OzVMX Forum
Clubroom => Tech Talk => Topic started by: Kenneth S (222) on October 05, 2016, 07:24:46 am
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Hi Guys,
I have been battling with the shifters on the two bikes I am racing at the moment, the 84 CR250 and the 89 CR250. I continue to have the issue of the shifters getting sloppy on the shaft. Each time I prepare the bikes, I tighten the bolts just that little bit more to within an inch of stripping the thread, but by the time I get the bikes home after a race day they are dancing around again. On the 89 I bought an OEM shifter from Honda for $100 and while it was a nice snug fit when I fitted it, within a few race meetings it is doing the same. I know fitting a steel shifter will help but I would prefer not to have to go that way. Is there a fix for this I don't know about?
Cheers,
Kenneth
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You won't like my fix on my 'rat bike' 360 yam but here goes anyway. If all else fails because the splines on the shaft have tapered off on the outer half past the locating groove for the pinch bolt i've drilled straight in [not crossways but straight in] as the lever pinches up. You end up with half the hole in the shaft & half in the lever. Drill in the depth of the lever plus a fraction, which about equals the depth of the shaft spline before the splines end, then tap it to 6mm thread & screw an allen head bolt in which are real high tensile. I dare say you're talking an ally gear lever & i'm talking steel so the drill might wander of to the ally side. Fit a steel lever & do 'that' maybe. That'll start the ball rolling but realy a new shaft & lever are the final cure. One more back yard mechanic thought--won't be a safe enough amount of shaft but thinking drill straight in dead center & tap it to maybe 5mm allen bolt & a bog washer to stop creeping outwards. in the gear lever i use a high tensile 6mm bolt with a spring washer under the head which allows [reluctantly] a slight bend as it's finaly tightened. Mainly talking my old stuffed steel levers as having been slotted wider they pinch up on an angle & end up bending the bolt a little [or trying too]. Found some 6mm bolts with number 10 strength on the head out of my honda car motor, strong 'as'. Anyway--carry on. long essay about not much. Cheers.
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sounds like the alloy threads are stretching or the bolt is loosening. I have assumed you are loctiting the bolt.
also check the shifter isn't closing on it self and not clamping the shaft tightly, you may have to take a thin slice out of the inside of the shifter to allow it to clamp tighter on the shaft.
you could also drill the threaded section out and put a longer allen bolt and a nylock nut on the outside with locktite on, that will fix it.
these arnt pretty fixes, but have solved those issues for me
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The first thing that comes to mind is try loctight on the shaft.the other old cure was to put the lever in a vice and run a hacksaw through the split opening to increase the gap to give you more adjustment when tightening up.
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Leave the thread in the lever , put a longer bolt in and tighten it up until the lever is as it should be , then use a nylock nut as a locking nut on the protruding thread of the new bolt , has worked for me before and your lever isn't modified either.
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every time this has happened to me I found that putting it in the vice clamp it shut run a hacksaw through it worked every time
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Sounds to me like your shaft spline is cactus. Replace the shaft AND gear lever with new.......or weld it :)
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Thanks guys, that gives me a few good ideas to try out
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i wouldnt go to the extremes of above just yet. remove it and clean it and the splines spotless. run a wire brush over the splines to remove all the gunk that will be in them . then a small tap with a hammer on the lever to close it up just a little so its a damn tight fit on the shaft. A few "gentle taps will have it seated. do the bolt up and thats all you need do unless the shaft is worn . incidentally they only wear if they are loose and grime gets in ;)
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As others have said, check the gap in the shifter to make sure its not closed up before it's tight on the shaft.
I also run a longer bolt with a nut as backup but also use a high tensile bolt as a normal mild steel bolt can stretch.
If adding a nut onto the back of the thread make sure it has a flat spot to sit on to.
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i wouldnt go to the extremes of above just yet. remove it and clean it and the splines spotless. run a wire brush over the splines to remove all the gunk that will be in them . then a small tap with a hammer on the lever to close it up just a little so its a damn tight fit on the shaft. A few "gentle taps will have it seated. do the bolt up and thats all you need do unless the shaft is worn . incidentally they only wear if they are loose and grime gets in ;)
of coarse the hack saw treatment is only for good splines on both and is clean and you can see that its touching then it works well, if everything is fluct then replace everything, oh yer replace the bolt Ive seen them stretch before (you would think they would just snap)
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If you have to crank the fcuk out of bolt on a new gear lever the shaft is rooted.
The depressions in the spline on the shaft should mirror the profile of the ridges on the spline on the gear lever. On a 30 year old shaft the depression on the spline widens due to back and forth motion of shifting up and down, so even with a new lever and a huge spanner to tighten the shit out of it there will still be side to side movement as the ridge on the spline on the lever rocks back and forth between the depressions on the shaft....
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I'm surprised nobody has suggested the bleedin obvious and to weld the gear lever onto the shaft ::)
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Sounds to me like your shaft spline is cactus. Replace the shaft AND gear lever with new.......or weld it :)
I did :) .......only because I've done it myself in the past.
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Welding it on would be a last resort, personally hate buying bikes then realising it has welded splines.
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I've had this problem a couple of times before, I put on a brand-new alloy lever on to a very slightly worn shaft, the el-cheapo lever kept stretching around the spline and coming loose after about 15 min of riding. A steel lever and better quality alloy lever's fix the issues.
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I'm surprised nobody has suggested the bleedin obvious and to weld the gear lever onto the shaft ::)
Not easy to weld aluminium to steel though never say never ;D
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Nothing wrong with a steel lever that has a folding tip. They can be clamped much tighter on the shaft. And they don't break in a crash/tangle.
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I'm surprised nobody has suggested the bleedin obvious and to weld the gear lever onto the shaft ::)
Not easy to weld aluminium to steel though never say never ;D
what rods would you use hmmm I think stainless or perhaps woodcraft and a big hammer
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I was doing some alloy TIG welding a little while back and was wondering why it wasn’t sticking until I realised I was using a stainless filler rod. D'oh.
Worked much better with alloy.
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I was doing some alloy TIG welding a little while back and was wondering why it wasn’t sticking until I realised I was using a stainless filler rod. D'oh.
Worked much better with alloy.
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LOL ive done the same and me old mate did the visa versa
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Of course there is also the possibility that operator error could play a part, one "family member" stomps on the gear lever heavily, I was always fixing the same issue on his bikes!
Tony.
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I'm surprised nobody has suggested the bleedin obvious and to weld the gear lever onto the shaft ::)
Not easy to weld aluminium to steel though never say never ;D
what rods would you use hmmm I think stainless or perhaps woodcraft and a big hammer
put both in better peno
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As evo550 said new parts required.Im as bodgey as they come but whenever Ive suffered these probs a new shaft and lever is the only real repair unless its a turd then just weld her her up.
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I'm surprised nobody has suggested the bleedin obvious and to weld the gear lever onto the shaft ::)
Not easy to weld aluminium to steel though never say never ;D
what rods would you use hmmm I think stainless or perhaps woodcraft and a big hammer
put both in better peno
LOL would you need to twist them together or tie string around them, hey I have a string theory soak the string in flux get a capaciter
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This topic got me thinking about machining a tapered pinch bolt.
Standard splined shift levers piss me off actually, they never let you get the lever were I want it, grrrr
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This topic got me thinking about machining a tapered pinch bolt.
Standard splined shift levers piss me off actually, they never let you get the lever were I want it, grrrr
Can you explain more in detail about this tapered pinch bolt please?
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This topic got me thinking about machining a tapered pinch bolt.
Standard splined shift levers piss me off actually, they never let you get the lever were I want it, grrrr
Can you explain more in detail about this tapered pinch bolt please?
I say he means the tapered bolt would move the gear shifter to the centre of the shalf slot .
I've never had this problem the standard bolt should centre it right unless it's bent , worn or stretched .
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You could weld it on. Hey come to think of it there are a couple other things you could weld on while your at it that will make sure you never have problems with them in the future like the kick starter and drive sprocket.
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This topic got me thinking about machining a tapered pinch bolt.
Standard splined shift levers piss me off actually, they never let you get the lever were I want it, grrrr
Can you explain more in detail about this tapered pinch bolt please?
I'm thinking like old push bike pedal crank bolts. On typical splines the shaft has a machined 'channel' running circumferentially in the spline. By careful measurement you could have a pinch bolt tat was tapered and tightly engaged into tbis groove.
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I had shaft welded up and machined to correct size with new splines cut. Instaled shifter using high tensile bolt(8.8 ) with washer and spring washer. Check tightness before every ride. No dramas so far.
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I had shaft welded up and machined to correct size with new splines cut. Instaled shifter using high tensile bolt(8.8 ) with washer and spring washer. Check tightness before every ride. No dramas so far.
That would be the go if you cannot find a new or good used shaft,
But I think the question also has a bit of just a reliable fix without opening an otherwise good in season use race engine?? Maybe?
This is the go if you don't want to pull the engine down
Get one of these diamond encrusted 3.15 pencil grinder bits and a tiny round file for the lever bore if you want.
(http://i677.photobucket.com/albums/vv132/mc125mick/20161017_184318_zpswd2h1yui.jpg~original)
Like others have said clean lever bore and shaft spotless.
Put it exactly where you like it. Mark it.
Then remove it and grind a half moon in both the shaft and lever, in the spot where shown
(http://i677.photobucket.com/albums/vv132/mc125mick/20161017_185201_zpsb14k7nom.jpg~original)
It will take a little while, obviously don't do too far.
Loctite everywhere except pinch screw thread.
Make it so you can tap in a small piece of 3.15 mm Satincraft welding rod.
Use one of those really thick section spring washers under the head of the screw of an 8.8 unbrako socket head
(http://i677.photobucket.com/albums/vv132/mc125mick/Heavy_Spring_Washer_zpsa4iav90x.jpg~original)
No loctite on the thread but a nyloc nut on the end if you have room, so you can nip it up if you have a shitty stretching lever.
I guarantee this is a reliable fix, unless you have a lever made from always gunna stretch pure Chinesium.
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Just a thought on gear lever bolts. 8.8 grade is not really high tensile. You need the harder to find 10.9 grade if you want hex head. Socket head cap screws- SHCS- are about twice the yield strength and thread-strip strength as 8.8 and your strongest, and toughest, ie not 'brittle' commercial fastener. High tensile M6 nuts are Conelock or the nylon insert type with the h/t marking code- most nylock nuts are made from free machining steel and strp at about the tension a shcs requires to stretch enough to be functional.
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valid point Momus, I'm a believer and a user of 10.9
But its all to late for me, ive just welded up all gear levers and kick start lever's as a precaution! non of them needed it as they were all in excellent condition, I am just not willing to accept the fact that one of the blighters may loosen on my watch
all done with great care and attention to detail, all prep grinding done before full penetration welds
Now does anyone know how to change a heat affected seal that's leaking? with out removing the levers in question!
thank you in advance
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So what you are saying is that an 8.8 SHCS will fail before the alloy thread does in the new alloy lever that he has fitted?
Forum full of ........ s
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So what you are saying is that an 8.8 SHCS will fail before the alloy thread in the new alloy lever that he has fitted?
Forum full of ........ s
yep that makes sense in the alloy like your saying, but tugging together that old stealy 10.9 is a better option (me thinks )
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Hi Guys,
I have been battling with the shifters on the two bikes I am racing at the moment, the 84 CR250 and the 89 CR250. I continue to have the issue of the shifters getting sloppy on the shaft. Each time I prepare the bikes, I tighten the bolts just that little bit more to within an inch of stripping the thread, but by the time I get the bikes home after a race day they are dancing around again. On the 89 I bought an OEM shifter from Honda for $100 and while it was a nice snug fit when I fitted it, within a few race meetings it is doing the same. I know fitting a steel shifter will help but I would prefer not to have to go that way. Is there a fix for this I don't know about?
Cheers,
Kenneth
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yep fare cop
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Modern bicycles, until recently, mostly used a square tapered shaft for the their cranks.
Why not for motorcycle kick starters and gear levers?
T2X
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The finer the spline the greater the choice of positioning Tony.
I have a habit of causing neutrals when I stretch way back on to the rear of the seat. My boot toe. To stop this ridding error of mine, I simply set my gear lever one or two splines higher than most do. Depends on the bike but works for me.
And I greatly prefer it that way.
The thing is these things dont all ways play up or strip out.
Depends alot on previous owner maintenance and as we all know the are a lot of shite sub standard after market levers and repo parts around too.
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For example there have been some real shite after market Maico gear shift cranks about at times. Some real disappointments.
I am nearly finished my first batch of new Mega 2 ones. I thing they will be better than some of the past choices ;)
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The finer the spline the greater the choice of positioning Tony.
Ah yes! Of course!
T.
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this post has reminded me of my RM250 N had the alloy gear lever on it, was always coming loose fixed it by removing it and putting a steal one on
yes the finer the spline the more adjustment, on the Suzuki with its coarse spline I have had to heat and bend the gear levers to be able to get it in the right positon, now I cut them at the weld rotate to my preference and weld, just looks better!
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this post has reminded me of my RM250 N had the alloy gear lever on it, was always coming loose fixed it by removing it and putting a steal one on
yes the finer the spline the more adjustment, on the Suzuki with its coarse spline I have had to heat and bend the gear levers to be able to get it in the right positon, now I cut them at the weld rotate to my preference and weld, just looks better!
Yes sometimes you just have to do whats best. Its great to have that sort of experience and background, to be able to do so.
On Maicos for example. I never had trouble with the early alloy ones. But they don't fold.
So I have collected NOS latter chrome plated forged steel ones. Usually at great expense.
I don't like to add weight, but they are brilliant if maintained.
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this post has reminded me of my RM250 N had the alloy gear lever on it, was always coming loose fixed it by removing it and putting a steal one on
yes the finer the spline the more adjustment, on the Suzuki with its coarse spline I have had to heat and bend the gear levers to be able to get it in the right positon, now I cut them at the weld rotate to my preference and weld, just looks better!
Yes sometimes you just have to do whats best. Its great to have that sort of experience and background, to be able to do so.
On Maicos for example. I never had trouble with the early alloy ones. But they don't fold.
So I have collected NOS latter chrome plated forged steel ones. Usually at great expense.
I don't like to add weight, but they are brilliant if maintained.
AHH I'm a tight ass over the years I have collected stripped bent fold one's and welded to the the spline/clamp of choice, but luv to keep the original gear levers for well you know that original look