Topic: A few gas related problems...1978 CB550

[King_Panther13]

 Hello all,

 I'm running a '78 CB550 on a '73 CB500 frame, with what I believe are '73 CB500 carburetors. The gaskets I ordered for 550 carbs didn't fit, but the one's for the 500 did, which is why I think this. I recently payed about $700+ to a mechanic to fix the timing, ignition, clean the carbs, and a few other minor things. They also put in smaller idle jets, as the old ones were drilled out. Before bringing it to them, I got about 20 MPG, and my idle would hang up around 1500-2000 before dropping to about 3-400 when coming to a stop. I was leaking fuel pretty badly as well. I'm using  a 4-1 Kerker exhaust.

 The mechanics told me that my problem was that the baffle in the exhaust was plugged up, so they completely removed it and now I'm running on a semi-open pipe (the plug is still in). The bike now idles around 3-400 all of the time, and immediately drops when it should. If I try to raise the idle speed, however, I run into the previous problem: A hang up around where I rose it, and then a drop to 3-400. The idle is so slow, I occasionally stall at lights. On top of that, it seems as if my bike doesn't want to rev past 7000 RPMS (and that's pushing it, usually around 6k it'll start slowing up) and now I'm still only getting about 20MPG. Sometimes when giving it gas, it'll act as if I'm only giving it a bit of throttle, and I have to hold my throttle at a certain point and wait for the bike to suddenly lurch forward. When I forget to turn the petcock on (only here and there) the idle speed seems to go to where it should be (around 900 or so) which I'm thinking could be related ( I have no clue).

 I told the mechanics, and they said that lowering the needles may help, but that's another 50 bucks I'd have to pay them. They also told me to ride it softer (I went an entire tank keeping around 3k RPMS except for two occasions, and only ended up getting about eight more miles to the tank) and to try changing the air filter. The air filter looks fine, but when I remove it I can push the bike further to about 8k, and it'll idle higher (around 1500 or so) but then immediately drop to about 300-400 as it did before removing the baffle or when I try raising the idle. Oh, and the tachometer (as well as the entire front end and wheels) is off of an '81 Nighthawk, so I don't even know if the numbers are correct.

 I'm obviously a noob to this....this is my first bike, and I'm not very mechanically inclined, though I have a feeling that it'll help if I start becoming so. I think the mechanics may be yanking my chain a bit to get money out of me, but now I have barely any left due to parts, repairs, and etc.

 Any advice? Oh, and I tried search and got a few different solutions to sole problems, but I'm just poking around to see if maybe there's any particular fix to my set of symptoms.

[scottly]

This makes me sad: you paid over $700, and it sounds like the only improvement is gas is no longer leaking?

Sounds to me like your float levels are wrong, causing a rich mixture, as it idles better when you leave the petcock off. To confirm a rich mix, look at your spark plugs: they will be black and sooty, or, in extreme cases, black and wet. If so, check the fuel levels in your bowls using the "clear tube method". 

[King_Panther13]

 Well, a few more improvements...it shuts off faster now when coming to a stop, and gets a lot more horses, but that's about it. I'm fairly certain that I got gypped. I'll be checking the plugs tomorrow (my motorcycle enthusiast uncle only has socket sizes too big and too small for my plugs, so I'm hoping Auto Zone will be able to help). I can say that the exhaust is leaving black residue on the inside of the pipes, and seems to be smoking a bit. He also says that it "feels like it runs rich all the way through."

 My aforementioned uncle also said that the jets may be too big. The PO drilled out the idle jets, and apparently my mechanics never checked to see if any of the other jets were drilled out or not. They did, however, replace the drilled out jets with stock jets. I never thought of the floats (the mechanics said that they adjusted all of that accordingly, synced them and all sorts of things, but I'm starting to think that it's best not to trust them anymore) I'll look up that method and check it out.

 If it doesn't turn out to be the floats, and turns out to be the jets, what size jets should I use considering that I'm using the original airbox, and a 4 in 1 Kerker header with no baffle?

[scottly]

 My aforementioned uncle also said that the jets may be too big. The PO drilled out the idle jets, and apparently my mechanics never checked to see if any of the other jets were drilled out or not.

I was wondering the same thing....

[King_Panther13]

 I'm thinking it'll be easier to check float levels than jet sizes, so I'll go ahead and do that first then give an update to what's happening. If the float levels seem to be fine, and the plugs are rather black, then I'm going to need to find what the proper jet sizes are....google turns up nothing hehe, I guess I'll lurk around here a bit more and see what I can dig up.

[scottly]

I'm thinking it'll be easier to check float levels than jet sizes, so I'll go ahead and do that first then give an update to what's happening. If the float levels seem to be fine, and the plugs are rather black, then I'm going to need to find what the proper jet sizes are....google turns up nothing hehe, I guess I'll lurk around here a bit more and see what I can dig up.

Exactly right! There's LOTS of info here, including stock jet sizes for 500/550s. Use the search feature...

[King_Panther13]

 Here's something I haven't seen asked: If I were to switch over to pods, would that help counteract the problem? Running my airbox with no filter helps a tiny bit (I can rev to 8k compared to 6.5 or 7, haven't ridden long enough without it to tell how it effects mileage). I just think that switching to pods may be a bit easier than fiddling with the jets, if the floats turn out to be at the correct level.

[bucky katt]

pods can be a reali #$%* and a half to tune for.............really really difficult.

[scottly]

OH NOOooo!!!! You are going to start the whole pods vs air-box debate/fight again!!

[King_Panther13]

 I just thought that maybe slapping on some pods would help lean the thing out, and at least get it semi-decent. I don't care about perfect as long as it's able to rev to its true redline (which I'm sure is around 10k or more) and can manage more than 20MPGs. I'm hoping for 50 or so, but I think somewhere in the 40's is more realistic. If it's really that much of a hassle, I'll just start trying different jet sizes (after confirming float levels and whatnot of course) and see where it goes from there.

[scottly]

Slapping on some pods won't be leaner than the stock system with the filter removed, especially at idle. Check the fuel level first, if OK, check the jets. You might want to buy some new spark plugs, too..

[King_Panther13]

 Alright, I'll forget about that idea then. I'll check plugs, and fuel level tomorrow...and probably buy some new plugs as well, if my current ones are too bad. Then I'll go on to finding someone who can give me new jets for a bit less than an arm and a leg.

[Stev-o]

First off, I'm sorry to hear you paid $700 and aren't much better off.
You may want to consider calling him, explain that the bike is really no better and ask for a partial refund.
Then, find a compentant mechanic that knows these old bikes and can repair it right the first time.
It definatly sounds like a carb/jets issue, I would suggest a good going through to start new, including a good cleaning. I have been though this and ending up buying a new/used rack of carbs w/new needles and seats.

Good Luck.

[King_Panther13]

First off, I'm sorry to hear you paid $700 and aren't much better off.
You may want to consider calling him, explain that the bike is really no better and ask for a partial refund.
Then, find a compentant mechanic that knows these old bikes and can repair it right the first time.
It definatly sounds like a carb/jets issue, I would suggest a good going through to start new, including a good cleaning. I have been though this and ending up buying a new/used rack of carbs w/new needles and seats.

Good Luck.

 I stopped by the shop, and they told me that they did the work for "performance, not economy" and that if I wanted to get better economy, it'd be another fifty bucks for them to lower the needles....and then suggested to not ride the bike so hard, or change the filter. It's a duo btw...and everybody in the area referred me to them, because apparently they're the only shop in my county willing to work on a bike older than like an '85. They did thoroughly clean them, and I bought new needles and gaskets. The jets are probably the worst problem, as it's hard to tell if they were drilled out or are still stock. The PO did however tell me that if this rack of carbs is unsat, he'd trade me for another set (he has two more) but I'd hate to get another set when these were just cleaned and synced.

[scottly]

Evidently their idea of "performance" is different from mine. A Honda small-four that only gets 20MPG, won't rev past 8K, and you had to remove the filter element to achieve that??? Where are you, so anyone near you knows where NOT to go for repair! (Put your location in your profile) 

[King_Panther13]

 Updated....Winter Haven, Fl in the notorious Polk County. At least, the residents here think to seem it's notorious.

[Ayrity]

I'm in Tampa, not crazy far from you, I am learning how to work on these bikes more and more every day, so I am not an "old timer" but I have come a long way, cleaned my own carbs, fixed my leaky petcock, new chain and sprockets, and going to do a whole engine clean over the summer. So if you want I would be MORE than happy to help you tune those carbs up right, and help you figure out the problems. At the very least, I know a great mechanic here who can help if I cant/dont have the tools etc. Feel free to drop me a message on here or email me Ayrity@gmail.com

[King_Panther13]

 Pulled one plug, turns out to be very black. The bike seems to be getting worse. My max rev keeps getting lower and lower, and my gas mileage seems to be decreasing as well. The idle now sits around 200 or so, and I constantly stall out at lights and whenever I pull the clutch in completely and let it idle for a few seconds. The bike smells quite rich, and leaves a nice black residue on the inside of the exhaust.

 I never checked the float levels, but I'm fairly certain it's the jets either way. The mechanics of course continue to blame me for not wanting to buy a jet kit, when they're the ones who said that I wouldn't need one. They also said that it's "impossible" for the idle to be dropping so badly, unless someone touched it. I wish people could just accept responsibility for their actions. I'm considering filing a credit card dispute against them, but I don't think it'll go very well (the work order was very ambiguous).

 I ordered four #100 main jets for the 1973 carburetors(on Bikebandit it just says "Jet Set #100") and four D7EA Spark Plugs (I dunno if the number makes a difference, it just says that on the website.) Once they come in, I'm going to lower the needles to the middle position (Which I think is the stock position) and redo the plugs+jets, and see where it goes from there.

[Stev-o]

I'm considering filing a credit card dispute against them, but I don't think it'll go very well (the work order was very ambiguous).

 

Do it!

On my '76 550, adjusting the idle is very simple, just turn the thumbscrew clockwise [not sure if yours is the same?]

Good Luck.

[King_Panther13]

 Then it'll go into the same problem that I brought the bike to the mechanics for....the idle will hang up around where I set it by the screw, then drop to about where it is now after a few minutes...and then sometimes it'll hang up at higher RPMs, then drop to the setting, THEN drop to the low idle. They supposedly fixed it, and it supposedly was because the baffle in my pipe was clogged up, but if I try to raise the idle it just comes right back. I think once I replace the jets, set the needles properly, and change out the plugs I'll be fine.

[scottly]

 I never checked the float levels, but I'm fairly certain it's the jets either way.

Why do you think it's the jets when you haven't bothered to check the float levels first??? Using the clear tube method is the easiest test you can do!

[King_Panther13]

 I never checked the float levels, but I'm fairly certain it's the jets either way.

Why do you think it's the jets when you haven't bothered to check the float levels first??? Using the clear tube method is the easiest test you can do!

 Because if the idle jets were drilled out, what stops the mains from being drilled out as well? Even though my mechanics didn't fix the true problem, I'm sure that they balanced and synchronized the carburetors well. I learned from other sources that these mechanics have a great reputation of fixing what doesn't need to be fixed, and overlooking everything else. If I rejet the carbs and the problem still exists, then I'll play with the float levels. It doesn't hurt to have new jets either.

[scottly]

The mains may have indeed been drilled, but the point is, that you can check the fuel levels in the bowls without taking anything apart. Then, if they are off, you can adjust them when you remove the bowls to check the jets. Do the easy tests first!!

[King_Panther13]

 Good call then. I couldn't find a good article on the clear tube method, but I'm certain that my metric-loving uncle will know the trick, or at least something similar for before I take the carbs off.

[scottly]

Check to current thread on fuel height! He posted pictures!

[King_Panther13]

 Well, I didn't get around to doing the fuel height test (didn't have the time to look around for a clear tube...hehe...my uncle was too busy to help) but I did change out all of the plugs to brand new ones (the old plugs were all extremely black) and took off the carbs. I couldn't figure out how to get to the needle (I was at a friend's house, so I couldn't come on here to look at the guide) but I did change out the jets. The old jets looked really grungy, and the O rings looked almost shredded. They were labeled as 105, and I couldn't tell if they were drilled or not. The jets I put in were 100s. The carburetors I use (off the 1973 CB500) use size 100 jets for stock, though according to some specs I've been reading, the carbs for the 1978 cb550 (the engine I use) use a size 90 jet. Maybe that's the problem? Or does the difference in carburetors make up for the large difference in size?

 Anyhow, after accidentally breaking a fuel filter AND a line, and jerry rigging a long line into a large filter, I took her for a ten mile test run. She ran a LOT better on the low end...didn't need to rev up to 3k to take off. No more stuttering in the 0-3k range either. Idle seemed to correct itself around a cool 800 RPMS.

 Problems I still noticed: I would cut out around 6500 to 7000 RPMS in second gear...before it was just at 6k (sometimes 7k if I was lucky) which I thought at first was the exact same as the old jets, until I realized that I was going a LOT faster than I thought I was. Before when I capped out around the 6-7k mark, I was probably doing 60 ish. I was doing about 75-80 when I looked at the speedo.

 I'm thinking maybe since the engine is supposedly meant for size 90 jets, I should drop down another size or two...and I'm going to ask the mechanics tomorrow if they remember where they put the needle on the clip. I don't want to lower the needles if I can help it, I'd like to keep them in the stock position, and just keep lowering jet sizes.

 Should my next step be something like 95?

[scottly]

Check the fuel level in your float bowls, please.

[King_Panther13]

 That will be done tomorrow afternoon. I'm kinda can't-even-afford-a-mcdouble broke right now, so I have to wait for my uncle to give me a hand doing the float level checks, or either that I need to wait until next paycheck to buy some clear tubing of my own.

 If the float bowl levels are fine, then would it just go back to the jets being too big? Or possibly the needle being in the wrong position. Ugh, gotta call the mechanic to check where they set the needle...if they even remember.

[scottly]

Don't worry about "ifs" yet. First things first. BTW, the clear vinyl tube will probably be cheaper than a mcdouble. You can get it at places like Ace hardware...

[King_Panther13]

 Well, tomorrow after work I'm just going to bug one off of my uncle. Then maybe even try playing with the needles while I'm there.

[Stev-o]

Why are you using 500 carbs?

[King_Panther13]

Why are you using 500 carbs?

 It's how I got the bike. I didn't even realize the carbs didn't match the engine until after doing some work on the bike.

[jessezm]

One thing you mentioned in your first post was that your tach was off of a nighthawk.  Do you know that the ratio is the same between these bikes?  I believe that the small Honda fours used a tach with a 1:7 ratio, but I don't know what the nighthawk is.  What year bike was it off of?

I just can't believe that you were actually getting a tick-over at 3-400rpm.  Obviously, the tach wouldn't impact your performance, but it would be nice to know whether your RPM readings are correct.  There is no way to do proper carb-tuning otherwise

[King_Panther13]

 The mechanics brought this up, and said that they'd "adjust it" then later said it was fine. It's off of what the PO said was an '81 Nighthawk 750, but I think it may have been off of an 82 seeing as how they didn't make nighthawks until 82.

 Also, of note, I finally hit reserve today. 81 miles! Before it was about 55 to the tank. Amazing improvement, but I still need to check fuel levels/needle position and maybe even go down a jet size (or toss on some pods and try to play around with them). I know I said that I'd get those fuel levels today...but I was rather busy. Maybe tomorrow...heh.

[King_Panther13]

 About to leave and visit my uncle now....but, quick question, will jets like these http://www.siriusconinc.com/pro-detail.php?pid=&product_id=1953 fit in my cb500 carbs? They look like they would, and I would buy them just to see, but they don't list CB500 on them....so I just need to make sure.

[King_Panther13]

 Ok, fuel levels seem fine. My uncle says that maybe the valves are causing the idle hangup (which slowly but surely has worked its way back into my list of problems) and that once I get the clearance numbers, he'll be able to adjust them easily for me. I pulled the numbers off of a guide linked here, so we'll be good to go for that. As far as the bike still running rich, I'm believing more and more it's because the stock jets for the 550k engine were 90's....I know that it must be different with different carbs, but it seems to be making too much sense. I'll be trying to buy some jets from http://www.siriusconinc.com/pro-detail.php?pid=&product_id=1953 next, and maybe sticking on some pods to lean the bike out.

[King_Panther13]

 Ok, I took it to my all-knowing uncle again (he's been tinkering with metric bikes ever since the 60's) and we checked the valves. All were around .002 or .003 inches, one being .004. None less. So we deduced that the valves were not a problem, although a few O-Rings were leaking and need to be replaced. He went into the ignition, and said that the timing wasn't done properly and the timing advancer (or something like that, I don't remember the exact word) was dry as a bone, and wasn't working properly. He greased it, retimed it, and then lo and behold the bike no longer had low end acceleration problems, and I haven't had an idle hang-up ever since (though he still thinks it's because of one of the carburetor arms that the idle sometimes hangs up).

 Then I decided to drive to Advanced Auto Parts to pull the plugs (for some reason, he didn't have the right plug socket for my plugs) and check them. On the drive up, I noticed that the bike started "coughing" around 5k instead of 6k RPMS. Uh oh. I changed the jets about 200-300 miles ago, and the plugs were already all black with a tiny bit of brown...except for the one on cylinder four, which was all black except for the center, which was white. I cleaned them all out with carb cleaner and a brush, put them back in, and had a small bit of trouble firing up the bike. With the use of the choke, I got it to start up. After about a minute of idling, it stalled, and the electric starter wouldn't start it back up. I made sure that I didn't have the kill switch on, and played with it a bit. No dice. I tried the kick start, and it started on the first kick. Weird. I let it idle for a bit, and drove off.....to discover that the "coughing" now starts around 4k RPMs, and the bike will only stutter up to about 5k or so. Ugh.

 I'm giving it a rest for today, but I'm doing some riding tomorrow. Maybe some more problems will show up...I keep pestering the mechanics about the horrible job they did, and they keep telling me that I need to lower the needles. Maybe that will be the next step I take, hopefully that'll make things better. I don't know what could be doing this...

 Thoughts? Opinions? In other words...help!