Topic: CB750K1 carb problem - SOLVED -

[TwoTired]

Glad you solved a mystery.  But here is another.

Why does your bike have a problem with the overflow/vent tubes but millions of others don't?

 

[andy750]

Well done Johnie! Very informative thread!

Andy

[Spanner 1]

Wow, some kind of harmonic @ 50 mph airflow!!..... like blowing across a soda straw.... I wonder what 'tune 'those 4 hoses were playing in the wind ?.... I hope it wasn't any Neil Diamond number !!

[Simpson]

Glad you solved a mystery.  But here is another.

Why does your bike have a problem with the overflow/vent tubes but millions of others don't?

 

Where the heck are these things suppose to go? There is no bracket on my K0 or place to nest them....

Congrats Johnie!

[shorterdanny]

congrats buddy,

hopefully mione is something just as easy to solve, was relieved to see the thread title changed to solved....

have ordered new floats and going to try different positions today..

as to why this doesn't affect every bike, prob down to a fluke combo of the variables, position, length, jet size, float effiency, but just as long as its fix..

well done people..............

[Magpie]

So the problem WAS in the overflow tubes - knew it! 
Good on you for finding it Johnie! Another thing to be aware of.
Cliff.

[Johnie]

So the problem WAS in the overflow tubes - knew it! 
Good on you for finding it Johnie! Another thing to be aware of.
Cliff.

The only difference I can see from the OEM and the tubes I put on which are the same size, is I cut the lower end on an angle on all 4 tubes. Does the angle have something to do with allowing more air to affect the pressure in the bowls I do not know. Today I plan to cut those tubes straight at the bottom to remove that angle cut and test it out with the tubes hanging straight down. I will report back...below is a pic of the tubes in the position which caused the problem. They run between the swing arm and case. Then they exit in front of the center stand post.

[shorterdanny]

yippeeeeeeeeeeeeee

tried repositioning the carb overflow pipes to behind the swing arm. and all good problem solved..

no hesitation upto 80mph and still pulling strong just ran out of road.

Really don;t think i would have ever thought of a 2 sec move of the pipes without this thread. So thumbs up all round

Thanks to all in this thread. just what the forum thing is all about..

[Johnie]

yippeeeeeeeeeeeeee

tried repositioning the carb overflow pipes to behind the swing arm. and all good problem solved..

no hesitation upto 80mph and still pulling strong just ran out of road.

Really don;t think i would have ever thought of a 2 sec move of the pipes without this thread. So thumbs up all round

Thanks to all in this thread. just what the forum thing is all about..

Man that is great Danny!!! Glad it worked for you too. Now here is something to think about. I noticed that on the OEM tubes I removed and the new tubes I installed the effects of the fuel & vapors on the end of the tubes have swelled them open a bit more than when they were new. I wonder if the swelling which makes that end hole larger could have something to do with it?

[shorterdanny]

my tubes are just some random clear tubes that the PO had put on, but yes they to have swelled a little.

remembering back to school physics. the pressure and velocity and temp will all vary as the diameter of the pipe changes, so i pressure that there is an occasion why these varibles and the airflow over the end of the tube could cause weird stuff to happen along the pipes length (and into the bowl).

what can i say never going to be a professor  but just glad it work, will certainly have me looking at other seemingly insignificate areas in the future.

[tlbranth]

So Johnnie, where are you getting brass floats for $17? I just ordered one and it's costing over $40 with tax.

[Johnie]

So Johnnie, where are you getting brass floats for $17? I just ordered one and it's costing over $40 with tax.

The $17 brass floats was the Yamiya price. I put on some plastic ones I had from a set of K4 carbs with 4,700 miles. To be honest, I am going to replace all my brass floats. That is the 3rd one I had with pin holes.

http://www.yamiya750e.com/index.php?main_page=product_info&cPath=27&products_id=147