Hi,
Got the 5VY (2005) R1 engine back in tha car again... it had its valves replaced, since the originals were faulty ones.
Anyway, test driven the car this weekend, the engine is sweet, runs very nicely.
But when I take my foot off the accelerator pedal, and depress the clutch, the engine spins up and only drops back to idle quite slowly. Each gearchange (with the clutch - when cruising) whenever I depress the clutch, the same thing.

I checked the pedal, it is not sticking, and returning nicely... the same thing with the accelerator cable.

What can it be? Any ideas? It surely wasn't the case before the engine has been taken out...
Thanks!
Gergely

Sounds like the idle is set too high (most likely), or you have an air leak between engine and tb's

Have you got a return spring at the engine end ? I had to fit one to my ZX9 engine even though it looked to return quickly without, it was not enough in practise so I had to rig a bracket and spring to stop it from staying about 3000 rpm

[Edited on 16/11/09 by Peteff]

Too much air or fuel getting into the engine, holding the revs up. Check the throttle butterflies close quickly and fully when you take your foot off the pedal. Check for air leaks on the inlet tracts.

quote:

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Originally posted by Peteff
Have you got a return spring at the engine end ? I had to fit one to my ZX9 engine even though it looked to return quickly without, it was not enough in practise so I had to rig a bracket and spring to stop it from staying about 3000 rpm

[Edited on 16/11/09 by Peteff]

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Cheers guys, I will have a good look.
The idle should not be the issue, if anything, it is set lower than it was before.
Anyway, I will check the return spring and the air leaks, too, and will let you know - but it won't before the weekend.
Cheers!
Gergely

If you need to check for air leaks, with the engine ticking over, spray some carb cleaner, or easystart around the inlet tracts, if you have a leak the rev's will rise as it sucks in the spray. HTH Ray

As above, the standard carb return spring was not designed to pul back a larger heavy cable and the weight/resistance of the pedal setup

Just remembered - I had this once and it turned out to be a frayed accelerator cable. It was just a bit too sticky to close the throttle quickly.

Hi Gergely

There is a small plunger near the bottom of the throttle bodies on each side. These are attached via a linkage to the thermowax. The thermowax ports tend to get corroded up or it may have a air lock.

If it is idling high and not returning very quickly this is most likely your cause.

It won't need adjusting just a clean. Email me if you need more info.

Cheers
Sonja

If it didn't do it before,then it points to an air leak or possibly the throttle cable hasn't been routed in exactly the same position ie a tighter bend in it

tony

Thanks guys for all the responses. We tried to rev the engine in neutral to see if this happens, and the revs dropped fairly slowly again. It turned out after some fiddling that when we installed the throttle cable, we have tightened it too much, without leaving enough free play in it. The last mm or half of return travel was slow and it didn't allow the engine to go back to idle quickly enough...
It seems fine now in neutral, but the stupid rain and fog means I couldn't test drive it yet... Maybe tonight!

Thanks again all!
Gergely

Got out for a half an hour blast last night - I didn't realise that the roads are this empty at night...
Something to keep in mind from now on I guess...

The revs drop nicely back to normal, so it seems that it really was only the stupid mistake of not allowing enough free play in the throttle cable.
Thanks all!!
Gergely