Author Topic: High Rev (Read 1248 times)

bcscotty · « **on:** October 30, 2014, 12:48:48 PM »

Was going to work this morning and my 750 started a high rev no matter what position the throttle is in. No cables are pinched and there are no air leaks. Tried cranking this afternoon with the same result. Fire up then revs like i am dumping the throttle. I am confused as to what would be causing this problem.

flybox1 · « **Reply #1 on:** October 30, 2014, 12:52:19 PM »

need to tell us more about what recent service you've done to it....

ekpent · « **Reply #2 on:** October 30, 2014, 12:55:03 PM »

A slide does not have to stick much or be very high to make the revs go crazy. Anything jammed under the control arms/linkage can cause problems also.
Do you still have some play in the cable at the handlebar throttle ?

bcscotty · « **Reply #3 on:** October 30, 2014, 12:59:31 PM »

Only thing done was changing my needle depth. Had to lean it out to compensate for too big of jets and riding in the mountains. I did notice I could push the slides down slightly with the control arm fully down but did nothing to stop the rev.

ekpent · « **Reply #4 on:** October 30, 2014, 01:01:39 PM »

What year so we know which carbs.

bcscotty · « **Reply #5 on:** October 30, 2014, 01:02:05 PM »

Did ride over 700 miles in the past 5 days

bcscotty · « **Reply #6 on:** October 30, 2014, 01:03:01 PM »

73 carbs. 76f bottom end. 75 A jugs. 73 K head

ekpent · « **Reply #7 on:** October 30, 2014, 01:08:22 PM »

Round top carbs.Do you still have both the push and pull throttle cables ? Make sure the push cable is not acting up if you have it and you have proper play at the throttle grip. Probably have to pop off the tank and start checking things out. Do you have pods or stock airbox. If pods it would be easy to take them off and compare the slide height of the 4 carbs.

bcscotty · « **Reply #8 on:** October 30, 2014, 01:37:31 PM »

round tops. cables are good. pod filters. Did forget to do one thing after my trip and that was to check the oil. My tank was damn near empty

bcscotty · « **Reply #9 on:** October 30, 2014, 01:56:28 PM »

Found this piece under my number 2 slide. As many times as I have taken them apart, I dont recall ever seeing this part

harisuluv · « **Reply #10 on:** October 30, 2014, 02:06:43 PM »

That goes on your choke flap. If fills a hole in the choke that slides down. A pin and spring assy goes on to keep it locked in, did you find it? Cause you are already lucky that piece didn't get sucked into your engine, you still need to find the pin and spring.

bcscotty · « **Reply #11 on:** October 30, 2014, 02:27:13 PM »

pin and spring are MIA. Hopefully they just got blown out the exhaust pipe

ekpent · « **Reply #12 on:** October 30, 2014, 02:35:59 PM »

Might not be a bad idea to pull that spark plug from the cylinder from which that choke part was found to see if the tip has any damage incase the other parts went through the engine. As for just going out the exhaust everything has to get by a valve also and they move very fast

Look inside the pod also for the missing extras.

bcscotty · « **Reply #13 on:** October 30, 2014, 02:43:21 PM »

Yeah wasnt in the pod. But the thought of pulling my motor out again is demoralizing.

bcscotty · « **Reply #14 on:** October 30, 2014, 02:46:02 PM »

Think sticking a magnet in there might grab it out?

ekpent · « **Reply #15 on:** October 30, 2014, 03:09:01 PM »

If the spark plug looks good than that will be a good sign and other than that if the parts are not found just see how it runs. The parts you lost are ferrous.

bcscotty · « **Reply #16 on:** October 30, 2014, 04:18:42 PM »

Will do. Thanks for the input fellas. Always helpfully to a novice 750 junkyard builder

Dunk · « **Reply #17 on:** October 30, 2014, 06:16:21 PM »

Wow, never heard of those little reeds on the choke flaps coming apart! The spring or pin could be in the carb holding the slide from closing completely. If it swallowed a spring you might be alright as it's small and pliable, the pin could probably do more damage. Sorry to see your conundrum!

grcamna2 · « **Reply #18 on:** October 30, 2014, 06:31:01 PM »

I'd be fishing in that cyl. w/ a tiny flexible shaft magnet just to be sure.

bjbuchanan · « **Reply #19 on:** October 30, 2014, 08:00:58 PM »

Those choke flaps are a common failure on kz's, my buddy's 550 is missing three of them. It is usually the spring that breaks and then you lose the flapper. If you didn't find the parts in the pod they are in your exhaust by now, almost guaranteed.

There is no way they are just flopping around in the cylinder. Pull the plug, make sure it isn't bent closed and hope for the best. Those little parts won't blow an engine, they just get worked through, maybe scar some surfaces along the way.

The uncontrollable high rev could be from the flappers. You have essentially lost part of your choke. With that one down it is only like half a choke. Yeah if you measure volume technically it's different, yadda, yadda but just kinda think of that cylinder as only being half choked now because of the big hole there now. Are any more of the flappers missing?

Usually two of them is alright for cold weather, any more than that missing and you may have issues starting it on a real cold day, it won't choke enough. If one broke, the others may not be far along, who knows. It doesn't seem to be a common failure on our bikes tho, could have been a PO 'fixing' it

bcscotty · « **Reply #20 on:** October 31, 2014, 02:23:33 AM »

Yeah just that one is missing.

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Author Topic: High Rev (Read 1248 times)