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

[HondaMan]

Mark your knowledge of the intricacies of the Honda motorcycle astound me, I re-jetted the carbs with the 92's and the flat spot seems to have disappeared. I didn't get a full test ride in as it rained all day today up in the mountains but I did take the bike up and down the driveway and I see any signs of the flat spot.
   Since it rained all day I was unable to go down to Denver to check  out the vintage bike "show", but I did get the new jets in from 4into1. I spent most of the afternoon re-jetting the carbs, putting on the new air box boots, and fixing a small fuel leak. The fuel leak was caused by a pooched o-ring on the 1-4 fuel T and would drip 1-2 drops of fuel a minute. I also took Mark's expert advice and ditched the unifoam air filter and made my own. I simply bought a circular paper Fram air filter and cut it down to size to fit in the unifoam's plastic box, altogether the modification cost me six dollars and I have enough filter element left over to replace the current filter once it gets used up. Hopefully there will be an hour or two of sunlight tomorrow to go on a proper test ride and see how today's tune up worked.

Great idea for the filter!

[Desert Dan]

Since Ive been out of school for summer I have had plenty of time to work on the 500, I did a quick 6 mile test ride in between rain showers and Im really liking the 92 jets. In just 6 miles the spark plugs started turning a lovely tan color as the carbon residue from running rich is being burnt off and the black carbon deposits on top of the pistons is burning off revealing the gold colored powder coating I had done to them.
  After the test ride I received a package containing the used 550 ignition and advance mechanism so I used the rest of the rainy day fixing my ignition timing. I tried several combinations of springs on both the 500 advance and 550 advance but the 2/3 timing was still way off so I broke down both advances and rebuilt the 500 mechanism using parts from both. The 500 advance had remnants of old fossilized grease inside of it so after a thorough cleaning I gave everything a thorough greasing. I ended up using an extra shim from the 550 advance along with a shortened spring from the 550 and a shortened spring from the 500.
Here is the 500 advance disassembled

And here is the 550 advance disassembled

A comparison of both advance bases with the 550 on bottom

There were several differences between the 500 and 550 advance mechanisms, the 550 had larger swing arms, larger springs, a larger cam with a flared base, and it used 2 large brass shims per a swing arm. The 550 has a tab on the spindle to help locate the points cam, it also uses 3 small shims per a swing arm 1 on bottom 2 on top, and it is over all a bit smaller than the 550 mechanism.
Both mechanisms worked on the bike but I decided to use the 500 mechanism because i figure it's better to stay with the evil I know verses the evil I don't. There was what looked like a small bit of welding slag on the 500 mechanism base that I think contributed to the timing issues, it can be seen just off the spindle at the 4 o'clock position in the last picture before I filed it off. Now the timing has moved towards the 1/4 points bringing 2/3 just back in to correct timing. I believe if I added a plastic shim to the very base of the mechanism where it contacts the crank like Hondaman describes, it would bring the timing even closer to 1 and 4.

[riverfever]

Are you up in the Denver area Dan? Nice looking bike. I'm down closer to Colorado Springs but up high way 24 about 20 miles into the mountains and had a heck of a time getting my bike tuned for 9000' last summer.

[HondaMan]

Are you up in the Denver area Dan? Nice looking bike. I'm down closer to Colorado Springs but up high way 24 about 20 miles into the mountains and had a heck of a time getting my bike tuned for 9000' last summer.

Yeah...above 7000 feet, you might wish to advance the timing a little bit, overall, or at the very least use the lowest octane you can find. On the 750, I grind the "stop ears" back a little bit (or bend them, if it is a Hitachi advancer, they are thinner metal) to let it have another 2-4 degrees top end advance. That helps "up there". When you come "down here" you can then just switch to more octane to keep it happy. Some have done this, but used little rubber O-rings on the "Stop ears" to back off the top-end timing a little when going to places like Kansas or Black Hills.

[riverfever]

Perhaps a silly question but, what did you use to cut that filter and, how did you ensure that everything was clean afterwards and nothing got sucked into the motor?

[Desert Dan]

So Im still chasing my tail on these timing issues, I spent all day trying to even up 2/3 so that the plate isn't maxed out on adjustment. I left off the other day with 1/4 being properly adjusted with the plate being a bit left of center on it's range of travel while 2&3 were barely on their firing mark with it's plate being maxed out on adjustment. I made a brass shim to go underneath the advance mechanism but that didn't help in moving the timing at all, so I tried bending the ears that stop the swing arms to limit the advance to get a little more advance out of the mechanism. As it turns out this plate was not the type you can bend, I bent the ears a slight amount then when I went to test how far they advance s%#t hit the fan. I must have cracked the ears instead of bending them because the swing arms snapped the ears off right before snapping themselves off of the advance plate. The whole mechanism is now fubar'ed and whats worse when the mechanism self destructed it pooched the dowel hole on the end of the crank  . Im kicking myself for making such a critical error and am currently shell shocked. I put the 550 advance back together and slapped it in there, now the timing is way off. 1/4 is now too advanced and I have to max out it's adjustment to get it near the firing mark while 2/3 is still retarded and maxed out to be near it's firing mark. I killed my budget again and ordered a used 500 advance off of Ebay and Im going to try and repair the crank's locating hole with some lead solder and clean it up a bit.

[HondaMan]

So Im still chasing my tail on these timing issues, I spent all day trying to even up 2/3 so that the plate isn't maxed out on adjustment. I left off the other day with 1/4 being properly adjusted with the plate being a bit left of center on it's range of travel while 2&3 were barely on their firing mark with it's plate being maxed out on adjustment. I made a brass shim to go underneath the advance mechanism but that didn't help in moving the timing at all, so I tried bending the ears that stop the swing arms to limit the advance to get a little more advance out of the mechanism. As it turns out this plate was not the type you can bend, I bent the ears a slight amount then when I went to test how far they advance s%#t hit the fan. I must have cracked the ears instead of bending them because the swing arms snapped the ears off right before snapping themselves off of the advance plate. The whole mechanism is now fubar'ed and whats worse when the mechanism self destructed it pooched the dowel hole on the end of the crank  . Im kicking myself for making such a critical error and am currently shell shocked. I put the 550 advance back together and slapped it in there, now the timing is way off. 1/4 is now too advanced and I have to max out it's adjustment to get it near the firing mark while 2/3 is still retarded and maxed out to be near it's firing mark. I killed my budget again and ordered a used 500 advance off of Ebay and Im going to try and repair the crank's locating hole with some lead solder and clean it up a bit.

Ouch! And just in time for the foot of snow that is just starting. My basement just flooded, am taking a short break from pushing water around for a while...

I suspect the timing issues you're fighting are due more to the Daiichi points than the spark advancers. When you get the new one, maybe try this: set the timing to be on the "T" mark for the 1-4 side with a gap of .012", then stop the engine and slightly bend the ground arm of the points set away from the moving one for a .014" gap. Then see if you can get the 2-3 to time up a little closer.

The geometry of the Daiichi points is simply incorrect. Most of the ones I have installed are only working because the bike(s) also has my transistor Ignition aboard, which makes it insensitive to gap sizes (you can run as little as .008" or as much as .016" with this box connected).

There are more than a few of the crankshafts out there with brass bushings in those dowel holes, too...
 

[Desert Dan]

So Im still chasing my tail on these timing issues, I spent all day trying to even up 2/3 so that the plate isn't maxed out on adjustment. I left off the other day with 1/4 being properly adjusted with the plate being a bit left of center on it's range of travel while 2&3 were barely on their firing mark with it's plate being maxed out on adjustment. I made a brass shim to go underneath the advance mechanism but that didn't help in moving the timing at all, so I tried bending the ears that stop the swing arms to limit the advance to get a little more advance out of the mechanism. As it turns out this plate was not the type you can bend, I bent the ears a slight amount then when I went to test how far they advance s%#t hit the fan. I must have cracked the ears instead of bending them because the swing arms snapped the ears off right before snapping themselves off of the advance plate. The whole mechanism is now fubar'ed and whats worse when the mechanism self destructed it pooched the dowel hole on the end of the crank  . Im kicking myself for making such a critical error and am currently shell shocked. I put the 550 advance back together and slapped it in there, now the timing is way off. 1/4 is now too advanced and I have to max out it's adjustment to get it near the firing mark while 2/3 is still retarded and maxed out to be near it's firing mark. I killed my budget again and ordered a used 500 advance off of Ebay and Im going to try and repair the crank's locating hole with some lead solder and clean it up a bit.

Ouch! And just in time for the foot of snow that is just starting. My basement just flooded, am taking a short break from pushing water around for a while...

I suspect the timing issues you're fighting are due more to the Daiichi points than the spark advancers. When you get the new one, maybe try this: set the timing to be on the "T" mark for the 1-4 side with a gap of .012", then stop the engine and slightly bend the ground arm of the points set away from the moving one for a .014" gap. Then see if you can get the 2-3 to time up a little closer.

The geometry of the Daiichi points is simply incorrect. Most of the ones I have installed are only working because the bike(s) also has my transistor Ignition aboard, which makes it insensitive to gap sizes (you can run as little as .008" or as much as .016" with this box connected).

There are more than a few of the crankshafts out there with brass bushings in those dowel holes, too...

Ill give that a try tomorrow once I get done shoveling all of this snow. The used 550 advance and ignition plate came with a 1/4 daiichi and a 2/3 of a different make, so I substituted it's 2/3 for the 2/3 daiitchi I was using as it was such a horrible fit. How would I go about getting a brass bushing put in to the end of the crank, would the whole engine have to be disassembled and taken to a machinist or would it be a process I could do myself without any special machinery?

[Desert Dan]

Ok I have had success with the timing, I spent all day monkeying with it and I have got it set correctly with extra adjustment room if need be. I started by measuring the runout of the advance mechanism spindle (points cam not installed) and I got these measurements (no shim behind advance .016in) (shim behind the advance .012in) I thought the run out was causing my timing issues so I spent a good while strategically sanding down sections of the brass shim I made until I got this measurement with the shim installed .006in. I reassembled everything and what I found was truing the mechanism made the timing worse so I removed the shim and viola timing came back to good adjustable levels. The next problem I had was the 550 advance did not have enough totall advance, so I ground down the stopper ears until I could achieve the proper full advance. Also I inspected the locating hole on the crank with a clear head and the damage is minimal to negligible as only the very outside of the hole got wallowed a bit, there is no play or wiggle when a pin is inserted in it. Now I have the timing set slightly advanced at idle with a little bit extra advance when fully advanced to help with the altitude. I also found a interesting quirk while tuning, since I am still using the stock 40 idle jets the bike runs rich at idle making it so when I idle the bike for long periods of time or several sessions of idling for a few minutes the air intake plenum behind the carbs fills up with fuel and overtime drains out the the vent tube with the foam filter on the end. I was pretty surprised when I found a small puddle of gas under the bike after it had not been run for a few hours with the fuel valve shut off.
Here is the brass shim I had made to "fix" the timing, and it's plastic template

And a few photos of my modified air filter if anyone is interested

[Desert Dan]

  So not much in the way of progress to report right now, Ive been riding the 500 every chance I can get which is a bit sporadic considering the daily rain showers Colorado has been getting these last couple of weeks. I reached the 500 mile ring break in point so Im now able to give the bike the beans and see what it can do, which is not as much as I was hoping. It appears I have more tuning to do to ring out every last drop of performance I can. I attempted to do the ton on a long straight section of highway but the bike reaches it's limit at 90mph which is faster than Ill need it to go but I'd like to hit 100mph once just to put the notch in my belt. Im going to order some smaller idle jets because the plugs and cylinders get pretty wet and carbon fouled at this altitude when I idle for any length of time, and I have a theory that even at speed a little fuel goes through the slow jets contributing to the richness of the mixture because the mains are now much smaller than stock.
  Ive also been on the look out for a new exhaust as the current 4into2 sounds just a little too choperish and doesn't make that smooth four cylinder sound that I want. Ideally I'de like to find a stock 4into4 and I was a day late on the one RiverFever had for sale, but the cost of a stock exhaust is somewhat prohibitive so Ive been knocking around the idea of getting a 4into1. Im hesitant to get one as most of the 4int1's I see for sale require them to be removed to change the oil filter which isn't the end of the world, but what Im most worried about is that it might contact the stock fender when braking or going over bumps. I like the look and the price of the lossa engineering exhaust as the stainless steal one comes in at $500, but I'd like to see what other people have to say about it.
   I also did another tune up today (valve lash and carb sync) and discovered a few problems. Firstly I installed Honda 5.5mm fuel line (which is excellent much better than 1/4in or clear plastic fuel line) while at the same time eliminating the in line fuel filters I had been using. The inline filters were causing just enough of a restriction to keep my carb bowls from over filling with the stock 22mm float height and the stronger sprung aftermarket needle valves. Now without the restriction of the filters my carbs piss fuel out of the drain tubes while at idle, so I need to pull the rack of carbs and find a float height that will keep the carbs happy. Secondly sometimes at idle I would here a momentary popping noise that I thought was just excess pressure coming out the vent tube, it turned out to be my #1 spark plug wire shorting to ground occasionally while idling. I attempted a shade tree fix with electrical tape and bicycle inner tube but that only worsened the problem. It's an easy enough fix and more than likely caused by the brass pin I used to replace the old wires with being pushed through the plug wire shielding, Ill just have to redo that plug wire when I get around to setting the float heights.
  Besides those momentary hick ups the 500 is running beautifully and the top end is bone dry and doesn't leak a drop of oil.

[riverfever]

Thanks for posting more pics of that filter setup Dan. I'll be trying that as well. Sorry we couldn't hook up on the exhaust. Would have been perfect for both of us. I rarely see anyone else wanting to run the stock fender with a 4 to 1 and the few pictures i have seen look just as tight as mine and I find it very hard to believe there's no contact unless there's just no travel in the forks. My new tires will be here later this week and once I get them mounted I'll start looking at tastefully modifying the fender so I can run it and still have things be safe. I think it looks good and, as you said, we get those daily showers here so it would be nice to have the coverage. I'll let you know how things work out.

[Desert Dan]

Thanks for posting more pics of that filter setup Dan. I'll be trying that as well. Sorry we couldn't hook up on the exhaust. Would have been perfect for both of us. I rarely see anyone else wanting to run the stock fender with a 4 to 1 and the few pictures i have seen look just as tight as mine and I find it very hard to believe there's no contact unless there's just no travel in the forks. My new tires will be here later this week and once I get them mounted I'll start looking at tastefully modifying the fender so I can run it and still have things be safe. I think it looks good and, as you said, we get those daily showers here so it would be nice to have the coverage. I'll let you know how things work out.

I took some quick shots of the clearance between my stock fender and my current headers if you want to compare and contrast with your 4into1. I have no idea if they're cut down stock headers or not but they clear the oil filter housing and they don't hit the fender. I imagine since many 4into1's cover the oil filter housing they must stick out a good deal further narrowing the gap with the fender.

[HondaMan]

One of the things that is real important for that hi-RPM work is: perfect spark. If you can, consider getting at least a set of the coils from PartsNmore instead of trying to reach 100 MPH with 'repaired' coils and arcing wires.

Then maybe consider a Transistor Ignition, too: it will improve the spark everywhere. That's why I started making them again.

[Desert Dan]

One of the things that is real important for that hi-RPM work is: perfect spark. If you can, consider getting at least a set of the coils from PartsNmore instead of trying to reach 100 MPH with 'repaired' coils and arcing wires.

Then maybe consider a Transistor Ignition, too: it will improve the spark everywhere. That's why I started making them again.

   I have been reading all sorts of articles of transistor ignitions I even downloaded a wiring diagram, parts list, and instructions to build a single points unit to try out on one of my Volkswagens. Your transistorized ignition has been on my wish list for some time now and as soon as my budget allows I plan on ordering one from you, from what Ive read on transistorized ignitions and from reviews of your ignition from other SOHC4 members there are no downside to using one which makes it all the more appealing.
   As of right now Im fairly confident I can repair the arcing #1 wire as the other 3 wires I installed in the coils are working fine and aren't arcing. When I first tested the coils I made a spark tester with a 7mm gap and all 4 wires were capable of jumping the gap with a hot blue spark. If I can't satisfactorily replace the #1 wire Ill bite the bullet and buy a set of new coils. The attempt to reach 100mph was done before I knew about #1 arcing, and I haven't ridden the bike since I discovered the issue. As far as I can tell the arcing only happens below 1500rpm and at a rate of 1-2 arcs a minute, when the bike goes above 1500rpm there is no sign of arcing visible at the coil or in the form of misfires coming from #1. It's a strange issue but working on the bike wouldn't be nearly as fun without a little circumstance.

[Desert Dan]

   Small update, Ive fixed the sparking #1 plug wire, raised my floats to 25mm, and installed new #35 slow jets. The plug wire was an easy fix all I had to do was pull out the old wire and insert a new one, it took a pretty hardy pull but I now know that I can easily change plug wires on my modified coils. Im not sure if Im setting the float levels correctly as I don't have the proper float level tool, I just use a card stock ruler that comes in VW carb rebuild kits. I'm unable to use the clear tube method to check the bowl levels because my drain screws have been seized in the bowls since day one, I believe it may take drilling out the old screws and tapping the bowls to get new drain screws installed. With that said the carbs no longer piss fuel from the vent tubes when the gas is turned on so Im on the right track. I cant report any changes with the #35 slows yet as it's been too cold and rainy in Colorado to go on any sort of test ride, but Im getting pretty close with the jetting as the engine now likes full choke and a little throttle when starting cold, where as before 3/4 choke was the max without becoming too rich to start.

[riverfever]

So nice to have someone else tuning that's in a similar situation as I am. The weather we're having right now absolutely sucks. I'm still running 100/40 jets but that needle clip adjustment really helped things out so thanks for the suggestion. You have much more experience than I do. I took mine around the block today and it really struggles right off idle. I still need to change the filter out but I pulled some plugs when I returned. All 4 headers are very hot which is great b/c last year 4 was ice cold but plugs are really rich. I suspect I may need to make a slow jet change but I'd like to do a plug chop for the mains before that. Keep at it Dan. Maybe this summer if it stops snowing we can meet up for a ride.

[Desert Dan]

Once the weather warms up a ride is definitely in order, the route to and around Colorado springs is one of my favorites, great roads and scenery all over. From the jetting charts I've scene on the forums there's not much to be gained from changing the slow jets as they are only effective up to a 1/4 throttle, I replaced mine in order to get better plug reads and to rule them out as an issue. I found changing the clip position helped most with getting up to highway speed with out struggling, but the most improvement came from dropping down in jet size. 4into1.com has the aftermarket replacement jets, they cary keyster jets which aren't held in high esteem on here but I found the jets marketed as reproduction keihin jets made by keyster fit better than the same part# keyster jets and also are cheeper. I don't know why this is but the regular keyster jets are $2.50 a piece while the reproduction keihins are $1.95 a piece. The regular keysters fit loosely in the carb bowl springs while the reproductions fit nice and snugly. Also the reproduction keihin slow jets by keyster are a dead match for the original keihin slows.

[Jerry Rxman Griffin aka MuthaF'er]

I'm in Briargate Dan. Drop by.

[HondaMan]

Once the weather warms up a ride is definitely in order, the route to and around Colorado springs is one of my favorites, great roads and scenery all over. From the jetting charts I've scene on the forums there's not much to be gained from changing the slow jets as they are only effective up to a 1/4 throttle, I replaced mine in order to get better plug reads and to rule them out as an issue. I found changing the clip position helped most with getting up to highway speed with out struggling, but the most improvement came from dropping down in jet size. 4into1.com has the aftermarket replacement jets, they cary keyster jets which aren't held in high esteem on here but I found the jets marketed as reproduction keihin jets made by keyster fit better than the same part# keyster jets and also are cheeper. I don't know why this is but the regular keyster jets are $2.50 a piece while the reproduction keihins are $1.95 a piece. The regular keysters fit loosely in the carb bowl springs while the reproductions fit nice and snugly. Also the reproduction keihin slow jets by keyster are a dead match for the original keihin slows.

Yeah...when they fit loosely, or if the 'carb kit' for rebuilds came with the too-thin O-rings for the jets, they let too much fuel slip by. This really confuses things!

[Desert Dan]

I'm in Briargate Dan. Drop by.

That sounds good Jerry, I believe RiverFever is just outside of Woodland Park so I can swing by when I go for a ride with him and we could all do a cruise through the Colorado springs area.

Yeah...when they fit loosely, or if the 'carb kit' for rebuilds came with the too-thin O-rings for the jets, they let too much fuel slip by. This really confuses things!

I originally got the standard Keyster jets when I tried the 98 jets and I had to use my own O-rings on them as the supplied ones were to thin and the jets themselves were very loose in the retainer spring jet holders, I used the reproduction Keihins when I went down to 92's and they came with the correct size O-rings and fit extremely well in the retainer springs. It's strange that Keyster makes two types of the same jet yet the cheaper version works best.

[Desert Dan]

Well there was finally some sun in Colorado the last two days so I have been racking up the miles on the 500. I did 60 miles yesterday and 125 today, I am extremely pleased with the way the engine is behaving. Im getting really close with my jetting my idle jetting is spot on and so is my top end jetting I have to do a few plug chops on the mid range to see if I need to change clip positions then Ill toss in some new plugs to get down to the real fine tuning. My best MPG over the last two days was 43.2mpg which is a substantial increase from my old average of 37mpg when I was running the 40 pilot jets and the 22mm float heights. Just to recap as the bike sits right now the carbs are running 92 mains 35  pilots and the needle jets are set in the middle clip position. I have the timing set a few degrees more advanced than the standard timing mark and I modified the mechanism to advance a few more degrees at full advance. The bike is running beautifully right now and is nearly read to make some long distance trips around Colorado.

[riverfever]

That's great Dan. I was amazed this morning when I drove down the pass on the way to work and saw blue skies and sun. I got out a little bit yesterday and tuned a bit (I moved the clips up one more spot and it seemed to really help around 1/4 throttle). Congrats on the progress. It's a good feeling.

[HondaMan]

You got sunshine?
I'm still  pumping out my bike sheds and back yard.
...and drying out motorcycle parts, like engine cases, that got drowned...

[Desert Dan]

That's great Dan. I was amazed this morning when I drove down the pass on the way to work and saw blue skies and sun. I got out a little bit yesterday and tuned a bit (I moved the clips up one more spot and it seemed to really help around 1/4 throttle). Congrats on the progress. It's a good feeling.

Thanks Chris, I was amazed at the amount of sun there was these last two days. I got rained on a little monday, but today It was clear skies with all the clouds hanging out up north. Ive been batting around the idea of movie up a clip position, I may do it next time I have the rack of carbs off, my only concern is it would throw off my low and high range jetting forcing me to jet up.

[Desert Dan]

You got sunshine?
I'm still  pumping out my bike sheds and back yard.
...and drying out motorcycle parts, like engine cases, that got drowned...

Im sorry to hear that Mark, I have some friends from school who live a few blocks from you and most of their basement has flooded from all of the rain. I wouldn't say it was all sun shine, I merely followed the clear skies south east where the clouds weren't hanging out.