Hey Fellas,
I'm a long time lurker here on the site, and have already learned a great deal from you guys, but need some help.
I have a 1976 CB500T (20,000 original miles) that I bought for next to nothing last year from a guy in Luray, VA. The previous owner said the bike shut off after a short drive and wouldn't restart. He took it in to a local dealer and a leakdown test revealed the bike had bent valves, so he put it up for sale as is. After I bought it from him, I took it home and tore the engine down to see what I could find. Sure enough, I found that one of the internal rollers had snapped, which made the cam chain loose, skipping teeth, ultimately screwing up the timing and bending the valves.
I ordered 4 new valves and took the head into a machine shop to have a valve job done and new valves installed. I also went ahead and had the jugs hones and pistons measured to make sure they're in spec. Everything passed according to the clymer manual and we did an acetone leak test for the new valves which passed fine.
Now for the rebuild; I ordered a replacement roller, new gasket kit, new piston rings, new cam chain, and did my best to install each following the manual steps. Intake and Exhaust Cam marks match LT on the left cylinder non compression stroke. (I dont believe the Cam timing has to be set on compression stroke, and the off stroke is easier to set since the engine wants to roll over past LTDC on the compression stroke, feel free to correct me). I adjusted the valves to spec, and believe at this point the engine is ready to go.
Now instead of going ahead and putting the engine right back in the bike, I get the bright idea that I want to make this a Cafe/Brat style bike and make a ton of cosmetic mods, new seat hoop and seat, new Mikuni vm32 carbs from DCC. Welded on new tabs for a new tank (different CB model), new clipons, controls, gauges, electronic ignition by pamco with e-advancer, powder coat the frame, all kinds of fun things.
Now, recently I put the engine back in the bike and started reconnecting all the wiring, all my indicator lights for gauges are working fine (with the exception of neutral indicator light/switch, I'll come back to that). New Pamco ignition installed following (Welcome to the PAMCO CB450 Installation Guide).
New carbs installed, pod air filters, stock exhaust pipes are back on, fresh gas, and guess what? No start.
Check for spark by pulling the plugs, grounding them to the engine, both have nice bright blue spark. I put them back in and turn the engine over a few times, pull them again, one is bone dry, one is covered in gas. Adjust the mixture screws a bit for each to richen and lean them out respectively. Still no start. run through these types of carb adjustments until my battery dies, then I drink a ton of bourbon and weep like a child lol. Recharge the battery over the next 2 days via trickle charger.
Few days later, I start doubting myself on the rebuild of the engine and check compression on the left and right cylinders. Both are pretty even, but also pretty low at about 115psi. I'm not sure if this is too abnormal since I just put on new rings that havent seated, but maybe thats my problem. I try a wet compression test and put a bit of oil in the cylinder, retest, and get 115psi in the right cylinder and 125psi in the left.
After several troubleshooting days, of adjusting carbs, checking spark plugs again and again, rechecking valve clearances on the compression strokes for left and right, I am completely stuck for what could be the issue. The problem is, that i've essentially touched or changed every component on the bike and dont know where to begin to troubleshoot, other than to run through the basic checks on spark, air, fuel, compression, timing.
I mentioned the neutral switch indicator light earlier, for whatever reason this light isnt working on my gauges, and i think its just a bad switch. I've got the bike in neutral, the back wheel spins freely, but is it possible that this model 1976 has a failsafe that would prevent the bike from starting if that indicator isnt working? I dont think thats related since its in neutral and I've got spark.
Any other ideas or thoughts you guys have for additional troubleshooting steps would be great. Sorry for the book, just wanted to provide all details. Thanks for the help!!
I'm a long time lurker here on the site, and have already learned a great deal from you guys, but need some help.
I have a 1976 CB500T (20,000 original miles) that I bought for next to nothing last year from a guy in Luray, VA. The previous owner said the bike shut off after a short drive and wouldn't restart. He took it in to a local dealer and a leakdown test revealed the bike had bent valves, so he put it up for sale as is. After I bought it from him, I took it home and tore the engine down to see what I could find. Sure enough, I found that one of the internal rollers had snapped, which made the cam chain loose, skipping teeth, ultimately screwing up the timing and bending the valves.
I ordered 4 new valves and took the head into a machine shop to have a valve job done and new valves installed. I also went ahead and had the jugs hones and pistons measured to make sure they're in spec. Everything passed according to the clymer manual and we did an acetone leak test for the new valves which passed fine.
Now for the rebuild; I ordered a replacement roller, new gasket kit, new piston rings, new cam chain, and did my best to install each following the manual steps. Intake and Exhaust Cam marks match LT on the left cylinder non compression stroke. (I dont believe the Cam timing has to be set on compression stroke, and the off stroke is easier to set since the engine wants to roll over past LTDC on the compression stroke, feel free to correct me). I adjusted the valves to spec, and believe at this point the engine is ready to go.
Now instead of going ahead and putting the engine right back in the bike, I get the bright idea that I want to make this a Cafe/Brat style bike and make a ton of cosmetic mods, new seat hoop and seat, new Mikuni vm32 carbs from DCC. Welded on new tabs for a new tank (different CB model), new clipons, controls, gauges, electronic ignition by pamco with e-advancer, powder coat the frame, all kinds of fun things.
Now, recently I put the engine back in the bike and started reconnecting all the wiring, all my indicator lights for gauges are working fine (with the exception of neutral indicator light/switch, I'll come back to that). New Pamco ignition installed following (Welcome to the PAMCO CB450 Installation Guide).
New carbs installed, pod air filters, stock exhaust pipes are back on, fresh gas, and guess what? No start.
Check for spark by pulling the plugs, grounding them to the engine, both have nice bright blue spark. I put them back in and turn the engine over a few times, pull them again, one is bone dry, one is covered in gas. Adjust the mixture screws a bit for each to richen and lean them out respectively. Still no start. run through these types of carb adjustments until my battery dies, then I drink a ton of bourbon and weep like a child lol. Recharge the battery over the next 2 days via trickle charger.
Few days later, I start doubting myself on the rebuild of the engine and check compression on the left and right cylinders. Both are pretty even, but also pretty low at about 115psi. I'm not sure if this is too abnormal since I just put on new rings that havent seated, but maybe thats my problem. I try a wet compression test and put a bit of oil in the cylinder, retest, and get 115psi in the right cylinder and 125psi in the left.
After several troubleshooting days, of adjusting carbs, checking spark plugs again and again, rechecking valve clearances on the compression strokes for left and right, I am completely stuck for what could be the issue. The problem is, that i've essentially touched or changed every component on the bike and dont know where to begin to troubleshoot, other than to run through the basic checks on spark, air, fuel, compression, timing.
I mentioned the neutral switch indicator light earlier, for whatever reason this light isnt working on my gauges, and i think its just a bad switch. I've got the bike in neutral, the back wheel spins freely, but is it possible that this model 1976 has a failsafe that would prevent the bike from starting if that indicator isnt working? I dont think thats related since its in neutral and I've got spark.
Any other ideas or thoughts you guys have for additional troubleshooting steps would be great. Sorry for the book, just wanted to provide all details. Thanks for the help!!