'81 cb650c idle jets, how do i clean them?

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nashbuilder
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Re: '81 cb650c idle jets, how do i clean them?

Postby nashbuilder » Thu May 17, 2012 11:49 pm

OK so after 6 hours of work tonight with someone who has a lot of experience on carbs and motorcycles it has been determined that one major issue is that the accelerator pump nozzles are most likely clogged. When we push the throttle there is no squirting of gas coming out of the accelerator pump nozzles. What options do I have to make sure those nozzles are clear?

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Volker_P
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Re: '81 cb650c idle jets, how do i clean them?

Postby Volker_P » Fri May 18, 2012 6:14 am

Nozzles are not the primary problem of acclerator pump malfunction.
First questionis if the rod moves at all.
Then diaphragm must be intact (including the small parts for the valves).
Nozzles may be tested by blowing through.

Neverheless the accelerator pump plays no role for your idle issues idle.
Here you need clean idle jets (blow through, they may be really tough to be cleaned).
But basically you seem to have a synchronization (or air leak) problem if it still should idle at 5000 at idle knob out.
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nashbuilder
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Re: '81 cb650c idle jets, how do i clean them?

Postby nashbuilder » Fri May 18, 2012 9:15 am

When taking the accelerator pump off we are able to squirt out the pump. When I put it on I am not getting any squirting out of the nozzles. That is what I am trying to fix right now. Any ideas of how to make sure those nozzles are not clogged?

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Volker_P
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Re: '81 cb650c idle jets, how do i clean them?

Postby Volker_P » Fri May 18, 2012 11:25 am

Does the rod move (it should be pressed down slowly by the spring mechanism) when you open the throttle? Or does it just go down fast (would mean no pressure on fuel side). Or is it blocked? Or does it not come up again? Or is your idle knob out too far to acivate the accelerator pump at all? Check out these mechanical issues first.
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forum links to common technical issues

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nashbuilder
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Re: '81 cb650c idle jets, how do i clean them?

Postby nashbuilder » Fri May 18, 2012 3:00 pm

Yeah I will have to look of the return of the rod when the throttle is released. Right now when the throttle is pulled open the rod moves and I am pretty sure it comes right back to it position when the throttle is released but I will double check that.

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Re: '81 cb650c idle jets, how do i clean them?

Postby Volker_P » Sat May 19, 2012 3:41 am

So how does the rod move when you open the throttle quickly? Just moves with the mechanism that previously blocked it there or do you see some retarded movement (which is essential) until it reaches its final position?
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forum links to common technical issues

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nashbuilder
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Re: '81 cb650c idle jets, how do i clean them?

Postby nashbuilder » Tue May 22, 2012 11:09 am

So I am at a lose for what to try next. I have had multiple people who rebuilt CB's look at my bike and we cant figure out what is causing the problems. Do any of you guys know someone in the TN area that knows these 81-82 CB650's with these carbs? I am at a loss of what to do next.

Thinking about buying new boots, accelerator pump rebuild kit but they all seem to check out fine based on what 6 other wrenchers have said.

Todd Richards
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Re: '81 cb650c idle jets, how do i clean them?

Postby Todd Richards » Tue May 22, 2012 11:50 am

nashbuilder:

Were you able to verify correct adjustment of the fast idle tab? (assuming your issues with high rpm upon startup remain...)

there is a difference between the idle adjustment screw and the fast idle adjustment tab, they are not 2 of the same.... I can get pictures from service manual if you are not sure what i am refering to?

I skimmed thru your previous posts and wanted to be sure that you have successfully completed the bench sync & that both the intake and choke petals move freely throughout their entire range of operation, without binding? Also checking that there is no binding as a result of the accel & choke cables being hooked to the carburetor linkages, upon assembly intake boots.

I admit that am somewhat puzzled here.... from my experience with the acelerator pump, if the individal carburetor accel. jets are faulty/plugged.. then this is most noticable when twisting the throttle for hard acceleration. I am not familiar with the accel. pumps causing the engine to rev and stay at high RPM's. The accel pump rod is activated thru a series of linkage that rely on spring pressure (rather than direct mechanical coupling) to apply a uniform force to the rod as it is depressed.

I hope this helps you...

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Re: '81 cb650c idle jets, how do i clean them?

Postby Volker_P » Tue May 22, 2012 1:30 pm

nashbuilder wrote:So I am at a lose for what to try next.
I am sure you did try out everything to clean out the idle jets and you are convinced you can't do any more there but did you ever verify that you can really blow them all through?
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

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nashbuilder
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Re: '81 cb650c idle jets, how do i clean them?

Postby nashbuilder » Wed May 23, 2012 1:46 pm

Yes I can feel the air coming out of the hole in the venturi of the carb. I am going to take them back off and make sure the accelerator pump nozzle is cleaned out.

The first burst of gas when you start a bike up comes from the accelerator pump nozzle correct? The bike wont start unless I spray gas in to the carb from the air box.

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Volker_P
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Re: '81 cb650c idle jets, how do i clean them?

Postby Volker_P » Thu May 24, 2012 1:22 am

The accelerator pump basically should add fuel manually at the point of sudden vacuum breakdown when you open the throttle from completely closed. This is just to avoid throttle response hesitations.
The CB650 carbs are the first carbs equipped with that pump. Previous SOHC CB's did not have them and some CB500/550 guys install PD51 carbs to have the accelerator pump (which requires the 550K3 ports).
It is also helpful for the cold-blooded CB650 engine to be twisted a few times before you press the starter.
Nevertheless it is not really required for reasonable behavior and plays no role for idle issues.

As you have a 1981, do you still have the vacuum shutoff? If yes, worth a try to bypass it.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

nashbuilder
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Re: '81 cb650c idle jets, how do i clean them?

Postby nashbuilder » Thu May 24, 2012 8:49 am

No i took the automatic petcock off and put a screw in the #2 vacuum port to cut it off. The idle issue I am not to worried about right now. I cant even get the bike to start now unless I spray gas through the airbox. It idles fine when I start it up and just let it idle, but when I give is throttle it dies once the throttle is released.

Todd Richards
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Re: '81 cb650c idle jets, how do i clean them?

Postby Todd Richards » Thu May 24, 2012 10:16 am

I just want to review a bit to make sure i understand where you are at:

This has me stumped!!! Hopefully i can be of some help here?

1) carburetors cleaned and reassembled, bench sync complete, no binding in choke or throttle pedals?
2) all gaskets and o-rings replaced/reinstalled after cleaning/rebuild? It might be worthwhile to look at a honda parts list microfiche to be sure all gaskets & o-rings were there to begin with? ( i actually saw a case once where that plastic ring seal that assembles under the carburetor slides was upside down & the little paper seals (kidney bean shape) were missing).. i am not implying that these would be the cumulative cause of what you are currently experiencing, but it is a good idea to know that your seals and gaskets are all acounted for and in proper working order...
3) fuel flows freely from tank to all carburetors? if you were to loosen the float bowl drain screw, fuel would drain and continue to drain until screw is tightened, for all 4 carburetors?
4) when running, firing on all 4 cylinders? (exhaust header pipes uniform in temperature?)
5) engine needs help to start.. once started, how much choke is used to maintain? full choke when cold? half choke when warm? no choke when up to operating temperature? Does engine die at any stage when choke is fully removed? Remember to have a fan blowing on the exhaust header pipes, to prevent discoloration.
6) can you observe the choke petal rods during operation? (tank removed, using long piece of fuel tubing to supply fuel to carbs) If so, mark the choke petal rods with a sharpie, in the same relative location such that you can observe them (the markings) when the engine is running & choke applied

How are they (the choke petals/rods behaving with respect to each bank, keep in mind that the #3 & #4 carburetor choke and common rod are linked to #1 & #2 via that nasty little choke spring and could be at a different open/closed position when in use, during operation.

That is enough for now. I recently rebuilt a set very similar to these for my bike and am tring to get an idea of you engine/carburetor behaviors. I kept a log book of notes during my rebuild of all the before and afters! My hope is that I will be able to relate the issues i had back then to some of yours, and possibly help with a fix.

I hope this helps

nashbuilder
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Re: '81 cb650c idle jets, how do i clean them?

Postby nashbuilder » Thu May 24, 2012 1:24 pm

1. Correct and the sync was good with a vacuum test.
2. New o-rings with the carb kit - check
Could not find O-rings for the Accelerator pump, gas dispersion tube o-rings and accelerator pump tubes.
All reinstallation I am 99% confident that all o-rings and other parts are were installed correctly.
3. Gas flow seems fine, I took a clear hose and put it on each float bowl loosed the screw and gas flowed . I bent the tube up to see how high it fills up and it fills up to the proper hight in the bowl.
4. All pipes were getting hot evenly.
5. Once I sprayed gas in the carbs to get it to start. I started with full choke, once the idle rose to 2500 I pushed it in half way and it continued to stay around 2-2500. The pipes were all worm so I pushed the choke all the way in. Idle dropped down to 1200-1500 and on a carb sync vacuum test they were all working nicely.
6. I can't observe the choke petals (plates as I was calling them)unless I take the air handler off. The carbs have to come off to do this. When they were off the bike they were moving very nicely. With carbs mounted on bike and looking between #2 &#3 carbs I can seen both rodes moving, therefore all 4 plates are moving and should still be in sync.

Should I take the carbs off, air handler off, and then reinstall the carbs inorder to watch the carb plates?

Where does the first burst of gas come from to start a bike cold? Slow jet or Accelrator Pump. Obviously this is A problem since when I spray the carbs with gas it starts up no problem.

Todd Richards
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Re: '81 cb650c idle jets, how do i clean them?

Postby Todd Richards » Thu May 24, 2012 2:18 pm

i wouldn't remove the carburetors, not just yet.
basically i wanted you to observe if the choke rods, that control the choke plates were opening & operating together as a set of 4, and closing uniformly. the reason i mentioned this was because the first time i did a carb clean and rebuild, i didn't get that nasty little choke spring exactly right, this caused the carbs/engine to run funny because the choke plates were not always in the same place in the throat opening... (sets 1&2 vs 3&4 respectivly)depending on where i was at with the throttle, i saw some fluttering of the choke plates for #3 & #4, whereas #1 & #2 were somewhat more stable/constant with respect to movement.

The idea of a sharpie marker mark on the choke rods would give you a visual during operation if a set of choke plates were possibly fluttering whilst the other 2 were stable. from what you mention, it sounds like they both move freely? you needn't remove the airbox to see the plates.

Lastly, are you 100 % sure that all internal carburetor passageways & jets are completely cleaned? the PDF file from Mcgregors carburetor cleaning services goes into very good detail regarding the cleaning procedure. a pine sol soak wont get the gunk from the smallest of internal passages, if they were to be completely clogged. please take the time to read it fully, then reflect back to see if there were steps mentiond that may have been skipped?

I am still stumped as to why your bike dies when you let off the throttle?, it takes it, then dies after you let off.. right?

Do you recall during rebuild if all throttle slides moved up and down with the same amont of resistance/ all moving freely without binding?
no bent/ elongated springs?

Once warmend up and off choke, adjust the idle a little higher, give it a little throttle, let of and see if it dies with the idle speed slightly increased? See if there is a point ~2k where you have the idle set a little higher and the engine remains running when throttle is released?

remember to have the cooling fan turned on

from your descripton of idle and choke position, i would say that your fast ldle tabe is set correctly.

I also replaced the air tee' connectors on my carburetors, they were badly cracked & did not seal tight.

from all of this i am beginning to think that whilst the jet (s) may be cleaned, they may still be partial blockage in the internal passageways...

the first burst of gas needn't come from the accelerator pump to start the engine. that is not why it is there.......

i hope this helps you.. Will look thru my log book tonight...


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