sticky valves

[paul2397]

Hi all, i have not long just required a divvey 600, i have cleaned it up, got it through its mot,got the fuel pump working again"well i never, i paid for that one. The new problem i got now is that it does not want to go past 4000rpm in any gear, and somebody told me it could be "sticky valves.any ideas how i can rectify this?

[CD]

I think its unlikely. If valves stick open there would be all sorts of odd things going on certainly more than a mysterious power drop.

Firstly set the throttle position sensor (TPS).
Instructions are in this section.

New spark plugs might help.

While you are at it check there are no 33bhp restrictors. Although they shouldnt prevent the engine from revving.

If the bike has been off the road for some time the carb jets can soon get gunked up. Try a strong dose of injector cleaner and some posh 97 octane petrol with all the fancy cleaning agents.

Failing all that, the carb float chambers need to come off and everything blown through.
Having done this on a 600, its not hard job, *but you need a brand new #1 Posi screwdriver and push very hard before turning the thing. The float bowl screws are all too easy to chew up. If you have a local fasteners factors its worth swapping them out for stainless socket cap screws.

I found (the annoyingly advertised) Cillit Bang was very good for cleaning carb float bowls. Dont leave it on for too long as it can etch the metal. Every jet was taken out and blown through and the drillings were blown out. If you dont have a compressor a bike tyre pump with flexible connector tube is just as good.

*All usual caveats included concerning grannies and eggs.

[paul2397]

Thank you Chirodave, i will give some of these things a go.cheers

[m40man]

I agree with CD that 'sticky valves' are unlikely culprits for the symptoms you're experiencing.

Check that the choke cable is working OK, & opening & closing the carbs butterflies as it should.

One other thing that comes to mind, after you've satisfied yourself about the state of the carbs - Might be a failing coil? Would probably only be apparent under load, so whilst it could be responsible for the problem out on the road, as you try to accelerate, the bike would prob rev much better in neutral whilst stationery.

[CD]

Could be the coils but dont rush to buy new until the cheaper to fix stuff is sorted.

Do check the chokes. The plungers stick and let fuel through. Its a fuel tank and airbox off job, but easier than opening the float bowls.