Topic: jerky drive train, cush drive ? 400 4

[kajtek]

hi all,

i have an anoying problem with my drive. once the bike has been ridden for about 20 mins (less in the hot), the drive train devolops a new lash.

as i pull away from standstill the bike takes up the slack in its gearbox/primary etc, and 2 seconds later is another jerk. i was told it was  worn cush drive rubbers which seems fairly logical, just wanted to get your opinions before i attempt the least fun bit of maintenance you can do on a 400 4..

along with this lash the bike becomes more 'jerky' in general, on/off the throttle, and it seems to 'bounce' off the engine braking when slowing down at lower revs. could this be the cush drive also?

bike has 22k apparently, but was stored for about 15 yrs in a shed.

thanks for any help/advice,

ashley

[bollingball]

Well in short it could be. Have you ever had your rear wheel off? If not it is a good idea and check other things like bearings Repack or get new double seal ones. Brake shoes if original replace. What condition are chain & sprockets? All this is one of the first things I do when I get a new to me bike. It is not that hard and you will have peace of mind. You don't want that thing locking up on you and you won't know until you take it apart.

                         Ken

It is not the milage so much with rubber parts it is time.

[kajtek]

Thanks ken, yeah had the wheel off before and bearings and shoes are good. sprockets and chain.. im currently 3/4 through their life i guess. holding out as long as i can as planning a trip in late august and will do them then. going for 520 sprockets with a x ring chain (i ride a lot and in the rain...).


ashley

[bollingball]

I don't know about 400s but the 500 or 550s have a problem with clearance up front with the wide o or x ring chain ?? Like I said don't know about the 400s but something to look into. I put new cush rubber on mine the old ones looked good but were hard as a rock. Felt so much better taking off and stopping well worth it and they are good to go for a few years.

[kajtek]

hi ken, with the 520 (as opposed to 530) chain clearence wont be a problem.

ashley

[kajtek]

well, looked it up and its only 35quid for a setup of cush drive rubbers so gonna order some.

is it possible that my strange lash could be from anywhere else? thanks

ashley

[Gordon]

Is it safe to assume the drive chain tension is set correctly?

[Cundalini]

if everything  is set up properly it is either worn bushes in the back wheel or a worn out primary drive chain

[dave500]

id guess a combination of worn primary chain and final drive chain,put the bike in gear with the engine off,and rock it back and forth as hard as you can,see any sprocket lash from the cush drive?if its worn that bad youll see it,i was born in catford by the way.

[Bodi]

I don't see how that's a worn cush drive in the wheel. A jerk after you've taken up the slack? This is usually a badly worn sprocket and/or very loose chain skipping a tooth. I've seen this many times but never had a skipping in the cush drive - it's basically impossible I think.
Driveline lash inside the engine is usually from a worn primary chain and primary drive cush rubbers. Worn clutch parts can also add lash when the clutch plate fingers get sloppy in the basket and on the spline. There's always some backlash in the primary chain and gears, the clutch, and the transmission gears - it can not be totally eliminated. But skipping is serious: usually the chain but the transmission can skip when the shifter forks get worn or bent, or when the drum grooves get worn.
The HyVo primary chain is very durable, plus expensive... and replacement involves a complete engine disassembly. I would look at the drive chain and sprockets first for this problem. If the transmission is skipping you should live with it (being gentle in the gears that are skipping) while sourcing the unobtanium drum and forks. If you let it skip under hard acceleration you risk breaking off gear dogs.

[dave500]

glazed steel plates in the clutch pack will give this effect on starting off,they slip as they should then grab in an in consistant manner,but still grab,if you can pull the clutch apart and sand blast the steels it will solve half of the #$%*ty clutch issues of any old bike,,they get glazed/polished and after a set of new friction discs later they get replaced to fix the problem,i call glazed steel discs as your problem,,it only occurs when slipping the clutch?

[kajtek]

thank you for all the helpful replies.

with regards to very worn sprockets/ skipping.. definately not as chain and sprockets still ok and set well with 20mm slack. also under heavy acceleration etc, no skipping or slipping, its only when moving off.

could of course have worn primary cush rubbers, i have to split the cases to change that no?

i wouldn't describe it as a skipping, its a 'notchy' feeling, and on closer riding inspection only happens when pulling of/changing gear, which all involve our good friend the clutch. so im thinking that glazed steel plates sounds like a very good suggestion.

its a daily rider so im gonna have to maybe purchase new plates, and might aswell stick new friction discs in, and see if i can do the whole thing in a weekend. on reading other threads the notchiness and tough clutch pull could also be from a worn basket, so will fix aswell by carefully filling the edges.

ashley

[bwaller]

I've seen a single bad roller/s in a drive chain show as something similar to what you describe.  From another direction you say it's been sitting awhile, could it be partially blocked pilot jets causing a hesitation that makes you think it's drive line slop?? 

[kajtek]

it was sitting for a while, though that was about 3 yrs ago. carbs are clean and runs good, i think whatever happens im gonna need to do chain, sprockets, hub cush drive, clutch basket, clutch plates...

thanks for all the advice

ashley