Hard throttle pull...?? HELP

[Bladerunner]

Hey everyone,

New to the site. I just picked up a very nice '78 GS750 yesterday in Omaha, NE. I was looking for a KZ900 or KZ1000 or a mid '70's CB750, but those bikes are out of my price range.

I was pleasantly suprised to find the GS750 I bought is everthing those other bikes are, looks/performance/reliability, but at a much better price point. I think the GS series of bikes are fantastically overlooked right now. Maybe the best kept secret in the "classic" bike market. Anyway,...I diegress.

I really like my new GS750 with one exception! The effort to rotate the throttle is horrendous. You have to have forarms like King Kong to hold the throttle in place while cruising down the highway. I rode the bike to Omaha (bout 20 miles) and couldn't wait to get there 'cuz the strain on my hand was almost too much.

I have lubed the throttle cables and I took the throttle tube off the bar and smeared a light amount of grease on the bar before re-installing the throttle tube. This did nothing to lessen the effort to rotate the throttle. And when releasing the throttle, the "taps" slam shut with authority! So I know the cables are not binding anywhere.

Maybe I'm just used to modern bikes with their 'easy' throttle pull, but I sure hope there is a simple fix for this.

Thanks in advance for any help.

Trent

 

[bobthebiker88]

My old CB550 was the same way. you get used to it, wrist and forearm muscles build, and eventually your modern "easy twist throttle" feels like broken cables.

 

[Adler]

Maybe take a look at the spring on the carbs, could be a PO substituted something more hardcore.

 

[Guest]

Will your throttle snap shut from any position , lock to lock ?
If so , you'll just have to "man up" .

Cheers , Simon .

 

[Colin Green]

Maybe take a look at the spring on the carbs, could be a PO substituted something more hardcore.

Will your throttle snap shut from any position , lock to lock ?
If so , you'll just have to "man up" .

Cheers , Simon .

What they said

 

[tom203]

My 650 throttle feels too strong for me- but you'll get use to it! If you're ambitious, take off tank, check cable routing and operate carbs at that end to convince yourself that throttle cable is not the problem.

 

[midnightcafe]

Hmm:-k as long as the throttle returns with a "snap" then it should be working just fine. Maybe you can rotate the throttle assembly backwards on the handlebar so that you need less wrist motion to open the throttle once it's comfortable for you.

 

[NoH2Oh]

Bladerunner, seems like you and I are twins...I also originally was looking for a nice Kaw Z or KZ before I bought my GS750 as I had never been a fan of Suzuki, but the $$ here in the Chicago area is nuts in regards to the Kawasaki's. Found my GS really local, may have paid a bit too much for her, but much less than a comparable KZ. After having her I am glad I went with a Suzuki, was never aware how good they really are.


Anyway, my throttle is just as you have described, I thought maybe I was just getting too old and soft. I have seen it before stated that the non-cv carbs are much stiffer than the cv carb models.

 

[bwringer]

Yes, the older VM carbs have a significantly higher effort throttle than the new CV carbs. Plus, they have the added drag of the double-cable system.

With all that said, it was once common to see VM carbs with the closing cable removed and a stronger return spring added. (You see, the slide can stick under certain high-flow conditions on VM carbs, which could be dangerous, so they needed a system for ensuring that the slides would always return. Hence the closing cables on stock bikes.)

Sounds like you do have both cables, so perhaps you either need to just get used to it or see if a stronger than normal spring has been fitted. I believe the stock throttle return spring is still available. Or, perhaps you can find a slightly weaker spring -- as long as you have the closing cable in place, you should be OK.

Another tactic is to fit thicker grips. Assuming you don't have wee little fingers, thicker grips will give you more leverage without causing any other problems.

 

[koolaid_kid]

You could also try lubing the cables, it might help a bit.

 

[tkent02]

They really shouldn't be very hard to pull. I can't really notice any difference in pulling force between throttles on VM carbed, CV carbed or modern FI bikes. Maybe a slight difference that could be measured, but not something you would actually notice.
Something is wrong with your cable, or the spring, or something.
Have you looked under the tank to see if there is any poor routing or kinks?
Any cable adjusters come apart? Any old worn looking cables?
If the cables are worn internally, all the lube in the world won't free them up.
Also old lube which has collected a ton of dirt will bind them up.

 

[Bladerunner]

Thanks for the suggestions fellas,

I really am starting to love this bike. For the $$$, the GS's really can't be beat! Suzook did a really good job of copying the KZ's, and for the money I could have two GS's for one KZ and from 20 ft. away who can tell the diff?

Anyway, I am not done trying to figure out why the damn throttle is so horrendously stiff. I have been riding since 1996 and racing since 2003 (Now on a Ducati 848 and 2005 GSX-R1000) and have owned almost 30 different bikes of just about every design.

I have had a couple of "vintage" bikes, namely an '82 KZ1000J and a '74 CB450K7, and neither required the kind of effort it takes to keep the throttles open at any speed. I have had a couple of riding buddies try it out and they laugh and say "holy ****" when they see how hard it is to open the taps on the GS750. I just wonder if someone in the recent past has put a heavier spring on the carbs. I'm going to take the tank off tomorrow and see if everything is O.K. and then look into putting a 'softer' spring on,...if that is even an option.

Unfortunately, this throttle thing could be a deal breaker. If I can't find a way to lessen the pull on the taps, I may re-sell the bike. I like doing long distance rides of 10 hours in any one day, and this bike just simply not do with the amount of effort it takes. My hand starts to cramp at 1/2 an hour, so there is no way I could make it to St. Louis and back which is a run I often make.

Keep the suggestions coming guys, and if I find a solution, I'll post it up post-haste. For now here's a pic of my 'new' GS750.

 

[tkent02]

Nice bike, it's easy stuff to fix. Cables or a spring, nothing to it.

 

[koolaid_kid]

I owned one of those new, and the situation you are describing clearly indicates a problem (duh). Since you going to have the tank off, I strongly suggest that you first remove the cables from the carbs.
Once off, twist the throttle and see how difficult it is to move the cables. It should be effortless. If not, remove the cables from the throttle. Try to slide the cable from within the housing. It should be effortless. If not, lube and try again. If still not, replace the cables.
If they do move effortlessly, put the throttle back together without the cables. Twist it. It should be effortless. If not, take it back apart and look for places it may be rubbing. Lube it a bit with some general grease. Try again.
To reiterate, take the carbs out of the equation first. If a problem is found, check the cables. If no problem found there, check the throttle itself. If no problem found there, it is the carbs themselves.
Best of luck.

 

[OzJavelin]

I owned one of those new, and the situation you are describing clearly indicates a problem (duh). Since you going to have the tank off, I strongly suggest that you first remove the cables from the carbs.
Once off, twist the throttle and see how difficult it is to move the cables. It should be effortless. If not, remove the cables from the throttle. Try to slide the cable from within the housing. It should be effortless. If not, lube and try again. If still not, replace the cables.
If they do move effortlessly, put the throttle back together without the cables. Twist it. It should be effortless. If not, take it back apart and look for places it may be rubbing. Lube it a bit with some general grease. Try again.
To reiterate, take the carbs out of the equation first. If a problem is found, check the cables. If no problem found there, check the throttle itself. If no problem found there, it is the carbs themselves.
Best of luck.

What he said. Check the whole mechanism to see what's happening. I'd suggest something is binding somewhere .. maybe even just one of the cables is kinked or something. That is too nice a bike to sell without taking a good look first.
Good luck!!

 

[Bladerunner]

O.K. fellas, here's the scoop.

There is some kind of interference at the throttle tube or right-side switch housing, or both. I completely disassembled the throttle mechanism, cables, and removed the spring from the carbs.

The "pull" cable was shot, and there is/was noticable resistance in the cable even when completely free of the bike. It was replaced with new. Next, the throttle/carb opening mechanism at the carb bank rotates freely. The "push" cable was free of any resistance, so I reused it. The switch housing and throttle tube rotates freely around the bar without cable hooked up, but snug down as if properly mounted. So far so good, and I was ruling everything out; one-at-a-time.

Here is what I believe is causing the problem: 1 - The throttle return spring is quite heavy. I wonder if someone has put an unusually heavy spring on the carb bank at some point within the past 32 years. I will be going to my local ACE Hardware tomorrow to find a lesser but similar return spring I can use. 2 - Once the throttle cables are secured back at the housing/tube juncture, and secured to the bar, there is very, very noticable drag at the throttle tube once the cables are tensioned. There is no housing-to-tube interference, but the bar underneath is corroded (but greased). I belive that the combination of an unusually heave return spring plus drag between the throttle tube and bar are causing my problems. I have a new chrome set of superbike bars to install, and with a lesser return spring I hope to have this problems solved!

My bike (pictured above) is a fantastic machine, especially for what I paid vs. a KZ900/1000 or CB750, and it would be a shame to sell it for this small, seemingly easy fix. I'll post more results tomorrow.


Trent

 

[cyclefvr2]

beautiful bike!
i have used light grease on the throttle tube between the bar, but you might be best off with dry lube "graphite" , it will stay consistant, in cold weather
im betting your cable angle is off a bit, right out of the tube area, keep them loose ,and see where there easiest pulling and returning, i had a similar prob with my kz1000, i also soaked cables in trans oil,so the weather wouldnt rust them "morning moisture ect..."
also the routing is criticle for easiest angle! above the tank mount or under it, or on the left side of the frame, or right side, i tried a few different ways

 

[tatu]

Very nice bike
Stick with it it cannot be anything huge.
I agree with you the Suzuki was always a better machine.
I have no idea why Kawasaki's command more money but for sure they do.