View Full Version : 1971 Honda CL70 Won't Start... Help!!

07-29-2011, 09:46 AM
So I've adjusted the valves, the ignition timing (points open as the the "f" and little line align) and set the carburetor to the specifications in my Clymer manual. The spark plug works perfectly and it has a new battery and ignition coil. All this and it will not run. I got it to start for a few seconds but couldn't get it to start again afterwards. However, it would run before I adjusted the valves and timing (but not very well). It would begin to die and shoot flames out of the exhaust after applying 1/4 throttle. Another new problem is that the the petcock (or the metal inserts which connect the petcock to the fuel line) is worn and now leaks. Would this cause it to not start? It's not a very big leak, about 1 drop a minute.

Should I just order a new petcock? I think it just the outlet nipples that were destroyed when my brother tried to rip them out of their old fuel line.

07-29-2011, 09:49 AM
Once I get it running I'll post pictures!! The bike is in absolutely amazing condition!

08-12-2011, 12:46 PM
My son bought a '72 CL 70 last week and it drove home just fine. Next day, it wouldn't start. After a lot of forum support, we narrowed it down to a fouled out spark plug. Once we got it to start, we emptied the gas tank and refilled it with fresh fuel. If your bike sat for any length of time..even a couple of weeks in some climate, you could have bad fuel. Those are the simple places to star looking before you o anything drastic. Good Luck!

08-12-2011, 12:55 PM
Glad you found that it was the spark plug. I advise people to start with the cheapest fix first...

#1 replace the fuel!
#2 replace spark plug etc etc

Of course you just said this yourself but it's exactly where people should start... oh wait... FIRST check that the ignition switch is in the "on" position. No joke - a friend of mine couldn't start his old bike and I just simply switched the ignition over the other direction and it started right up. :D

08-13-2011, 12:59 PM
The fuel line on our CL 70 became disconnected at the engine (inside the frame), which looks pretty well inaccessible. Do I have to drop the engine to get the hose back on it's connection?

08-13-2011, 05:48 PM
Hey everyone! So you know how I mentioned the small leak? Well I fixed that with some sort of gas tank repair putty and a new petcock. The bike ran like it was new after that! It would start on every kick no matter how weak. After a few times running it I guess a gasket finally gave out. The bike still starts but revs as if it were at full throttle. Using WD-40 I sprayed around some known gaskets until I found what I think is the problem. When I sprayed the cover for the timing chain the idle would slow down and almost die. I made a new gasket with some of this: http://www.permatex.com/products/automotive/automotive_gasketing/gasket_makers/auto_permatex_ultra_copper_maximum_temperature_rtv _silicone_gasket_maker.htm

Not sure if it'll work though so I ordered an entire new gasket set. Does that make any sense that a leak for where the timing chain is would cause problems? It wasn't even leaking oil.

As for Kvanpamel, I have no idea why your fuel line even goes through the frame. I haven't seen one like that.

As for everyone else's ideas: I know I'm a beginner at mechanics but I developed the habit of checking the key, petcock/fuel line, then plug when it doesn't start. So until I get my gaskets heres a picture of the bike for you guys to drool over :P


She's not perfect but she's getting there :)
Next job is to maybe get a new kickstand because the other looks like it was broken an welded back together... Not properly though.

08-13-2011, 07:06 PM
Same color as ours....yeah..have no idea where that gas line disappears to once it leaves the carb, but I made the mistake of not pulling the hose off of the carb when we took it off for a cleaning and I must have disconnected the other end from whatever it's attached to. I'm really hoping we can figure a way to put it back as it was without pulling the engine out. We're totally new at this..we can't even get the seat off! I ordered a repair manual...wish us luck.

08-13-2011, 07:14 PM
Oh!!!! I know what you're talking about... That isn't part of the fuel line! that's just the overflow. The fuel leaves the carb to the engine by that metal pipe (called the inlet pipe) on the left side of the carb in the picture. The overflow is the black tube you see on the bottom of the carb going into the frame. It's not supposed to be connected to anything on the other end so don't worry you're safe!

08-13-2011, 07:32 PM
You're right. I couldn't figure out for the life of me what that thing was doing. Great and thanks. We have a leak but I'm sure that's just the carb not being seated right. Really appreciate it.

08-13-2011, 08:11 PM
Where is the leak coming from?

08-14-2011, 06:07 PM
It was the carb. I didn't seat it properly. It's fine now. No leaks and she starts right up.

08-14-2011, 07:05 PM
Awesome! That's great to hear!

08-19-2011, 03:59 PM
So remember that gasket maker I talked about? It seemed to have worked pretty good. The compression improved by so much it's incredible. I almost thought it had gotten seized somehow. It'll stop being able to idle after warming up though.

Another thing: While riding it's like the bike is really missing a lot of power. It accelerates VERY slowly after 2nd gear and the most i can get it is 3rd. Also it hesitates and jumps and whatnot. Any ideas of why this is?

I checked again for leaks and couldn't find any

08-21-2011, 10:52 AM
So I found something today that I found really weird. When I turn on the flashers on the bike, the bike gains a lot of power. Enough power to get me to 20 mph instead of 10. Any ideas?

08-21-2011, 02:45 PM
Update: After inspecting the plug I noticed it was had a pretty big layer of carbon that wasn't there from the last time I checked. In addition I checked the wires for any shorts. To fix the over-rich mixture I brought down the float height about 2mm and there were also a few wires that looked like they could cause problems. The bike got me to 30mph this time but refused to go faster.

Another thing to note: I couldn't get the bike to idle and it ran better with the air screw all the way in. The more I back the air screw out the faster the idle becomes. The idle screw has no effect, though.

If anyone has any ideas PLEASE help me out.

I took a video while riding it but don't know how to upload it onto here soo... :(

08-22-2011, 11:19 AM
Sure sounds like a compression issue, but the fouled plug is often due to bad (old) fuel. Fuel issues usually affect start up and idle...not so much overall speed. I hate to go back to the same advice you've been given already, but did you replace the fuel and the spark plug yet?

08-22-2011, 03:03 PM
Hmm maybe the gasket I made isn't as great as I thought? The new one came in today I think but I won't be able to install it until friday. I've also got a buddy who's an electrical engineer so he's gonna help me re-wire it.

I guess I'll order a bunch of new plugs too while I'm at it.

Is it possible that the plugs bad even though it's looks like it's giving nice sparks when I test it?

08-22-2011, 06:27 PM
I've uploaded the video to youtube to show you guys. Near the end of the video, when I start accelerating, you can hear how it doesn't accelerate smoothly and the fast I go, the worse it becomes, until it refuses to accelerate anymore.


The specific part is 0:24 to the end. The times before that were me letting go of the gas because I was scared to drop my new phone.

08-22-2011, 07:05 PM
It's definitely not getting enough fuel. Need more! So what gasket are you talking about a couple of posts ago?

About the carb those things must be SUPER clean inside all the passageways in order to run perfectly. I've seen people try and clean their carbs once, twice to no avail. Then who ever is next in line to work on the bike dips the carbs a couple more times and then it runs perfectly. It takes a few times to really make sure that you have the carb clean. Some people boil them in carb cleaning solution. Some people put them in sonic cleaning tanks with solution and baking soda. I prefer BOTH! Back to the solvent tank for you! Don't pass go and don't collect $200. :D

My CL70 will whip yours as it runs now. I need to get me some new tires...

If worse comes to worse you can send me your carb and I can clean and tune it on my CL70. Making a new wiring harness is a GREAT idea. I have soldered all my connectors and the light shine SO much brighter and the horn is strong. All those old connectors really hold back the current of the poor little 6V battery. I would like to make a new harness for mine someday.

08-22-2011, 07:21 PM
That little Honda 70 sounds like my air compressor! :) If my pipes weren't in such good condition on my little CL I would totally put a new trick looking muffler on it. I also found a guy that manufactures some REALLY cool mufflers that people use on some classic bikes all over. I'll have to find the pictures I took of them at a bike show a little while back.

08-22-2011, 08:03 PM
Haha well just wait until my bike is done and then we'll see :P

Also I have no idea where to buy the kind of carb cleaner that you can submerge the whole carb in. I can only find the spray ones. We don't have as many auto stores here in Canada... Especially in Quebec.

I also kinda have to update the wiring. When it was in it's little shed, (for about 30 years) some mice decided that the empty spot where the battery used to be was a great spot for a home. As a plus it came with some tasty wires. So because of the bad wires, the headlight rarely works, the blinkers don't blink (except they did once while I was riding it the day I took that video), the rear light randomly decided to start working one day, etc lol.

As for my exhaust, the chrome is in excellent shape but the pipe has some tears in it. I have no idea how they happened but you can see some of them in the picture right under the guard on the left side.

The broken gasket is the one for the cam chain cover. Here's a picture: http://images.cmsnl.com/img/partslists/cylinder-head-coverinletpipe-cl70-scrambler-k0-usa_bighu0007e1001_1182.gif

It is on the right of the picture labelled as number 7

08-24-2011, 03:29 PM
Ok so I finally put the new gasket on but when I started it, it idles REALLY fast. The exhaust is also really dark and applying cause flames to shoot out the exhaust. I was riding it a couple days ago and it didn't have this problem.

My personal input is that the new gasket resulted in better compression and less air intake from leaks therefore the previous carburetor settings no longer work. The extra rich mixture is backed up by the fact that it is getting a lot less air then before. Yes?

08-26-2011, 04:35 AM
Ok so as it turns out, my thought about it running too rich was only partially right. I adjusted the floats and it didn't really fix the problem. I also tried letting it warm up for a bit thinking that my help but it had no effect either. What did help was applying throttle while messing with the choke. It made the bike die but when I started it again it ran great. Dirt carb problem? I think so!

08-30-2011, 04:52 PM
Wow does changing a few connections and fixing some wiring issues make all the difference! The bike runs AMAZING now. Got it to 35 no problem but I ran out of road and didn't want to attract to much attention seeing as I don't have a license to drive bikes and the bike itself doesn't have a license.

There is one problem though. When I first start the bike, it revs REALLY high until I put the choke and a lot of throttle a bit. The choke brings down the revs to an acceptable level. After a few times of doing this and making the engine die out from it, it starts and runs fine. I tested the compression and it went up to 140 Psi with no decrease. I also put some new gaskets in and can't find any leaks at all.

My suspicion is that the new petcock I ordered is crap. The thing drips out gas even in the off position. I think the pressure from gas always trying to get in (and actually filling the carb) really messes with it until the excess is burned.

08-30-2011, 08:54 PM
Yeap cleaning up the wiring and cleaning out corroded connectors (or replacing them) really helps huh!? Now to just fix the pesky fuel flow problem. : \

It should just run perfectly! Don't stop until you get it right.

09-10-2011, 03:59 PM
Alright so I've done everything I can do. The only problem is that when the bike is on weird inclines it goes nuts and revs to the max. Raising the floats makes this issues less frequent but it still happens whenever I have it parallel to the garage door (lol). Raising the floats, however, has caused a large loss of performance. The bike accelerates pretty slowly after 30. Is that normal?

09-16-2011, 12:11 PM
So I brought my exhaust pipe to a local welder. To my disappointment he said it was completely rotten and could not be fixed. Even worse is that it was so bad that when I took out all the bolt's holding it to the frame, it snapped in 2 under its own weight. Seeing as there are no mufflers to buy ANYWHERE I am stuck. This is the last piece I need to get the bike licensed again so I'm pretty depressed :(

09-17-2011, 11:42 AM
Keep looking on eBay. If not, they have some aftermaket mufflers that will let you get it at least licensed.

09-17-2011, 04:07 PM
Unfortunately there are only two sellers of aftermarket exhausts on ebay and both have to be modified to fit. By modified they mean have brackets welded on and the mount for the heat guard welded on also.

09-19-2011, 04:35 AM
I thought i found one that bolted on, i'll have to check it again online and see what it was.

09-20-2011, 04:06 PM
That would be amazing if you know of one! I can't find anything at all.

09-21-2011, 08:15 PM
I've thought about making an exhaust for these bikes but by the time you bought materials and threw in a little labor it would be up to $350 or $400 :-/ at least for the first 2 or 3 sets until I got good at makin em.

09-23-2011, 02:14 PM
nice bike clean, looks great..