revving out

[hybrid350lc]

Hi all

I have a hybrid350 lc
With the what seems a not uncommon hanging on to revs problem
I have tried a list of fixes so if you can add any ideas I would appreciate any help
A bit of background
4l0 bike 31k motor std no porting
Hy tech reads just fitted
New crank case seals and bearings
Fresh rebore and new pistons out to 1.0mm over
All new gaskets and seals throughout the motor so as far as I can see no air leaks
Just fitted new ypvs valve seals too
Carbs are std 31k type 260 mains 22.5 pilots
I have tried 27.5 and 37.5 no joy there
Changed float heights
New coil and caps
New plugs again
New YPVS seals
New throttle cable
I am running auto lube
Tried with airbox pod filters and no airbox
Tried 3 different sets of carbs
Bike is hard to start revs ok from cold but when on a ride shut the throttle off and the revs stay up or go up to 5k+ but if I keep the clutch out I can get the revs back down by running it in gear until the revs are down to lower level does not make for a nice ride
It seems that as I am idling along at a slow pace that the bike is hunting juddering back and forth too.
The bike has always done this before and after the complete rebuild

So any help please
Getting quite cheesed off and light on new inspiration

[MarJay]

It's doing it after a rebuild? Then I'd guess at either an air leak in the carb rubbers or a poorly adjusted throttle cable. Are you sure the throttle slides are in the right way around? I had the same trouble on my 350 YPVS when I hadn't quite got one of the slides in the right place...
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[spanners]

You may need to turn out your fuel screw/s.
If you are sure nothing is catching/snagging, then it may be the case that you are running lean.
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"Insert profound quote here"

[pits]

It sounds like you haven't adjusted your post properly, the problem is your thread is in the wrong area, it should be in the workshop not in here.
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00:32:08 Blau Zedong: yes, i am a massive CB400 fan and collector
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[c_dug]

I had the same issue with my TDR 250 and it turned out to be the carb mounting rubbers were cracked. Only tiny barely visible cracks to begin with but it made a noticeable difference.

Also triple check the throttle routing just in case something is snagging somewhere, had a similar issue with my CBR which could quite easily have been mistaken for an air leak. Was caused by having rotated the throttle body on the bar just slightly but enough to take the slack out of the cable. Was an absolute arse ache to get it to move freely again.
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[stinkwheel]

I would also go for an air leak at the inlet rubbers.

Get it idling and squirt some EZ start round the carb rubber area. If the revs increase, you have an air leak.

Worn slides can cause a similar problem by getting jammed in the throttle body at an angle by the faster air rushing into the carb at full throttle but it looks like you've got that covered. That said, you tried different carbs but did you keep the same throttle valves?
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[hybrid350lc]

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[hybrid350lc]