Author Topic: Cb750k7 funny clutch? (Read 2322 times)

78whiteorbs · « **on:** March 28, 2018, 04:41:12 PM »

Heres an easy one possibly!

Just got finished with this bike pictured and runs great but when taking off in first even after warm you have to like feather the throttle just a little bit or it will wanna die. Imagine a two stroke that jetted wrong were you have to rev rev it to take off. Once in gear everything shifts and accelorates normally as should....

Clutch cable is adjusted all the way out and the lever almost.could this be a clutch issue? Or maybe and accelorator pump issue? It revs clean in neutral from 1200rpms on up. Pulls like a freight train! There doesnt seem to be an adjustment nut at the engine end of the clutch cable......

78whiteorbs · « **Reply #1 on:** March 28, 2018, 05:31:10 PM »

Well Im a dummy. Adjusted clutch out on engine side so the pull is much firmer now. So I know its fullyengaging and disengaging but still the friction point trying to walk it seems super small. Like its " on" or "off". Could just be the clutch is worn?hmmm....doesnt stall now or hesitate hardly as much . maybe just need to ride with choke till it was a little warmer. After a spirited ride it seems way more responsive from a dead stop to wide open. Doesnt like to take it easy out the gate likes fast take offs.

HondaMan · « **Reply #2 on:** March 29, 2018, 08:53:32 PM »

Without trying to start an oil thread...the oil you are using can cause this, today. Low-zinc oils, in particular, will do this to the clutch. Also, use 20w50 oil in this engine, which by default also widens the "slip point" of the clutch by delaying the oil's departure from between the plates slightly longer. However...this will take about 100 miles of in-town shifting and riding to make it purge the old oil from the clutch, first, after the change.

There are also ways to widen the slip point of the clutch, as shown in my book, but you have to open up the clutch cover to do it, and a Dremel tool would be helpful, as would the clutch-nut puller (Motion-Pro sells thes, so does PartsNmore).

78whiteorbs · « **Reply #3 on:** March 29, 2018, 08:57:02 PM »

Yeah still having to rev it pretty high when taking off. Traffic always sucks but gonna suck big time now. Will try changing oil. First CB750 have had this problem with out of maybe 15

dave500 · « **Reply #4 on:** March 30, 2018, 01:47:38 AM »

What do you mean by funny?Funny how?how is a clutch funny?what do think the clutch is there to amuse you?how funny can a #$%*ing clutch be?ive seen a lotta clutches and believe me none of them were funny!so tell me,how funny is your clutch,i don't get by what you mean by funny?funny how?how is it #$%*ing funny?

Paintedseat · « **Reply #5 on:** March 30, 2018, 02:35:40 AM »

It's your accelerator pump and your needle position.

rotortiller · « **Reply #6 on:** March 30, 2018, 03:00:03 AM »

You can maximize clutch lift by making sure the lever at the engine and cable are 90 degrees to each other at mid handlebar lever travel. Do that with the screw adjuster on the engine and use the cable length adjuster to match it up. That will remove one item from the equation. The acceleration pump is not a concern for normal pulling away since low throttle movement does not squirt fuel. With the clutch disengaged the bike should not thy to walk in first gear at idle.

78whiteorbs · « **Reply #7 on:** March 30, 2018, 06:40:16 AM »

Quote from: dave500 on March 30, 2018, 01:47:38 AM

What do you mean by funny?Funny how?how is a clutch funny?what do think the clutch is there to amuse you?how funny can a #$%*ing clutch be?ive seen a lotta clutches and believe me none of them were funny!so tell me,how funny is your clutch,i don't get by what you mean by funny?funny how?how is it #$%*ing funny?

Nice Goodfellas pun.

The more I think about it the more I am thinking itmay be as suggested in the fuel delivery. When I ease out the clutch it does begin to lurch the bike forward as normal put right at the friction point , if I dont over rev the engine like you would a 2 stroke that is jetted to lean or rich( always get those swapped up) it wants to stall out. I think it could be for the same reason! I took this carb bank off another 77 that had , gasp ...pods. I cant say for fact that I didnt assume the needle position and jet sizes were stock. Hmmmm

78whiteorbs · « **Reply #8 on:** March 30, 2018, 06:43:38 AM »

Oh and the accelorator pump works great.Revs perfect in neutral. Maybe missing one of the two little brass restrictors in between 3 and 4 as I recall but the streams shoot straight and strong.

Paintedseat · « **Reply #9 on:** March 30, 2018, 09:13:23 AM »

The pump can work great but you need to make sure the rod is in contact with the actuator arm. The squirt of gas needs to be immediate. Just make sure it is barely touching. Where are your needles set? You have 5 notches the 4th worked best for me.

78whiteorbs · « **Reply #10 on:** March 30, 2018, 10:06:38 AM »

Yeah my guess is the PO might have to change my needle clips to compensate for the pods that were on there go figure pod strike again

78whiteorbs · « **Reply #11 on:** March 30, 2018, 10:23:58 AM »

can you change the needle clip position without removing the carbs I'm thinking you can just pull the tank and do it from the top that would be great if so I wouldn't have to pull the airbox and go through all that my time for wrench and on Mike's is short today

78whiteorbs · « **Reply #12 on:** March 30, 2018, 10:35:30 AM »

4th from top or bottom?

Paintedseat · « **Reply #13 on:** March 30, 2018, 10:39:03 AM »

They say you can but I never tried. Say the first notch at the top of the needle is 1 I set mine down to the 4th notch.

Paintedseat · « **Reply #14 on:** March 30, 2018, 10:41:19 AM »

The accelerator rod is more important. You want that squirt of gas to shoot as soon as you start twisting the throttle. That gives you the extra gas you need to start off from a start. The slides opening let's a large amount of air in immediately and you need that fuel too.

rotortiller · « **Reply #15 on:** March 31, 2018, 11:41:20 AM »

Mine squirts about 1/8th throttle (.120" gap at the throttle stop adjuster when water pistol rod contact occurs) and works perfectly fine, actually it runs like a top the truth be known. The small .020" or so gap at the rod is pretty typical even though the manual says otherwise. Not much mass airflow change at small openings. I can pull away on the flat with mine from idle (1.5 grand) by feathering the clutch and not touching the throttle. Brother's K7 does the same thing as mine with a similar gap at its rod end. Basically they both pull away like any other CB750. What I'm saying is even with a totally non functional acceleration pump you should be able to pull away smoothly provided all else is correct.

Paintedseat · « **Reply #16 on:** March 31, 2018, 11:59:32 AM »

. 020"? Do you know how small a gap that is? If your bike takes off with no throttle your idle is set too high. Mine is 950rpm and it needs throttle to take off. Never had a bike that didn't.

rotortiller · « **Reply #17 on:** April 01, 2018, 04:32:19 AM »

Quote

Do you know how small a gap that is?

.020" at the rod equals quite a twist at the throttle. Yup I know, that is why I explained it very, very carefully.

Paintedseat · « **Reply #18 on:** April 01, 2018, 06:59:34 AM »

Well you don't need it if your idle is set to 1500 and. 020 is not a lot of throttle. Try adjusting your idle correctly and your idle air/fuel correctly and get back to us.

rotortiller · « **Reply #19 on:** April 01, 2018, 08:23:51 AM »

Look at the lever ratio that drives the accelerator pump rod. Think about the pump stroke as it relates to full throttle travel and use a bit of math. If you had a bike to look at you would understand easier, my bike works fine as stated. Maybe down load a K7 service manual and look at the pictures could help you understand. It's a lot easier when you have a bike on hand to play with and observe. 1200-1500 idle makes these bikes run much more quiet and smooth since it gets rid of normal SOHC engine rattle-chug-chug-chug like noises from the clutch and primary.

Paintedseat · « **Reply #20 on:** April 01, 2018, 10:14:34 AM »

I have one and I have 2 sets of carbs I am currently rebuilding. Mine idles perfect at 950 rpms. I have never had to set it high to make it idle correctly except when my pilot jets were too small. The manual says the pump arm is adjustable for a reason. You're telling me to go read a manual and you have your idle set at 1500. Lol. You might want to go read it yourself. If you think your carbs are set up correctly and you have to set your idle at 1500(and you can take off with no throttle) you need to rethink your set up. It is not set up properly. Anyone can mask improperly set up carbs but jacking the idle speed up. It's an indicator that something is a miss.

Paintedseat · « **Reply #21 on:** April 01, 2018, 10:56:16 AM »

Went to look at manual. Hmm. What does it say?! It also says to adjust idle to 950 to 1050. Hmm $:-\$

rotortiller · « **Reply #22 on:** April 01, 2018, 02:12:40 PM »

I guess it's like the bible and all to be obeyed, in order to avoid that bolt of lightning hey!

Paintedseat · « **Reply #23 on:** April 01, 2018, 02:22:20 PM »

Lol. You're the one that brought it up. Do what you want but I'm going to trust the engineering that built it

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Author Topic: Cb750k7 funny clutch? (Read 2322 times)