Topic: Throttle 1 into 4 problems

[lucky]

I should probably make a VIDEO...but when removing a slide to get at the slide needle here is what you do.

Remove the threaded ring from the top of the carb.
Pull out the slide.
then....
lift the spring out of the slide and keep it cupped in your hand.
By squeezing the spring in your hand(bunching up) the spring
you will now be able to un hook the throttle cable from the slide.
Do not let go of the spring or it will fly across the room.


You re install it the same way.
Bunch up the spring in your hand with the throttle cable in your hand. The throttle cable sticking all the way through the spring .
The throttle cable should stick out 3-4 inches through the spring, so you can easily hook the end of the throttle cable into the groove in the slide . Then slowly release the bunched up spring into the slide.

[Sandy]

Lucky:

I would like to add the fact that one must be sure the needle set plate is sitting on top of the needle and clip with the spring eventually holding the needle and the needle set plate in place.  And, why yes , I had a few springs fly across the room along with a needle set plate, closely followed by a tool or two .  And as a precaution, before I inserted the slide into the carb, I made sure the needle was properly set (not moving up or down) and somewhat loose.  Thanks to everybody here, I am well on my way.

[Sandy]

Hi everybody:

Had to take a bit of time off, but I am back at the task and here is what I have.  I followed Lucky's instructions to the tee - I made sure all the T's in the idle adjustment screws were exactly the same, where the top of the T lined up with the line on the carb body and the top of the T was almost touching the carb body - pic attached.  When I re-installed the carbs, the slides came out differently - #1 and #3 were exactly the same, but #2 and #4 were quite a bit higher in the carb.  The slides were installed exactly the same way as the pic - did not use different slides into different carbs.  I would have thought that all the slide openings should be even kinda like the attached pic.  Have I done something incorrectly?  Should I start moving the slides around until they are even in the carb openings?   Should the slides be even along the carb openings?  Thanks to all in advance.

[crazypj]

I would not trust the mechanics they have now at those dealerships because they know nothing about these bikes.

I'll agree with that 100%.
I worked at MMI as an instructor, the manufacturers don't want to have 'obsolete' stuff taught and to be honest, in the majority, the 'kids' don't want to learn about 'old junk' (although the very few that do will be real good techs, maybe 1 in 100?)

 It looks like cable adjusters in carb tops are at different heights?
I would adjust them so slides are 'right' and not worry about heights being the same
I like the early carbs from performance standpoint but they really are a pain to keep in sync (they will never stay 'perfect')

[70CB750]

You are at good starting point for the vacuum synchronization.  There is a good how to procedure in the manual, every carburetor is little bit different, thats why you need to hook up gauges now and synchronize it while the engine is running.

[Sandy]

Hi everyone:

After installing the carbs and adjusting the slides I found I had a problem with the #4 carb.  #'s 1, 2 and 3 all resembled the bench sync openings but #4 was way too high in the carb body.  After taking the #4 adjuster to the max, this slide was still 1/2" higher than the other 3 that resembled the bench-sync heights.  It is like the #4 cable is not long enough. Started the bike and it quickly raced to a high RPM without my touching the grip, so I hit the kill switch.  Fiddled some and tried again, same result.  Today I will see if the cable to #4 has come out of its socket at the connector and I think that might be the problem.  Does anybody here have an opinion as to how wide the slide openings should be before start-up??  I was shooting for the bench-sync openings but I am probably wrong .

crazypj:   Thanks for the recommendation - I will try to make the adjusters all the same height as all four are now all over the place and try again. By way of background, when I received the carbs from TMP, the adjusters were all the same height.

Once I get it to idle, I will hook up the gauges.  Will post all results.

[Killer Canary]

I would not trust the mechanics they have now at those dealerships because they know nothing about these bikes.

Again, hear, hear! Do as much research as you can on your own for part numbers. Don't trust the minimum wager behind the counter to get it right.

[lucky]

All 4 slides should be bottomed out

It does not matter if the adjusters on top of the carbs are different heights.
The cables can come out of that junction box so check on that.

Try to get most of the slack out of the throttle cable between the throttle and the junction box AFTER you have the carbs all bottomed out.

The cutaway on the bottom of the slide is designed to give  just enough air to let the engine idle. A simple system.

Now after all the slides are bottomed out put your finger in each carb and turn the throttle slowly.
Make sure that the second you start turning the throttle the slide begins to open.
This is VERY important!!!

Then you can sync the carbs.

Remember to adjust the idle by using the cable adjuster up by the throttle NOT by turning the idle screws!!!

When you synced the carbs you use the individual idle knobs/screws to get it in sync.
Do not use them anymore after the sync procedure.
Just use the cable adjuster up by the throttle to set idle . Then you will always have carbs in sync.

See what I mean?

[Sandy]

Lucky:

Thank you for the response.  At the grip, the "play" is 1/4", which I am comfortable with.  The cable, all 4 carb cables and the connection box are free and unbound - the grip turns all 4 carbs easily.  I need to find a way to get more cable length - I will try to explain.  This AM I removed the attaching nut on the top of the adjuster on #4 in an effort for more cable and the slide will still not hit bottom.  The other 3 do.  I started it again with the lower #4 slide and although it still starts instantly, it also revs instantly - no idle. What I will try next is in the handlebar area - lots of room for adjustments as the cable wire coming around the triple tree has lotsa room and is free.  Lucky:   what you detailed in your excellent thread about carb/cable setup, I will try at the idle adjustment before it attaches to the grip as perhaps that is now my problem - it idles toooooo high!!!!

The attached pic is what I am dealing with - I figure the problem now is at the handlebar end.  I will keep everybody posted.

[Sandy]

The problem was the #4 cable had jumped out of its slot at the connection box.  Fixed, reassembled, readjusted the slides and started it.  Started fine and idled just a bit high, but I will fix and then I will hook up the vacuum gauges to see what else I can find.  A humongous thank you to everybody for all their responses .  Yeah, I will post a pic with the motor running and the gauges attached - should be forthcoming.

[70CB750]

Great!  Well done.

[crazypj]

The #4 cable may be in the 'wrong hole'?
As far as I remember, the inner carbs have much shorter cables although all the inner wires should be withing 1/16" of each other ( I have seen them with 1/8" + variations though)

[lucky]

Yes that is right.
The two inner cable housings and cables are shorter than the out side cables from the junction box to the carbs.


Good work!

[Sandy]

Well, I still have some issues , but they will be easy to rectify.  I will be posting a pic of the sync that I will be performing soon, but I decided to post a few pics of what the finished product will look like.  I cannot begin to thank you all enough for all your advice, manuals, instructions and pics - I would not have been able to accomplish this rebuilding without your help.

[70CB750]

Great job, she is a beauty, Sandy!  Definitely keeper 

[lucky]

Thanks for reporting back. so often the forum members spend time giving out help and we hear nothing again.

Thank you. Beautiful bike too!

[Sandy]

This post will be the final one for me on the throttle problems.  I cannot begin to say how much all of your responses were of tremendous help to me.  While the 69 is now being ridden, there are a few other issues that should be addressed - coils might be going bad (and after 44 years I am not surprised), the front wheel seems to be out of round and I need to repack the baffles.  Thanks to all of you and the information you provided the bike starts immediately, idles at about 1,200, the throttle response is crisp and bottom lining - everything works including all electrics.  So I just gotta tinker a bit more.  Have attached 2 pics of the finished product alongside its younger (and bigger) brother .  Thank you all very much.