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Hello guys, I am need of some serious urgent help. I have a bike that is a 1996 model kx250. The bike has a hole in the right side crank case where the kicker is. I used JBWELD the 1st time to patch it and it held up but it has gotten a lot worse over the time. I am dire need of the case to fix it. I did a little research (google & local kawasaki dealer/customer support) and found out that no other cases from other models will work with the 96 model. I have search Ebay for nearly 2 days now non stop with no luck of finding the right side (found the left) or even a set of cases for that model. If anyone could help me out and maybe enlighten me on some people selling cases, please do link them below!
Was wondering if anyone has ran across an aftermarket oversized crankcase cover to increase the amount of oil on a CRF450r? I am a desert rider but I had this 450r given to me by my son in law because it was too fast for him. It only holds about a quart of oil which is a huge concern to me when I'm out in the middle of nowhere 30 miles from camp. I assume that more oil would be a good thing but maybe there's something I don't know regarding the lubrication system on this bike? I will say it is one fast mofo. Seriously thinking of getting an AMA number and riding the old man class next year. Any and all suggestions and comments welcome. Thanks in advance. TL
If you’ve ever experienced a ride or race where your crankcases got damaged in some way, whether from a rock or engine failure you know just how painful dealing with the aftermath of damaged crankcases can be. For those of you who haven’t had to deal with crankcase issues, consider yourselves lucky and know that if you stay in motorsports long enough, your time will come. Late last year I picked up a 2005 Honda CRF250 project bike (click here to read about it) which came with crankcase damage. The crankcases had the following issues: Stripped right main bearing retainer bolt hole Broken off right front shift shaft boss/bore Partially broken off cam chain guide I chose to repair the crankcases because it can be a much more cost-effective solution than buying brand new cases. In this post, I’m going to cover crankcase repair options and tips that may help you save your next set of injured cases when the need arises. While you may or may not be equipped with a welder or feel comfortable carrying out the repairs, the information provided will be equally helpful when discussing repair options with your local welder or fab shop. Strength Considerations First off, since the crankcases house the heart of the engine, consideration should be made as to how structural the repair area is to the functionality of the engine. Secondly, the likelihood of making a repair that results in a joint that is equally strong to the original in critical areas should be considered. If the criticality of the joint is deemed too high or the repair is too difficult, then it is advisable to pursue a new set of cases instead of risking a mediocre repair that could jeopardize future operation. Many people often question whether or not a welded joint or the weld material is as strong as the base material used to manufacture the crankcases? The answer to this is, it depends. The specific casting process used to make the crankcases has a significant effect on how strong the cases are and whether or not the manufacturer chooses to heat treat the cases after casting them. The strength of the welded repair is only as good as the weld itself. Cleanliness, depth of penetration, and skill all play into how strong the repair will be. Most of these variables are relatively controllable; however, skill and experience are primary drivers. Since engineering data that outlines what materials and processes manufacturers’ use to make their crankcases isn’t available, it is impossible to say with any certainty that a weld repair will be as strong as the original material. However, it could also be stronger or weaker. We simply don’t know without testing or analysis. Personally, based on my knowledge of casting processes and how I believe most engine cases are made I don’t believe the alloys used to make weld repairs on crankcases differ significantly in properties from the base material. Repair Methods Outside of welding, there are a couple of other repair methods worth considering depending on the issue at hand. With proper preparation, epoxies (think JB Weld or equivalent) can be used to fix minor issues. For stripped threads, heli-coils or increasing the tapped size can be good options. Welder Types Both MIG and TIG welders can be set up to weld aluminum; however, in my experience, it is preferable to use a TIG welder because they offer significantly more control throughout the welding process. Due to the thick walls found in many crankcases using a welder with enough amperage is imperative. For most dirt bike applications a welder capable of at least 150 amps will be necessary. Welding Best Practices Preparing the Damaged Area - Since untreated aluminum oxidizes when exposed to oxygen, the area being repaired should be prepped by grinding away the surface layer in and around the joint. The material can be removed with a die grinder and an appropriately sized bur. Depending on the area and geometry of the repair it may be necessary to groove out the joint so that additional surface area and weld depth can be achieved. Check Flatness - Before welding, take the opportunity to assess the flatness of all the crankcase mating surfaces. This initial assessment will serve as a benchmark to compare against once all welding is complete. Cleanliness - The cleanliness of the area to be repaired is critical to the success of the job and to keep frustration levels low. Carefully clean the crankcases using isopropyl alcohol, acetone, or other suitable cleaners. Be sure to verify whatever cleaner you use will not emit harmful potentially life-threatening chemicals should you inadvertently expose them to high temperatures and argon gas. Brake cleaners are typically a no-no since they may contain Tetrachloroethylene which can become fumes of phosgene when exposed to high temps. Phosgene, even in small doses, can be lethal. If the crankcases are very porous, an initial cleaning can be performed to remove most of the oil. The cases can then be baked at around 250°F (121°C) for 15 minutes, which will help draw out oil from beneath the surface. The cases can be cleaned again. Filler Rod Choice - 4043 filler rod should work well for most castings and is what I used to carry out the repairs on my CRF250 crankcases. Alternatives to consider include 4047 and 4943. 4047 filler rod offers improved resistance to porosity over 4043 due to its higher silicon content but offers slightly less strength. 4943 filler rod was designed to be an improvement over 4043 and may offer additional strength while retaining similar flow characteristics. Preheat - Heating the crankcase in the oven and raising its temperature before welding will help reduce distortion post welding and make welding the part easier. Oven temps up to 300°F (149°C) and bake times up to 30 minutes can be used to preheat the crankcases. Limit Distortion - Distortion is a risk anytime something is welded and due to the criticality of the location of bearing bores, shafts, and other features found within the cases everything possible should be done to limit distortion throughout the welding process. What can be done will be situation dependent, but the following are recommendations that can be implemented when practical: Preheat the crankcases Make weld repairs with the case halves bolted together Clamp a single case half to a flat surface if the repair permits Leave bearings in their bores Check Flatness - Upon completion of all repairs, check mating surface flatness before returning the case to service. If mating surfaces are not flat corrections can be made on a surface plate or via milling in extreme cases. CRF250 Case Welding and Repair - My CRF250 cases welded well, and I was able to get proper fill with minimal porosity. The weld layers built nicely as I filled in the cam chain guide, shift shaft boss, and bearing retainer hole. Post welding I carefully machined in a new bearing retainer bore, and shift shaft bore. My case did not distort due to welding but had some knicks and dings on their mating surfaces, which I addressed using my surface plate and sandpaper. Upon completion of all the work, I inserted the dowel pins and shift shaft back in the cases and checked fitment of the shift shaft in the new bore. Everything lined up well, and the case halves and shaft mated perfectly. Wrap-up I hope you enjoyed this write-up on welding crankcases and that you consider it as an option the next time your cases incur life-threatening damage. I’m looking forward to moving my CRF250 project forward and taking the next steps to get my engine running. If you want more engine building knowledge at your fingertips, check out my books on two and four-stroke engine building. The dirt bike engine building handbooks are nearly 300 pages apiece and share a wealth of knowledge, such as repairing crankcases, which you won’t find in your service manual when it comes time to rebuild your engine. Check them out on our website or on Amazon. Thanks for reading and have a great week! - Paul
“Splitting the cases” is often referred to as a daunting or undesirable task, but if you are well prepared and properly equipped then it can be a straightforward job. To alleviate any concerns you may have with the task, I want to discuss best practices and share some tips that you may find useful when dealing with crank bearings that utilize an interference fit with the crankshaft. We’ll get started by discussing preparatory items and work through to completing the job. Preparation I always recommend prepping for crankcase separation by thoroughly reviewing the service manual. This is important in case any special instructions are present, such as guidance on how the crankcases should be positioned. Typically, it is advantageous to lift one half off the other in a certain orientation due to the way the gearbox or other components are installed. Secondly, a review of the manual may highlight any specific hardware that must be removed prior to attempting to split the cases. From a tools standpoint, a crankcase splitter tool is a worthy investment because it will help ensure the job goes smoothly. Case splitters are relatively inexpensive and widely available. Alternatively, for the budget conscious or lesser prepared, a case splitter is something that could be fabricated. Whether buying or making, ensure you pick up a model with a protective end cap for the crankshaft or fabricate one. We’ll discuss the end cap later. The other tools required are all fairly standard and include your typical sockets, wrenches, and soft mallets. Wooden blocks or other soft semi-malleable spacers should be selected which level and raise the crankcases off the tabletop. This allows the cases to be positioned so that the split line between the cases lies horizontally and subsequent splitting can be done vertically. This will help ensure evenness of separation as well as reduce the likelihood of components falling out of the cases unexpectedly. As much as shortcuts are desirable, just about everything external to the cases must be removed in order to successfully split the cases. Clutch, stator, crank gear, etc. must be removed prior to case splitting. Your service manual will provide further clarity as to what needs to come off. Technique & Tips Once you’re ready to separate the cases, the first thing we’ll need to do is remove all the crankcase bolts. The crankcase bolts should be removed via any prescribed patterns outlined in the service manual. Since the crankcase bolts are typically several different lengths, ensuring the location of each bolt is well documented is extremely important. As I discussed in my post on keeping track of bolts, the cardboard gasket method or any other you find suitable should be utilized so that the reassembly process is straightforward later on. After the crankcase bolts have been removed, the crankcases should be inspected one final time to ensure no hardware that should have been removed prior is hitchhiking. Trust me, trying to separate cases only to find there is one last forgotten bolt is quite frustrating! Once you’re confident all the necessary hardware has been removed, position the cases on the blocks with the correct half facing up. Next, install the protective cap over the crankshaft. I advise using the cap whether you own a two or four-stroke simply because in both cases it helps preserve the end of the crankshaft. This is of particular importance on four-stroke engines that utilize an oil feed that passes through the crank. Once the crank end is protected, proceed to install the crankcase splitter. Select threaded holes that are as close to equispaced from one another as possible to promote uniform loading of the case splitter. When threading the case splitter studs into the crankcase, make sure you engage at least 1.5 times the diameter of the stud diameter. For example, if the stud is 6mm in diameter make sure at least 9mm of thread engagement length is achieved. This will help ensure the threads are not stripped when you attempt to separate the crankcases. With the crankcase splitter installed begin tensioning the main bolt against the end of the protective cap. Proceed to tighten the bolt until the crankcases begin to separate about a 1/16” (1.5mm). Once separation has occurred, make sure that separation is even all the way around the cases. Due to the way the case splitter loads the cases, the area near the output sprocket tends to lag. Case separation needs to be even so that the dowel pins used to pair the cases together don’t bind. If the output sprocket end of the cases hasn’t separated, use a soft rubber or plastic mallet to gently tap in that area. Tap carefully and only on case areas that appear sturdy. Once you’ve created an even gap, proceed to tension the splitter bolt, tap when necessary, and fully remove the crankcase. Upon separation, make sure that no gearbox components, such as washers, have stuck to the case. What I’ve described is the ideal sequence of events for a successful case separation, however, occasionally the cases won’t be as cooperative. In the past, I’ve had to deal with crankcases where moisture has found its way into the dowel pin bores and corroded the dowel pins. This effectively seizes the dowel pins in their bores and makes the separation job more challenging. If the crankcases are being resilient to separation, stuck dowel pins may be a potential problem. Most dowel pins are located opposite one another and their exact position can often be referenced in the service manual or in the crankcase section of part microfiches. Once the location of the dowel pins has been confirmed, a torch can be used to lightly heat the dowel pin areas. Heat will expand the metal surrounding the dowel pin and aid in freeing up the stuck pin bore. Usually, a few careful rounds of heat, tension on the splitter, and well-placed tapping is enough to free up the pesky cases and get them separated. Alternatively, if the heat does not help, applying a penetrant to the pin bore areas is another option that may help free things up. If you find yourself dealing with stuck cases, the key is to be patient and think through all your options. In these types of situations, most mistakes are avoidable and are usually the result of rushed decisions. Once the cases have been separated, the remaining tasks of removing the gearbox and pushing the crank out of the remaining case half can commence. I hope you’ve enjoyed this write up on crankcase separation and that it makes you more prepared for the job. If you’ve got additional crankcase separation tips that you want to share, please leave a comment below. For additional engine building information, whether two or four-stroke, check out my engine building handbooks. Each handbook is offered in print or digital form, contains over 250 color pictures, detailed instruction from start to finish on full rebuilds, and contains a wealth of information pertaining to diagnostic testing and precision measuring. Thanks and have a great week! -Paul