KX Riders
Maintenance & Technical => KX500 Original => Topic started by: bjohn07 on January 26, 2013, 01:06:04 PM
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so ive used the search option, got on team green charts and the fmf charts, everything says for sea level to 3k above. im in colorado springs most places around here are 6200-6500 ft. some of the trails i wanna go ride out in canon city can get up to 10k. im just lookin for a base point for around 6500 and i can go from there. the bike has a fmf fatty pipe, smoking normal as far as i can tell but its lagging at top end, and the bottom end feels weak, very weak. any guys from around the same elevation care to share there carb settings. main jet, needle and clip setting, and the pilot jet. im gonna pull the plug and carb to inspect and see what kind of jets are in it now, guy i got it from said it was mainly used in utah and was not jetted for this elevation.
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pulled out the carb. main jet is 162, pilot is 58 and the needle clip was on the 2nd from the top notch? can anyone help me out here.
according to the fmf site (since im running there fatty pipe) my main should be 168 pilot is 60 and clip should be on the 3rd. and thats for 0-1500ft altitude. :-o gonna try to fatten up the jets and see how it does.
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maybe i got this wrong. im from south texas. sea level so im not used to this jetting for elevation stuff. but i might have to go lean since at higher elevation less 02?
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You should really run a compression test 1st,since you say it's feeling quite weak.You can jet and re-jet all you want,but if your top-end is weak,you're just gonna be pissing directly into the wind :cry:.
I've never run at 5k+ elevation,so I really can't say what's a "good" setting,but in my opinion,you're already on the leaner side,with the exception of the pilot.
Just to avoid running the risk of melting the top-end,I would drop the clip into the third(middle) position,and try it.You'll know pretty quickly if it's better or worse.It's better to go a little fatter to start if you're not sure,so you don't melt it.
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You should really run a compression test 1st,since you say it's feeling quite weak.You can jet and re-jet all you want,but if your top-end is weak,you're just gonna be pissing directly into the wind :cry:.
I've never run at 5k+ elevation,so I really can't say what's a "good" setting,but in my opinion,you're already on the leaner side,with the exception of the pilot.
Just to avoid running the risk of melting the top-end,I would drop the clip into the third(middle) position,and try it.You'll know pretty quickly if it's better or worse.It's better to go a little fatter to start if you're not sure,so you don't melt it.
ok. sounds like a plan. what kinda psi should i be reading. also it was rich. i pulled the plug and it is just soaked in fuel and oil.
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found the comp test psi. 105-164. ill be doing that today. also the 2 o rings on the fmf pipe are shot. little oil was coming out so im sure that had an effect on the way it was running. to bad the local bike shop is closed till tuesday.
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See what you get for a compression reading....if it's under 125psi,if it were me,then I'd just yank the motor out of the cradle and pull the jug,send it out to be re-plated,with a fresh piston/rings....and while you're at it,you can check for play in your crank bearings.I'm not saying this is what you have to do...but if it were me,with it being winter,now's the time to freshen things up for the start of the new season :-D
If it still reads well above 125psi...which is what you're hoping for,then I'd be pullin off the carb and cleaning the snot out of that,get a handful of different jet sizes,and take small steps.
Keep in mind too,with it being winter...you are gonna want to be a bit rich....and yes,get the OEM exhaust o-rings,they last longer than the FMF's...and don't be afraid to use a little red RTV to help seal it tight :wink:
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I really can't give you a good starting point for your jetting....as I run in 500-1000ft elevation at the most.I'm sure someone will chime in that can better guide you for your kind of elevation.
Also,what are you running for a pre-mix ratio and what brand of oil are you using?
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I really can't give you a good starting point for your jetting....as I run in 500-1000ft elevation at the most.I'm sure someone will chime in that can better guide you for your kind of elevation.
Also,what are you running for a pre-mix ratio and what brand of oil are you using?
well not really sure. guy i got it from didnt ride much so im more than positive this is old gas. not sure what mix. but if the compression is good im gonna go grab fresh 91oct. and mix 32:1 with benol. buddy told me its good stuff and it adds a distinct smell to the exhaust which will help to let me know if im running to rich. i wont test it out again till tuesday once i have the exhaust orings. so i already pulled the carb last night. im gonna run a cold compression test just to get a base. what should the psi reading be.
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what should the psi reading be.
You already know that answer from one of your previous posts :wink:
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what should the psi reading be.
You already know that answer from one of your previous posts :wink:
ok didnt know if those psi specs are meant for cold or operating temp. but ill give it a shot. thanks for the help
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for warm/operating temp.
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main jet is 162, pilot is 58 and the needle clip was on the 2nd from the top
That should be right for hot mid-summer temps, if your below 70* though take it to 165 , 60-62 pilot. I'm betting its been as cold there as it is here & it's probably pretty hard starting. The 62 pilot where its as cold as it is & maybe even 168 , I know that doesnt seem right at elevation but... colder air is the factor.
I ride the elevation you are talking about, You're really trying to hit a happy medium cause your running such a spread of jetting ranges. There's a nice riding spot uphill from me @ about 6500 ft that I can dial in for there & then go up to 10,500 & tell how close I am. You'll be a complete pig up at 10,500 if your too rich at 6500. At 10-11000 all your going to get is the ability to run at the edge of piggyness. It'll clean out & wont leave you fouling , but if you make it run sweet up high you'll be too lean when your lower. From the 6500 ft "good" baseline you'll feel a slight loss at about 9000 but it will still be rideable up to 11,000, thats as high as I go anyway & it's just crossing over a ridgeline for a mile or 3. My opinion is as you go up the air does cool which helps the spread.
It does sound like a compression test is in order though.
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ok i ran the compression test cold. as i said i dont have the carb on so there is no way to start and get to temp. but it hit 110 cold. thats good enough for me. im sure it will come up some if its at temp.
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main jet is 162, pilot is 58 and the needle clip was on the 2nd from the top
That should be right for hot mid-summer temps, if your below 70* though take it to 165 , 60-62 pilot. I'm betting its been as cold there as it is here & it's probably pretty hard starting. The 62 pilot where its as cold as it is & maybe even 168 , I know that doesnt seem right at elevation but... colder air is the factor.
I ride the elevation you are talking about, You're really trying to hit a happy medium cause your running such a spread of jetting ranges. There's a nice riding spot uphill from me @ about 6500 ft that I can dial in for there & then go up to 10,500 & tell how close I am. You'll be a complete pig up at 10,500 if your too rich at 6500. At 10-11000 all your going to get is the ability to run at the edge of piggyness. It'll clean out & wont leave you fouling , but if you make it run sweet up high you'll be too lean when your lower. From the 6500 ft "good" baseline you'll feel a slight loss at about 9000 but it will still be rideable up to 11,000, thats as high as I go anyway & it's just crossing over a ridgeline for a mile or 3. My opinion is as you go up the air does cool which helps the spread.
It does sound like a compression test is in order though.
ill try this as my baseline and go from there. so what is your air screw set at.
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Back out 2 1/2 & turn it in to where it sounds best. If your getting surge/run on with the 62 go up another size.
but it hit 110 , thats low borderline even cold. Sounds like its due
Before anything else it would pay to go through with a leak down test as low as the compression is
http://www.kxriders.com/forums/index.php/topic,4378.0.html
http://www.kxriders.com/forums/index.php/topic,6608.0.html
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I threw the carb back one. Gonna run it tomorrow and get it up to temp and go from there.
Thanks.
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but it hit 110 , thats low borderline even cold. Sounds like its due
Before anything else it would pay to go through with a leak down test as low as the compression is
+1...just freshen it up now while it's winter....that way you have ALL this upcoming season to ride worry free :-D ...you will thank us!
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but it hit 110 , thats low borderline even cold. Sounds like its due
Before anything else it would pay to go through with a leak down test as low as the compression is
+1...just freshen it up now while it's winter....that way you have ALL this upcoming season to ride worry free :-D ...you will thank us!
so ive never rebuilt a dirt bike 2stroke. not saying that i cant do it, been building small block v8s and hd motors for years. but when you say freshen it up are you mainly talking about ring replacement to help bring that compression up, do the cyclinders use a sleeve replacement or a coating. and the rest im sure ill just try to find specs and replace bearings and such as needed. any top end build kits you would reccomend as far as brand?
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If you can rebuild a s.b. v8,you can easily rebuild a two stroke!.Here's a little helpful info,courtesy of the site.
http://www.hallbergs.net/kx500/
I would pull the jug and inspect the nickel plating for flaking and wear...but it's sounding like you need a re-plate and new piston/rings...at least that is the way I would go.And while the jug is off,you can feel if there's alot of slop in the crank bearings...good chance there is...which means splitting the cases...and if that's the case,you might as well do a complete overhaul...which would run roughly about $1400,give or take.I know this is probably NOT what you want to hear...and I'm just basing this on "worst case scenerio"...there's a chance you might be fine just getting the jug re-plated and new piston/rings/gaskets for $600 give or take.I don't think just replacing the rings is gonna be a good solution,I'm thinkin "mo money".
These guys do good re-plating..
http://www.powersealusa.com/
...and they will/can supply you with a piston if you ask for one.I myself,and a few others on here are running Wossner pistons...and I've had excellent luck with it.
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If you can rebuild a s.b. v8,you can easily rebuild a two stroke!.Here's a little helpful info,courtesy of the site.
http://www.hallbergs.net/kx500/
I would pull the jug and inspect the nickel plating for flaking and wear...but it's sounding like you need a re-plate and new piston/rings...at least that is the way I would go.And while the jug is off,you can feel if there's alot of slop in the crank bearings...good chance there is...which means splitting the cases...and if that's the case,you might as well do a complete overhaul...which would run roughly about $1400,give or take.I know this is probably NOT what you want to hear...and I'm just basing this on "worst case scenerio"...there's a chance you might be fine just getting the jug re-plated and new piston/rings/gaskets for $600 give or take.I don't think just replacing the rings is gonna be a good solution,I'm thinkin "mo money".
These guys do good re-plating..
http://www.powersealusa.com/
...and they will/can supply you with a piston if you ask for one.I myself,and a few others on here are running Wossner pistons...and I've had excellent luck with it.
BIG X 2
Replate , piston, main bearings & seals if your lucky . You will be happier with a good running bike over a mostly worn out 1
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thanks for the info. i didnt think it would be that much. if im gonna pull it apart i might as well redo it. i might just wait. got a deployment coming up so it will prob be after that.
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holy moly! :-o i used to pay 250 to get all 8 sleves coated and honed and pistons coated for nitrous. granted it was 5 years ago i was expecting it to be 70 most for a single cylinder at the most. looks like i better start putting aside a rebuild fund. might as well do it right.
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holy moly! :-o i used to pay 250 to get all 8 sleves coated and honed and pistons coated for nitrous. granted it was 5 years ago i was expecting it to be 70 most for a single cylinder at the most. looks like i better start putting aside a rebuild fund. might as well do it right.
Now you're talkin..."do it right"!!
One more thing you will not want to skimp out on...is a GOOD pair of riding boots,you'll need em to kick over a fresh K5...or...the consequences could be quite painful!
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So got my new exhaust orings on. New fuel and air filter. Didnt start it. It was in the 20s and 30s yesterday. But after putting fresh gas and the carb back on i noticed a steady flow of fuel out the bowl overflow? Makes me think the float is sticking or height is wrong. what is the height supposed to be?
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compression psi at temp was right under 145. with the jet change, (carb was pretty clean already) and a float height adjustment, new plug and air filter the bike is running like a 500 should. wheel up, going sideways in dirt. feels right. got the exhaust o rings changed also but it is still leaking oil from the weld at the front mount. probably gonna jb weld it and call it a day. a little bit of surging only in neutral, not sure if this is a carb issue or a cable issue. but i cant adjust the idle at all. not sure what the deal is.