Maintenance & Technical > KX500 Original
Rebuilding 5 hunny ???s
kawdude:
All,
Going through the process of rebuilding my 94 Kx500 and have some questions. I apologize in advance for the questions but I don't know where else to turn. My Kaw dealer has no clue and just wants me to spend money. :evil:
I pulled the jug and took measurements and it appears out of spec but the compression tests at about 150 cold. I would like to like get Eric Gore to big bore it or just buy a std size jug that's ported. I guess I'm confused on his pricing. It appears that its 425 for the big bore and that includes porting and piston parts. How about valves? Whereas, it would cost 325 to swap jugs and he takes off 50 bucks for a trade. Does this include a new piston? How about the exhaust valve assembly? Any recommendations on which to choose. Has anyone done purchased either from him? Are there any hidden charges for his work?
I also split the case and inspected the tranny...not that I know what to inspect. I did see that the shift forks (ends) are within spec but the knob that rides in the shift drum is out of spec on all three. Should I change these out? I also found that the output shaft bearing is noisy and I will replace that. Is this a common problem? How much play should there be regarding the gears on the shafts?
Crankshaft inspection...what should I look for. I seem to have excessive vibration but I don't have anything to compare it to. I could be normal. No up and down movement on rod but there is some side to side. I planned on sending this to Gore also.
Also, how do I put the crank back in the case. Should the bearings be placed in the case or on the crank. Any tricks?
I noticed that the stator plate is broken by the bolt hole where the timing mark should be. Is the mark in the center of the bolt hole. Is there a way to buy just the plate? I attempted to inspect the main seals and they seem OK. The dry side was dry and the wet side was wet!
Is there anything else I should check??? Again, I apologize for all the questions!!!
gwcrim:
I sent my top end off to Gorr yesterday. The deal as I understand it is for $400 you get:
-bored & replated
-"Mo Better" porting (which is just basically a clean up job)
-new piston
-KIPS valves cleaned and installed
-gasket set
-head machined to lower the compression
I want the lower compression so that I can run pump gas. And if it's only $25 for some kind of 'big bore' kit, well that sounds like a decent deal. There's no substitute for cubic inches. :)
Rick:
Wow, Kawdude, that's a lot of questions!! I might be able to help with some of them:
- Have never used Eric Gorr's services, but there have been some posts here that have been less than positive (in fact down right venomous). I have used Rick Peterson Motorsports on a CR265 big bore kit raced in the Open Expert National Hare & Hound Series with great results. I know Eric does a lot of work for folks, I just don't have any experience with his service, so can't be much help here.
- On the tranny, I have only had a couple of problems with a tranny, a broken shifting hub on a KX125, and a counter shaft bearing on a KX250 that took out the case. On an older bike, I would replace the counter shaft bearing without hesitation. As long as the other bearings don't have a lot of play (just by feel, as I don't have specs), I would keep the current bearings. Replace all tranny seals, as they are cheap.
- The vibration is caused from crank runout. The stock runout spec is too high, so having your crank trued will take care of the vibration. If you are going to have the crank trued, replace the rod bearing at a minimum, and rod replacement would not hurt if the wallet will allow.
- Here are the steps to installing the crank:
1-Always install the crank bearings in the cases first.
2-Toss the bearings in the freezer (still in the packages to avoid moisture contamination) for about an hour. While you're at it, toss the crank in the freezer as well, as it needs a little longer to get cold.
3-Heat the bearing pockets in the cases with a small propane torch, and the bearings will just drop in place without any convincing. (You can also use a bearing driver, but most folks don't have one in the garage.) On a KX250, you need to install the seals before the bearings, so heating can create a problem. I put a little grease on the inside of the seals so I can tell if I am getting too much heat on the seal, as the grease will begin to liquefy before you hurt the seal.
4-Before you begin the installation, you will need to build a small frame out of 2x6 standing on edge. The intent here is to have a box that will allow the case half to sit on the edges, and allow the shafts that protrude from the bottom to sit down in the middle. Without this type of frame, you will not be able to drop the crank through the first crank bearing. If you can't figure this out, I can measure mine and let you know the size.
5-Once the bearings are dropped in place, heat the inside race, and drop the crank in place. I install the crank in the case half with all of the gears first, and then drop on the other case half in place. As a note, don't heat the inside race until you are ready to install the crank, so just focus on one case half at a time. Also, don't forget to smear on some case seal on the case halves before you drop the crank through the first bearing, as the crank needs to stay cold enough for both bearings, so time is your enemy when dropping the crank in place. Don't use anything else but the real stuff from the motorcycle shop, as everything else will leak. Don?t force the second case half in place, as you will break the shifting hub. Just wiggle the case, and the hub will drop into the bearing. Might even add a little grease to the hub bearing before you start with the crank installation.
6-Once the cases are together, install all bolts finger tight. You MUST tighten the bolts evenly, such that the case is pressed in place all at the same time. Turn each bolt a half turn at a time in a crisscross pattern until everything is tight. A T-handle is preferred for this task. Also, start with the bolts around the crank in a crisscross pattern, as this is wear the resistance will be.
7-Once the cases are together, use a dead blow hammer to relieve the crank by tapping once or twice on the flywheel end of the crank. If you try and turn the crank before you do this, you will find it turns very hard. Afterwards, it turns easily. Also, check the distance between each crank half and the bearing with a feeler gauge. I try and get the crank centered, with even distance on each side. Not sure if this is that important, but it would seem to be a prudent step. You will probably find the crank is not centered. You can move the crank just slightly with your case splitting tool by just pushing on the proper end of the crank with a little pressure. Releive the crank after centering and recheck the distance.
Viola, you?re done.
Finally, on the stator plate, if the crack allows the stator plate to move, it is a problem. If you need one, you have a problem, as the backing plate is not sold seperately. However, I happen to have one in the shop that should work. We would have to check part numbers, as mine is from a 2002, but if it works, I am sure we can work a deal.
Enjoy the rebuild.
Rick
kawdude:
Thanks Rick. I appreciate you taking the time to answer all these questions. Lots of excellent information!!! I will replace the countershaft bearing. This bearing has noise and seems a little rough when spun. I will check the other bearings...maybe they don't need replacing. I plan on having Gore do the crank rebuilt. This includes replacing the rod with a "hot rod" kit and bearings.
Several things...
What sealant for the crankcase is recommeneded?
When I pulled it apart I noticed that the crank came out of the left side bearing fairly easily but on the right half I had to use a puller. Is this normal?
When I put the seals and bearings in the case halves. How far to I push them in? Do I bottom the seal and then bottom the bearing.
When I install the crank into the tight bearing will it slide into the bearing easily if the crank is cold and the bearing hot. I don't know how I would "press" the crankshaft into the bearing if it didn't!
Thanks again.
Rick:
I'll take a look at home for the case sealer, but several folks make this stuff. I really like the product from ...uh...errr...Honda :oops: . I know, I know, but heh, we use what works. I have also used the following product:
Threebond 1211 Here is the web page:
http://www.instantop.com/cyclepages/threebond.htm
Visit a good local dealer, and they will probably have something in stock, or can get easily. White Brothers sells the Threebond product line, and most good shops have an account with White Brothers. It's not cheap, and will cost you $15 or so, but will last a long time.
In addition, you will want to make sure you remove all of the old gasket material. A razor blade will work, but be careful not to damage the surface. I have also used a dremel with a fiber brush. The best method is to use a scotch bright pad (the green one in the kitchen), but be sure to rinse everything well in a parts washer or with spray on carb or brake cleaner (always wear safety glasses when using the sprays, as the stream will hit various pockets and deflect into your eyes).
On the bearing, it is not uncommon to have a bearing stay on the crank or in the case during disassembly. If they stay on the crank, you will need a press or a good puller to remove. If they stay in the case, just tap them out. In either case, as long as the bearing has not spun on the crank or in the case, you should be fine.
During reinstallation, the bearings should go all the way into the case up against the outside edge of the pocket. You will probably have to tap the bearings in the pockets a little, just make sure you use a brass hammer (if at all possible) and tap at four points around the bearing as you walk the bearing into place. Think of the bearing as a clock face, and tap at 12, 3, 6, & 9 oclock. Don't rush. As soon as the bearing is in place, the tapping tone will change.
On the seal installation, add a little high temp grease to the seal and tap flush with the outside of the case. Hear again, tap gently around the circle. If you have a piece of pipe about the same size as the outside of the seal, you can slip this over the crank and drive the seal straight in, but walking the seal in will work just as well.
I really enjoy working on the bikes, so hopefully you will have as much fun. If you have any more questions, just post 'em up.
Rick
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