Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Aye Gee 1977 on January 04, 2024, 04:02:47 PM
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After a mere 40 years on non-use, I thought now was the time to restore my beloved 400 - bought new when 1 was 17 years of age and then ridden to death before being retired at 65,000 miles
I have had a few problems - the rear hub housing was worn due to the bearing turning within; this was a recurring issue when in regular use. Not noted previously, the sleeve between bearing and axle on the drive side has worn - presumably it was turning on the axle rather than the bearing; fortunately the spindle is unscathed. Anyway, all stripped down including splitting the crankcases (for the second time in my ownership) and now being reassembled. The chrome plating seems to be taking an age - it won't be long before it is holding things up. I just hope they haven't lost anything.
Parts are not too hard - but I can't find a rear mudguard (so had to patch the holes with fibreglass(!). I managed to dismantle the horn such that it now makes a noise of sort - and only broke the plastic a little when reassembling.
Anyway, I did a silly thing and applied some heat to the petrol tap to loosen its screws - which was successful! I now know there is a tapered nylon bush inside - with a low melting point. Does anyone have a spare bush or bustd tap, please? If it matters, it has a 20mm thread.
If not, can anyone speculate whether (and which ideally which) of the cheapo petrol taps on ebay might yield a suitable innard
Thanks
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After a mere 40 years on non-use, I thought now was the time to restore my beloved 400 - bought new when 1 was 17 years of age and then ridden to death before being retired at 65,000 miles
I have had a few problems - the rear hub housing was worn due to the bearing turning within; this was a recurring issue when in regular use. Not noted previously, the sleeve between bearing and axle on the drive side has worn - presumably it was turning on the axle rather than the bearing; fortunately the spindle is unscathed. Anyway, all stripped down including splitting the crankcases (for the second time in my ownership) and now being reassembled. The chrome plating seems to be taking an age - it won't be long before it is holding things up. I just hope they haven't lost anything.
Parts are not too hard - but I can't find a rear mudguard (so had to patch the holes with fibreglass(!). I managed to dismantle the horn such that it now makes a noise of sort - and only broke the plastic a little when reassembling.
Anyway, I did a silly thing and applied some heat to the petrol tap to loosen its screws - which was successful! I now know there is a tapered nylon bush inside - with a low melting point. Does anyone have a spare bush or bustd tap, please? If it matters, it has a 20mm thread.
If not, can anyone speculate whether (and which ideally which) of the cheapo petrol taps on ebay might yield a suitable innard
Thanks
Add some images....[attachimg=1][attachimg=2][attachimg=3][attachimg=4][attachimg=5]
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I suspect it's unlikely that innards from a new aftermarket tap will be interchangeable.
Many now have rivets holding them together.
I would try & source an original used one I'd start with Steve at 400 bits.
I bought one off e-bay but the thread was wrong so had a refund, it also differed from the photo that showed screws, there are a couple of different sized threads iirc where it fits the petrol tank.
What confused me was there is only one part number listed in the parts book 16951-377-005 like this one below.
.https://www.ebay.co.uk/itm/115828691611
I have a dented early 400 petrol tank & the tap is a different size fitting to my later 400.
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I bought a tap repair kit from David Silver a few years ago and I'm sure that it included the nylon bush thingy.
I just had a look at DS and the repair kit doesn't include the nylon Bush. ☹
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I suspect it's unlikely that innards from a new aftermarket tap will be interchangeable.
Many now have rivets holding them together.
I would try & source an original used one I'd start with Steve at 400 bits.
I bought one off e-bay but the thread was wrong so had a refund, it also differed from the photo that showed screws, there are a couple of different sized threads iirc where it fits the petrol tank.
What confused me was there is only one part number listed in the parts book 16951-377-005 like this one below.
.https://www.ebay.co.uk/itm/115828691611
I have a dented early 400 petrol tank & the tap is a different size fitting to my later 400.
Thank you. I will ask if 400bits has anything to help. It does seem that there is more than one fitting size
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I bought a tap repair kit from David Silver a few years ago and I'm sure that it included the nylon bush thingy.
I just had a look at DS and the repair kit doesn't include the nylon Bush. ☹
I kept an old note of some problems with the bike that included need for a new filter etc. And joy of joys, I recently found a brand new refurb kit that I must have bought 40 years ago and had quite forgotten. It all went downhill when I put the blowlamp on the tap.
For those that like details, the large nut on the kit is plated whereas the one on the bike is plain brass
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Have you sourced a suitable replacement tap?
I'm interested in the outcome/solution.
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My solution, and only time will prove its worth, has been to cast a new nylon taper cock.
I tried reusing the old nylon, but it resulted in bubbles and voids as it boiled soon above its melting point. I have had more success using a petrol resistant 3d printer filament. It was cast in the ally tap casing with bungs to prevent leaks to unwanted ports. Some work with a sharp knife and files required when cast.
It seems to work but it will be tried for real later today.
The best advice is not to melt the one you have!
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I like the idea of using 3D printer filament. Keep us posted on the results...
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Great solution if it works! Here’s hoping. I’ll put my order in now for one! 😜
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Ahem! The DIY moulded tapered cock works a bit, but passes a little fuel even when closed. It seems an odd arrangement to me, insofar as the spring presses the cone out of its house, which can't help. Maybe I have misunderstood how it is meant to work - my cone was a strange shape following its relationship with the blowlamp.
The DIY method works sufficiently well to persuade me it could be done - given sufficient patience and skill. But in the meantime I have found someone that seems to sell the innards of the fuel tap https://nrp-carbs.co.uk/shop/index.php?route=product/product&product_id=5802
I have ordered a kit. It's said to be for a a 1975-76 model whereas mine is a 1977 CB400F2. I'll post an update when it arrives.
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That’s a pity but good you found a supplier. I’m sure the spring goes between tap and cone to push cone inwards thus tightening a seal.
Of course it will push it away from the seal behind the front plate.
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Please will you post dimensions of the cone when received. Be great if it also worked in my 550k1 tap .
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Ahem! The DIY moulded tapered cock works a bit, but passes a little fuel even when closed. It seems an odd arrangement to me, insofar as the spring presses the cone out of its house, which can't help. Maybe I have misunderstood how it is meant to work - my cone was a strange shape following its relationship with the blowlamp.
The DIY method works sufficiently well to persuade me it could be done - given sufficient patience and skill. But in the meantime I have found someone that seems to sell the innards of the fuel tap https://nrp-carbs.co.uk/shop/index.php?route=product/product&product_id=5802
I have ordered a kit. It's said to be for a a 1975-76 model whereas mine is a 1977 CB400F2. I'll post an update when it arrives.
Just a thought was your refurb kit for a single outlet tap or a double outlet. Don’t even know if there is a difference in the cone configuration?
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many moons ago, I converted my 400/4 tap into a twin outlet tap, so I would presume the internals are the same, having fitted another 2nd hand "cone" from 400/4bits since the first mod.
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OK - time to report back.
It's a single outlet tap; I'm not sure I know where the second outlet would link to?
The NRP kit arrived well; you don't get a lot for your £25 (cone, two screws and a couple of rubber seals. The spring fits between the lever and the cone, which pushes the cone into it housing which is logical even if it leaves a seemingly pointless void at its other end.
It was a tight fit and when assembled, bound the lever. The cone is, I would judge, turned from stock and had a small burr on the larger end, which I then removed hoping it would press home. But the tap still passed fuel when in the off position! Neither could I find space to fit the large washer so it got replaced by an O ring. This large washer prevent a petrol leaking out of the tap - it doesn't help seal the on/off/reserve function., so that's not the problem.
Petrol must be passing between the cone and its housing. The two seem to fit reasonably well - but maybe not as snug as they should be. Whether that is because the new cone has an incorrect taper or the tap is worn, I'm not sure.
Anyway, somewhat frustrated, I had another go at moulding a new cone. It's not perfectly petrol tight, but it's the best yet. I think the problem is with the two ports that lead to the tank. When moulded two limbs are formed which need to be cut off perfectly flush.