KX Riders
Maintenance & Technical => KX500 Original => Topic started by: lsampson on April 02, 2013, 04:09:34 AM
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Hello All,
New to the site, so be gentle :) I have a 1991 KX 500, all stock, that I'm putting a top end into. I have several questions.
1. When I rode it prior to tearing it down, it didn't have much spunk on mid-top end. I checked for exhaust valve operation, and they were functioning. I also cleaned the jets and they were clean. I cleaned the whole carb thorally. The bike was from my uncle, and it should be jetted right, but it is running a 160 main, 45 pilot, with the needle clip set 2nd from top. The elevation I ride is appx. 6000'. I found a jetting chart, and it looks close. The plug is a little on the lean side, but not bad. During teardown of the top end, I inspected the power valves, and they WERE gummy, but still functioning. Anything else I can look at since I'm this far that will solve my flat mid-top end performance? It starts easily, but during deceleration it kind of "chugs" to a stop. Idle is ok.
2. I have read the outline of power valve re-installation, but am a bit confused. I have the powervalve with the notched top pin on the right side (the counter gear side), and aligned it with the rack, aligning the dots. When I fully close the rack (pushed in) the valves expose some of the exhaust valves, probably half of the outer exhaust port.. Only when the rack is pulled out some do the exhaust valves fully close. Is this to compensate for idle RPM, thus pulling the rack out and closing the valves? I have a sneaking suspicion that this is the reason for the ball bearing mod?
Thanks a bunch for the help.
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Maybe stator position. I found this problem when I messed with advancing the timing.
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Actually it is a better chance it could be the kips arm. Here's an explanation of a problem I had with it a while back. http://www.kxriders.com/forums/index.php/topic,9425.0.html
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Thanks Bilger. I'll look into that. Have you torn into the Exhaust valves at all? I took them completely out and accidentally mixed up the right and left valve. There is only one way they can go in and still function correct? The Kawasaki book mentions a right and left for the 125 and 250, but not the 500. The reason I ask is the "barrel" valves seems too far closed with the rack pushed all the way in. At rest, you can see around the valve and into the cylinder exhaust port (one of them anyways) then when you pull on the rack the valve closes the ports, then full open it opens up both ports.
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the left and right exhaust valve of the kips-system had to be fully closed at low rpm. check out, that all valves are fully open at high rpm! if it installed in wrong position it cant work properly.
stator position is in stock the middle of the 3 marks on it.
i think that the old piston already had too low compression. check the motor performance after rebuild again. when piston and exhaust valve work in right order, you can only continue with the ignition and carburetor adjusting.
at last, go with your ignition system to a kx dealer and let it measure whether everything in it works proper.
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possibly a sheared stator woodruff key?
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I don't think its electrical, it starts great and everything, it just doesn't have the 2-stroke kick upwards of midrange, and isn't as wheelie prone as I remember when my uncle had it. The exhaust valves were pretty gummy, so I think it is related to that. They are cleaned up, and I'm hoping to have it back together Friday night.
One more question, for the left and right exhaust valve guides with the rubber o-ring, how often does the o ring need replaced? They appear ok, but I did notice some oil at the gasket when I took it apart. I'm thinking of using silicon around the guides to keep oil off the gasket. I have new o-rings coming, but they wont be here in time for the weekend. Do I need to wait for the o-rings, or can I get by with the silicon?
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the o-rings on the exhaust valves are really only there, that it is not falling out when you pull the cylinder. a little oil there is normal, because the exhaust valves are also lubricated with 2stroke-oil. the o-rings need to be replaced only when the valves fall out when you pull cylinder ...
i think, you should ask your uncle, which jetting and needle position he used, as he rode the bike... this could be the keye to find back the 2stroke-punch out of the middle... :-)
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Thanks motopunk, thats EXACTLY what I wanted to hear! Now I can ride this weekend! As far as jetting, I bought several sizes up for both pilot and main jets, so I will fine tune it this weekend. The plug is a little light brown, so one size main should do it.
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Sampson,
Check the power valve as I'm sure if it's a "91" model they have had a lot of time put on them since new. In the open position, see if the "center" valve lifts all the way up flush to the port window, even if it hangs down just 1mm or 2, it will cause a big loss in top end power. There has been a lot of info posted about the cause & fixes for such on here, give it a search & see if it answers any questions.
Hope it's as simple as this.
DoldGuy
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I don't think its electrical, it starts great and everything, it just doesn't have the 2-stroke kick upwards of midrange, and isn't as wheelie prone as I remember when my uncle had it. The exhaust valves were pretty gummy, so I think it is related to that. They are cleaned up, and I'm hoping to have it back together Friday night.
One more question, for the left and right exhaust valve guides with the rubber o-ring, how often does the o ring need replaced? They appear ok, but I did notice some oil at the gasket when I took it apart. I'm thinking of using silicon around the guides to keep oil off the gasket. I have new o-rings coming, but they wont be here in time for the weekend. Do I need to wait for the o-rings, or can I get by with the silicon?
I had a sheared woodruff key retard the timing approx 30 degrees, thats why I suggested checking it. The symptoms are exactly like what you are describing. Its a simple and easy check to isolate that it isn't the problem.
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Did you check the compression bro?
Low comp would put a hurtin on ur top end bro.
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much luck isampson. want to hear that after the weekend the bike runs well again ... 8-)
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Hello All,
New to the site, so be gentle :) I have a 1991 KX 500, all stock, that I'm putting a top end into. I have several questions.
1. When I rode it prior to tearing it down, it didn't have much spunk on mid-top end. I checked for exhaust valve operation, and they were functioning. I also cleaned the jets and they were clean. I cleaned the whole carb thorally. The bike was from my uncle, and it should be jetted right, but it is running a 160 main, 45 pilot, with the needle clip set 2nd from top. The elevation I ride is appx. 6000'. I found a jetting chart, and it looks close. The plug is a little on the lean side, but not bad. During teardown of the top end, I inspected the power valves, and they WERE gummy, but still functioning. Anything else I can look at since I'm this far that will solve my flat mid-top end performance? It starts easily, but during deceleration it kind of "chugs" to a stop. Idle is ok.
2. I have read the outline of power valve re-installation, but am a bit confused. I have the powervalve with the notched top pin on the right side (the counter gear side), and aligned it with the rack, aligning the dots. When I fully close the rack (pushed in) the valves expose some of the exhaust valves, probably half of the outer exhaust port.. Only when the rack is pulled out some do the exhaust valves fully close. Is this to compensate for idle RPM, thus pulling the rack out and closing the valves? I have a sneaking suspicion that this is the reason for the ball bearing mod?
Thanks a bunch for the help.
When I did my K5 top end a few years back, I had the same exact lazy midrange acceleration as you are describing. I ended up tearing down the top end again, and upon a closer inspection of the power valves, I accidentally had them one tooth off on the timing. The manual is a little confusing, and the pics are not very clear. But in short my valves were both incorrectly partially closed . I'll bet this is your issue.
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Thanks for the reply guys. I've looked over the powervalves closely now, and I have placed a longer bolt to be used as a stopper to keep them from overclosing. Now, with the valve rail pushed all the way in the drum valves close off the side ports completely and are flush with the main exhaust port, and the center valve is all the way down. When I pull it all the way open, the center valve rises to flush with the main exhaust port, and the side valves fully open the two side ports on both sides.
Its crazy how different the powervalve setups are compared to the yamahas. If I remember correctly, the YZ250 of 1994 has just one "cresent moon" valve that is located in the main exhaust port. Not necessarily better, but simpler for sure.
I'm also suspecting bad fuel may have been a culprit on my ride last week. The fuel was a mix of fresh, 6 month old, and ancient fuel. I didn't want to throw it out, but I ended up trashing all of the fuel in the tank. I don't want to run SH*t fuel and always wonder if thats the problem. I'll let you all know after this weekend!
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One more thing, is the stator woodruff key seen simply by removing the left cover, or how would I go about that?
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Well Boys And Girls, I Rode The K5 And It Ran Like A Raped Ape! I Noticed When I Put Her Back Together That The Reed Cage Was Installed Upside Down(The Arrow Was.up) So Between The Valves, Old Fuel, Reeds, And Top End, Something Did The Trick!
But....
I Did Notice That WIth The New weisco Piston, It Rattles Alot At Idle. During Insallation, I Checked The Ring End Gap And It Was Within Specs (0.030"). Do Wiseco Pistons Slap At Idle Until They HeaT Up? It Did Quiet Down Some Once It Was WarM, But It Was Still Present. Thanks Gents.
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Hmmmm.
For a stock set up you are .002" past the service limit:
1987-2004 New .15-.35mm or .006-.014" Service limit .7mm or .028"
I know Motorrad had some problems with getting rings from Wideco that were in spec.
Sounds like that hasn't changed any.
The rattle.... I'm wondering if you could use the kipps bolt mod....
I know my bike needed it after I put in a new piston.
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What was your piston wall clearance..
End gap should be half that.. Makes me think hole is too big... So loose piston wall. Thus. Rattle
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Thats why they call them Wideco now :-)
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Sorry, I Meant .30 mm
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As For Piston Clearance, I Totally Forgot To Measure That. Oops!.I Think I Will Tear It Back Down. The Rattle Is Pretty distracting. I Did Do The Kips Bolt Mod.
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As For Piston Clearance, I Totally Forgot To Measure That. Oops!.I Think I Will Tear It Back Down. The Rattle Is Pretty distracting. I Did Do The Kips Bolt Mod.
kips are noisy anyways.
listen to this one rattle. and I can GARONTEE its right. (beyond right). its shimmed, machined, etc to perfect.
http://s13.photobucket.com/user/Motorrad/media/DSCN1214_zpsa8f1783a.mp4.html
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Man, that thing is crisp....
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Ill have To Listen To It Tomorrow, My Phone Is Jacked Up. The Rattle Is LoUd, Louder Than The Exhaust (At Idle)
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Man, that thing is crisp....
the sound of a perfekt 2 stroke motor... :-D
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Motorad, after listening to that clip, it is the same sound, but mine is louder, and I only noticed it after the rebuild, which i suspect is because I switched from a stock to a wiseco piston. I am not sure what to do. The rattle annoys me, so I'm leaning on replacing the new wiseco with a new OEM piston and rings. Is there any chance that when I cleaned up the exhaust valves I gave them more slop and they are whats rattling? What would you guys do?
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Motorad, after listening to that clip, it is the same sound, but mine is louder, and I only noticed it after the rebuild, which i suspect is because I switched from a stock to a wiseco piston. I am not sure what to do. The rattle annoys me, so I'm leaning on replacing the new wiseco with a new OEM piston and rings. Is there any chance that when I cleaned up the exhaust valves I gave them more slop and they are whats rattling? What would you guys do?
the clean valves will rattle.
if its the same sound as the video. its not piston. (there is no piston to be heard in that video). that is 100% kips ratte.
Mine is quieter than most due to all the work I have done to them.
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what kind of work can I do to quiet mine down? The valves seem good (no excessive wear), but I can move the center valve flapper up and down with the exhaust pipe off. Is that where the rattle is? Do you guys typically use OEM pistons? I just don't want to pass it off as ok and have to rebuild the top and bottom end of the bike because I messed something up :?
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Do you guys typically use OEM pistons?:?
That is a hotly debated topic depending on who you ask.
ask me. Forged only goes back in my bikes.
what kind of work can I do to quiet mine down? The valves seem good (no excessive wear), but I can move the center valve flapper up and down with the exhaust pipe off. Is that where the rattle is? :?
when you say you can move it up and down... how much we talking? 6" or ?
do you have any tension on the kips acuator rod (via the kips arm) ? there should be some tension on the system.
There is lots of work that can be done mine for example, are Re-shaped on the flow areas, the ramp angle is messed with on mine., roughly .030" taken off the top's to pull them higher in the cyl, and everything is shimmed to perfection.. kips acuator rod re-cut, run a differant kips arm for better leverage and ratio for kips bolt mod, as well as a "messed with" kips drum (spring shim stack etc))... Im sure somone will post a link to my motor thread. :roll:
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Wiseco is Forged Correct?
The center valve moves just a little, maybe 1/32th up and down if that. It is the slop where the center valve pins move within the drum valve channels.
I did preload the kips arm, I pushed the rod all the way in, then tightened the arm against the full closed position, which basically happened anyways since the nut forces the rod closed during tightening.
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something just dawned on me, do you think the piston is the wrong size? I ordered a std size from chaparral, and my cylinder has never been bored out, but isn't there various bore sizes? Chaparral OEM says its a "size B" piston..
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something just dawned on me, do you think the piston is the wrong size? I ordered a std size from chaparral, and my cylinder has never been bored out, but isn't there various bore sizes? Chaparral OEM says its a "size B" piston..
This is the reason why usmc 500 didnt ride his K5 for 3 years.
the guy he bought it from put in a fresh piston. and NEVER bothered to check the piston wall clearance.
well. I did once I got the motor.
more info on that subject can be found in usmc500's build thread
needless to say.. Im shocked it never seized...
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This is the reason why usmc 500 didnt ride his K5 for 3 years.
the guy he bought it from put in a fresh piston. and NEVER bothered to check the piston wall clearance.
soo... I should probably tear it down and check piston clearance...? If the wiseco rings were within new spec, shouldn't the piston be within new spec? The wiseco was an 86mm piston, which I believe is standard. I was looking at the OEM pistons when I mentioned a size B piston..
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The heck with it. I just ordered new gaskets, new exhaust valves (both drum and center), new guides, guide orings, exhaust o rings and gasket, and will tear it back down. I will check the piston clearance this time. Should the wiseco piston have the same piston-cylinder clearance as the OEM, or is there a spec out there?
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Typically Wiseco states their PTW clearance on the box the piston comes in. Usually these specs are different than OEM, to account for the different thermal expansion rates of the two materials (cast vs forged).
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So..... I Figured Som Stuff Out Tonight. The Piston That came Out Of The Bike Has A "C" stamped On The Crown, And Fits Tighter Than The Wiseco. I Do Not Have Ash Inside Micrometer So I Couldn't Measure The Bore, But The Old Oem Piston Measures 85.94Mm And The New Wiseco Measures 85.84Mm. The WIseco piston-Cylinder Clearance Is .127 Mm, And Spec Is .100Mm. So I Have A Larger Bore. I Have Not Seen An Oem Piston sold In A "C", Where Are They Available?
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"C" Stands For Cast...Doesn't It... :cry:
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http://www.wiseco.com/ProductSearch.aspx
measure your cylinder and look good in this list, which piston you need . your old size is 85,94, than is your needed size 85,95 in cast!
if you replace a cast-piston by a forged piston you have to know, that forged pistons need more clearance, caused of the different material character. a long time ago i found out that cast pistons with the same mark on the top, are a little bit bigger than forged pistons.
forged cast
- = A
A = B
B = C
C = D ...
feel free to contact wiseco for the right piston size and your problem with the rattling in the motor will be gone forever. than it will sound like a swiss rolex... :-) you heared motorads bike in the video,
the C -size cast piston, you found in your motor you can get at all kawasaki-dealers . the stock pistons and con rods, that kawasaki build in all kx-modells are made by prox in japan, but without the prox-logo in the inside.
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I think what I need is a SLIGHT OEM oversized piston... I'm borrowing an inside micrometer today, so I should be able to get it measured up tonight.
All I can find is 0.50 mm over sizes in Wiseco for over-bored engines (like the link you included), and all I can find in OEM is 1 size, part number 13001A (13001A: PISTON-ENGINE,B) but NO C pistons... :? :?
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I'm going to start a new post..
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you can also use wössner, prox or vertex pistons ... you should take contact to one of the sellers. not all, that they offering is to find on theyre websites...
you could also give a call to an kawasaki dealer.. for an oem c piston...
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I contacted my dealer, and they can only get the same B piston. Same part number.
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I wasnt done typing. read it again
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if you take that measurement. and assume you didnt factor in the measurement for the stock piston wall clearance. you should be pretty darn close. to spec.. off memory. Ill have to go look up what wiseco wants again. but I recall it being .004" (I dont work in metric. youll have to deal with it.)
so. math time.
85.94mm - 85.84mm = .1mm conv to in is .0039".......
lets assume your stock setup had a .0015" clearance.
so
plus the .0015" (theoretical)
.0054"
But this is a HORRIBLE way to check piston wall clearnace. and very inaccurate. as lots of assumptions. and you know what happens when you assume..................
even checking the piston wall with a feeler gauge is more accurate than the way your trying to do it.
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where did you measure the piston BTW?
you know Pistons are egg shaped from front to back right?
measure them, you would find that many pistons are as much as 0.010" out of round. (all bikes)
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sorry about that, so what is the best way to check piston-wall clearance? I used a feeler guage, slid it between the piston and the cylinder on the intake side of the jug, and let to drop to around mid-bore, and came up with .127mm with the new wiseco. The box states .100mm is the clearance on the box.
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I measured on the skirt, 90 degrees from the wrist pin. Thank you for the help. I'm not totally ignorant to this stuff, but this one has me stumped.
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I measured on the skirt, 90 degrees from the wrist pin. Thank you for the help. I'm not totally ignorant to this stuff, but this one has me stumped.
have a camera? Im curious what kidn of shape the CYL is in...
the more and more we dig on this. the more and more you need to go to a local machine shop and have a bore guage stuck int hat thing...
somthing aint right.
or if your local to san diego. We can do it.
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I will try to take a pic, and like I said I'll be measuring the bore tonight. The cylinder looks good. I can still see the cross hatching in the walls in most places, and no significant gouges
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I will try to take a pic, and like I said I'll be measuring the bore tonight. The cylinder looks good. I can still see the cross hatching in the walls in most places, and no significant gouges
yea. lets wait till we have that measurement before we jump to any conclusions.
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Thanks again for the help. I'll let you know what I find out.
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Thanks again for the help. I'll let you know what I find out.
curious. what you goign to be using the bike for? colorado singletrack?
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Just amateur hillclimbing in NW Colorado. Putting around. Thats about it. How did you know I lived in Colorado?
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Just amateur hillclimbing in NW Colorado. Putting around. Thats about it. How did you know I lived in Colorado?
Magic admin tools. :evil:
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Just amateur hillclimbing in NW Colorado. Putting around. Thats about it. How did you know I lived in Colorado?
Magic admin tools. :evil:
motorrad is the man,who knows everything ... :wink:
and i agree to him.first you have to measure your cylinder and then its time to find out the right piston size. motorrad is a great guy and will help you to find the right piston.
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Copy that motopunk. Thank you for all your help as well! Its blizzarding here as we speak, perfect timing to figure this bike out! I hate it when the bike is down and the day is perfect for riding!
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Copy that motopunk. Thank you for all your help as well! Its blizzarding here as we speak, perfect timing to figure this bike out! I hate it when the bike is down and the day is perfect for riding!
you can keep all that white stuff.
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I'm ok with it since I have a 2012 Ski Doo! But I am ready for it to be bike season..
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It's a shame we couldn't take all the information in Motorrad's head and store it in a neatly filed spread sheet form.
Then you could simply click on the info you needed :-)
Like this:
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Copy that motopunk. Thank you for all your help as well! Its blizzarding here as we speak, perfect timing to figure this bike out! I hate it when the bike is down and the day is perfect for riding!
you can keep all that white stuff.
The magnificent white flies around outside :mrgreen:... The winter is the best time to rebuild a bike ... 8-)
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The Cylinder Measures 3.386", Which Is Right On According To Spec. I'm Satisfied. I'll Just Throw the Wiseco Piston Back In With The New Exhaust Valves And Be Done With It. Thanks For All The Help. I Was Probably Measuring The Pistons Wrong And The Rattle Is Probably Just The Exhaust Valves.
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The Cylinder Measures 3.386", Which Is Right On According To Spec. I'm Satisfied. I'll Just Throw the Wiseco Piston Back In With The New Exhaust Valves And Be Done With It. Thanks For All The Help. I Was Probably Measuring The Pistons Wrong And The Rattle Is Probably Just The Exhaust Valves.
as it was. with the other calculations. you were only off by .001" which is easy to blow somewhere without the right tools...
even if it was .001" big.. id run it.
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Yep. I Need To Invest In More Tools! Better SafE Than Sorry I Guess. Thanks Again Motorrad, And If You ArE Up This Way Again, Look Me Up!
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Yep. I Need To Invest In More Tools! Better SafE Than Sorry I Guess. Thanks Again Motorrad, And If You ArE Up This Way Again, Look Me Up!
now....
lets get even more in depth.
what brand base gasket you running?
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:-D Cometic..
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:-D Cometic..
do you see a differance between the one in the lower left corner.. and the rest of them (ones I custom order)?
(http://i13.photobucket.com/albums/a289/Motorrad/Kxmotor%202/DSC_5067.jpg)
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Yep, Smaller Holes For Exhaust Drum Valves!
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Yep, Smaller Holes For Exhaust Drum Valves!
Yep... guess what that does... (look at the title of this thread)
have you read my motor build thread? more info than you ever wanted to know on kips shim'n in there..
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I Assume It Quiets Things (Exhaust Valves) Down! How Can I Get To Your Build Thread? I Tried To See Another Build ThreadThe Other Day But Was Having A Hard Time Finding It...
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I Assume It Quiets Things (Exhaust Valves) Down! How Can I Get To Your Build Thread? I Tried To See Another Build ThreadThe Other Day But Was Having A Hard Time Finding It...
(with a off the shelf cometic gasket and no shims, you are losing 1.5mm of exaust timing!!)
Ill dig up links for ya...
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Right On! Thanks Man! Are There Links To Buy The SHims And Custom GaSkets, Or Can I Buy Them From You?
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Right On! Thanks Man! Are There Links To Buy The SHims And Custom GaSkets, Or Can I Buy Them From You?
Alward25 can get you set up on gaskets.
I used to use shims (as you will see in my thread). but have actually started just cutting circles out of old Cometic gaskets I have around to shim with. as I have found them to be pretty darn close. (for example. my motor right now.. has 1 .020" cutout on one side, and 2 .020" cutouts on the other side.. to make everything happy.
but my drums, base gasket stack, and just about everything else is NOT STOCK.
in USMC500's motor it took just one extra cutout per side.
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I Will Understand More When I Read The Thread, But I Suspect The Shims Go At The BaSe Of The Drum Valves, Where They Rest In The Cylinder, And Move Them Down To Open Up The Center Valve More?
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I Will Understand More When I Read The Thread, But I Suspect The Shims Go At The BaSe Of The Drum Valves, Where They Rest In The Cylinder, And Move Them Down To Open Up The Center Valve More?
they go between the base gasket, and the alum piece's to raise it all up
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Right, I Had It Backwards. :|
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I Will Understand More When I Read The Thread, But I Suspect The Shims Go At The BaSe Of The Drum Valves, Where They Rest In The Cylinder, And Move Them Down To Open Up The Center Valve More?
they go between the base gasket, and the alum piece's to raise it all up
i did the same on my ´97 250 motor a few years ago, as i saw the hanging valves. at least at the dyno +1,5 hp more = 47,5 hp on the rear wheel :-D
for the older kx500 motors 86-88 were only the small holes in the base gasket. why they took bigger holes in base gasket of the newer kx- modells, i will not understand.