Idle changes when bike is hot

[kerrfunk]

Choke the bike to start it when its cold, release the choke and let the bike warm up, idles at around 1100 rpm. Good
But after riding the bike and getting it good and hot, come to a stop...then bike idles around 2500 -2700 rpm.
Is this normal operation?

My bike acts similarly. Idles around 1100 cold, then after five miles on the highway, idles around 2K.

 

[Guest]

If you don't have full compression by 600 miles, more miles probably won't fix it.

Isn't that the truth. Break in done properly takes very little time. I rode my GSXR1000 home from the dealer, went out on a back road and did maybe 6-8 hard pulls to progressively higher RPM in 3rd gear. Break in was done, change the oil and carry on.


Mark

 

[Sandy]

As mentioned set the idle to 1100 when warm. Cold start ir with the choke and gradually reduce choke to keep the idle between 1500 - 2000. After about 30 seconds you should be able to ride away with part choke and turn it off within a minute or so. It will idle a bit low until fully warm. Such is life.

 

[ehkmcveh]

I'll take that as a no. Had a similar hanging idle situation last week; turned out to be an unnoticed slightly bent valve. Pulled hard wide open. A leak down tester picked up on it better than a dynamic compression test.

If you don't have full compression by 600 miles, more miles probably won't fix it.

uhhhhh
Cylinder 1 - 70psi
Cylinder 2 - 50psi
Cylinder 3 - 50psi
Cylinder 4 - 70psi

These are cold, but cant see much gains from a fully hot bike... well darn

Shims all look good except for 5... which is 0.13mm.

Its just weird though because it rides really good, just a hanging idle and a little stumble in the mid range ( but no stumble if I twist the throttle slow)

 

[BigD_83]

uhhhhh
Cylinder 1 - 70psi
Cylinder 2 - 50psi
Cylinder 3 - 50psi
Cylinder 4 - 70psi

Those numbers look suspiciously like what I've seen when I forget to hold the throttle open while testing...

 

[Sandy]

Those numbers look suspiciously like what I've seen when I forget to hold the throttle open while testing...

I was thinking something didn't look right. Warm it up and hold the throttle open. The reading are too even for them all to be that low and even. When you lose compression like that it's rarely on all cylinders, or maybe a bad gauge.

 

[jsandidge]

A bad gauge is a possibility. I have a cheapo HF gauge that always reads exactly 90 psi on all 4 cylinders, hot or cold.

 

[ehkmcveh]

Those numbers look suspiciously like what I've seen when I forget to hold the throttle open while testing...

the carbs are off right now..., so full throttle is there.
It a rental tool so I dunno, the bike seems to have a lot of power so I am not too worried about it
Going to carry on

 

[BigD_83]

That is strange, then. It shouldn't really run with compression numbers that low.

Fingers crossed you get this sorted and it turns out to be something simple.

 

[ehkmcveh]

Alright shims are all within spec now, did some shuffling. Thank god for notes!
I split the head cover gasket though, ordered a new one so should be hear in a week

Guess I should lube that gasket with motor oil before putting it on, it got bake on and destroyed when I opened the head
oh well

 

[Guest]

Alright shims are all within spec now, did some shuffling. Thank god for notes!
I split the head cover gasket though, ordered a new one so should be hear in a week

Guess I should lube that gasket with motor oil before putting it on, it got bake on and destroyed when I opened the head
oh well

I put a thin coating of grease on both sides before installing a new one and they usually last 2-3 valve check cycles before leaking or tearing. Make sure you are torquing the valve cover bolts correctly as well. Over torquing them crushes the gasket and makes it leak faster.


Mark

 

[ehkmcveh]

I put a thin coating of grease on both sides before installing a new one and they usually last 2-3 valve check cycles before leaking or tearing. Make sure you are torquing the valve cover bolts correctly as well. Over torquing them crushes the gasket and makes it leak faster.


Mark

Ok yeah, just some all purpose grease. Ok ill give that a shot. Thanks

 

[ehkmcveh]

Ok back from vacation, gonna pick up gaskets tomorrow (closed today )

Found the timing on the bike out, can't confirm exactly how much because I was playing with it quite a bit, looked like a couple teeth. Its good now
My question is, is the an interference engine or not? Could the timing out cause damage/ bad compression?

 

[hannibal]

Yes it's an interference engine. Don't ask me how I know. Incorrect timing can certainly cause damage and poor compression readings if the intake valves are open on the compression stroke.

 

[ehkmcveh]

Yes it's an interference engine. Don't ask me how I know. Incorrect timing can certainly cause damage and poor compression readings if the intake valves are open on the compression stroke.

Hmmmm... I have heard the odd ping come from within the engine....o boy. Wonder if a valve bent??
I am putting it back together to day,

Re checked shims, some are 0.10mm on the outake.

 

[hannibal]

I think your timing would have to be pretty far off to bend a valve. I don't think 1 or 2 teeth would be enough.

0.1mm isn't bad. Many folks prefer to run on the looser side, even above the recommended upper limit of 0.08mm.

 

[steve murdoch]

Hmmmm... I have heard the odd ping come from within the engine....o boy. Wonder if a valve bent??
I am putting it back together to day,

Re checked shims, some are 0.10mm on the outake.

A bent valve does not "ping". It will bang and clatter....and as hannibal mentioned, don't ask me how i know.

 

[ehkmcveh]

Ok got the timing sorted, added quite a bit more power!
Idles a lot better now too, dances a bit between 1100 rpm and 1600rpm. This is when the engine is good and hot. I'm good with that
Ended up getting new airbox intake boot clamps and engine boot clamps also, it seems to be sealed pretty good. Returns to idle a lot better

Did another plug chop. For the Pilot circuit ( 4th gear at 30MPH for like 4 miles ), the plugs are now black! Incredible difference

Set the pilot fuel screws to 1 1/8, air screws 1 1/2
This is the worst one.

Mid is little white ish (2nd clip from bottom), Full is white ,mostly on cylinder 2 and 3, have 105 mains ordered

 

[Guest]

Idles a lot better now too, dances a bit between 1100 rpm and 1600rpm.

Good to hear things are improving. The idle shouldn't dance much at all, so you still have some tweaking to do. On my 1100E I have a digital tach and the warm idle varies about +/-50rpm at most from 1100rpm. On an analog tach you would barely see the needle moving off 1100.

Did another plug chop. For the Pilot circuit ( 4th gear at 30MPH for like 4 miles ), the plugs are now black! Incredible difference

Set the pilot fuel screws to 1 1/8, air screws 1 1/2View attachment 52765
This is the worst one.

Mid is little white ish (2nd clip from bottom), Full is white ,mostly on cylinder 2 and 3, have 105 mains ordered

Realize that modern unleaded fuel doesn't read like the old stuff. It runs much cleaner and tends towards always looking lean until you are slobbering rich. If you get any brown on the insulator at all and a dark ring on the steel plug body at the threads you are doing ok with it. GregT had a post on this a few weeks back somewhere here and he knows his stuff when it comes to tuning these machines.


Mark

 

[ehkmcveh]

Realize that modern unleaded fuel doesn't read like the old stuff. It runs much cleaner and tends towards always looking lean until you are slobbering rich. If you get any brown on the insulator at all and a dark ring on the steel plug body at the threads you are doing ok with it. GregT had a post on this a few weeks back somewhere here and he knows his stuff when it comes to tuning these machines.


Mark

Nice, I will have to give that a read.
My main circuit shows the metal tip white on cylinder 2 and 3, so I'm pretty certain that it needs a 105 (102.5 currently)
Don't want to cause any damage after all this work lol . Sure rips though!