Hi tickover

[reasty]

My mk1 has suddenly developed a strange fault.
On start up it would normally revert to normal tickover in the time it takes me to put my helmet on.
This weekend I was on a trip to Luxembourg and Belgium and every morning when starting, the engine raced to about 3k and stayed there for about 20mins when it then reverted back to normal settings. Throughout the days it remained fine but would repeat the trick on 1st start up in the morning.
Any ideas anyone what it might be?

[Skids]

Wax idle unit?

[reasty]

Thanks skids - can you elucidate a bit - is this a mechanical bit that can go awol and is easy to replace?

[Skids]

Originally Posted by reasty

Thanks skids - can you elucidate a bit - is this a mechanical bit that can go awol and is easy to replace?

That's not a piece of kit I've had to mess with much previously. Swapped one out on my 08 800 for a new one but other than that, I'm sorry I can't help you.

Not sure if this would affect it but have you balanced the starter valves recently? That engine benefits from regular (~ every 4k miles) balancing, as well as some other relatively minor engine work which helps smooth out the low rev response.

[popkat]

There's a few possibilities. the fast idle or choke appears to be mechanical, they look to have plungers the same as carbs have choke plungers, the 4 are connected by a link rod, it's possible this is seized or another part in there, to check would mean to remove the throttle bodies and inspect them.
There's a temperature sensor which is normally in the airbox this usually sends a signal to the ECU telling the plungers to open, a new sensor would be needed but check the connection is not corroded first. It may be though that they work off a vacuum, if so check the vacuum hoses for splits.
Lastly it could be a problem with the ECU itself.

It could be difficult to diagnose, first check the temp sensor connection if it looks ok then remove the air box and see if you can get to the plungers/linkage and hoses (if this is how they activate) check all is good and spray some lube in there, AC90 is good. If you can't see then you'll have to remove the throttle bodies.
If it all still looks good and seems to work ok then you'll need to replace the temp sensor, after that it could be a case of finding a known good ECU and trying that (a friend with the same bike would be most helpful there)

These are all the things I would check first, it doesn't mean that the problem isn't something else though.
Best of luck with fixing it. Post up the outcome if you can 

[reasty]

Got the dreaded call from the dealers today - it's the wax idle unit - 576 of your finest English sovs to replace. The bike is an 11 with low mileage - they don't come across it very often, nearer 70k than 17!

Oh well luv the bike so no option than to get it done😂

[popkat]

wax idle unit £118.46 plus about £10 postage... seems a lot of labour cost to replace the part 

part number 3 on the diagram. https://www.fowlersparts.co.uk/parts/5962844/vfr800-crossrunner/throttle-body

.

[Skids]

Tank off, airbox off, throttle bodies off then pfaff around trying to reconnect the hoses.

It would take me longer.