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Author Topic: CB500k carb kit "re-engineered"! need a second opinion  (Read 1693 times)

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Offline rockadoo

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CB500k carb kit "re-engineered"! need a second opinion
« on: December 29, 2012, 02:33:04 PM »
I recently bought 4 carb kits for my 500. during the rebuild I noticed a big difference in the jets. My original jets are twice as big as the ones in the kit. I contacted the people I bought the kits from and they said they have been re-engineered and as long as they fit they will be fine. Now I'm asking for a second opinion. Should I just put my original jets back in or the new ones? The old ones look fine. I'm attaching a couple pics to show the difference


Offline Lars

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #1 on: December 29, 2012, 02:48:29 PM »
That set is usually ok, used them many times. I prefer to use the original ones, if they are ok. You have to have a clear channel from top to bottom, not only the sideway holes. Use a reamer if the channel is filled with dirt, but do not widen it up more than it is as original. This slow jet takes care of the rpm up to about 3000.
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Offline Scott S

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #2 on: December 29, 2012, 03:46:53 PM »
 I had a TON of tuning problems with the "re-engineered" jets. They're too short and will not stay in the fuel level properly, causing a lean and "hanging idle"" condition.

 Re-use the stock jets. All of them if you can. Put new O-rings on the mains and the idle mixture screws (if your bike uses O-rings on the IMS), use the new needle/seat valves. Set your floats properly and be sure to pull the emulsion tubes while the carbs are off the bike. Bench sync the carbs, too.
 Do all of those things and you'll be miles ahead on the tuning.
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Offline rockadoo

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #3 on: December 29, 2012, 07:45:57 PM »
pull the emulsion tubes? If you mean the overflow tubes in the bowls. three of them had cracks almost full length I didnt try to remove them but I did solder the cracks so they no longer leak. I think I will try to find a welding tip cleaner to use on the jets

Offline Stev-o

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #4 on: December 29, 2012, 08:37:58 PM »
pull the emulsion tubes? If you mean the overflow tubes in the bowls.

No, the emulsion tubes.
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Offline lostinthe202

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #5 on: December 30, 2012, 01:22:13 AM »
pull the emulsion tubes? If you mean the overflow tubes in the bowls.

No, the emulsion tubes.

Wow, what a pertinent response.  Lets see, did he spell 'emulsion' incorrectly... no that wasn't it.  Did he call them something other than tubes... no that wasn't it either.  Ah!  He's not sure what the emulsion tubes are... well perhaps.  But why on earth would someone post in a forum specializing in the type of bike he's working on if he didn't know everything there is to know about that bike already?  Surely he's not seeking assistance from people who know more about these bikes than he does? 

Ah, I see.  He incorrectly guessed what an emulsion tube is.  You are certainly correct in stating his error.  Let him figure out for himself that the emulsion tubes are the long brass tube sitting below the main jets in the carb body.  After all, why should we bother typing an extra sentence describing the emulsion tube's location when he could just search for the answer on the internet someplace?  As you know, It takes a long time to type with two fingers.
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Offline rockadoo

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #6 on: December 30, 2012, 06:08:24 AM »
Thanks for the help. I guess the emulsion tubes don't get pulled as I'm not taking the carbs apart from the rack or removing the slides. As much as I'd like to, I've yet to find a sufficient step by step procedure detailing how this is done. My Clymers manual is a terrible reference and I've seen one other reference online but that also failed to relieve my intrepidation. Ignorance on my part prevents me from tearing into something that I may not be able to put back together correctly. :-[

Offline Deltarider

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #7 on: December 30, 2012, 07:05:43 AM »
Can be done with the carbs on the bike. Best way to get them out is to open throttle, so the needles rise. You can then use a matchstick or wooden toothpick and insert this from below into the tubes (that is after removing the main jets). By wiggling you can pry them out. Spraying some WD-40 at forehand may help.
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Offline rockadoo

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #8 on: December 30, 2012, 08:50:18 AM »
If I can push them out from the bottom. Even with the throttle completely open the needle is still  in the center of the throttle body. How would they be removed and how can they be pushed back to their original position. I just put some penetrating oil on them and tried to push them up but they dont move. Again, I don't want to bite off more than I can chew on this project  ???

Offline andrewk

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #9 on: December 30, 2012, 09:04:23 AM »
Doing it halfway will likely not solve your problem.

Take the carbs off, do a real clean, and a real service.  I've never understood why anyone would want to dick around with contorted hands and making special little tools to work at right angles, etc.

Take 10 minutes, remove the carbs, and then you can actually do a real carb service.  Not removing the emulsion tubes for cleaning is about as short-sighted as one can get on this project.  They are notorious for being plugged.

A 500/550 OEM manual can be had for free if you can use Google.  Use the google search on this forum to find many, many, many, many threads on servicing 500/550 carbs.  There's at least one "how to" that I've seen in recent months.

Offline Scott S

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #10 on: December 30, 2012, 10:42:29 AM »
 You don't have to de-rack the carbs, but you do have to pull the needle/slide assembly. It seems intimidating at first, but it's not that bad. Just set up a "clean operating theater" and take your time.
 I've had to use a heavy wooden skewer and a hammer to tap a few out. You'll be surprised how dirty they can get. Be sure to have new O-rings for the main jets, as that's what keeps the emulsion tubes seated.
'71 CB 500 w/ CB650 engine
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Offline Mainerider

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #11 on: December 30, 2012, 12:46:07 PM »
Doing it halfway will likely not solve your problem.

Take the carbs off, do a real clean, and a real service.  I've never understood why anyone would want to dick around with contorted hands and making special little tools to work at right angles, etc.

Take 10 minutes, remove the carbs, and then you can actually do a real carb service.  Not removing the emulsion tubes for cleaning is about as short-sighted as one can get on this project.  They are notorious for being plugged.

A 500/550 OEM manual can be had for free if you can use Google.  Use the google search on this forum to find many, many, many, many threads on servicing 500/550 carbs.  There's at least one "how to" that I've seen in recent months.
[/quot

+1

As a sideline, I ultrasonicaly clean all of the carbs for a local MC shop; they sublet their work to me because I have the proper equipment. Carbs are NOT cleaned simply by pulling the jets and emulsion tubes. What about the tiny passageways in the idle and low speed circuits? They don't collect varnish or gummy residue from Ethanol?  These passagewas are so small that even a little blockage represents a significant percentage decrease in fuel flow. And, you can't access these passageways by sight or by hand. To gain an understanding of just how tiny some of the idle circuit passageways are, take a look at the tip of your idle mixture screw; now imagine how small the passageway must be for flow to be affected by an intrusion as tiny as the idle mixture screw's tip.

The entire bodies need to be ultrasonicaly cleaned using a PROFESSIONAL-grade ultrasonic cleaner, hgh heat, and chemicals specifically optimized for the ultrasonic cavitation process.  Anything short of this and you are just kidding yourself if you think the carbs are fully clean, which they need to be in order to function correctly.
I can't count the number of cases that I have seen where people spent good money on rebuild kits because they thought that would relieve their carb issues, only to find the issues still there afterwards. They give up and bring the bike to the shop and I get the call to pick up the carbs. At least 75% of the time the rebuild kits were a complete waste of money because the carbs just needed a proper cleaning.

Even when a proper cleaning doesn't alleviate the problem, it still serves a critical role by allowing you to eliminate possible carb contamination as the source of the issues; you can then move on to other possible causes.

Carb spray cleaner, dip tanks, Simple Green, etc simply are not in the same league as professional ultrasonic cleaning and do not give assurance that the carbs are indeed clean.
« Last Edit: December 30, 2012, 03:28:54 PM by Mainerider »

Offline seanbarney41

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #12 on: December 30, 2012, 01:05:09 PM »
Doing it halfway will likely not solve your problem.

Take the carbs off, do a real clean, and a real service.  I've never understood why anyone would want to dick around with contorted hands and making special little tools to work at right angles, etc.

Take 10 minutes, remove the carbs, and then you can actually do a real carb service.  Not removing the emulsion tubes for cleaning is about as short-sighted as one can get on this project.  They are notorious for being plugged.

A 500/550 OEM manual can be had for free if you can use Google.  Use the google search on this forum to find many, many, many, many threads on servicing 500/550 carbs.  There's at least one "how to" that I've seen in recent months.
[/quot

+1

As a sideline, I ultrasonicaly clean all of the carbs for a local MC shop; they sublet their work to me because I have the proper equipment. Carbs are NOT cleaned simply by pulling the jets and emulsion tubes. What about the tiny passageways in the idle and low speed circuits? They don't collect varnish or gummy resudue from Ethanol?  These passagewas are so small that even a little blockage represents a significant percentage decrease in fuel flow. And, you can't access these passageways by sight or by hand. To gain an understanding of just how tiny some of the idle circuit passageways are, take a look at the tip of your idle mixture screw; now imagine how small the passageway must be for flow to be affected by an intrusion as tiny as the idle mixture screw's tip.

The entire bodies need to be ultrasonicaly cleaned using a professional grade ultrasonic cleaner, hgh heat, and chemicals specifically optimized for the ultrasonic cavitation process.  Anything short of this and you are just kidding yourself if you think the carbs are fully clean, which they need to be in order to function correctly.

Carb spray cleaner, dip tanks, Simple Green, etc simply are not in the same league.

Mainerider, so you are saying that nobody has ever got their carbs fully clean before the use of ultrasonic cleaners?  Lot's of guys here have been doing this for a long time.  Pre-ethanol gas cloggs up carbs just as bad as ethanol, when it sits around for 5+ years...
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Offline Mainerider

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #13 on: December 30, 2012, 01:14:18 PM »
No,
What I am saying is that if your carbs are clearly dirty with varnish, gum, etc, cleaning only the visible parts is not getting at the complete circuit routes.  Does every carb need an ultrasonic cleaning. Absolutely not. But if you continue to have issues after "cleaning" them (especially at idle or just off-idle), clogged circuits are often the root cause. Sure,  with slightly dirty carbs the low-budget methods may work but the only way to be 100% certain that the carbs are cleaned completely within the bodies is through true ultrasonic cleaning. How many threads have we seen from people with ongoing idling issues after making every adjustment possible? Oftentimes, the root cause goes back to the minuscule idle/low-speed circuits.

 I have seen the results over and over and that is why the shop continues to send me all of their business.  The key, though, is a commercial grade, high heat cleaner and the proper chemicals. What I use does not harm plastic or rubber.

Regarding Ethanol, it is less stable than gasoline and leaves a gummy residue that is worse. It takes very little time for a carb to clog up when ethanol mix is used and the bike sits.
« Last Edit: December 30, 2012, 01:19:22 PM by Mainerider »

Offline seanbarney41

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #14 on: December 30, 2012, 01:21:30 PM »
That is cool.  Any more specific info on what chemicals and what ultrasonic machines it takes to do the job right?  Is any of this practical/cost effective/available to a serious hobbyist?  I know the cheapo/smaller/harbor freight machines with some off the shelf chemical generally fail.
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Offline Mainerider

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #15 on: December 30, 2012, 01:33:50 PM »
I use an American-made commercial quality cleaner ( retail on my mid-size model is about $900 but they go on sale occasionally). Harbor Freight and similar are absolute junk for carbs; HF model is a jewelry cleaner and a low-end one at that.

I use chemicals from a company in Wisconsin; the external carb cleaner is $55 per gallon and the main shellac and gum dissolver is $75 per gallon on sale; Simple Green and the like are just not n the same league, for a number of reasons.

The shellac dissolver is reusable but the machine's high heat evaporates the chemicals pretty quickly so you  end up buying a lot of the dissolver.

Offline seanbarney41

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #16 on: December 30, 2012, 01:43:28 PM »
thanks for the reply
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Offline rockadoo

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #17 on: December 30, 2012, 08:25:31 PM »
 I have an ultrasonic, but it's not big enough to fit a carb into. I saw one at Harbor Freight last week in the $80 range but not sure if it's big enough either. That being said I have previously used Yamaha Carb cleaner mixed with water and brought to almost a boil and dipped an cv carb that was so gummed up the slide wouldnt work. I was amazed how good it worked. Bolted it onto the bike and it ran great.
I guess I'm wasting my time as I'm not going to tear these carbs apart. just finding fuel line for between them would be a chore as no mc shops or auto supply around here carry that thin walled fuel line.  If I had a pot big enough to dip the whole set into the yamaha cleaner I'd try that, but until I find a "perfect" step by step diagram or video I've gone as far as I plan to. I'd rather have the bike run just ok than have it in pieces and never have it run again. I've tackled single and dual carbs and even a triple ,cable controlled mikuni and amal carbs..No linkage no weirdness

Offline Stev-o

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #18 on: December 30, 2012, 08:32:27 PM »
Can understand your hesitation in not wanting to tear them down if you haven't done it.
Check the services offered thread, Harris rebuilds carbs or maybe Mainerider would do it for you?
As far as the fuel line, that can be ordered online.
Good luck.
'74 Honda 750K [836]   '77 Honda 750K project    76 Honda 550K cafe      plus plus plus

Offline Mainerider

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #19 on: December 31, 2012, 06:51:46 AM »
I have an ultrasonic, but it's not big enough to fit a carb into. I saw one at Harbor Freight last week in the $80 range but not sure if it's big enough either. That being said I have previously used Yamaha Carb cleaner mixed with water and brought to almost a boil and dipped an cv carb that was so gummed up the slide wouldnt work. I was amazed how good it worked. Bolted it onto the bike and it ran great.
I guess I'm wasting my time as I'm not going to tear these carbs apart. just finding fuel line for between them would be a chore as no mc shops or auto supply around here carry that thin walled fuel line.  If I had a pot big enough to dip the whole set into the yamaha cleaner I'd try that, but until I find a "perfect" step by step diagram or video I've gone as far as I plan to. I'd rather have the bike run just ok than have it in pieces and never have it run again. I've tackled single and dual carbs and even a triple ,cable controlled mikuni and amal carbs..No linkage no weirdness

The cleaner I have will take a 3 rack completely; most 4 racks fit at a slight angle so I typically immerse one end of the rack for a cleaning cycle, then immerse the other end of the carb rack for a second cycle.  With the cleaner I have, I don't need to break the rack apart for a full cleaning, just pull the jets, emulsion tubes, floats, float valves, etc. The cleaner is powerful enough to completely clean the internal passageways with the rack still together; a huge time and money saver.

Offline Scott S

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #20 on: December 31, 2012, 07:04:45 AM »
 Again, you do NOT have to pull the carbs apart to pull the emulsion tubes. You can pull the slides with the carbs on the rack.
'71 CB 500 w/ CB650 engine
'78 CB550K
'75 Yamaha XS650
'87 Yamaha Radian
 and too many projects...

Offline rockadoo

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #21 on: December 31, 2012, 10:13:48 AM »
If I could get the slides and tubes out without disturbing the synchronicity of the carbs I'd be all for it ! I just know the procedure.

Offline Scott S

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #22 on: December 31, 2012, 11:39:08 AM »
 You will have to re-sync. Removing the slides not as hard as it is intimidating. I've done it on two sets of carbs in the last year. Before that.....never. Synching isn't a big deal either. If the carbs are off the bike at anytime, you'd be a fool to not at least CHECK the sync and bench sync if necessary.
'71 CB 500 w/ CB650 engine
'78 CB550K
'75 Yamaha XS650
'87 Yamaha Radian
 and too many projects...

Offline Scott S

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #23 on: December 31, 2012, 12:15:52 PM »
 Copied these from my manual. Steps 6 through 11 will show you how to get the slides out for access to the emulsion tubes.
  It helps to have some small, sharp bladed screwdrivers to fold back the locking tabs, an extension for your ratchet and a long, small screwdriver to get to the screws on the slode holder. Take your time and do one at a time. Use a wooden dowel or skewer or something to push out the emulsion tubes.


'71 CB 500 w/ CB650 engine
'78 CB550K
'75 Yamaha XS650
'87 Yamaha Radian
 and too many projects...

Offline crazypj

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Re: CB500k carb kit "re-engineered"! need a second opinion
« Reply #24 on: December 31, 2012, 12:42:32 PM »
The biggest/major issue with any system which submerges carbs in any 'cleaning' fluid, any seals which are not removed get screwed up.
The only way to get new throttle shaft seals from Honda is buy a new carb body (good luck with that for a 30~40 yr old bike)
It's quick, easy and expedient, but, it just messes stuff up
Cleaning carbs properly isn't a quick job, any shortcuts will cause damage.
I've had to re-build many, many carbs that were professionally 'cleaned' using very expensive ultrasonic cleaners (one set from a very well known aftermarket carburettor parts supplier)
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