Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Murf on December 06, 2024, 01:59:11 PM
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Hi can anyone tell me which way up the secondary main jet should go.
It has 2 groves one for the o ring the other for the clip, the groves are positioned at different distances in from the ends giving a wide land at one end and a narrower one at the other. The old o rings are in the grove that will place the narrower land in the carb body next to the emulsion tube and the wide land in the float bowl, is this correct?
The internal jet bore is machined differently at each end so it is critical.
I ask as I don’t trust anything I find on this bike, and I feel they should be the other way up.
Thanks for any help.
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I am confused by your description, do you mean the main jet that fits after the Emuslion tube where the wide bowl clip is fitted?
I found this useful even thought its for a 400, if you zoom in on the photos at the relevant ( rebuild near the end) page you will see the counter sinking on the inside of the jet. Very important to lube the O ring I used a smear of red rubber grease on the outside. Any excess can easily be wiped off then it's fuly home.
https://www.vintagebikebuilder.com/cb350-400f-carb-rebuild-demonstration.html
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when the jet, or guide, which is what I think you are referring to is in the right way up, any writing on the end of it is facing you.
Edit..... Or do you mean the main jet?
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Thanks
I think I have my answer from Teds rebuild link, it looks like the end with the longest land goes towards the float bowl, the larger diameter internal drilling is also that end with the small drilling (the actual jet orifice) towards the emulsion tube. The article in Teds link is an excellent article.
Thanks Julie but there was no markings on the end of my jets just on the side.
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I'm not 100% certain but if you have no O ring in place and try to fit it upside down I don't think it pushes the emulsion tube fully home.
I have a memory of having the same doubts as you before it became sort of obvious once I'd read the link.
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It does push the emulsion tube in ok either way around, I got concerned because of all the cock ups that have been made by POs, odd secondary main jets 2 x 100 and 2 x 115, also incorrect o rings on them so they were just lose fit in the tube. I was told when I bought the bike that the carbs had been balanced by a very well respected local bike restorer!!!
Anyway carbs rebuilt now and looking good, I just need to do static balancing and get the 2 100 size jets I need. Oh and find the big horrible return spring which seems to have lost itself, I am sure it was in a tub on the bench last week 🙄.
Thanks for all the advice I have had.
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My only advice when doing the bench synch is go for a small slider gap. That way I think reduces the chances of dreaded hanging idle when hot.
Yes, I know it's never that simple.
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They seem to recommend about an 1/8 inch on the stuff I have read and looked at, would you go a bit smaller. I will balance them on the bike with the gauges when and if I get to bike and engine rebuilt point. That’s something time next spring with luck.
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I actually went for a zero gap on my 500 (just at the point where the slider would start to lift), I used something like a 1.5mm drill bit on my 400.
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Smallest undamaged drill shank you can get1/8 is a bit big 1 to 1.5mm is about best
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I guess it depends on which side of the slides you are adjusting the setting? I prefer to do it downstream of the slide using the smallest diameter drill I have (1/16 eg 1.5mm) ensuring the main tickover screw is not touching the lever arm.
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http://www.sohc.co.uk/index.php/topic,25713.msg235653.html#msg235653 Some use 4 steel balls from a bearing.
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Thanks, interesting stuff and very helpful, which side of the slide did you do the sync on, I would have gone for the choke side but now you have me wondering. Great info and no don’t will save a lot of time messing around trying to get it set up when I do get the engine up and running.
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I found the engine side easier as it's a straight enough gap
The advantage as I see it is a smaller gap means you can easily reduce the air flow & thus fuel flow at idle.
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Definately flat(engine) side to get a consistent measurement
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That's how I did it. Just take care you don't damage the slides edge. I'm still thinking of a perfect bench sync. Think popsickle sticks that are 100% identical. The basic idea is leverage. Situate all four sticks under the slides front thus, that on closing the slides a tiny bit further, you cause the ends of the sticks to raise. Check the far ends of the sticks have reached the same height/angle and adjust if needed. I haven't tried it myself, but anyone is invited.
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If you go for zero gap like I have on my 500 it was quite easy to see the slider twitch as it began to rise.
The down side for me was the main adjuster/stop screw on the bracket ran out of thread on the adjuster totally compressing the spring on the screw. I ended up building up the alloy stop to compensate so the idle adjuster worked normally.
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Thanks, will go for engine side.
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That's how I did it. Just take care you don't damage the slides edge. I'm still thinking of a perfect bench sync. Think popsickle sticks that are 100% identical. The basic idea is leverage. Situate all four sticks under the slides front thus, that on closing the slides a tiny bit further, you cause the ends of the sticks to raise. Check the far ends of the sticks have reached the same height/angle and adjust if needed. I haven't tried it myself, but anyone is invited.
WD40 straw works fine with me and no damage to the slides ;)