Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: mattsz on January 18, 2019, 02:02:47 PM
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I'm beginning to think about my carbs.
The PO says everything was running fine when the bike was stored, but I know the bowls weren't drained and the fuel dried out. I opened one carb up, it doesn't look all that bad, but some attention is needed. Here's a post with a couple photos attached, nothing too surprising there:
http://www.sohc.co.uk/index.php/topic,17461.msg150591.html#msg150591 (http://www.sohc.co.uk/index.php/topic,17461.msg150591.html#msg150591)
And here's a couple more (click to zoom). The float valve seat's o-ring is typical of the rest of them in this carb, dried out and cracking apart. Obviously, all new o-rings needed:
[attach=1]
The float valve - showing signs of age, but I can't feel any texture or ridge at the seat with a fingernail, and the spring action is smooth. Ok to try out, or should I just go right with new?
[attach=2]
Float bowl screws: 15 all the same, one different... ::)
[attach=3]
The jets and brass bits all seems pretty clean, so I'm hoping I can reuse them. Of course, things could be different in any of the other carbs!
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Regarding the choke lever action: there's a slight amount of play in the linkages between each carb. With full choke, all the plates are closed, of course. As I rotate the lever to reduce the choke, the #1 plate rotates right away - but there's a slight lag before the #2 plate begins to move. Same with #3, and then #4, all "cascading" as I rotate the choke lever. As a result, when the choke lever reaches the limit of its travel, the #1 plate is noticeably "more open" than the #4 plate, with 2 and 3 in the middle somewhere. You can see that condition in this photo:
[attach=1]
Is this ok, or should I be looking at trying to adjust the linkages to equalize them?
My initial plan is to try to clean the carbs without separating them, and reassembling with new o-rings (definitely) and jet, float and seat parts (maybe) to see how it goes...
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Yeah, use the adjuster screws to equalise all 4 butterflies so they move together inline. Don't forget to tighten the locknuts afterwards. 😉
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Be careful with the threads on the float bowl screws, they strip for fun due to being so fine and old alloy. I got Graham to helicoil all 16 of mine when I refurbed my carbs.
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Be careful with the threads on the float bowl screws, they strip for fun due to being so fine and old alloy. I got Graham to helicoil all 16 of mine when I refurbed my carbs.
Thanks for the warning! But... assuming you're talking about removing them - how does one be careful with them? Apply penetrating oil and hope it soaks in before trying to remove the screws?
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You could try penetrating oil but experience has taught me that how ever careful you are removing the screws, its when you put them back in the problem occurs. You jut get that very 'loose' feeling on the end of the screwdriver but by then its too late. Remove the screw and the thread comes out with it :'(
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You could try penetrating oil but experience has taught me that how ever careful you are removing the screws, its when you put them back in the problem occurs. You jut get that very 'loose' feeling on the end of the screwdriver but by then its too late. Remove the screw and the thread comes out with it :'(
Ah, ok... I wondered if it was an initial "removal" problem, where the screws simply bring the threads with them...
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The removal of the screw is ok as you have the leaf spring pushing the bowl down, so there is little or no tension on the screw thread. When you re fit the bowls, you are having to push against the leaf spring, whilst trying to do the screws up. I always put 2 screws in at opposite corners of the bowl and just nip them up to take out some of the tension and then pop the other two screws in.
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I'd recommend that you try using the original needle valves. Just give the needles and the seats a bit of a polish and replace all of the o rings and then take some time to make sure that you get the float heights correct.
Whilst you're in there, it's also worth checking that the jet sizes are std to get an idea if someone has been in there before you in which case you might want to think about checking needle heights.
Also check that both jets and the emulsion tubes are clear - make sure you check the cross drillings in the idle jets and the emulsion tubes.
The choke flaps are simple to adjust to make sure that they're all fully open.
And as Julie mentioned, buy yourself a helicoil kit for the float bowl screws
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Thanks guys!
Is there a specific resource which would show me specifically, on these carbs, what parts are what and where they go... the jets and float valve and such I know about, but what about the different passages? I'm looking to dismantle the carbs enough to replace the rubber bits and clean everything as best I can, but without separating them, which means carb cleaning spray and compressed air. And probably some degreaser for the exteriors...
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Regarding the float bowl screws, sure use penetratong oil if they have been stood a while, but if you’ve already removed them once its too late for that. Make sure the screws are clean and if they look shot (threads or screw heads) replace them... Most importantly when you refit them just give them a gentle nip and avold overtightening. You could use a bit of copper grease on the threas to prevent any further damage but shouldn’t be necessary if you don’t overtightening. Good luck 😄
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I opened up the rest of the bowls today, no issues. All screws were only just barely more than "finger tight." I had a moment of panic when I removed one of the carb top covers, and felt the screw dragging and grinding a bit, but it turned out to be the split washer turning with the screw and scraping the top of the alloy cover.
All four bowl interiors looked about the same - dirty, but dry and powdery, not sticky or varnish-y. Two of the float pins were a bit bunged up, though, and gave me a bit of trouble - one had been gripped with pliers at some point, and had some tooth gouges, which I polished out enough to be able to reinsert it easily. The second had one end that was slightly bent, and so it didn't want to budge. But I freed it up and tried to straighten it out a bit, not sure if I really improved it, anyway it goes back in enough and I can remove it again. Either way, all four floats pivot with no restriction.
All four have a 75 main jet, and a 40 pilot (slow?) jet, per spec. Are there any other numbered items I should be on the lookout for? The Honda Service Manual quotes a spec of "Carburetor Setting mark: 054-A". I can't find any other reference to that.
It seems like most of the "tutorials" for carb disassembly include disconnecting them, which I was thinking of not doing initially. I'm having a hard time deciphering what steps are for separating the carbs, and what steps are just for dismantling interior parts for cleaning, especially for the upper parts (everything in the float bowl is obvious). Anyone have any suggestions for where I might go for clarification? Are there multiple grooves in the needle?
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If you don't split the carbs you can still remove the throttle slides with the needles attached to them. The needle has several grooves. If I remember correctly the standard position is 3rd groove down for the circlip. It's clearly shown in Clymer or Haynes manual.
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If you don't split the carbs you can still remove the throttle slides with the needles attached to them. The needle has several grooves. If I remember correctly the standard position is 3rd groove down for the circlip. It's clearly shown in Clymer or Haynes manual.
I have both. Interesting that the Honda service manual doesn't mention the needle grooves...
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Honda didnt want anyone messing with the mix !
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I've got a new o-ring set... it includes the rings for the pipes that connect the carbs together. I wasn't planning on getting in that deep, as I mentioned earlier - just dismantle as much as possible without separating the bodies, then clean. Do you guys think that's a false economy at this point? I was told the bike was running great two years ago, but I really don't know. If I'm going this far with the strip and clean, does it make sense to go the full monty? Or is it wise to fix what I know is bad, then try it out?
Is there a specific resource which would show me specifically, on these carbs, what parts are what and where they go... the jets and float valve and such I know about, but what about the different passages? I'm looking to dismantle the carbs enough to replace the rubber bits and clean everything as best I can, but without separating them, which means carb cleaning spray and compressed air. And probably some degreaser for the exteriors...
Any thought on this? Some tutorial or video? Or do I just clean everything?
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Personally I would not remove the back plate and split the carbs if I didn't think there was a problem that needed attention. I would pay more attention to the bits I can get to and make sure they are as clean as possible and fit new O rings etc. If you do need to remove carbs from the back plate and spit them, it is easy enough but it doesn't sound like it's necessary in your case.
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Thanks Julie! That's kind of where my head is at anyway, in case you hadn't sorted that out... but all the easy-access rings need replacing, so I was on the fence about digging further. I will definitely check the balance of the slides on the bench; the choke linkages are mis-adjusted and I imagine the slides could be, too...
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I have both. Interesting that the Honda service manual doesn't mention the needle grooves...
if you have the 'shop manual - honda cb350f-400f' (hwm002) by honda then its right at the back on page 95!
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Personally I would not remove the back plate and split the carbs if I didn't think there was a problem that needed attention. I would pay more attention to the bits I can get to and make sure they are as clean as possible and fit new O rings etc. If you do need to remove carbs from the back plate and spit them, it is easy enough but it doesn't sound like it's necessary in your case.
easy maybe for some of you 'old timers' (not you julie of course :))) but i was finding it difficult just getting the slides out - 'cos i'm not used to honda multis' - but i see there are complete repair kits jets and all on ebay for about £30ish or with the floats for about £45ish which, if mine is still running so very rich after syncing them i may/will have to carry out - 4th time taking them off, but without trying them first you can not tell if they will work ok or not..
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I have both. Interesting that the Honda service manual doesn't mention the needle grooves...
if you have the 'shop manual - honda cb350f-400f' (hwm002) by honda then its right at the back on page 95!
Yes, you're right, of course - I did notice that. I wasn't clear, what I meant was, that I thought it interesting that that manual doesn't mention the grooves at all in the work description...
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Keyster kits are not good for brass bits which rarely wear but usually have all the gaskets and O rings
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I think you'll always get black sooty plugs if you're just checking them after idling as they don't hot enough to burn it off.
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Also forgot to say 500's do run rich low down.
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Someone gave me a carb jet cleaning tool. Bikemaster says it's a necessity. Is this useful, or should I avoid it like the plague?
https://bikemaster.com/carburetor-jet-cleaning-tool.html (https://bikemaster.com/carburetor-jet-cleaning-tool.html)
(https://bikemaster.com/media/catalog/product/cache/1/image/604x779/9df78eab33525d08d6e5fb8d27136e95/1/5/152212jetcleantool.jpg)
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Someone gave me a carb jet cleaning tool. Bikemaster says it's a necessity. Is this useful, or should I avoid it like the plague?
https://bikemaster.com/carburetor-jet-cleaning-tool.html (https://bikemaster.com/carburetor-jet-cleaning-tool.html)
(https://bikemaster.com/media/catalog/product/cache/1/image/604x779/9df78eab33525d08d6e5fb8d27136e95/1/5/152212jetcleantool.jpg)
Don't use it on your jets they will open them up as they are files used for cleaning Oxy cutting nozzles.
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I have a set of those in Pink, purchased from Mr Silver many years ago. I use them on everything.....except carbs and never ever to clean out jets
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I have a set of those in Pink, purchased from Mr Silver many years ago. I use them on everything.....except carbs and never ever to clean out jets
Oh great,....now I find out! I don't think it's done any harm, but never again! :-\
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Originally used to clean out gas welding torch heads, not for carbs.
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Huh. So what, does Bikemaster sell new jets, too? Handy business model! :-X