Help needed carbs

[mark73]

Hi Ive recently boughtan cb 750. S plate. Theres k & n filters fitted, the seller said the carbs havent been set up to suit them.
My mate reckons they run shit with them on, and better off with the standard air box ??

i like the k&n,s. what needs doing ? would the carbs need rejetting ? or just setting up properly ?

any info much appreciated.

mark

[bobbed_750]

What year 750 do you have? If you are running the pod style filters most likely you while have to re-jet I have done a lot of reading and it is possible to just tune the carb with pod filters but you are gunna been in the extreme edge of your tuning limit if you understand what I'm saying

It also depends on the kind of exhaust it has on it I know with my 78 with pods and open drag pipes it was to much for the stock configuration and had to go to 110 main jets. all in all changing the jet isnt that hard to do and if its an old bike and the carbs havent been gone through it might be a good idea to get in there anyway and check float heights and what not anyway.

[mark73]

hi bobbed,

cheers for the info. shes on a s plate. so hang on trying to work it out. a v plate is 1980, so 1979. the carbs are standard. the k and n,s are the conical shape. round where they fit onto carbs, go inwards, slimmer to a smaller end. about 1.75 to 2 " long.

the pipes are open drags, no baffles at all ( yeah its fuckin loud ). the carbs have been cleaned out thouroughly, no crap left in them.

what size are the original jets ?

im new to the cb 750. love the look of the engine. its non standard, 15"apes, single seat, 4 into 4 open slash cut drags, back end cut and chopped, all black, teardrop shape tank, slightly stretched. electrics standard, switch gear off a kwak..couldnt get hold of cb switches for love nor money, either fucked or exspensive...shes no showwinner, a rat /bobber. bur my pride and joy...still needs few things finishing properly. chain guard needs painting, and rear end mud guard struts.

cheers

mark

[bobbed_750]

Yeh I know what filters your talking about. The standard main jets for these bikes are 105 I believe. Who cleaned your carbs? Carbs are very tricky things just when you think they are clean.....they aren't lol I've found that out over the years. Like I said going to 110 or 120 mains would deffinitely help you out in my opinion. and set the needle second clip from the top and go from there.

[mark73]

cheers bobbed. the bloke who cleaned my carbs, is a mechanic all rounder on bikes, does electrics, engines ect...been doin it for yrs, never had  aprob with him before...he did say the carbs were  a bit gunky...

I,ll try the larger jets, the 110s 1st...i know the jets on now are standard, size.

hope that works..if not try the 120,s. if still no good, get hold od an standard airbox and see what happens, with standard jets back in...

rather keep the k and n filters tho...

cheers.

will let you know how it goes...once ive got the money to get the bits i need...any idea how much the jets will cost ?

mark

[bobbed_750]

Well at least you have someone you can trust you have a couple diff options

http://www.crc2onlinecatalog.com/misc_carb_parts.htm#Main%20Jets

Just scroll down to KEHIN MAIN JETS SCREW IN TYPE

OR.....

http://www.z1enterprises.com/catalog.aspx?pid=HPCF2

as for cost they are literally pennies. make sure you call and get the right ones for your carbs and year of bike. cheers