I did a search on kickstart-skipping and found most posts were years old already. I didn't want to necro an old thread, so here we are.
Preface to all that follows: I am not a mechanic. You will no doubt spot this as I stumble through my discussion. If I state something blatantly wrong, I am sorry and please correct me. I am trying to offer some help, that is all. I am not trying to trick anyone into blowing up their bike.
Now then...
Cliff's notes version:
The skipping of a kickstarter is, in my experience, very likely to be excessive play between the outer case cover and the shoulder on the kick-shaft just above that plastic centering-bushing. If the kickstart shaft has any loose in/out play, this is likely your problem. Shim this clearance out by buying some thin stainless washers and putting them on the kickstart shaft. If you look at the microfiche for 88-early-90's KX's, you'll see they show a thin washer that goes there in some applications. The generic shop-manual I have mentions 'some years have this washer'. Its not very specific.
Importantly, the shims you use will -not- rest directly against that plastic spring-centering bushing..they will register against the small shoulder on the kick-shaft. I don't know why this is, but I bought the shim (a Kawi oem part) for my bike, and the shim stops against this shoulder, not all the way to the plastic bushing like I was expecting.
My bike was a basket case build, in parts in plastic tubs.. the motor was all apart. I have no real proof that all of the parts I have are from the same year engine, for instance. What I have did eventually all go back together, but.. I can't swear it is really 'all an 88 engine' internally. I suspect that some 89/90 parts are in there. So, caveats apply here, but I believe the base problem of shaft play would be found in an older 'all homogenous' setup too. I think the play is a result of normal wear/tear.
/cliffs
Overly-wordy, long analysis of the problem (take with grains of salt here... ):
The bottom line is, if you can pull 'out' on your kickstart shaft and it moves even a couple of mm out, then you are going to very likely get this skipping problem when you kick it over. This extra clearance lets the ratchet and spur gear misalign under load and skip. What's happening (in this trouble-case anyway) is that the kick-shaft, carrying the spur gear, rides 'out' of the case, so to speak.. a couple of mm, and this then means the ratchet gear is barely connecting to the spur gear ratchet teeth by just the tips (mind you!).. this isn't enough solid purchase to do the task, and with the clearance the spur gear has on the shaft to allow it to spin, the spur gear will now deflect off-axis slightly and the ratchet gear slips right past the ratchet teeth on the spur gear.
I do not believe the problem is that the spur gear is worn on the ID. I took mine off and did not notice any obvious wear signs/chattering/etc... neither was there any obvious wear on the bearing surface for the spur gear on the kick-shaft. It was shiny and smooth. I think the spur gear has clearance to let it rotate and get splash oiling, and that's all.
It is also not, as I've read in dozens of old posts, the idler gear being worn out or anything else. If the idler gear teeth were that worn, you'd know it b/c you'd have shrapnel in your gear-case and lots of other carnage would result. I've never seen 'just one gear' have worn teeth either. Not saying some kick-skipping issues couldn't be the result of 'broken off teeth' from idler gear (and you happen to catch it 'just right' so that the missing teeth prevent rotation). What I am saying is, if you pull the case cover and you do not see actual broken off idler-gear teeth (or any other broken teeth on other gears), then your idler gear is fine... do not replace it hoping to fix the kick-skipping.
Further, you probably do not need to replace the ratchet and spur gears either. If they show wear on the tips of the ratchet-teeth, this is the result of the excessive clearance issue letting them misalign during the kick-stroke. Over years, that will burnish down these teeth and you will see 'some' wear/shiny spots.
Unless this wear is so excessive that you see real gaps when the ratchets are meshed, you are probably not needing new gears. I'm sure there are use-cases where there is enough wear to warrant new ratchet and spur gears, not saying this is impossible... just unlikely. The problem with the older 2strokes now is, Kawi doesn't stock the spur gear anymore... so you can't buy a new one unless you get lucky and find a shop with NOS parts sitting on the shelves. They don't appear to stock the spur gear for any KX250 2s.. up to the last year it was made. The ratchet-count on the later ratchet and spur gears vs late 80s ones is different, so you cant just buy the ratchet gear and hope it works with your older spur gear (ask me how I know).
The real, more obvious culprit is excessive shaft movement (heh heh... minds out of the gutter!). Shim this up and you'll be amazed at how solid your kickstarter will work. I suffered for years with this until I took it all part a few weeks ago and realized what the problem was with my setup.
OH, also.. yeah, it might be a weak ratchet spring causing your problem, but I doubt it. That spring has like 1/2lb rate brand new (I bought one to see). I installed -two- on my ratchet mechanism (with a thin washer to separate them so they were not enmeshed) to increase the total rate.. and this really didn't fix anything... just made the ratchet click louder. The spring's apparent (to me) purpose is to return the ratchet gear to 'mesh' position when the kickstart lever returns to 'home'. You are not getting enough extra 'clamping' force from this tiny/weak little spring to overcome the slop/play that is the real problem. If you put a 30lb spring in there.. ok, that would probably band-aid the issue b/c it would force the entire kick-shaft 'out' and into the case cover.. eliminating the play we're trying to fix with a shim. So, I'll modify my prior comment and say .. perhaps if your oem ratchet spring has zero tension, a new one puts just enough pressure on the assy to take up the small play in your kick-shaft to case cover. Maybe. Happy for you if this really fixed your problems
I think the majority of the problems are really what I've been describing though. Since this problem builds over time from normal wear (the kick-shaft shoulder rides against the case cover.. steel on aluminum it appears!), it creeps up over the years.
Be very careful to measure the existing play/clearance first! If you shove a 2mm thick washer in there to tighten up 1mm of play, then reef down the case cover bolts, you'll very likely crack your case cover or worse. Measure it all as best you can, then go with a slightly thinner-still washer setup. If you get the play down to under 1/2mm, you'll prob be fine.
I bought a bunch of very thin, precision washers online in thicknesses ranging from .03mm to 1mm and wound up using, I think, a .03 and a .5.. something like that. I want to say the ID was like 18mm... its whatever the primary dia of the kick-shaft is outside of that shoulder... and the OD was prob 22mm or there-abouts. Probably only really needed the .5mm thick one, but I was trying to get every ounce of play out. This may bite me later on... I don't know if Kawi designed this to always have a smidge of play... like I said, the non-Kawi manual I have barely touches on this subject and gives no real spec/clearance.
Go at your own risk, but I do think the notion here of taking out that shaft-movement is the true fix for skipping kickstarters on these old bikes.
Oh, Also!.. one more important point I'll add here just for completeness's sake ... there are -timing- marks on the kickstarter shaft and ratchet gear that you must get right. This is what allows proper clocking of the kickstart return spring. If you get this wrong, you may wind up with a 'lazy' kickstart return where it never really retracts all the way home. There are posts on here about this, but its simple... with the kickstart assy in your hand.. look at the ratchet gear end (the ratchet gear is the one with the little 'arm' on it).. look to see if the punch mark on the gear aligns with the punchmark on the shaft. If not, align them by turning the ratchet gear (you'll have to pull it away from spur gear) until you get them to align when the ratchet gear returns to 'home' position (meshes with spur gear under that little spring-tension). What this does is set up the correct kick-return-spring preload.
Whew... sorry.. very wordy, very likely to have many technical mis-statements. I wrote a lot of stuff here, I'll prob proof it after this posts and edit it later.
Again, I'm trying to add some knowledge to help folks.. assume positive intent. If I stated anything blatantly wrong, please correct me if you are sure I am wrong. If you just think I'm wrong and can't prove it, well, we disagree perhaps, and that's fine too. I just ask that you state 'you are not sure' either. Let the folks get all the opinions.
