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ET: Engine (Twin) Kick Start Indexing Problem


G.L. Winter

Website User
VOC Member
My series B Rapide tends to jam from time to time at the initiation of the kick start down stroke. I fit a new kick start quadrant and ratchet pinion (G82 and G46AS) supplied by The Vincent Spares Company, but the problem persists. Does anyone have a suggestion? Thank you in advance for your kind help.
 

MartynG

Well Known and Active Website User
VOC Member
From OVR 33:
Often one reads about the need to “file” the lead tooth on a Kick Starter quadrant to avoid the dreaded “locking” of the kick starter. Attempting to force the kick starter once locked may result in damage to the kick start shaft, the kick start quadrant, the driven pinion, the rider’s foot or the rider’s leg – and any one or any combination of damaged items is possible.

Once the kick starter becomes locked the accepted release technique is to engage a gear then rock the bike back n forth till the kick starter becomes free, then gearbox back into neutral and try the kick starter again.

The attached picture is a close up of the lead in tooth on one quadrant superimposed over another quadrant clearly showing how it needs to be shaped. Note that its top surface slopes slightly towards the valley of the first “full” tooth.

In order to provide the best opportunity for smooth engagement between the kick start quadrant and the kick start driven pinion it is advisable to polish the lead in tooth, especially its upper surface.

There is also real benefit to be gained if the tip of each tooth on the engaged pinion is also polished.
25795
 

G.L. Winter

Website User
VOC Member
Thank you, sir, for your prompt and informative reply. It seems that my problem is not altogether unheard of. The picture, as always, is worth a thousand words. Quite a bit of metal removed from that lead tooth! I'll put the quadrant on the milling machine and have a go. One wonders why they aren't supplied with that profile in the first place?
 

fogrider

Active Website User
VOC Member
I made a test jig to see what was going on. If you file the first tooth, what will stop it jamming on the second tooth? It appeared to me from the jig that, if there is 10 thou wear on each of the two shafts and bushes involved, the teeth can jam. The cure, add 25 thou to the tip of the first tooth, that leads the engagement .
No, I haven't tried it on the bike yet, but it works in the jig based on accurately machined shaft centres.
 

oexing

Well Known and Active Website User
VOC Member
A Vincent is not anything special in this matter, you find same kickstart gear on any other bike. Trick is to grind the first tooth to half its height so it will just wipe over the first tooth on the small gear to engage in the second and move that so much so the second full tooth will do as it is meant to. No polish or funny shape is required, just half size.

Vic
 

fogrider

Active Website User
VOC Member
That seems to be the normal theory, but if you cut half the first tooth away, it misses, you might as well cut the whole tooth off !
I will do my 'add 25 thou ' mod this year, I'm sure the total wear on the small gear, the quadrant , the two shafts and the bushes, is what's behind the problem. If all dimensions were perfect, 'jamming' should not happen, the first tooth just touches and makes the second one fully engage.
Terry
 

oexing

Well Known and Active Website User
VOC Member
I cannot provide a good photo of kickstart gears for the moment, but half size first teeth are the norm for a reason. Anyway, don´t you see a situation when first tooth exactly meets its top with top of one tooth of the gear ? In just that position the mechanism jams no matter what you try. So to fight this effect you grind the first tooth down to half size.
Will try to do a picture.

Vic
 

fogrider

Active Website User
VOC Member
I understand what you're saying Vic , the teeth do sometimes happen to meet point to point exactly, jamming up. What I'm suggesting is that if the first tooth was 25thou taller, it could not jam in the first place, would start normal engagement which then takes up fully from the second tooth onwards.
I will do that mod , something to gain (maybe), nothing to lose !
Regards, Terry.
 

oexing

Well Known and Active Website User
VOC Member
Terry,
you cannot have one tooth higher, it will jam in the gear afterwards in the bottom . I did some tests tonight but the battery is low in the camera. Wait a little, I´ll post more photos.

Vic
 

oexing

Well Known and Active Website User
VOC Member
So I had a close look at what a different first tooth height will do to the jamming problem. I reduced the tooth in a few steps but this did not totally prevent the jamming. Seems the top on top tooth situation can happen at all sizes. I came to my conclusion that the best and safest way to get only very rarely any jamming condition is to modify all teeth on the small gear for very pointy tops and same goes for the first one or two teeth on the quadrant. As you can see in my Youtube clip below you have to very carefully set the pair of gears so they do meet head on head but this should be a rare case. I searched my stock of kickstart sets from various other types and most of them do have the pointy teeth that prevent blocked gears when working with same pointy first tooth on the quadrant. In the photo you see a new gear from the Spares Co. next to my reworked "pointy" gear, a carbide burr in the Dremel and diamond file did it last night. My old quadrant will get some welding at the first tooth for the pointy shape so this should do like in the video hopefully.
Great to have this forum as I did not think about this matter before but when checking my Argentinian box of parts I could see that there is a job waiting before problems only show after bringing the bikes on the road.

Vic

Youtube clip kickstart gear test:

BMW gear box:
26236

26237

26238


Vincent gear modified rear :
26239

26240
 

fogrider

Active Website User
VOC Member
That's an excellent review Vic. I see that the extra 25 thou I figured would only go in if there was at least that much 'slogger'. I tried a half-cut tooth, some time ago but found no real benefit. The best result was the leading tooth on the quadrant cut back at an angle on its' trailing face.(but retaining full height). That seems the least chance of end to end jamming as the two points are the thinnest on contact. I did spot that thinning/sharpening the teeth on the small gear would be a benefit but assumed the reduction in contact might result in damage to the gear.
Interesting problem, thanks for the comments and suggestions.
Regards, Terry.
 

oexing

Well Known and Active Website User
VOC Member
I was thinking about reducing the contact faces from sharpening the teeth but most wear and load is nearer the bottom of these. The very top of the teeth is retained and still case hardened.
Yes, the critical thing is the pointed tops of first tooth on the quadrant and all on the small gear. So half size does not do it but sharpening . I started on the BMW quadrant with the original tooth size and went lower in steps but yes,only the pointy feature would reduce the chance to jam.

Vic
 

Glenliman

Well Known and Active Website User
VOC Member
There was an article in mph discussing this problem with the Comet kicker.
I applied those methods to my problematic Rapide kick starter and I'm happy to say it now jams perhaps once in a hundred kicks rather than one in five or ten.
Prior to using the MPH info I tried gradually reducing the first tooth on the pawl.
After many tries and no success the first tooth was eventually reduced to nothing, at which point things jammed on the second tooth.
Before using the MPH info I flipped the pawl over so that it had a full first tooth again.
I tried it that way without shaping, but it jammed almost every time.
As I recall, very little shaping was needed to stop the jamming. That is a plus because this way you get a full kick, the first tooth is doing its job to start rotation.
The article was in MPH about four years ago from memory.
MSVH might recall the article. He and I both had the same kickstart jamming problem on our Rapides back then.
Both bikes are cured or greatly improved with the MPH Comet tooth shaping method.


Glen
 
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MartynG

Well Known and Active Website User
VOC Member
There was an article in mph discussing this problem with the Comet kicker.
I applied those methods to my problematic Rapide kick starter and I'm happy to say it now jams perhaps once in a hundred kicks rather than one in five or ten.
Prior to using the MPH info I tried gradually reducing the first tooth on the pawl.
After many tries and no success the first tooth was eventually reduced to nothing, at which point things jammed on the second tooth.
Before using the MPH info I flipped the pawl over so that it had a full first tooth again.
I tried it that way without shaping, but it jammed almost every time.
As I recall, very little shaping was needed to stop the jamming. That is a plus because this way you get a full kick, the first tooth is doing its job to start rotation.
The article was in MPH about four years ago from memory.
MSVH might recall the article. He and I both had the same kickstart jamming problem on our Rapides back then.
Both bikes are cured or greatly improved with the MPH Comet tooth shaping method.


Glen
see post #2 in this topic - its the same material
 

Glenliman

Well Known and Active Website User
VOC Member
Funny I read that and thought it similar to the MPH article, except for the amount removed.
I did not take nearly that much off of tooth 1.
Did you submit the MPH article? If so, my right knee thanks you!

Glen
 
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BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Funny I read that and thought it similar to the MPH article, except for the amount removed.
I did not take nearly that much off of tooth 1.
Did you submit the MPH article? If so, my right knee thanks you!

Glen
My right knee says "Thank You" every time I press the starter button. :D
 

oexing

Well Known and Active Website User
VOC Member
No matter what you do to the first gear tooth on the quadrant, it will jam with a shape that is not pointy. As I showed in my posting above, I had reduced tooth height in several steps but no joy. I could still find situations when gears jammed top to top. The ONLY way to minimise a likely hood of jamming is to sharpen the first gear, filed or not, on the quadrant, to a pointy shape so in operation you will have to position its top EXACTLY to meet one pointy tooth top of the kickstart gear. Both components pointy you will be challenged to jam them as shown in my video clip above .
The MPH photo really only confirms the pointy shape idea, polishing any sloping areas may be nice but not essential. The real trick is to have the top point stoned smooth so it will rather slip in any direction than jam.
Please test your ideas on your bikes by carefully trying to find a position of jamming, the wider any face on gear tops is , the easier you will get a jam.
The kickstart gear has wide tooth tops which is design flaw really. This has to be corrected with next production, basically. But I will not tell them at Spares Co myself, seems they won´t listen to the people, matter of pride maybe.

Vic
 

Glenliman

Well Known and Active Website User
VOC Member
I applied some synthetic grease to the pawl and pinion as well, making sure the tooth tops were coated.
The grease just adds to the slippery factor for the tooth tops.
It stays in place for a long time and can be reapplied thru the access hole.


Glen
 

Gary Gittleson

Well Known and Active Website User
VOC Member
It looks like I will have to remove my kickstart cover and examine things. In 15,000 miles of riding my D Rapide I have never experienced a kickstart jam. On the other hand, it was a pretty common experience on my wife's R69S. (All that was involved to resolve that one was to pull the clutch in and give it a soft kick.) If I get around to removing the cover, I'll post what I find, with pictures as necessary.
 

MartynG

Well Known and Active Website User
VOC Member
Funny I read that and thought it similar to the MPH article, except for the amount removed.
I did not take nearly that much off of tooth 1.
Did you submit the MPH article? If so, my right knee thanks you!

Glen
Hi Glen,

Yes - the OVR article was the first published - and MPH was a reprint of it. All written AFTER a lot of trial and error work with my Burman box - Note: I still get the kick start locking but now its like 1 in 200 not every second attempt. Now if it sticks DO NOT try to force it - that will just flatten the top of the clashing teeth. Put the bike in gear then rock it back n forth to release the jamb.

Martyn
 

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