motor

    literally: 20-30 min ordeal to get it back in. Not very hard at all...the most frustrating part was the piston circlip installation

    bottom end seemed fine...the detonation was likely just a top end issue.

    and we're back to stock:



    but umm...kinda sketchy revelation with the power valve: the linkage arm bolt had a nut between the linkage & the power valve

    I don't think there's supposed to be a nut. I think it's supposed to be a collar. With the nut, the whole thing freezes up and doesn't open.

    Is there a chance the machine shop lost the collar, replaced it with nut and my power valve may not have been opening?

    Was the woods port actually pretty good, and the whole time it was just my power valve staying shut?

    either way, that cylinder + head + piston are getting sent to EG.

    oh well...gonna order up some new parts off the fiche and install them to be safe.

    could not finish the bike either...couldn't get the damn cylinder head studs out of the cylinder. They were in there pretty tight, so even with the double nut trick, I started to strip the threads; so I just ordered new ones.

    oh yeah - the tusk gasket kit sucks.

    holes were way off; even with trimming



    eventually just ripped

    in case anyone was curious, here is a stock port vs. woods port. The woods ported cylinder has the swirl - that's where the cylinder was machined.


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    Last edited by breakdirt916; 08-18-21 at 01:21 AM.
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  11. #1086
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    On the powervavle, run the bike with the cover off to verify it's moving once you're fully assembled.

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    Mistake - 1992 WR250ZD / 2000 LS650P / 2019 KTM 150SX / 2016 KTM 250XC / 2016 KTM 500XC W

  12. #1087

    Re: street legal 2-strokes

    rockymountain - is FAST

    do they have amazon level distribution or something?

    anyways - THIS is what should be in there; not a nut



    still gonna go back to stock, but I'm VERY curious now if the woods port was fine in terms of power delivery...it may not actually flatten out up top. I may have never had a functioning exhaust valve.

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    Last edited by breakdirt916; 08-20-21 at 06:51 PM.
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  13. #1088
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    They've got two primary warehouses they ship from IIRC. Utah and Kentucky. If anything I order ships from Kentucky I get it DAMN quick compared to from Utah.

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    Mistake - 1992 WR250ZD / 2000 LS650P / 2019 KTM 150SX / 2016 KTM 250XC / 2016 KTM 500XC W

  14. #1089

    Re: street legal 2-strokes

    they deliver it before I even get a free day to work on it

    been asked to pickup more shifts lately...so I'll get a day off, then work 6 days straight until the next day off.

    Need to get back to riding on work days to get some sort of riding in...or weeks go by without any riding.

    So I was glad we at least we got some time at Pismo on a Razr 700



    Pismo's probably gonna close in 2-5 years...so if ya wanna OHV ride on the beach in CA do it soon!

    Took my time yesterday: trying not to finish the whole bike in one shot.

    Pick one section: (carb, top end, suspension, cooling system) and do it thoroughly. Hand clean each part, torque each bolt down properly. Measure out, don't eyeball.

    Top End

    I ordered the OEM parts for the power valve and I found a few things botched by the shop:
    -there's definitely supposed to be a collar, not a nut.



    The power valve spring rotates around this part so a nut doesn't provide that smooth rounded surface for it to pivot

    -the bolt he used, while it fits, is longer than oem, and has a larger washer integrated.



    I'm wondering if the length affects how it's seated/torqued or if the larger washer was making contact where it shouldn't. If I hand tightened down the parts he provided, the whole mechanism would lock up, so the power valve wasn't opening at all.



    ^^ here is the correct washer/bolt installed. The oem washer is super small so it doesn't interfere with the movement of the linkage.

    oh well. Correct parts have been installed. Power valve opens/closes with finger pressure.

    Good time to inspect the power valve stopper too:



    as you can see, there is some wear starting. The top one is the older stopper. The bottom was only used a short time.

    The power valve itself is also starting to show a wee bit of wear

    but have 2 sets...will last me 5-10 years. May order a new stopper regardless for cheap insurance. Going to send out cylinder #3 for a re-plate to stock + a head + power valves. May buy the next good set on ebay for $200-$250.

    otherwise, this part was done carefully:



    -piston: arrow facing forward
    -cylinder head o-rings: not pinched/trimmed

    getting studs out of the other cylinder was a pain with the double nut method. They were pretty stuck in there so I put new ones in.

    clean/straight head was seated carefully and cylinder head bolts torqued per manual specs. It was oddly satisfying to hand clean a bolt, put a dab of grease on the threads, torque it down properly, then wipe the excess grease. 2 strokes can be kinda fun to rebuild.

    next time: carb clean, fill radiator, install overflow reservoir.

    @ Kurlon - did you just install the reservoir zip tied to the radiator fins on the back?

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    Last edited by breakdirt916; 09-07-21 at 02:37 PM.
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  15. #1090
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    I install them in front of the radiator, zip tied to the plastic grill/louvers.

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    Mistake - 1992 WR250ZD / 2000 LS650P / 2019 KTM 150SX / 2016 KTM 250XC / 2016 KTM 500XC W

  16. #1091
    Lifer typeone's Avatar
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    Re: street legal 2-strokes

    ...if you do that ^ just make sure the louvers are secured, i lose those damn things almost every ride on last two bikes. have Unabiker guards going on soon (EE last bike).

    -----

    great work, man. i love seeing bikes revived and put to good use year after year rather than sold as a sack of shit.

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  17. #1092

    Re: street legal 2-strokes

    Quote Originally Posted by Kurlon View Post
    I install them in front of the radiator, zip tied to the plastic grill/louvers.
    Quote Originally Posted by typeone View Post
    ...if you do that ^ just make sure the louvers are secured, i lose those damn things almost every ride on last two bikes.
    ooo...I don't have louvers...should I get some?

    this is what I'm working with:



    finally got the exhaust, seat, tank, etc. back on the bike, 1.2L of coolant, 750ml of transmission 10w30, and fired her up!

    but...

    1.) I messed up - I somehow forgot to tighten the lower engine bolt, and it wiggled out (rest were tight). I lost the OEM lock nut. I also somehow lost the clutch lever nut. luckily they're still orderable...will use a home depot washer/lock nut so I can keep testing/tuning
    2.) the rubber chain guide on the swingarm is also busted and now the chain rattles against the swing arm
    3.) ^ with all these new noises, I can't tell if the bike is detonating, or if the power valve is working

    but if I had to guess, based on a couple trips around the block, I'd venture to say it's still detonating

    only thing I can think of now is going back to a used stock head...maybe the one the shop machined to straighten it out increased the compression. Maybe just run race gas.

    I want to do some controlled tests - I wanna run WOT in 3rd on a lake bed, then make a timing change, then try again. Then swap a head and try again.

    also wtf - 8:30pm at night on a 3 lane parkway that terminates into neighborhoods and EVERY time I pull out there's a cluster of slow cars

    every time I braked, tons of cars behind me tailgating

    it's too crowded here to make testing easy I'm tempted to head to the desert to a dry lake bed

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    Last edited by breakdirt916; 09-14-21 at 12:17 AM.
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  18. #1093
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    You can still order the radiator louvers new, 'bout $80 for the pair. They're on the 'Side Cover' fiche. I didn't see any used sets on eBay when I took a quick look.

    I'm with you on wanting to have some place to just do a long rip after playing with jetting/timing. The dyno that was local to me is no more so I can't cheat and do it that way, I've got no where close that I can wind it out in 4th and 5th to see what happens, bah.

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  19. #1094

    Re: street legal 2-strokes

    Omg omg omg

    I made a last ditch effort amd decided to try a used older head I had kicking around

    And wow...it looks a little different than the other 2!

    (Pardon the size...I will re-size when I get home)



    The bottom one has a way wider “bowl” (?)

    Uh wat??

    They all have 4EW cast on top. An eBay search for 1994 YZ250 heads brings up heads that look like the top 2

    Bolted her up and fired her up - first kick!

    And the motor felt “easier”

    Maybe a little less low end, but smoother and no detonation!!

    Is that possible?? And why does this head look so different? WR250 head? Did someone machine it?

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    Last edited by breakdirt916; 09-14-21 at 05:44 PM.

  20. #1095
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    That bottom head has been reworked. Almost looks like it was recut for an overbore.

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    Mistake - 1992 WR250ZD / 2000 LS650P / 2019 KTM 150SX / 2016 KTM 250XC / 2016 KTM 500XC W

  21. #1096

    Re: street legal 2-strokes

    But it works!

    Kinda

    But now what?

    Does that head needs to be measured to ensure the the O ring gaskets still seal and just run it?

    Or should I try to set the squish band on the middle head pictured and either add base gaskets or have that head worked, to match the stock bore cylinder?

    Edit: Facebook chatter suggests the top 2 were milled for more compression and the bottom may have had the squish band set

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    Last edited by breakdirt916; 09-14-21 at 06:13 PM.

  22. #1097
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    O-rings should be fine, I'm +6mm and they still seal without issue. If it's running well, run it.

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    Mistake - 1992 WR250ZD / 2000 LS650P / 2019 KTM 150SX / 2016 KTM 250XC / 2016 KTM 500XC W

  23. #1098
    Backwoods lobster boy number9's Avatar
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    Re: street legal 2-strokes

    Quote Originally Posted by Kurlon View Post
    If it's running well, send it.
    fixed

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  24. #1099
    Lifer Kurlon's Avatar
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    Re: street legal 2-strokes

    Quote Originally Posted by number9 View Post
    fixed
    I knew this subscription to MotoGrammarly would pay off!

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    Mistake - 1992 WR250ZD / 2000 LS650P / 2019 KTM 150SX / 2016 KTM 250XC / 2016 KTM 500XC W

  25. #1100

    Re: street legal 2-strokes

    I'm still sketched out...I'm tempted to just send it, but if I know something's not right it will be in the back of my mind that it'll explode

    photo dump...

    this is what I saw after maybe 10-15 mins of test riding on the fresh rebuild w' milled head:



    hot spots for sure (detonation?)

    and these two heads look so substantially different that I'd worry it's the wrong piece for the the application





    I think I want to send a head to EG

    I'll tell him I'd want it cut for pump gas. He's got the measurements

    in the man time, I'll still go tinker at a lake bed this week to see how it feels and maybe do some plug checks.

    While EG is working on the head, I'll do more cleaning, plastics, hour meter, fix rear right signal, plate mount, rear tool pack mount (get it out of my backpack), coolant reservoir, new tires/tubes, balance them, and swingarm chain guide

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