1978 CB750F - Metric Mayhem

Re: 1978 CB750F (METRIC MAYHEM)

I photoshopped up a few color comps of my bike with the paint striping and badge. The tank, rear fender, and side covers will be Ducati "Titanium."

White Version:
4462548925_b433678c22_b.jpg


Red Version:
4464966100_608280ebf6_b.jpg
 
Re: 1978 CB750F (METRIC MAYHEM)

Ok, the engine should be wrapped up sometime in the near future. Looking forward I am going to need some advice for re-jetting. Right now, I have a stock set of carbs for the '78 CB750F. I think it has 105 mains right now.

I will end up with an 836cc motor, with 4 into 1 Yoshimura replica exhaust, and K&N oval style pod filters for the carbs. What would be a good place to start with for some new jets?
 
Re: 1978 CB750F (METRIC MAYHEM)

I sent an email to dynoman.net to see what they recommended and this is what they said.

"We would recommend that you order 115, 120, and 125 jets to get you started. We would start with the 120 jets and see how it runs. Then go 1 size smaller and one size larger to see what works the best. All engines are a little different, but if you start rich and you will be safer, as a lean mixture can damage your engine."

Unless anyone would see a problem with this, I think I'll go this route. Not sure If I want to order from them, but they are 4.50ea there. Not bad...
 
Re: 1978 CB750F (METRIC MAYHEM)

white.


as for jetting, that works, but simply trying to see what runs better seems like too much work... read up on jetting and how it affects performance.
 
Re: 1978 CB750F (METRIC MAYHEM)

Rocan said:
white.


as for jetting, that works, but simply trying to see what runs better seems like too much work... read up on jetting and how it affects performance.
Click to expand...

I've done some reading, but it's mostly about 750's with upgraded exhaust and pod filters only. I cant find anything about proper jet sizing for a 750 bored out to an 836cc. That's why I asked here...
 
Re: 1978 CB750F (METRIC MAYHEM)

I just call from my Dad at the shop. The motor is finished now! He got the tap for the crankshaft I sent today, and the guy who bored out the cylinders came and dropped them off today as well. He was able to tap the hole in the crankshaft and the bolt a fellow SOHC4 member sold me fit perfect. Thanks ffjmoore... Waiting on the powdercoaters for the frame and some other pieces. Exhaust is getting heat wrapped. Rims are being repainted. This bike should be going together pretty quick now... I'm stoked.
 
Re: 1978 CB750F (METRIC MAYHEM)

Anyone else want to add their share on where to start the jet sizing for an 836cc?
 
Re: 1978 CB750F (METRIC MAYHEM)

I don't know if this will help but:

If you google jet bore diameters you should be able to find charts with each jet # and their corresponding bore size. Figure the percentage increase from 750cc to 836cc and increase the jet sizes that way. Oh, and those charts normally show the equivalents to each brand of jets (Mikuni, KeiHin, etc) to cross reference the sizes. Assuming you know different brands of jets don't mix between carbs?

That's the only semi-logical way I can think of to figure it out. Hope somebody has a better answer than mine!
 
Re: 1978 CB750F (METRIC MAYHEM)

Sent you a message on another forum. I have been told 128's is a good place to start for a 836 build.
 
Re: 1978 CB750F (METRIC MAYHEM)

Big Rich said:
I don't know if this will help but:

If you google jet bore diameters you should be able to find charts with each jet # and their corresponding bore size. Figure the percentage increase from 750cc to 836cc and increase the jet sizes that way. Oh, and those charts normally show the equivalents to each brand of jets (Mikuni, KeiHin, etc) to cross reference the sizes. Assuming you know different brands of jets don't mix between carbs?

That's the only semi-logical way I can think of to figure it out. Hope somebody has a better answer than mine!
Click to expand...

Cool, I'll look into that.
 
Re: 1978 CB750F (METRIC MAYHEM)

Yoshi exhaust being wrapped...

4810800965_c5183aef82.jpg
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And painted black. The whole thing will get several coats of clear gloss after the tape is rubbed down with some stripper to give it a vintage look and some more depth. Should be interesting.
 
Re: 1978 CB750F (METRIC MAYHEM)

tWistedWheelz said:
Good job on that wrap, nice and neat!
Click to expand...

Thanks, my buddy Aaron did the wrap job. Simple tip for header wrapping. Wet the wrap first, and you can work it easier. Be sure and give it plenty of time to dry out though. Especially if you want to paint it or whatever. Also, before painting you can use a blowtorch to get rid of all the fuzzies on it.
 
Re: 1978 CB750F (METRIC MAYHEM)

This cover will need some sanding and polishing before being re-painted because of some scuffs:
4810800739_43a685aa4a.jpg


Oil Pan with paint being removed:
4811424122_b9e347e5d4.jpg


More new paint:
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