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Bogging at 3000 rpm Keihin Carbs...

garbal

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Saskatchewan Canada
I'm at the end of my rope here, I have had the carbs off 5 times now, apart back together, apart, back together.
I've cleaned them ultrasonically for about 5 hours... blew everything out put them back together and back on and the problem persists.

My buddy keeps telling me it's dirt in the little passages... is this still possible. They looked very clean and I blew everything out... is this still

a carb problem or should I be looking elsewhere.

Firstly it used to bog out between 3 and 5000 rpm, if I pulled the choke it would light right up, now the choke doesn't even help, it just bogs and sputters at about 3-3500 rpm... that's it... runs perfect at idle but once you open it up ... it just coughs and sputters... let off ... fine,

Anyone else have a similar issue. I'm hoping someone has and has found an answer to this issue. I've been told I need to clean the carbs again...

This is my second set of bodies... what am I missing?

Also... New to the forum. Looking forward to meeting and hearing from you guys!

Take care,

Garbal.
 
You can clean carbs till the end of this planet and might not be them.

The engines are well known for valve problems due to them burning then everybody blames the carbs. The CV type carb performance is based on basic engine condition, it being off then carbs do not work right and tend to go super rich due to slides not opening due to engine draw being off and the not revving up to max rpm then.

Valves set by changing shims and nobody ever does it then they burn because these tend to close up clearance instead of open to looser like most engines do.

Engine compression check and 170 psi is the standard new engine spec, they run down to 130ish then it gets much worse, 100 psi is a dead cylinder that never will run right ever. If you aren't in that range forget the carbs until you are. With low compression the engine will not rev regardless of what you do to carbs.

Be advised as well that if ethanol is used in your local fuel there can be deposits in the small spaces with the strength of concrete, many have to work the carbs more than 2 times to get it out. There is a plug pressed into carb body bottom next to idle mixture screw hole that blocks off a pocket that feeds the transition holes past closed throttle, if that pocket has crap deposit in it then the carb can be considered junk.

Pods or individual air filters = worse. The OEM airbox helps the slides to lift more.
 
Wow, Excellent advice, I didn't consider anything other than the carbs until I had them on and off 5 times.. .then I clued in and thought maybe I'm chasing my tail with the carbs. As you suggested, I did a compression test and they are 130 across the board. I'm ultrasonic cleaning the carbs right now, I've had them in for about 2 hours with CLR.
I've strained the CLR once and there's a lot of black crud in the filter... I'm going to run them through a couple more times then rinse them in water for a couple cycles and see what comes out. Someone else suggested jetting up the primaries a bit, Not sure what a bit means but what would you suggest. Do you think it's a compression issue more than anything else?
Would a valve adjustment help at this point or has that ship sailed?

Thank you so much for your help. I so appreciate it.
 
Well, that was it... took them apart again, cleaned them again... CLR for 2 hours, more crud was coming out, two rinse cycles in Water in the Ultrasonic Cleaner, put them together, said a little prayer... and success... No more bogging, just really dirty carbs.

Thank you to all who replied and for the great suggestions.

I guess the lesson learned here is when you think they're clean, clean them again!
 
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