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Jetting for 81 CB750C

John Luke

CB750 Enthusiast
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I have a custom 81 CB750C. It has 4into1 delkevic exhaust and I’m gonna put K&N pods in the carbs. The valves are in spec and carbs are synced. Fuel/air mixture screw is out 2-1/2 turns and stock jet is #102. Does anyone else have the same set up and what size jet would y’all use to get it running properly?

Thanks!
 
Like it has done with almost every other DOHC Honda since they were built the CV carbs and pods combo will kill you if the engine does not have full 100% compression. Valves in spec help that but any leaking has not been touched by doing that other than one open is now not open. If it started to burn to leak that is NOT cured. The CVs will not open the slides for spit if the engine does not have really good vacuum draw and pods kill that quite a bit. Why you see so many thousands of complaints by those that did what you are about to. The engines commonly go rich with no jetting changes at all and then anything jetted up makes it even worse. So, there is no way to even gauge until you get it running.

I can say that CV carbs self adjust to supposedly cover that but it never stops those who think you need to jet up, and showing a gross misunderstanding of how they work. The slides only work on demand from the engine, nothing your right hand does has full control of that like a direct lift carb so you don't even know where the added fuel should be placed. Most jet up and then bike goes into the super rich blind staggers when you gas it up. Most never do get them running tight either, the engine being off will not run right with pods often with anything you can do.

I've had them run fine with 75-115 jetting while running a good scavenging header that worked well. If you run around at 125 mph you won't be doing that any more either, the slides with pods will NOT open 100% like before and it shows on top end 5th gear. All other modes the engine should run fine.

Dynojet brand kits are often claimed to work there but they don't. The guy who owned the business worked long and hard with an owner that frequented the DOHC website, they even used custom needles and all other sorts of one-off parts and never did get the bike running 100% perfect using their pods. The head of Dynojet then gave up. But the kit still sells a lot and confused owners swear they work, commonly because they have never had a really good running DOHC under them. Understand one thing.............after you add the pods you will be doing all work after that just to get back to where you were with the stock OEM airbox, yes it sucks to have to work with but there is no other setup that makes the engines wake up and go as well.
 
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