Author Topic: CB 750 K5 - Shifting hard/clunky (Read 9064 times)

andyvclifford · « **on:** January 22, 2016, 03:29:22 PM »

Hi!

My name is Andy Clifford, i have a 1975 CB 750 that is entirely stock minus the exhaust ( of course

! ). Ive had it for a few months now and it has 15,000 miles on it. I noticed over the course of the time I've had it the shifting seems to become hard / clunky at times and other times its completely smooth. By hard / clunky i mean it makes a loud noise or wont pop into gear without a little bit "grinding". Although sometimes its perfect, and goes right in without any noise. I am trying to figure out where to start troubleshooting this problem before I tear apart the engine to get to the transmission. What are some good things to do to test out what this might be?

Thanks!
Andy

HondaMan · « **Reply #1 on:** January 22, 2016, 03:35:29 PM »

Quote from: andyvclifford on January 22, 2016, 03:29:22 PM

Hi!

My name is Andy Clifford, i have a 1975 CB 750 that is entirely stock minus the exhaust ( of course ! ). Ive had it for a few months now and it has 15,000 miles on it. I noticed over the course of the time I've had it the shifting seems to become hard / clunky at times and other times its completely smooth. By hard / clunky i mean it makes a loud noise or wont pop into gear without a little bit "grinding". Although sometimes its perfect, and goes right in without any noise. I am trying to figure out where to start troubleshooting this problem before I tear apart the engine to get to the transmission. What are some good things to do to test out what this might be?

Thanks!
Andy

It sounds like you've been bitten with some of the modern low-zinc motor oils: these gearboxes require zinc to operate smoothly and release the clutch easily. If you just changed the oil and don't want to do it again, get some zinc additive (ZDDP, in little 4 ounce bottles) and add a bottle to the oil. That will help after about 50-100 miles.

After that, use only oils rated 20w50 and LOW DETERGENT, with zinc. Examples are: Bel-Ray EXL Mineral, Spectro (synthetic), Torco Motorcycle Oils for Offroad Use Only, Motul, or a few others. DO NOT use high-detergent car oils, like Castrol XL or XR, Valvoline "V-Twin" oil or other oils for Harleys or V-Twin motorcycles, or thin oil, like 10w40. The CB750 engine needs 20w40 at the very least, and 20w50 is the recommended summertime oil weight.

RevDoc · « **Reply #2 on:** January 22, 2016, 08:41:15 PM »

Andy, if you've been following the forum for any time before you decided to become a member then you probably realize that Mark (Hondaman) is the Grand Wizard of tech details for these bikes and will always steer you in the right direction. Besides the oils he suggested, another option that I have been using is Rotella Diesel. Diesel oil is low detergent which reduces the chance of foaming, (which these clutchs do not like!) and is a high zinc level that is crucial for these clutchs to work smoothly.

I see on your profile that you are in New Haven. If you have any Pep Boys stores up there, they stock it in gallons for a very reasonable price. I've only seen 15-40 on their racks but they could probably get the 20-50 that would be better for summer heat.

andyvclifford · « **Reply #3 on:** January 22, 2016, 08:44:57 PM »

Wow thank you I will try this ASAP. I am well aware of Hondaman i actually bought his book a week after buying my CB 750 and am flirting with the idea of rebuilding the engine this winter :0.

scottly · « **Reply #4 on:** January 22, 2016, 08:51:24 PM »

It may simply be a matter of adjusting the clutch, as well as experience with shifting a wet clutch, constant-mesh transmission. As far as rebuilding the motor, if it ain't broke, don't fix it....

HondaMan · « **Reply #5 on:** January 22, 2016, 09:30:50 PM »

Quote from: scottly on January 22, 2016, 08:51:24 PM

It may simply be a matter of adjusting the clutch, as well as experience with shifting a wet clutch, constant-mesh transmission. As far as rebuilding the motor, if it ain't broke, don't fix it....

Scottly has a great point: I may have overstepped my diagnosis? First adjust, THEN go after the oil, if it doesn't fix it...

PeWe · « **Reply #6 on:** January 23, 2016, 12:25:10 AM »

Not finding neutral when engine is warm is another "problem" that correct oil can make better.

evanphi · « **Reply #7 on:** January 25, 2016, 08:30:09 AM »

I find that if I don't preload my shifts a bit the transition from 1-2 (through N) is quite clunky. Just a bit of preload is all you need... you don't want to pop into N while accelerating! Shift "slowly" from 1-2, also. Don't slap the shift. Push it.

Last year I ran BelRay, and this year (spring) I will be running the Rotella T 15W40. I'll be interested to see if I notice any differences.

BobbyR · « **Reply #8 on:** January 25, 2016, 11:11:14 AM »

You have received sage advice from extremely knowledable people. Over 15 years, I have found that the oil has
an effect. Also, as the mileage on the increases shifting changes. One other thing I have observed, these are old and strong but crude gearboxes, in addition you are also not the first owner. They do get a bit cranky on and off.

PeWe · « **Reply #9 on:** January 25, 2016, 11:32:02 AM »

Sloppy drive chain will also cause clunky sound when shifting to 1:st from neutral. Other gears too if shift unloaded
The initial description can be as earlier written, clutch adjustment inside clitch cover where the arm must have correct play and cable clucth cable adj.
Plus the oil that must have zinc. Search for oil in the forum when this has recently been discussed so most of the modern variants have been discussed.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #10 on:** January 25, 2016, 12:08:00 PM »

+1 good point about the chain.

Kenzo · « **Reply #11 on:** January 25, 2016, 12:59:50 PM »

Shell Rotella T and 4oz of Rislone per oil change has been working great on my 550.

Cheers,
Kenzo

andyvclifford · « **Reply #12 on:** January 25, 2016, 04:26:06 PM »

Thank you very much - I bought some Rotella T engine oil today and I have the day off from work tomorrow so I will do an oil change and check the clutch adjustments. Checking the drive train would require taking the engine apart correct? Is there any way to diagnose that part without taking it apart first?

Thank you for so much information!
Andy

HondaMan · « **Reply #13 on:** January 25, 2016, 04:32:58 PM »

Checking the chain part of the drive is simple: put the bike on the centerstand, then spin the rear wheel several turns. If the chain is in good shape, it will have a slack in it, which should be about 3/4" in the center of the lower width of the chain. If it goes tight-then-loose, over and over, it is unevenly worn. This can cause clutch shift problems, as can a too-tight chain (with no slack at all). A rusty chain, with kinked links that don't lay straight easily, will also cause 'chatter' when running (coasting) which will also make for erratic shifting.

andyvclifford · « **Reply #14 on:** January 25, 2016, 04:37:16 PM »

Great! I will add this to the list tomorrow. Looking forward to diagnosing this problem!

scottly · « **Reply #15 on:** January 25, 2016, 06:17:51 PM »

Start with adjusting the clutch. Your symptoms point towards a dragging clutch.
I prefer to check the chain slack off the center-stand, sitting with the tire on the ground and weight on the seat; this will put the chain at it's tightest position. It's far better for the chain to be a little loose than a little tight!

Redline it · « **Reply #16 on:** January 25, 2016, 11:34:46 PM »

Quote from: scottly on January 25, 2016, 06:17:51 PM

Start with adjusting the clutch. Your symptoms point towards a dragging clutch.
I prefer to check the chain slack off the center-stand, sitting with the tire on the ground and weight on the seat; this will put the chain at it's tightest position. It's far better for the chain to be a little loose than a little tight!

Andy, if you don't know exactly what Scotty is saying here, about chain adjustment, without any guessing or measuring, is you have 3 shafts to line up, the counter shaft, pivot shaft (swing arm,) and the axle shaft, when those three are in a line, that's the tightest point of the chain unless the chain is kinked, adjust with some but little slack. The reason for the slack is, if it's too tight, it can break a counter shaft, or case, the chain is strong. And the easiest way to get the 3 shaft in line, are with a tie down connected at the upper frame to the swing arm, somewhere near a shock, compressing it, then you can set the chain tension and the alignment and know it's right, even after the axle is matching the reference marks on both sides of the swing arm, snug up the axle nut a little, and sighting down the chain from the rear,then spin the wheel, you'll be able to see if it's not straight, but double check that the rear sprocket teeth are riding in the center and not off to either side. Sometimes the marks wont be accurate if there's slight bends in the frame.

PeWe · « **Reply #17 on:** January 26, 2016, 01:15:24 AM »

Please, do not forget to tell us what solved the problem:)

andyvclifford · « **Reply #18 on:** January 26, 2016, 01:35:49 PM »

Hi guys!

Here is what I've done so far:

Adjusted the clutch as per the Honda manual - removed clutch cover, loosened clutch cable, removed the clutch locknut and turned the clutch in until it met full resistance and then turned it back out 1/4" turn, and finally reassembled the cable to proper tension. I included a video below of the clutch being operated without the bike on as reference to see if it looks normal!

I am still waiting on the oil filter to do the oil change, and I cannot find the zinc supplement in any auto store, so that may need to be ordered online, however I do have the Rotella T 15w-40 triple protection oil ready to be put in once i get the filter.

Unfortunately the problem persists after clutch adjustment but I think I've pinpointed how it occurs and included a video below. Whenever I turn the bike on, pull in the clutch, put it in neutral, release the clutch, and then pull the clutch back in and shift into either 1st or 2nd there is a loud "clacking" sound / sometimes a grinding sound before it pops into gear. After this inital "clack" if i shift from 1st to 2nd or 2nd to 3rd ect it shifts perfectly normal. It mainly occurs when i have put the bike into neutral, released the lever, pulled the lever back in and then shift.

Also i checked the oil cap and noticed a "tan frothy substance" on the dipstick pictured below. I assume this is condensation? Is this bad?

Thanks!
Andy

RevDoc · « **Reply #19 on:** January 26, 2016, 02:31:57 PM »

Yup!, get your fresh oil in and I'm thinking you'll see much smoother shifting. My 550 was like that when I first got it and had not changed the oil yet. Regarding the Rislone supplement I have found it at AutoZone stores if you have any in your area.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #20 on:** January 26, 2016, 02:34:09 PM »

What RPM is it running when going from neutral to first?

andyvclifford · « **Reply #21 on:** January 26, 2016, 03:04:56 PM »

RPM - Running at idle around 900-1000 usually once its all warmed up

Jerry Rxman Griffin aka MuthaF'er · « **Reply #22 on:** January 26, 2016, 04:12:14 PM »

Quote from: andyvclifford on January 26, 2016, 03:04:56 PM

RPM - Running at idle around 900-1000 usually once its all warmed up

Does it grind the gears/clunk at less than 1000rpm, say, 800rpm or just when cold at higher rpm?

andyvclifford · « **Reply #23 on:** January 26, 2016, 04:29:24 PM »

Pretty much always whenever i shift as described above. It seems have something with setting the bike to neutral and then getting back in gear

Kenzo · « **Reply #24 on:** January 26, 2016, 05:25:06 PM »

The neutral, first, neutral shifts look good to me...clutch not dragging too much. The question is how well will it hold under power. I'd get some new oil in it and yes most chain auto parts stores carry the Rislone.

Cheers,
Kenzo

andyvclifford · « **Reply #25 on:** January 26, 2016, 05:29:36 PM »

Sometimes it grinds before it goes in, it seems much louder/clunkier than it should be - perhaps its completely normal this is my first bike? It is quite loud and the bike lurches sometimes when i pop it into first this way. Other times the shift makes no sound at all and pops right in.

seanbarney41 · « **Reply #26 on:** January 26, 2016, 05:43:05 PM »

sounds pretty normal to me, maybe just some sticky clutch plates/basket. Good oil should help, but you are may have to run it for a while with good oil before improvement will be felt. If that does not work, the clutch basket may be worn/grooved and that is not terrible to replace either...no case splitting.

How much have you ridden this bike?

scottly · « **Reply #27 on:** January 26, 2016, 06:13:05 PM »

Sound pretty normal to me, too.

Spanner 1 · « **Reply #28 on:** January 26, 2016, 06:51:23 PM »

I'm late to the party but that oil with condensation in it ( milky stuff ) is not helping ya and baaad for the motor. So, new oil of the correct type and some riding trips ( 20 miles min IMO ) in reasonable temps will help this problem for sure.

Kenzo · « **Reply #29 on:** January 26, 2016, 07:01:04 PM »

Quote from: andyvclifford on January 26, 2016, 05:29:36 PM

Sometimes it grinds before it goes in, it seems much louder/clunkier than it should be - perhaps its completely normal this is my first bike? It is quite loud and the bike lurches sometimes when i pop it into first this way. Other times the shift makes no sound at all and pops right in.

There is always a little clutch drag, so when you drop it into first, all of the gear, dogs, countershaft and chain come to attention from a relaxed state. These bikes don't shift with a snick-snick like a manual car transmission. The fact it will shift out of first to neutral tells me there is not too much clutch drag. Hell I can't even walk my dirt bike backwards with it in gear and clutch in...too much drag...but it locks up when I hammer down!

Get some good oil in it, preferable with some zink, ride it and make sure you hit the shifter with a little bit of authority and ride it like other have said. May take an oil change or two to get these 40 years old bikes running like they use to.

Cheers,
Kenzo

andyvclifford · « **Reply #30 on:** January 27, 2016, 06:20:17 AM »

Thanks for the advice - i will doing the oil change today and trying to get some miles on it while the weather is above freezing. If you guys think this is perfectly normal and not doing any harm to my gearbox ill trust the forums - i just felt like based on some of the other cb's ive ridden it was excessively clunky and grindy.

Also - the drive chain seems to be ok based on the minimal tests i did (as suggested by the almighty hondaman!)

thanks!!
andy

DH · « **Reply #31 on:** January 27, 2016, 06:22:55 AM »

My k5 does this as well. Only thing I've found that helps a little is to slow the idle speed down.

andyvclifford · « **Reply #32 on:** January 27, 2016, 01:21:02 PM »

Changed oil today and added zinc supplement. Took it for a 15 mile drive after that (until i got too cold!) and brought it back in. I cant really notice any huge difference in the shifting. It randomly shifts hard and then not, especially when its been in neutral.

I suppose i give up on this, since it seems that everyone says this is normal?

One other thing to note - after riding for 15 miles the frothy / foam on the oil cap was back meaning there is still a problem with condensation? Should i check my breather tubes?

robvangulik · « **Reply #33 on:** January 27, 2016, 02:37:12 PM »

Quote from: andyvclifford on January 27, 2016, 01:21:02 PM

Changed oil today and added zinc supplement. Took it for a 15 mile drive after that (until i got too cold!) and brought it back in. I cant really notice any huge difference in the shifting. It randomly shifts hard and then not, especially when its been in neutral.

I suppose i give up on this, since it seems that everyone says this is normal?

One other thing to note - after riding for 15 miles the frothy / foam on the oil cap was
back meaning there is still a problem with condensation? Should i check my breather tubes?

Checking for blocked tube is always good (and easy) but a ride for 15 miles at temps not far above freezing won't let you get rid of all moisture in the engine, you're generating more until the engine really warms up.
Only when the bike stops 'smoking' white water vapour from the exhaust its really warm and then you start vaporising the water in the oil.
There is a saying: bad weather doesn't exist, only bad clothing.
Dress yourself warm enough and go for an extended ride of some 50 miles, by then the oil should be clean again.

cb650PK · « **Reply #34 on:** January 27, 2016, 02:37:27 PM »

In cold climate 15 miles is not enough to warm up the oil. If the temp is really low, it never warms up. Your shifting seems pretty much normal for K5. After ridding your bike for while, you may figure shifting technique it likes better.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #35 on:** January 27, 2016, 02:40:34 PM »

Oil froths without condensation. Did you lower your idle rpm?

HondaMan · « **Reply #36 on:** January 27, 2016, 05:14:49 PM »

Quote from: Jerry Rxman Griffin aka MuthaF'er on January 27, 2016, 02:40:34 PM

Oil froths without condensation. Did you lower your idle rpm?

It also froths if it is a high-detergent type: that's not a good thing...

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Author Topic: CB 750 K5 - Shifting hard/clunky (Read 9064 times)

DH