And so it begins...

[Mellis4949]

Hello! Newbie here. I have fond memories riding CT70s as a kid, and I recently pulled these two bikes out of my dad's barn where they have been sitting for the last 25 or so years. They are pretty rough. This is a project for me that is one part nostalgia, one part personal growth (learning about engines - I am an inexperienced mechanic) and one part excited dad (to share the experience of riding these with my kids). I am so unbelievably grateful that a forum like this exists. The wisdom and experience here is incredible.

My goal initially is to get one running and then I will go from there. I chose the red one to start with. As you can see by the pic, they have been picked apart over time and neither had carburetors/air cleaners. The plug wires have been cut, and I have my work cut out for me. I've been watching videos online, reading posts here, and I bought a shop manual. Given that my starting point is unknown (not sure if there is spark, don't know about compression, etc.) I just decided to tear into it, take a look, and figure it out as I go.So far I have dropped the engine off ol' red and have pulled the cylinder and head. I bought a battery, new coil, points/condenser, gasket set, and a few other things. I am waiting for a few more items to arrive and I will begin to start to put it back together.

For where I am now, I have a questions regarding the valves. I have stripped the head all the way down and removed rockers, cam, valves, etc. It was very difficult to get the valves all the way out, particularly the intake. I cleaned the head as best I can and now when I try to put the valves back in they don't really go..Instead, they bind up and get stuck, and it takes a fair bit of force to shove them down. Should they slide up and down smoothly? (I would think so! I don't have a "good" example to compare to.) I have seen some reference to the "tuliped valve" reputation for these bikes and am wondering what I need to do...new valves? Will inexpensive (Amazon/probably Chinese) ones work, or are OEM a must? Take the head to a machine shop? I'm not sure what they can do. Attempt to clean the cylinder they insert into? I am reading conflicting information on whether or not it is necessary to lap them. If I do push them down they don't seat well - I can see daylight through the intake side when it is all the way down. Any advice or words of wisdom on how to proceed are appreciated.

Ok, well that is enough for now. It occurs to me that perhaps my questions should go in the tech area, and I don't necessarily want to breach etiquette, but on the other hand maybe this is a way to track progress on the project. Thank you very kindly.

 

[kirrbby]

Welcome to lilHonda Mellis4949. Those are a couple of good CT70's you have there.
Those valves SHOULD slide right in very easily. The valve stems could be rusted or bent? The valve guides could be rusted or somehow damaged? And you definitely should not be able to see light thru there.
Unless the valve seat is badly rusted...all can be replaced and repaired. If you could post up some good close pics of everything, you'll get some opinions and advice. A properly rebuilt head is a wonderful thing for your engine. It's a really good place to spend some money...especially for what you are trying to accomplish...IMO.

Someone with the tools and experience can recut your valve seats, replace the guides, new valves and rockers.
If the head isn't right, the engine isn't going to run well.
If you're seeing light thru the sealing surfaces, it's not going to run at all.

These are not uncommon problems for our engines. Don't sweat it too much. You're on the right road.

 

[69ST]

The valve guides are replaceable. Yet, that's rarely needed. They're made from a tough, but brittle, alloy. As long as they're not fractured or deeply pitted, even hammering-out a bent valve rarely causes damage. A fractured guide would be hard to miss...there'd be a jagged piece missing.

I've rebuilt heads that looked like old shipwrecks. The valve seats took the brunt of the rust damage, requiring a heavy cut. The guides just needed honing. Most likely, your guides just need to be cleaned-up. If they are worn out...which is very unlikely...replacement isn't expensive. Guides are cheap. It does require specialized tools, though.

 

[allenp42]

Welcome aboard. It looks like you have a couple a couple of bikes with solid bones, which have have escaped the rust termites. Racerx has a better term but I can't remember it at the moment. Also, both have a manual clutch! You may want to take a peek at the frame serial numbers (above chain guard & and tag on neck) and the engine serial numbers (near kick stand usually covered with grease and dirt) to see what you have unearthed. Regardless you definitely have something to work with.

There is ton of info already posted on this site and tons more that is only a post away.

 

[Tripod]

Welcome. Whenever possible go with oem parts. Dont throw anything out either.

 

[Mellis4949]

You guys are good! Kirrbby nailed it - the valve stems were bent ever so slightly (slight enough that I didn't notice it with the naked eye). They were stuck in there to begin with so it is possible I bent them trying to get them out. I took the head to a machine shop and they said the seats looked good. Initially my goal is to get the first bike running and learn, so I got some new cheapo valves off Amazon. They slide right in!


However, they come with the incorrect valve seal (like shown in https://lilhonda.com/index.php?threads/c70-vlave-seals.20758/#post-160565). So, I need to order the correct little green seal...and wait for it it arrive. I also don't see the hardened spring seat/seal cap retainer as referenced in https://lilhonda.com/index.php?threads/where-does-this-part-go.22265/#post-182170 either, so best get one of those too. I did put the intake side back together, so there is that!

In the meantime, I have a spare engine that was most likely taken off the yellow bike pictured in my first post. It has been sitting, uninstalled, with the bikes in the barn for years. I have been tinkering with that just to play around and learn. I actually wanted to take a peek and see what the valve seal looked like on that one because I didn't notice it when I did the breakdown on the first head. On the second one for some reason the rocker shafts will not slide out. I blasted it with PB, and the shafts are in the right way because the threaded ends are out and I can get the bolt to thread a few turns. They move a little when I push them all the way in, so I can tell the shafts themselves are bound up, but it just won't slide out like I know it should. I got one side out past the opening about 1/16th of an inch, but I just can't get it out any more.

Anyone have ideas on why or how to get the darn things out?

Living, learning, and having fun with this project. I spent WAY too much time browsing this forum today!

Notes on what I am working with:
The Red Frame is CT70H 2002199 - H K1 (1972 – 1973) with engine CT70E 112184 which I believe is a K0 engine from 1970-1971
The Yellow Frame is 199516 so...K0 with engine SL70E 106579 which must obviously have been off an SL70 - somebody put on there.
Loose engine CT70E 112184 (K0 motor from 69-71). Possibly original motor off the yellow bike.

 

[69ST]

Anyone have ideas on why or how to get the darn things out?

Living, learning, and having fun with this project. I spent WAY too much time browsing this forum today!

Notes on what I am working with:
The Red Frame is CT70H 2002199 - H K1 (1972 – 1973) with engine CT70E 112184 which I believe is a K0 engine from 1970-1971
The Yellow Frame is 199516 so...K0 with engine SL70E 106579 which must obviously have been off an SL70 - somebody put on there.
Loose engine CT70E 112184 (K0 motor from 69-71). Possibly original motor off the yellow bike.

Rocker pins can sometimes put up a fight. Start with the "Captain Obvious" approach...make sure the rocker is on the base circle of the cam, i.e. no spring tension against the rocker arm. The most likely cause of binding dirt/oxidation in the pin bore, the portion that can be reached with the pin fully seated. Reinsert the pin, then clean the bore using a fine Scotchbrite. Clean out all of the debris using compressed air & solvent, then oil the bore. If that doesn't do the trick, heat the head aiming the torch flame away from the pin; then insert an M8 bolt and extract the pin. The bolt can be threaded-in until it starts rotating the pin inside the bore; that, plus oil should loosen the grip considerably. Holding the bolt head with Vise Grips, you can turn the bolt while pulling. That bolt can also be used as an anchor point for some improvised slide hammer action...tapping against the Vise Grips with a soft (plastic, or rubber) mallet.

I'd replace the pins & rockers. There's a chance that they are tweaked and new replacements cheap.

If that's a K0 engine, it will not have a neutral switch above the countershaft.

SL70s were 4-speed/manual clutch motors, pretty much the same as a CT70H but with a different shift pattern...and slightly higher factory hp rating.

 

[kirrbby]

You should be able to tell whether the pin is sticking/dragging on the rocker bore, or the bore in the casting. Might help to know what you're fighting.

 

[Tripod]

Be sure to thread in the puller as far as you can so it can grab onto as many threads as possible. If its really stuck you could pull out the last thread if thats all you grabbed.

 

[Mellis4949]

Success! The main thing I was missing was the spin/rotation motion while pulling outward on the rods. The first head I pulled these pins from came out so smoothly. These seemed stuck but threading the bolt in there all the way and continuing to spin out was the trick. Thanks guys!

Now I am staring to put things back together and working on wiring. More questions to come I am sure!

 

[Mellis4949]

The top end on my first (red) bike is done and the engine is back together, so now I am excited to begin putting parts back on instead of taking them off!

I took a look at the main wiring harness and it has been hacked into pretty good. I have a wiring diagram and am carefully working my way through that, but some of the wire colors don't match and there are (poorly done) splices all over the place. I'm ordering a new complete harness from Trail Buddy, but in the meantime I wanted to check for spark. Let the fun begin...

I learned a lot from this thread: https://lilhonda.com/index.php?threads/ct70-basket-case-no-spark.22912/ so thanks everyone who contributed to that!

My coil wire to the spark plug had been cut and it was missing the spark plug cap connector. I got the NGK splice connector and connected a new plug cap to the damaged plug lead. This was pretty simple and I am not worried about aesthetics yet. (I will shorten it too!)

I have a lightbulb probe tester that I grounded to the head and probed the stator connector main ignition wire, and the lightbulb lit up when I kickstarted.

I then ran a test lead from the black primary ignition coil output and connected it to the black coil wire, touched (grounded) the plug to the head and kicked it... Nothing.

So then next I think it must be the coil, but I understand that they rarely fail. I get a bit stuck here due to my lack of knowledge of electrical and the use of a multimeter. Racerx kindly explained that the coil could be tested:

"HT-to-ground resistance should be 3 megohms (minimum), primary-to-HT should be 5K to 15K ohms. A direct short should manifest as an ultra-low impedance (resistance) number, an open coil will have no continuity. "
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I set my meter to ohms and zeroed out the needle. I wasn't sure if "HT" in racerx's description is the coil wire/plug cap, but when I touch one probe to the spark plug cap and the other to the head (ground), my meter shows 10ohms (megohms?); then the main (only) black wire out of the back of the coil (the primary) to the other end grounded to the head (a short?) measured basically 0ohms - no resistance. The final combination was the primary black on one probe and the spark plug wire on the other measured at 10ohms. So, I am thinking that the coil is good - Seems to fall into the ranges described as I understand them.

I tested each of the 4 wires coming off the stator and only one out of the four lit the bulb in my tester, and that is the one that I assumed is the ignition coil - not sure if that is accurate and I need to learn more about the stator/points/condenser because I don't just want to throw parts at it. I did take a little sandpaper and ran it over the points, but otherwise I haven't done anything. I thought that the lightbulb test was encouraging, but I don't understand why there is no spark if all of the elements I described seem to be in order.

So that is where I am! If I can get spark then things will start to get interesting. Thank you all for participating and contributing to this forum. During this very weird time with Coronavirus I find this new hobby of mine to be extremely fulfilling because I can turn off all the other noise and do something I feel to be constructive and fun rather than get dragged into the mire. I appreciate you.

 

[Tripod]

Set the meter to ac volts and check the black wire out of the magneto harness. If theres no volts its either points or condenser. If your getting voltage but no spark, look into the coil.

Its wise to take care of this now. Get your coil squared away before the fuel tank and hoses get run. The coil can be taken out from the top, but it requires tiny hands. Its much easier if you decide to drop the engine, best to do when engine is out. And shorten the coil wire too as that area runs out of room pronto.

 

[69ST]

Yes, "HT" = high-tension, i.e. the sparkplug lead.

This all comes down to one very simple, basic, test that anyone can perform...no tools or equipment needed...pulling the sparkplug and cranking-over the engine. If it makes decent spark, you're probably good to go; if not, the cause is going to be a single component. And coils rarely fail. Those that have croaked usually have some clear visual injuries.

 

[Mellis4949]

My new coil from TrailBuddy came in and so I was able to install it and resume working on getting spark...but I am stuck. Initially I took my lightbulb tester, grounded the clip to the head, and probed the hot lead wire from the stator. When I turn the engine over using the kickstarter I get the lightbulb to light up. However, when I run a clip connector from this same wire to the wire coming out the rear of the coil (then ground the spark plug to the head and turn it over), I do NOT get spark. I think my (new) coil is good, but I don't understand why I can get the lightbulb to light, but no spark. I am bypassing all the other wiring by connecting the stator to the coil, so there shouldn't be many other variables I am missing. Could it be that the ignition coil in the stator is producing something but not enough to translate to spark at the plug? I might just need Captain Obvious to give me some tips.

 

[allenp42]

If possible, please post up a pic of your stator. If the parts are new, you just may need to clean the points again. For what it's worth, cleaning new points is required and some are a little more stubborn than others to get the protective coating of oil (or whatever) off the contacts.

As far as cleaning, Brakleen seems to work a little better than "technician in a can" (electronic contact cleaner).

This is just a starting point and the most common problem. There are other things that can cause you not to get a spark.

 

[Mellis4949]

Thanks allenp42!

It is a Mitsubishi stator. What is confusing me is that I do get a reading (bulb lights up) when I probe the lead. I bought new points and condensor online but they were very cheapo parts, and those are what is pictured here. I "think" I did okay soldering the condensor on. I have not really adjusted timing/set points yet. I did take some fine sandpaper and run it over top and bottom of the new points, then sprayed with engine parts cleaner per your earlier suggestion, but still no spark.

 

[Mellis4949]

Argh! So in reading online I am discovering that I put the wrong points and condenser in. I have a clutch (CT70H) and Mitsubishi stator, not the Hitachi. Early on I purchased points and condenser for the Hitachi before I knew there were two kinds. I guess that is one way to practice soldering! The good news is that the other bike has the Hitachi, so I can save the parts for when I get to that one.

 

[allenp42]

You can use Hitachi points, at least new OEM Honda or NOS Daiichi points in a Mitsubishi stator. However, the condenser is different between the 2 and are NOT interchangeable. A Hitachi is too large to fit into the well and the screw mount is no where close for a Mitsu stator. The felt pad does look a wonky. Is it facing the cam lobe? It may be the pic but looks like it's touching the crankshaft?

Regarding your points, is that a small crack I see on the movable edge of the points? Even your rub block looks a bit rounded on the edge?

For what it's worth, I have had problems with cheap points. I have 2 brand new sets in front of me that look fine but will not work. One has a weak spring and the other has a bad connection at the rivet that connects the spring steel band at the rub block. I could not get a spark with either of the sets.

I've attached a pic showing the physical difference between mitsu and hitachi condensers. You should be able to tell which version you have.

Just as info, the multimeter you have will not work to test stators, points open vs, close etc. Your meter only has the ranges X1k and x10. You need one that has x1 (no k). You can only test that you have continuity with that meter, and will not be able to determine if something is shorted to ground or if the points are open or closed. The coil should should a resistance of ~1.3 to 1.4 ohms with the points open and less than ~0.3 ohms closed.

With all that said, order a new set of points and condenser and your problem may go away. But be aware, new OEM honda points are about $40 + shipping.

 

[Mellis4949]

Thanks @allenp42! I can't tell you and all the guys on here how much I appreciate your help and advice...especially for someone like me who is just scratching the surface (but having a ton of fun) with these bikes! I especially appreciate your comments on the multimeter - that is exactly the guidance that comes in handy for me.

I've learned that the Mitsubishi condenser is much more rare than the Hitachi...and I had to look very carefully to be sure to get the right part (DRatv) was the only place I could find any in stock (July 2020).

Another tidbit - the cheapo Amazon condenser (didn't work) but was the same diameter as the original (branded with Mit logo) one I took off (even though the angle in the pic is bad) and there are 2 bracket hole choices which is how it fit for me.

Thanks also for the comments on the felt and placement. I had sort of shoved it on there and it wasn't right. You mentioned that the points are most likely interchangeable between the stator types, and I did notice that the set that I bought said Mitsubishi on the box...so those "might" actually work once I get the correct stator. I bought some more, higher quality, points anyway.

Okay, now to tinker and basically do some parts cleaning while I wait for my order to arrive! I am hoping that with this correct replacement condenser and points (and new coil) that my ignition system will be working and I will have some fire. I've got new valves and I went through the top end...about 45-60 days into this and I am looking forward to a little more substantial progress!

 

[allenp42]

cheapo Amazon condenser (didn't work) but was the same diameter as the original (branded with Mit logo)

A LOT of the aftermarket condensers are smaller in diameter than their respective oem version. Yours is a first where I have seen a 2nd hole mounting in the bracket. Did it arrive this way or did you drill or modify it it fit?

Regardless, a decent Quality aftermarket Mitsu condenser and good set of points should (hopefully) take care of your problem. Just don't forget to clean the points to remove the lubricant prior to installing.