750G1 carb woes.

I'm pretty sure my problem lies in the fuel air mixture.

I have replaced the jets in the float bowls, replaced the float needle valve, and the needle screw thingie at the front and set it 2.5 turns out. the bike still only starts for 2 seconds on starter fluid sprayed into the air box.

The next step, kinda shot gun method, I am replacing the tank (creamed) and fuel filters with clean ones from the G.

I can't think of anything else.

Q2:
If I replace the float valve, does the float level need to be adjusted? What would the symptoms be if I do?

Thanks in advance,
Erol

Yes when you replace the float needle valve you need to check/adjust the float level.

When you pull the carbs off, is there fuel in the float bowls?

Shade tree mechanic trick, when you are cranking it over trying to start it, stick your hand over one of the carbs to block the airflow. Then see if it fires or if your hand has fuel on it

I guess the bike in question is a twin since you mention 79... In any case, does the bike have the stock airbox on it when you try and start it? Mikuni BS series carbs can be fussy to start if you lean them (not using an airbox/filter) and they have the stock jetting. If you DO have the airbox/filter in place and you can't get the bike to run, then you need to check some things...

First, does this bike have a vacuum or gravity petcock? If it is a vacuum petcock, put it in PRI (prime). If gravity, put it in ON position. Take the hose off the carbs and see if gas comes out. If not, then crud inside the tank is obstructing the flow of gas. You will need to remove the petcock and clean its screen that is inside the tank. Use an inline gas filter...

If gas flows out the hose, then check the vent lines are not pinched or blocked or obstructed. See the "BS carb connections" page available for viewing from the main page of my web site ( www.wgcarbs.com ).

OK, if the vents are clear, get a clear and flexible plastic hose. Put it on the drain nipple of #1 carb as you sit next to the left side of the bike while the bike is on its centerstand. Open the drain screw a few turns while holding the hose STILL and against the side of the carb so the end comes up OVER the line where the bowl gasket is. The gas will fill the hose... tap out ANY air bubbles as these give very false readings on the gas level... Anyway, gas should come to about 1/8" below the gasket mating line of that carb. If it doesn't, you will need to remove your float bowl and carfully bend the tang (the bit of metal on the float that contacts the needle) up or down to adjust the level. Bending the tang UP puts less gas into the bowl and down puts more. Anyway, refill the bowl and recheck the level and repeat till you get the correct amount of gas in the bowl.

I would be pretty surprised if one of these things, done in the order I suggest, doesn't fix your problem.

George... I dont know what to say but thank you. thank you from the heart of my bottom!

It is a gravity petcock and it does flow, but I am still exchanging tanks with my clean one, and replacing the fuel filters. I did pull the petcock out of the creamed tank and it was clear.

wiredgeorge wrote:

If gas flows out the hose, then check the vent lines are not pinched or blocked or obstructed. See the "BS carb connections" page available for viewing from the main page of my web site ( www.wgcarbs.com ).

Ok,I went here www.wgcarbs.com/101348.html cuz I am curious what vent lines we are talking about. The page is empty.

I've not given up on demistifying this "magic box" in my bike.

Hello?

Thanks for the heads up. My hosting company tells me there was a "glitch" and that their developers can fix the problem and bring the page back online. They likely will be hiding this page till it gets fixed so have some patience... Hopefully, it will be fixed soon as I don't feel like cooking up a new page from scratch. thanks

So, regardless of the page not being up, what are the vents? are we talking about the little channel on the air box side of the carb, at the top that is to allow the diaphram to breath or are we talking about something different?

Maybe this will help.
I really meant to get your bike running before I left, but we didn't even have the time to get started on it

The web site page is back online.

wiredgeorge wrote:

The web site page is back online.

That page is still a dead link, in fact all i noticed that has changed is there is no longer a link to thatpageoff your website. If it aint there, i guess it isnt a problem.

::: throws cover over bike ::: See, no problem!

You might as well take off the carbs as it's obvious that's where the problem is.
When you replaced the float needle valves, did you check the passage from the fuel line barb to the float needle valve to make sure it's clear? I have seen that passage plugged solid on 750 twin carbs.

You could verify that's the problem by removing the hex plugs on the bottom of the float bowls, if no fuel comes out then there is no fuel in the float bowl.

I don't have a clue what drain nipple WiredGeorge is talking about, there is a nipple on the bottom of the carbs but that's the overflow line, it's connected to a standpipe inside the fuel bowl and it will not drain gas out of the fuel bowl unless your float needle valves are bad and flooding the carbs. That line will also act as a vent to the fuel bowl since there is no check valve in it.

Anyway, step one is to see if you have fuel in the float bowls.

Just checked and the vent tube is on the left rear of each carb close to where the airbox connects to the carb, it points up and to the rear.

So there are three lines going to each carb, the vent line, the overflow line, and the fuel line.

Post edited by: steell, at: 2006/07/24 17:28