Did I just ruin my engine?

R

robmurray12

New Member
So, I've been rebuilding my 1974 CB360 and its been going really well up until last night. After finishing chassis work I have started on freshening up the engine. I am planning on painting the cylinder part of the engine black while leaving the head, valve cover, and cases cleaned up aluminum. So, I tore the engine down and pulled the cylinders and scrubbed them with simple green and soap and water in the tub.


I thought if I immediately and thoroughly dried the cylinder sleeves I could avoid rust, I knew the rest would be fine since its aluminum. Big mistake, I got spot rusting in the cylinders. Nothing horrific but it is definitely noticeable. I'm thinking that since I rinsed it with hot water that caused it to flash dry because the block was warm from the water and caused it to rapidly evaporate. Anyways heres the dilemma, did I just ruin my cylinders, forcing me to bore over and fork over the cash for new pistons and rings? Or can I hone the spot rust off and maybe just get new rings?
I'm a college student and my budget is tight. I'm figuring to rebore will be about $75 and pistons and rings will set me back another $150. Speaking of witch I have only been able to find OS Pistons and rings on bikebandit.com, any other options?


Some background on the motor. When I got it in the January cold of Colorado I did a compression test on the engine. It was literally 22 degrees in my garage and I just kicked it a few times to get a reading. No oil sprayed in the cylinders and I got 120psi left cyl. and 110psi right cyl. Granted I had not made sure the valves were within spec so that could be part of the reason compression was low in additional to it being cold. Also right cyl. has a small scratch about 1/2" long starting at the top of the cyl., can definately feel it with the finger nail. So, with all this information should I buck up and rebore and get os pistons and rings or, will a hone job be ok for now. And the only reason i'm entertaining this thought is because I want to get it running for summer to ride and if it will last me the summer/3000mi I will just wait to rebuild the engine till next winter when I can't ride anyway. Thanks, your guy's vast knowledge will be a great help. I frequent this site often for both inspiration and tech talk. If I can figure out how to get photobucket pics to work i'll post some. Thanks guys.
 
A machinist will be able to tell you for certain whether a bore job is needed of whether you can get away with just an hone. Make sure you bring in the specs for him when you get the work done.

You can might be able to get away without either the bore or the hone, but if it were my bike, I wouldn't even try it. It's much less of a headache to know things were done right rather than have to worry about it later when something else goes wrong. For what it's worth, the rust will probably wipe right off with a microfiber cloth and some WD-40.
 
For peace of mind and a strong motor I may just give in and overbore it. Good advice on the machinist, I know of a good one that specializes in motorcycles so I may take it by and see what he thinks. As for sourcing new os pistons and rings do you guys have any good retailers or do you rely on ebay?
 
Just to clarify surface rust mentioned in the original post is not a reason to bore it. That will probably just wipe off and will definitely come off with an hone. The reason for boring is the scratches that can be felt.
 
I'd lightly hone it, check to make sure it's still with stock spec. If it is the slap it back together and go.

You can get non over bore rings direct from your Honda dealer. Also you can file down ob rings by filing down the gap until it fits non ob pistons.
 
ok, I think I may just lightly hone it. Is it worth it to get new rings after honing or will it be fine to reuse the old ones? I'm gonna bust out the caliper tonight and see how close within spec the cylinders are. If its out of service limits I'll do a rebore, but if its ok I'll just go the cheap route and just hone it. I really want to get the bike running within a month or so. I don't have the money/time to do a full blown engine build so I'll enjoy it for the summer and the next winter do a rebuild if it needs it then.
 
I agree with Brother Sonreir, if the cylinders look good and are in spec when you measure them you can wipe them out to clean them. Make sure the cylinders do not have any scratches, scoring, or ridge ring at the top and at least use new rings. You will also need to file your new rings to the proper end gap before you put them on your pistons, put the rings in the cyinders one at a time and check the end gap in several different areas of the cylinder as well.

Also if you do decide to bore the cylinders for new pistons mark your new pistons for each cylinder and have each cylinder cut for each piston as new pistons often vary slightly, make sure that you use the piston in the cylinder that it was cut for.
 
Honda has still got new rings. I paid 78 bucks at my Honda dealership for a complete set. He did give me a 20% discount tho. He thought that all six rings came in one set but only three do haha.
 
robmurray12 said:
So, I've been rebuilding my 1974 CB360 and its been going really well up until last night. After finishing chassis work I have started on freshening up the engine. I am planning on painting the cylinder part of the engine black while leaving the head, valve cover, and cases cleaned up aluminum. So, I tore the engine down and pulled the cylinders and scrubbed them with simple green and soap and water in the tub.


I thought if I immediately and thoroughly dried the cylinder sleeves I could avoid rust, I knew the rest would be fine since its aluminum. Big mistake, I got spot rusting in the cylinders. Nothing horrific but it is definitely noticeable. I'm thinking that since I rinsed it with hot water that caused it to flash dry because the block was warm from the water and caused it to rapidly evaporate. Anyways heres the dilemma, did I just ruin my cylinders, forcing me to bore over and fork over the cash for new pistons and rings? Or can I hone the spot rust off and maybe just get new rings?
I'm a college student and my budget is tight. I'm figuring to rebore will be about $75 and pistons and rings will set me back another $150. Speaking of witch I have only been able to find OS Pistons and rings on bikebandit.com, any other options?


Some background on the motor. When I got it in the January cold of Colorado I did a compression test on the engine. It was literally 22 degrees in my garage and I just kicked it a few times to get a reading. No oil sprayed in the cylinders and I got 120psi left cyl. and 110psi right cyl. Granted I had not made sure the valves were within spec so that could be part of the reason compression was low in additional to it being cold. Also right cyl. has a small scratch about 1/2" long starting at the top of the cyl., can definately feel it with the finger nail. So, with all this information should I buck up and rebore and get os pistons and rings or, will a hone job be ok for now. And the only reason i'm entertaining this thought is because I want to get it running for summer to ride and if it will last me the summer/3000mi I will just wait to rebuild the engine till next winter when I can't ride anyway. Thanks, your guy's vast knowledge will be a great help. I frequent this site often for both inspiration and tech talk. If I can figure out how to get photobucket pics to work i'll post some. Thanks guys.
Click to expand...
You must be located in a Mountain town, cause Denver is all year riding for the most part.
 
robmurray12 said:
I'm gonna bust out the caliper tonight and see how close within spec the cylinders are.
Click to expand...

you cant just use calipers, you must use t-bore gauges and then measure them with calipers. youre supposed to measure the cylinders at 10 and 4 oclock, 12 and six oclock, and 2 and 8 oclock at three different heights in the cylinder if you want to do it correctly. the main reason for this is to check for taper and out of round, but if you do try and just measure the cylinders with a caliper then it wont be accurate because there is a ridge at the top of the cylinders.

this is what you want to use.....

vernier-micrometer-caliper1.jpg


and these.....

6-pc-5-16-6-cylinder-t-bore-gages-gage-set-telescoping-pix.jpg


OR just this....

kdt-3769.gif
 
Man, if I had the money I would do it that in depth, think I could take it to a machine shop and have them do some measurement for a small fee?


Also, one more question I just remembered. When I first got the bike i pulled the generator cover while it was on the side kickstand so it was leaning over towards the gen. side and when i pulled the cover oil started pouring out. do i have a bad crankseal or is this normal when the bike isnt level?


Below is a picture of the bike now that im done with chassis & paint and another of the generator..


Picture060.jpg



Picture025.jpg
 
In the future, whenever you clean bare metal like that be sure to fog it with some WD40 or rub it with a little honing oil to help prevent flash rusting. Other then that I don't think you ruined anything. That rust come right off with some 0000 steel wool and some 3 in 1 oil.
 
or just wipe it with an oily rag until that rage comes out clean. OK That wasn't very clear. Wipe it with an oily rag and repeat until the last new oily rag comes out clean.
 
Sonreir said:
Never reuse old rings. If you take the pistons out, you need new rings.
Click to expand...

If the ring gaps and clearances after honing are within spec, there's no reason not to use the old rings.
 
rockcitycafe said:
If the ring gaps and clearances after honing are within spec, there's no reason not to use the old rings.
Click to expand...

i agree 100%, ive reused rings in the past in desperation and never had one problem, just inspect them and make sure there is no substantial scoring and you should be fine.
 
If you can afford it, I would say just replace the rings. You already have the pistons free from the head, why make more work for yourself in the future? :D
 
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