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PLEASE HELP!!! 1981 - Honda cb750c - Bobber- Jetting Issues: PODS and STRAIGHT PIPES

brett_damn_combs

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Hello,

1981 Honda cb750c
-bobbed
-air pods (air box removed)
-straight open pipes

Issue: runs lean, pops, flames, won't run when giving it any gas

Please help me with this! I got this bike last year from a guy that built it into a bobber for me... Has 5,000 original miles.
-I've taken to 3 different mechanics
-I've read FORUM after FORUM about this issue, and some have gotten it to work

JETS I'VE TRIED:
-OEM
-120, 125, 130, 135, 145, 150 (Primary)

Current Mechanic is a Vintage Bike Shop. Current mechanic has 30 year working on Honda.
-But they are telling me that with the OPEN STRAIGHT PIPES they cannot get the JETTING correct

QUESTIONS:
-Are there baffles I can insert into the OPEN STRAIGHT PIPES to provide some back pressure? My mechanic said "no" and is trying to get me to go to a 4 to 1 exhaust system

-Also, the mechanic is ONLY changing the PRIMARY JET out and not messing with secondary... Could this be an issue? They ARE manipulating the needle..

-They want to go up to a 160 / 170 Primary Jet... Does this sound right?

-I've read that people have taped the ends of the POD FILTERS to restrict the air flow... and this helps with the vacuum and reduction of air getting through the bike... Thoughts?

-Also, for straight open pipes - there aren't any universal baffles I can insert into them to help with noise and regulating the exhaust?

-DOES ANYONE HAVE ANY SUGGESTIONS OF GOOD MECHANICS NEAR THE MID-ATLANTIC REGION (RICHMOND VA)? I HAVEN'T BEEN ON A BIKE IN OVER A YEAR AND I'VE LOST MY JOB, MY GIRLFRIEND OF 14 YEARS KICKED ME OUT OF OUR HOUSE AND THE ONLY PLEASURE I GET IS FROM RIDING AND I CAN'T DO THAT... PLEASE PLEASE HELP!!! THANK YOU SO MUCH FOR ANY INSIGHT!!!

BELOW IS A PICTURE OF THE BIKE:
(Sorry these aren't the best pictures of the areas I'm talking about - but hopefully you will get an idea of what I'm dealing with... I just don't know what to do)

hondacb750.jpg.....JPG...MY BOBBER.JPG1554344_10101586142030706_478663491_n.jpghondacb750.jpg.....JPG...MY BOBBER.JPG1554344_10101586142030706_478663491_n.jpg
 
Lengthen your pipes or better yet go to a 4-2 set up, will mellow sound a little, you dont need back pessure to run proper. Ditch the cv carbs if you are not going to use the stock air box and filter. The cv carbs wont work with pods. Search this forum, there are a couple guys on here that have put newer model carbs on their DOHC bikes that work.
 
I would love to know what carbs guys are putting on in place of the CV carbs. Im about to trash mine and build a manifold and just run 2 round or flatside carbs. These CV's are junk!

as for the baffles, yes you can get some, I put some in mine and it helped BIG TIME! I dont remember off hand what size mine are but this is where I got mine. I just slipped them into the end of the pipe and that was it.

http://www.tcbroschoppers.com/metric-parts/exhaust.html

Hope that helps and if you find anything about different carbs, let me know as well.
 
Best carbs would be Mikuni RS carbs. Cycle X also made a two carb kit for the sohc and the dohc motors
 
They came on the 78 and older models if im not mistaken correct? Wonder if I can just bolt them on in place of the CV's. Im about to smash mine with a hammer. lol
 
Mikuni RS carbs are aftermarket carbs. Any of the sohc carbs would be on the small side for the dohc motor as far as flow and trying to get a rubber boot that would fit.
 
An alternative carb set would be from an 83 cb1100F they seem to work with pods, good luck finding any tho, and you will need to run a cb 900F cam . Also some are useing carbs from the early cbr's but you need to do some fabrication for the intake boots.
 
Really like your bike, I would like to get a pix of the rear of the bike to see how he handled the rear suspension, is it a hardtail? I am ready to bob my 750 and the way yours was done is just fine, please reply
 
Lengthen your pipes or better yet go to a 4-2 set up, will mellow sound a little, you dont need back pessure to run proper. Ditch the cv carbs if you are not going to use the stock air box and filter. The cv carbs wont work with pods. Search this forum, there are a couple guys on here that have put newer model carbs on their DOHC bikes that work.

the cv carbs can run with pods. i did it on my 1980 cb750f i changed the jetting to 120 main and 75 secondary air mixture screws are set to 2.25 out. im running a 4 into 1 kerker. i also have seen others running them. guess their not for the timid.
 
Hello,

1981 Honda cb750c
-bobbed
-air pods (air box removed)
-straight open pipes

Issue: runs lean, pops, flames, won't run when giving it any gas

Please help me with this! I got this bike last year from a guy that built it into a bobber for me... Has 5,000 original miles.
-I've taken to 3 different mechanics
-I've read FORUM after FORUM about this issue, and some have gotten it to work

JETS I'VE TRIED:
-OEM
-120, 125, 130, 135, 145, 150 (Primary)

Current Mechanic is a Vintage Bike Shop. Current mechanic has 30 year working on Honda.
-But they are telling me that with the OPEN STRAIGHT PIPES they cannot get the JETTING correct

QUESTIONS:
-Are there baffles I can insert into the OPEN STRAIGHT PIPES to provide some back pressure? My mechanic said "no" and is trying to get me to go to a 4 to 1 exhaust system

-Also, the mechanic is ONLY changing the PRIMARY JET out and not messing with secondary... Could this be an issue? They ARE manipulating the needle..

-They want to go up to a 160 / 170 Primary Jet... Does this sound right?

-I've read that people have taped the ends of the POD FILTERS to restrict the air flow... and this helps with the vacuum and reduction of air getting through the bike... Thoughts?

-Also, for straight open pipes - there aren't any universal baffles I can insert into them to help with noise and regulating the exhaust?

-DOES ANYONE HAVE ANY SUGGESTIONS OF GOOD MECHANICS NEAR THE MID-ATLANTIC REGION (RICHMOND VA)? I HAVEN'T BEEN ON A BIKE IN OVER A YEAR AND I'VE LOST MY JOB, MY GIRLFRIEND OF 14 YEARS KICKED ME OUT OF OUR HOUSE AND THE ONLY PLEASURE I GET IS FROM RIDING AND I CAN'T DO THAT... PLEASE PLEASE HELP!!! THANK YOU SO MUCH FOR ANY INSIGHT!!!

BELOW IS A PICTURE OF THE BIKE:
(Sorry these aren't the best pictures of the areas I'm talking about - but hopefully you will get an idea of what I'm dealing with... I just don't know what to do)

View attachment 3957View attachment 3956View attachment 3955View attachment 3954View attachment 3957View attachment 3956View attachment 3955View attachment 3954

awesome looking bike!!
 
Have you tried chetty__moo's carb guidance? He's preaching it pretty hard. Might as well give it a try, right? Oh, and let us know how it turns out..
 
Not preaching. Lol just stating what worked for me. My step dad owned several bike shops. I introduced him to my mom when I worked at a shop he was working at back in 84. Cycles of Longwood in orlando fl. I would work summers at his shops over the next 20 years tearing down carbs and other bike dutys for him. He is the guru around these parts on carbs and anything motorcycle and he told me the combo. Good luck friends :)
 
Cycle X also made a two carb kit for the sohc and the dohc motors

Im done screwing with these CV carbs on mine. Although I got it to run decent, I was not happy what so ever with them. I might try this air box (DOHC CB750, CV carbs - http://www.steeldragonperformance.com/air_boxes_7.html ) and see how that goes otherwise I am just going to go for the 2 carb set up from Cycle X. I have been talking to them about it and they say they are amazing on the DOHC motors. Motorcycle season is about 2 months away here so going to need to do something quick. lol
 
Hello,

1981 Honda cb750c
-bobbed
-air pods (air box removed)
-straight open pipes

Issue: runs lean, pops, flames, won't run when giving it any gas

Please help me with this! I got this bike last year from a guy that built it into a bobber for me... Has 5,000 original miles.
-I've taken to 3 different mechanics
-I've read FORUM after FORUM about this issue, and some have gotten it to work

JETS I'VE TRIED:
-OEM
-120, 125, 130, 135, 145, 150 (Primary)

Current Mechanic is a Vintage Bike Shop. Current mechanic has 30 year working on Honda.
-But they are telling me that with the OPEN STRAIGHT PIPES they cannot get the JETTING correct

QUESTIONS:
-Are there baffles I can insert into the OPEN STRAIGHT PIPES to provide some back pressure? My mechanic said "no" and is trying to get me to go to a 4 to 1 exhaust system

-Also, the mechanic is ONLY changing the PRIMARY JET out and not messing with secondary... Could this be an issue? They ARE manipulating the needle..

-They want to go up to a 160 / 170 Primary Jet... Does this sound right?

-I've read that people have taped the ends of the POD FILTERS to restrict the air flow... and this helps with the vacuum and reduction of air getting through the bike... Thoughts?

-Also, for straight open pipes - there aren't any universal baffles I can insert into them to help with noise and regulating the exhaust?

-DOES ANYONE HAVE ANY SUGGESTIONS OF GOOD MECHANICS NEAR THE MID-ATLANTIC REGION (RICHMOND VA)? I HAVEN'T BEEN ON A BIKE IN OVER A YEAR AND I'VE LOST MY JOB, MY GIRLFRIEND OF 14 YEARS KICKED ME OUT OF OUR HOUSE AND THE ONLY PLEASURE I GET IS FROM RIDING AND I CAN'T DO THAT... PLEASE PLEASE HELP!!! THANK YOU SO MUCH FOR ANY INSIGHT!!!

BELOW IS A PICTURE OF THE BIKE:
(Sorry these aren't the best pictures of the areas I'm talking about - but hopefully you will get an idea of what I'm dealing with... I just don't know what to do)

View attachment 3957View attachment 3956View attachment 3955View attachment 3954View attachment 3957View attachment 3956View attachment 3955View attachment 3954
 
Unfortunately pods look good but perform like s***... They just don't create enough vacuum... I have rebuilt hundreds of those carburetors and there's a reason our friends from the rising sun to put a air box on them... Not only your mechanic should worry about Jets, needle length needle diameter is a major issue.. and replace Jets with genuine kehein jets... The aftermarket stuff is junk.
 
Pod filters and straight pipes on a DOHC is not only possible but will give good gains with a little fiddling. First off throw whatever ebay pod filters you bought in the trash and get a set of uni foams. These are the only good pod filters available for these bikes. There's a lip on the cheapies that blocks the vaccum port to the slide which is where 99 percent of everyone's issues come from. Once you have the uni filters a good starting point is an 80 primary jet (from the stock 68) and a 120 secondary jet(from the stock 102). The pilot jet doesn't need any immediate attention but it won't hurt to jump from a 35 to a 38( this is the jet underneath the little black rubber plug and is only a thread in on 81-83 carbs. 79-80 these jets are pressed in and not easily changeable). Also make sure the rubber plug is not cracked and seals good or else that will create a whole other list of problems. The final trick is to place a .005 inch shim underneath your needles. This isn't 100 percent necessary but helps to get the slides more responsive. Do those basic steps and you will have a bike that runs pretty good right off the bat. This is all assuming you have good compression and no leak through on your valves. Remember engines are air pumps and they don't create the required vaccum to operate these carbs if they aren't in good condition. Hope this helps some guys that want to run pods and are tired of all the nay sayers telling them it's impossible because it definitely is totally possible once you learn how these carbs actually operate. These carbs give and take with each jet change it will affect the other. It's a balancing act but once you get it figured out it will outrun any bike with factory air boxes.
 
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