Topic: 1982 CB650 Top End

[aircraftgrade]

Recently acquired a '82 CB650 that I posted about cleaning the carbs on earlier. I got the carbs back together and the bike starts and drives, but stumbles at about half throttle. Bike tops out at about 50 mph before it can't produce any more power in any gear. At idle, the right side is warm and has a fair amount of exhaust strength, compared to the left side which is weaker and much colder. The headers are actually hot on all 4 but by the time it makes it out the exhaust on the left, it's cold.

Compressions are: 30/30/60/60 and the brand new oil is significantly darker after riding 30 minutes. I'm calling it as bad rings and looking at doing a top end. Bike has 33k miles.

Anyways, anybody accomplish a top end on a CB650 and want to offer any advice before I move forward? I have an FSM in the mail, just wanted to hear any tribal knowledge on it. Any chemicals that might come in handy, or special tools, other than what's in the manual? Any advice on cleaning the different parts?

Looking at doing:
--new rings
--clean carbon from pistons
--lapping valves
--new gaskets/o-rings
--cleaning and painting the outside

Thanks!

[Nicklopic]

Wait until you pull the top end apart before ordering parts.
-There are 2 different head gaskets used and I never found any way to tell what used what until you look at it.

-Aftermarket head gaskets are thicker than OEM and the O-rings for the oil passages at either side of the motor my not seal well. There are 2 sizes listed from honda for these o-rings that can be found on a site like partzilla. Order the thicker of the 2.

-You may found your cylinder walls to be damaged and requiring a rebore and boom, you wasted money on stock bore rings. Cruzinimage offers pistons and rings in std. .5mm and 1mm overbore. larger that that, 674cc pistons from dynoman.

-Valves can not be lapped. If theyre worn and chewed up and they probably will be, youll need new ones. Old bike barn carries japenese made replacements. Valve springs are still available from honda. Apparently valves from this era are made from one softer metal and deform over time. You may consider just having the head sent out and rebuilt... and ported lol

-Clean the threads of the headbolts before reassembly. dirt gets caked up down there and it can and will crack the ear off the bottom of the threads inside the case.

-when re installing the rocker cover, back the tappet screws completely out and use the "rubber band trick" to keep them pulled open to prevent bending the valve stems

-expect helicoils will be necessary for certain things. The case is all aluminum and threads pull out. Mike from JMR helicoiled every bolt in my 650 head basically lol

Thats all i can remember off the top of my head right now.

[Scott S]

-Valves can not be lapped. If theyre worn and chewed up and they probably will be, youll need new ones. Old bike barn carries japenese made replacements. Valve springs are still available from honda. Apparently valves from this era are made from one softer metal and deform over time. You may consider just having the head sent out and rebuilt... and ported lol

 Why not? I've done it several times on 550's; what's different about the 650?

[DaveBarbier]

-Valves can not be lapped. If theyre worn and chewed up and they probably will be, youll need new ones. Old bike barn carries japenese made replacements. Valve springs are still available from honda. Apparently valves from this era are made from one softer metal and deform over time. You may consider just having the head sent out and rebuilt... and ported lol

 Why not? I've done it several times on 550's; what's different about the 650?

Yeah, I don’t see what makes these valves any different than any other.

[DaveBarbier]

Do you want to go stock or do you want to do some performance work? If so, read through my build thread. And contact Mrieck.

You might want to check out my build thread anyway. The link in my description will take you my table of contents. Down the list are links to different 650 “chapters” from my build.

This link is where the tear down starts:
http://forums.sohc4.net/index.php/topic,140833.msg1692299.html#msg1692299

There’s also a link in there to all the part numbers for o-rings, gaskets and such needed for a complete tear down.

As far as knowledge, get as many OEM parts as you can. OEM seals, and o-rings are sized correctly. I would get the head and cylinders decked by a shop. Gives you a perfect, clean finish for gaskets and will save you hours of scrubbing the gaskets off. No chemical removes the left over gasket material easily. ALL require a heavy amount of elbow grease and you can’t used abrasives or power tools on it because it will damage the aluminum. A shop’s mill will take it off in 15 seconds.

Don’t go nuts on making the piston crowns spotless. Clean them, but don’t loose sleep if they have some carbon on them. DO clean carbon deposits from the ring grooves. Remember, aluminum pistons are soft so be careful with power tools.

Make SURE to put rags in the cam chain tunnel or (when you get the cylinders off) in the holes in the case so you don’t risk dropping anything down there. Many many posts on people who fail to do this and then drop a bolt or something down there and can’t find it. Could trash an engine in no time if it gets picked up by the cam or primary chain.

[Nicklopic]

I wasnt really specific
As per Mike "Please keep in mind Honda valves cannot be ground if the valve faces are hammered……the valves have to be replaced." When I sent him my head, he said my valves needed to be replaced so I wanted to warm him of the possibility of the extra costs
Service bulletin from 71' describing the valves and why they can't be ground
https://www.motorcycleproject.com/images/SL84.JPG

[DaveBarbier]

Ah ok, it says valve refacing isn’t recommended. Lapping to the valve seat is ok and is recommended in the last line of that bulletin. That makes more sense.

So I would lap so you can see how well the surfaces are mating and then decide if you need a valve job.

[fizzlebottom]

I rebuilt the top end of my '82 CB650 a few years ago and can give some insights (some of which others have already mentioned):

• Go slow, label parts as they come out, and create cardboard templates for bolts and valves so they can go back where they belong.
• If oil or debris has made its way into the cylinder head bolt holes, clean the threads out with a tap, soak up fluids with a shop towel, and use compressed air to blow out anything else.
• Measure bolts and compare to the specs listed in the FSM. Do not mess around with over-stretched cylinder head bolts.
• Get one of the top end gasket kits, but make sure you can get an OEM head gasket.
• Have your cylinder head decked and your cylinder block decked if necessary. Take them to a machine shop. They can also do any valve lapping too.
• Follow instructions in the FSM as damn closely as possible. You may not need to measure every single thing, but it sure doesn't hurt.
• It may not be a bad idea to pull your oil pan while things are apart and clean that mess out. You very well may have some stuff floating around in there.

[DaveBarbier]

Oh, one more thing I just thought of. I am in the camp that you do NOT use a torque wrench on the small 6mm screws that hold down the valve cover. Just choke up on your 1/4” ratchet and tighten it by hand. You can crack the cover or strip out the threads in the head. It’s just not at all needed.

[MRieck]

Oh, one more thing I just thought of. I am in the camp that you do NOT use a torque wrench on the small 6mm screws that hold down the valve cover. Just choke up on your 1/4” ratchet and tighten it by hand. You can crack the cover or strip out the threads in the head. It’s just not at all needed.

That's how I have done it for years.

[aircraftgrade]

Thank you for all the responses.

Couple questions as I wait for my FSM to arrive in the mail (trying to get things prepped since tools are taking so long to ship from Amazon)

1. The '79 FSM calls out molybdenum disulfide grease on the camshaft bearing and valve stems during reinstallation. I'm assuming the '82 is similar. This is a pretty generic term and google searches didn't lead me to a typical product. Things claim to have "moly" in them but I don't see just a typical molybdenum grease. What should I use when assembling these parts?
2. I dont have access to a blast cabinet or parts washer but I'd like to clean the head and the cylinders myself. Any recommendations on good cleaners? I was going to make a makeshift parts washer out of a plastic storage bin.

[DaveBarbier]

Thank you for all the responses.

Couple questions as I wait for my FSM to arrive in the mail (trying to get things prepped since tools are taking so long to ship from Amazon)

1. The '79 FSM calls out molybdenum disulfide grease on the camshaft bearing and valve stems during reinstallation. I'm assuming the '82 is similar. This is a pretty generic term and google searches didn't lead me to a typical product. Things claim to have "moly" in them but I don't see just a typical molybdenum grease. What should I use when assembling these parts?
2. I dont have access to a blast cabinet or parts washer but I'd like to clean the head and the cylinders myself. Any recommendations on good cleaners? I was going to make a makeshift parts washer out of a plastic storage bin.

Instead of moly grease for the cam and tappets and stuff I used assembly lube. It’s designed for first start ups on new motors. Molybdenum disulfide itself is a solid so it has to be added to some sort of grease as a carrier so that’s why you see things that say “with moly”. Pure moly would be like a block of graphite.

As for cleaning, I really like odorless mineral spirits. Cheap and works excellently. I like to pour it in a spray bottle from Home Depot and scrub with a nylon brush.

[Nicklopic]

eBay has be solid with fast shipping, as an alternative right now for Amazon stuff

[aircraftgrade]

My head and cylinders are in work at the machine shop.  I've ordered all new valves (since they can't be ground) and having the head bead-blasted to remove all the carbon buildup over the years. The block and head were milled at the mating surface to remove the gasket too. Should run like a tank when it all goes back together.

I have some more new guy top end questions for those that have done this before:

1. Is anything applied to the head and base gasket before reassembly? I've heard mixed opinions on this.
2. Do I need to paint the head since it was bead-blasted, or can I leave it as bare aluminum? I would like to keep the bare aluminum look but don't want it to corrode later. Not planning on riding through any harsh weather.

Thanks!

[DaveBarbier]

I like OEM gaskets and for those you don’t use any sealant. Actually, I’m against using any type of sealant for any gaskets. I don’t know of any gasket that requires sealant.

Aluminum will get a white chalky film over time, so you can clear coat it if you want. I don’t think it’s necessary. Or paint it aluminum color.

[bryanj]

Who said they cant be ground? And you need to be sure that every last little particle of bead blast medium is removed or expensive repairs will follow
Oh and NO sealant on head and base gaskets

[Nicklopic]

Who said they cant be ground?

Honda and Mike rieck

[scunny]

I'll add that you have to be sure to seat the bottom end of the cam chain tensioner in it's little slot. you can check by looking up with the oil pan off.

[bryanj]

By ground do you mean resurfaced on a machine or lapped in with paste?

[MRieck]

 Bryan...the 45 degree face ground on a valve machine. I have personally seen ground 550 valves with the margin pounded out of them in a couple of thousand miles. The steel used for those valves (and other Honda valves) is pretty soft. And it's just not Honda. I have seen first generation Kawasaki Ninja/Eliminator 900/1000 and ZX-10 valves with razor sharp margins.....completely pounded to crap. And that is with non ground OEM parts.
That's why I just bought a set of Kibblewhite stainless valves for my CBX.

[bryanj]

I agree not to reface on a machine, we are on 2 different english languages again as grinding valves over here means paste and a double ended stick, machine work would be re-facing, albeit using a grinding machine.
Problem sorted.

[bryanj]

Mike, have fun with the CBX, i actually found a good use for the Honda "Blue Book" manuals on them------- glue the rocker gasket in with evostick and leave the cover rubber side down on the table with 4 Blue Books on top

[MRieck]

Mike, have fun with the CBX, i actually found a good use for the Honda "Blue Book" manuals on them------- glue the rocker gasket in with evostick and leave the cover rubber side down on the table with 4 Blue Books on top

I've had the engine apart for 5 years secondary to my regular job and porting work. Working on it is like hitting yourself on the head with a hammer.....it only feels good when you stop.

[bryanj]

Its real fun doing valve clearances

[aircraftgrade]

Some more follow up questions as I am putting things together this week (build thread with pictures coming soon)

1. Is there any different kind of oil that should be used for engine break in? Anything other than what is recommended for a "normal" oil change once broken in? I currently have 3 qts of conventional 20W-50 oil that I am planning on using.
2. Proper engine break in technique...a topic that has a LOT of different opinions. Most of what I found online was for new engines in new motorcycles, with tighter clearances and ECUs. Does anybody have any specific advice for these older, air cooled motors? This is not my first time breaking in a new engine though, I am familiar with the idea (I come from an aircraft maintenance world, but our procedures are probably different than that for motorcycles).
3. The Honda manual just says to change the oil every 600 miles. Is there typically an earlier change when breaking in rebuilt engines? How early should that first oil change be?

Thanks again.

[bryanj]

Change oil and filter at 500 miles then every 1500, no idea where you got 600 from.
Oil should be 10w40 or 15w40, 20w50 is too thick cold.
DO NOT  "baby" or lug the engine. If built to original specs normal running is fine, in facr in the late 70's Kawasaki had problems with oil consumption because people ran in motors too slowly and glazes the bores

[DaveBarbier]

The procedure is probably similar to what you’re used to in the aircraft world.
Don’t let it sit there idling
Don’t baby it or go for highway runs with a sustained RPM.
Vary the RPM a lot.
Third gear up hill rolling on the throttle is good as is engine breaking from higher RPMs.
Very high RPMs isn’t inherently bad for a new motor but avoid it until you know you don’t have leaks or weird noises and good top end oiling. I worked up to redline that same day.
I changed my oil the first time after about 150 miles and readjusted my valve tappets. They will be out of spec if you had a valve job done. If you did, continue to monitor them until they level out too.

You can look up places that do engine break-ins on a dyno. After a few pulls they’ll wind it up high and you can watch the HP increase each time.

[aircraftgrade]

Change oil and filter at 500 miles then every 1500, no idea where you got 600 from.
Oil should be 10w40 or 15w40, 20w50 is too thick cold.
DO NOT  "baby" or lug the engine. If built to original specs normal running is fine, in facr in the late 70's Kawasaki had problems with oil consumption because people ran in motors too slowly and glazes the bores

600 miles is from the service schedule listed in the Honda FSM for the bike. 20W50 is also called out as an acceptable oil in the FSM...I was more concerned about mineral oil vs. synthetic. It seems straight mineral oil is what I'm looking for so I'm going to stick with that. Thank you.

DaveBarbier, thanks for the valve adjustment note. That's a good idea.

[bryanj]

600 might be first service and then some later Hondas went to 6000 servicing so that could me a misprint, didnt do many 650 as they wernt that popular here. Personaly a wouldnt go more than 2000 or anually

[DaveBarbier]

There are specific break in oils you might consider using. It’s usually 10w-40 and high in zinc. It is also cheap since it will only be in the motor for at most a couple hundred miles. I’ve only heard that synthetic is not good for break in because it’s so slippery that it doesn’t let the rings bed in as well as conventional does.

Do a search on this site for break in procedures, many topics on it with differing ideas and techniques. None of them have done extensive double blind testing with multiple exact motors doing different break in techniques and comparing results. It’s all “I do it this way and haven’t had a problem” not very scientific. The large takeaways are varying RPM to load up the engine, a swift oil and filter change since there will be a lot of suspended particles and don’t go too high in RPM until you know you have good oiling and your motor was assembled correctly.