Honda CB750 Sandcast Forum
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Author Topic: Kick Starter Rubber  (Read 3020 times)
kp
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« on: May 21, 2014, 06:50:45 PM »

Opinions Sought.
Maybe this has been discussed or mentioned before but I just don't recall. I have noticed that all early bikes which we see as being unmolested etc etc all have a kick rubber that is way too small in length for that foot lever part. Later bikes and certainly later genuine kick rubbers are longer and fit the full length.
Anyone care to comment, advise, discuss. I've always been intrigued with this. Maybe they have just shrunk with age but I doubt that   Huh
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Yabba Dabba KP
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« Reply #1 on: May 21, 2014, 08:54:30 PM »

I have also noticed this and after looking at quite a few of these "shrinkers" versus new rubbers, I think it is just that. Pretty sure the original part number was 28311-250-000 that was used on 305's, 350's, 450's, and SC, K0, and K1 750's. It was then superceded to 95011-52000 and later superceded to 28311-329-000 which I think is current. Both of the latter rubbers were a little fatter and longer. Interested to hear if anyone has additional info.
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Steve Swan
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« Reply #2 on: May 21, 2014, 11:28:38 PM »

Great observation, KP and Keith.

kicker rubbers that came with 4363 and 232 are same length of short, no indication kickers were not original to machines nor that rubbers were replaced, both have the "HM" logo.  hard, i always assumed with age; with great effort or not at all could i rotate them by hand on the pedal shaft, much less even try to pull them off.  i gave them a long dip in boiling water; softened and readily came off.  i would think they would have had to be softer from the factory, how else could they get such a hard rubber on ?!?

2157 kicker not original to bike, long, small diameter rubber, no logo, same rib design and soft.  

in the past, i've ordered replacement rubbers from Honda, smaller diameter, long type, soft, no "HM" logo, so i did not use them.  i don't have them anymore, so i have no idea what the pn was.  i do remember being impressed how soft the replacements were compared to the 232/4363 rubbers that came on their kickers.  

i know the later 750's came with larger diameter rubbers and quite soft; around the K3 or K4 generation, i believe.

i wonder if the original production rubbers were a different composition material than the later production replacement rubbers..... ??

i've always wondered if they shrunk or came that way...  sort of an 'eyesore'.  kind of assumed they may have shrunk, because i could not rotate them on the shaft suggesting the diameter had shrunk has well as the length and because they were so hard.... imho.

for me, if i recall correctly, seems the rubbers with "HM" are nla, hard to find good  logo type that are not nicked or gouged.

« Last Edit: May 21, 2014, 11:47:27 PM by Steve Swan » Logged

Honda CB750 Sandcast Forum
« Reply #2 on: May 21, 2014, 11:28:38 PM »

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corsa65
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« Reply #3 on: May 22, 2014, 01:24:15 AM »

I going to agree that they have shrunk. The same goes for the passenger foot peg rubbers with the HM logo. As they shrink they no longer offer the resistance to keep the pegs in position. I haven't decided wither to add rubber spacers to fill the gap or just use modern pieces without the logo.
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Steve Swan
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« Reply #4 on: May 22, 2014, 02:15:51 AM »

corsa65, another great observation. 

indeed, i to have noted those passenger peg rubbers lose their length and become unable to hold the peg in position !

Crosa, what is your name ?  We like to get to know each other !
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Erling
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« Reply #5 on: May 22, 2014, 05:27:47 AM »

Can just ad my observations. Have never tried till now to turn the rubber on the kick starter. And it does turn. But still some 5mm short! Never really noticed its actual length. It fits up to the outer edge though. Might it not have shrunk equal in both ends if shrunk at all over the years? My kick has never started the motor, only used for turning it over by hand these past 35 years engine stands idle. From new the kick came off after but a few days. CB250 footrests had come on. 2" higher and giving a better feel than the original hinged ones. Kick couldīt turn after that. Never a problem. As for the rear footrests, they seems more tight in an upright position, than when down for use. Do not remember if they rattled in the day, they were soon exchanged for a piece of flat iron bent at an angle in over the silencers. "rubbers" were oversize garden hose. Could not have girlfriends feet and legs flaring so far out to the side. At that time we used to creep up between car rows, to be first at traffic lights. Behaviour has changed since though.
    Erling.
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Marcello Tha
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« Reply #6 on: July 12, 2014, 12:05:39 AM »

I tried Steve Swan's teory and put the kick start rubber in boiled water for 1 minute, I was just trying to rotate the honda logo. Worked fine. My kick start rubber was very short, 64 mm, then I put another minute in boiled water, streched the rubber and put it in a recipiente with water and ice, made this twice, now my rubber has 69mm, it is not too much, but after 45 to grow up something is realy a miracle.  Grin Grin Grin

Marcello
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Marcello Tha
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« Reply #7 on: July 12, 2014, 09:38:01 PM »

I have noticed that all early bikes which we see as being unmolested etc etc all have a kick rubber that is way too small in length for that foot lever part. Later bikes and certainly later genuine kick rubbers are longer and fit the full length.

Dear KP;

I noticed that the lenght between the rubber part number 28311-200-000 (harder and with HM logo) and the superceded 28311-250-000 (softer and no Hm logo) are almost the same, about 69 mm, but I found a diference between the lenght of a sandcast and a K2(?)-onward kick starter that is 8 mm longer.

Marcello
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vnz00
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« Reply #8 on: April 13, 2018, 09:06:58 PM »

I thought this might shed some light on the early kickstart rubbers.  Measured length was 73mm.

Ill update with the part numbers soon.


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Steve Swan
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« Reply #9 on: April 13, 2018, 11:31:27 PM »

Steve - are those covers soft rubber like they appear to be?  since they are photos, it's hard to tell, but the "HM" appears indistinct and there are molding seams/tags on the covers.  the pictures make them appear either as a later factory production or a non-factory reproduction.

my own personal belief is the covers that came from factory in '69 were not rubber but a plastic material, and the "HM" is quite distinct.  of the about 25 or so April '69 through at least K1 bikes i have hands on, all had this non-rubber type cover which (at least to me) is a type of plastic.  i had ordered covers from Honda in past years, they were fat rubber type and no "HM" logo.  i wound up getting lucky finding good used original plastic-type rubbers on projects i needed them for.  

fwiw, those hard plastic rubbers can be a bitch to remove unless they are heated, and can get ruined pretty easily if trying to remove them cold.  i put a kettle of water on the hot plate and when the water's near boiling, i dip the end of the kick lever with the cover in it til the thing gets hot, they slide right off wearing a pair of insulated leather gloves.  i've found with other work, on bikes that use actual rubber covers, i will heat the part that needs a rubber put on, heat the rubber, and this almost always keeps the rubber from splitting, especially if it is an original rubber.  and i'll use a dab of synthetic grease to help the thing slip on more easily.  if the cover cools off before i get it on all the way, i just dip the whole thing in the pot of hot water and have another go.  and i have found i can stretch them a bit when hot.
« Last Edit: April 14, 2018, 12:04:57 AM by Steve Swan » Logged

vnz00
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« Reply #10 on: April 15, 2018, 09:56:17 PM »

Hi Steve,
Sorry for the delay.  I had to do a bit of research.
Just to clarify their history, the parts came from a seller who sells NOS Honda parts.  I don't believe them to be repops.  the HM logo is crisp and clear - its just the enlarged pics don't make them look crisp.  The parts are a firm rubber, and they do have mold flash on them too.

I know what you mean about the plastic material used - they would have originally been made from a similar material to the rear passenger peg rubbers with the HM logo.  They also suffered the same fate which Im sure a lot of us have noticed - they shrank and made it hard for the passenger pegs to stay up when not in use.  I have NOS versions of the passenger peg rubbers which are a shinier material but quite soft none the less.

My new KS rubber in the picture, Im sure is genuine Honda.  If a modern repop, Im sure we'd have seen more of them since I bought them a few years ago and the quality is often not as nice.  Im also quite sure its a different material to the passenger peg rubbers I have which are NOS.  Having said that, Ill let you know if they age and shrink to a similar size/consistency as the originals in 10yrs time  Wink

Comparing my KS rubber to the nicest original version I have, the original is 65mm long, this is 73mm. They both have 12 ribs overall and an identical profile down to the mold flash lines and thickness.  The original mold flash lines are much finer, perhaps due to wear and age.  The flash lines are only different in that they appear in different locations to each other, perhaps meaning a different factory made them/different molds.  Not incredible if they are different material.  The 73mm rubber also fits the kickstarter lever tang perfectly.

While these may be NOS, theres no guarantee they havent aged and shrunk as well, however they appear nice and supple and dont bunch up on the lever when fitted.

I have updated this post with pics of the nicest original KS rubber I have - it appears I need my eyes checked and the mold seam lines are identically located
« Last Edit: April 15, 2018, 10:11:41 PM by vnz00 » Logged
vnz00
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« Reply #11 on: April 15, 2018, 10:17:26 PM »

Pics of my used original KS Rubber and new KS rubber showing similar mold flash.
Pic of original SC 1095 KS Rubber.
« Last Edit: April 15, 2018, 11:33:52 PM by vnz00 » Logged
kp
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« Reply #12 on: April 16, 2018, 04:24:30 AM »

Forget the rubbers, I'll have the bike please  Grin
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Yabba Dabba KP
Steve Swan
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« Reply #13 on: April 16, 2018, 09:29:40 AM »

Steve - Good stuff!   Thanks !
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Don R
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« Reply #14 on: April 17, 2018, 11:29:14 PM »

 On the passenger pegs that tend to flop down, I've lubed them with silicone spray and slipped a fat o ring in at the end of the rubber. It's not obvious and helps the old rubber hold the peg up.
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