Idle changes when bike is hot

[BigD_83]

102.5 Main
15 Pilot

What do you mean too dry, should I be oiling it ever season?

I don't think you'd have to oil it every season, but certainly every time you clean the filter. Given your location, I'd expect a lot of hot, dry days during riding season, so perhaps your filter has dried out a tad. Wouldn't hurt to have a look.

As for the jets, that is the stock pilot air jet, and 1/2 size up on the main. That pretty much meshes with what I've been told about headers.

[ehkmcveh]

Are the valves adjusted? Compression checked?

Well I rebuilt the top end about 600 miles ago.
I checked all valves there and changed about 4 shims... all within the 0.03mm to 0.08mm
Compression I have not done yet, want to give it time to marry to the cylinder...I'm sure its good cause it hauls ass full throttle!

[ehkmcveh]

anyways, been talking with some other guy in my hometown
He suspect dirty carbs, so got them ripped apart and going for a 24 hr bath... Changed all 0-rings last year but did find on that was pinched on carb 3 pilot air screw... not sure if that would be the cause of the hanging idle!

[John Park]

Well I rebuilt the top end about 600 miles ago.
I checked all valves there and changed about 4 shims... all within the 0.03mm to 0.08mm
Compression I have not done yet, want to give it time to marry to the cylinder...I'm sure its good cause it hauls ass full throttle!

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.

[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.

Well I don't have access to a leak down compression tester..... probably should find one since I'm this deep already.
Bent valve hey! what do you think/suspect that was from.

I could do a compression test tomorrow and re-check the valves while I wait for my jets to finish the carb dip bath.

[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.

[mmattockx]

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