Big Boy's Bike

[J.P.]

Okay here's my background posts, but I'm wanting so experienced eyes now to help me see any problems.

Tear it up, fix it, repeat: Boys and their toys

Tear it up, fix it, repeat: Compression??

Tear it up, fix it, repeat: Trail 70 Clean up

Tear it up, fix it, repeat: Trail 70 Stand

Trail 70 Stand Teardown


Up and onto the table. That was a chore to get it up on here by myself.



Left side off again.


Four bolts hold the pegs and sidestand.


Rear brake springs need to be out of the way.


I figured I would break torque on all the case bolts while it was still in the frame.



Here's my advice about this little impact driver from Harbor Freight. It's the only thing that will fit on some of the heads on the case, but I beat it to death on the tough ones. Use the little one when you have to on these bolts on get a bigger one for the others. Wear gloves. Get a real 2 inch long #3 Phillips, not bit holder and short bit. You loose impact with the extra pieces and the extra bit is now stuck in the little impact. I think my little impact is now junk, but the case all, but apart and I'm only out like 7 bucks.


I believe this is the only case screw that can't be turned a bit with the engine in the frame.


A long bolt holds the left side head cover.


Three screws hold the cam gear.




Three acorn nuts and a regular nut hold the rocker cover. I have no idea why they have the mismatched hardware, but it's correct.



Rockers.


I removed the bolt that holds the head to the cylinder. Tap with the ghetto mallet and the head comes off.



The head should come off with the engine in the frame, but not quite?


Let's try it with a flat front tire.


Perfect!


Wow, look at the carbon on that piston.


A little bolt holds this camchain roller.


Here's the compression leak on the exhaust valve.


Little oil seal here.


Bolt for the cylinder to the crankcase.


Cylinder comes off.


That piston is so cute.


Little oil seal here.


Strapwrench on the rotor to break the center nut loose.




Pull the rotor puller into the rotor. The big threads are left handed.



Hold the outside turn the inside.



The stator/magneto. Seven screws hold this together. Don't loose the woodruff key. Oops, too late, oh there it is.




Two bolts and a keeper hold the front sprocket on.

 

[ez50]

Keepem commin JP. We all like pics

 

[69ST]

Looks to me like your project is well on its way, nice photo essay too. Your motor looks pretty good for a raw-state teardown. The flywheel & stator asm are remarkably clean & free of rust, the piston skirt looks fairly unmolested. Both are good signs (but not guarantees) of what's likely awaiting discovery inside the motor.

Your impact driver experience is not unusual. It's tough finding a good one, the cheapies end up beaten to death. You wouldn't believe how well a top quality impact driver works. These days, of course, they also cost real money. If you're only ever going to rebuild one engine, the only way you'd recoup the cost is by not damaging something during teardown. Since you've gotten this far without breakage, you've gotten your 7 bucks worth...gotta be a lot less than a shop would've charged to remove the old screws.

You still have a few workstand-related discoveries ahead. Based on what you've shown so far, I think you'll figure out some things that work well for you and enjoy the process. To this point "ya done good, kid!":21::41:

 

[NJBphotography]

good info, love the pics! should post this up on minimayhemcrew.com also!

 

[J.P.]

CT 70 Head and Valve Teardown



Big boy takes off the tappet caps.


The right side cover comes off with screws, since the long bolt is already gone.





If you look really close you can see the threads inside rocker arm pins.




I forgot the thread pitch, but at this point plenty of bolts are laying around. The footpeg mount bolt fits.




Screw it in and pull it.







Okay, I should have pulled the tappet adjuster screw and lock nut, before the rocker arm pin, but it still comes apart okay.







Now the valve spring compressor.









When the spring pressure is off, then the keepers come out.







Here's the exhaust valve components. I need to check all the free lengths on these springs, to see if I can re-use them.




Exhaust valve is dirty, but seems reuseable. I'll see how they lap out.







The pad on the rocker is terrible. I'll need a new one.




There's a collar one and seal the exhaust side only.




Bag and tag.




On to the intake side, here's the rocker arm pin.




Intake rocker is smoked, too.




Cam falls out.




Seems good enough to be re-used.









Here's the intake valve guide. It doesn't take the collar and seal, like the exhaust.




Exhaust valve guide.




Exhaust valve seems to be useable.

 

[J.P.]

CT 70 Splitting Cases



Two bolts hold the engine in the frame.
First one.


Other one.




Out.



This is the last case bolt to break torque on.



I pulled one wrist pin keeper and the wrist pin and piston come off.



Here are the right side cover and left side case bolts. I have list of the bolt sizes and they will be replaced with stainless socket head bolts. (This was way too early to take out the case bolts.)








Here's the right side cover off.


Clutch stuff.






Oil screen is clean.



Shifter stuff.



Camchain tensioner stuff. There should be a metal rod and a rubber end in there some where to.



Now to build the box to hold it.



It seems every OHV single engine builder has one, but no one knows how big they should be so I figured 4 inches by 5 inches on the inside. 5x5 would have been okay too.





I bought a new bigger impact driver, but the inner stator plate screws still won't bundge. I should have gotten these while the engine was still in the frame.



I decided to try the clutch side. I was figuring using the penny on ribbon to lock the clutch basket and primary gears. I couldn't get it to lock, but it didn't matter.



I think I screwed something up working on the wrong screws. All this mess locked up the clutch basket.



These are the first screws that need to come out. They should have come out with the engine in the frame.




I have to quit buying Harbor Freight tools.



Finally off.



Unbend the tab washer.



Special socket gets the castellated nut off.





This is some nasty sludged up yuck.




Okay, this is a mess. The clutch basket should come off as an assembled unit.





When I impacted the wrong screws, and the snap ring came off and this got bent up. I need a new one.



The rest of the clutch.





Missing one spring it seems.




It might in here somewhere.



Snap ring on the drive gear.




Loosen this bolt and disconnect this spring.





I didn't get a good picture off the shifter mechanism, but I think I want to replace this spring, just in case.




Back to the stator plate. Stubborn, stubborn, stubborn.



Barely got this one out, but it's out.



Still stubborn with no screws left. I finally got it off, and used p-oil on it, too.



Two o-rings under here, too.



Seal in the middle, o-ring on the outside.



Here's the rod and rubber pad on the tensioner.



Plug over the shift drum.



Shift drum nut.



Cases split!



One more screw holds the other end of the shift drum.




This coating seems out.



Gears and shiftforks look good.

 

[J.P.]

[h=3]CT70 Valve Lapping and Head Build-up, plus some[/h]
It's been a very long time since I have worked on the Trail 70 for my big boy. The Shovelhead shelled out real bad right after I got the Trail 70 torn down, so it sat under a blanket on my bench for over a year. I wouldn't have torn it down if I had known it would sit so long. I would have waited, but I'm glad I took a lot of pictures of the teardown. Any how...

I'm going to lap the valves and rebuild the head first. It's a good place to start.


The exhaust valve port is nasty so I want to clean that a bit.


Baby boy helps clean tappet covers.


Lapping compound on the exhaust valve.


Slide it in.


Big boy gets a lesson on valve lapping.


On to the intake valve.


I think that's good. So I need to wash all the lapping compound out of everything.


I think that looks good.


I'm going to Simple Green soak the bare head to try to get the oil and dirt off of the fins.


The valves go into the oil bag to stay rust free for a day or two.


The head is looking better. I should really mask and bead blast the thing, but it's clean enough. Here I am again taking a clean part and covering the steel parts with oil.


Here's everything you need for the exhaust valve. The collar and seal are only on the exhaust valve and not the intake.


Valve goes in.


New seal going into the collar.




Collar onto the valve stem and guide.


Springs on.


Top collar on.


Now to the valve spring compressor.




These keepers are extra tiny.


Good to go.


New intake valve and old hardware.


Valve in.


Springs.


Collar.


Keepers in.


Both valves in.


Time for the rockers and tappets. The rocker shafts are threaded on one end to help you take them out. It doesn't really help going in though. Brand new OEM rockers, too.


Looking good.


Here's the tiny tappet and lock nut.


I put these in kind of loosely, because I know I will have to adjust them in time with the motor later.


New o-rings in the tappet covers.


Again I just put those in loosely because I will back into them.


Add this oil routing cover with a new gasket.


Looks good.


The long bolt is just hanging out. The cam and cover will go on later.


I was just about to put my tools up and put the blanket back on everything, when I found these on my bench. They aren't bagged, but look important.


I thumbed through the parts book and these looked right.


Luckily the other two were where they were supposed to be. So it's good that I found them.


One more thing, this cover was painted originally but looking rough now. So it will head over for powdercoating to new cooler finish. This clutch thingy needs to come off though.


Looks like a seal goes here, too. Hopefully that one is in the gasket kit that I bought.

 

[Adam-NLV]

Great photography! Thanks for showing your engine re-build. It's interesting and a little scary, so many things to remember and to get right, the first time.

 

[theraymondguy]

The "shift star" should be taken before splitting the cases - generally, the engine is laid on it's left side and the rhs case is to be 'lifted' off of the left when splitting, keeps any spacers etc. in place.

In your picture of the exhaust valve parts, I didn't see the valve spring seat part# 14776-028-000... maybe it's stuck on the valve stem seal cap?

 

[vwbusman]

Nice pictography of a tear down and rebuild

What happened to your shovelhead ?
I had a healthy '77 and basically ran it into the ground, sure miss that clapped out beast, my '90 Evo FXR Sport pales in comparison.

 

[J.P.]

[h=3]CT70 Crankcases going together [/h]
Time to really go back together with the motor. I cleaned up the cases with Simple Green soak and an electric toothbrush. Clean enough. I found this busted boss on the left case.


It seems to match the busted spot on the stock left side cover that I was going to replace.


There has to be a real way to fix this, but this is what I am going to do. QuikSteel. It's not truly structural and I just what something to hold a bolt to fill a hole in the new cover.


Knead it up and fill in it.


DISCLAIMER: The rest of the efforts documented here are not chronologically true for my build. I had to try stuff, back up, and try stuff again. This documentation is how to do things correctly the first time.

Now onto getting these cases together. Here's the way the kickstart shaft fits.


The old kickstart shaft is still in the right case. I need to get it out of the case and get the gear and retainer off of it to re-use them.


16mm snap ring goes first. The retainer and spring come off.


Gear and shaft slide off. This is what I discovered next, the splines to the left of the 20mm thrust washer and snap ring are bigger than the 20mm. So everything has to come off to the right and then be re-install from the right as well.


New shaft and everything else new I need.


New 20mm snap ring on the left end of the new shaft.


17mm washer off. Then the 17mm and 20mm snap ring come off the old shaft.


Here's the gear off shaft with the ratchet spring. I bought a new one, but I don't think I will use it.


The 20mm washer off of the old shaft onto the new shaft.


Gear on the new shaft.


Another new 20mm snap ring.


It fits in the case like this. The 17mm snap ring and thrust washer shouldn't this sit in this high.


It should be down here.


Like this. The thrust washer sits on top of the ring and against the other case.


Here's part of the transmission diagram. Note 11 and 12, they look the same, but one is 13.5mm and the other in 14mm. It makes a difference, trust me.


See they only fit one way.


The shift drum, forks, and gears go something this.




Drop the whole mess in like this.


The mainshaft still needs a few more pieces. This funny washer.


Another gear.


Spacer.


Then the proper washer. This is the smaller washer. I know the big one is already in place, this will fit.


Getting closer, but not quite. I decided to slip the other case on temporarily to work on the outside of the left case.


I figured I would pull these old seals.




Flip things back over and of course I have to find all those shift drum pins again.


I had to make sure that this thrust washer was in place.


Here's the gasket.


This piece needs cut off.


Now the right case can go on and flip it over to put the case screws in. Four screws, three medium, and one short one. As near as I can tell, the medium screws go here.


The shorty goes on the back.


And these are the long ones.


Together.


New seal here. If you bought all the oil seals, double check the part numbers to make sure it's the right one or you may ruin the wrong seal and need to buy another one for the rotor.


This bolt goes into the shift drum.


And the cap.


I just barely laid the the shift lever stuff in because I wanted to play with it a bit and I wanted to capture those stupid pins. I somehow forget to order a new shift shaft, so this part is on hold until I get a new one.


I can pretty much finish the kickstart shaft. The spring and retainer slide onto the splines. The retainer needs to catch the corner on the case.


Pull the hook end of the spring onto this catch.


The retainer needs to slide down enough to slip the snap ring into the groove.


Oil pump next. For whatever reason I didn't get picture of the tear down, but it's really simple. Gasket here.


Body and screws.


Make sure the whirly gig parts are in there and they are spinning with the sprocket from the other side connected to the camchain.


Gasket.


Cap and screws.


Onto the clutch side cover. This the inside of the clutch adjuster. The pin makes it dummy-proof.


New o-ring here. Here's a look at the powdercoat. "Wrought Iron" not as black as black wrinkle, but not smooth. I think James wants the bike to be black so I don't want all the accents to be too black.


Locknut and washer just on loosely at this point.

 

[J.P.]

The "shift star" should be taken before splitting the cases - generally, the engine is laid on it's left side and the rhs case is to be 'lifted' off of the left when splitting, keeps any spacers etc. in place.

In your picture of the exhaust valve parts, I didn't see the valve spring seat part# 14776-028-000... maybe it's stuck on the valve stem seal cap?

Yeah, figured the easy after I tried it all wrong. That's seems to be a reasonable question. I looked it up in the parts book to see what it was and I'm not sure.

Nice pictography of a tear down and rebuild

What happened to your shovelhead ?
I had a healthy '77 and basically ran it into the ground, sure miss that clapped out beast, my '90 Evo FXR Sport pales in comparison.

A rod bearing crapped out bad. The bottom end was supposed to be "professionally" built with receipts.
Bottom end loose rod - YouTube

I had Truett and Osborne rebuild the bottom end and set it up as 93 incher. Now the 4 speed crapped out. Luckily the transmission is the lasted professionally build piece on that bike.

 

[J.P.]

[h=3]CT70 Shift Shaft Install[/h]
I'm going to need to back up just a bit and pull off the stopper plate or star plate. The only reason I put it on temporarily was to keep from me losing the shift drum pins.


As I lost and found and lost and found the swift drum pins, I noticed this pin does not go in as far as the rest. I thought that was odd.


However, it matches a countersink on the star plate to idiot-proof the gear drum timing.


You can see the countersink on the outside of the star plate, too.


On to the shift shaft or gear shift spindle. The old one(top) has this build-on washer. The new OEM Honda one(bottom) does not have the washer.


The parts fiche shows that it is the list part number and shows no washer, so I assume this is redesign and will work okay.


Another bigger picture of the difference.


This a new Honda OEM shift arm and spring. I really didn't need a new arm, but I accidentally bought one when I thought I was buying the shift shaft.


New shift shaft and shift arm together. The old set still has the spring on it in the background.




The spring goes on like this. Dratv.com didn't have a new one of these springs available so the old one will have to do.


This stopper arm and spring need to be removed and reinstalled properly.




Another new spring.


Shift shaft goes in.


Now the stopper arm and spring goes on.


Even Honda's need some loctite.



Stopper plate on.


I went through the gears with the shifter. It's not as smooth as I would have hoped and it kind of wanted to hang between gears. However if I spun the input shaft a bit after every shift it shifted better. Hopefully it will shift good once the engine and transmission is spinning.

 

[J.P.]

[h=3]CT70 - KO Centrifugal Clutch Build up [/h]

Time get most of this clutch built up. The manuals I have for this leave a lot to be desired. There are too many versions of centrifugal and manual clutchs on 50cc to 90cc Honda's and every manual covers all of them in unsteady and unclear detail. I also believe that the CT70K0 is a one model version too. So it took a few tries to come up with this, the pictures are a little out of chronological order, but as presented should be correct to do it right the first time. If you know more than me and spot a screw up, please let me know.

The big gear goes on the transmission input shaft.


Double check the part number on the snap ring.


Install snap ring.



How the clutch should look. ???!!!!????


This view should help more.


This gear(17) goes on the crank. The smaller gear part up.



I never disassembled parts 1, 10, 11, 13, and the screws and washers. Notice these screws are clearly marked with a dot as JIS. I had thought those didn't come onto the scene until the 80's, but actually I believe all of the screws on these Hondas are JIS.


I found eight of these little parts(23) after my first build up attempt.


I couldn't find any good explainations in any manuals, but looking at the parts diagram I think this is correct and they need go in close to the first of this build-up.


This is 16, 4, and 22. I didn't take these apart so I shouldn't need a new snap ring.


That assembly lays right in here.(The rollers(23) should still be here in this picture, too.)


The steel plate with the fingers(7) goes on next.(The rollers(23) should still be here in this picture, too.)

F
riction plate(6). These aren't great, but runnable for now.


Steel plate with knotched ears(9).




Another friction plate(6).



Four new springs(12), because I lost one tearing it down.


Springs(12) go onto the fingers of 7.




Steel with holes(8). This piece is not pretty but runnable.




Retaining ring(14) holds it together.



Flip it over and put it on the crank.That's a good stopping point for today.

 

[J.P.]

[h=3]CT70 - K0 Top of the Clutch and Right Cover[/h]
Time to finish the clutch and get the rightside cover on.

I still need to install 20, 19, 3, 2, 27(X3), and 28 to finish the clutch up. The washer(21) wasn't there when I took things apart so I didn't put one back in.



Special tab washer(20).


Castellated nut(19).


There is a special tool to hold the clutch basket to torque the castellated nut, but I don't have it. I could use my penny-on-a-ribbon to lock the gears, but the Clymers manual suggested using an extension in the wristpin bushing to hold things still.


Special socket for the special nut.


Torque to about 30 ft*lbs.


Bend up a tab of the tab washer.


Gasket(3) and Outer Clutch Cover(2). Finding the right position for the gasket is a trick.


Getting it all aligned on clutch is a trick, too.


I tore up one of these screws(27) and I thought I bought more from Dratv.com, but I didn't. Luckily I found some allen-style replacements at Ace Hardware.


Drop the bearing(28) into place and now the clutch is done.


Now the right side cover can finally go on.


Clutch cam plate(5) goes on.


Clutch lever(4) goes on the shift shaft splines and into the cam plate knotch.


"Oil through"(10) and spring(11).


Those slide into the middle hole.


Ball retainer(9) and spring(6).


The spring is under the ball retainer.


Dowel pins(19) for the outside cover.


One here.


Other one here.


New oil screen. I probably could have cleaned and reused the old one, but what the heck.


Slides into the case near the oil pump.


Gasket(2) in place.


Right side cover goes on. I already assembled 1, 14, 12, 18, 8, and 7. Check out the bottom of this post.


Two long screws(17) and six shorter screws(16).


Long ones go here.


Put the shorter ones everywhere else. Tighten all in a crisscross pattern.


Whoa. This one bottoms out before it's tight. It's sharing a threaded hole with this case bolt. I guess my stack up tolerances got me or maybe that wasn't the correct length case bolt that I used.


At any rate a little time on the belt sander and this bolt is now the perfect length.


I thought I had a decent dipstick(3), but I didn't really. The stock is broken(right) and the junkyard special is nasty dirty(left).


Use the broken on for now and soak the better one in dawn and see how it cleans up.


Flip the motor over and install the shift shaft seal.


This is a "special 1/2 inch drive 15mm deep well seal driver."


Perfect.


Flip again and install the kickshaft seal with the same tool.


The right side is mostly done. The piston, cylinder, and head should be next.

 

[bc17a]

JP,

That clutch looked a bit grungy when you put it back together. I like to have a bucket of mineral spirits handy to make sure everything is squeaky clean. Also, the shift drum threads looked oily, loc-tite likes clean dry threads so don't be surprised if the shift star screw loosens up on you in the future. Just my .02 cents. Other than that, nice work.

 

[J.P.]

JP,

That clutch looked a bit grungy when you put it back together. I like to have a bucket of mineral spirits handy to make sure everything is squeaky clean. Also, the shift drum threads looked oily, loc-tite likes clean dry threads so don't be surprised if the shift star screw loosens up on you in the future. Just my .02 cents. Other than that, nice work.

Yeah, probably could have cleaned up those friction plates a bit. Not big as today's screw up when I put the rings on all wrong and didn't know until I had built the thing.

 

[J.P.]

[h=3]CT70 Piston-Cylinder-Head-Genny[/h]
Here's the cylinder parts diagram.


Here's the first panic of the day. My universal gasket kit had this wrong, but close, base gasket.


Luckily, I little more digging through the gaskets and I found the correct base gasket(4).


A little pre-planning and checks first. So here's my the seals, gaskets, and parts that will need to do the job.


This is the top of the piston. One book and dratv.com say point the arrow. It seems odd, because that means the bigger valve cut away is with the smaller exhaust valve.



Okay this is where things got out of sorts the first time I put this together. One books shows this and I couldn't find anything else at the time. The rings I had were square and black and double beveled copper color with silver edge. I compared the rings on my old piston and the beveled ring looked to be the middle ring. I was wrong.



I put the whole topend together and then I found the proper instructions with pictures on dratv.com. I stole them and put them on here. Hopefully they don't get upset about that. I spent a lot money with and give a lot of free ad space if anyone is following this build. Also I didn't document my re-teardown and second build-up so if you see the rings wrong in the rest of my pictures know that it's been taken care of.






Okay, back to my work and pictures. Install one wristpin keeper. These are always a trick.



Base gasket(4) and dowel pins(14) go on.


Moly grease into the rod bearing.


Assembly fluid on the wristpin.


Wristpin into piston from the side without the wristpin keeper. Just enough to stickin through to caught the rod bearing.


Line it all up.


Push it in. It's tight, but once it starts to move it will go fast.


C-clamp and sockets squish it in the last little bit.


Go deep enough to find the other wristpin keeper groove.


Work in the other wristpin keeper.



Oil seal(10) goes here.


Oil up the piston and rings.


The book said the rings could be pushed together and the cylinder(3) installed by had without a compressor and it actually worked.


Cylinder(3) on.



Holder bolt(9) goes here.


Camchain diagram.


New parts. Camchain(2), and rollers(4 & 12).


Camchain routing starts here.


Routes through here.


Roller(4) goes here.


Roller(12) goes here.


Funny bolt(13) and washer(19).


They go into this hole and through the roller(12). The chain runs on both sides of that roller.





Notice the piston at top dead center(TDC) and how the keyway on the crankshaft lines up to it.
This how you find TDC when the rotor is not installed.



Back to the first diagram. Headgasket(6), dowel pins(15), and oil seals(12 & 10).


Moly grease on all the cam and contacting surfaces.



Cam goes into the head. I had to pull the tappet covers and tappet adjusters to get it to find its home.


Now to the camgear(1 on the camchain diagram). Notice the "O" mark the lines up with the "lonely" hole and is perpedicular to the center line of the inline wholes. That is the TDC mark for the cam and camgear.


It should be inline with the keyway of the crank.


Position the cam in the head to match the thread holes to the holes of the camgear.


Slide gear and chain into the head and the head onto the cylinder studs and cylinder.


Another keeper bolt.


Adjust the TDC marks and install all three the camgear bolts.


Head cover diagram.


Gasket(5).


Cover(1).


Nuts and washers. I'm not sure exactly why, but the acorn nuts go with the steel washer and the regular nut goes with the copper washer. The regular nut and copper washer go on the bottom right(looking from front).


The regular nut and copper washer go here.


The acorns and steel washers go everywhere else. Crisscross torque pattern.


Long cam cover bolt. Goes in...


and through.


The tab on the camcover goes between the two tabs in the head on right.


Gasket and camcover go on and the long bolt threads into it.


Looks a little more like a motor now.



Spark plug wire guide goes here.


Camchain tensioner diagram

New number 11.


Looks better than the old one. Put it into number 8.


Slide that assembly into the case.


Add 6, 10, 18, and 16.


Looking good and holding things tight.


Generator/ignition diagram.


New o-ring(16) and seal(15) for the stator plate.



These caulk spots are sealing though holes.


New little o-rings(17).


They go here.


The plate goes on like this. There is an upside and a downside be careful.


ACE Hardware replacement screws again.


Four long screws(20) hold the stator coils(11) in place.


A screw(19) and washer holds the condenser(4).


A screw(19) and washer here for the points breaker(2). I'll adjust that later.


A screw for this clip, too.


Key goes in the keyway.



Rotor(9), washer(14), and nut(26) go on.


Hold the rotor and torque the nut.


Getting there for sure

 

[bc17a]

JP,

The sealing washer goes on the other side of the head where the oil flows. The plain nut takes a steel washer.

 

[J.P.]

Well I do agree that all the o-rings are bottom left(facing the end of head), but I was working to this manual. Is this manual wrong, too? Not the first wrong manual I found though.