Idle question

Hey everyone
I recently did a top end gasket and valve adjustment on my 81 KZ550. I got it all back together and can't seem to get the idle right. Before I took it apart it idled right around 1500 rpms. I set it back to 1500 at idle after the engine work and now the rpms take off to 5000 when I blip the throttle. I tried setting it to 1000 which is too low and stalls the bike. Normally I'd say it's a vacuum problem but I can't find any leaks. Right after I put it back together it would only fire on 2 cylinders because I pinched some wiring by accident. I corrected the problem and it starts a little bit quicker but it still takes longer than it did before I took the engine apart. There is no clunking, smoke, or weird noises coming from the engine like there is something wrong with the rebuild. Does anyone have and ideas of what I can look at to fix this?

Sounds like the bike is too lean. Sucking false air, no air filter, no airbox, something.

BTW, spraying crap around the carbs is an unreliable method of finding vacuum leaks. Only gross leaks will respond to this method.

The bike is completely stock with the stock air box, filter, and air suction system. I'll pull a plug to check how it's running

I pulled one of the plugs and attached a pic of it. Does it appear to be running lean? If so what are the steps to fix it?

Plug looks a bit lean to me, further pointing to likely manifold air leaks as above. My 550 was idling rough, and 'hanging on' when blipped. I suspected an air leak, the manifold rubbers ok but so I used a light smear of sealant on the flange faces and it sorted it nicely. Better replaced with new if you want a 1 step fix.

I wonder if you ever had that running right at 1500 rpm minimum idle speed, should be around (guessing) a 1000 rpm .

The carbs were never synced so i assumed that was probably part of it. The intake boots were just replaced last summer so they should still be in good shape, however I'll try to put a sealer on them to double check

The intake boots were just replaced last summer so they should still be in good shape, however I'll try to put a sealer on them to double check

Don't, do that last resort, new boots shouldn't be a problem...but re-tighten the two m6 mount bolts and clamps that can work loose.

Your carbs could be massively out of balance stifling one or two of the pots, not such a problem
when the throttles are openened. .

nickleo373 wrote: The bike is completely stock with the stock air box, filter, and air suction system. I'll pull a plug to check how it's running

The clean air paraphernalia isn't needed and may be removed to rule it out as the possible source of air leakage.



Good Fortune!

I've been debating removing that for a long time but never did because I have no idea what it does. I did find some cracks on the ends of the hoses for the smog system so I think I will remove it now. Does anyone know the hose sizes and the types of plugs I will need to link the two reed covers together ?

Good Fortune!

Alright as it turns out it was not a vacuum leak, however i ordered all the parts to get rid of the air system anyway. When i put the bike back together I accidentally screwed up the timing which was causing the bike to take forever to run. I pulled the valve cover back off and retimed it and everything seems to be working again.
Thanks everyone