KX Riders
Maintenance & Technical => Kx Frankensteins => Topic started by: scottysg on November 03, 2015, 05:19:24 PM
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Hello, this thread will attempt to document the process I go through to install a KX500 engine into my street legal 2002 YZ250 dirbike.
Purpose: The goal of this project is to have a true, no compromise dirt bike (2 stroke) that also performs reliably for consistent road use, and in motord trim gives quick road bikes a run for their money. Budget has not been decided. In my experience, these projects always break it so I may never set one. Thriftiness will be required.
Motivation: I bought the YZ250 to get back into the off road scene after being away for 5 years. The kicker was I also wanted to get to work on it legally. Something about starting the day smelling that castor oil... I guess we all have our addictions! (another one is boost, so that will come to this bike one day, but not now)
The YZ's been great to get to and from work (17" wheels, 15-49) since the max speed limit is 45 on my route, but it really doesn't have the torque to pull the highway gears (14-40). And don't even get me started on lack of wheelies...Needless to say, for my application there is no replacement for displacement. Enter K500!
The 1988 KX500 motor I bought appears to be in good condition. It shifts nicely, piston and cylinder seem brand new, and it was sold as a fresh rebuild, though with unknown porting, and high compression piston. The inside of the cylinder that I can see looks good, with totally fresh looking crosshatching from hone. I need to get a little mirror to see the other side. The engine did not come with any external electronics, but the flywheel is there with wiring harness coming out from behind it. I have no more info on it, so I should probably take it apart to check everything. If anyone knows how I could do that without needing new gaskets, please let me know.
I have been looking at an ecotrons efi kit, to solve the lack of CDI and it also allows me to upgrade to a turbo setup when I get used to this bike how it is. Its very reasonably priced, around 500. Need to do more research here. I feel like this would be a great possibility for an arduino, but I don't know if I have time for that now. Open to suggestions for this problem.
Check it out!
(http://i1379.photobucket.com/albums/ah149/scotty-sg/photo%202_zpswa9hwcmg.jpg)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/photo%201_zpstsd1urqm.jpg)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/photo%203_zpsqa7dmepi.jpg)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/e523838a-fa5f-4dd7-983e-839116d2b24b_zps8bismxot.jpg)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1620_zps6z0k8xon.jpg)
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Is the KIPS valve assembly in place and not cracked? That's one of the issues I had with my 88. Also, does your engine have the KIPS cast onto the left side of the cylinder? For some reason your cylinder looks different than mine, but I can't find a decent picture of mine from that side.
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Umberto, KIPS is cast into the left side of the cylinder.
Tonight I will get a light up into the exhaust and look for cracks in the valve. Then I will remove the side cover for the kips and see if I am able to actuate the valve.
I noticed the rings where the exhaust springs hook onto the cylinder are pretty worn out. The springs have acted like a knife, sawing away at the cylinder material. If I can find a stainless steel grommet that size to put into those holes to prevent it from getting worse, I think it would be a good thing for me to do. I will get some pics of that as well.
I got an email back from ecotrons. They suggest their 2 stroke kit with a 38mm throttle body. They corrected me, telling me that their unit does not control spark, only fueling, so I will need to get the CDI and coil anyway. $799 was the quote price for EFI. Then I would need to upgrade the stator to supply enough power to run it all, another $500 ish. Looking at 1500$ to go EFI yikes.
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Here is a shot up into the exhaust port. Nothing seems cracked in there. Using my fingers, I can rotate the power valve drums, not sure if that is how it is supposed to be.
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1692_zps4td04awh.jpg)
This shot shows how worn the exhaust spring retainer is!
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1690_zpsvyvk0wvj.jpg)
Using a 10mm on the power valve arm bolt, the two drums are operated and open to just the right location. No visible cracks in them.
Check out this last shot. If you look real close, you can see someone tried to chamfer the edges of the ports. They are not done evenly at all, especially the one left center. Is this really bad?
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1693_zpsouuzwz71.jpg)
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Can you see if the entire KIPS linkage is in place? You shouldn't be able to rotate the drums with your fingers. You may be missing a part or two, which isn't a big deal (I bought several parts for mine on eBay and Rocky Mountain). The important thing is that the drums are in place and in good shape.
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I Would not go moving kipps arm by the 10mm nut
The GOVERNOR roller bearings can fall apart inside the clutch cover
Looks good inside that cylinder
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The whole assembly seems to be there. They move together so it seems ok, but you're right umberto, I probably shouldn't be able to move them with my finger. Also, are you still thinking that my cylinder looks different than yours? Im curious, especially because I really have no way to verify the year mine is.
Yikes thanks for the heads up on not moving the arm dave916. I don't want problems in the cases!
Bought a coil today for 13 $, Im still on the hunt for CDI, kick starter and expansion chamber. Id like to have a compression release too, so Im reading all about that.
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Maybe Dave916 could comment, but I think your motor may be an 87. This motor Foxx posted from eBay looks similar to yours but with paint.
(http://i.ebayimg.com/images/g/cL8AAOSw14xWQH8z/s-l1600.jpg)
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Umberto, you may be right! If i post my engine serial, would we be able to identify the year?
Parts Updates!
-Used '88 kx250 CDI (fingers crossed its gonna work alright)
-brand new coil
-Used fmf fatty with a broken mount (ok since I have to chop it to fit my frame anyway)
-Used ignition cover and gasket
Still need:
-Kick start lever (read the '04 is the best) Anyone got one! :?
-Sending my head to Larry next Tuesday for a compression release since I'm 6' @ 150 lbs and i need my energy for riding! Im a packaging engineer with full access to multiple cad programs, countless materials and machines so its gonna be the best custom packed cylinder head ever! :) Let me know if anyone needs a custom package for engine parts, I am the man with the solution!
On another note, work is relocating me from Orange county to ventura county starting jan 1. I just found out a couple weeks ago. Switching from designer to project coordinator and sales. Hopefully more money for buying motorcycle parts! That will delay this project slightly as i will be looking for a place to live and moving. Considering full time motorhome living to save money haha pm me if you have any advice or tips for that. Also I'm going to thailand for 2 weeks starting wednesday then idaho for christmas when i get back. So ill be making pretty much no progress for at least 5 weeks unfortunately.
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I lived in a 40' 5th wheel for 7 years. It was cool you definitely meet some interesting people. RV parks aren't too hip to dirtbikes!! Now that I own a house n have a family I would never do it again. Only tents when we camp n ride, but the wife has been bugging for a motorhome
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Updates today! Been really busy with work this month. finally got time to jump on this project. No mods have been done to the frame. The KX fits with the rear axle and lower engine bolt lining up. will need to modify the head bracket and make some adapter for the front engine bolt.
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_0019%201_zpswxn53tvg.jpg)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_0023_zpsgoxlzzkf.jpg)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_0030_zpshfzlapmp.jpg)
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Last night I used a dremel, a file, and tap magic to remove 0.315" from the inside chain side of the swing arm because the kx motor is quite a bit wider at the rear mount that the yz motor. Test fitted, and the sprocket looks like its centered pretty good with the rear sprocket. But there should be a slight gap between the swingarm and the engine. So I will remove material to get to .375" total material removal. This is very easy to do, just slightly time consuming.
Now the holdup and the hard part is removing this 0.375" from the bearing pin. I couldn't even scratch that with my fancy file, it is extremely hard material. Ill have to take that to a machine shop to throw on a lathe. I found a bearing online that will replace the 2 bearings that are currently in each side of the swingarm, except of course it is .375" shorter that the 2 oem bearings total width together.
Once the rear mount is sorted out, I can move on to the front mounts. Then figure out what carb I want to run.
As a side note, there is a slight bit of slop on the flywheel. Like its not tight on the crankshaft and it rotates until the key stops it. I don't have a flywheel puller for this yet but if you guys think thats pretty weird Ill have to just pull the flywheel and make sure the key isn't sheared then lap the crank and flywheel to fit more snugly.
Any thoughts or suggestions are appreciated. I don't know what I'm doing here :)
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Last night I was able to ream the hole in the engine. used a grizzly 43 64 drill bit. (17.07mm, I read about this on the forums as a good overbore to allow clearance, not my idea) sorry my slash button is broken on my computer. its a hss chucking reamer so it was easily able to bore the hole in the soft magnesium. I also started removing .25" of material from the clutch side of the engine mount, so as to let the engine fit in there. I got tired and wanted to eat before I got all the way to .25". I have .125" to go. Unfortunately I am an idiot and in my stupor didn't realize that the swingarm bolt changed from 17 to 18mm from '01 to '02, which my bike is, so the swingarm pivot bolt still doesn't fit in. So I ordered a 23 32 chucking reamer (18.25mm)to bore it again to the next size.
Also, I removed the flywheel, used some valve lapping compound and worked the flywheel on the crank. both the flywheel and crank had surface rust. Now they're polished clean and after a hit with a mallet, it is locked on there. stator looked good, though i have no experience with kx500s so that comment is pretty useless.
Waiting for parts or tools sucks!! Its so close, the hole is going to be very clean indeed. Today i should be able to finish cutting the motor and getting it fit in the swingarm. Cant wait to get this rear mount figured out and get going on the other mounts. hell i can't wait to spark it up.
Im just lost with how I want to fuel it. I have the kx500 carb and the yz250 carb. But I've read that 500's are hard to tune (and I'm nothing special at carb tuning) and I'm trying to spend my time riding not tuning. not to mention if I'm riding at gorman its freezing then I go to barstow or ocotillo and its 100 degrees out. because of that a lectron sounds very appealing. If any one has some advice on this matter, Id appreciate it. Pics to come tonight.
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I have a Lectron on my 525. If you are riding that varied of conditions, it's right up your alley. There are only two adjustments, the needle for open to 1/2 throttle, and the power jet for 1/2 to full. It takes minutes to tune, plus they can get it pretty close from the factory. I bought mine from Packard racing. I have a post on my 2003 conversion showing what mods I did to get it installed.
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now you need black plastics and paint frame green :-D
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(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1946_zpsnhpqgcfm.jpg)
the rest of the pics at: http://s1379.photobucket.com/user/scotty-sg/library/
Please check it out and let me know what you think! I appreciate any input you have for me :)
umberto I may try the lectron in the future for the reasons you've posted. I was emailing David over there, i believe he is the vp. He was very kind and helpful, so I would like to give them business if It works out. for now, as you can see in the photos in the library attached, the oem carb fits almost flawlessly. I just wish i could stretch the rubber .375 inches on top. If anyone has tips on that, I would appreciate it. I love how I can do some metal work but when it comes to a rubber... Im just no good ;)
The kx exhaust is way huge on the yz frame. Gonna need to cut it up so I can lower it about 6 inches and remove the stinger almost completely. I may cut a short segment from the belly. Ive been doing a lot of research and it appears this would increase the top rpm, which would give me more the small 2 stroke revability which i fell in love with as a kid and still find more fun than anything. Also interested in belly exit exhaust instead of at the end of the baffle. who knows but I'm gonna have to cut that pipe up like swiss cheese here this weekend.
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Looks like it's going to be one hell of a great ride when it's done. Look up pics of the 125 air boot and compare to the 250 boot. I bet the 125 air boot will reach a little farther. Take a chance on one from eBay. Even if it doesn't work, you a won't be set back much.
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http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1416_zpsgmxokjfh.jpg
https://www.youtube.com/watch?v=CnXQ6syZqg8&feature=youtu.be (https://www.youtube.com/watch?v=CnXQ6syZqg8&feature=youtu.be)
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Break in done. I know my jetting is rich so Ill work on that tomorrow. Not sure the needle clip position, ill find out. right now it has a 170 main, 60 pilot, and air screw at 1.75 out. more smoke than I like. Jetting chart on this forum suggests 168 main and 58 pilot. My gearing is 13-40, weird i know, its just what I had. But I figured it would pull harder than it is so I know jetting must be off. Although, starting it is a 1 kick affair, unlike what the internet would like you to believe. definitely not getting a compression release yet. Im beginning to think 500's are more myth than anything else :\ "please let correct jetting cure my need for speed". I won't be happy until theres solid matter in my britches.
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Looks like it's going to be one hell of a great ride when it's done. Look up pics of the 125 air boot and compare to the 250 boot. I bet the 125 air boot will reach a little farther. Take a chance on one from eBay. Even if it doesn't work, you a won't be set back much.
When I finished getting everything in, the airboot was almost perfect so I ended up not needing to change it. Thanks for this tip though, I didn't know that.
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Looking good!!! Crisp jetting will make a world of difference. My son used to think mine was a bore, now that I got it dialed in he is scared of it. Says it stupid why would you need that much power. I say don't be little girl
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Took a trip to divide peak behind Santa Barbara. Awesome views. But the bike ran like hell. Moved the needle to the third position. Tried 58/168 then 55/165 jets with as many air screw adjustments as I could. If I didn't know any better I'd say it feels pig rich. Just falls on it's face blubbery after a pretty lame low end. But at wot there's hardly any smoke, so it can't be. I'm scared to go more lean that that :/ the bike idles great! Minutes more than any 2 stroke I've had. Seems crisp off idle if revving it in nuetral. Timing is good as per dots on stator. Spark looks good jumping to the block, plug is gapped to 24 thou. I'll try the "kips bolt mod" as I've seen it called, tomorrow. I hope that's the problem. If not then I'll pull the kips plastic cover and see if the arm is moving. If they're moving and I've checked for over rotation, I guess the drums could be a tooth off, so I'll have to pull the head at that point. Out of ideas after that.
Also, I noticed a lot of tranny fluid coming out of the plastic nipple on the inside of the case behind the kick starter. My skid plate was soaked and it was obviously coming out of this spot. Gonna hook up a hose to this and zip tie the other end somewhere higher on the bike so it can drain back down. Is tht normal for it to expel so much fluid from there?
1.1 hours on the clock and running poorly I'm scared I'm gonna break this motor before it's running right. Oh well gotta run it to tune it :/
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I have taken my main jet from 160-178 at every step and see no change in my wot performance. its unbelievable. My float valve is adjusted to spec. The carb has been thoroughly cleaned. Every port\channel is clear. I checked the power valve system it appears to be in spec. It just doesn't wanna rev or give me any power. Im on the beach and its 70 degrees. A friend suggested I check the reeds. How do these pictures look
(flashlight behind pointed right at the reed tips) Theres barely any if any light coming through the reed tips. however there is light coming around the edges as you can see. These are v force reeds, the old ones with screws holding the reeds on the block. Should I replace them or do I need to look elsewhere as to why my bike runs like a$$. Ive never had a reed issue on any of my bikes ever so I'm doubtful this matters. A 500 piston coming down should create enough pressure to close these little valves, but thats opinion only not experience.
Thanks for your help.
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1457_zpsj61p5cjr.jpg)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1458_zpstowqgjmk.jpg)
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Didn't read the entire thread..... But if your using a used carb... I have tried to tune several of the socal guys stuff... But couldn't due to football shaped NEEDLE jet.... (Ahem... Shlepy)....
Edit.. Are you located on Santa Barbara? If so you may be in the "socal crew". That gets super squirrel help and info....
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Should I replace them or do I need to look elsewhere as to why my bike runs like a$$. Ive never had a reed issue on any of my bikes ever so I'm doubtful this matters. A 500 piston coming down should create enough pressure to close these little valves, but thats opinion only not experience.
Thanks for your help.
sorry if you've said you already done so...I didn't read the entire thread, but...
have you verified the KIPS are indeed working?
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haha interesting, ill check out the needle. Thanks for that tip. I got the carb from a guy in north dakota. I live in ventura, so santa barbara is just a cruise away. Im not sure what the socal crew or super squirrel help and info is.
I checked kips while running and the arm is moving like it should. Looking into the exhaust, the ports seem to line up right when its moved, so I'm fairly confident kips is not the issue. however I am new to kips.
Ill call around to some shops and see if I can't get some new reeds for this block. process of elimination...
Thank you,
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Ill call around to some shops and see if I can't get some new reeds for this block. process of elimination...
Thank you,
these are the replacement reeds you want....
(http://i895.photobucket.com/albums/ac152/foxx4afoxx2/vf2_zps9add932e.jpg)
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Ill call around to some shops and see if I can't get some new reeds for this block. process of elimination...
Thank you,
these are the replacement reeds you want....
(http://i895.photobucket.com/albums/ac152/foxx4afoxx2/vf2_zps9add932e.jpg)
thank you very much! this is really helpful.
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It's not the needle that is the problem... It's the tube that it goes up and down in... It is a jet. , and when the needle wears it out it makes it impossible to get fueling right....
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I checked kips while running and the arm is moving like it should. Looking into the exhaust, the ports seem to line up right when its moved, so I'm fairly confident kips is not the issue. however I am new to kips.
Thank you,
this probably isn't the culprit...but,
did you happen to notice if the center "flapper valve", at the top of the exhaust port was opening fully as well, when you were checking the side valves?
over time the pins get worn and that valve won't function fully....in other words, if that center "flapper valve" can't open fully...it'll choke itself to some extent under full throttle because the exhaust port opening will be to small.
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It's not the needle that is the problem... It's the tube that it goes up and down in... It is a jet. , and when the needle wears it out it makes it impossible to get fueling right....
Motorrad I see now what you mean. I hadn't even thought that could happen. Ill take a look at it and see how loose the needle looks in there.
I checked kips while running and the arm is moving like it should. Looking into the exhaust, the ports seem to line up right when its moved, so I'm fairly confident kips is not the issue. however I am new to kips.
Thank you,
this probably isn't the culprit...but,
did you happen to notice if the center "flapper valve", at the top of the exhaust port was opening fully as well, when you were checking the side valves?
over time the pins get worn and that valve won't function fully....in other words, if that center "flapper valve" can't open fully...it'll choke itself to some extent under full throttle because the exhaust port opening will be to small.
This engine only has the 2 barrels, theres no center valve.
Thank you,
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my bad...chalk that up to me not paying attention. :lol:
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Not sure why. But I've seen more k5's with the worn needle valve than other modernish bikes....... Now old bultacos... Don't get me started...
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Not sure why. But I've seen more k5's with the worn needle valve than other modernish bikes....... Now old bultacos... Don't get me started...
Its clearly because there is so much fuel gushing through to the massive engine. Its natural erosion like the grand canyon except it only takes years not millions of years. :p
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(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1461_zpsbsphibxu.jpg)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1462%201_zpsrdknfi7u.jpg)
The needle jet looks pretty good, but I can't say I know what Im looking for.
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My stator plate came loose! The screws were almost all the way out and timing was like 15\20 degrees off. The plate was flopping around. Miracle nothing catastrophic happened and incredible the bike even ran. Realigned the dot, used red instead of blue loctite, and the thing ran much better. Im sure I could benefit from fresh reeds which I will order after my next paycheck, and I need to get my jetting dialed in, but Im relieved that Im on the right track now and can focus on tuning.
Thank you guys so much for your help along the way, this has been an extremely fun process and I couldn't have done it without your support!
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:lol:....sweet.
roost on!
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Glad you had an "ah-ha" moment. It's such a great feeling when you start getting the motor headed in the right direction. The guys on here are so good about helping you out with questions and sharing their knowledge. I'm pretty sure most of them have forgotten more about KX 500s than I know. :-D
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Not sure why. But I've seen more k5's with the worn needle valve than other modernish bikes....... Now old bultacos... Don't get me started...
Can those tubes be replaced, or is it time for a new carb at that point?
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Glad you had an "ah-ha" moment. It's such a great feeling when you start getting the motor headed in the right direction. The guys on here are so good about helping you out with questions and sharing their knowledge. I'm pretty sure most of them have forgotten more about KX 500s than I know. :-D
It is amazing to have a resource like this. 20 years ago you were on your own for the most part. Now a guy like me who knows nothing can put a bike together and get riding quickly thanks to helpful guys on here.
Speaking of which, please take a look at this youtube video and let me know if I'm getting closer with my jetting. 168 main, 60 pilot, 40:1 927, 70 degrees at sea level. I had the timing on the center mark with a 170 main and it didn't want to rev on top. I retarded the timing halfway between the center and retarded notch and put the 168 in. It doesn't blubber at wot as much anymore. i just don't want to go down too much and run lean. Plug chop to come after I get the seat of the pants tuning dialed in.
https://www.youtube.com/watch?v=AWk4577qW50
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It sounds good, but I would still do some plug chops just to make sure. Better safe than sorry for sure, especially with the less common 1988 motors we have.
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It sounds good, but I would still do some plug chops just to make sure. Better safe than sorry for sure, especially with the less common 1988 motors we have.
Good call, I want to keep as many of these alive so our species does go extinct :)
Check out this shot of my plug chop: 69 degrees, sea level, 40:1 maxima 927, 168 main, 58 pilot, air screw 1.5 turns out, fresh filter, slightly overcast\foggy.
Got the bike warmed up for about 20 minutes, shut it down, pulled the plug, put a brand new one gapped to 22 thou (manual says 24 but Ive had better results with 22, does anyone possibly know why). Started it up, rode to the end of the block not at full throttle but pretty quick, turned around, wound it out to the top of 4th, pulled the clutch\hit the kill, coasted back to the toolbox, and this is the result. Not seeing a perfect 'ring' like I've seen on the internet. Also, since I'm doing this on roads (ahem in mexico) I didn't want to have it wound to the top of 5th for 1 mile at wot like I've read I need to. with my gearing thats like 120 lol. I don't know if this would lead to my test giving inaccurate results.
Let me make a guess before the experts tell me what the plug actually says: The motor is running slightly rich at wot based on the carbon deposits that have lightly covered the whole tip of the ceramic. I could go down 1 size on the main, but for safety, its probably best I stay with this size.
Alright guys, let me have it-what is going on in my engine! Thanks for the tips :)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1500_zps9npruitk.jpg)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_1499_zpsxx0k81gc.jpg)
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The bike is running great! My computer got stolen which is why its been challenging to get pics up. In any case, I rebuilt the motor, got the crank balanced and bearing seat repaired at crankworks, the bike is very smooth. after lots of experimenting with heat wrap im pretty settled. the bike is now just a rider, not a project anymore which feels great. though its almost red sticker season so knowing me ill have this apart again soon riding other bikes. it pulls very well. if i could get it to hook up... my friends dont ride behind me anymore and tires dont last very long out here in californias rocky terrain. the frame seems to be holding up well to the extra weight. i have a big desert tank too so this was never planned to be a light bike. im a tall but very light guy so i just point it and hang on! its been a fun journey to get this done.
If anyone has questions about the work or problems please let me know, im very happy to share what ive done :)
The problems with this build seemed never ending
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_0380_zpsnh7uy0rr.jpg)
this is why you shouldnt hit doubles on a street bike...
(http://i1379.photobucket.com/albums/ah149/scotty-sg/6e46b8c7-4da5-4009-848c-9c2f491b4c1b_zpsmqqze9rn.jpg)
killed my old dc welder, got this fancy new one and i recommend it to others
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_0406_zpspm3llmrq.jpg)
proud over my creation! (heat wrap not finalized in this photo, im using much less now)
(http://i1379.photobucket.com/albums/ah149/scotty-sg/IMG_0066_zps7n5bnzza.jpg)