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Discussion Starter #1
Hey guys, i removed the carbs off my cb350. Tried to get the bike to run, no luck. Have spark, but no fuel at all. when i remove the plugs after a few cranks they are bone dry - no fuel. No fuel will even get into the fuel bowl.

The petcock is good, i drained the gas tank through the petcock.

Im gonna grab a can of carb cleaner and advanced auto.
Anything that needs particular attention when cleaning these?
Thank you! merry xmas
 

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NOS351WCM said:
Hey guys, i removed the carbs off my cb350. Tried to get the bike to run, no luck. Have spark, but no fuel at all. when i remove the plugs after a few cranks they are bone dry - no fuel. No fuel will even get into the fuel bowl.

The petcock is good, i drained the gas tank through the petcock.

Im gonna grab a can of carb cleaner and advanced auto.
Anything that needs particular attention when cleaning these?
Thank you! merry xmas
What's your compression?
How did you set the timing?

Everything requires particular attention when you tear these carbs down. Get a manual and print out the fiche picture too.
Have an air compressor handy.
Do not poke any wires into holes or anything.
Do them one at a time, don't mix parts up.
Check your diaphragms.
 

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NOS351WCM said:
Anything that needs particular attention when cleaning these?
Yep, EVERYTHING.... Also, don't get carb cleaner on anything rubber or plastic, don't force anything solid through any holes..... follow the proceedure in the Manual, Do one carb at a time.....IF in doubt, ask first..........

I know this may sound smart-ass, but it isn't meant that way......

It is very easy to damage the carbs or their parts, so you have to be very aware of what you are doing... New carbs (if you can find them) are several hundred dollars each, just the slide/diaphragm assemblies are around $100 each.......
 

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Discussion Starter #4
Yes i know not to stick anything hard through the passages..
I used carb cleaner and an air gun w/ soft tip. I also took out the accelerator diaphragm before i unloaded cleaner on them.
I printed out a parts fische form off line. Very helpful btw. Ill put the carbs back on and try to start it.
How does compression affect the carbs?

Thanks
-dan
 

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Less compression= less vacuum drawn= less lift on carb slide=smaller openings
Very low compression may not draw enough fuel up the jets/through the passages and into the cylinders to fire (unlikely, but you never know)..... or that the valves aren't fully closing, or they're bent/stuck, or etc, etc.........
Mostly, the point is that compression should be one of the first few things checked... Hard to do accurately if you can't get the engine hot, but even a cold reading is a good (relative) starting point.
Good compression means it's OK to try to start it (after you go over all the basics... Oil, fuel supply, timing, valves, etc, etc...)
Bad or unexpectedly low compression not only indicates you WILL have to rebuild the engine, but also is a good diagnostic tool for determining where the problems lie..... (not to mention that it is a waste of time to try to start it).......
JMHO... Steve
 

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NOS351WCM said:
Hey guys, i removed the carbs off my cb350. Tried to get the bike to run, no luck. Have spark, but no fuel at all. when i remove the plugs after a few cranks they are bone dry - no fuel. No fuel will even get into the fuel bowl.
When you pulled the carbs off did you remove the float bowl and and check to see if any fuel would flow with the floats in the down position?
 

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LOL.... I don't even use the carbs when test firing.... I duct-tape the port closed, punch a #2 pencil sized hole in the tape and squirt in an eye-dropper of fuel.... Doesn't run long, but if it burps and starts, clean/rebuild the carbs....
 

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Discussion Starter #8
Re: How to clean a keihin carb

Ahh i see how the compression could affect the carb function. Interesting. Is this only with these kinds of carbs? The carbs on my dirt bikes have the throttle cable attached to the carb slide.

I put the carbs back on. hooked everything up, cranked and still nothing.
Pulled a spark plug, checked for spark - have spark. but the plug was bone dry no fuel what so ever.
I took out the screw on the bottom of the float bowl on the right carb and no fuel came out

So my problem is no fuel gets into the float bowl. Im stumped. There must be some restriction or somthing - right?
I used some starting fluid(not much, my fellow tech at work said too much starting fluid dries the cylinder walls) it ran for 3 seconds, just enough time to burn the starting fluid vapors then the bike would die.

I did have this bike running over the summer, so it will run, but just not now.

Do i need special tools for taking the carbs apart? i couldnt remove the floats, the pin the holds it was stuck pretty good.
Im not sure where to go from here. any ideas
Thanks fellas -Dan
 

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Think of the float bowl as a toilet tank...When the fluid level gets low, the valve opens as the float drops (sound familiar?)... This allows the bowl/tank to fill until the float gets back to its "set" level, where it closes the valve.... Same in a carb...your valve is stuck closed because the float can't drop.....so no fluid to refill it..............
 
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You HAVE to remove the pivot pin and float to fully clean the shut-off needle and seat.
A thin pin punch can gently be used to push/ease the pin out..... Carefully!.... the cast posts are easily broken if you "miss" the pin..... I've been told a thin nail has been known to work also....
 

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66Sprint said:
A thin pin punch can gently be used to push/ease the pin out..... Carefully!.... the cast posts are easily broken if you "miss" the pin..... I've been told a thin nail has been known to work also....
Yup, or else this can happen.

 

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I have used small finish nails with the point ground off a bit (just to make it more blunt) as a very fine drift pin for this very job.

I use the very smallest socket I own (4mm??) as a backstop against the cast post to prevent breakage. Set the socket on a stack of firm material up to such a height that the carb can be turned sideways and rested on the socket. Kind of a rube goldberg setup, but you definitely want a firm backstop to the post. And you want it oriented vertically if possible so gravity works FOR you. Flood the whole thing with penetrating oil first and allow to soak a bit.

However, if the post STILL breaks, as shown, I've built them back up successfully using JBWeld. Wrap the pivot pin in one or two layers of fine Saran Wrap at the broken post end and install. Build up the JBWeld over the pivot pin and once it's set, the Saran Wrap will allow the removal of the pivot pin. Done and successful.

Good luck.

Kirk
 

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Discussion Starter #15
When you say timing, do you mean ignition timing or sync the carbs? If youre referring to ignition timing then no i did not check the timing.
 

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Discussion Starter #17
Sry didnt mean to post that twice..
Yeah those pins were pretty corroded, i tried to see if they would come out, didnt force them, but it wasnt happening. Theyre stuck good. Ill try the nail method and file the tip down. hope i dont break anything wish me luck
 

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I fixed my issue of not getting fuel to the bowls this weekend. It was a combination of a non-free flowing petcock due to junk Kreem liner and incorrect float settings. The 18mm setting recommended was not getting it done, I'm more at 23 mm or so. I took the carbs off and ran a hose to the bowl under running water and played with the settings until the floats will allow the bowls to fill up but not allow them to fill beyond excess and spill water out of the drain.
 

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"The 18mm setting recommended was not getting it done, I'm more at 23 mm or so"

That's cuz your 722a carbs are the last in a series of carbs for those bikes. The earliest model, the 350a was the 18mm float setting. Look at the carb settings here.

viewtopic.php?f=15&t=2385

Yours is the same as the 3D I think. Someone please correct me if I'm wrong. Don't feel bad. The first problem I had with my KO was not realizing I had later year carbs and trying to set them too high.

Edy
 

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BTW the fiche does NOT show the actual differences in these carbs. Its all late year fiche for those carbs. In other words the float for the KO is not shown correctly. The parts number will be right but the float does not look like that.

Edy
 
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