Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: amx1992 on November 20, 2020, 08:50:28 PM
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I know these aren't available, so I thought id have a go making a set
The originals were rock hard, split and had shrunk, allowing the play between the clutch and drive gear
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I made them out of teflon, because I didn't really have anything else more suitable to hand, i might try making a poly urethane set now I know how easy it is, but not sure how they will hold up to the heat and oil.
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https://youtu.be/McekCbIILg4
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Kevin, TTR 400, who manufactures some wonderfully engineered CB400/4 parts and sells them all over thd world, tried making them but they failed quite quickly. I can't remember what he made them of though.There is a thread on here about them somewhere. I hope yours work.
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https://www.uksealants.co.uk/soudal-silirub-ht-n-high-temperature-silicone-sealant.html
Maybe something like this if you made a mould in teflon.
Or mould in situ.
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Here is the post I was talking about earlier
http://www.sohc.co.uk/index.php/topic,18619.msg166659.html#msg166659
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Intresting, it seems viton would be the way to go, but to soft to be machined. I think these teflon ones will act more like the acetal ones ttr made, not much give, but might hold up better.
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Intresting, it seems viton would be the way to go, but to soft to be machined. I think these teflon ones will act more like the acetal ones ttr made, not much give, but might hold up better.
Nice looking adaption - I'm surprised DS or CMS haven't found a suitable replacement part.
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Years ago I had the dampers inside the CB750 primary drive analysed at Hul Uni. to determine what they are made from.
It turned out they are made of nitrile rubber but it is compounded with extra additives to give superior oil resistance to swelling and hardening at high temperatures than 'standard' nitrile rubber. I got the sample from a NOS CB750 part that had had the rubbers swapped for a racing setup. I used to work with the guy who owns this company linked below and he could definitey compound and mould the correct rubber as we used to make rubber parts for the automotive industry, at the P.L.C. we both worked for but not sure about tooling costs. Last time I spoke to him he was restoring a Gold Wing so he talks our language.
https://www.yell.com/biz/antivibe-hull-ltd-hull-2761000/
Following my analysis of the part, I this I found that a deidicated CB750 club in Germany was re-manufacturing them but only selling to club members.
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The CB400F appears to have 3 cush drives, clutch, primary gear and rear hub. Does making one with less give in it have any disadvantages? Replacing the dual mass flywheel on a car with a solid one often works but I have also heard of increased vibration and even crankshaft failure. Be interesting to see the outcome of the Teflon ones as I think mine need replacing.
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Intresting, it seems viton would be the way to go, but to soft to be machined. I think these teflon ones will act more like the acetal ones ttr made, not much give, but might hold up better.
If your Teflon ones work there is a business opportunity here !
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The CB400F appears to have 3 cush drives, clutch, primary gear and rear hub. Does making one with less give in it have any disadvantages? Replacing the dual mass flywheel on a car with a solid one often works but I have also heard of increased vibration and even crankshaft failure. Be interesting to see the outcome of the Teflon ones as I think mine need replacing.
Yes to the question of disadvantages. All of these system components are specifically developed and included to control, mitigate or reduce the unwanted forces inherent within the working design of the engine and transmission in getting disparate frequencies to not cause breakage and improve lifing of individual components.
The dual mass flywheel is an interesting (valid in this thread context as some of the measures are easily discussed) comparison as it incorporates more than one method. Originally responding to diesel engines as they became more prevalent in refined passenger cars.
With a four cylinder diesel originally having a heavy flywheel to absorb slow pulse vibrations at low crank speed, the need to lighten the flywheel effects and speed up engine response to better match petrol motors asked for reduced mass, but then they shake like hell, making it very harsh at tickover.
The dual mass allows one part of the flywheel to spin independently of the other over a controlled maximum angle and restrained by springs. This lets one piece oscillate with the crank pulses while not transferring the peak to pass into the transmission. At low speeds the two are operating close to their optimum absorption characteristics, hence the crankshaft is pulsing with big frequencies but you don't get to feel it. Like have suspension within your drive line.
As the crankshaft speeds up the frequency doesn't have the peaks and troughs at such high amplitude so the two parts become much more in synchronisation, but the springs in the flywheel will still cushion the drive especially if you abruptly shut the throttle as a diesel has pretty severe closed throttle deceleration. It's all part of how refined current diesels feel and you could see that by not allowing this movement to happen then the peaks of the frequencies are just rattled through the component set to it's detriment.
There's little telltale signs of how effective it is too. With many diesel engines running one way clutches on the alternator as letting the crankshaft oscillations free the ancillary drive also pulses at this rate. The alternator pulley then lets the speed up part of crank pulse (firing event) accelerate the alternator spindle, but as the crankshaft pulse slows the alternator can over run the belt drive and not clatter it.
As injection development has improved both timing and accuracy, this need is getting less with low speed pulses significantly reduced when no load is being used. Which is why they sound much better nowadays in any size diesel engines. This has a parity with how we set idle circuits on these Honda engines too, it illuminates how critical and useful the adjustments are on the carb sets in use.
This is all happening in our engines, but less seen. Which is why the various cush drives are incorporated.
The cush drives within the Honda engine are primarily to mitigate pulse peaks imposed on the primary drive chain in my view. Its a very clever drive system but with very very simple bearing properties in the structure. They are also susceptible to vibration peaks which can dramatically shorten their life, making the absorption curve of the rubber components vital to their function.
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To add, as these measures are incorporated into the original design, it follows that the design and R&D process ultimately leads to excess being removed from the components as part of improvements in performance.
Simply deleting or compromising them then steps the design in the opposite direction, reducing component's life ultimately.
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For info:- Update on on previous thread:-
http://www.sohc.co.uk/index.php/topic,18619.msg166659.html#msg166659
Viton clutch damper rubbers now completed approx 700 miles mostly local driving, Recent check revealed clutch basket freeplay still non exsistant and no vibration or noise noticed from clutch area. I would suggest vition as a possible solution.
Will feedback after 1500 miles.
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Tried contacting Max few times to no avail. I'm desperate to find these basket cushions. Anyone have any contact with him or know of anyone else supplying these.?????
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I have contact with him Eddie, last time we talked he told me he was waiting for some new Viton sheeting to arrive.
When he's made some more I'll buy a couple of sets and sell them on here for him, might be cheaper than his Ebay price but I haven't negotiated a price with him yet so we'll have to wait and see.
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Forgot one thing Eddie, there are 2 versions of the rubbers, Max only makes the one like are shown at the beginning of this thread so you'd need to make sure yours are the same type.
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Heard from Max, he'll be making some more for the 408cc version, 8 sets he says, and also 2 sets for the 398cc version. Cost will be £50 a set, that price may be if he sells them on Ebay direct to you, if he sells them through me then I suppose I'd have to add on P&P as well or I could possibly ask him to post direct to you. Lets wait and see what he does.
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new member here. recently purchased a 1975 cb400f in Varnish Blue. I am definitively in need of a set of these cushions. I bought a spare clutch basket on eBay and it is very loose a rattly as well. also would like to find 6 low profile bolts like i have seen to re-assemble it. please let me know when they become available.