Take a look at this topend...

[SoFlo]

These are just some pics of the topend on my bike, I'm thinking of going ahead and pulling the cylinder and putting a new piston on it. How does the plating look? You can't really see any hone on it, but there's not streaks either. Does it look like it's burning tranny oil or doing anything abnormal? Because it's fouling plugs every 30 minutes, and can't really see why, since the bike runs awesome I think.

 

[SoFlo]

Or try this link, http://www.imagestation.com/album/pictures.html?id=2109474475

 

[nickyd]

I'd have it honed for starters - and measured. fouling plugs.....can we see the underside of the piston? are you losing tranny oil? I'd suspect the clutch side crank seal if you are fouling plugs - assuming your jetting is fine that is

 

[SoFlo]

Sure, I'll take the cylinder off. I was planning on poping on a new piston.

 

[SoFlo]

Alright, I poped the cylinder off, and right now I'm cleaning the powervalve. I had the cylinder tilted over in my hands, and all of a sudden there's a pool of black oil puddling up, I mean a lot. Is that normal? And of course the powervalve was dirty, not carbon or anything hard, just mostly slick black oil, and a little of the more gummy stuff. Do really oiled up powervalves cause plug fouling? The piston itself looks fine, no scoring. There is some burn marks near the exaust though. I'll have pics up soon, it's almost dark.

 

[QKENUF4U]

what ratio are you mixing at ? what kinda oil ? what gas ?
if anything i would say you are on the EDGE of being LEAN. that piston looks like my buds RD400 piston that now has a nice hole in it from a 5th gear missed shift. (leaned it out on over-rev)

 

[SoFlo]

I've been running Belray synthetic at 32:1 with regular pump 93. What kinda problem will lead to the engine running almost lean, yet fouling plugs like crazy, that's what I don't understand? If it's not getting too much oil and gas, is tranny oil getting in, or old powervalve oil?

 

[nickyd]

p-valves can be gooey - not to be overly concerned there - how are you fouling plugs? explain it - I had a 96 RM 250 and if you didn't warm it up properly and you blipped the throttle too soon - forget about it - she'd do the BAWWWwwwwwppppp and not start unless you changed the plug - you put in a plug and BOOM, it starts 1st kick....I thought it was the top end - pulled it and everything was fine - tweaked my jetting and the problem lessened - then I finally changed the clutch side crank seal...and subsequently sold the bike - hope you didn't end up with it!! anyway - those bikes are notoriously hard to jet.

 

[SoFlo]

As far as how it's happening, if I ride hard and fast for a while, like blitzing through trails in 1st, maybe 2nd, and I come to a stand still or slow down, that'll probably foul my plug if it's been in there for 30 minutes. Also, if I'm riding WOT, let of the gas, come to a stand still, it'll usually foul right as I'm taking off again. Sometimes, it's just normal riding, and if I shut it off, it won't start unless I got a new plug. Also, it loads up very easy when warming it up. As far as the bike starting with a new plug when warm, mine is usually a one kicker too, though it's been getting a little harder these past few times.

 

[muddy226]

If I remember rightly my 96 had one of those dreadful combined choke/idle knobs, and unless it was turned right down would cause rich running right at the bottom, I believe I ended up running it turned fully in and went a lot weaker on the pilot jet. I still have an old piston out of that bike in the garage, and it looks just like yours. I'd say it was pretty much spot on and has a good burn pattern, but if anything a little rich, but not by enough to try and mess with. As someone else said, those motors were very difficult to jet, and my problem was always to get it lean enough. I think your problem is almost certainly to do with jetting at the bottom end of the circuit.

 

[sick 96 250]

if your bike was ran lean before you got it but then the jetting was fixed it could still cause you to foul plugs all the time. Your piston is prob done. Its exactly what my 96 rm250 was doing. Get a new piston and rings, take a brillo pad and lightly scuff up the cylinder walls, just get all the excess crap off there, put the new piston in and go to something around the stock jetting specs, i believe in your other thread i told you what i was running after i did the top end. I bet you after this you will be fine. And i am still trying to locate that gasket kit i have laying around, my garage is a mess. the sooner you get this done the less you will be confused on this whole topic :laugh:

 

[jumpingjoe628]

Hows the coolant level been? Usually there should be at least a little carbon built up on the dome of the head. Mine did the same thing and it turned out to be a head gasket leak. After warming up the bike for a couple minutes, if I opened the rad cap the coolant would be real brothy and foamy with a slight sweet smell to it. The head might be getting washed off from coolant introducing itself into the combustion chamber. When my bike was only 6 months old I did a topend inspection and there was a little carbon built up on the dome, which is normal. But after I overheated one time when the plastic tee for the rad hoses burst, the head had warped and in turn ruined the cylinder as well. I had to get a new cylinder after it cracked at the base mounts. Just something to think about. Good luck.

 

[SoFlo]

Oh and by the way, the piston underside is clean, not a speck of gunk sitting there. I snagged a piston off the site for $30, it should be here soon. I cleaned the powervalve too, I thought it was kinda fun actually for some reason, a nice little challege. I've got plenty of pilots below 52, everything down to 40 or so I'm preety sure.
Once you find that gasket kit, send me an email or something, toomeyb12001 at yahoo.com.
And I do have a choke/idle knob on the carb. I have it turned all the way down. If non of this really does much, I'll keep an eye to see if I'm losing any tranny oil. Do people ever put on PWKs from later model bikes on there? I'm sure routing the throttle cable or the cable opening and closing the carb isn't much of a problem? I might do it one day to make things eaisier.
Aside from stopping every 2 seconds to change a plug, I'm preety happy with this bike. It does use a lot of gas though, compared to the Blaster that I used to ride. But this bike's power and suspension are incredible compared.
Oh and one more thing, I've gotta set of I think V-Force 1's on this bike. The cage is black instead of grey like the 2s. Anyways, I can see about 2 page thickness gaps in about 1/3 of the reeds. I have a stock cage with brand new reeds too. The stock one does look more resticted, but I've got new reeds that don't cost $70, and I'd like this bike to start easy cold. I think I'll try the V's with the new topend, and if it's still a hard starter when cold, I'll pop on the stock cage with new reeds. I've got one of those clearance tab tool things (forgot what they're called), and I could measure it if someone knew the exact #'s.

 

[SoFlo]

I should have taken a pic right after pulling the head. There was a little bit of greenish sitting on the oring, maybe I'm getting a little leakage... I've got some new orings coming, hopefully that'll stop the problem if it's there. I never thought to open it while the bike was running, always to afraid it would blow up! :ohmy: But if it's not warmed up fully, I'll check that next time. My nose doesn't really know all the smells for different chemicals on the bike though. :ahhh:

Hows the coolant level been? Usually there should be at least a little carbon built up on the dome of the head. Mine did the same thing and it turned out to be a head gasket leak. After warming up the bike for a couple minutes, if I opened the rad cap the coolant would be real brothy and foamy with a slight sweet smell to it. The head might be getting washed off from coolant introducing itself into the combustion chamber. When my bike was only 6 months old I did a topend inspection and there was a little carbon built up on the dome, which is normal. But after I overheated one time when the plastic tee for the rad hoses burst, the head had warped and in turn ruined the cylinder as well. I had to get a new cylinder after it cracked at the base mounts. Just something to think about. Good luck.

 

[SoFlo]

In this pic, the inner oring is green, not sure if anyone can tell whether that's normal or if it's like coolant of something. I already cleaned everything and all, I don't remember how it was exactly.

 

[sick 96 250]

thats prob just the color of the oring thats in there. i think i know where the gasket kit is, have to check tomorrow AM, hopefully if its there i can get a hold of you and we can work something out so i can ship it to you ASAP. I believe as well once you get the new top end in the stock idle/choke knob should be turned about 6.5 turns out from bottom. I really think you had the same issues i had when i had my 96 with it being jetted wrong for a while then corrected but the damage was already done to the piston and rings, at least you didnt have a melt down. I will keep you posted on the gaskets.

I found the gasket kit but its for a 99-00 rm250 and not 96, i thought they were the same but the 96-98 have different part numbers. rockymountainmc dot com has a kit for you for $30

 

[apb]

Do people ever put on PWKs from later model bikes on there? I'm sure routing the throttle cable or the cable opening and closing the carb isn't much of a problem? I might do it one day to make things eaisier.

Yes, I put a pwk38 on my RMX250, and I was amazed how much cleaner the bike runs and idles, and how much easier it is to get the jetting right. Its a drop-in replacement, and I'd highly recommend it. They came stock on many 250 mx bikes, so they're easy to find on the auction site used if you dont want to cough up the big bucks for a new one -- mine was like $35 off a '97 kx250.. Best to get one with out the powerjet solenoid thing for older bikes like ours, but I've heard you can switch needles to work around that if you need to.

 

[SoFlo]

Will keep an eye out, thanks...
How different does the jetting end up, not more than a few sizes I'd guess.

 

[apb]

Well, I was coming from a mikuni tmx carb, so I can't compare with the keihin jets. But on the pwk, I followed some advice I received and started with the jetting that was stock for the bike that carb came on ('97 kx250 in my case). Then I adjusted from there -- it didn't need much changing, really. Right now I believe I've got a 42 pilot and a 165 main in there, but obviously, those could end up different for you with your motor, elevation, temps, and whether or not you have aftermarket reed valve and exhaust..

 

[BlackS84]

I agree with nickyd about the clutch side crank seal. Couple questions: Does your bike smoke still when warmed up? Does the exhaust smell like burning crankscase oil instead of gas and two stroke oil? Does the oil level drop after one or two rides? Does your coolant look milky and darker than normal? Does anything come out of the crankcase breather tube after one ride ? If you answered to these questions as yes its most likely the crank seal. What normally happens is the oil seal for the coolant impeller starts leaking and then the pressure from the coolant system starts blowing coolant into the crankcase and then finds the next path of least resistance, either the stator side seal or the clutch side seal. Hope this helps!

 

[SoFlo]

--Does your bike smoke still when warmed up?
--Does the exhaust smell like burning crankscase oil instead of gas and two stroke oil?
--Does the oil level drop after one or two rides?
--Does your coolant look milky and darker than normal?
--Does anything come out of the crankcase breather tube after one ride ?

It smokes very slightly, I'd honestly say like a normal dirt bike. Deffintly not any huge white clouds or any of that.

The exaust smells like good ol exaust, unless I'm more of a newbie that I think, and it does in fact smell wrong. To me, it smells exactly like any two stroke oil, when I smell a weed whacker, it reminds me of my bike.

The oil level I'm not sure of, I'm going to check it soon. When I first got the bike, it was a little low on oil, but recently I've changed it often, and not really checked it. I'll check it the next time I get some good couple hours on it.

The coolant looks perfect, stays filled up, doesn't boil, no darkness or milkyness. Just nice neon green.

I'm not exactly positive which hose that is, but I'm basically positive that I know which it is. I've never had anything come out of it. On my bike, it's right above the powervalve on the right side of the engine. None of my hoses spew much. My powervalve hose splurts a little bit, I notice it becuase there's a crack in it, and it gets all over the left side of the engine on long rides, but it's not really that much oil.

 

[souphmars]

mna it is the jetting - u got to tinker with it to u get it right - i got an 02 rm250 with a FMF SST and v-force - it would drip oil out of the exhaust but it would not foul a plug - but if i stayed on the main constantly like in sand or during a race it would look good - so i moved the clip on the needle and did some adjusting with the air screw - helped a little, but plug was still black - so i put all that back when i changed the top-end about a month ago, and went down 1 jet on the pilot - it runs a ton better now - way more crisp - i already couldn't wait for racing season, and this makes me even more excited - but a new top end in it and put the factory jets in it, and go from there - depending on where u live, u will probably at least have to go 1 leaner on the pilot and main - don't give up - just keep working with it - i had a 98 yz250 that had a simliar problem but way worse - i sat down 1 day and worked on the carb, and finally figured it out - iw ould put a jet in it and then go for a ride - i did this overe and over all day until i got it right - that bike was a totally different bike after that - then i sold it for the 02 rm250 nad have never looked back - good luck