Author Topic: Carb O-ring sizes  (Read 6216 times)

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Offline danfr

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Carb O-ring sizes
« on: May 12, 2013, 04:40:48 PM »
Hey guys,

I'm going through my CB350F carbs. A lot of the O-rings are old and brittle, and the top gaskets need to be replaced on one of my carbs.

Does anyone have any leads on reasonably priced O-ring/Gastket kits? I just finished up 6 months of schooling so every dollar counts.

Or does anyone know where I can find the sizes?

Cheers

Dan
« Last Edit: May 12, 2013, 09:51:42 PM by danfr »
Apollo Motorcycles
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71 Commando
74 CB750K
74 CB350F

Offline danfr

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O-Ring sizes
« Reply #1 on: May 12, 2013, 09:50:47 PM »
Does anyone know where I can find the sizes for CB350F carb O-rings. I have a shop in town that should be able to find the O-rings I'm after, but I cannot find the sizing other than the main jet O-ring (3mm O.D. x 1.2mm thick)

I'm looking for the O-ring size for the float valve seat seal and the 4 fuel connect.
Thanks

Dan
Apollo Motorcycles
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71 Commando
74 CB750K
74 CB350F

Offline bryanj

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Re: Carb O-ring sizes
« Reply #2 on: May 12, 2013, 11:00:14 PM »
Honda never listed the individual sizes for the 350/400. I can give you the sizes for the 500/550 but cannot guarantee they are the same.

Safest way is to buy one Honda kit 16010-333-004 and size the O rings from that
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline danfr

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Re: Carb O-ring sizes
« Reply #3 on: May 12, 2013, 11:31:39 PM »
thanks for the reply Bryan.

I did some more digging around and I think I found the sizes although I'm not too sure how credible the sources are. I figure I'd post my findings in case someone with a 350F or 400F is looking....

Main jet O-ring:
1.2mm cross section x 3mm I.D. Quantity 4

Float Valve Seat Seal
1.5mm cross section x 5mm I.D Quantity 4

Fuel Connect
1.9mm cross section x 5.8mm I.D Quantity 12

I think I remember Hondaman stating that most metric O-rings range by 0.5mm so I may need to do some rounding. Also I think he mentioned Buna fits a bit bigger than Viton or Visa Versa...??

I still need one top gasket. Maybe I'll search the salvage yard this weekend.
Apollo Motorcycles
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71 Commando
74 CB750K
74 CB350F

Offline busa

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Re: Carb O-ring sizes
« Reply #4 on: May 13, 2013, 02:43:33 AM »
you could try csml they have online microfische  that give you sizes  right through everything carbs to engine  and part numbers

www.cmsnl.com

Offline Rudi91

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Re: Carb O-ring sizes
« Reply #5 on: May 13, 2013, 03:11:11 AM »
I've ordered some carb revision kits on ebay from cruzinimage for my cb350F. The quality is pretty good, I could buy 4 kits for the price of 1 keyster kit over here.
U can find it here: http://stores.ebay.nl/cruzinimageco1484
I think he also has gasket kits.
CMSNL is insanely overpriced imo.

Ordered an extra kit last week cause I lost my float needle, and he shipped it within two hours. Went from Japan to the Netherlands in just 4 days!
EDIT: The cost of one kit was less then ordering a float needle + seat over here ;) and they are the same quality.
« Last Edit: May 13, 2013, 03:12:55 AM by Rudi91 »
CB350F '73

Offline Shane72

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Re: Carb O-ring sizes
« Reply #6 on: May 13, 2013, 09:36:36 AM »
Another endorsement for the seller listed above.

I just got this kit for my Wife's '74 350f that was leaking from the overflows...

 http://www.ebay.com/itm/140962302751?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

While the pilot jets lacked the numbers that were on the originals, the kit was comprehensive, and by the evidence running it since, seem to be of good quality.

Took just a few days to ship to Iowa, happy customer.

Good luck,

Shane
I mount and balance MC tires--while-you-wait service by appointment.  Send me a PM.

Offline danfr

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Re: Carb O-ring sizes
« Reply #7 on: May 14, 2013, 10:34:08 PM »
Do you guys know if O-rings for the fuel connect lines are included with the kit?

http://www.ebay.com/itm/140962302751?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Apollo Motorcycles
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71 Commando
74 CB750K
74 CB350F

Offline Shane72

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Re: Carb O-ring sizes
« Reply #8 on: May 15, 2013, 12:01:11 AM »
I didn't use all of the parts in the kit...just the float needles and seats, pilot jets and main jets.

The float seat and main jet come with the appropriate o-rings pre-installed, so the o-rings you see pictured in the ad are all in addition to those needed inside the float bowls.

Since the only issues I had were in the float bowls, I'm saving the rest of the parts for future.  If the o-rings supplied don't do what you're asking, I'd be surprised.  If the fuel inlets are similar to my 750, they look to be similar in size to the ones I replaced there last year.

Good luck, hope this helps.

Shane
I mount and balance MC tires--while-you-wait service by appointment.  Send me a PM.

Offline Rudi91

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Re: Carb O-ring sizes
« Reply #9 on: May 15, 2013, 12:28:00 AM »
I've done the same as Shane. I also had a couple of O-rings left and I think they are for the fuel connect lines. They do look about the same size, but I can't guarantee it since I didn't use em and I've just put my carb's back together and on my bike.
Just send him a message on eBay? He doesn't speak english that well but he responds fast.

The float bowl rings are just plain O-rings and aren't shaped for the bowl so they can give some problems.
If u've got the time for it u can do the same as me. I first "glued" em in place with liquid sealant then left em for a few days. When u take em out now they will have the proper bowl shape.
I then removed the sealant and could just place em with some oil or grease to keep them in place.
« Last Edit: May 15, 2013, 12:32:40 AM by Rudi91 »
CB350F '73

Offline Rudi91

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Re: Carb O-ring sizes
« Reply #10 on: May 15, 2013, 05:07:11 AM »
Another endorsement for the seller listed above.

I just got this kit for my Wife's '74 350f that was leaking from the overflows...

 http://www.ebay.com/itm/140962302751?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

While the pilot jets lacked the numbers that were on the originals, the kit was comprehensive, and by the evidence running it since, seem to be of good quality.

Took just a few days to ship to Iowa, happy customer.

Good luck,

Shane

Don't want to highjack this topic but at what level did u set the needles?
I can't get my 350 running well and I've red the position of the needles is different with the aftermarket ones compared to the original Honda ones. They seem a little longer than the original ones.
CB350F '73

Offline Shane72

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Re: Carb O-ring sizes
« Reply #11 on: May 15, 2013, 10:13:13 AM »
Another endorsement for the seller listed above.

I just got this kit for my Wife's '74 350f that was leaking from the overflows...

 http://www.ebay.com/itm/140962302751?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

While the pilot jets lacked the numbers that were on the originals, the kit was comprehensive, and by the evidence running it since, seem to be of good quality.

Took just a few days to ship to Iowa, happy customer.

Good luck,

Shane

Don't want to highjack this topic but at what level did u set the needles?
I can't get my 350 running well and I've red the position of the needles is different with the aftermarket ones compared to the original Honda ones. They seem a little longer than the original ones.

Hey there,

I didn't have to adjust the float heights at all with the new parts.  Yes, the new float needles are marginally longer that the stock parts, but the pairing of the new needles with their seats seems to net out such that the float height change (if any) is a non-issue, at least in my case.

As for measurements, here's what I did...

When removing the float bowls, the carb bank was all upside down on the bench, supported by a block of wood to keep it all standing up, as is my habit.  At rest in this position, all of the floats were at the same height (except the one that was stuck open!), with the flat bottom side virtually parallel with the sealing surface for the bowl.

I just went with the same eyeball-level when re-assembling, figuring that if there was an issue, it was easy enough to remove the bank again and deal with it.

I learned long ago that when dealing with carburetors (and I've done more than my share), best not to intentionally create a potential issue where none currently exists.

Since the leak source was fairly obviously a stuck float (and lots of fine crap in the bowls), I didn't want to change the float heights until necessary, and the new parts fit well enough to make me happy.

All the best,

Shane
I mount and balance MC tires--while-you-wait service by appointment.  Send me a PM.

Offline Shane72

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Re: Carb O-ring sizes
« Reply #12 on: July 09, 2013, 11:21:38 AM »
As an update to this post, I wanted to add a bit more information for those who may have a similar experience...

I wound up re-installing the original pilot and main jets, and using the new o-rings from the new main jets.

The reason was that at idle, the bike would want to flood out with a too-rich idle.  Had to keep feathering the throttle to keep it happy.  This only happened when fully warmed up, and probably only was affected by the pilot jets.

Anyway, the old jets got a good cleaning before being pressed back in to service, and everything seems to be good now.

All the best,

Shane
I mount and balance MC tires--while-you-wait service by appointment.  Send me a PM.

Offline Dos

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Re: Carb O-ring sizes
« Reply #13 on: August 24, 2017, 07:01:24 PM »
I recently just bought, 4 rebuild kits for my carbs
http://4into1.com/keyster-carburetor-rebuild-kit-honda-cb400f-1975-1977/


the main jets did not fit properly with the clip that holds them in so I used my original main jets and took the orings off the aftermarkets and put them on however I feel they aren't holding well.. am I making this up? what would be a side effect of an oring not sealing correctly

I also used the aftermarket Needle Valve & Seats.. What would be the side effect of the orings on that not doing the job?

Right now I am just having alot of trouble starting her up and at idle it sounds bad. Alot of gas also leaks out of the overflow.