RPMs stay high after i rev it up.

[pinstripe_chuck]

It idles good at like 8 or 900 but when i rev it up it stays high. After about 10 -15 seconds it will come back down.

 

[Ironsled77]

Sounds like a gummy Carb or a cable in need of lube.

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[DetroitMuscle07]

800-900 is far too low for idle RPM, you want about 1200 at tickover. Also, you didn't state any specs for your bike. After you clean your carbs, clean them 2 more times. The passages and jets can become restricted with junk quite easily.

 

[fermatseye]

If clean carbs don't do it replace the auto-advance springs in ignition. Over time they lose there strength allowing the weights to swing out keeping timing advanced. Mike's XS has em.

 

[joe-wiseguy]

sounds like lean jetting to me. if they are cleaned and each time you rev it up without load it wants to stay high and slowly .....very slowly return sounds like lean fuel mixture. when under load and you are riding it and you rev it up while leaving it in gear and then release....... does it poppity pop all the way down the rev range? if so this is the next telltale sign of lean fuel jetting.

 

[nightowl49]

sounds like carbs need a good cleaning you probably have your idle set up high to make up for it so when you left off after high rpm your throttle plates donnt really close so it sucks enuff air to keep the revs up give it a good bath inside

 

[gordonscott]

sounds like lean jetting to me.QUOTE] what Joe and others have said, classic symptoms of dirty carbs/jets. Clean jets and carbs real good and you will be good to go

 

[pinstripe_chuck]

Ok its a '78 SE, with pod filters and shorty pipes. carbs have been cleaned and rebuilt with 127.5 mains and #42.5 pilots. When i ride it it dosen't pip and pop at all, it rides good and if anything i think its too rich cause there is soot all over my linkage and frame from the exhaust. it only does it when its in neutral. and i have replaced the advance springs too.

 

[Crab_Cake]

Ok its a '78 SE, with pod filters and shorty pipes. carbs have been cleaned and rebuilt with 127.5 mains and 42.5 pilots. When i ride it it dosen't pip and pop at all, it rides good. it only does it when its in neutral. and i have replaced the advance springs too.

doesn't that seem a bit small?

 

[txpowdercoater]

sounds like a vacuum leak to me. I'll bet those plugs are porcelain white at 127 mains on open pipes and pods.

 

[pinstripe_chuck]

I'll check the plugs. whats size mains should i start with?

 

[Tech7]

If I remember correctly, my mains on my 79 are 134.5. I also have pods and straight pipes.

 

[gggGary]

Carb synch time, in my experience that is often the cause of slow drop back to idle. The only reason I can think of for a 1200RPM idle is battery charging. I like idle get em as low as they'll go. With a properly set up choke a high idle is the tug of a lever away.

 

[txpowdercoater]

I would go richer (I have an 81, open pipes and pods at 145 mains and average 52 mpg's), I also would also check the mating surface of the intakes to the head. my bike did exactly as you described and it was sucking air. once checked, cleaned and tightened up, no more issues.

 

[bluebikerblan]

The easy's first.... check that your throttle at the carb returns at the same time as you
release it at the hand grip.....ie no drag or hang up of the cable in the sleeve. Clean the cable and control tube thoroughly, re-lube and check for smooth routing and no pinch points or sharp angles.....then on to the carbs if you've still got hang ups and delay. There's dirty gummy somewhere or where's maybe a little of all the aboves. Blue

 

[XSLeo]

Depending on weither the carbs are early or late 78's will determine the stock jets.
The early 78's had 122.5 mains, 25 pilots. With a Z-8 neddle jet, 4M1 needle, #3 slot.
The late had 135 main, 27.5 pilots. With Z-2 needle jet, 502 needle #3 slot.
You need to figure out what your carbs are. Then you can start with the stock jets and work from there.

 

[HooliganCycles]

Sounds like an intake leak (which would give u a lean mixture) spray starting fluid or something around ur intake manifolds, if the rpm's change u got a leak, that will definitely make ur rpm's stay high for a while

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