Topic: Just got bike running, revs real high though, not sure why

[yitzac1990]

Hey all,

just got my 750K running tonight.  heres what all I did since buying it from the previous owner:

individual pod filters
MAC 4-1 exhaust
115 main jets
38 slow jets
completely disassembled, cleaned, and reassembled carbs with rebuild kits
new, rust free gas tank
new fuel line
custom "simplified" wiring harness with kill switch and start button on side of bike (no longer use the hand control buttons at all)

When I got the bike, rust filled the gas tank, fuel lines, and carbs.  but somehow the guy still got it to idle with choke on (guessing there was enough fuel trickling in to idle).  Now since the list above, I start the bike with the choke fully on, and it revs at about 8k RPM!!  when I take choke off, it idles at about 6k - 7k RPM and I have to just cut it off with my kill switch.

When I put the carbs back on and got the cables situated, I did notice that the throttles inside the carbs (the shiny things that move up and down?) were almost halfway open, even with the throttle cables fully "closed".  I didn't play with the adjustment of the throttle linkages in the carbs when rebuilding.  Any idea what it could be?

I tried uploading a video, but my internet is #$%* right now and wont let me...

Thanks for any help.

[dhall57]

Yeah the slides should not been open like that. No wonder the RPMs are up high. Your at half throttle or more.  Here is a pic of my K4 carbs right after rebuild and getting reassembled. See the big idle screw to the right is yours in this position or is it turned all the way in. See how the slides are down. Make sure you have the throttle cables hooked up and adjusted correctly. Be better off running a factory air box instead of pods also.

[yitzac1990]

yeah the reason I stated the conditions of the bike before I started working on it, is because when the carbs were still off the bike, before i connected the throttle cables back up, the slides looked like they were much further down and more closed.  i had to jiggle the throttle control to get the pull cable on, so it might just be a throttle adjustment?  will try to take a look today.  will also use the 1/8" drill bit trick to re-sync them.

i dont have the means to vacuum sync them right now, but once i get it running somewhat normal at my shop, im going to take it to a shop and have them vacuum sync, among other maintenance items that need attention that I dont feel comfortable attempting.

all the carb parts I ordered seemed to be very good quality parts.  no leaks as of right now.

also, i do understand the safety risks involved with relocating the kill switch.  the key is still in the stock spot, should be easy to spot in case of an emergency.  I can always add a "clean" aftermarket handlebar switch for a kill switch in the future, but I am going for a very minimalist/simple look and feel for this bike.  Im also thinking of even switching to single throttle cable, versus push/pull.

[yitzac1990]

well, got at least a temporary fix done and rode the bike up and down the street today!  I think the throttle cable is the wrong one for that bike (I can tell it was definitely replaced at some point), because the cable sheath was about 0.5" too long, which was making the throttle open at closed throttle.  I took my dremel out, cut off about 0.5" of the sheath and put it back in, and it fit pretty good!

also noticed the throttle return spring was a bit weak, so I made a little "extension plate" to hold the stationary side of the spring back further, putting more pressure on it to help return it back to closed.

Also, im sure its just because the current throttle control is crappy, but for some reason it takes a LOT of effort to get the throttle open!  I have to squeeze the handle really hard to twist the throttle, and there seems to be some lag.  im going to replace the grips, throttle, cables, clutch lever and brake master cylinder, can anyone suggest a good throttle control to get?  would the following items work?

http://www.dimecitycycles.com/satin-black-oem-style-single-dual-throttle-assembly-78-handlebars.html

http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-cables-honda-cb550-throttle-cable-02-0155.html

http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-cables-honda-cb550-throttle-cable-02-0156.html

P.S. - I will be putting clubman handle bars on this bike, I know that will affect the positioning of the controls/cables.