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1969 Honda CL70 Scrambler! My old dirt bike returns!

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  #1  
Unread 09-19-2011, 02:46 PM
montanaman montanaman is offline
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Default 1972 Honda CL70 problem

Hello all,

I am having some of the same problems as the other thread, but dont know what to do. I picked up this bike and the guy said he thought it would run ok. I have a new carb, charged battery, good spark, and fresh gas but cant get it to start. I checked the valves and adjusted the exhaust and their both looking good. Some of the wiring is messed up or not hooked up, mainly from tail light, blinkers and a few others. I am waiting on a new wire harness but thought that since I was getting good spark, the main wiring to get it to fire was ok. The points look good, flat and appear to be timed ok.

Any thoughts or suggestions would really help because i'm all out of ideas.
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  #2  
Unread 09-19-2011, 06:14 PM
montanaman montanaman is offline
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Also,
I know the ignition works, I have checked it with volt meter, the points when open show about 6.4 volts ( i just touch the tip of the pos terminal between the points and get the reading). most of the lights are broken or mising but they do have power getting to them, and like i said, it has good spark.
I'm not sure if the condensor would keep it from starting, but that and the points are the only thing I have not replaced or confirmed. but like i said, they appear to open and close at the proper times.
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  #3  
Unread 09-19-2011, 06:54 PM
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Are you getting fuel? Did you squirt a little fuel in the cylinder to see if it would ignite and pop or give any sign of life?

If you got spark then you got spark. Whether it's out of time is another issue so you should check that incase someone has been messing around and never got it to work after they rebuilt it maybe? Check the screws and bolts to see if they were tampered with. You can see if a bike has been taken apart or not by checking the edges of the hardware as you look at the engine.

Last thing you might want to check the compression. Does it feel like it has any?
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  #4  
Unread 09-20-2011, 04:00 AM
montanaman montanaman is offline
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Well I am using a "funnel fuel tank" just to get it started. I want to get the tank cleaned before I run gas through it. But it pulls the fuel down and I have gotten a few "blue flames" and a few backfires, but thats it.

It does seem to have good compression. I dont have a tester, but just putting my hand over the spark plug whole, and the exhaust port and it seemed to have good compression.

The points look "good" almost to good, so I think your right, someone must have replaced them and may not have got the timming correct. I ordered a new primary coil, lighting coil, condesor and points to rebuild the generator.

I have cranked on it quite a bit, and it really hasn't even sputtered, only a few backfires and a blue flam or two.
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Unread 09-20-2011, 05:37 AM
montanaman montanaman is offline
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I had a backfire (blue flame) out of the back side of the carburator, that cant be good!
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  #6  
Unread 09-20-2011, 12:03 PM
montanaman montanaman is offline
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I covered the spark plug hole and cranked it a few times, it has little compression
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  #7  
Unread 09-20-2011, 12:05 PM
montanaman montanaman is offline
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how would you know if you have a stuck valve?
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  #8  
Unread 09-20-2011, 02:08 PM
montanaman montanaman is offline
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Well I got a compression tester and found it had NO compression. I squirted some oil down the spakk plug hole and re-checked it and none! Not sure what to do from here.
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  #9  
Unread 09-21-2011, 10:05 AM
montanaman montanaman is offline
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here are a couple pictures. I am still finding so many things that need fixing, I guess I should expect that with a bike that has been sitting for 20 or more years. I broke the exaust valve tappet or cover and was wondering if that being missing would affect the compression test.
Attached Images
File Type: jpg 4-AC293211-1035080-800.jpg (75.0 KB, 9 views)
File Type: jpg 4-A45CC959-1018444-800.jpg (74.7 KB, 10 views)
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Unread 09-21-2011, 08:10 PM
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Uh oh that doesn't sound good. If you take off the caps so you can see where you can check the valve clearance - then you can see if the valves are moving I suppose. The bikes engine would have had to be severely beat on in order to hurt it. They are so tough you would have to purposely take the oil out of it and run it to damage it.

I think the thing you said you broke is just the round cover that screws on and off to get to the valve train right? That won't have any effect on compression. It just keeps the oil in the engine and the dirt out. I wonder if maybe someone ran it without the air filter on and got some dirt or something into the engine causing damage. If the engine sat fro years and years there might be some rust inside but if it's turning over freely it probably is ok and not so bad. I wish I could give it a look up close for ya!
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Unread 09-21-2011, 08:13 PM
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Hmm if it's just out of compression it's time for a rebuild! I was rebuilding CT70 engines when I was 12 years old with scroungy tools so I know you can do it. Just turn the engine to top dead center with the timing marks and pull the whole thing apart and see what condition the rings and piston are in. Easy stuff.
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  #12  
Unread 09-22-2011, 03:37 AM
montanaman montanaman is offline
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Smithers, thanks for the information, I think you right, i'm just going to have to take it apart and see what it looks like. If you dont mind, I will probably need some help, sometimes the manuals just dont explain things enough.
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  #13  
Unread 09-22-2011, 09:36 AM
montanaman montanaman is offline
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Well I removed the head and it looks like it had been sitting in poor conditions for all those years. Here are a couple pics of the head and top of the piston. My question is, do I just buy a new head assembly ready to bolt on or rebuild this one? and what about the piston and rings, can I get away with getting a standard size piston? probably need to measure it first. Probably looking like a total re-build.
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File Type: jpg IMAG0110.jpg (91.8 KB, 5 views)
File Type: jpg IMAG0111.jpg (73.6 KB, 6 views)
File Type: jpg IMAG0113.jpg (132.0 KB, 6 views)

Last edited by montanaman; 09-22-2011 at 09:45 AM.
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  #14  
Unread 09-22-2011, 06:31 PM
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Not TOOO bad. Just need to have the machinist clean up the cylinder and head. They can hone it out to get the cylinder walls clean then measure it and give you their opinion. I can't tell the condition of the cylinder walls so I can't take a guess at if you need a 1 or 2 size over piston and ring set. This is easy stuff for any machinist that does engines. I would probably just "lap" the valves in with a hand spinner thing and some compound and put it all back together.

Just keep all the original parts as much as possible. I've fixed worse than what I see in your pictures. Shoot you could probably just hone out the cylinder yourself with a drill and ball hone - and then just re-use the piston with some new rings and be on your way. Just lap those valves in while you have it apart and make sure the guides and valve stems are operating smoothly. Put some synthetic grease on them while assembling and get that show on the road. :-)
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Unread 09-22-2011, 06:39 PM
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I would buy the following:
  • gasket kit for engine rebuild
  • oil seal kit for the kickstarter and shifter seals but you might as well do them all at this point - cheap.
  • pistons are cheap so probably a new piston and ring set
  • don't forget the wrist pin and circlips - all new don't re-use!
  • borrow a ball hone or buy one for like $30 maybe they might cost

A local machinist here in my town has done all this stuff a million times in his life so he charges me like $100 (at the most I know it wasn't more) to bore and hone the cylinder LIKE NEW and he gives me all sorts of advice on to of that which is priceless. This is for a Honda 150 twin but I don't think they will do a single cylinder for less than that these days. He also told me to go buy the larger size pistons I thought I would need and he bored the holes to match each one. He measured them so precisely that he labelled each piston a number and told me which one went in each hole. I guess even the Honda brand pistons weren't exactly the same size when you measured them. but anyhow you only have one so nevermind.

The valves you can just get a cheap suction cup grinder thing and just spin them like you are starting a fire. Of course you will need to use the grinding compound and have released the springs and keepers on the other end to allow them so spin. I'm just covering all the basics for the sake of recording this info here. I'm not assuming you haven't done anything mechanical in your life so bear with me.
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