Topic: 74 CB550K Carbs, NO acceleration.

[elfmagic17]

My Uncle had this bike before me andmessed up the carbs.? He took them apart and damaged one of the sliders on the inlet side,about the size of the corner of a straight tip screwdriver if you cut it back 3/16 of an inch. I think he sanded on the main needles a little bit too. My question is would this be enough to keep the engine from revving up at all at full twist? You can baby it up to about 3800RPM but that's all it will do and if you "nail it" it sputters and dies. Timing is good, I checked that myself. They seem pretty clean, the floats don't all seem to set right even with them measuring at the 22mm like specs say. Any ideas? Manifold O-rings? I'm Stumped!? Thanks in advance!

 Kenny

[Stev-o]

start with a full tune up.

[dave500]

they wont be sycned or anything either,ill bet theres more to it than that,out of sync carbs should still run half ok.go with meriggi on the tune up,always make sure ignition is up to scratch before chasing carb issues.

[TwoTired]

Yes, tune the carbs last.  Complete the entire 3000 mile tune up schedule and then deal with the carbs.  Tuning the carbs to an engine that isn't otherwise tuned to run well is foolish, imo.

Also, you will never be able to "nail it".  The carbs don't have accelerator pumps.  When tuned correctly you can twist the throttle up to one half total travel to get quite spirited or reliable acceleration in any gear.  Twist more than that and the engine will wheeze from lack of fuel, and likely die if the trans isn't in gear to keep the engine turning.

I would shop for replacement slides and needle, just to avoid headaches and doubt.  If the slide bore was scratched by the damaged slide, then shop for replacement carbs.  If he sanded the needles, what clip position did he use during reassembly?  Have the pilot jets been verified clean and clear?

Check that all the head pipes are hot.  These engines do struggle for RPM when the cylinders aren't all firing.

Report what's been done to induction and exhaust.  Any change from stock will have some repercussions regarding carb tuning.  And certainly book value carb settings no longer apply.

The stock bike would do the the standing quarter mile in just over 14 seconds, which is faster than most cars.

Cheers,

[elfmagic17]

Plugs are like new gap is good, I will recheck point gap and timimg, the needles were set on position 4 (4th from top) if i remember right if not then 3rd from top. Believe it has an older Mac 4 into 2 Turnout exhaust but it ran good on this system before. the jets all look clear but i guess the passages could be cloged. I love my Uncle but He really needs to stop "trying" to fix stuff on his own.

[Stev-o]

Plugs are like new gap is good, I will recheck point gap and timimg, the needles were set on position 4 (4th from top) if i remember right if not then 3rd from top. Believe it has an older Mac 4 into 2 Turnout exhaust but it ran good on this system before. the jets all look clear but i guess the passages could be cloged. I love my Uncle but He really needs to stop "trying" to fix stuff on his own.

Original airbox and clean filter?

[elfmagic17]

Plugs are like new gap is good, I will recheck point gap and timing, the needles were set on position 4 (4Th from top) if i remember right if not then 3rd from top. Believe it has an older Mac 4 into 2 Turnout exhaust but it ran good on this system before. the jets all look clear but i guess the passages could be clogged. I love my Uncle but He really needs to stop "trying" to fix stuff on his own.

Original airbox and clean filter?

Yes, also plugs are black like its getting too much fuel, like i said i don't know what my uncle has done but its very screwed up. Idles beautiful but just won't accelerate. Anyone think it would be a good idea to lower the needles a notch or two? I'm not familiar with tuning these carbs and I just don't want to waste anymore time taking them apart for nothing.

[elfmagic17]

Finally found out what my Uncle did! He had the connections for the new condensers grounded to the points plate instead on the other side of the isolators. Didn't see it before, don't know how, but when I found it it all made sense. I replaced the slide and carb body for the #1 carb to repair the damaged slide and broken guide inside the carb body, luckily my Brother-in-law had a set of parts carbs laying around to rob parts off of. Now I just need to get me a Helicoil kit to repair the other three carbs' stripped bowl screw threads.