Heavy throttle

[guitarkev66]

Well I have been out of town working for 7 months; while I was gone I have purchased many parts to put my sandcast back on the road.  I replaced the tires, chain(diamond)and sprockets(17/45) , rubber intake boots, brake lines, and throttle cable.  The bike runs fantastic and handles great, the only problem I have is the throttle is very heavy to twist.  It felt a bit heavier with the old cable, which is why I replaced it.  I figured it would get lighter with a new cable.  It didn't,  it really starts to cramp my hand after ridding for a few miles... I have had over 10 cb750's K0's through f models and none had this issue.  Is this typical for a sandcast?  I have the cable routed correctly and the carbs are very clean.  I love ridding the bike its performance is definitely better than all of my other 750's ,by a lot....  Any advice on making the throttle twist easier?  Thanks

[Steve Swan]

Hmm....  given what you wrote, it sounds like you've covered your bases, so not sure what to say about your heavy throttle operation.  With the cable unattached to twist grip and the 4 carbs, check for ease of operation.  Check to make sure the junction box moves freely.  Lubricate the cable with "DriSlide," even if the cable moves freely.  Disassemble the junction box, clean and lightly grease.  check to make sure the throttle tube turns freely on the handlebar with the switch housing screws tightened.  Compare your cable routing to the routing as per the enclosed Service Bulletin.  make sure the cable is not having an undue bend as it passes by the coil and then through the triangular part of the 3 frame tubes.  make sure the 2 shorter cables attach to carbs 2 & 3 and the 2 longer cables attach to carbs 1 & 4.  if all this fails to ease operation, then perhaps file some relief on the frame as seen in the SB.

[Sam]

As Steve said, check to make sure your cable moves freely when it is strait. If so, then I would look at three things:

1. Your cable routing. Bending them too much can cause this problem. I wrestled with this more than i thought I would!
2. Check to make sure the slides move freely in the carb bodies.
3. Check to make sure the slide springs are not binding anywhere.

Let us know what you find!

[Sgt.Pinback]

Had the same problem. New cables, carbs sliders cleaned.....in the end it was the rubber from the throttle. It was too deeply pressed into the handlebar so it didn't move free.

[Erling]

Maybe the original weaker springs might help?
I only used the stronger ones for 5 minutes!
On my 90S BMW Dell Orto carbs I used to sort of tie together some turns of the spring.
Think I ended up with 4 tied together and it still managed to shut the carbs.
And I know of the handlebar rubber been pressed too hard in.
Erling.