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Cush Drive too rigid

tjcassar

Well Known and Active Forum Website User
Non-VOC Member
I seem to go from sorting one problem to another.
After changing all the springs PD6 and PD27 in the cush drive, as well as fitting the following new parts: PD5, PD8, PD1, I was sure that my primary drive would be perfect. Dream on.... The result is a very rigid cush drive much more jerky then before. The springs seem to be so hard. No they are not coil bound as I tried 2 beforehand as instructions sent to me by Russ suggested. Has anyone had this problem?? I opened up the chain case all over again after about 300 miles of use. All seems well but it is as good as a rigid sprocket. This results in having to use more clutch in traffic slipping it to reduce jerking. Before putting it together again as is, can anyone shed some light on what I could do? I thought of removing the internal springs to lighten the loading. Would this be a bad idea??
Thank you for any valid suggestion.
Cheers.
Tony
 

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
Are you sure it is not a too loose primary or rear chain causing the jerking when driving in traffic?
 

tjcassar

Well Known and Active Forum Website User
Non-VOC Member
Hello Ed,

These seem to be fine and according to the advised tension. Both chains are new. I will check these again just to make sure once you pointed this out. What I notice is that the springs are extremely strong.
I thank you for your advise.
Tony
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Scotland's Vincent guru told me he thought that most ESA problems were the result of trying to pull away from 40 rpm (I exaggerate, as usual). I fitted series D bits to my C ESA, and despite Shadow first gear it's a pussy-cat in traffic. Without prejudice, maybe you need to use more revs?
Or maybe you need to 'phone Roy Price, and buy a new ATD that approaches "progressive" instead of a worn-out one (there are five clapped out ATD's in my box of eBay earners, next to the five ally large idlers all with one tooth missing, draw your own conclusions) that acts like a switch? Going from no advance to 34 (say) in an instant MAY lead to jerkiness...



I seem to go from sorting one problem to another.
After changing all the springs PD6 and PD27 in the cush drive, as well as fitting the following new parts: PD5, PD8, PD1, I was sure that my primary drive would be perfect. Dream on.... The result is a very rigid cush drive much more jerky then before. The springs seem to be so hard. No they are not coil bound as I tried 2 beforehand as instructions sent to me by Russ suggested. Has anyone had this problem?? I opened up the chain case all over again after about 300 miles of use. All seems well but it is as good as a rigid sprocket. This results in having to use more clutch in traffic slipping it to reduce jerking. Before putting it together again as is, can anyone shed some light on what I could do? I thought of removing the internal springs to lighten the loading. Would this be a bad idea??
Thank you for any valid suggestion.
Cheers.
Tony
 

timetraveller

Well Known and Active Forum Website User
VOC Member
tj, how many springs are in your shock absorber? The 'B' s and 'C's had fewer than the 'D's and more recently there have been some Australian ones with even more springs. The Australian one with a full complement of springs is certainly too stiff for solo use and even with a sidecar Dick Sherwin has found it better to remove three spring pairs. The 'B', 'C' or 'D' type should be OK and assuming that you have been supplied with the correct springs then you should be looking for the problem elsewhere. If you still have some of the old springs left then you could compare their strength with that of the new ones. In the past two weeks two local members have had problems with 'official spares'. One had an inlet valve seat fall out of a head that was brand new less than one year and 5,000 miles ago. The other was fitting new valves and guides and found that one set had the valve seriously loose in the new guide although whether the problem was with the valve, the guide or both I have not heard yet. Something seems to be going wrong with quality control so check the springs just in case!!
 

tjcassar

Well Known and Active Forum Website User
Non-VOC Member
Hi Tom,
I guesss not enough information was given in my short message. My Rapide is set with coil ignition. Its one of those with the bobweights inside the unit rather than the original ones. I have fitted two new Concentrics 928's. And, I have the long first gear!! however, prior to changing the cush drive springs, this did not bother me. I have also fitted the original clutch which works well and does not snap ( This was completly rebuilt so it is as it should be. Yes, I do try to pull off on top gear say from 40MPH, is this not correct?? If I do so, I get plenty of thumping felt on the foot pegs. This also happens on first gear when moving from stand still. I find that I have to rev up and slip the clutch rather than open the trottle slowly and pull up without jerks. It could be that I am slightly more advanced then I should. I will have a look at that now if you tell me thet the cush drive is not the culprit. I do not know these motorcycles enough to have experienced their habits. Is the cush drive one of their bete noir ???
Thank you for your input.
Tony
 

peterg

Well Known and Active Forum Website User
Non-VOC Member
Howdy Tony,

Compared to other machines with similar setup, Vin's are quite benign and response to modification in this area very linear. Your ESA works in concert with your clutch, ie, breakaway torque reaction on the latter has an influence over how much one must control power pulses through the primary chain which would lead to clutch slip, or ESA windup/release, which is controlled by spring rate against the ESA cam. As engaging clutch takeup with the aftermarket V2's of 15 years ago was nicely linear if the setup for even lift off was achieved without shimming the spring buckets up too drastically, one could remove springs from the ESA which I did as the Red Rap in my sig was not intended for sporting use and to be ridden solo. It is a docile machine that can have the throttle pinned back at 35mph in 4th with a 46 tooth on a 4.50x18 without any unpleasantness. On the other hand the Shadow is intended for sporting use, has a tall 7.2/1 bottom gear on a 3.50x19 thus presenting a roll-off challenge from a stop and full throttle application at low speed. The repro set of springs running through a stock Vin clutch were a bit too firm as I could feel yield in the lightening pilot clutch so I refitted my originals and then flipped the ESA washer over for a slight increase in spring rate for a happy medium.

Like Indians, Vincents were fitted with clutch arrangements designed to accomodate hanging chairs without modification so thus leave lots of lattitude for one to dial in just how much thud they want to see projected through the primary drive to the clutch. I would not hesitate to remove a few springs. I'd also make sure your ESA cam ramps glide over each other smoothly when rotated, any notchiness will sharpen torque pulse and snatch through the primary chain.

If it's any indication, on one of my Indians for which a sintered bronze clutch is fitted with extremely high coefficient of friction on take up as well as a very soft after market ESA installed on this engine that originally had none, I have now dropped from 16 springs to only 8 on the clutch with no slippage, this clutch can be activated with one's finger and power delivery smooth as an electric motor. It's all about getting that ESA to work in concert with one's clutch for a pleasant riding experience.
 
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tjcassar

Well Known and Active Forum Website User
Non-VOC Member
Hi Pete,
Thank you very much for giving me a better insight of things. I do however have the original clutch of the vincent and would like to retain this as it really grips well.

I am still wondering where the problem lies. Mind you, I did find the primary chain slightly loose, but nothing to write home about!!

Yes, the ESA ramps are fine. I just think that the springs are rather hard and difficult to press. But then. I am sure the strength of the engine can easily overcome the stiffness of these springs. So I need to know why the engine is so thumpy at low RPM. It is fine at higher revs.

Cheers
Tony
 
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