Saving one from the dump!

Hey all, new to the forum and wanted to start a thread on my CT as I've got ALOT to do and will definitely be needing some help along the way!

I had 2 CT70s, a K0 and K1 and due to finances had to sell them. Of course I regretted that and after missing the days of ripping the bikes around I decided to pull my last CT, a 1970 parts bike out of my boneyard. Used and thoroughly abused it was froze up, no carb, no wiring, loads of spray paint among other issues. I decided to do my best to bring it back. Got the motor free'd up, new coil and (China) carb, fixed the condenser wiring and got spark. Set timing, did some odds and ends and went for a start...no love. Checked compression, nada. Adjusted valves, still no compression. Finally gave up on here running and after some diagnosis of a compression tester that was faulty I decided to pull the top end.

What I found was compressed and froze rings, to the point I had to break them off in addition to leaky valves. After much deliberation on how much I wanted to invest in the heap I decided to go all in and order an 88cc kit from Dr. Atv with new head as well. Then after evaluating my fork situation I splurged on a new disc fork setup. The kit should be here tomorrow and the fork following so I'm gearing up. I've done 2 stroke top ends before but this will be new to me. The disassembly went smooth and I gained alot of knowledge of things I'm not familiar with like cam, chain, valves etc. so I'm excited. Just wanna do the top end properly considering how much I have invested in a bike that was destined for the scrap yard.

I was going to refurb the frame that was pretty severely damaged but found a Honda replacement frame in great shape for a great price! Couldn't be happier. Thanks in advance, can't wait to discuss the rebuild!

What I'm looking for is some guidance on the top end rebuild.

HMC_MT said:

What I'm looking for is some guidance on the top end rebuild.

Click to expand...

Welcome to lilHonda HMC_MT. We can definitely help you with the top end. I'd recommend buying only known, good quality parts. If the price seems too good to be true, it probably is. Dratv, & tbparts are our go-to's.
But we would always recommend splitting the cases on a bike with more than...maybe 3000 miles on the odo. The shift forks are a common wear item that will cause shifting issues. The clutch should be pulled and cleaned at a minimum...and a look under that clutch cover can VERY often show you a problem...including damaged gears and such. (Metal schrapnal will typically end up laying under that right side cover)

...I reread your first post...you have your parts already...and you must have already been into the clutch side too.

http://dratv.com/howtoputrion.html

http://dratv.com/ringgaps.html

http://dratv.com/infoonfitment.html

Be sure to inspect your engine cases for stripped threads while the engine is out, worn damaged frame mounts...rear lower stator cover mount hole is commonly stripped and/or broken.
Look to see if the engine mounting holes on your new frame are in good shape, and there should be 3, welded in spacers on those holes. Look close for stress cracks on the frame in the area of the triangular hole above the engine.

Thanks for the feedback kirrbby, engine is off the old bike and starting with a good inspection and getting it as clean as possible while its not mounted. I'll check everything listed above but I'm not gonna split the case at this point. It's a low mile bike and the cylinder was almost perfect, head and cylinder is off. The bike was timed perfect and got spark sorted out before the teardown. Typical lower stator cover mount hole is broken. Here's what I've purchased...

http://dratv.com/88ctalalc7.html

http://dratv.com/hewivain.html

https://mytrailbuddystore.com/ct70discbrakeassemblylevel230mm.aspx

New coil, plug and Chinese carb

Decided to just go for it and get the sweet disc fork. Also got a bunch of odds n ends. Quickly realized the kit didn't have a new cam but was told by a trusted guru I can use the cam I have. My ? is should I get one more appropriate for the kit? Is it a game changer? Cam chain and cam sprocket I have are in good shape. Step one is gonna be getting the rocker arms and cam out the old head and inspect. Never done that before. I'll do some more work here and report back...

Thanks!

Been working on her most of the day, going well. Cam and rocker arms look real good so I'm using those. Barely any lateral crank play. Got rings on without any breaking, looking into orientation as we speak. My piston doesn't have any markings for intake side or anything so I'm hung up there. Is the bigger divet on top of piston intake side then? Also trying to nail down how cam should be when putting the sprocket back on. Dot orientation in relation to everything else.

"Is the bigger divet on top of piston intake side then? " Yes,it's a bigger cut out because the intake valve is larger. Also the dimple on the left side of the picture on the piston is for sparkplug clearance. With a razor blade try to clean up that cylinder to case gasket surface. Be careful not to gouge the soft aluminium. I use CRC gasket remover. Might be best to spray it into a cap or something and brush it on- it will remove paint if your not careful.

Yep, definitely cleaned that gasket material some more. I'm going to drill out the oil port 2mm before I put the top end on and order a high flow oil pump. Got the piston orientation sorted but still slightly confused by getting my ring gap orientations all right. In addition not sure how to line up cam/cam sprocket. The dot on sprocket goes where and when?

If you go to Dratv website click performance parts section then what fits what section it shows various ring orientation. The dot on cam sprocket lines up with notch in head next to cam sprocket. Piston needs to be top dead center when installing cam chain. Sometimes have to turn cam a little to line up with sprocket holes.

Appreciate the link. Drilled the oil port to 2mm now putting the top end back on and I'll be ready for a new oil pump. Oil slinger cleaning too and clutch inspection along with making sure I've got these o rings/gaskets right from the kit.

Engine is done but I forgot to order a clutch cover gasket. Doh. Moving on to disc fork install. Anyone have a link for getting the aftermarket race/bearing all correct?