Clutch slippage in 4th gear, RPM gauge dropping

3andit

3andit

XS650 Enthusiast
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Hey everyone,
I have finally got my bike back together and the electrical sorted out! Thankfully that's done, but now to my new problem and puzzle! I took my bike out for a test ride to see how things were running working etc. and I noticed when shifting into 4th and rolling on the throttle the clutch would slip, then when I backed off for a few then slowly applied throttle it was ok. I haven't had it happen in any other gear yet, I haven't test it extensively enough due to work but where I got really puzzled was when that slippage happened the Rpms would climb and my tach would flutter then drop off to zero until the slippage stopped and it would return to what ever Rpms I was at.... To me when the slippage happens the rpm gauge should climb rapidly with the increase in rpm. And one other thing I noted was when I put everything back together my clutch was much harder to pull when the bike wasn't runnig but not terrible when running. Could that be related to my slippage ?

Any one have any thoughts or input on the matter ? I couldn't find anything when searching the forum and Google


Any help is much appreciated

Thanks in advance

3andit

*The tach is brand new so i don't think it's the magnets.
 
Normally, I'd think that those two issues would be separate and coincidental. But, the common denominator would be the primary drive gear. Best to open up the clutch cover for some clutch work, and thorough checking of the primary drive gears, oil pump gear and tach drive...
 
That is kind of what I was thinking too, but everytime the slippage happened the rpm would drop (tried it out three times), when I get back home on Thursday I'll open her up and see what I can see
 
As to the tach dropping off to zero......................you need to check both ends of the tach cable. Make sure that the centre square drive of the cable actually fully inserts into its respective home receptacle i.e. engine case drive unit or the tach itself.

Clutch slippage......................are you using the correct oil? Is the clutch adjusted correctly at the engine side case and at the clutch lever?
 
Hey guys finally got a chance to look at my bike. I pulled the clutch part and measures the frictions at 3.0mm and the discs are at 1.5mm springs measure at 34mm so all within spec I looked at the clutch pushrod and on the clutch side there is a short rod with the pad for pushing the plate then a ball bearing then a long push rod that goes out the other side to the clutch helix, then there is supposed to be another bearing correct ? Found out mines missing and the previous owner had taken the adjustment screw and screwed it all the way in to compensate for the lost ball...that's probably where my issue is.
Now my question is when I do research it says 75s only had one ball bearing and one single long rod or am I wrong ?

Oh and as far as the rpm gauge goes all the gears Are in good order and all that jaZz
 
Yes there needs to be a ball inside the clutch worm. a 5/16 ball bearing is perfect. It should be staked in the worm so it doesn't fall out but a bit of grease and watching that it's in place when you assemble is OK. remember to run the cable adjuster all the way in at the bars before you set the screw at the cover then adjust the cable.

Check for a binding cable, check cable routing for sharp bends, straighten the elbow at the case to nearly straight. Lube the cable, check the clutch lever pivot bolt for slop and lube it. Guys are often looking for a home run clutch fix but it's usually a series of bunts and base hits that "fix" it.
 
Most often you start to notice clutch slipping in 5 gear first, it then moves down the gears as it gets worse.
Your springs may be the right height but still be weak. While you have it apart I would replace them. 650central has several sets to choose from. From a bit stronger than stock on up.
Leo
 
Well I ordered new clutch springs and frictions just because as well as a new helix and bearings. When I get home from work next week I will install it all and let you know how it turns out
 
I looked at the Tach and the cable issue briefly. Verified that the all important oil pump is indeed working and I checked all the gears and they were contacting correctly and in good order so that leads me more to the cable or perhaps a faulty tachometer.
 
Sometimes those new clutch springs are too stiff, much more than factory, resulting in a very hard pull. If the plates & such are ok, often I will only replace every other spring, with excellent results.
 
Hey guys I forgot to up date you on the bike. So I put the new clutch frictions and springs in and adjusted the worm gear accordingly. All clutch slippage is gone now which is great! One question I have is on these bikes can I adjust the clutch so that it grabs a little later? Right now it wants to grab as soon as I start to let the lever out. And as far as the tach goes it needs an extension I believe the cable isn't going all the way into the tach and slipping out at higher Rpms
 
With the oem worm screw arrangement it is not advisable to alter the engagement of the clutch because you won't get the necessary plate seperation which will cause a dragging clutch. The dragging clutch will then make it difficult to find neutral or shift properly.
 
The factory spec for the worm adjustment is "just snug" then back off 1/4 turn. Many of us cheat that a bit, just 1/8 turn or so. Cable routing is critical. As 2many demonstrated with his cable testing regime, just one "too sharp" bend in the cable results in excessive "take up" needed before actual pulling of the clutch starts. But ippy is right also, the "correct tension" range is quite limited. Change one end too much and you don't have enough movement on the other.
 
Thanks for all the help guys!
Now that I have those little issues solved I have 2 more that have risen doh!!

I know these two issues are related

First issue is when ever I stop at light or anything and I am waiting to go my bike will stall if I don't blip the throttle every so often. Is this a too rich or too lean issue ? The bike idles at about 1400rpm

Second issue is while cruising around at 30-60km/hr the bike will stutter and faulter a bit. Again a carb issue. But where do I start? When I bought the bike I cleaned the carbs and checked it all out the butterflies are synced or damn close to it. I haven't done the dead cylinder method yet as I have a pamco and I'm not 100% clear on how to ground my caps safely. Ie. Can I clamp a wire to the plug threads and the. To a fin?

The bike is a 75 with BS38s so no barbs for vacuum syncing

Thanks again guys
 

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