Author Topic: Re-threading carbs?!  (Read 1135 times)

Offline Alexrayz

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Re-threading carbs?!
« on: December 27, 2021, 01:43:08 PM »
Hey everyone!
I'm in the preparation and research phase for my carb rebuild for my 400/4.

These carbs have given me all sorts of headaches since I got this bike but truthfully it was my lack of knowledge that was the main culprit.
In a previous attempt at revuilding them I changed all the jets and tubes etc... On one of the carbs the idle jet thread got brittle and some bits fell into the conduct. It also meant that I couldnt get the jet to sit properly. The threading got so loose in fact, I didnt feel any resistance when screwing in the jet and I crushed a few jets thst way.
I ended up taking the damn thing to a mechanic near Paris specialized in 400/4. She managed to patch it up, saying that it was just a fix not an actual repair and I should be weary with the idea of rejetting that carb.

Fast forward today where I indeed want to rejet with originals that are graciously donated by Alan Kelly (the real MVP ). Now I don't know what was done in there but for the sake of the argument I'll assume a crap ton of red loctite.
If I remove the jet it is propable I'll find my mangled thread.
My question is do you think I could repair it with a helicoil?
Or too much of a risk of cracking the jet tower?

Cheers!

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Offline Nurse Julie

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Re: Re-threading carbs?!
« Reply #1 on: December 27, 2021, 02:43:44 PM »
No, you cannot repair that area with helicoils.
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Laverdaroo

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Re: Re-threading carbs?!
« Reply #2 on: December 27, 2021, 03:27:50 PM »
I dont think you said which carb it is,somebody on here might have a spare unit. If not,.....

https://www.cb-four.com/cgi-bin/shop/__Carburetor-Battery-Honda-CB350Four-CB400F-used__21-0375-S09_02.06.html


Dont look too bad and a working set for fair money.
Mornings are the invention of the devil!

1977 CB550F (current money pit!!)
2002 VFR800 VTEC (The Beloved)
1977 CB400F (the last money pit!)
1998 Ducati 748\853 conversion(sold :()
1980 ish CB750KZ in a billion bits (need to get rid, anybody want one?))

Offline allankelly1

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Re: Re-threading carbs?!
« Reply #3 on: December 27, 2021, 03:36:17 PM »
I dont think you said which carb it is,somebody on here might have a spare unit. If not,.....

https://www.cb-four.com/cgi-bin/shop/__Carburetor-Battery-Honda-CB350Four-CB400F-used__21-0375-S09_02.06.html


Dont look too bad and a working set for fair money.
Hi Roo

Hope you are well

That’s a good site and has a few bits at a good price

I shall add that to my list of favourites

Best wishes Al


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Offline Laverdaroo

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Re: Re-threading carbs?!
« Reply #4 on: December 27, 2021, 03:44:32 PM »
Hiya mate, hows the back? You mending, albeit slowly?


It's a great site and always have the bits that nobody else does and they're super dooper efficient being over in Germany. I've had several 'get out of jail free' moments with them.
Mornings are the invention of the devil!

1977 CB550F (current money pit!!)
2002 VFR800 VTEC (The Beloved)
1977 CB400F (the last money pit!)
1998 Ducati 748\853 conversion(sold :()
1980 ish CB750KZ in a billion bits (need to get rid, anybody want one?))

Offline Alexrayz

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Re: Re-threading carbs?!
« Reply #5 on: December 27, 2021, 04:24:06 PM »
I dont think you said which carb it is,somebody on here might have a spare unit. If not,.....

https://www.cb-four.com/cgi-bin/shop/__Carburetor-Battery-Honda-CB350Four-CB400F-used__21-0375-S09_02.06.html


Dont look too bad and a working set for fair money.
It's been a while will tell when I move to disassembly!

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If it aint broken don't fix it

Offline Alexrayz

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Re: Re-threading carbs?!
« Reply #6 on: December 27, 2021, 04:25:33 PM »
No, you cannot repair that area with helicoils.
Welp there goes that plan! Thanks for the info! Got your Orings, all good! You da bomb

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Offline allankelly1

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Re-threading carbs?!
« Reply #7 on: December 27, 2021, 04:25:49 PM »
Hiya mate, hows the back? You mending, albeit slowly?

It's a great site and always have the bits that nobody else does and they're super dooper efficient being over in Germany. I've had several 'get out of jail free' moments with them.
Hi Roo

Back is on the mend, and just being really sensible and on orders for both my wife and doc to stay out of the shed but still planning things

Got a six week minimum recovery time so have “spent” my time wisely as lots of bits have a bit of a lead time

Got a set of YSS piggyback shocks on order to go with the Dresda swing arm



Also ordered my Race Tech springs that are a match to my  body weight  (springs are linear and spring rate is up from the standard Honda 0.65kg / mm to 0.75kg /mm) And also ordered the Race Tech emulator kit for my front fork upgrade plus those adjustable preload fork caps



Lastly as running CB400N lower sliders, have lastly bought a Fastec fork brace in black to brace up the front forks too




Need now to rest but will have plenty to do once the six week recover is over and I am approved by the doc to start in the shed again

Hi Alex sorry for the thread hijack

Best wishes Al


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« Last Edit: December 27, 2021, 04:28:30 PM by allankelly1 »

Offline Laverdaroo

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Re: Re-threading carbs?!
« Reply #8 on: December 27, 2021, 05:14:50 PM »
Well hijacked Al,

YOU BLOODY TART ;) ;D ;D

Lovely goodies there bud. I didnt go for the piggy back ones for Mejima as I couldnt justify the cost, especially as The VFR is gagging for a rebuild/new one so snagged a pair of YSS ones for £100 in the box still, unused, which I thought was quite good!

Apologies Alex ;)
Mornings are the invention of the devil!

1977 CB550F (current money pit!!)
2002 VFR800 VTEC (The Beloved)
1977 CB400F (the last money pit!)
1998 Ducati 748\853 conversion(sold :()
1980 ish CB750KZ in a billion bits (need to get rid, anybody want one?))

Offline allankelly1

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Re: Re-threading carbs?!
« Reply #9 on: December 27, 2021, 05:45:26 PM »
Well hijacked Al,

YOU BLOODY TART ;) ;D ;D

Lovely goodies there bud. I didnt go for the piggy back ones for Mejima as I couldnt justify the cost, especially as The VFR is gagging for a rebuild/new one so snagged a pair of YSS ones for £100 in the box still, unused, which I thought was quite good!

Apologies Alex ;)
Hi Roo

Yes I admit it am a bit of a tart and yes totally agree piggyback rears are a tad expensive and OTT but just love the look of them

But the Race Tech changes are are not far behind, but I think the combination of the front and rear changes will certainly “change” the bikes handling for the better.

Anyway having a LC too gets you use to having an expensive hobby and only other bike expenditures in 2022 (If I get round to it) will be the 460cc motor build that is currently under a dust sheet till the rear disc and suspension mods are completed.

Have a good new year and I will now officially hand the thread back to Alex

Sorry Alex

Best wishes Al


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Offline Laverdaroo

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Re: Re-threading carbs?!
« Reply #10 on: December 27, 2021, 08:15:59 PM »
 ;D ;D ;D ;D ;D
Mornings are the invention of the devil!

1977 CB550F (current money pit!!)
2002 VFR800 VTEC (The Beloved)
1977 CB400F (the last money pit!)
1998 Ducati 748\853 conversion(sold :()
1980 ish CB750KZ in a billion bits (need to get rid, anybody want one?))

Offline Alexrayz

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Re: Re-threading carbs?!
« Reply #11 on: January 30, 2024, 09:31:15 AM »
Hey everyone, I am resuscitating this thread to give an update on the bike.

Carbs were fine, even more so with Al’s OEM jets.

The issue was the previous owner did an extremely poor job of cleaning the cylinders… It was more of a rebore at that point.
So much so that the pistons can wiggle somewhat… As a result there was almost no compression, cylinder 2 got 0,72bar for instance x).
 It goes to show how well these old things were built as it still somehow managed to tick over.

Anyway, this was way beyond my skill and equipment level so I had a local shop (Rolling Moto Le Mans) do a full diagnosis and rebuild. 
Sounds a bit overkill, but I already had spent a lot on repairs and figured it’d be best to just get everything done once.

Cost me a pretty penny (3k in total) But it is good as new now, with a kicker:
It was so overly bored out, it needed to be refitted with a big bore kit haha! So it is a 450 now and it purrs like a kitten!

I’ve been running it for a year now and apart from a bad oil pressure switch it’s been a good sport.

Yipeee!


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Offline taysidedragon

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Re: Re-threading carbs?!
« Reply #12 on: January 30, 2024, 12:16:15 PM »
Glad to hear that it's running well now. Enjoy! 😎👍
Gareth

1977 CB400F
1965 T100SS

Offline McCabe-Thiele (Ted)

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Re: Re-threading carbs?!
« Reply #13 on: January 30, 2024, 03:34:37 PM »
Good result with the big bore - what we need are some photos or a video of the engine running via U Tube!
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
http://www.sohc.co.uk/index.php/topic,23291.0.html

 

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