'79 with '75 CB750 carbs and pod filters... jet size?

If it's broken or just needs tweaked

Moderators: Volker_P, tidd650

seebeesixfifty
Posts: 9
Joined: Mon Jan 21, 2013 7:02 pm

'79 with '75 CB750 carbs and pod filters... jet size?

Postby seebeesixfifty » Tue Jan 22, 2013 12:12 pm

Newbie to bikes/engines here, please forgive me if this is a preemptive question. Picked up a pretty good condition 1979 standard, and I haven't had time to crack it open yet (cold Boston winter), but I want to get a better idea of what to expect when I do check the valves/carbs.

Here's the situation: the kid who had the bike before me put the 750 carbs in with 1974-1977 jets, he didn't know which year. He also installed stainless steel pod filters. Now because of all the extra air moving into the engine, he was having problems getting a smooth turnover. So he wrapped the pod filter in a t-shirt and ducttaped it. It runs now, but with the stock mufflers, he's getting a lot of condensation (not letting enough air out?) and it's rotted the bottom of the cans. There's also a pretty good amount of gunk on the front side of the engine, looks like oil might be coming from somewhere, but it's all over, not just in one spot. I think it's running super rich but it's hard to say because starting/running it in 25* weather doesn't give me the best idea.

So my plan right now is to clean the entire bike, tighten the casings (might get rid of mystery oil), remove the hack t-shirt job, keep the pod filters open and try to re-jet the carbs to get it all balanced out. Does this make sense? Just want the bike running clean, which I know it is not...

EDIT: i am at sea level

pic for your troubles:Image

my79650
Posts: 643
Joined: Tue Apr 06, 2010 11:37 am
Location: Gagetown, New Brunswick Canada

Re: '79 with '75 CB750 carbs and pod filters... jet size?

Postby my79650 » Tue Jan 22, 2013 7:19 pm

Nice machine; mini signal lites....i have a set of those 750 carbs as well sitting in my shed. They came with a pd50 stock carb setup....oil leak is probably the head o ring at the oil channel; these are known for leaking; other than that i like your bike.

User avatar
Volker_P
Posts: 5508
Joined: Mon Mar 06, 2006 1:53 am
Location: southern Germany

Re: '79 with '75 CB750 carbs and pod filters... jet size?

Postby Volker_P » Wed Jan 23, 2013 3:26 am

Welcome here! :D

Nice 1979, really looks good. Looks like the second, upper frame bolt in front of the engine is missing. This part of the frame is bolted and may be removed for removal of the engine. So better to have all bolts there!

Good idea to get rid of the undefined T-shirt solution. For the PD carbs, pod filters require a considerable rejetting (mains from ~90 to ~120). This is probably similar for the CB750 carbs. You may find more datails in the cb650 carb jetting question thread.

In the Rebuilt carbs source thread you may find some possibly interesting info on CB750carbs on a CB650, too.

Member pinhead would probably know something, too. Seems he was not here for a while, you may try a PM.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum


Return to “Technical Discussion”

Who is online

Users browsing this forum: No registered users and 24 guests