new on the forum

Posted: Tue Apr 27, 2010 11:20 pm

Hi to everybody
Pretty cool to find this place, it will be interesting and useful to be able to share the joys and worries about my first bike, a 1981 CB900c I got last august. This is my first post so here is my description and feeling so far.

It's now around 34k, so I almost put 5k on it. The bike was in fairly good shape, mechanically and aesthetically when I got it, and it still is.
Obvious issues when I picked it up were the rusted exhaust pipes (4 in 4) in some spots, with even some rather big holes, to the point that the previous owner patched them with some kind of caulk...

Aside from that, bike is running strong, even if it's sometimes a major pain to start it up...I read these engines are cold-blooded, mine certainly is, especially after sitting for more than 4 or 5 days (winter was tough). Starts right away when ridden every day but needs some time to warm up.

After the 1st 1k, I noticed the oil consumtion was very very, very high (>1 quart/1k, but no smoke, no leak on the ground etc, smells like oil though!). I will post about this asap. Also noticed an oil leak on the right arm of the fork. I know nothing about bike mechanics except for my mountain bike, so I'm here to learn.

This bike is a total blast, the engine is full and the technology on it is still pretty advanced (driveshaft!). Some concerns maybe, quite heavy and the handling in cornering feels a bit floaty/not precise sometimes, it's not exactly a rail. But what do I know, it's my first!

Thanks for the future help and see you around. Anyone in the Hudson Valley, NY? haven't seen a lot of CB900s around

Posted: Tue Apr 27, 2010 11:23 pm

Welcome to here wave

Please Click Here

Posted: Wed Apr 28, 2010 6:02 am

Welcome.

When was the last time the oil was changed. What weight are you running. New oil tends to stay in these bikes a bit longer. As the oil breaks down it thins out and disappears.

Most important, have you had the valves adjusted yet?

Posted: Wed Apr 28, 2010 6:38 am

Replacing the fork seals and using 15w fork oil will go a long way toward improving your handling.

Posted: Wed Apr 28, 2010 9:14 am

Howdy

Posted: Wed Apr 28, 2010 10:25 am

OldTimer wrote:

Welcome.

When was the last time the oil was changed. What weight are you running. New oil tends to stay in these bikes a bit longer. As the oil breaks down it thins out and disappears.

Most important, have you had the valves adjusted yet?

Hey OldTimer,
I thought every 5k would be good, so haven't done it yet. I'm using valvoline 10W40 4T for bikes. For the soon to come oil change, I was thinking about 20W50, so the oil is less thin and maybe I'll burn less.
I will try to do the oil change myself, it's a simple thing, but I've never done one, car or bike! So I'm a bit stressed out. I just bought a KN-401 oil filter (is it a good one??).

I really don't know much about engines and stuff, so valves adjustment? The guy I got the bike from supposedly is a bike mechanic so he told me he sync'ed the carbs and did all the relevant stuff...
I found the Honda service manual for the CB900F 1980 to 82, read about the valves adjustment, I must say I don't really understand everything and it looks a bit scary to do. Since I don't know much, I don't really wan to start messing with it, but I also want to learn how to do these stuff.

old_dirt, same thing for the fork seals, is it "easily" doable myself? the local mechanic told me $300 to get it done, pretty expensive. Where can you get a seal?

Posted: Wed Apr 28, 2010 10:26 am

I also posted about the oil consumption

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&p=121983#121983

Posted: Wed Apr 28, 2010 10:49 am

Welcome to the site mentodan ... Smile

5K ? no wonder it's burning oil . You should be changing oil about every 2K ( some do it more often than that) .

Posted: Wed Apr 28, 2010 10:59 am

Jeeberz! I missed that! These bikes contaminate the oil much faster than the factory thought they would. If you feel and smell the oil at 2000 miles you will see and smell something that is no longer capable of protecting your motor from wear. I don't care if you put oil in there that costs $1000 a quart, it's gonna stink and feel bad in 2000 miles.

Change the oil at 2000 miles and your bike will be a lot happier. My oldtimer wrenching buddy changes his every 1000 miles. He uses regular old castrol 20w50 available cheap everywhere, and has over 100,000 miles on his old GS Suzuki... although it's ready to die, but that's pretty good for a bike.

Posted: Wed Apr 28, 2010 12:21 pm

Ok got your point, will do the change more often.
But in 4k, I put more than 4L of oil, so I kind of replaced the oil (ok not the filter), right...? Sometimes when I was not monitoring it often enough, I even had to put 2L to top it off.

Another point still not clear to me...what kind of oil should I put, bike specific (wet clutch) or car oil will be fine? lots of stories on internet about that, what's your experience with the CB1000c?

what do you think about 20W50 instead of 10W40, good idea? what brand do you recommand for the CB?

Posted: Wed Apr 28, 2010 12:26 pm

These bikes break down oil much faster than cars because the gear box is also bathed in the same oil.

I have used Castrol 20-50 for years also. Some folks use desiel oil and will chime in.

Posted: Wed Apr 28, 2010 12:36 pm

diesel oil or bust

Posted: Wed Apr 28, 2010 12:45 pm

mentodan wrote:

old_dirt, same thing for the fork seals, is it "easily" doable myself? the local mechanic told me $300 to get it done, pretty expensive. Where can you get a seal?

I imagine that for $300.00 you can do it yourself. If you have enough mechanical ability to change the oil and sparkplugs, you should be able to handle fork seals. There are plenty of instructions and tips on here in addition to the FSM procedure.
The easiest way to get quality seals is to go to your local Honda dealership.

Posted: Wed Apr 28, 2010 4:12 pm

So the sparkplugs also have to be changed along with the oil?

Posted: Wed Apr 28, 2010 4:46 pm

mentodan wrote:

So the sparkplugs also have to be changed along with the oil?

not with every oil change, but if you don't know for sure the history of the plugs, yeah, change 'em. not too hard to do, relatively cheap as well. a quick job. wires too if they look nasty, but somebody else has an opinion on that too, and will chime in. download the manual and ask questions, plenty of help here.

welcome too!

Posted: Wed Apr 28, 2010 10:46 pm

If you run a stock ignition, I'd recommend changing spark plugs often. The book in chapter 1 says to replace the plugs every 4000 miles.

With an MSD ignition, I got over 20,000 miles on a set of plugs without a cough.

Posted: Thu Apr 29, 2010 10:11 am

I see, pretty sure I have stock ignition, so might'could be a good time to do this as well, sparkplugs I think I can do easy (true? no need to remove the tank or stuff like that?)

About the valve clearance adjustment, I read the manual, not very clear to me. I think the guy I bought it from did it, but really I am not sure. How do you know you have to adjust the valves, beside oil consumption?
I used the search function to find earlier documented posts on this, but I did not find something for total beginners. I think I need pictures, like some kind of step bey step tutorials, is there something like that among the posts?

Posted: Thu Apr 29, 2010 10:16 am

You know you need to check the valve clearance because the book says to, and if you don't and one tightens up, you'll have a burnt valve. The valve clearances are supposed to be checked every 4000 miles according to the book, too. Why don't you just go download the book and read it?

Posted: Thu Apr 29, 2010 10:32 am

Maybe this will help ?

Valve Adjustment :

DO NOT ROTATE THE CAMS WITHOUT A SHIM IN EVERY BUCKET .

Check all clearances ( cam lobe pointed straight away from the shim face ) and record them on a chart like the one below . Cylinder #1 ; exhaust valve #1 is furthermost left while sitting on the bike ; record the initial clearance in EXHAUST #1 top square on the chart .
After recording the clearance , remove the underlying shim . Measure it and put it back in the bucket . Record that initial shim size in the corresponding square . DO NOT ROTATE THE CAMS WITHOUT A SHIM IN EVERY BUCKET . If you do , serious bucket damage could and most likely will result .
You don't have to do them all in a row ( 1 - 8 ) on the motor . Which ever lobe offers the best angle for checking clearance ; work your way through all 16 . Just make sure you record the clearances and shim sizes in the correct squares . When you know each valves clearance and shim size , do a little math and figure which shim will work where and which will need to be exchanged for a correct thickness . Remember the correct clearance for both the exhaust and intake is .005" . The FSM says .002" . That's way too tight and can cause burnt valves .

Hopefully , you have a good relationship with your local Honda dealer and better yet the shop manager . Ask if they will do a shim exchange . They probably have a box buried in the back of the shop and figure that doing an exchange might just get them some of your other business . Most shops don't do very many valve adjustments that use these big shims anymore . The newer bikes use a smaller shim about the size of a large pea . So , it's not taking anything out of their pockets.

Here's the worksheet I use .

Posted: Thu Apr 29, 2010 2:17 pm

I have the manual and I read chapter 3 inspection and adjustment, it's just not clear to me how to do that, no clue what it looks like when you remove the cylinder head cover. Total beginner so this is new to me. I've just learned there were 2 exhaust and 2 intake valves /cylinder!
I understand that when an exhaust valve is up, you can not access the intake, right? And then you have to rotate the crankshaft by 180deg to see the intake valves. But how do you tell an exhaust from an intake valve?
Also, what clearance are we talking about? between what and what...
I know for you this must be basic but I don't really understand what we are talking about here...is there some pictures by any chance?

Posted: Thu Apr 29, 2010 2:23 pm

Experience is the best teacher.

It would be best for you to pull the valve cover and get started. Take your time and ask questions of the board as you go.

Now, the intake valves are located on the upper back side of the cylinder head and the exhaust valves are on the lower front side of the head. They are adjacent to the carbs or exhaust accordingly.

Posted: Fri Apr 30, 2010 1:21 pm

thanks OldTimer

when removing the cylinder head cover to do the valves, is it not full of oil? or all the oil has dropped down? also do you have then to replace the rubber seal that's between the head cover and the head?

Posted: Fri Apr 30, 2010 1:31 pm

Yeah, if you lean the bike over to each side for a few moments before removing the valve cover, some of the oil will drain out. I use a turkey baster to remove more oil if necessary.

Posted: Fri Apr 30, 2010 8:59 pm

I will usually put a jack under the front cross member and lift the front end off the ground. This tilts the engine back and keeps the oil from running all over the front.

I would replace all the rubber on the valve cover, especially the bolt seals as you do not know how old they are.

Honda has them available though pricey. Georgefix on Ebay sells aftermarket gasket and seals and is good to deal with.

I would also replace the tach drive seal - 91311-425-000. You need to get that from Honda.

When you get ready to do the deal, ask a lot of questions and consult the book. No sealer on the gasket.

Posted: Wed May 19, 2010 10:12 pm

I am new to this site. Seems like a great place to get help.

I have downloaded the manual, my original got burnt.

1980 CB750F, original owner

edit: I zipped all the chapters to the manual and uploaded to my site so only one download is required. Let me know if there is a problem or conflict.
http://www.nlneilson.com/wwposts/H_CB750_79_83.zip