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Discussion Starter #1
I was tuning my stock 86 lt250r Mikuni carb the other day, just the slide and air/fuel for idle and had her running really good. Started this based on new info from reading and watching vids. Took the 250 around the block and ran out of gas on the main line (petcock) just before pulling her back into my drive. Switched to the reserve line and tried to kick her over and the engine just kept flooding and I mean real bad. I did manage to get her started again but with an extreme amount of smoke, definitely not motor oil in the crank case (or coolant) but an extreme amount of fuel getting into the crank and combustion chamber. Fuel was spraying out of the exhaust and dripping from the mid pipe at the silencer connection (known exhaust leak). She WAS idling fine though even with this condition. JUST tons of un-burnt fuel.

Soooo I took the carb off and given it was off I took a peak through air intake on the topend and slowly (spark plug out of course) kicked her over and found the piston to be slightly/noticeably marred (can feel it with finger). I'll post a pic soon. It appears the cylinder sleeve has escaped any damage that would cause problems down the road, in my estimation at least (feels smooth) but I would definitely appreciate feedback on this as to its condition (again pics incoming, stupid 2mb limit). I would rather not have to replace the sleeve (stock bore) and I don't really want to get her bored out but given the choice between the two, bored out might be easier/better? I'm assuming that the sleeve isn't going to want to come out willingly and probably requires heating the case, but I'll look further into that if need be.

Alas, to spite my best efforts, when I removed the hinge-pin to un-mount the piston something, not sure what or how cause I had a shop rag stuffed in around the rod/bottom end, but something managed to fall into the bottom end and wedged it's self under the connecting rod. I can see it but can't tell what it is and there is no way I'm risking just removing this piece of whatever and calling it good, even if I could manage to get it up past the rod and out. In addition to whatever fell into the crank case there's muck in there, dirt or some type of debris, which could be responsible for marring the piston and I'll feel A LOT better about things with a fully rebuilt/clean engine which is now the project I've started...that was going to wait till winter.

I don't have the manual yet but that's now gonna happen sooner than I had planned as well. I'm confident I could get by without it giving all of the info that's already out there but...Murphy's law and all that. Noticed from the beginning that the kick start assembly is a bit wonky, way to much play and feels like it missing a "stop" (missing tooth on a gear, again don't know all the terms yet) inside the case. So really just going to go through the whole thing. It will be a long time coming (first time so taking my time) but once she's put back together it will be worth the wait.

Definitely appreciate any feedback on the smoke and fuel condition I ran into. Maybe the oil mix in the reserve portion of the tank was incredibly rich? Didn't understand how the tank and petcock worked when I filled her up the first and only time in my hands and didn't drain from the reserve position before adding new fuel so maybe it was just the old fuel mix in reserve? The flooding was incredible though and float seems fine. Ohh, last question. How much lateral play should there be with the connecting rod on the crank shaft? Thanks for any input.
:Cheers:
 

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Discussion Starter #3 (Edited)
Ok so what's up with Suzuki using phillips head screws for the crank case cover??? Anyone have the specs on these screws? Going to have to easy out them (were already stripped) and don't want to replace with phillips head screws. Does the manual give that kind of information? I'll have the manual by end of the week but I can easy out these screws as soon as I have that info. Thank ya.

Also watched a vid on splitting the cases, definitely getting a splitting tool, have to be way easier and safer than using a fladhead and mallet. Should have the engine out of the frame tonight. In addition, the reeds look good from what I can tell. No chips in the petals, pita where there located though for future replacement. What exactly is the purpose of the reeds? That's all for now, hope everyone's enjoying their 250's...
 

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My guess is it's one of the washers between the piston and rod bearing that fell. If it were me I'd try to get it out rather than split the case. Reserve isn't two tanks, there are two inlets that stick up from the bottom of the tank out of the petcock. Think of them as two straws, the longer one is the main position on the fuel tank, once the fuel level gets down to it's height fuel no longer can come in so you switch to reserve which pulls fuel from the shorter straw. Could be as simple as when you switched to reserve you pulled crap from the bottom of the tank and wouldn't let the needle valve seat to stop the fuel flow.

Before you go any further and strip out anymore screws buy an impact screwdriver like this one: http://www.homedepot.com/p/TEKTON-3-8-in-Drive-Impact-Screwdriver-Set-7-Piece-2905/205674679?cm_mmc=Shopping|Base&gclid=CLvZurG3rMgCFZSMaQodvA4N5A&gclsrc=aw.ds If you are going to work on quads you will need one a lot. Usually need them for the stator screws too.

Reeds are pretty much your intake valves in a two stroke. When the piston is on it's way up it pulls a vacuum behind it which opens the reeds and pulls fuel into the crankcase. This is how the crank and connecting rod are lubricated. When the piston is on it's down stroke the reeds close and it pushes the fuel mixture through the transfer ports to the top of the piston and the compression chamber. There's more to it obviously but that is enough to give you a general idea how it works.
 

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I agree, when you said something "dropped" other than the circlip... It's one or both of the thrust bearing washers between the rod and piston. Your best bet...unless you can use a small magnet to pick it out.
Pull the motor out of the frame and turn the motor upside down and move the crank back and forth to rattle it out.
Otherwise, if it is jamwedged...you'll hafta split the cases to get them or the one out. It'll wreak havick in the piston and cylinder!

As for the question of the reed set-up on your motor, 85-86 used a "piston port - reed set-up " that's why they have the reeds on the bottom of the cylinder.

87 all the way up went to a full reed cage design, instead of the combo of the earlier model.
85-86 has a WAAAY small intake but .. you can make them run due to the limits.
 

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Like the gentelman said, get a magnet. I have a telescoping one. You'll get it out.
I agree to take the motor out. This way you can put fuel mix in the motor and turn it upside down to clean it out.
You don't need no splitting tool. We'll tease you....LOL j/k
Rod play:: a lil side to side play is normal. If it is exessive then you will feel it go up and down. Up and down is no good.
"I removed the hinge-pin to un-mount the piston something", That's the piston pin and cir clips. :)
Using ethenol gas? That's caused alot of flooding problems.
You need a .5 over piston and new bore to match. Replacing a sleeve isn't near as easy as you think and usually not done till it is bored to max or gets a crack in the sleeve.
Hope that helps a lil.
 

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Discussion Starter #7
Before you go any further and strip out anymore screws buy an impact screwdriver like this one: http://www.homedepot.com/p/TEKTON-3-8-in-Drive-Impact-Screwdriver-Set-7-Piece-2905/205674679?cm_mmc=Shopping|Base&gclid=CLvZurG3rMgCFZSMaQodvA4N5A&gclsrc=aw.ds If you are going to work on quads you will need one a lot. Usually need them for the stator screws too.
Yeah, an impact driver would be good to have. Good looking out. The screws are possibly salvageable using an impact...They were already in the beginning stages of being stripped and I didn't make things any worse. We'll see. You are correct about the washers...the clips are in hand but the washers, well I didn't know about em and that has to be what fell into the crank area. Definitely going to try to get them out. Thanks for the info on the reeds!
 

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Discussion Starter #8
Like the gentelman said, get a magnet. I have a telescoping one. You'll get it out.
I agree to take the motor out. This way you can put fuel mix in the motor and turn it upside down to clean it out.
You don't need no splitting tool. We'll tease you....LOL j/k
Rod play:: a lil side to side play is normal. If it is exessive then you will feel it go up and down. Up and down is no good.
"I removed the hinge-pin to un-mount the piston something", That's the piston pin and cir clips. :)
Using ethenol gas? That's caused alot of flooding problems.
You need a .5 over piston and new bore to match. Replacing a sleeve isn't near as easy as you think and usually not done till it is bored to max or gets a crack in the sleeve.
Hope that helps a lil.
Yeah, I imagine replacing the sleeve is a pita. I'm not actually the person who bought the gas so it is entirely possible that the person who did, bought something with ethanol in it...If I'm not mistake, rotating the motor around could cause issues with the transmission or other components? Swear I read that somewhere. If it's all good and I can manage to get the washers that fell into the crankcase without splitting the case then maybe I will go that route.
 

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Discussion Starter #9
As for the .5 over bore, I'll have to see how much the shop charges for that. I'm sure it's not completely unreasonable but have other fish to fry too.
 

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you may have one of the thrust washers break down causing the piston wear... so you may only find 1 being the other one wore out and caused the wear on the piston. debris... ughhh !
 

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As for the .5 over bore, I'll have to see how much the shop charges for that. I'm sure it's not completely unreasonable but have other fish to fry too.
No matter what you do don't put that engine back together with those factory washers inside the piston. Doesn't seem like anyone is selling them on ebay right now but contact Hall Precision Racing in Arizona, he sells them. You need a wristpin bearing from a 1999 RM250 to use with them. It is a bit shorter than the lt bearing and the washers are made to fit it. Those original washers are notorious for breaking and trashing top ends. When one broke on my 86 back around 1990 I had to replace everything, piston, head, sleeve, etc. I've seen pictures where a piece fell down under the crank like happened to yours and it busted a hole in the case halves.
 

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Discussion Starter #12
Wow. How in the hell does one go about removing the needle from the carb slide??? This is a flat slide mikuni and for the life of me I cannot get the throttle cable to release from it's "groove." I can see how it's put together but I'll be god damned if I can figure out how to remove it to access the needle! Help needed and appreciated. You guys rock btw, thank you's all around.
 

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Been a while since I took one apart but I don't remember it being a big deal. Pretty sure you just compress the spring up into your hand away from the carburetor then turn the carb upside down to get that little white keeper to fall back towards the spring then push the cable into the carb a little bit and move it out of the groove.
 

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Discussion Starter #14
You da man Jerkin! I read through many threads looking for that info and found nothing. It looked as if the bottom of the spring was attached to that piece of plastic and I didn't want to pull up on the spring for fear of breaking the plastic stopper cap thing (don't you love my technical wording). The 250 is at the point where I can take the engine out of the frame now. Had the slider (safely) hanging there still attached to the throttle cable and I really wanted to get it out and check the clip on the needle, it's in the 3rd slot which I believe is the stock position (I'll leave it there). The designation on the needle is 6FJ41. I believe that's the stock needle for this Mikuni flat slide carbs?

Now on to draining the fluids and removing the motor. Any tips for plugging the coolant intake on the motor? Like something that could be re-purposed (other than my finger) so I don't drip so much coolant on the driveway? I suppose I could go wander around the auto parts store and see if I can't come up with something. Picking up a telescoping magnet tool (see if I can't get those washers out), impact driver (I'm guessing that removing the stater cover/crank cover won't give me any better access to the bottom area of the connecting rod?). Still, nice to have the impact driver.

What's your take on a cylinder polishing tool? Still don't know if I really want to have to the sleeve bored out but maybe polishing wouldn't be a bad idea and I should be able to do that myself.

The crappy part. I was supposed to be going to a quad jam today but that all went out the window when I found the piston to be marred and in need of replacing. Thanks again!
 

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Discussion Starter #15
Ya know. Maybe I should remove the stater cover and make sure I'm timed right? My hope, have this thing put back together and running like a champ before it gets SUPER cold up here. Again, on the fence with over-boring the sleeve and getting a bigger piston. Any reason I should go that route beyond maybe a tiny bit more power? Is there an after market piston for these with a single ring vs 2 rings? Is one ring better than 2? LOL ok that's enough for now...
 

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Was just getting ready to tell you I think there's a drain plug on the bottom of the water pump cover, lol. Personally, if I had it down that far I'd buy a new piston and have it bored. You're going to need new gaskets anyways, bore job is $50 and you can find a piston on ebay for under $100 but if you don't have the money then you gotta do what you can afford. Not so much about getting more power as it is getting it back in tip top shape. If Nothing else take the cylinder and piston to a shop and have them measure it, I'm sure they'll do it just to get the machine work from you. You need to have it looked at by whoever is going to bore it anyways to see how far it needs to go so you know what size piston to buy (I pretty much stick to Wiseco pistons)

Only access to the crankcase is from the top but probably not a bad idea to pull the stator cover anyways and check the timing like you said. Also see if there is any up/down side/side play on the crank by wiggling the flywheel. It might move in/out a little but anything else is probably crank bearings.
 

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Discussion Starter #18
Engines out. Washers were easily fished out of the crank area once I had the engine out. Still gonna get me one of those magnets for future purposes. There's some horizontal play with the connecting rod but little if any vertical play. Absolutely no gear oil in the crank case however...I'm unsure if coolant is in there. The fuel mix if I remember correctly, with oil added, was sorta blue in color and the mix at the bottom of the crank housing (little puddle) is blue-green in color, and of course the coolant is also blue... Is there an easy way to see if my wet-side seal (believe that's the term) is letting coolant into the crank housing?

Also did notice that there's some RTV (case sealer) that squeezed into the crank housing from the seam, noticed while I was fishing the washers out. Should this be removed? I'm guessing so, sharp little chisel should do the trick. The screws and bolts/nuts have seen much better days and I would like to replace 'em, are the stainless engine screw/bolt sets on ebay worth it?

I'll take the cylinder and piston to the shop today and see what they say. I have the money for bore and piston but don't want to get fleeced and the 250 needs other stuff on top of the engine work. Kick starter pedal needs to be replaced, seems to me there's something going on internally with the kick start mechanism as well. In serious need of re-wiring, the stater wire spades are all rusted and all wires lead to a bit of a birds nest (seriously) electrical tapped/zip tied to the frame, not my style and needs that needs to be addressed. Potential coolant leak into crank housing and I'm sure more to come. Ohh the rear wheels are some fenagled bead-lock deep dish home made things and those are quickly being replaced with some Douglas .190s. AND the rear shock/nitrogen can has to be rebuilt. LOL. Freaking money pit! Love it though.

Well, I suppose since I'm off work today I'll go ahead and run the piston and cylinder up to the local shop now and see what they have to say. Thanks for all the help and advice.
 

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With all you have going on you might want to rethink your original plan and consider taking some time and getting it ready for spring. That would give you time to get some money together or just buy parts as you can, build a leak tester, get the upgraded washers to replace the ones that fell into the crankcase, pick up a new wiring harness (buy them new for $38, not worth screwing with), etc.

Couple hundred bucks and some serious elbow grease and you could have a nice, reliable machine next year that you won't have to work on every weekend before you can ride it.

As far as what's in your crankcase just get some on your finger and feel it, coolant is very slippery, like oil, fuel isn't. If' it's fuel you should be able to smell it too. My bet would be fuel, be tough for coolant to get in there unless you had a head gasket leak and it was leaking past the rings.
 

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Discussion Starter #20
Definitely appreciate the sentiment with waiting till spring, and I'll take my time with the engine, but I'll have her back together and running no later than a month from now, maybe sooner. Found a guy here to do the cylinder and he showed me that it had already been re-sleeved and bored at ~70.3 but that the piston was the stock 70mm likely causing issues with slight rattling and friction in the sleeve. This guy runs a machine shop out of his garage who the big shop I originally went to today uses for this kind of work. Having him order the piston for me as well, cost more but I like to support local businesses and hopefully I can build a rapport with him for future work.

Of course I'm not made of money but the couple hundred (more or less) isn't a big deal. I come from a family with a history of having a need for speed (lol) and right now I'm without my fix, used to race an '87 MR2 (n/a) in local cone track SCCA time attack events and hadn't since gotten that fix until I picked up this quad. Hooked again, what can I say. Can't afford a separate car to work on and race soooo an old lt250r it is....

Should there even be fuel mix in the crank housing? From what I've read, If memory serves, some fuel mix goes into the crank to lube the components?
 
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