problem with carbs and diaphrams

[madmaze]

Hello everyone,
ive been messing around with my carbs on my 83 gs450 this weekend since my bike doesnt run.
Ive narrowed it down to the diaphrams not moving up enough to let the fuel by the needle, ive cleaned everything i can think of and i just cannot get it to run..

Now if I take a screwdriver and jack up the diaphram a little it will come on but die as soon as the screw driver fall out from the vibrations.. lol

anyone have a clue what i could try/do/clean to fix this?
Ive spent way too much time on this and ive come up with nothing..

thanks


*btw yes that air jet is clean.. atleast on the inside.

[rustybronco]

Please tell me you tried running it with the air filter and air box installed.

[madmaze]

yes I did, but im using k&n filters. Does that make alot of a difference?

[TheCafeKid]

YES! The bike will have to be completely rejetted for Pod KN filters. They let WAY more air in, and as such the bike will be insanely lean without a rejet. Also, your slides LIFT by vaccum. They are not mechanical. So they're not going to lift untill you have the bike moving to the point the engine causes enough vaccum to lift them..

[madmaze]

Hmm so that means I need larger main jets? or also air jets?
Is there anyway to calculate/guesstamate the new jet size?

[Billy Ricks]

The most important part of a jet kit is the needles. You can go up on the mains, raise the needles, and adjust the pilot screws but there is nothing you can do about the taper of the needles.

[madmaze]

so I have 120 main jets in there right now.. what would make sense as a reasonable next higher step?
Can i just up the main jet size and not do the needles or is it recommended to do both?
also you mentioned "jet kits"? where can i find decent ones of those?

Thanks for the info

[Steve]

You have 120s in there now? What is stock?

Not sure about the two-cylinder bikes, but for the fours, you might bump the mains about two or three sizes for a pipe and three to five sizes for pods. If doing both, figure on about seven or eight sizes up.

Somebody more familiar with the twins can give better suggestions, I'm sure.

.

[madmaze]

stock is 115..

two or three sizes for a pipe

hmm what do you mean with pipe?
I currently have 1 "pod" per carb with a 3" pipe extension to make it fit past some frame pieces.
so maybe I should go up to 185 or 195's then..

[Steve]

By "pipe" I mean a custom exhaust pipe, usually called a "header".

Most of them are freer-flowing than stock, requiring larger jets in the carburetors.

With your 120s, you are already two sizes larger than stock.

Where did you come up with that "185 or 195"?
Stock is 115? two to three sizes for a pipe or three to five sizes for pods would mean 135, at most, that's eight sizes larger.

.

[madmaze]

not sure what you ment with sizes LOL
I just figured 10 is an even number

so since, for now, i have stock pipes i might want to go up to a 125 or 127.5?

[madmaze]

hmm ill give 125's a try.. well see what happens

[Billy Ricks]

Jets come in 2.5 increments, that's why he said 8 sizes.

[madmaze]

yea i figured that out after i looked for some..
I found this:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&_trkparms=algo%3DLVI%26its%3DI%26otn%3D2&item=180342067087&category=35597&viewitem=

[rustybronco]

http://www.z1enterprises.com/detail.aspx?ID=61