Fuel starvation...or what?

This is what happens. Engine cold, starts great, pulls like a train, open it up on a straight and first one cylinder fails then another does - me thinks float levels are incorrect, but letting off doesnt cure the problem ( Id assume the chamber fills up pretty quickly). I have to park the bike and leave it 5 minutes, then it starts and does the whole thing over again - ive checked and it is spearking when it wont run - any suggestons?

 

Look for a kink in the supply line.
Possible Beenie-screen filters atop the Float Valves are clogged.

Possible vacuum leak or collapsing vacuum line to the Petcock.
Bad petcock?
Try running the Bike on PRIME and see what happens.

Report findings.

 

problem in understanding - this engine is fitted to my quad (dont all curse at once)....we dont have petcock in the UK...must have another name. Plus there are no vacuum lines going to anything - please try to help me understand this? thanks

 

You need to check for the constant flow of petrol from the fuel tap to the carbies inlet port.

 

everything flowing freely - allitems are megga clean...just dont understand it

 

Dirty screens in the carbs? Could be there isn't enough height between the fuel tank and the carbs to generate enough head pressure to flow enough fuel. Also, if there is a horizontal section of fuel line or an up and down, air could be trapped restricting the flow of fuel.

 

theres no air lock and with twin tanks there is loads of fuel pressure at the carbs...could it be float height?

 

I had a similar problem, I had a big piece of rust in the tee shaped tube between the first two carbs. Had to pull the #1 carb off the rack and clean it out with a drill bit. Pulled the float bowls and removed the floats blew carb cleaner and air out the needle and seat holes. worked fine after that. Actually that is my best set of carbs I own. Good luck

 

I once found an obstruction "Hidden" in the Petcock. I had to find it; first.

When the flow from the Petcock didn't look as strong aas it should; I thought the Tower Screen in the Petcock needed cleaning.

When I pulled the Petcock; the Tower Screen was M-I-A ... it had become dislodged and is still at large in the Fuel Tank.
Somehow, a chunk of something got in to the Petcock and lodged in the Outlet.

I found it by probing the Outlet itself with a piece of long, plastic Weed Whacker Line.

Whatever is causing your Fuel Starvation is something we have overlooked.
The thing I always overlook is a kink in the Fuel Line after I connect the Fuel Line to the Petcock and then lower the Tank back down to secure it.

To insure that the Fuel Line does not kink; I have taken to using Spiral Plastic Wrap that you'd use to dress several wires together.

Tightly wrapped around the Fuel Supply line it prevents the Fuel Line from kinking, especially if you have added an inline Fuel Filter to the Fuel Line between the Petcock and Carb Inlet Line.

 

Hi Fizzy,
here's some translations.
petcock = petrol tap.
MIA = missing in action, or in tank
weed wacker line = strimmer cord.
anything else, just give me a shout, us Brits have got to stick together.

 

Strimmer???

What's a strimmer?

 

a machine that spins a piece of nylon cord around at high speed, for cutting long grass and weeds.

 

Weed Eater

 

Mine starts great, runs about 2 miles, craps out and runs again after sitting a bit....thought it was bad battery ( my stator is out I think), but it appears to be fuel flow.... the bike has been sitting, had a bunch of crap come out of the bleeder holes on the bottom of the carb bowls....Rick, you were talking about some screens that clog?

 

Original Equipment Float Valve Bodies come with "Beenie's"

They are small, plastic domes with a fine mesh screen which clip to the Float Bowl Body on the inside where the Fuel Fill Passage is.

They are really fine mesh and can foul with rust very easily.
Absent an inline filter to screen-out foreign matter ... it is screened from the Float Pin by this screen atop the inside of the Float Valve Body.

 

So....can i take them apart and clean them out without damaging anything?
Dennis

 

Yes.

Just be extremely careful NOT to break-off a Float Hinge Pillar.
That's a disaster waiting to happen.

The screens pop off the ends of the Float Body.
I normally leave then ON and spray through the Float Body and screen to clear them.

 

what do I use to clean the screens?

 

I use a toothbrush and spray carb cleaner.
Shoot the cleaner through the Float Body hole and blow off the screen.
Use the toothbrush to lightly brush-off any matter.

 

Can this cleaning be done with out re-syncing the carbs?

I am new to owning a bike. I bought my first XJ in January of this year. 1983 750 Midnight maxim. Had 9700 miles on it. Looked to be in good shape. The guy I bought it from Cleaned and re-built the carbs and re-synced them before he put it up for sale. I got it for a grand. I have put over 500 Miles on it and just last night it started to seem like it was missfiring and would barely run. Thought I blew the rings or valves. But no oil buring and spark plugs looked great. I was going to check the compression. But maybe there is something with the carbs. It would not stay running unless I used the choke. Any help would be appreciated.

Thanks,
Michael

 

Mikey:

You need to start your own Thread.

Plus:
Enter your Location in the appropriate box.

Use the "Signature" feature to provide Thumbs on your bike.
Like this:

_____________________________________________________
83 Mid-Max 12,000 miles Stock Carb Problems.

When we open your thread ... we need as much info as we can possibly have for your situation.

Use the "New Topic" and start a new thread.

More than one word, too ...
Midnight Max with possible Carb Problems (OK?)