Topic: 75 CB750F Gearchange problems!!!

[weasel897]

Hi all...I'm new to this site and was hoping that I could find some info on my situation.  I recently aquired a nice little bike and something just dosen't seem right with the shifting.  When cold the bike shifts without a problem.  However, it seems that when it warms up, it doesn't want to slip right into the next gear. I can feel the gears still turning(more the less grinding) when trying to advance to the next gear.  Usually after a few spins, it will finally pop into gear.  I've adjusted the lever adjustment for the clutch and that didn't seem to help much except for taking some play out of the lever.  I've also noticed that on occasion when downshifting, I have trouble shifting from 2nd to 1st.  The lever will lock up and I have to "double clutch" it. I'm sure someone somewhere has seen these problems.  Thanks in advance for any insight you can provide.   Brian

[scrapvalue]

Hi all...I'm new to this site and was hoping that I could find some info on my situation.  I recently aquired a nice little bike and something just dosen't seem right with the shifting.  When cold the bike shifts without a problem.  However, it seems that when it warms up, it doesn't want to slip right into the next gear. I can feel the gears still turning(more the less grinding) when trying to advance to the next gear.  Usually after a few spins, it will finally pop into gear.  I've adjusted the lever adjustment for the clutch and that didn't seem to help much except for taking some play out of the lever.  I've also noticed that on occasion when downshifting, I have trouble shifting from 2nd to 1st.  The lever will lock up and I have to "double clutch" it. I'm sure someone somewhere has seen these problems.  Thanks in advance for any insight you can provide.   Brian

What kind of oil are you using?
How much play is in your clutch lever?
Should have about an 1/8th inch play,(about the width of a nickel),

Hard shifting like you are discribing is usually a clutch issue. But not always.
Just best to start with the simple stuff first.

[Old Scrambler]

+1 and welcome to the board!  Good Oil....it solves a lot of shifting problems.....Search the board for Oil and Clutch advice.

[scrapvalue]

One more thing.
Not sure how much experiance you have riding , but it really makes a difference as to how fast you are moving, which gear you are in and your rpms.
There is always a sweet spot for your shifts.
If you are over reving, it will make it hard to shift.
If you are lugging it, it will also crate difficults.
I can shift my bike up easilly without the clutch with just a little let off of the throttle.
I mostly use the clutch for downshifts and when coming to a stop. Or hot rodding,(never really do that)
My oil of choice in the summer is straight 40w. Usually valvoline. No additives. Change frequently,(around a 1000 miles).
Motor has about 30,000 miles on it.

[weasel897]

Thanks for the responses.  I haven't checked the site in a while because I thought that this forum would notify me of reply's, but I guess not. 

The oil I'm running is Castrol Syntec 10W-40 I think (Bike was serviced and tuned before purchase).  I was thinking of going to a heavier weight because it's real hot here in Mississippi 10 months out of the year.  What are your thoughts on this? 

I'll check the clutch play to see exactly how much I have.  Sounds about right though. 

As for riding experience, I'm not an expert by any means, but It's not my first rodeo!  Other than my step-father's 78 Kawasaki 1000, this is the oldest one I've been on. 

Given my limited experience on these older style bikes, I was wondering about the shifting techniques, rpms, etc....I've noticed that sometimes it shifts better at a certain rpm than others.  Is there a magical rpm that works for anyone?

Thanks again for all the great advice!

Brian

[scrapvalue]

I run straight 40w Valvoline in the summer time. My motor has about 30,000 miles on it. I have ridden it for almost 4000 miles using 40w.
It will shift at any speed with no problem.
When I am shifting from 2nd on up, I very seldom use the clutch unless I am really getting on it.
Make sure your clutch is adjusted right, change the oil and see what happens.
Does the bike try to pull at all when you are sitting still with the clutch in and in gear?
Did I ask you how many miles were on it?
Did you know the previous owner, and was he a hot rodder?
If the bike has been ridden hard, there maybe some internal issues that are causing the hard shifting.

[weasel897]

I'll give the 40W a try and see how she performs.
Bike's got roughly 30,000 miles on it now.  I've only put about 600 or so on it. 
I've been reading some posts on clutch adjustment, so I'll give that a try as well.
No problems with the bike pulling while the cluch is in and in gear.
I don't know the previous (driving) owner.  I bought on ebay from a guy that rebuilds them.  He bought this bike and replaced the normal stuff (oil, filter, plugs, wires, adjusted valves, chain, sprockets, battery, etc...nothing major)
Overall, the bike is in execellant condition. It runs great and has no other problems.  I just want to make sure there's nothing "I'm" doing to mess up the tranny. 

Brian

[scrapvalue]

Just got back from a little ride around the country side and was checking to see what rpm it is at when I actually shift it. Guess I never really [paid attention the the rpm's, just how it feels.
Anyway, I am shifting at approx. 3000 to 3200 rpms.
If I just let off the throttle a little bit at those rpm's I can shift up easily with out the clutch,(or with it).
When I get to 5th gear, I am going just about 50 mph at 3200 rpms.

[Jerry Rxman Griffin aka MuthaF'er]

Weasel,

(PLEASE boys, let's not make this into another damned oil thread!)

I've used Castrol GTX 20w-50 for a long time in my 75 F without any real problems. I've never put synthetic in it. That may be your problem if it's not BIKE specific synthetic. Some oils just do not have the correct-for-the-day additives anymore. Too slippery. I was just comparing clutches from the 75 F vs a 78 K. You mention the PO does "rebuilds". Ask him if he has done ANYTHING to the actual clutch. There are at least 3 distinct clutches. Our 75/76F is identical to the 76 K. The late 76 F is identical to the 77/78 F and 77/78 K. Pre 76 K have other differences which I haven't researched. They ALL mix and match to a large degree. If he changed anything in the clutch it may not have the correct item numbers in it. Do the oil first though.   

[weasel897]

FYI...
I just looked at the list of this that was done to the bike before I purchased it and it has Castrol GTX 10W40 in it. 
It doesn't mention anything about the clutch. 

Weasel

[weasel897]

OK, so I drove the bike to work after lunch and there was a noticable difference when shifting around 3200 rpms.  I guess I was trying to stretch each gear too much?  I'm glad to see that it was operator error!
I'm still going to swap out the oil this afternoon weather permitting.
Now to get that pesky oil light to stay off.  I think I've narrowed it down to the oil pressure switch.  I'm hoping new oil and switch combo will knock that one out though.
Thanks again for all of the great help!

Weasel