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Found 109 results

  1. So I have a 1998 Yamaha Yz80, and I need a new top end. I found a 2002-2017 Yz85 piston kit, for a very reasonable price, and I was wondering if it would be able to fit my 98 Yz80? Would the piston, wrist pin, bearings, rings, Etc be able to fit? And will it work?
  2. A 1994 KX125... This is my first 2-stroke (and a new purchase for me), i was told by the previous owner that the oil from the exhaust was a sign that it needed a new piston ring. Replaced the piston and ring and now the bike bogs down bad from a stop/very low speed while in first gear. New piston and ring (Wiseco spec sized for the year but is flat while the original one was crowned) Cleaned the carb (42 pilot jet with a 158 main jet) 800' above sea level Reeds look great Repacked the FMF silencer (still have oil out the exhaust so I know its running rich) I just can't figure out what else to do or check. The bike has great pull and power in the upper RPM range of first and all through the rest of the gears it pulls strong. Just looking for something that I might be missing. I have been searching this forum along with others for an answer to the issue I am having but have been unlucking in finding any leads...
  3. I recently purchased a 2010 KX250F from a friend of mine that had been sitting in his garage for about 5 years. The bike seemed to be in decent shape and the price was right so i picked it up. I went through most of the bike before riding it (air filter, oil, greased all the bearings, adjusted suspension, changed all the fluids, etc) The valves sounded a bit loose so i decided to have a "Buddy of mine" adjust the valves. I get the bike back, go for a ride and the cam chain tensioner falls out while i was riding, luckily i caught it very soon after it happened and it never jumped timing. I put the tensioner back in and continue to ride the rest of the day. as the day goes on the valves sound much looser than they were originally before the adjustment was done, I decided to call it a day and tear the bike down myself. I shim the loose valves and button the bike back up, but now the thing sounds god awful. Straight up clacking coming from the right side of the top end. Since then ive probably had the bike apart and back together 4 or 5 times trying to figure out the problem. Its not the auto decompression valve, every valve is in spec, timing is solid, and the cam chain tensioner is working fine. I'm stumped. anyone have any thoughts?
  4. Hi All, I am going to be rebuilding the top end of my '07 DRZ 125L. I am what most would call a complete novice when it comes to rebuilding engines and am just looking for general information on parts required and any other things that I could need or would be helpful. I am also considering putting a bbk 150cc on it when I do the rebuild, Any thoughts? Thanks.
  5. 2008 crf250r, in the process of finishing up a top end rebuild, and after installing the timing chain onto the cam I deciding to hand crank the engine slowly with the kickstart to see if everything was alright. There is a distinct knock that sounds like it is coming from somewhere in the cylinder each time I turn the engine over. What would be causing this sound?
  6. I have a bike someone gave me thats in pieces and I have a good 426 bottom end and a good 03 450 top end. Can I put these together and what if anything would I have to change?
  7. Hey i have recently acquired a 2000 kx 125 and i just found out it has a big bore 144cc kit and i need to buy a piston for it. I have searched and i cant seem to be able to find one. Where do you purchase those.
  8. Hi everyone, My yz125 has 22 hours on the current top end and 77 hours on the cylinder and I took off the pipe to fix my radiator hose and figured I might as well take a look into the exhaust port. I run a double ring forged piston from wössner and it still has the machining marks that hold the oil and it still has the black coating so it looks very good as far as I can tell. It doesn’t show any hotstreaks is what I’m trying to say 😅. The bike has good compression as far as I can tell by pushing the Kickstarter down, it starts first kick and runs strong 💪. I did however notice that there are black horizontal marks on the cylinder wall above the intake port. I attached a pictures so you guys be the judge, is this concerning or nothing to worry about? Thanks!
  9. OK here goes... Picked up an 04 200 EXC few months back, needed some work to say the least, wont go into detail of all the things i've fixed on the bike just the current and most present issue I cant seem to fix... it is smoking IE blue smoke/lots of splooge to the point that at the end of a few hour's ride, it's out the tail pipe, running down the back and dripping onto the swing arm/rear break caliper and blue smoking quite a bit. When I first got it, it smoked more and smelled like shit. So first things first went to the carb, I live on the Oregon coast (elevation/temp reference) it's old dirty/stained but inside looks good, came with jetting pilot-45, main-178 needle: no idea what brand guessing stock in the 3rd clip, adjusted the float height due to it leaking gas when bike was upright no tilt with the gas on, Bought JD jet kit and running pilot-45, Main-185 and Needle is blue 3rd clip (JD's recommend specs for my bike @ my attitude). I have also replaced my Inner crankcase seal twice (First time I thought I messed up the O-ring so redid to make sure). I've rebuilt the top end/new piston (same thing) cleaned the PV, NOTE HERE that the PV has some issues, it seems to work fine but the screw that goes on top of the cylinder, down into the PV/flap would not come out preventing me from removing the flap to clean it, however it move's/ function's correctly, and has minimum clearance on both sides. One of the PV cover bolts that also works at the exhaust spring holder, was over torqued at some point (impact driver prob), or a result in a hard impact, the hole the bolt goes into is flailed/jared open a bit, not bad, not in the way of any function/ PV Gearing/hinge, it is not needed for that area to be air tight as their is also a breather that goes out of the PV so will not result in an "air leak" or loss in Top end PSI.... anyway... it's still smoking.... quite a bit.. now the bike itself rides fine I feel, the carb does puke gas when tilted over slightly/ hard to start (kick start) after flooded (like all bikes tho) I don't have any stalling/low idle issues outside of user error on clutch control. Honestly outside of it smoking as much as it does I would think nothing is wrong with it.. I have also tried raising the needle Clip to 2nd clip and it changed nothing at all, not even feel of the bike/response and have a new Spark plug I have yet to put on the bike. I have also "compromised" the crankcase Gasket (new one in the mail) while I was putting the Crankcase back on but that should do nothing with the exhaust just a little gear oil leak not relevant but throwing it out there. So I am at a loss... I've been toying with the idea of getting a Lectron carb... However... would hate to drop $400~$500 and the issue still persist, if it's a jetting/carb/float issue that would fix it and improve MPH/fuel consumption Or something with the PV? but I don't see the PV causing that much smoke/sploogee... I've ridden the bike normally/hard and nothing's happened but I don't want to keep pushing it and possibly clip the bike. Any ideas? "Oh help me 2 stroke community you're my only hope"
  10. Hi I just done a top end rebuild and a few other bits too my bike change the clutch cable,got it started sounded like a ticking sound coming from the engine after listen for a minute I think it’s coming from around the clutch area and it starts to tick faster if I rev it ? I disconnected the clutch cable and still was ticking. Even if I push it with the bike off I can here it . The bike won’t go into gear at all now it feels as if it’s half in gear and then clicks out any body able to help me ? New here thanks 😃👍
  11. Hi guys, I’ve got a 2005 kxf250 here and Im concerned about how oil is fed from the bottom end to the top end ... anyway I bought it blown up... I’ve had to buy new bottom end casings, new cylinder head new valves all that lot.. but once it was put back together and oil was put in, I went to re time the bike and noticed there was no oil by the magneto hole, I took the side cover off to inspect whether oil was actually in this side casing where the conrod and big end bearings sit and there’s nothing? But normally oil is fed through the timing chain to the top end isn’t it? you can clearly see by the sight glass there is the right amount of oil inside there (not to mention I measured the amount of oil I put in anyway) I’m just wondering if there’s another oil top up point I’m struggling to find or is this just how the bike is? Because there is two oil drain hole plugs so it’s just a thought, any advice will be appreciated!!
  12. okay, so I recently rebuilt the top end of my 2007 yz250f as it went out on a ride. Anyways during the winter it was taken out of the garage and and started for about 2 minutes before it "seized" At least that's what I thought until I took it apart. The kick starter was stuck and wouldn't move and after I took the top end off I saw that the crank was stuck and I was able to get it moving again. So the cylinder was still in good condition and has no big scratches, and now the crank is moving freely as it wasn't before. Is this a simple top end job and I must've not put it back together correctly or is it something deeper involved? Thank you, any input would be appreciated.
  13. This is my first top end rebuild. I just got the head off, cylinder and piston removed. There's definitely some wear on one side of the piston and cylinder. I'm replacing the piston, rings and head with a VHM. Should I be concerned about the wear in the cylinder? If so, would scotch bright suffice? Also, I gave the bike a good cleaning prior, but as more and more parts came off, it was apparent that things were still a little dirty. Can I clean the cylinder prior to putting it all back together. Lastly, the cylinder bolts were pretty corroded; well at least 3 out of the 4 were. Should I wire brush these? It'll be hard to keep junk from falling into the bottom end... The bike is a 2006 RM250 Thanks
  14. I just rebuilt my kids 2013 YZ-125 that I had the cylinder professionally oversized by 2mm from Millenium Technologies last year. It made it a 134cc. I just rebuilt the motor for this season, I had MT-LLC re-plate the cylinder and match it to a new piston. I also had them deck the head for race gas only. My sqush is at .038. I plan on running race gas (sunoco 110 non oxygenated) at 32:1 with Redline (which is what I ran all last year). Here is where my concern begins. I did a compression test and it is right at 220psi. Will I be eating main bearings quickly? Will this motor hold up for a season with exceptional maintenance? Should I advance my timing about .002 to compensate for the high compression and reduce the pressure on the rod? I was told to simply double the base gasket and it will work. IF I do that, What will that do with the timing and jetting? Just a little out of my league with this much psi..... Please help with ideas. Thanks.
  15. My brother was rebuilding my top end for me on my 2002 yz250, and due to a failure on his torque wrench, he over tightened and snapped one of my studs . Now i only have 5 of 6 working bolts on the cylinder head. I have 2 questions. We are supposed to be leaving for a 5 day riding trip in a few days, so we don't have time to order a new one. A: can I achieve enough compression and avoid any disasters for one week without 1 of the 6? b: There is a pretty awesome machine shop by his house that may be able to make us one, but I can't locate the specs. Does anyone have the exact specs for a 2002 yz 250 cylinder head stud? Any and all help would be much appreciated.
  16. Hey, I picked up a 96' cr125 off Craigslist for pretty cheap. Learned my lesson from my last two stroke- gonna do a rebuild before I crank her up again... Anyways, pretty sure the bike has "piston slap" noise coming from the motor. I looked it up on Youtube, sounds like what it is. Is there anything special I need to know before I do a top end? I'm still a fairly inexperienced mechanic, but as far as I know, I need to get a bore-measuring tool and measure the cylinder bore before I buy a new piston. They make slightly oversized pistons for this kind of situation, right? I'll post pics sooner or later. Just gonna keep digging this thread up. Let me know your thoughts! *Edit*- The bike can roll in second gear. Noticed it when I was buying the bike. When I pop it in gear to rock it back and forth before I start it cold, it'll just roll through and you can hear the engine turn over. My guess is this is a symptom of a roached top end.
  17. Hi all - So I have my friends kids 1991 JR80 that needs a top end. (I dont think they ever ran mixed fuel) Its got about 30 PSI in the cylinder and from what I could see through the exhaust port, it was looking pretty bad. Looking for a top end kit, cylinder and all. So my question is... is the LT80 and JR80 the same engine? Will a LT80 top end kit fit the JR80? Having a hard time finding a JR80 specific kit. Anyone have a suggestion?
  18. Recently changed the cams to hotcams without checking the valve lash like an idiot. Went to change the shims and couldn’t get one of the barrels back on. Looks like This. What’s my best option? Buy the oem pieces for this one valve or buy a whole new forged set?
  19. I just bought a 1999 kx 125 and wanted to inspect the top end so i took off the pipe and looked through the exhaust port and saw the images below, I am new to this but i think that that is blow by meaning i could use a new top end. What do you guys think that I should do, if anything?
  20. I just put an fmf powerbomb on my 2006 yz250f and started it up a few times and have began to hear a slight tick in the top end. I also turned the bike over maybe 20 times without starting it to test for air leaks in the exhaust. Could this have caused too much back pressure and thrown off my valves? (the muffler plug WAS in). I know the normal 4 stroke engine noise, but this doesn't sound too normal. Could you guys take a listen and let me know? Hoping it's a normal sound. Any help appreciated! Video of sound:
  21. Hi all, I’m doing the top end on my 300 tpi 2stroke and I heard the circlip openings should be at 6 or 12 o’clock. Mine is at 2 o’clock and I can’t get it to turn. Should I just leave it?
  22. Hi everyone, I just did a top end on my yz and it runs 🤗 , I ran it just above idle for 2-3 minuets for the heat cycle. but I still have a few question: when I cleaned the cylinder head I noticed ever so slight detonation on it, what can be the cause of this so I fix it before it gets worse? I run 32:1 with 95 pump gas, I run a br9evx or something like that it’s the one the manual recommends. Or did compression just get too low at the end? when I put the cylinder on it was quite hard to compress the rings and put it over at once, the rings have to be compressed at a certain spot at the back and I am not sure if I perfectly did that. Like if it was perfectly compressed and the gap Should be at that spot but I don’t know if it was exactly there. But the cylinder went on just fine, it has compression and startet so it’s probably good right? is it normal for the forged piston to run a bit louder than the cast piston, in the 3 minutes I ran it I noticed that the engine was just making louder noises than before, like the same sound of the cylinder but louder. I switched from the stock single ring cast piston to a forged double ring piston in case anyone is wondering. also I’m planing to do 2 more heat cycles, then ride it easy for 30 mins, medium/normal for 20 mins and then go through all the gears pinned to make sure all is good. So 1 hour brake in. Is that good enough? thanks!
  23. I bought a "2000" yz125 from someone. Shortly after purchasing the bike, I checked the vin and realized it is actually a 1999. Off to a good start. The previous owner told me he put a new top end in the bike and saw the clearance value of 0.002 inches on the wiseco piston box, so he thought that meant to bore the cylinder out the much... no big deal, its a pretty insignificant amount. I start the bike up and ride it around, but it has practically no power at all. It revs up fine on the stand, but it has absolutely no power when riding. So I started checking stuff. The power valve actuator arm moves when the revs go up, good. The valves themselves are new (he also replaced the entire assembly). The valves do no stick, and they move with the actuator, so I know that is working properly. Next I check the reeds, they are not damaged at all. Then I check the exhaust. It does not appear to be blocked anywhere, so thats out of the question. Then I do a compression test, and it comes out to 105 psi... found my problem. I'm just not sure why it has no compression with a new top end. The clearances between the cylinder and the piston look good, and the ring does not appear to be damaged (I have not take the jug off the bike yet). The cylinder walls looks bad though. There is no visible crosshatching, and there are weird patterns in the walls. The previous owner took the cylinder to a friend of his to remove that 0.002 inches, so I'm assuming he did not hone the cylinder properly. I'm kind of at a loss, and I don't want to replace the whole top end again. I am attaching pictures of the cylinder and a view of the piston and exhaust valves from the exhaust port. Does any of this look right? Also, he said that he lost the "top cap" when doing the top end. I assume that means the head because the motor mounts don't line up properly. He said he took a "top cap" from an rm125 or something that was laying around the shop, so I'm thinking that could be a possible culprit for the low compression. Any insight is helpful. Thanks.
  24. let me start off by saying, that i am a long time reader, but have never posted until today. I HAVE SEARCHED EXTENSIVELY. all over. i have done multiple fixes and changes. but, here we go... I road race in a mini bike series. kx65's are ultra popular and competitive due to their cheapness, speed and weight. I have a kx65, my frineds have kx65's, everyone has kx65's! lol My kx65 however seems to have no top end power. I can run lap times close to 2 seconds faster on our endurance bike (which i dont own), and I can always really feel the top end pull on it. Both bikes are modded exactly the same. except one runs race gas, mine does not. I have ridden other peoples kx65's and their bikes also make more top end power than mine does. What its doing is it feels like the top end just flattens out and tapers off right when it should be at peak power. It doesnt bog, it doesnt stutter, it just flattens out and makes no power where there should be 2-4k rpms of more power band. MODS MADE TO BIKE -wiseco 46.5mm piston (72cc), GENUINE keihin pwk28 carb - 132-148 main tested. float level set to factory specs, 42 pilot is golden, clip set to third position, off idle is beautiful, mid is great and will power wheelie shifting from first to second. vforce 3 carbon reeds. moose intake spacer, dent free factory expansion chamber, brand new pro circuit pipe. -crank, piston, and main bearings have 10 hours on them. rings have maybe 1 hour on them, plug color with WOT plug chops in fourth are kinda ehhh, not dark, but not light, but i can never jet it to the point of it being brown on the main jet. i have as of today ordered a 130 main jet to try even leaner settings...color largely remains the same no matter what, power is flatter with richer jetting things ive done to try and recitfy this issue -new crank seals, split case and resealed it, new piston rings, performed leak down test, held pressure except for at the plugs on the leak down tester. confirmed with soapy water... jetted and jetted and jetted. confirmed timing position. 120psi of compression on brand new rings...maybe they just hadnt seated yet?, new dent free expansion chamber, new head gasket, pit free head, confirmed squish at .65mm at all four corners. squish is however tighter right at the edge due to head gasket being slightly smaller due to 72cc piston (everyone else i race with is like this too though), what else...checked coolant system, no leaks, holds water over the course of a race weekend. last year i ran a grom, it was a pig, i wanted to get results and lap times like i had on my buddies 65, so i got a used clapped out 65 and built it. so here we are...makes great bottom and mid power, falls flat on the top, doesnt bog, doesnt stutter, and my gearing is a little bit shorter than some peoples. i get plenty of drive off of other riders on the corner, but they catch, pass me on the striaghts. when trying to pass people, i suck up on them on the brakes and in turns, then they leave me on the straight. its been half a season of me not getting results and im getting heavily annoyed... am i simply running out of my powerband and its being exacerbated by slightly shorter gearing? is my clutch slipping and making it feel like it doesnt build anymore power, but the motor isnt really increasing in revs...is my stator or coil going bad? who knows. im sure its engine related... any more ideas or questions and i will immediately respond because i sit at a desk all day at work, and have pretty much unlimited internet access... long post is looooonnnnngggggggg my neighbors are beginning to get pissed at me for screaming around all the time doing plug chops...
  25. I just finished rebuilding the top end on my 2001 wr250f. The bike has an Athena 290 big bore cylinder and piston. I never checked the valve clearance before the rebuild. After rebuilding, I checked the valve clearances. All three intake valves have zero clearance. I cannot get my .03mm gauge to slide in. The exhaust valves are only slightly on the tight side with .015mm each. I double checked and made sure I wasn't on the exhaust stroke. I have zero clearance on all valves on the exhaust stroke. I even tried turned the flywheel back and forth from TDC and measuring to see if my timing was off, causing the zero clearance. These test also had zero clearance on the intake valves. Have all three of my intake valves worn down to the point where there is no clearance? When I had the head off, the bottom of the valves looked decent. Slightly blackened, with a small amount of carbon, but I didnt notice any major wear, chips or cracks. Anyone got any idea what's going on here? Thanks in advance for your guys' wisdom.
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