Honda Twins banner

1 - 20 of 39 Posts

·
Registered
Joined
·
23 Posts
Discussion Starter #1
Hello, I'm new to the board and ready to annoy you with questions.

I have acquired a 68 CB450 for a dirt cheap price. The owner says it has been rebuilt/overbored once and last time ran in 1998. The rust is mostly surface. The toolbox is trashed. Carbs are rusted shut. Now the thing that bothers me is that it does not turn over. The kickstart is just stuck to where even lots of pressure yield no result. The gearshift goes 1-N-2-stuck.

Any ideas on what I should attempt first? Are the carbs worth rebuilding or is there an alternative?

 

·
Registered
Joined
·
608 Posts
this is one where you just have to start pulling it down and see what you've got, it almost certainly has a piston stuck to the cylinder, when these old motors are parked they usually have a open valve on one side or the other and condensation gets in, so you're looking at a cylinder hone job and a valve lapping, try moving the rear wheel when you shift gears but since the motor is froze the tranny isn't going to turn over either, these old bikes are fairly tough and it can most likely be rebuilt cost will depend on how much you are willing to do yourself, carbs will likely be rebuiltable and probably just need a good cleaning, any idea why it was parked in the first place? that may influence your options
 

·
Registered
Joined
·
145 Posts
1.) pull the plugs and spray a bunch of PB Blaster into the cylinders, wait a couple days

2.) pull the plugs and spray a bunch of PB Blaster into the cylinders, wait a couple days

3.) Go buy a Clymer manual for the bike.

4.) pull the plugs and spray a bunch of PB Blaster into the cylinders, wait a couple days

5.) While you're waiting, read the Clymer

6.) Pull the dynamo cover, put a wrench on the bolt in the center, and see if the crank will rotate in either direction. Don't use too much force though.

7.) If it moves, hit the cylinders with PB Blaster again and try kicking it over

8.) If it kicks over, its worth trying to make it run, sometimes..... so set the valves & cam chain tension

9.) clean the carbs, replace the oil, and borrow a battery
 

·
Registered
Joined
·
608 Posts
Honest Don said:
6.) Pull the dynamo cover, put a wrench on the bolt in the center, and see if the crank will rotate in either direction. Don't use too much force though.
I disagree here, one direction you loosen the nut if the engine is still stuck, the other direction you can over tighten it stripping it or breaking off the end of the shaft ... use the kickstarter to try moving it, it's what it's on there for, or with spark plugs out and bike in gear try turning the rear wheel in both directions, bumping the crankshaft/pistons in both directions, either way don't get to rough with it, the rings are seized to the cylinder wall and to the piston even if you get it moving it likely will have compression issues
 

·
Registered
Joined
·
23 Posts
Discussion Starter #5
I actually pulled all of the other parts out - tank, seat, covers, carbs etc. My tools are elsewhere this week so I did not have the large plug wrench to get the plugs out, I did, however, spray PB blaster into the intake/exhaust valves. Tried the kick start, the engine moved about 10 degress and stuck again. So I'm going to pull the plugs tomorrow and soak the thing properly.

Prev. owner says the engine ran when parked and has been rebuilt/overbored once before.

I do, however have another question. What is the black valve for? The repair manual I have does not even mention it.
 

·
Registered
Joined
·
608 Posts
that's the steering dampener knob, don't know where the labeling came from :lol: but you tighten or loosen that knob to control steering head shake
 

·
Registered
Joined
·
175 Posts
The words on the steering damper adjustment are probably a reminder to the rider to shut off the fuel cock. Watch the valves through the spark plug hole - you could have a valve stuck open, which can hit the piston and stop the motor from turning. After you drain the old oil, pour it from one container to another and watch for water. If there's water in the oil, it was on parts inside the case at some time and you could have some serious rust problems inside the crankcase. It often happens with bikes stored outside and it can be pretty destructive. I suspect you're in for a teardown, anyway.
 

·
Registered
Joined
·
23 Posts
Discussion Starter #8
The bike has been stored in a garage I know that for a fact.
I don't think the valves are stuck, when I turned the engine, all of the valves changed state. IE before the left cyl intake was open, exhaust was closed; right cyl intake was closed exhaust was open. After I turned it, it was all backwards. I just need to let it sit for a while I guess.

Pulled off the exhaust pipes. The left one spilled a pile of rust flakes onto the floor. The right one was pretty solid. The toolbox is completely rusted through - will have to make another one. Gas tank did not look dark inside, although it is dry.
 

·
Sensei
Joined
·
27,163 Posts
You stated the engine wouldn't turn over, but that you turned it over....WHICH is it?
 

·
Registered
Joined
·
23 Posts
Discussion Starter #10
The engine was locked up and would not budge even with pressure applied to the kick start. I sprayed PB blaster in through the intake and exhaust ports. Then it turned slightly and because stuck again.
 

·
Registered
Joined
·
23 Posts
Discussion Starter #11
Removed spark plugs, poured in PB Blaster. Engine turned over a few times and stuck again... I guess I'll wait a little more. Will post pics of nasty valves tonight.
 

·
Registered
Joined
·
145 Posts
jayel said:
Honest Don said:
6.) Pull the dynamo cover, put a wrench on the bolt in the center, and see if the crank will rotate in either direction. Don't use too much force though.
I disagree here, one direction you loosen the nut if the engine is still stuck, the other direction you can over tighten it stripping it or breaking off the end of the shaft ... use the kickstarter to try moving it, it's what it's on there for, or with spark plugs out and bike in gear try turning the rear wheel in both directions, bumping the crankshaft/pistons in both directions, either way don't get to rough with it, the rings are seized to the cylinder wall and to the piston even if you get it moving it likely will have compression issues

I agree with the potential dangers, however, I did say not to use much force. I probably should've been more clear. Sometimes, if it hasn't set terribly long, its only a small amount of corrosion on top of the top ring. If this is the case, you can just back the piston off of the affected area, lubricate accordingly, and try a "running start" at it with the kickstarter.

I've been lucky with this method on several occasions. Compression afterwards wasn't anything like fresh rings, but definitely still run-able
 

·
Registered
Joined
·
23 Posts
Discussion Starter #13
So here is a picture of the lovely head ports and valves. Rag+chemical clean up or tear apart the head? The engine moves freely now.




 

·
Registered
Joined
·
608 Posts
eeuhuu supernastycalifrajilisticextraaledouchous, I'd take it apart just to clean it, that stuff in there isn't going to do it any good even if you got it to run like that
 

·
Premium Member
Joined
·
5,610 Posts
First off, great to hear you got the engine moving, good work and patience

I'd tear it down as well. One good thing is those pics will make one hell of a group of before pics :) If you do tear it down, take lots of pics and keep us updated on the progress, should be a fun project.

Best of luck.
 

·
Registered
Joined
·
23 Posts
Discussion Starter #18
See, I'm not sure that the rebuild would entail. Sure I can take parts off and clean them, but that's really as far as I can probably go by myself. I'm thinking I want to see if it will run as is. If it does, do a small rebuild/clean up. If not, sell it for parts.

I take pictures at every step and every part removal step.

Now, the carbs looks pretty good inside, I still put them in some carb cleaner. But the throttle valves are stuck, I can not get the to budge. What's your take on that?
 

·
Registered
Joined
·
175 Posts
I assume you've tried penetrating oil - Heat them the carb body with a heat gun while applying some rotational pressure to the throttle shaft. aluminum expands a lot when heated.
 

·
Registered
Joined
·
23 Posts
Discussion Starter #20
KERRY said:
I assume you've tried penetrating oil - Heat them the carb body with a heat gun while applying some rotational pressure to the throttle shaft. aluminum expands a lot when heated.
Just as an update, I got everything sorted out with the carbs, I think. Now just need to hunt down some new floats - the old ones leaked.

Then going to try and start it.
 
1 - 20 of 39 Posts
Top