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Starting it up, keeping it running

rs_ss350

CB750 Enthusiast
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Just bought this bike so still working out the proper quirks in starting her up. 79 cb750k w/13k miles, needs choke on start, starts off at good RPMs but within 5-10 seconds it dies. Try to start it again, it sputters, then I gotta rev it and keep the revs up until it warms up enough and I can diengage the choke and let her idle. This is not ideal. My 2000 Shadow needs the choke to start also, but runs real strong when doing so, only a few minutes needed to get warm enough to pusht the choke back in... where whould i start with the CB?

Thanks!
 
Lean due to emissions regulations of the times. Remove the idle limiter caps off the screws with say a soldering iron (loctited), and realize the stem right below cap is super thin so it breaks off easy to make a problem. I either grind tab off the limiter and leave cap on or grind the tab off fuel bowl, all done with carb bank off bike. Then you can set the idle screws like 2 1/2 turns out to make it richer and helps cold idle. The carb linkage also has fast idle linking to choke but it must be adjusted right.
 
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Hi rs ss350
I know this is an older thread, but I am having exactly the same issue with my '81.
Did you try the carb mod - if so did it work out?
Thanks :)
 
Hi Oliver Boy,
I actually did not attempt this. I had yet to get through a checklist of items from another site (http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&p=68364). Once I swapped the plugs, adjusted the valve clearance, and synced the carbs, i got a much stronger start. On start it idles pretty high around 2k, then starts to slow down on it:s own and die unless i do something. Through experimentation i:ve found that as the tach starts to go down, i slowly push the choke back in, little by little to keep the engine running at a healthy speed until it:s time for me to take off. Not perfect, but manageable for now, until I remove the carbs and replace them with the set I am currently rebuilding - i:ll test them out on this bike before I put them on the other bike I:m building, just to make sure they work as they should.

Sorry if this isn:t at all helpful :)
 
Thanks, this is extremely helpful!
My '81 is going to have to serve as a winter commuter this year- I need to get it starting with much less fuss then it requires at the moment and Vancouver rain is not going to help the situation :)
You mentioned a second bike- What are you building?
(I have 3/4 0f an '82 custom that I got for nearly free and I intend to complete a functional rebuild on it)
Thanks again for your reply.
:thumbsup:
 
Thanks, this is extremely helpful!
(I have 3/4 0f an '82 custom that I got for nearly free and I intend to complete a functional rebuild on it)

Funny, that:s exactly the situation I:m in. Just bought this 82 custom on the weekend for a few bucks... most of the pieces are there, just need to get enough of it back together and running before spending too much on a full custom build.

cb750c-1.jpg
cb750c-2.jpg
 
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