Revs fall slowly - not enough engine braking

[stopintime]

Bike has been worked on, but it shouldn't be related. Things have been taken apart, so of course anything is possible...

Fast idle lever moves freely. Throttle cam slams shut. Throttle tube moves freely.

Idle is a couple of hundred revs higher, but the slow rev reduction is worse. Engine braking has become slow and progressive.

Where do I look?

[koko64]

Since the mehanical stuff like cables, throttle, etc are good then it could be an air leak. Be good to check the intake manifolds for leaks. I've heard of people forgetting to re-fit the idle synch port bolts which could be missing. Something may not be seated fully with the intake manifold or throttle bodies.

[stopintime]

Since the mehanical stuff like cables, throttle, etc are good then it could be an air leak. Be good to check the intake manifolds for leaks. I've heard of people forgetting to re-fit the idle synch port bolts which could be missing. Something may not be seated fully with the intake manifold or throttle bodies.

 

Where are those bolts?

[koko64]

You know the ones on the inlet manifolds that the manometer fittings screw into?

Could be a split in one of the manifold rubbers or not seated air tight.

[ducpainter]

Drop the idle to where it belongs.

[stopintime]

You know the ones on the inlet manifolds that the manometer fittings screw into?

Could be a split in one of the manifold rubbers or not seated air tight.

Nope, but how many can there be.... I'll have a look.

I'll check those too. Do I remember a DIY check ..... spraying starting fluid around the area and listen for fluctuating revs?

[koko64]

You reckon someone's adjusted it incorrectly DP?

Good idea to check for leaks.

Nope, but how many can there be.... I'll have a look.

I'll check those too. Do I remember a DIY check ..... spraying starting fluid around the area and listen for fluctuating revs?

Drop the idle to where it belongs.

[stopintime]

Drop the idle to where it belongs.

When the engine gets warm, the idle settles at ~1,500, but it takes time to fall from 2,500/3,000. I used to be able to control engine braking, but now there's a delay.

I do have a DIY old school idle control, but have never used it. I will check it.

[stopintime]

The old school idle stop screw isn't active.

Both synch port bolts are there. So are the air bleeds.

No loose attachments or visible damage to the intake rubbers.

I sprayed what I thought was starting fluid on the area with the engine running. It wasn't starting fluid - it was "One shot" carb/intake cleaner. No reaction.

[koko64]

What work was done to the bike?

[ducpainter]

IIRC, high idle will cause a slow drop, at least it does on a carby. Try to get the idle down around 1100, where it belongs, and go from there.

The old school idle stop screw isn't active.

Both synch port bolts are there. So are the air bleeds.

No loose attachments or visible damage to the intake rubbers.

I sprayed what I thought was starting fluid on the area with the engine running. It wasn't starting fluid - it was "One shot" carb/intake cleaner. No reaction.

Carb cleaner is a better choice than starting fluid.  If it didn't react, you don't have a leak in the area you sprayed.

[stopintime]

What work was done to the bike?

Cylinder and pistons. Complete top end service - which includes parts removal.

It was dyno tested. Don't know, but assume adjusted.

Maybe trim was adjusted...

I'll ask the work shop in a few days.

IIRC, high idle will cause a slow drop, at least it does on a carby. Try to get the idle down around 1100, where it belongs, and go from there.Carb cleaner is a better choice than starting fluid.  If it didn't react, you don't have a leak in the area you sprayed.

I don't know how to adjust idle. ECU?  Again; I'll ask the work shop what they did

[ducpainter]

I'm pretty sure that the idle speed is adjusted with the air bleeds, but I'm not a fuelie guy.

There may be a stop screw. Check with the shop.

[Howie]

Check the injector seals too.  Also could be slightly leaking injectors or the throttle plate not coming to it's proper position due to dirt.

[koko64]

How many turns out are the TB air screws?