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  1. Need help on deciding what to do or how to find what i need. Bought a 1978 Honda xl125s for father son project. It had low compression, found piece of metal holding both valves open. It had beaten piston, valves and compression chamber up some. Havent located machine shop that works on cycles yet so ordered upper end rebuild kit containing cylinder and new piston and gaskets and cleaned up other components. Lapped valves. Seemed ok but leaking compression on intake valve. So, orded cylinder head which I thought was for 1978 . This included valves, springs, and camshaft etc... first we noticed camshaft not the same. Rest of it looks ok or same. Discovered it must be a pre 1976 head which although it is a split 2 piece head it used contact points instead of the cdi pulse generator we have. So the shaft is shorter. Cant put in my old somewhat worn camshaft because the journals and bearings and cap cover etc are different. I have not seen any heads specifically for my year model online so cant just order right one and resale other. Also i have new valves for mine since seller would not confirm if valves were included. Seller also has not responded about this not fitting. So the question is:? Do I 1: order parts to convert to points ignition?? Dont want to and may be unexpected complications. 2: see if new head can be machined to except my original cam? Or new cam shaft extended further? 3: get original head machined, valve job , new guides and seals and new oem valves installed etc.. . Note suspect new parts are chinese but suspect if i can find someone willing to do this it would cost much more than new parts. 4: try to do a diy valve job and guide replacement? Have never done this and do not have tools.?? Thank you sooooo much for any advice or info!!
  2. I have a sikk-MX trail bike. And tried to extract a snapped bolt....snapped the easy out inside the bolt casing/shell(I drilled a hole through said stick bolt). I cant figure out which 52.4mm cylinder head to replace it with. Does anyone know? I also cant figure out the headlight wiring to my tusk headlight...if anyone has any schematics for that...please help. And does anyone know what larger/largest size tire or rim will fit on these bikes? Cuz these tires are pathetic.
  3. I got a 2004 rnz250, and I got the thing very cheap. When we took it apart we found there were a couple things missing in the head: the timing chain tensioner and one of the cam caps. Can I just buy a cam cap somewhere? Do I need a whole new head? Does anyone have parts for one of these?
  4. Alright, so I just got done rebuilding the top end on my 07 KX 450F and as I am getting ready to install the top of the cylinder head I notice I have one last piece remaining that I can't account for. I mark everything and take several pictures so I can make sure everything is put back together perfectly, but somehow this piece evaded me. I showed where I think it goes in one of the pictures I provided. Can someone tell me if I am right or if this piece goes somewhere completely different?
  5. Hi folks, Honda CR 125 1990 model, standard is 54.00mm bore? Domed or Flat Piston? Some pistons sites sell pistons as same 90-97 but I belive? that 90-91 have a domed head piston? And pistons are also avaibile in 54.50mm, if use that piston will the cylinder need to bore up and new nicasil or fits when cylinder nicasil is getting used up? Hole on the intake side on Piston for 1990 CR 125? I see some special cylinder heads to with light aircooled style on, who sell them? I hope you CR 125 experts here can help.
  6. Hi guys 👋🏻 I’m looking for some help! I’m rebuilding my 2008 KXF 250 and I’m struggling to find a complete new head for it. I have done everything else. Do the heads on any other years or models fit into mine? Any help is appreciated 🙂
  7. Hi, Anyone on the forum, or can be referred too, that is an experience engine builder with extensive experience on this DRZ motor? Someone that has built multiple motors and fully understands camshaft profiles? Calling Hot Cams is useless. I have yet to call Webb. I know they are are good. They have done cams for me in the past. I just have a bunch of questions on what I can get away with without head modifications. Using parts off an E or e3 model. I've been digging around and found some info. Can cams from an LTZ400Z be used? Whats the profile? Are the e3 model cams from the 400e a direct bolt in? Springs OK? Decompression still active. I have a bunch of questions. If anyone can help, Id certainly appreciate it. Thanks!
  8. Hi. Can somebody please help me to find a spare part thats not listed as a separate part? It is for a Husqvarna TE450, 2007. The part I'm talking about is the clamp that holds the bearing on the camshaft. It's formed like an U, and it is only listed together with a complete cylinder head. Not as a separate part. But its crazy to have to buy a whole new cylinder head just to fix this! Does any angel out there have any idea how to find one? Maybe from a blown engine or something?
  9. I have a 2002 cr250 2 stroke that recently blew up. i believe it was due to low octane fuel and extended periods of holding it wide open. Mill tech already replated my cylinder, redid the power valves, and sent me a new piston with gaskets but i was wondering if i can reuse this cylinder head if i really clean it up. Any advice would be appreciated. I can buy a new cylinder head for about $85 if needed. i would like to reuse this one but i already have $600 into the top end by sending it to millennium and the parts alone so i suppose another $80 wouldn't be too bad. pic of cylinder head attached.
  10. So I made huge rookie mistake yesterday. I'm rebuilding my xr400 after engine failure (blown piston). I got my top end all disassembled. I figured it was time to get the parts all cleaned up. Here's where I made the stupid mistake. I had some purple power laying around in the garage and figured it would be a good cleaner for my parts. I took a wash bucket and filled it with some purple power and diluted it with water. I took my top end parts and placed them in the bucket and let them sit overnight. I now know that was a huge mistake. I pulled the parts out and they actually didn't look half bad but when I pulled my cylinder head out the smooth aluminum surfaces all turned a matte black color. SOAB! The surface is now rough to the touch. I'm so upset and I just don't know what to do from here. So my questions is, is there anything I can do to combat this? I figured I can machine surface the bottom side, which I have to do anyways, but what about the top? Is there any way to clean/machine the cam journals and the valve spring seats? Or is this thing toasted? I don't know what to do, any help is appreciated, thanks.
  11. Sorry if this is not the right forum to post this, but I've recently started taking apart the top end on my 2008 ktm exc-r 450. I was able to loosen 3 out of the 4 bolts that hold the cylinder head on and when I got to the last one (front right shown in the picture) the inside rounded out. As you can see from the picture its pretty close to the side of the engine so nothing can fit around the outside of it. I tried using a star-head to get a little more grab on the inside of the bolt head but no luck. I'm trying to figure out what my options are before I make anything worse. I've been told I could cut the bolt head off, but if I do wont the threads inside still be holding the cylinder head down?? Maybe a stupid question, since from looking on the oem parts finder it looks like the threads dont start until their into that bottom part of the engine. I've also head of tack welding a bolt on top to remove it, but not sure how hard thatd be to do with such little space. Are there any other tools or tricks to getting this thing out before resorting to those last ditch efforts?
  12. Hi there! I wanna put some new valves in my old training bike - 2010 CRF250R. My main question is, what parts I should buy - what parts I should replace? FASTHEADS offers a rebuild, were they use the follwing parts: Beryllium Copper Intake Seats, Bronze Manganese exhaust guides, Chromium Nitride Coated Ti intake valves, Kibblewhite Black Diamond exhaust valves, OEM springs. They change the intake seats to actually match the titanium intake valves (stock seats are not perfect for the Ti intake valves) New exhaust guides, because they are mostly gone because of the rocker arm They leave the intake guides and exhaust seats (probably just re-cut them). --- Thats what I have on my list: New titanium intake valves - Del West or Xceldyne ? New intake seats - Beryllium Copper or MoldStar®90 (Beryllium-Free Copper) ? New exhaust valves - OEM Honda or Kibblewhite Black Diamond ? New exhaust guides - Bronze Manganese or MoldStar®90 (Beryllium-Free Copper) ? New valves springs - OEM Honda or...? When everything is true what they say about the MoldStar 90 stuff it's better than BeCu. Is this enough or should I replace everything seats and guides intake/exhaust? Any advantages if I go all titanium intake plus exhaust valves? Don't think so... Thanks in advance 😉
  13. Thanks! Crf 250R 2009 I am looking recommendations because the cylinder was 82mm moly material LA sleeve and 82 mm wiseco 13.5.1 big bore piston. with that piston at vp mr12 in the dyno only it gave 39 hp with motocross tire my goal is 45hp. I have ecu vortex ported cylinder head Crankshaft OEM custom camshaft by Daniel Crower racing Hinson yoshimura double pipe I only need the piston and cylinder but I'm confused because I don't know which one will help me more to get to 45hp. Big bore or standard? I search the best spring for high lobe lift. The one who worked the cams recommended that I use the factory spring because he says that the kibblewhite are not good. I accept any recommendation thanks! sorry mi English not is very good.
  14. Is damage on the cylinder head as critical as damage on the actual cylinder walls? .. to me, I can't see this damage having an issue.. but i'm new to all this, that's why I'm posting. Wondering about your guys opinions!
  15. I just bought a 1982 XL500R to restore (famous first words). I've got it all in pieces now, top end apart, and I found an unexpected issue (famous last words). The camshaft is significantly worn down and there is a bunch of metal buildup on the cylinder head journals where the end of the camshaft sits. Am I SOL or is this something a machine shop can fix? I fully expect to have to get a new camshaft, but the cylinder head/valves are a bit more expensive and harder to track down so I'm hoping its salvageable. It looks to mee like the metal has built on the journals up from the camshaft, not worn down the journals so I'm hoping that's a good thing. Thanks for the help!
  16. I am new to the forums and did not see anywhere on the page that has a list of used parts by forum members. I apologize if I am posting in the wrong place. As the title says, I am looking for a cylinder head. Can anyone point me in the right direction on where to find one? Mine dropped a valve. Its for a 2005 KX250F
  17. Hi All. I'll try to be clear and I commit to responding. And I'll let you know how the story ends when I am back riding! And I'll be stoked! Problem: Exhaust valve stuck open after cylinder head rebuild - valve overheated and stuck in valve guide (both came out together at machine shop). Bike: 2006 Yamaha YZ450F Background: Previous issue: About 20 hours ago head gasket failure and continued to ride bike (lots of kicks to start, wouldn't idle). Dessert riding. Replaced head gasket. new neturon ignition coil because it overheated too Coolant overflow tie wrapped shut (previous owner)...removed this and heard coolant overflow properly for first time on next ride. Failure 1 - First Exh Valve Failure: At end of ride exh valve got stuck open. That valve guide had dropped significantly. The other exh valve guide came out with the valve. (there are indents in my valve guides and key ring type holders....both stayed on top of the valve guide port). Coolant and oil levels ok when exh valve failed. Cylinder head rebuild (reputable repair shop). No valve contact/indent in top of piston. Head Rebuild: 5 Titanium valves, new springs (old ones out of spec/saw a lot of heat), ground seats. New valve seals. Oversized exh valve guides. Head surface machined. Replaced piston rings, cylinder bottom end gasket, head gasket. Ran 10 seconds with homemade shaved shims (after seats were ground my shims were well below stock with the new valves...my mistake but I ground down 5 of the 6 stock shims with a grinder...not precise). Bike took a lot of kicks to start and sputtered a lot and stalled out after 10s. (had oil and coolant) Side Note: I had gotten desperate because my buddies YZ250 shims turned out to be smaller diameter than the 450. Again, my mistake. Leak tester arrived in mail, shimmed with new shims: Leak test: Cheap tester, 30 psig into spark plug, 12% leak, can hear air out exh and intake. Convinced myself this was ok. Sized shims using my buddies YZ250 shims. Purchased correct sized one off shims from local shop. Started bike (5-10 kicks...nothing too crazy) Rode around block...sputtering when not on acceleator. But idled and accelerated well for 8-12 minutes. Failure 2 (current issue) Took it to the dirt. Warmed it up slow 4-5 minutes. Then 7 minutes up and down some small hills. Medium throttle. Nothing crazy. Exhaust valve stuck open while at 1/3 throttle. Engine stopped. No compression. Thought process (maybe incorrect) : First exh valve failure was due to overheating during head gasket issue. Could feel compression decreasing and more kicks to start engine over time until exh valve stuck open. Shaved shims didn't hurt valves and misalignment from top end for short time is not a likely cause of valve later overheating in valve guide. Shims were correct at 2nd failure...nothing to confirm otherwise. Lack of oil wasn't the cause because stem is not oiled (valve seal on stem prevents oil from coming down). Additional facts ( I believe these to be true): Leaky exh valves will get the valve hotter. (not sure if this was cause). Attached pic shows view of second failure through exh port...failed exh valve shows heat discoloration and other doesn't). Only one of the exh valves overheated on exh valve failure #2 Current Plan (can adjust based on advice): Machine shop replace valve and valve guide and grind seat of 2nd exh failure valve. Check oil getting to head using oil screw (just found out about this). Check oil channels in cams. Reinstall. THIS IS WHERE I NEED ADVICE...WHAT ELSE NEEDS TO BE CHECKED SO I DON"T REPEAT. Run engine successfully :).
  18. I just bought a 2015 yz250f from a buddy of mine for $950. Kick start locked up on him and he never looked as to what caused the problem. I pulled the cylinder head off and it has dropped the valve and did some damage to the piston as well. My question is, will a 2014 cylinder head fit on a 2015 bike? I can only find a 2014 complete head on Ebay. If it fits, would I have to get a 2014 piston?
  19. My son has a 2008 crf250r. Dropped an exhaust valve and ruined the head. Is there another year that will fit this motor or are we stuck with looking for a 2008 head only? 2004-2007 different part# 2008 different part# 2009 different part# Does anyone have any info?
  20. Hi all, I have a 94 SE model and due to top end oil starvation, I am stuck with a scored cam shaft, rocker arms and cam journals. I bought a running 90 DR350 trail bike for parts with the manual decompression lever. I got the parts bike on a great deal and I wanted to swap over the suspension and the brand new pumper carb it came with. I understand that the cams are different between the electric and kick start with manual decompression so my question is; can I use the cylinder head, camshaft and head cover from the 90 DR? if so I assume I would need to install the decompression lever as well and can that work with an electric start? Thanks
  21. It's time to open up a can of worms and talk about a hotly debated topic in the powersport community - four stroke cylinder head reconditioning best practices. I've perused the forums and had discussions with people about reconditioning four stroke cylinder heads and there appears to be a lot of mixed opinion and beliefs on what is right or wrong. I'm certainly not going to say my take on the subject is the only way, but I do want to share my opinion, explain the technical details, as well as touch on the machining process. The text below is out of my book, The Four Stroke Dirt Bike Engine Building Handbook, and details why cylinder heads should be reconditioned a certain way. Whenever new valves are installed in a cylinder head, it is best practice to recut the valve seats since the valves and seats are mated parts, otherwise the new valves are very susceptible to premature wear when run in the old seats. If a major overhaul is being performed, there is a good chance that enough seat wear will have occurred during the engine’s life that the valve seats will need to be recut before new valves are installed. This may be news to you, so I want to provide an explanation of why this is necessary. The term concentricity is used to describe the relationship between the axis of two circular objects. When two objects are perfectly concentric, their axis match up precisely with one another. In the case of the cylinder head, the valve guide axis and the valve seat axis must be as close to perfectly concentric as possible and parallel to one another. Usually, guide to seat concentricity is kept around 0.001” (0.025mm) or even less for racing applications. This is achieved by the factory by using a manufacturing process where the valve guides are reamed first. Then the freshly reamed valve guide bore is used to center the valve seat cutter. Once centered, the valve seat is cut. This process is then repeated for all the valves and results in very good concentricity between the valve guides and valve seats. As the engine is run, the valve guides, valve seats, and valve faces will wear. The valve guides will wear from front to back in an oval shape at the top and bottom of the guides. In a cross sectioned view the valve guide will take on an hourglass shape. The guide will become oval as a result of thrust forces stemming from the way the camshaft contacts the lifter bucket or rocker arm. These forces are transmitted to the valves and cause the valves to thrust against the sides of the guides, eventually causing the guides to become oval shaped. Once the guides start to become oval shaped, the valve faces will no longer be as concentric to the valve seats as they originally were. When this happens the valves will start to slide against the seats, causing the seats and valve faces to wear. The valve seats will eventually become out of round and the sealing between the valve face and seat will suffer. Installing new valves into oval shaped guides and out of round seats will ensure that the new valves wear out very quickly! To ensure the new valves being installed last as long as possible, the cylinder head’s seats and guides must be reconditioned once they are worn out. Complete cylinder head replacement is always an option, but I want to focus on freshening up the original head which is usually a more economical option, but comes with many more variables surrounding the quality of the job. There are numerous services offered in the marketplace for valve seat cutting, however, not all valve seat cutting methods are equal in terms of quality. There are hand operated seat cutters, dedicated seat cutting machines, and a few other options to choose from. Selecting the correct seat cutting process and entrusting the work to a competent engine builder is very important. The valve seat cutting process should mimic the OEM process as closely as possible. A concentric valve seat will never be able to be cut without first servicing the valve guides. If the valve guides are out of round then they will either be reamed to a slightly larger size if they are not too oval in shape or they will be replaced. Once any issues with the valve guides are addressed and they are perfectly round from top to bottom, it will be possible to cut the valve seat. Ensuring the valve guide is perfectly round is extremely important since the valve seat cutter is centered off of the valve guide bore. Cutting the valve seat concentrically to the guide requires a combination of skill and using modern machinery. The best valve seat cutting equipment in the world is worthless without a good experienced operator running it. There are two main factors which make cutting a seat concentric to the valve guide difficult. To start with, the valve seat cutter uses a pilot which locates in the valve guide. Since the valve stems are very small in diameter the pilots used to guide the seat cutters are also very small in diameter. A small diameter pilot shaft that centers the cutting tool can flex easily, which presents a real problem when cutting the seats. The next issue that arises when reconditioning seats is that often times the cutting tool will try to follow the path of the old valve seat which can make it hard to cut a concentric seat. Couple these factors together with slop within the machine, setup error, and operator error and you can see how quickly things can come out of alignment and you can end up with a poorly cut seat. In addition to seat concentricity, the depth the seat is cut to will influence valve spring pressure, shim sizes, and the compression ratio of the engine. All three of these variables will be reduced the deeper the seat is cut, which is not a good thing. The surface finish of the seat itself will influence how well the valve seals. A seat with chatter marks or other machining blemishes will not seal as effectively as a smooth seat. The valve seat width and the contact point between the seat and the valve face are also very important. Due to the complexities involved with cutting valve seats on modern four-stroke dirt bike engines, the job should not be left up to just anybody. There are numerous businesses which specialize in valve seat cutting which have both the right equipment and expertise to do the job correctly. I highly recommend spending some time researching and finding a reputable cylinder head machining company when it comes time to recondition your head. If the cylinder head must be shipped off in order to do business with a reputable company, the additional wait will be worthwhile. If you found this information helpful and would like more technical info on maintaining your four stroke engine, check out my book, The Four Stroke Dirt Bike Engine Building Handbook. Thanks for reading and happy wrenching! As always if you have comments or want to share your thoughts please leave a note below. -Paul Available at: - Amazon - Moto Fix Website
  22. My 2004 250EXC steams through the breather hole when I start it. It doesn't even last a 1 minute before it stops. Coolant level is down only slightly after a 60+ mile enduro. I use Evans waterless coolant. Has been like this for about half the season. I have taken off the head and checked the gaskets, they seem to seated properly. I can't find any cracks anywhere. Now my crank is showing signs of trouble, only 117 hours on the crank it the rod is moving side to side more than has in the past, more than it should probably, seems like the rod bearings are going bad already (no up and down play, just side to side). The crank will need replaced or rebuilt soon, too soon. All this tells me that radiator fluid is getting down in the bottom, unless I am wrong. I have replaced the water pump seal twice (although I think that would only allow water to get into the clutch, not the bottom end). What else could be happening? How can I find this leak? Is it a cracked head? Internal crack in cylinder? How do I find the source of this? Thanks.
  23. Hi guys, I’ve recently bought a kxf 250 05 model which needs a new cylinder head, I’m wondering if anyone knows what year head will fit from either rmz or kxf themselves, is it just 04-05 models that work or are they interchangeable? Thanks
  24. Hi this is my 1st post, I’m in the guts of my Xl600r engine and the cylinder head is cracked in between ports and I can not findanother one anywhere. I’ve found a cylinder head from a newer bike on eBay, the only difference I can see is on my bike there is a cylinder head bolt plug hole just in front of the sub chamber valve and on the newer one there isn’t, there’s still a hole for a bolt. Does anyone know if this will affect anything before I go and spend a fortune on it for it. Il try and post some pics and any help is much appreciated. The clean head is the one on eBay
  25. I snagged up an 93 rm250 for cheap. It needs a new head among other things. I'm wondering if a 96-00 head will work or not? Any one tried this?
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