1981 CB650c Won't Start
Posted: Wed Jun 06, 2018 11:03 pm
Hey everyone. First-time poster, but I've been lurking on here for the past couple weeks and I am looking for some advice.
I just picked up a 1981 CB650c for $800 about 3 weeks ago from this older lady who said the bike had belonged to her husband that high-tailed it out of the province and wasn't coming back.
Anyways, she told me that the tank was off the bike, but it did start (it did not infact) and that the bike had had a lot of work done to it over the winter (cleaned carbs, new gaskets and seals) and my buddy who knew the lady vouched for her on it, so me being completely inexperienced with motorcycles, decided to buy it figuring it would be no problem to get it started. (just connect the tank and go, right?)
Oh did I mention this is my first bike?
This will be a long post.....
So I brought it home and opened the tank and it was completely covered in rust, so I did some googling on how to remove it and picked up a couple jugs of Evaporust and dumped it into the tank with a bunch of bolts and let it soak for a week while I flipped/rotated and shook it daily. The end result was great.
The tank is still soaking in fresh evaporust to make sure I get it all, and so it doesn't happen again while I decide if I want to try using a tank sealer.
So, my first question I'm looking for advice on is: Should I use a tank sealer?
I've done a lot of reading and watched tons of videos of different products to seal a gas tank and I've come down to two options, POR-15 or Caswell.
So if anyone has tried either of these products, I'd like to know how it turned out? Did it fail after a while? Or am I better off to not seal it all all?
Either way, while my tank was out of commission, I made an auxiliary fuel tank to test the bike.
I couldn't get it to start.
So I replaced the spark plugs, the old ones had lots of carbon build up and one didn't have good continuity.
It still didn't start.
I hit it with two short sprays of quick start through where the air filter sits and I got it to run for maybe 10 seconds with the throttle wide open before it died out. I tried this a few times until I killed the battery. (which I have also replaced with a new one a few days after, I figured it couldn't hurt)
So after having no luck getting it started I tested the compression on the cylinders to see if that could be the problem.
The results came back as:
#1 - 90 PSI
#2 - 90 PSI
#3 - 60 PSI
#4 - 75 PSI
So I did some more googling, and I attained 3 different shop manuals for CB650's and decided I might as well try to set the valve clearance and see if that helps. After triple checking all of them and was satisfied with the results I put the cover back on and did another compression test.
The new results were:
#1 - 90 PSI
#2 - 90 PSI
#3 - 65 PSI
#4 - 90 PSI
So I figure something is probably wrong with cylinder 3? Maybe a leak? (the spark plug is also a pain to get to without the EXACT socket...)
Either way. I figure this thing should still fire up with these readings, right? I picked up a new set of piston rings if I end up having to take the engine apart anyway. (I'll probably overhaul it in the winter regardless)
So now my next step was to examine the carbs...
So I drained and removed them from the bike with the help of my roommate and opened up the first float bowl expecting to see freshly cleaned carbs, like the lady had said.
It was grimy as hell!
So I went through all 4 carbs and cleaned tons of build up and rust from them.
The gasket from the accelerator pump needle split in two as soon as I removed it.
After cleaning them all I assessed what needed to be replaced.
I've ordered 4 carb rebuild kits, 4 floats and new parts for the accelerator pump, which I'm currently waiting to receive.
So once the new parts arrive, I'll be removing the carbs again and overhaul them. Hopefully it solves the problem.
Now the other thing I noticed is the starter doesn't always catch to crank the engine, I removed it and it looked like it had just been replaced.
I stuck my finger in the hole and it didn't feel stripped either.
I tried turning the engine by hand and it seems like the starter catches when it sits in a "sweet spot", otherwise it seems pretty random when it turns, or not.
I know that's a lot of information for one post, but I think I covered everything up to now.
Any advice or suggestions would be greatly appreciated!
Thanks!
I just picked up a 1981 CB650c for $800 about 3 weeks ago from this older lady who said the bike had belonged to her husband that high-tailed it out of the province and wasn't coming back.
Anyways, she told me that the tank was off the bike, but it did start (it did not infact) and that the bike had had a lot of work done to it over the winter (cleaned carbs, new gaskets and seals) and my buddy who knew the lady vouched for her on it, so me being completely inexperienced with motorcycles, decided to buy it figuring it would be no problem to get it started. (just connect the tank and go, right?)
Oh did I mention this is my first bike?
This will be a long post.....
So I brought it home and opened the tank and it was completely covered in rust, so I did some googling on how to remove it and picked up a couple jugs of Evaporust and dumped it into the tank with a bunch of bolts and let it soak for a week while I flipped/rotated and shook it daily. The end result was great.
The tank is still soaking in fresh evaporust to make sure I get it all, and so it doesn't happen again while I decide if I want to try using a tank sealer.
So, my first question I'm looking for advice on is: Should I use a tank sealer?
I've done a lot of reading and watched tons of videos of different products to seal a gas tank and I've come down to two options, POR-15 or Caswell.
So if anyone has tried either of these products, I'd like to know how it turned out? Did it fail after a while? Or am I better off to not seal it all all?
Either way, while my tank was out of commission, I made an auxiliary fuel tank to test the bike.
I couldn't get it to start.
So I replaced the spark plugs, the old ones had lots of carbon build up and one didn't have good continuity.
It still didn't start.
I hit it with two short sprays of quick start through where the air filter sits and I got it to run for maybe 10 seconds with the throttle wide open before it died out. I tried this a few times until I killed the battery. (which I have also replaced with a new one a few days after, I figured it couldn't hurt)
So after having no luck getting it started I tested the compression on the cylinders to see if that could be the problem.
The results came back as:
#1 - 90 PSI
#2 - 90 PSI
#3 - 60 PSI
#4 - 75 PSI
So I did some more googling, and I attained 3 different shop manuals for CB650's and decided I might as well try to set the valve clearance and see if that helps. After triple checking all of them and was satisfied with the results I put the cover back on and did another compression test.
The new results were:
#1 - 90 PSI
#2 - 90 PSI
#3 - 65 PSI
#4 - 90 PSI
So I figure something is probably wrong with cylinder 3? Maybe a leak? (the spark plug is also a pain to get to without the EXACT socket...)
Either way. I figure this thing should still fire up with these readings, right? I picked up a new set of piston rings if I end up having to take the engine apart anyway. (I'll probably overhaul it in the winter regardless)
So now my next step was to examine the carbs...
So I drained and removed them from the bike with the help of my roommate and opened up the first float bowl expecting to see freshly cleaned carbs, like the lady had said.
It was grimy as hell!
So I went through all 4 carbs and cleaned tons of build up and rust from them.
The gasket from the accelerator pump needle split in two as soon as I removed it.
After cleaning them all I assessed what needed to be replaced.
I've ordered 4 carb rebuild kits, 4 floats and new parts for the accelerator pump, which I'm currently waiting to receive.
So once the new parts arrive, I'll be removing the carbs again and overhaul them. Hopefully it solves the problem.
Now the other thing I noticed is the starter doesn't always catch to crank the engine, I removed it and it looked like it had just been replaced.
I stuck my finger in the hole and it didn't feel stripped either.
I tried turning the engine by hand and it seems like the starter catches when it sits in a "sweet spot", otherwise it seems pretty random when it turns, or not.
I know that's a lot of information for one post, but I think I covered everything up to now.
Any advice or suggestions would be greatly appreciated!
Thanks!