Help! Poorly running 750k

[amc49]

There may be no pins, I can't remember any in the 550 now that I'm forced to think about it. The internal linkage on those may well hold slide in place good enough to work and a pin might interfere with the linkage moving freely since it works in a plane, the two planes off or arguing might tend to hang slide.

I too expect slide pins but might wanna wait till the guy reports back again................the lowest part of the slide faces forward FYI. The other side is cut with a higher cut.

 

[amc49]

Went back and checked, the 550 for sure has carb slide pins to lock slide position in dead nuts. My apologies to any who I have mis-steered.

 

[Stah1one]

Okay, so after months of boards studying and not being able to work on my motorcycle I'm finally done and was able to dive back in. I replaced the insulator boots with brand new ones and changed the air filter as well hoping that this would help with vacuum leaks that I definitely had. It definitely is helping, but not enough to make the bike run well. I still starts and idles just fine, but still dies when you open the throttle completely. The difference is, now you can feather the throttle a lot and the bike will start to pick up enough that it will run. There isn't a HUGE difference in it's performance before, so I wonder if I still have vacuum leaks somewhere? I tried spraying starter fluid where the air box connects to the back side of the carbs and got no change in idle speed. As for there being slide pins in the carbs I don't remember seeing any. I haven't taken the carbs off again, but I know they were definitely all the same when I took them apart and I don't remember seeing slide pins in any of them.

 

[madmtnmotors]

Well, a picture of the carbs looking into the inlets (from the airbox side) would be in order here. The slides used in the PD "Keyhole" carbs on the 77/78 K models do not have a guide pin for the slides. This means the slides can be installed backwards. Need a picture of your carbs from the inlet side, with the choke open, to see if the slides are oriented properly. Take a couple shots with all four in the picture, then take a close up of each carb inlet.

 

[amc49]

If idling fine at pure dead idle then not vacuum leaks, they affect idle first.

Slow timing can do that, as well as blocked carb circuits for right off idle, the transfer holes that expose as soon as slide lifts. Even if accel pump working, if those holes blocked same result as no pump working. Be advised the accel pump can work and still be messed up,k it must work INSTANTLY with even the slightest throttle movement open. Any delay and you get a balk there. So, not enough that it merely works, the timing on it has to be right. FYI, I mod them on the DOHCs for quicker action and more pump shot.

If needle clip in wrong spot can do it too. Provided that one is adjustable.

Lacking dwell can too. Setting point gaps by feeler is so stone age now. I set by old school dwell meter ONLY, they are dead on then and matched perfectly.

 

[dirtdigger]

You always have to check that the ignition advancer is moving free, they do stick from old grease and rust.

If needles are stock in the keyhole carbs they will only have one slot for the e-clip, have to adjust them with small shims.

Agree, feeler gauge is only a preliminary adjustment for points, they should always be done with a dwell meter, will also let you know if the ramps that open the points are getting worn, which can happen from lack of the appropriate point slide lube. I bet most people now days would look at you funny if you ask for point rub block grease lol

Problem with setting point gap with feeler gauge is that it is easy for inexperienced people to not know they are opening the points with their gauge because of the weak point springs, its far to easy for people to set the gap wrong.

How do the plugs look? Are they very black? Very white?