Topic: PD42B Choke Plate Screws

[DHuffman]

Hey guys,

In the interest of learning, I completely disassembled my '77 CB750F carbs (PD42B).  Later, a local motorcycle guru informed me about the tiny choke plate screws being penned and that I probably made a huge mistake removing them. Fortunately, the threads in the connecting rods seems to be in good shape, but the scews themselves will not thread back in.  I have looked in the forums, and saw someone mentioned that information on where to buy them was in the FAQ. However, I believe the links are outdated, as most lead to errors, and one leads to a page of various sizes of screws. 

What size/thread pitch screw is used for the choke plates?  Can I cut/grind the ends off of mine and use lock-tite instead?

I apologize if I missed somewhere in the forums where this information is - still learning to navigate these catacombs.

[HondaMan]

Yes, they are "recoverable", in fact they are quite soft. That's how Keihin peened their ends over the first time. I have many times taken a small file to the burrs to let them find their way back in: try filing off any 'flower' on the end, then you will see a slight "V" groove in the end of it where it was splayed. Clean the edges from the high points of the 'Vee" and you should be able to get them back in. I usually start them a thread or two (once I had their tips going smoothly) and then add some red Loctite and run them in. It will set up in about an hour to hold well.

[CycleRanger]

I am not 100% sure but I believe the choke plate screws are 3mm x .5 x 6mm JIS screws.
(I'd go with stainless metric hex button heads if you get new ones.)

When I was rebuilding the Mikuni's on my XS650 I bought a whole bag of the screws I needed for the choke plates from mcmaster-carr.  (Not the same size screws as for the Keihins but you get the idea.)

[Spanner 1]

Please note !... before you snug up those choke plate screws, operate the choke on and off a few times and tighten the plate screws with the choke all the way ON. This 'sets 'each plate in it's throat as the screws have a little 'play' on the plate holes. It's common for the PD carbs to fail to choke all the way especially on carb 3 and 4 as the mech. is ( weakly ) spring coupled and the plates jamb in the off position with the choke knob pulled all the way on at the handlebar ....

[HondaMan]

Please note !... before you snug up those choke plate screws, operate the choke on and off a few times and tighten the plate screws with the choke all the way ON. This 'sets 'each plate in it's throat as the screws have a little 'play' on the plate holes. It's common for the PD carbs to fail to choke all the way especially on carb 3 and 4 as the mech. is ( weakly ) spring coupled and the plates jamb in the off position with the choke knob pulled all the way on at the handlebar ....

Yeah! What he ^^^ said...it's a real pain to make it work right, otherwise.

[scottly]

Please note !... before you snug up those choke plate screws, operate the choke on and off a few times and tighten the plate screws with the choke all the way ON. This 'sets 'each plate in it's throat as the screws have a little 'play' on the plate holes. It's common for the PD carbs to fail to choke all the way especially on carb 3 and 4 as the mech. is ( weakly ) spring coupled and the plates jamb in the off position with the choke knob pulled all the way on at the handlebar ....

Yeah! What he ^^^ said...it's a real pain to make it work right, otherwise.

2+ to what they both said!^^^
Better to not remove them in the first place.