cb750 slow take off

My 1976 cb750 runs great but one thing I do notice is when I really give it throttle, it feels as if the clutch is slowly releasing to full contact. I have had the carbs recently serviced (running pods) and also the clutch cable has been adjusted. It feels like a slow clutch engagement even when I am already in gear and just decide to punch the gas. Does this sound like I need new clutch plates or could my carbs be running rich? Much thanks

Those are two completely different issues...

Is the sluggishness throttle or clutch related specifically? Help us help you.

VonYinzer said:

Those are two completely different issues...

Is the sluggishness throttle or clutch related specifically? Help us help you.

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Thats a great question. What would the difference feel and react like? Im not sure if its a clutch or throttle issue to be honest.

To test the drive ride along at a moderate speed and pull the clutch in, and let the bike drop a little speed. Without adjusting the throttle drop the clutch quickly.

If the bike jerks up to your original speed the clutch is good. If the bike takes a long time, clutch is slipping.

If the clutch is good then your problem is something else.

ako said:

To test the drive ride along at a moderate speed and pull the clutch in, and let the bike drop a little speed. Without adjusting the throttle drop the clutch quickly.

If the bike jerks up to your original speed the clutch is good. If the bike takes a long time, clutch is slipping.

If the clutch is good then your problem is something else.

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Okay so I finally was able to test the bike with your suggestions. The bike did jerk up to the original speed. The problem is mainly when I really pull the throttle hard. It just kind of slowly takes in that amount of power. Any other thoughts? Thanks so much for any help!

What kind of Cb750 are we discussing here ?

The CB750 Four, seems to have this "powerdip" every bike till the K6.
On the F2 en K7 they changed the carbs, and put in a mechanical fuelpump to try and solve it.

Tetter said:

What kind of Cb750 are we discussing here ?

The CB750 Four, seems to have this "powerdip" every bike till the K6.
On the F2 en K7 they changed the carbs, and put in a mechanical fuelpump to try and solve it.

Click to expand...

Hmm. I just know its a 1976 SOHC cb750. Does that help. How would I know if its a K6?

It sounds like you may not be used to a slide type carburetor? If you smoothly apply throttle to wide open do you experience the issue?

If you quickly wack the throttle wide open on a slide type carburetor, you will experience a bog from the engine breathing in too much air until the revs catch up.

I've heard these bikes done respond well to the open atmosphere of pods. I don't know if that could be related.

acm177 said:

It sounds like you may not be used to a slide type carburetor? If you smoothly apply throttle to wide open do you experience the issue?

If you quickly wack the throttle wide open on a slide type carburetor, you will experience a bog from the engine breathing in too much air until the revs catch up.

I've heard these bikes done respond well to the open atmosphere of pods. I don't know if that could be related.

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It does respond nicely when I smoothly apply throttle. Its only when I wack the throttle. You think it could be my pods?

No-- It might not be the pods per say... But you could switch back to an airbox and check.

These carbs require you to moderate the vacuum smoothly so they can do their job. You may need to tune them, but perhaps just refine your riding style toward their operation.

A CV carb lifts the slide according to the vacuum signal from the engine. Or a carb with an accelerator pump squirts extra fuel to help with the sudden amount of air you gave it... Slide carbs just require a different style of moderation.

acm177 said:

No-- It might not be the pods per say... But you could switch back to an airbox and check.

These carbs require you to moderate the vacuum smoothly so they can do their job. You may need to tune them, but perhaps just refine your riding style toward their operation.

A CV carb lifts the slide according to the vacuum signal from the engine. Or a carb with an accelerator pump squirts extra fuel to help with the sudden amount of air you gave it... Slide carbs just require a different style of moderation.

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So what you are saying is that these bikes arent really built to peel out or pop the front wheel off the ground?

Well i'm not saying that...
I'm sure that there is some tuning you could do to better the response of the carbs. But to me it sounds like they aren't malfunctioning.

Id start by giving the air box a try again and see if it makes any difference.
I don't have any experience with these bikes so maybe someone else has some further input.

Thanks for all the advice. The last few days the weather has been much nicer and sure enough the bike has been a bit more sluggish. Also gets stuck in a high idle until I blip the throttle and hard to get into neutral. I looked at the plugs today and they are dry black. I am assuming the previous owner changed the jets since its running rich with pods. My question is can I just lean out all four air screws the same amount and be good? Which way do I turn to make leaner?

what do the rpms do when you open the throttle vs. what does the speedometer do?

if the clutch is slipping, the rpm will increase with little or no change in speed. if you want to see a slipping clutch, get going in first, then pull the clutch in, red line it, and dump the clutch, if it's slipping, the revs will slowly decrease as the speed slowly comes up, if it's not slipping, you'll wheelie a bit as the revs drop really quick.

keeleydavis said:

Thanks for all the advice. The last few days the weather has been much nicer and sure enough the bike has been a bit more sluggish. Also gets stuck in a high idle until I blip the throttle and hard to get into neutral. I looked at the plugs today and they are dry black. I am assuming the previous owner changed the jets since its running rich with pods. My question is can I just lean out all four air screws the same amount and be good? Which way do I turn to make leaner?

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Essentially no.
You need to see what jets you're running and compare to others with pods.
Looking at the plugs isn't really that helpful If they have been in there forever under various riding conditions. You need to put new ones in and the go ride at specific throttle and then do plug chops to determine if you're rich or lean.

and opening the throttle on a pre accelerator pump cb750 will make it fall flat on it's face, they ran fairly lean at cruising in any case, the later carbs used a pump to enrichen the mix when opening the throttle. running pods is just going to make it worse, i tuned mine with the stock airbox (only way I could get it close to the 12.5:1 a/f ratio over most of the range), pods just destroyed the airflow going into the carbs and cost a bunch of power

SONICJK said:

Essentially no.
You need to see what jets you're running and compare to others with pods.
Looking at the plugs isn't really that helpful If they have been in there forever under various riding conditions. You need to put new ones in and the go ride at specific throttle and then do plug chops to determine if you're rich or lean.

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pretty much the only way to tune that bike is years of experience or this http://www.ebay.com/itm/Wideband-Air-Fuel-Ratio-Gauge-w-Bosch-O2sensor-Green-White-0-5v-output-EVO-serie-/310650983731?pt=Motors_Car_Truck_Parts_Accessories&hash=item48543dd533&vxp=mtr
I've found almost anyone running pods on a 750 has a 750 running slower than it should be

Roc City Cafe said:

pretty much the only way to tune that bike is years of experience or this http://www.ebay.com/itm/Wideband-Air-Fuel-Ratio-Gauge-w-Bosch-O2sensor-Green-White-0-5v-output-EVO-serie-/310650983731?pt=Motors_Car_Truck_Parts_Accessories&hash=item48543dd533&vxp=mtr
I've found almost anyone running pods on a 750 has a 750 running slower than it should be

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Agreed but he can at least tell rich or lean with a proper plug chop.
On a side note I really want a wide band with a data logger.

Can I ask what you mean by had the carbs. serviced??? A while back I had hauled another p.o.s. home with stuck carbs. Foolishly I took it to a local stealership... after a few days I was told the bike was ready. The bike fired and I could ride it, but all the same issues you talked about. I quickly found that all they did was sync the carbs and make a few adjustments, which would have been fine if it hadn't sat for 15+ years in a museum. I quickly found out through a site like this, that most of the rubber in the intake system was worthless. Intakes leaked, butterfly shaft seals were hard and disintegrating quickly, needle jets toast. Yeah it ran, but had issues that everybody chalked up to it being an old bike. I bought a Manometer and all the pertinent seals and parts needed. Once finished, it blew the tanks off several sport bikes.

When you're riding along and you crack the throttle, does the r.p.m. raise, then drop as the power catches up? If so, it could very well be the clutch is slipping or in my case the cable was routed wrong under the tank and holding things up.

If it's not the clutch, get out a can of carb. cleaner, let the bike idle till warm, then start by spraying around the intakes... Idle change??? Go to the shafts that connect the carbs and spray.... Idle change???? I have been surprised how many times my old bikes had carb issues that ended up being shaft seals, because the stealership, even if they rebuild the carbs. some mechanics are too lazy to actually dismantle the carbs. they spray, replace parts with whatever comes in the little baggie and bolt everything back up and sync. Problem is you can sync a set of carbs with issues and it will run, it just won't run correctly.

I know this is going back to basics, but I've learned the easy stuff is usually needed to be lined up before you get into the deeper stuff for it sll to work properly and sometimes you get lucky and the easy stuff is the cure....

SONICJK said:

Essentially no.
You need to see what jets you're running and compare to others with pods.
Looking at the plugs isn't really that helpful If they have been in there forever under various riding conditions. You need to put new ones in and the go ride at specific throttle and then do plug chops to determine if you're rich or lean.

Click to expand...

The mechanic basically replaced all the carbs with better condition carbs since the ones I had were cracking. He is pretty trustworthy and yes he did give me shit about running carbs he also mentioned he couldn't believe it was running rich still, and I'm not sure why I dint ask if that was fixable.

The plugs were new about 6months ago. I have a carb sync gauge but was wondering if it would basically sync all the carbs to be the same richness, or should I dial them leaner and then sync?

I tried the method of pulling in the clutch and the bike quickly returned to speed. If I give it a ton of gas, the engine revs but the bikes speed pics up later.