The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: derek taylor on 20.04. 2014 19:56
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had a run out yesterday flash run well until coming home, stopped at some lights going up hill wife on the back when we set off the bike jerked twice as if the rear chain jumped teeth.
the chain does seem a bit slack, but if that's not the problem what else could it be ?
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Hi derek, was the chain loose without either of you on board ? Or just with you ? I think two up that could make it looser. what are the teeth like and the condition of the chain. Just adjust the chain and try it then decide what do do, regards bob
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Could it be the cush drive jumping? If so you both need to lose weight *eek*.
Cheers *smile*
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had a quick look tonight chain is a bit slack wile an center stand
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Derek the chain will be loose while the bike is on the centre stand. There is a thread here that deals with how to adjust your chain.
You need to have the bike sitting on its wheels and get someone to sit on the pillion seat and then check the chain, it tightens as the suspension compresses.
If the chain was jumping while you where riding the bike the chain would have to be horribly loose or the sprockets totally worn out.
You also need to check the cush drive, it can not actually jump unless it has come loose and if that is the case it needs fixing immediately.
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was ok when riding jumped when we set off
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Checked the primary chain reciently ?
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Broken driveshaft on the crank or sheared keyway on mainshaft.
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Could it be the cush drive jumping? If so you both need to lose weight
or the cushdrive nut is bidding farewell and adieu to it's neighbours *conf*
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have added a pick to first thread
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Good one, that looks all in reasonable order
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Wheel spin ???? *????*
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Checked the primary chain reciently ?
I allus have one at eleven!
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just been thinking its only done it since i fitted the new clutch plates.
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G'day Derek.
Other things to check. Primary sprocket alignment and clutch basket bearing wear. Under load like you described the basket could cock off a bit causing momentary slip.
Cheers
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just been thinking could the lugs on the new clutch plates be digging into the basket (them being sharp)
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G'day Derek.
Have you ridden the bike since? Have you tried to replicate the situation?
I think I'd be stripping the primary down again. Check for Wilko's suggestion of main shaft key.
Cheers
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been on the bike its done it again just jumps when letting clutch out in 1st gear otherwise its ok.
carn't grasp the thing about the key way if its slipping the key must be sheared if that's so it would slip all the time.
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My thinking - if it's just first gear it's maybe due to first providing more torque then any other gear which might point to the key theory or it's down to first gear itself like in the box somewhere
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That could also point a worn/chipped dog or bent selector fork.
Cheers
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I'd concur with Muskrat and from the picture it appears your sprocket on the clutch basket also look fairly worn, which if poorly aligned could be hooking up when you pull in the clutch.
Tie the clutch lever to the bars so the clutch is disengaged and look at how it rotates/aligns, chain alignment is important.
But your front sprocket tooth profiles look far more healthy than the clutch sprocket teeth do.
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right then not stripped anything down yet but took it for a run yesterday, its the clutch you can feel it slipping and biting through the leaver as you let it out.
two things tho it only seems to do it when the engine is hot have also noticed some slack has appeared in the cable at the leaver. also if you pull up at a junction in first gear and pull the clutch in its wanting to creep forward.
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keep in mind you can always remove the primary cover and run it with everything visible.