Author Topic: Popping noise from carb (Read 24888 times)

longshanks · « **Reply #25 on:** June 07, 2011, 10:50:11 AM »

Carbs are synced but I haven't taken out the carbs entirely to check the needle positions. Just pulled the float bowls to replace the emulsion tubes and clean out the main and pilot jets. The mixture screws are around 1 1/4 out I think or 1 1/8. The carbs are stock for the K6. I also haven't checked to see if the float heights are correct but they are moving freely.

gnarlycharlie4u · « **Reply #26 on:** June 07, 2011, 12:34:02 PM »

you need this:
http://www.hondachopper.com/garage/carb_info/carb_info.html

enjoy the read. it's quite liberating having that much carb knowledge condensed for you.

Quote from: longshanks on June 07, 2011, 10:50:11 AM

Carbs are synced but I haven't taken out the carbs entirely to check the needle positions. Just pulled the float bowls to replace the emulsion tubes and clean out the main and pilot jets. The mixture screws are around 1 1/4 out I think or 1 1/8. The carbs are stock for the K6. I also haven't checked to see if the float heights are correct but they are moving freely.

yea I'm afraid you might have to pull the carbs on this one.
make sure they ARE CLEAN and the float heights are set correctly as per this article: http://www.hondachopper.com/garage/carb_info/float_levels/float_levels.html

If you can have them ultrasonically cleaned I'd recommend it; it'll do the best job. In fact I bought a good one and I've loved every minute of it, it's so much better than carb cleaner.

JosepyK · « **Reply #27 on:** June 07, 2011, 01:03:02 PM »

Yes, it takes around 30min to get really warm and then the high idle problem surfaces. It's pretty consistent at doing this too. The bike smoothes out under acceleration(1/4 to 1/2 open on the throttle?)
[/quote]

Not sure how late I am to this party but, I had the same idle issue. Took me a couple days to realize that my carb rack had gotten out of synch. Give your carbs a check, a couple may be standing open a little.

gnarlycharlie4u · « **Reply #28 on:** June 07, 2011, 01:05:31 PM »

Quote from: JosepyK on June 07, 2011, 01:03:02 PM

Yes, it takes around 30min to get really warm and then the high idle problem surfaces. It's pretty consistent at doing this too. The bike smoothes out under acceleration(1/4 to 1/2 open on the throttle?)

Not sure how late I am to this party but, I had the same idle issue. Took me a couple days to realize that my carb rack had gotten out of synch. Give your carbs a check, a couple may be standing open a little.

haha THAT'S WHAT IIIIIIIIII SAID. you can't properly sync them till you've got all the other issues sorted out though.

OP if you really do have a vacuum leak then order a new boot(s) and have the carbs ultrasonic cleaned while they're off the bike.
http://gnarlywrench.blogspot.com/2011/05/cleaning-bs-34-carbs-from-81-xs650.html <- me cleaning my buddy's carbs in the ultrasonic. I need to get after shots of them but they're spotless now.

dave500 · « **Reply #29 on:** June 07, 2011, 01:13:23 PM »

Yes valves have been checked twice. I'll try that kickstart method you mentioned, thanks. (Do you mean with the no. 3 plug in and the rest out or vice versa?)

number three in,with all the others out,this will compress on number three only,try the kicker by hand with your ear close to the carb,it might have an obvious leak it might not,hopefully not.

JosepyK · « **Reply #30 on:** June 07, 2011, 01:14:48 PM »

Guess I should finish reading these things before posting. HA

longshanks · « **Reply #31 on:** June 07, 2011, 01:23:03 PM »

Ya, the high idle problem has been fixed. I think it was due to the play on the screw for the return throttle cable. Or it could have been replacing the emulsion tubes, cleaning the jets and syncing.

So if I clean the carbs, set float heights, put new boots on(can I save $100 and refurbish them with wintergreen if they have no cracks?), set needle position, and re-sync and if I still have problems then it's likely an ignition problem right? (timing and valves are set properly)

By the way, mixture screws are set at 3/4 out and mains are at 120.

longshanks · « **Reply #32 on:** June 07, 2011, 01:26:26 PM »

Quote from: dave500 on June 07, 2011, 01:13:23 PM

Yes valves have been checked twice. I'll try that kickstart method you mentioned, thanks. (Do you mean with the no. 3 plug in and the rest out or vice versa?)

number three in,with all the others out,this will compress on number three only,try the kicker by hand with your ear close to the carb,it might have an obvious leak it might not,hopefully not.

I don't think its a bad/misadjusted valve if thats what you're thinking.

Compression on the cylinders is 120 across all of them. They're very consistent(maybe 1 or 2 psi difference)

Spanner 1 · « **Reply #33 on:** June 07, 2011, 01:27:53 PM »

Longfella.... your mains may be stamped '120' but are you sure they are not drilled-out to some unknown size by the P.O. ?? , would explain a lot.

longshanks · « **Reply #34 on:** June 07, 2011, 01:31:16 PM »

Quote from: Spanner 1 on June 07, 2011, 01:27:53 PM

Longfella.... your mains may be stamped '120' but are you sure they are not drilled-out to some unknown size by the P.O. ?? , would explain a lot.

Pretty sure they haven't been messed with, I will check again when I pull the carbs off. All the plugs except no. 1(rich, black and sooty) are a nice light brown color.

dave500 · « **Reply #35 on:** June 07, 2011, 07:25:27 PM »

check the resistance of the caps,are the plugs new?

longshanks · « **Reply #36 on:** June 08, 2011, 12:41:03 AM »

no, plugs are not new. i dont really want to foul a new plug until i figure out what is going wrong, plus they look like they are in pretty good shape.

dave500 · « **Reply #37 on:** June 08, 2011, 12:46:42 AM »

have you got a multimeter to check the caps resistance?were the plugs in it when you got the bike?

longshanks · « **Reply #38 on:** June 08, 2011, 10:51:19 AM »

Quote from: dave500 on June 08, 2011, 12:46:42 AM

have you got a multimeter to check the caps resistance?were the plugs in it when you got the bike?

Yes, the plugs were in it when I bought the bike and yes I did check cap resistance. I believe it was around 10k ohms.

dave500 · « **Reply #39 on:** June 08, 2011, 12:50:10 PM »

your looking for 5kohms,try new plugs aswell.

longshanks · « **Reply #40 on:** June 08, 2011, 01:04:51 PM »

will do

longshanks · « **Reply #41 on:** June 13, 2011, 05:51:18 PM »

Haven't had time yet to test the ignition but I've been noticing that when I ride it the hesitation and stumbling is worse when I open up very little throttle and let the bike steadily accelerate. However, when I open up the throttle maybe 1/4 to 1/2 the stumbling is less and it seems happier upon acceleration and not holding the throttle at constant speed. Anyone have any thoughts as to why?

Spanner 1 · « **Reply #42 on:** June 13, 2011, 09:14:58 PM »

Haven't seen in the 41 back-and-forth posts so far where you have proven the emulsion air feed is good on all 4 ( or any ) carbs

. Saw where you said you cleaned the slow jet and it's cross holes but that is only 1/2 the procedure. The other 1/2 is to clean/prove the righthand brass port( 1and 2 ) in the carb throat is clear thru' to the slow jet cross ( emulsion ) holes. ( lefthand port in 3 and 4 ).
A good squirt of carb cleaner while looking where the c.c. comes out is what to do. If the emulsion holes in the slow jet are not supplied with air thru' this air passage then the slow jet supplies a stream of gas , waaay much richer than the designed 'froth' of gas , maybe 1/2 times leaner with the air to froth the mix........ very important step in the carbs function

longshanks · « **Reply #43 on:** June 13, 2011, 09:46:23 PM »

Quote from: Spanner 1 on June 13, 2011, 09:14:58 PM

Haven't seen in the 41 back-and-forth posts so far where you have proven the emulsion air feed is good on all 4 ( or any ) carbs . Saw where you said you cleaned the slow jet and it's cross holes but that is only 1/2 the procedure. The other 1/2 is to clean/prove the righthand brass port( 1and 2 ) in the carb throat is clear thru' to the slow jet cross ( emulsion ) holes. ( lefthand port in 3 and 4 ).
A good squirt of carb cleaner while looking where the c.c. comes out is what to do. If the emulsion holes in the slow jet are not supplied with air thru' this air passage then the slow jet supplies a stream of gas , waaay much richer than the designed 'froth' of gas , maybe 1/2 times leaner with the air to froth the mix........ very important step in the carbs function

What exactly is the righthand brass port? Is this in the upper body of the carbs?

Spanner 1 · « **Reply #44 on:** June 14, 2011, 02:02:19 PM »

When you look into the carb throat ( from airbox side ) there 2 small air ports, one to the left close to the airscrew and a brass one to the right. These 2 openings extend into the carb and provide a pre-mix of air to both the slow jet and the main jet nozzles; i.e. the fuel gets premixed with this air as it enters ( gets sucked ) out of the jet into the carb throat and into the motor. In other words both the main jet and slow jet need this air to 'froth' the mixture as it is delivered. The bike will run if either/both air passages are blocked but much richer as no air = liquid gas out of the jets. Carb cleaner shot thru' each one must appear under the main jet needle (when sprayed into brass port ) and out the slow jet in the throat when sprayed into port by airscrew. You need to place a finger under the main jet to force the spray out the jet under the needle and also block the slow jet to see spray from its opening which is just ahead ( motor side ) of the slide needle.......... hope this makes sense

longshanks · « **Reply #45 on:** June 14, 2011, 02:45:18 PM »

Quote from: Spanner 1 on June 14, 2011, 02:02:19 PM

When you look into the carb throat ( from airbox side ) there 2 small air ports, one to the left close to the airscrew and a brass one to the right. These 2 openings extend into the carb and provide a pre-mix of air to both the slow jet and the main jet nozzles; i.e. the fuel gets premixed with this air as it enters ( gets sucked ) out of the jet into the carb throat and into the motor. In other words both the main jet and slow jet need this air to 'froth' the mixture as it is delivered. The bike will run if either/both air passages are blocked but much richer as no air = liquid gas out of the jets. Carb cleaner shot thru' each one must appear under the main jet needle (when sprayed into brass port ) and out the slow jet in the throat when sprayed into port by airscrew. You need to place a finger under the main jet to force the spray out the jet under the needle and also block the slow jet to see spray from its opening which is just ahead ( motor side ) of the slide needle.......... hope this makes sense

Yes, that makes sense. I will look into it. Thanks,

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Author Topic: Popping noise from carb (Read 24888 times)