Holy crap. From the ground up.

[emacklin]

So the bike blew up.<br /><br />I blew a piston about halfway through a cross country trip this summer, and I'm gonna need a lot of help in getting everything back together.<br /><br />In an effort to diagnose the problem, nearly the entire engine has been pulled apart, except for the bottom end.<br /><br />The bike is a 1966(67?) CB77 Superhawk. Or at least what's left of it....<br /><br />I got my hands on a clymer manual, which will be sitting next to me when I get a chance to fly back out to Minneapolis (where the bike is sitting)<br /><br />but I'd love to hear any tips you guys have, or any instructions from someone besides the writers at Clymer, for a little more clarification.<br /><br />Also, I waaaay over-estimated my mechanical understanding and repair skills. I'm not afraid of this job. but I am. Just a little.<br /><br />Here are my biggest threats:<br /><br />Pistons<br /><br /> I picked up some STD pistons from ebay, and some rings from someone else. I have no idea what to look for to ensure that the rings fit the pistons. <br />Or the pistons fitting the sleeves.<br /><br />I figure I'll probably need to swing by a metal/auto shop to get the sleeves honed (just for good measure) and maybe they can take a look, and offer a little more piece of mind...<br /><br />Clutch:<br /><br /> Not too intense of a subject. My clutch was acting up a little toward the end of the trip, so I bought some new clutch plates. Should I soak them in oil before installation? Is there anything I can look for on the old discs that would give me a hint as to what was happening? (replacing the cable too, since the one on it was for ape-hangers)<br /><br />Carbs:<br /><br /> As far as I know, the carbs aren't doing bad, but I DID rebuild them with Keysters immediately before I started the trip, and I know everyone seems to hate keysters.<br />Right piston always seemed to be running a little rich, but then blew a hole in it. Someone mentioned unbalanced carbs to me, but I'm not sure if that holds water.<br /><br />Coils: <br /><br />Kind of random: I noticed that the coil on the right side of my bike was much larger than the one on the left. I bought some used good coils, just in case. but since then I've had a handful of discussions that suggest that the coil size really doesn't matter, as long as it's getting spark. (&quot;8 volt or 80 volt, if it blows up, it blows up.&quot;)<br /><br />Timing:<br /><br />So, like a couple jackasses, we let the cam chain drop. I'm a jackass because I know nothing about timing, how to find TDC, nor which piston is #1. Oh, and I basically tore apart the alternator, so, sitting here, I'm not too sure if there's a way to set the marks back in place.<br /><br />Advanced VS. Retarded- Someone mentioned that the blown piston was possibly indicative of timing that is too far advanced. Is this right? sparking after TDC shouldn't actually hurt the head, in my understanding, since it's on it's downward thrust.<br />Now if it was too far retarded, then it could be blowing while the piston is travelling upward, thereby increasing the pressure, and damaging the cylinder.<br />Am I wrong?<br />I probably am.<br /><br />(Something I just thought of... When I pulled the cam chain tensioner, I found that it had been stuck. really stuck. Like &quot;take out the lockbolt and slap the whole thing against the counter 4 or 5 times to free it up&quot; stuck. What are the chances this had something to do with blowing the piston? would it whack out the timing enough? stupid questions. I know. I'm full of 'em!)<br /><br /><br />About the rebuild:<br /><br />So how do you go about getting this whole thing back together, anyway? Anybody?<br /><br />Jesus, I'm screwed.<br /><br />So that's about it. I bought a motorcycle I didn't know much about (except that I'd wanted it bad for about 9 years!)<br />Flew someplace I'd never been to,<br />Tried driving a 40 year old motorbike that hadn't been maintained nor ridden on a regular basis, Across the entire nation,<br />spent all my money<br />all of it.<br />and then some.<br />and then, blew it up on 94 West in Hixton Wisconsin.<br /><br />So I'm here, it's there, and when I get back to it, I'll still know as little as I do now. Crap...<br /><br />Oh! but turns out the guy across the street from me has an old Dream! His left pistons not firing, so he's letting me putz around with it a little, in the hopes that I can fix it. <br />I'm just hoping I can learn a little more about the engine (Although mine has dual carbs, a second set of points, and possibly another coil(?) Well, anything helps right?)<br /><br />If anyone is interested in throwing some info my way, I'd be very grateful. I just can't stand the idea that I may have to ship this bike back. I gotta ride into town under her own power.<br /><br />Thanks so much guys.<br /><br /> -Eric<br /><br /> eric@emacklin.com<br />

[RJag]

First, <br />This sounds like a fairly big job. Just feel lucky that you didn't tear the transimission apart. Usually that is a bit much for a beginner.<br /><br />Take the sleeves and inspect them inside, If you just blew a hole in the piston and nothing scratched or scored (from fragments of the ringsn or piston) the inside of the cylnder I would leave them alone. (avoid the honing) Take the rings you bought and use one of the compression rings, push it into the cylnder flat and use a feeler gauge to check how much space remains between the ends of the ring. There should be a specification somewhere in your manual... If the gap is too big you may need to get some work done with oversize kits or boring to larger size. <br /><br />As for the rings fitting the pistons and the pistons fitting the cylnder, a little time with a micrometer comparing the old piston to the new ones should tell you this. When you are putting new rings onto a piston be very careful. they will spring a little bit but they do break pretty easy.<br /><br />I am not sure about the clutch plates... I know that the dreams often had trouble with sticky clutches. I thought it had to do with buildup on the old plates.<br /><br />You can adjust carbs for lean rich in several ways, an experienced mechanic can get very close by sound, others will run the bike for a while at a setting, pull the plugs and check for color of the deposit, Ideal color is usually a cocoa brown color. If you get white ash it is too lean, if it is greasy or oily black it is too rich. Running too lean in a cylnder can burn em up, however you said it was running rich when it blew.(On a side note using the wrong spark plug can also burn a hole in the piston if it is too long or hot) The carbs need to be synched for throttle movement as well as rich lean. check your clymer book for this it should be pretty easy to grasp.<br /><br />Cam chain is not a big deal, if you have to, use a clothes hanger or wire hook to fish it back up. with a bit of careful movement back and forth you can get the chain seated on the sprocket on the crank. You should be able to turn the crank by pulling on one side of the chain or the other. <br /><br />The flywheel is marked to indicate TDC for static timing, (you can confirm this by watching the connecting rod for when it is at the top of its movement. Your clymer book should indicate which cylnder is #1. On my bike it is the right one if you are sitting on the bike. <br /><br />You say alternator do you mean you took the flywheel and stator coil out of the bike? The flywheel should be keyed, only one way to put it in. If you can remember where the wiring came out of the stator to the leads for the wiring harness on the bike you should be able to get the stator situated right, the windings are wrapped in oiled paper looking stuff that can get brittle with time, so treat it gently and try not to ruin the insulation. I don't think it is that picky about alignment just get it so the wires are routed right and the holes line up to bolt it in.<br /><br />In your place I would clean out the crankcase first, you gotta get rid of all of the bits a peices of the blown piston. Drain the oil use solvent of some sort to clean everything up and try to account for all the peices. If you are still missing some peices I would tear into the the lower end and make sure that you have gotten everything. (you don't want to do all this work only to have the bike's transmission freeze up or have it suddenly loose compression because it has scratched up a cylnder.) After clean up go fishing for the cam chain. Hook a wire to the cam chain and feed it up through the channel it will run through in the cylnder part. Put new rings on the new pistons and lubricate the cylnders, use a ring compressor or a sheet of strong plastic or thin sheet metal to compress the rings and slide piston 1 into the cylnder (you may have to secure the crankshaft by having someone else hold the clutch assembly.) until piston two needs its rings compressed, compress piston rings on cylnder 2 and feed it up in. Seat the cylnders in place, pull on the wire to get your cam chain up, check to see if it is still on its sprocket, if not you can rock the engine and settle it into place. <br /><br />Well, I am getting a bit short of time for now. All of this stuff should actually be in your clymer book.. <br /><br />Hope this helps<br />Rick<br /><br />

[Pigeonalley]

<br /><br />Wow Rick.<br /><br /> What a great job. I have been “chain fishing” more times then I like to admit (some people never learn) That was so well written I could SEE the parts coming together.. I for one would like to thank you for writting it. <br /><br />Rob<br /><br />

[kustommusic]

Eric, Good stuff here! as far as timing,,,,before TDC is advanced after TDC is retarded. Ans yes soak the new discs in motor oil before installation. Good Luck. Steve Greer

[RJag]

For the next part we have to deal with the mechanical timing of the bike. Since this is a 4 cycle bike that means that the crank makes two full revolutions for each firing cycle of the engine. What Top Dead Center (TDC) means is the point in the firing cycle when both valves are closed and the piston for cyl 1 is all the way to the top. With the cylnders in place and the piston in cyl #1 all the way up you should probably reinstall the flywheel.<br /><br />If you inspect the crankshaft where the flywheel sits on it you will see it has a taper, this taper is what holds the flywheel in place (in-out) on the shaft. There should be a channel milled into the crank where a key fits. It may be resting in the flywheel or in the crank. Check the key to make sure it is still straight. Sometimes if an engine seizes or is halted suddenly while in motion the key will be partially sheared in this case it needs replaced. Clean up the taper put the key in the milled groove, slide the flywheel into place on the shaft. Hopefully it slid on far enough that the bolt that goes in the end of the crank will thread in. If not recheck the alignment of the key and how it is sitting, if it was lined up right you may have to clean surfaces better. If the key drifted or moved just try again with hand pressure and a bit more care. Once the bolt can thread on simply tighten the bolt down to the crank. You may have to shift the bike into gear and have someone hold the clutch assembly to get enough torque on this bolt as when you tighten it will want to turn the engine over. Not sure of the torque spec. it should be in your book.<br /><br />Back to mechanical timing. with cyl #1 At TDC you should now see a pointer on the housing lining up with a mark on the flywheel. If not, it should be off by 180 degrees. If it is off simply turn the bike over again until you have both the mark lined up and the cyl #1 at TDC. <br /><br />I would probably clean any carbon out of the head and from around the valves at this time. You can use carb cleaner or a scraper if you are careful. Look at the area where the valves seat into the head check to see if there are any cracks, if the surfaces where the valve meets the head are all smooth and check to see if the valve surfaces where it seals are all smooth (no chunks missing). If there are any reminants of the head gasket stuck to the head or cylnder now is the time to get em scraped clean. If you have valve problems, seat problems or problems with the surface where the head gasket sits that is a whole nother deal.<br /><br /><br />I am unfamiliar with how the chain hooks up to the head with your model, but one thing is pretty much universal, there will be a mark to indicate where the cam in the head is at TDC. both valves on cyl #1 should be closed and you should be able to line up a mark on the sprocket for the cam chain with a mark on the cam. When assembled correctly the marks to indicate TDC on the flywheel, and the marks for cam and cam chain sprocket indicateing TDC should all occur at the same time. Usually I do this part with the head nuts on fingertight and the head gasket in place. If you drop the chain or have to take the head back off for some reason it can save you a head gasket. If things don't line up you may have to unhook and adjust where the chain sits by a tooth or two, reinstall and try again until it is right. once everything is timed right tighten everything down to torque spec from your book.<br /><br />Bolting down the head needs to be done right. Your book should tell you a bolt tightening sequence and torque specs. Not following the sequence can warp the head and cost you a visit to a machine shop or even cost you for a new head. Not following torque specs for the head can set you up for a blown head gasket in the future, which for replacing requires you to remove the head.<br /><br />Usually unless your bike has electronic timing installed aftermarket it will have a way to advance the timing when the engine hits higher RPM. Make sure all of these parts are working and put the head back together like you took it apart. <br /><br />There should be a mark on the stator plate (the plate the points are hooked to) and a mark on the lobe/cam that turns to open and close the points. The screws that hold this plate in place are out near the edge of the plate, (they don't actually go through the plate) and allow you to loosen the screws and rotate the plate. Exactly how you go about static timing (electrical timing while not running) for your bike should be detailed fairly well in your clymer book. It ususally involves setting the plate at a certain place by twisting it and seeing where it causes a spark plug to spark when the points close with the engine at TDC, screwing the plate down. This will usually be enough so that the bike will run, however it can be a lot of trial and error to get this plate screwed down in exactly the right place so that the bike runs well. Once you get it right using trial and error or a timing light, I reccomend loctite on these screws.<br /><br />Hope this helps.<br /><br />Rick

[emacklin]

Wow, Rick.<br /><br />I feel like Maybe I should send you the price of the clymer manual.<br /><br />This will all help me out so much, I really appreciate it.<br /><br />This whole adventure went from <br /><br />&quot;Riding across America on the vintage bike I've always wanted&quot;<br /><br />to<br /><br />&quot;1966 Superhawk: An intensive crash course in vintage motorcycle maintenance and construction (Spread over 10 states)&quot;<br /><br />I'm more than happy with Rick's instructions and help, but if anyone else would like to chime in, or add to his directions, I'd be happy to hear from you as well. (Not that you shouldn't help out anymore, Rick! It's all very valuable advice.)<br /><br /> Thanks again, and in advance!

[LOUD MOUSE]

I'd say the head gasket had been leaking for quite some time.<br />That one side was running and the other really wasn't .<br />When these engines run for any extensive length of time on one piston that piston will HOLE because it is carring the total load and will eventually overheat and hole itself. At least that's what I see. ......................