Topic: High altitude 73 CB500 daily driver ( 5/20/17 update )

[riverfever]

That's a heck of a ride Dan! Did you guys come south through Larkspur? Today I heard that the bridge at Trumbull is now under water so that road is shut down. Glad you're seeing improvements with your bike.

[Desert Dan]

We took 83 all the way down to the springs and 105 back north but I didn't see any flooding along the route. I was thinking you brett_bike and I could meet up with the 500's in Sedalia next weekend to compare notes and see how each others bikes run.
If you're interested I saw a 550 engine for sale on Craigslist up in Aspen incase you're overly vexed by your low compression numbers.

[Desert Dan]

After the 200 mile ride the other day my back was killing me from wearing a backpack loaded down full of riding gear, so today I got creative and fit the bike with some saddle bags. The saddle bags are just canvas pack bags that we used to use on our pack horse but I found they fit the bike really well. I made up some brackets that bolt to the grab bar to keep the bags off of the exhaust and to lash the bags to. Over all Im pretty pleased and these will work until I decide to spring for some actual leather saddle bags.

[HondaMan]

The "mixture issue": for many years, i have 'tuned' my 750 to the altitude where I was with the octane in the tank. It works very well. As you go higher, you want LESS octane, as it burns faster than higher octanes. In the oversquare 500/550/400F/650F engine, this is the best way to match up without changing the jets. In the longer-stroke 750 and 350F, it is slightly less sensitive, but if I have premium in the tank and climb, for instance, Mt. Evans (14,260 ft), I may lose the #2 and #3 plugs if I don't keep the revs on tap more than normal. The center cylinders run slightly hotter than the outers, so they don't appreciate the richer mix.

The plug caps: yours should be 7500 ohms, if OEM. They should not be more than 8300 ohms, and on one coil not more than 500 ohms different between them, or one side will get weaker spark. Higher ohms makes for longer duration (and cleaner plugs), so a quick test of what you have might be to get some of the DR7EA or XR22ES-U plugs in addition to the plug caps you have now: these add 2000 ohms to the circuit(s) and stretch the spark dwell a bit. BUT...if your caps are weak, with the contacts burning inside where they contact the resistor, the resistor plugs may make the spark jump to the block instead. With new 5000 ohm caps, this won't happen.

HP loss of these carb'd engines is about -1% of total output per 1000 feet altitude, all else being equal. So, by 8000 feet, the 500 is typically running about 32-ish HP at 7000 RPM. Higher-compression pistons (if they are NOT forged pistons) will reduce this effect by about 50%, as the efficiency stays higher. This is why the "Gentleman's Express" version of these bikes (590cc, made with 750 pistons) has been popular for many years. Way back when, Action Fours used to make some 1mm oversize 10.5:1 pistons for these bikes, and if the owner stayed with the stock cam this made for a mighty torquey 500, indeed! Then, the rear sprockets would lose a few teeth to make them smoother 80 MPH tourers, too. But, those who decided they wanted a "big cam" to go with the pistons discovered the efficiency was very low until 7000 RPM, so the bikes became a nuisance to ride. (Something to ponder...).

The 4-1 pipe will cause a very small "suction draw" in a minor RPM range where the only power "boost" will be felt. for the rest of the RPM range, it will not have any effect, simply because the collector pipe is WAY too short to extend the header-suction moment. In order to actually work, this pipe would have to be about 8" longer than the rear wheel...

[riverfever]

Love the way those saddle bags look Dan. Bikes looking great.

[Desert Dan]

The "mixture issue": for many years, i have 'tuned' my 750 to the altitude where I was with the octane in the tank. It works very well. As you go higher, you want LESS octane, as it burns faster than higher octanes. In the oversquare 500/550/400F/650F engine, this is the best way to match up without changing the jets. In the longer-stroke 750 and 350F, it is slightly less sensitive, but if I have premium in the tank and climb, for instance, Mt. Evans (14,260 ft), I may lose the #2 and #3 plugs if I don't keep the revs on tap more than normal. The center cylinders run slightly hotter than the outers, so they don't appreciate the richer mix.

The plug caps: yours should be 7500 ohms, if OEM. They should not be more than 8300 ohms, and on one coil not more than 500 ohms different between them, or one side will get weaker spark. Higher ohms makes for longer duration (and cleaner plugs), so a quick test of what you have might be to get some of the DR7EA or XR22ES-U plugs in addition to the plug caps you have now: these add 2000 ohms to the circuit(s) and stretch the spark dwell a bit. BUT...if your caps are weak, with the contacts burning inside where they contact the resistor, the resistor plugs may make the spark jump to the block instead. With new 5000 ohm caps, this won't happen.

    The mixture issue is pretty much a thing of the past now, Ive got it so that the plugs are turning brown at altitude and at lower elevations, it was allot of guess and check work but everything seems to be copacetic carb wise.
   
    The spark plug boots Im running now are the stock Honda ones, and when I first started on the rebuild I checked them to make sure they all had the same # of ohms I just can't recall what that #  was. Ill be installing dyna 5ohm coils pretty soon as I hear they recharge faster between sparks than the stock Honda coils and I was just checking to see what spark plug boots work best with those coils.
 
    Im in no hurry to install a 4into1 at this point in time as they are a pretty significant chunk of change and the engine has been breathing allot easier since I drilled more holes in to the baffles of my jardine 4into2's.

    If you need I can swing by sometime with a bucket and help you bail out your garage, we've been fortunate these last couple of days with high temps and low humidity which should help everything dry out a bit.

[/quote]

Love the way those saddle bags look Dan. Bikes looking great.

Thanks Chris, I was just cleaning up the old barn and I saw them laying under a tarp on a saddle and that's when I had the ah ha moment. So what do you think of meeting up for a ride and some Sohc talk sometime next weekend?

[SOHC4 Cafe Racer Fan]

Interesting short piece on the effects of altitude on making power:

http://www.cycleworld.com/2015/06/25/technical-update-effect-of-altitude-on-engine-performance-project-156-at-pikes-peak-hill-climb-race/?src=SOC&dom=fb

[Desert Dan]

It took a while but I mustered up the energy to rebuild the forks this weekend, it was allot easier than I thought it would be, the hardest part of the process was polishing the fork lowers. I would have taken more pictures of the process but I was on a roll and everything was going so smoothly.

Forks off, (I need to replace the yellowed turn signal lens)

Before

After

Polished fork lowers


After that my new 5ohm dyna coils showed up so I soldered up the wires threw together the plug wires and viola. I have to say the coils were pricey but worth every penny, the engine seems to be much more responsive, pulls hills better, and seem smoother all the way around. I had the engine extremely well tuned before the new coils and after installing the dynas it is now running even better. Currently Im running the stock Honda resistor plug boots and it's running great, Im wondering if the stock plug boots have to much resistance and will harm the dyna coils, or if replacing the Honda plug boots with the lower ohm'ed NGK boots will improve the performance of the ignition system.

[HondaMan]

Higher resistance in the plug caps is actually desirable. The Honda caps were 7500 ohms new (considered burned out at 8500 ohms), but modern days have left us with only 5000 ohm caps instead. These will eventually burn the coils out FASTER, as they draw higher currents during the spark (but, we're talkin' YEARS, here...). I have had good luck with the "R" series sparkplugs in this regard, using plugs like XR24ES-U (CB750) or XR22ES-U (CB500/550) with getting a longer-duration spark. This causes a longer push down the bore, and enhances the midrange torque in the process.

[Desert Dan]

Higher resistance in the plug caps is actually desirable. The Honda caps were 7500 ohms new (considered burned out at 8500 ohms), but modern days have left us with only 5000 ohm caps instead. These will eventually burn the coils out FASTER, as they draw higher currents during the spark (but, we're talkin' YEARS, here...). I have had good luck with the "R" series sparkplugs in this regard, using plugs like XR24ES-U (CB750) or XR22ES-U (CB500/550) with getting a longer-duration spark. This causes a longer push down the bore, and enhances the midrange torque in the process.

  I couldn't find anything on the Denso XR22ES-U on the internet, I don't believe ND makes them anymore. I went through ND's spark plug sizing chart http://densoautoparts.com/spark-plug-part-numbering and what I found is that the X22ES-U is just about the same. According to the chart X is the thread pitch and socket size which is 12x18, 22 is the heat range ES stands for a 19mm reach with a stainless steal gasket and -U is for the U groove in the spark plug diode. I think these may work, but the denso plugs themselves are still hard to track down.

[Desert Dan]

Quick question on an oil seal. Im on a crusade to stop any and all oil leaks coming from my engine and Im in the process of replacing all the oil seals under the left clutch actuator cover, Im wondering if the oil seal behind the drive sprocket is replaceable without splitting the engine case. Ive so far replaced the pushrod seal and the shift shaft seal but Im hesitant to replace the drive sprocket seal because it is quite large and kind of looks like the oil seal behind the points plate which is a seal that can only be replaced when the engine is split. If it can only be replaced by splitting the engine I wont worry about it as I currently don't suspect it of leaking, on the other hand since I have everything off and have the new seal on hand I would like to replace it for piece of mind.
The seal in question

[riverfever]

Dan I did mine without splitting cases. It was a little tricky to get out but various picks finally did it.

[Desert Dan]

^Thanks for the info Chris, I left well enough alone with mine as it isn't leaking but it's good to know it's an easy replacement.^
    So over the past thousand miles Ive developed a new problem, the engine has started to burn oil. Its not a huge amount and it's very sporadic when it does but I can see smoke coming from the tailpipes. Im leaning toward valve seals on this one but its a very strange the way its burning oil.
    On the first start of the day the 1/2 pipe blows out clouds of white smoke for about 5 min then stops, the engine will then run fine for about 100 miles not burning any oil then after 100 miles the 2/3 tailpipe begins to blow small amounts of white smoke at idle and a steady stream of smoke on acceleration. When the 2/3 pipe starts blowing smoke I can feel the engine lose a little power and start to run hotter and rougher and it will sound louder, but sometimes if I stop and turn off the engine for a moment it will magically stop smoking and run smooth again.
    For instance yesterday I rode the bike up to Fort Collins where I do my flight training which is about 100 miles one way and it ran great all the way up there not burning any oil, I stopped for 2 hours while I did some flying then on the way home it ran rough and was smoking out of the 2/3 exhaust. I stopped after 15 miles to let it cool and see if it would behave itself but it persisted in running rough almost all the way home. When I was about 15 miles out from my house I stopped to throw on my jacket and when I turned the bike back on it was running nice and smooth again, I had only turned it off for maybe a minute  .    When I first noticed it beginning to smoke I first checked and re-adjusted the valve lash and reset the timing, I also checked compression and got just about 165 on all four cylinders plus or minus 1 or 2psi. At this point I think it's valve seals maybe a couple didn't seat right or maybe some of the guides are worn and are damaging the seals. When I check the spark plugs all 4 look decent with 2 and 3 being a little iffy but none caked in oil deposits 1/4 look really good and so do the tops of their pistons while the tops of 2/3 look a bit carbon fouled.
Number 1 spark plug

Number 2 spark plug

Number 3 spark plug

Number 4 spark plug

    My game plan at this point is sometime in the near future Ill pop the valve cover off and replace the valve guide seals on cylinders 2 and 3 since they are more suspect then 1 and 4, and while Im in there I will also re-torque the head. Beyond that the only thing I can think of is it's a problem with the oil rings on the 2 and 3 pistons, the oil consumption isn't excessive maybe a 1/16nth of a quart every 200 miles. If any one has any ideas as to the oil burning issue Im all ears at this point.

[calj737]

You have said white smoke. Oil is blue smoke. How much is needing to be added? Those plugs don't indicate to me that oil is being burned. Sounds more like its a stuck float over filling the fuel and those carbs are drowning.

[Desert Dan]

After 200 miles the oil level dropped maybe an 8th of an inch from the full mark on the dipstick. I have been having a stuck float issue on the #2 carb but the smoke comes from the 3 and 4 muffler on my 4into2 exhaust. I used the clear tube method to set all my float heights and the over flow tubes are all clear and working properly. I did think it was strange none of the plugs showed oil consumption.

[HondaMan]

When these bikes burn oil, it also usually shows up at the header pipes on the front of the engine as a light greasy smear, as they don't seal 100% like modern designs.
More likely: the float level(s) are sticking, like CalJ suggests. This makes the pipe(s) slowly load up with unburned fuel until enough of it lights off to either smoke (white), or lightly pop (like a real mild backfire).

I think you already have new seals on those valves?

[Desert Dan]

I picked up a rack of 550 carbs today from the motorcycle salvage yard for 30 bucks, they're pretty nasty but full of good parts and good floats, Ill use one of the new salvaged floats on my #2 carb to fix it's sticking float issue and while Im at it Ill recheck the float levels of the other 3 carbs. When I was on my ride yesterday and it was running rough there was no sign of fuel coming out the overflow tubes when I was idling at stop lights. I did a pretty thorough job of cleaning the engine the other day after replacing some leaky oil seals and I saw no evidence of oil on the headers. The head does have new vesrah valve guide seals installed back when you ported the head, before all of this summer's rain flooded your garage. When the bike is running correctly it runs extremely well and when its acting up it still runs pretty well. It very well could be a float issue, when the bike is running well it's gas millage is in the high 40's low 50's and when its running rough it drops down in to the low 40's.

[Jerry Rxman Griffin aka MuthaF'er]

Sticky float = suspect pin.

[riverfever]

Jerry...just out of ignorance...what are you talking about here? The brass pin that the float pivots on?

[Desert Dan]

All the float pins in the spare rack of carbs I bought were suspect, I had to cut a few of them to get the floats out. The float pins in my good set of carbs are in good order I can easily remove them and the floats actuate freely, my #2 float is suspect because the brass tab that limits how far it can drop in the bowl is missing and I think it's causing the float to get hung up when the fuel gets low in the bowl.

[Desert Dan]

    Long time no post everyone! Ive been pretty busy since the last time I posted with school starting back up, but I have still been riding and working on the good old 500. Not long after my last post I put in a "new" float and float pin in to the #2 carb from the spare rack of carbs I picked up at the junkyard and for the last 1,600 miles I have not had an issue with it over flowing, that is untill this afternoon. I drove the bike to school this morning with no issue but later in the day when I rode it out to the airport it was running rough and bogging down in the mid rpm range, sure enough when I parked it the #2 carb was pissing fuel out of the over flow again. I plan on putting a new float valve in there as soon as possible to fix this recurring issue as I enjoy riding the 500 far too much to let it sit around unused.

Here is a picture of where I had the float level set in #2 and the other 3 carbs, which was working well for the last 1,600 miles.

   
Last time I updated the 500's progress we collectively thought that the smoke was unburnt fuel from improper float heights, but it has continued to smoke and burn oil since I fixed the float issue. Im burning about 1qt of oil every 1000 miles. From what I can tell it only burns oil once the engine has gotten good and hot and the oil has gotten thinner, usually this is about 80 miles of highway riding or 30 minutes of city traffic riding. There is no smoke coming out of the exhaust while the engine and oil are still cool but once everything has heated up i get a steady stream of smoke from both sides of the 4 into 2 exhaust and from the valve cover vent tube. Im 95% sure that cylinders 2 and 3 are the culprits because their pistons are oily and black while pistons 1 and 4 are a dark brown color. When the engine begins burning oil I don't feel any loss in power and it is not burning enough oil to fowl the plugs or leave much in the way of residue on the plugs, which I find very odd. My best guess is that for some reason the oil rings on 2 and 3 never fully broke in and oil is being burnt off the cylinder walls, but the last time I did a compression check I got the same reading +- 1psi on all four cylinders ( I believe it was either 165psi or 160psi on all 4, I don't remember which.)
    Besides the oil burning issue and the #2 carb acting up on me again everything is going great on the 500, Ive put 5,200 miles on it since I finished the engine rebuild in March. One of the best things about riding the 500 is all of my riding buddies get floored when every one at gas stations and restaurants come up to talk about and admire the little CB and ignore the big, new, and chromed out V-twins that my buddies ride.

And a few humble pictures of the CB500 in it's natural environment.

[calj737]

My money is on the valve seals as the cause of oil entering the cylinders.

[Desert Dan]

My money is on the valve seals as the cause of oil entering the cylinders.

I'd be pretty happy if it were just valve seals, Ive got a set of new Vesrah valve seals sitting on my work bench at home. I could slap those puppies in the bike over a weekend.

[HondaMan]

Maybe check for a cracked or chipped valve guide? Or, check to see if the intake valve in the cylinder(s) of question now have excess clearance on their stems (i.e., if you pull the head off, try the 'wiggle test' of the valve with it lifted about 6mm off the seat). If the [new] engine (head) was last run on normal gas and now has suffered the ethanol solvent having washed out the valve guides, the once burned-on oil film may have washed away, leaving too much clearance on the valve stems. I see this happen with the 750 heads pretty often. Since the guides were not changed in the head (just the valves and head cleaned, new seats ground on both), this clearance may have increased. If so, you will have better luck sealing the guides with the Buna valve seals than with the Viton type: the Viton ones are orange color and the Buna are charcoal. Viton is stiffer.

[Desert Dan]

Worn valve guides were another suspicion of mine, especially since the head received new valve seals when I sent it off to you. Im not overly concerned with the oil burning issue at the moment because the bike runs the same whether it's burning oil or not, and it has yet to foul a plug or have any detrimental side effects. Ill try those Buna valve seals you describe, any idea where I can order such a part? At the current moment Im off at school so I don't have a garage to do major repairs in so Im just going to fix the leaking #2 carb and continue to feed it's oil burning habit, as I plan to keep riding the 500 up to the very last minute of the riding season. Worst case scenario in my mind is once theres snow on the ground and riding season is solidly over I can pull the head and and see if new guides are in order, and if Im in that deep there might be room for improvement as I have been eye balling that cruzin image big bore kit for a while.