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

[SOHC4 Cafe Racer Fan]

Dan,

If possible, can you shoot some pictures of the intake ports.  I am just curious as to Mark's method of porting and how it compares to Mike Reick's -- not that one is better than the other -- but I wanted to see if they shape the ports similarly.

[Desert Dan]

Ill see what I can do, since the valves are installed its some what difficult to get a good picture of the port's shape.

[Desert Dan]

Ive been unable to find much in the way of info on the installation of the cam chain tensioner, from what I can visualize in my mind when installing the tensioner will keep the cylinders from sitting on the block until the head is bolted on forcing the tensioner assembly to "bow". If some one with experience rebuilding these engines could chime in and describe the installation process I would be extremely grateful. If all else fails Ill remove the pistons and try dry fitting everything to see how the tensioner is supposed to fit.

[goldarrow]

Recommend that you download HSM  here's the page you need

Make sure tensioner is seated properly when pushing the cylinder block down, drop oil pan and see from bottom.

[Desert Dan]

Recommend that you download HSM  here's the page you need
Make sure tensioner is seated properly when pushing the cylinder block down, drop oil pan and see from bottom.

Thanks, I actually had the HSM printed out and in my shop, I was just on a roll assembling everything and was working out of the clymers because everything was going together smoothly up to the point when I discovered the chain tensioner wouldn't seat properly with the head installed. I tried for a couple hours to get the tensioner installed without removing the freshly installed head and cylinders but there was no possible way to get it to seat properly in the case. I could get the adjuster nut and fastening bolt lined up fine but it wouldn't be seated or I could get it seated and there would be no way to get the adjuster bolt through the cylinder block hole. It just seems to me the distance from the slot in the case to the adjustment hole in the cylinder block is about .75 inches shorter than the distance the from the bottom of the tensioner to the adjuster bolt.

[Greggo]

Nice work on the bike so far, and nice van!  My dad's been working on VW's for about fifty years.

[HondaMan]

Not the best pix, I'm afraid!
Here they are, though. I think the lighting in the garage wasn't good enough for my camera to full-field focus that day.

This was after the face mill, but before the final finish. The tool marks can be removed with 80 grit emery paper if you do yours to completion, use your fingertips in there. The small sanding drums on Dremels will sorta work, but they don't follow the contours very well.

[Desert Dan]

Thanks Mark, I couldn't get very good pictures of the port job with the valves installed and like you suggested I went in and finished up the intake sides with 80 grit then polished smooth the exhaust sides followed up by a thorough acetone and q-tip cleaning.

Thanks Greggo, Ive been working on old air cooled VW's for about 8 years. The bus was my very first project that I built when I was 15 and has made transitioning to the Honda engine pretty easy.

[SOHC4 Cafe Racer Fan]

Pretty decent shots when you enlarge the image.  Thanks, Mark!

[Desert Dan]

Ok so I did the dry fit of the cylinder block and head with the tensioner installed, some how the little m6 tensioner bolt is able to withstand the pressure of the head and cylinders forcing the tensioner in to place. Installation was pretty easy without pistons and gaskets but it will make the actual process of assembly a bit more of a PITA.

When properly seated the tensioner keeps the cylinders about half an inch off the block

Initially there was barely enough of the studs sticking out to get the head bolts started but they slowly drew the cylinders down on to the case

Everything installed and the assembly lightly torqued down

Hopefully Ill have the replacement bits in this week and Ill have the engine together by next Monday.

[Desert Dan]

I have run in to another considerable road block, I got the replacement head gaskets and I assembled the top end with the cam chain adjuster installed correctly this time or so I believe but..... I cant get the adjuster bolt to spin clockwise or counter clockwise and something is binding in the engine making it difficult to turn over. The spark plugs aren't installed so its not compression keeping it from turning over and the cam chain itself is not binding up so i believe the issue is the adjuster itself is binding on something. The motor turns over well enough for about 340 degrees then I can feel something rubbing for the last bit of rotation but its still stiff enough where the kick start lever doesn't have enough torque to turn the engine over at all. Here is a somewhat grainy and out of focus picture of the cam chain adjust in it's slot in the engine case.

I can see the adjuster making its way up to the base of the cylinder block but I cant see any thing that it might be binding, the adjuster worked fine prior to installation and I am currently letting my nerves cool. I want to fix this issue WITHOUT pulling the head and ruining another gasket set. Im in desperate need of advice I have most of today and tomorrow free if more pictures are necessary.

[Desert Dan]

Here are some pictures of the latest assembly of the top end so if you spot some critical error I may have made durring installation let me know.

[Desert Dan]

Never mind I figured out the issue and fixed it, I had a mild brain aneurism though fixing it. If you notice on the 4th image down on my last post the cam chain guide was installed backwards so I had to un-torque the head separate it from the cylinders a 1/4in and reposition the cam chain guide. Im hoping Im lucky and the head gasket holds even though I torqued it once the head separated from it cleanly and there was no damage to it. With the guide fixed the engine now turns over freely and the adjuster works again so now I can dial in the cam and hopefully get this spiteful thing running.

[Desert Dan]

Im beginning to think this bike is cursed or some sort of jinx, I got the engine all put back together and the darn thing refuses to start. The issue appears to be the engine not getting any fuel, so I dropped all the carb bowls and cleaned out the jets and passages with carb cleaner but it is still not getting gas to the cylinders. I rebuilt the carbs a few months back and had them tuned and working well prior to the top end rebuild. Ive got good spark to all four plugs. Prior to the rebuild I had the ignition timing spot on so I didn't think it was necessary to re-time it for the first start, but Ill check and or adjust that tomorrow.
   
    I spent an entire day measuring the cam with my dial gauge indicator and I couldn't get the hang of it so I decided to use the stock cam sprocket for now and revisit the adjustable sprocket later on down the road. I set up the cam with the notch lined up with the top of the head facing the exhaust side of the engine with the engine at tdc. Setting the valve lash went smoothly and when #1 is at tdc and on its power stroke the valves are fully closed with the proper gap, as I rotate the engine forward from there the exhaust valve opens and closes until Im back at tdc followed by the intake valve opening then closing.
   
    At this point I was pretty sure the cam was properly set up so I did a quick compression test and with a cold engine and the new rings yet to be worn in and properly seated. I got 60psi across the board, I only kicked the engine over 4 times for each cylinders compression test so I felt that was adequate. Seeing as there is still no fuel getting to the cylinders Im beginning to think there is not enough compression/suction to pull the fuel in to the cylinders. Im going to redo the compression test tomorrow and Im hoping the new head gasket seated correctly and Im not loosing compression past it. I may be overthinking the fuel problem and it will probably end up being something simple but hopefully some one will chime in with some ideas on what I should do next to get this sucker to start. Even with all my careful planning and preparation this motorcycle has fought me every inch of the way since I bought it so Im considering naming it Old 666 after my great Uncle's B-17 that he flew during the war.

[goldarrow]

How did you hook up your gas supply? Post pics?

[calj737]

It would also be worthwhile to use the "clear tube method" to verify fuel level in the carbs. You never know, after handling the carbs you may have whacked the float levels badly and there too low now.

[Desert Dan]

Well I am feeding the worst at this point as the is still no sign of ignition. I verified that the carbs are filling up with fuel properly but that fuel is not traveling to the cylinders. I think when I had to lift the cylinders to flu the cam chain guide I ruined the sealing property of the head gasket and pressure is leaking between the cylinders because i can't get a pressure test above 60psi.

 Also I reset the ignition timing and something is off with the 1-4 points as they turn which ever coil I hop up to them in to an electromagnet and kill the spark to the corresponding plugs. I took the entire points assembly all the way apart to get a fresh view of what is going on with them and discovered there is significant run out on the bolt screwed in to the crank .025in so that's another issue I need to figure out.

[calj737]

If I could, stop and address one problem at a time. First get your point corrected and insure you have spark. Then proceed to fuel. Then proceed to combustion. Wandering all over the place and picking at different problem will lead to unanticipated results.

Regarding your compression, drip some oil into the cylinders and re-test. And confirm you are using a motorcycle type tester, not an automotive type. Auto types produce irregular results in pressures. And compression results are more important if all 4 cylinders are equal (or very close to each other) more or less. The pressure read is not so important at all.

[Desert Dan]

Thanks for the reality check I was getting a little frazzled with all the issues going on. I put the points back together and statically timed them now I have spark on all 4 again. I then did as you said and put about a tea spoon of oil in each cylinder and compression rose to about 160psi on each. I'm using a harbor freight compression tester and it's not designed for motorcycles.

[calj737]

Now, I think you're ready to verify fuel. Step-by-step, check everything as you go.

[Desert Dan]

Ok so I took off the airbox and intake plenum on the back of the carbs and I got it close to firing by spraying starter fluid in the carbs as I crank it. I'm taking a break for today and will pull the carbs tomorrow to really clean them out and reset the float heights. I can confirm they are getting fuel to the bowls as when I first turn on the fuel the over flow tubes drizzle some gas for about 5-10 seconds.

I need to re address the spark as I will get a good strong spark on all 4 plugs then they will randomly quit sparking. I'll pick up new condensers on my way home tomorrow and see if that helps

[Desert Dan]

Good new everybody! She lives and runs great! Thanks to calj737's advice I went through piece by piece and got it figured out. Unfortunately I don't know exactly what was causing the non start issue because I did multiple things to it before starting it, instead of trying after each different fix. I took the valve cover off to verify that I had installed the cam correctly which I had, this also entailed re adjusting the valve lash. I also took the carbs back off and verified the float heights were still set correctly and cleaned out all the jets and passageways with carb cleaner. I drained the gas tank and refilled it with fresh 87 octane from the nearby gas station. I replaced the condensers even though Im 95% sure the old ones were fine, the coil issue was caused by the blue trigger wire on the 1/4 coil grounding out on the coil bracket when ever I installed it.

So here it is in all it's glory, this isn't it's first start as I wasn't expecting it to start the first time it decided to fire up so I didn't have my camera ready.

[calj737]

Probably the BLUE wire grounding out your spark. But at least now you know everything is 100%! Nice job and good looking bike 

[Stev-o]

Congrats -  bike sounds solid!    Kudos to Cal, he's helped get another one running. 

[Desert Dan]

Thanks Steve-o and Cal, I did a number of test rides to break in the rings and the motor felt stronger after each ride. I put about 50 miles on it today and I plan on doing the first oil change at 100m Im using standard 20w-50 motorcycle mineral oil in combination with a zinc additive. Its running a tad on the lean side right now with stock 100 manes and 40 idles with the stock air box set up and a uni-foam filter. I think the boots that go from the air box to the carbs are letting air by causing the lean condition so I ordered new boots from Germany for $35 U.S including shipping, It'll take an extra week to come from Germany but its worth it to save paying the additional $25 4into1 and David silver spares wants for their boot kits. Once the new boots are on Ill continue to dial in the carbs Ive got 98 mane jets standing by incase they're called for. Before the rebuild I had the needle clip set in the middle position (3rd from top or bottom depending on which way you count) I had tried the 2nd from top which was too lean and second from bottom which was too rich so Im thinking second from the bottom with the 98's will be the ticket.