Topic: '75 CB550 2nd gear slips into neutral

[stereosilence]

I have noticed that in second gear, if I give it a lot of gas, it goes into neutral. Any idea what causes this and how to fix it?

[ekpent]

The shifter fork may be bent or the gear engagement dogs are worn out and does require a case split to fix. Not a rare problem,especially on the larger 750's.

[grcamna2]

It's possible that the shift detent cam that lives on the end of your shift drum has loosened up;how are the other gears,do they have this similar problem? other wise it might be a problem with your shift fork inside the trans. Have you done all the" outside the cases" checks that you can like make sure your shifter is tight & clutch adjusted correctly by the book ?

[stereosilence]

Let's slow down a moment  . I bought this motorcycle last week. It is my first ever carbureted vehicle. At this point, I'm going through trying to figure out what is wrong and what I can fix.

So, I haven't attempted any adjustments on it yet. I have simply identified the problem. I have only noticed this problem in second gear. Can you point me in the direction of some tutorials for what to do?

[grcamna2]

stereosilence,

       I recommend as a first solid plan of action to look on this forum for a download to the Original Factory Honda Service manual.It will give you much insight on what will keep your motorcycle operating up to it's full potential.It has pictures on the procedures like adjusting your clutch & other things & also has a troubleshooting guide.The other members on this Great forum will literally walk you through the different procedures on the work that you need done to diagnose the problem you are having...it will be a tutorial. I will help also.

[bryanj]

Jumping 2nd is not common and will be either the springs on the detent roller which is hidden behind the clutch outer inside the RH outer case (see the manual)

OR

damage to gearbox internals requiring relacement parts---usually the quickest "Fix" for this is a replacement bottom half engine(or complete one) as parts are expensive and its a complete engine strip with necessary time to fix

[Rgconner]

If you are new to the bike, and it to you:

It could be your shifting technique. These old bikes shift hard. Make sure you are being firm and positive with the shift. I have a 75 550k. Failure to shift fully into second (or third) will make it pop into nuetral when load is applied. I did it a lot until I sorted out the clutch and my shifting technique. Now it only happens when I get lazy and fail to shift/clutch properly.
 
Before you do anything, remove the tappet covers and make sure oil is getting up there. Ruining a valve train sucks. If you have any doubt, don't run it until you make sure oil is getting up there!

Read the FAQs! There is an ungodly amount of info and even some wisdom there. Run a search on anything you want to fix. You will find info on the best way to do it, and some ideas on the best stock/aftermarket parts to use.

Get the manual, go over the adjusting procedure for the clutch. Very few are well adjusted from the PO ( previous owner, also the other meaning)

Try this:

Don't clutch, just roll off the throttle and press up on the shifter. If it goes into 2nd smoothly you are probably fine. If not, try varying the timing and firmness of the up shift. Theoretically, you don't need the clutch if you never stop, it will shift up and down so long as you get the timing right. No, I am not saying it is a good idea, just that a good transmission "can" do it.

Shifting while oil is cold can suck, btw.

Second, oil impacts shifting and clutching. Changing the oil and using a good oil like delvac 1300 or Rotella in a 15-40. Make sure it does not have friction modifiers or it will f'up your clutch.
Mine shifted much better with Delvac, so try a few brands/weights. Oil change interval is only 1500, so it does not take long. (if the bike was not well maintained, you might be changing it more often at first. Mine went 500 miles before it got black as night. Took 2 changes to ungunk the engine)

Walmart sells both for ~$15 for a gallon.

Third, get an old timer to try the clutch for you. Again, this is not like a modern bike and what feels wrong to you might actually normal for the bike. Part of the charm, like an oil slicked leg from a BSA. Helps if you can find someone who sold/repaired/rode them in the 70's.

Set it on the center stand for oil checks and don't overfill!

[grcamna2]

+1 on what Rgconner says....100%.

[dave500]

no clutch upshifts are ok on bikes,dont down shift without the clutch though,in fact blip the throttle as you de-clutch on a down shift similar to driving a constant mesh truck(fuller/roadranger/mack/spicer),itll match the rpms a little better and make for a smoother downshift,avoid shifting it really fast,as mentioned they are a little clunky compared to modern bikes,if it was ridden long with this gear popping out chances are its rounded the engagement dogs and itll have to come apart,itll also bend or wear the fork if its not fixed if it hasnt already,,also check the shift pedal isnt hitting the case ,one member here had the wrong pedal and it was fouling the case preventing a good solid shift,if the pedal is set too high you have to lift your boot higher to shift,set so its comfy and you get full range of movement.

[Rgconner]

no clutch upshifts are ok on bikes,dont down shift without the clutch though,in fact blip the throttle as you de-clutch on a down shift similar to driving a constant mesh truck(fuller/roadranger/mack/spicer),itll match the rpms a little better and make for a smoother downshift,avoid shifting it really fast,as mentioned they are a little clunky compared to modern bikes,if it was ridden long with this gear popping out chances are its rounded the engagement dogs and itll have to come apart,itll also bend or wear the fork if its not fixed if it hasnt already,,also check the shift pedal isnt hitting the case ,one member here had the wrong pedal and it was fouling the case preventing a good solid shift,if the pedal is set too high you have to lift your boot higher to shift,set so its comfy and you get full range of movement.

Good point about the shifter. I have a bad ankle and cannot lift the full range up, so I moved mine down a tooth or two to compensate. if someone's has been moved or just does not work for them, moving it could give them that positive shift you need on these bikes. My buddy's BMW makes me jelous sometimes, shifts like a dream. Of course, I think his monthly + insurance is more than I paid for the bike, $600.

Downshifting is different than up shifting as you say. Lot harder without a clutch. Don't try it at home kids.

[dave500]

yeah i have my shifter set a spline or two lower to get that little better purchase on up shifting,i actually sort of roll my foot counter clockwise as i lift it.

[bryanj]

Dave you are showing your age! most big stuff now hasn't got a third pedal or a "waggle" stick---The good old Eaton stwin split used to sepatate the men from the "Tune" makers!!

All the points on the gearchange are good ones, but to be only playing up in 2nd i am leaning towards the damaged internals i'm afraid

[stereosilence]

I can tell this will be a blast already. I am 25 with pretty much no experience as a mechanic (changing oil and stuff doesn't count). I got this bike because I love motorcycles and because I wanted to learn to work on them. At this point, I'm trying to figure out where to start (I'm about to make a post on that next).

Back to the clutch issue, I am pretty sure it is none of the above. I put my inexperienced money on wear. I drove it about 40 miles today (much of it interstate) with no problem.

The previous owner used it as a daily driver and had it into a mechanic recently so I doubt it is anything that would destroy the bike in short order as I would expect it would already be destroyed after a few years of being as it is. The other thing is that it doesn't slip at the shift. It only seems to slip under heavy load, that is, when I tried to accelerate as fast as I could and when I accelerated up a very steep hill. None of the other gears seem to have a problem at all.

Anyway, I really appreciate your input and it looks like the community here is going to be a lot of fun to work with as I try to keep my bike in shape!

[grcamna2]

 Worn gear engagement dogs? or damaged shift fork ?