Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Liam on April 25, 2018, 07:33:43 PM
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Hi,
Nearing the end of my build...yay!!! Just a couple of things to finish off. Posted previously regarding dyno testing to get the fuelling right... general advice is no which I'm more than happy about so I'm dealing with the resetting the carbs... as ver a trial and error job. Grebbo recommend a relatively local chap that can fine tune the feeling but I'd like to get it there or there abouts...
My problem seems to be the slow jets. when opening up the throttle the revs can dip to the point of stalling. The original size 40 jets are 28mm long, the only jets available these days seem to be 32mm in length so it's deeper into the fuel bowl. The length is in the main body so if required I cut the bodies down to the original 28mm. Ive increased to number 48's but no difference and the air jet does seem to have any impact at all. I'm hoping I just need to up the size. carbs have been refurbed, ultrasonically cleaned etc. etc.
My question is... How will having a longer pilot jet "body" impact on the fuelling??? is it an issue.
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oh... and the bikes got ramair pods that replace cheap Chinese pods which were on the bike as well as a 4 into 1 straight through exhaust also inherited...
Cheers
Liam
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What bike is it
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Hi Pete,
Apologies... Its a CB750F Supersport 1976 US import.
it came with 135's main jets
Ive upped the pilot jets to 48's
Cheers
Liam
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Are you sure this is a jet issue, coils often cause these issues I chased a problem with one of my bikes for a year believing it to be a feeling problem only for problem to disappear with a different set of could and cleaning all earthing points
Also float height set properly helps
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Probably the pods, they don't sit well with these bikes. Can you go back to standard air box? It is possible to get them to run right on pods but it's a lot of trial and error.
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Cheers gents.
I think it's going to be trial and error, I don't have the original air box... so I'll try the 58 and 68 pilot jets and try and set tick-over...
I set the floats when I cleaned and refurbed the carbs...
Watch this space
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There's a few airboxes about. Here's both halves you require.
http://www.cb-four.com/cgi-bin/shop/__TOP-CASE-AIR-CLEANER-Honda-CB750Four-F1__13-0090-09_07.06.html (http://www.cb-four.com/cgi-bin/shop/__TOP-CASE-AIR-CLEANER-Honda-CB750Four-F1__13-0090-09_07.06.html)
http://www.cb-four.com/cgi-bin/shop/__Bottom-airbox-Honda-CB750Four-F1-F2-K7__12-B01-1010-09_07.06.html (http://www.cb-four.com/cgi-bin/shop/__Bottom-airbox-Honda-CB750Four-F1-F2-K7__12-B01-1010-09_07.06.html)
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Cheers... Appreciate the link