[krukster86]

Hey all,

Thanks for all the help in the past, I am going to need some more now

When working on the bike, I spent a lot of time on everything but the engine. Now that I have the parts bike engine taken apart, I am thinking of rebuilding it as part of a winter project. I have never done any engine work so please forgive me if the questions seem basic. Anyway, here it goes:

When I got the parts bike, the bike was sitting outside for almost a year under a tarp. Carbs were off the bike and I gave it a few kicks to check compression in the engine. I got readings of about 130 each side, which I think is not too bad for the condition it is in. Flash forward to now, I have the top end in pieces. I was thinking of just stopping here and having parts "just in case", but a recent find of an almost NOS cam guide made me consider a rebuild. How do you check out the size of the pistons? Do I need new piston rings? Do I need to hone the cylinders? Do I need new pistons too?

Thanks!

 

[66Sprint]

At 130 PSI, it is due for re-ringing at the least.... Your machinist can measure the bore for you (usually a nominal charge)... If it needs bored, you'll need pistons, rings, and wrist-pin clips (NEVER re-use these)......Plus gaskets of course.....
Read the online manual to familiarize yourself with what is involved, and get the necessary specs........ If in doubt.... ASK or farm it out...... You CAN do this...Just take your time and follow the steps... It's NOT rocket surgery......

 

[tbpmusic]

Kruk -

130 psi is not good - any time and money you sink in it will get you little in return, unless you address that.
The bike will never start and run well........
I don't want to see yet another disappointing 360 experience.

Have the cylinders "miked", compare to the specs - if all is cool, just hone and give it new rings.
See if the valves leak - put the head on it's "side" and fill the intake/exhaust ports with acetone. Observe the valves for any leakage into the combustion "dome". No leakage or seeping at all is permissible.

Oh, and do the compression test again, just in case - remember, throttle wide open, NO CHOKE.......

 

[krukster86]

Steve and Bill,

Better to get it done right the first time, I gotcha.

I need to do something to keep occupied this winter when I am not riding, and with Chicago weather, winter does come early! (its in the low 50's tomorrow wtf?!)

I have a gasket kit still in the packaging lying around. I will study the service manual sometime this week to get some bearings. The valve leakage test looks like a nice next step forward. I will keep you guys posted with my findings and dead ends haha!

 

[krukster86]

Ok next question:

I have the top end apart. Should I have all disassembled components oiled for storage or are they ok as is (some have been washed and have no oil on them)? They will probably be apart for some time until I get all the components ready.

 

[66Sprint]

Spray or wipe with clean oil and put in ziplock bags......Put labels on the parts bag (left intake rocker & shaft, etc,etc.....) That way the parts return to where they came from.....Re-clean & assembly lube (where needed) as you re-install ....

 

[krukster86]

Alright some minor progress. I found out that the bead blasting got way into the engine, and it looks like I am going to tear it down all the way :-D. Clutch is off and I performed some cleanup on the top end.

I hit a roadblock tool-wise. I need to pick up a snap ring tool and a valve spring compressor/make one. I was trying to take off the rotor, but it kept spinning when trying to loosen it. Any tips?

 

[66Sprint]

Why do you need to remove the (I assume) alternator rotor?...Starter clutch not working?....

 

[Badbiscuit]

probably blasting media in/around it....just a guess

 

[krukster86]

Oh, the glass beads from the previous blasting got ALL over despite my best efforts to seal it up. So I need to remove everything to clean up all the loose beads.

 

[leethal]

I used a strap wrench, the type you fit car oil filters with...

 

[krukster86]

Cool, thanks Lee!

 

[krukster86]

Still gotta track down some tools!

In the meantime I took a look at the pistons, rings, and the cylinder.
Here are my findings: I took off the rings on one piston and snapped the bottom 2 in the process...looks like I did it incorrectly, but I was going to change them anyway. I have no idea what size my piston is, but I think it is standard? (How do you check this? Is it on the piston?) I measured the bore of the cylinders as it was suggested in the service manual, and I got roughly 66.45 (+/- 0.07).

Please tell me where to go from here. According to the service manual I need to check the ring gap. Is it ok to just use the remaining ring? Or is this not necessary if I am looking for new rings anyway?

I heard from another forum that to check if the pistons are ok, I need to place them in the cylinder and insert a feeler gage to check the gap if it is in spec. What is "spec"?

 

[MNellis]

In the meantime I took a look at the pistons, rings, and the cylinder.
Here are my findings: I took off the rings on one piston and snapped the bottom 2 in the process...looks like I did it incorrectly, but I was going to change them anyway. I have no idea what size my piston is, but I think it is standard? (How do you check this? Is it on the piston?) I measured the bore of the cylinders as it was suggested in the service manual, and I got roughly 66.45 (+/- 0.07).

Please tell me where to go from here. According to the service manual I need to check the ring gap. Is it ok to just use the remaining ring? Or is this not necessary if I am looking for new rings anyway?

I heard from another forum that to check if the pistons are ok, I need to place them in the cylinder and insert a feeler gage to check the gap if it is in spec. What is "spec"?

You might have snapped the rings during removal because they might have have been stuck in the groove. That's not uncommon. I found the middle ring on one of my 450 pistons stuck and it broke during removal as well. Be aware of this because, if you don't clean the grooves properly and completely you might have problems installing the new rings if you re-use these pistons.

How did you check the bore diameter? You ask how you check if the piston is the standard size. You'll need a good Micrometer (a dial or digital caliper is not good enough). You measure the piston SKIRT, not the top of the piston and compare the measurement to the published spec in the service manual. The difference between the piston measurement and the cylinder measurement is your "piston to wall" clearance. The min/max for this clearance should also be called out in the service manual. Typically, it's probably between .002" and .003" but check to be sure.

When measuring the cylinder you should measure it in multiple directions. You need to measure it near the top, in the middle and near the bottom of the piston travel. Additionally, you might want to measure it from "front to back" and "side to side" at the top, middle and bottom. The top, middle and bottom measurements should be compared to each other to insure there is not excessive taper to the cylinder, there should be an allowable variance called out in the manual as well. The side to side/front to back measurements will tell you if the bore is out of round at all.

You don't need to bother measuring the ring gap of the OLD rings but you will need to measure and adjust if necessary, the ring end gap of the new rings. Your friend is correct, you place the ring in the bore and use a feeler gage to check the gap. What he may have failed to mention is that you need to "square" the ring in the bore before measuring the gap. You accomplish this by inserting the ring and then use the top of the piston (without rings installed) to push down on the piston to square up the ring and ensure it's not cocked in the bore. You need to so this with all three rings on each piston.

You asked a couple of times "what is spec"? Each model of engine is unique and specs may vary. However, the specs should be called out in the factory service manual and if I read you post correctly, it looks like you have one.

 

[66Sprint]

Kruk... The "specs" are the listed measurement specifications for the part(s)....
Maximum bore (worn) for a stock piston is 67.1mm, standard is 67.01/67.02, so the wear limit of the cylinder is .09mm...before an oversize bore/piston is required...sometimes a cylinder can be lightly honed and a new std (size) piston installed to replace a slightly worn original piston... It ALL depends on the measurements....
A std piston should be 66.97 to 66.99 with a minimum diameter of 66.85... Anything smaller is worn out... (Now you can see why an EXACT measurement is necessary)
"fattest" piston in smallest allowable bore gives minimum piston to cylinder clearance of .02mm, smallest piston in biggest bore gives maximum .05mm clearance at original installation..(wear accounts for the remaining size differences).... Most mechanics have the cylinders bored/honed to .03/.04 during a rebuild, and measure off the replacement pistons to figure out what that would be.....
The "specs" are usually in the manuals......
Hope this helps you out....... Steve

EDIT: I see Mike has also explained the process.... Between the two, you should have all you need... IF NOT ask specifics again....

 

[leethal]

You should take the cylinders and a printout of page 41 of the Honda Sevice Manual to your machinist to measure wear. If you clean the crowns of your pistons there may or may not be a number cast into them. If not, then you're probably running standard pistons.

Its common to re-bore 2 sizes up to allow the machinist some headroom, but if the jugs are only slightly worn you may get by on 1 oversize.

I have a good used pair of 1 over pistons, and a NOS pair of 1 over rings. You can have em all for postage + a carton of my favorite swilling beer (Melbourne Bitter $35)....

 

[krukster86]

Alright thanks guys. I am going to read this over and over again to get it wrapped around my head before proceeding. Sorry for the confusion, it is just that the Service Manual seems to have cylinder bore specs for the oversize bores, but nothing about "standard" range.

Lee, that sounds like a sweet offer! I will let you know after I get this stuff understood.

 

[krukster86]

Well I got the valves out. I took out 1/2 of them with the valve spring compressor. The other half, I could not get the cotters to come out at all. I resorted to the "smack with a hammer as hard as you can" method and popped them all out. I have a new set coming in sometime next week. Fun fun!

Also I split the cases too, now the real tough stuff begins!

 

[krukster86]

DELETED.
Wow that was stupid :lol:

 

[krukster86]

GAH! Looks like the glass bead blasting is starting to be a bad idea! I have glass bead pretty much everywhere. A lot can be taken off effortlessly but the nooks and crannies are tough to get to. I am really considering just popping my engine pieces in the dishwasher and letting it run to get all this crap out. Is there a more "sane" way of doing this? :lol: