Anther idle topic, tried everything

[Jim417mx]

Alright,I broke a ring in my STOCK motor at redbud national a few weeks back, I just put a 13:1 CP piston and new cylinder in my 2007 ltr450. It starts fine if I hold the throttle, but it does NOT idle unless I have the throttle cable adjusted out far. The second I mess with the idle screw or the throttle cable, it dies when idling at low rpm.

**When removing the throttle body I did try un-hooking the choke cable from the throttle body because I thought it was the throttle cable, so I'm thinking this is my problem because I pulled it out and found the spring and parts inside, maybe I didnt put it back in right, or all the way? Is the black nut supose to be tightened all the way down ? Info on its specs would be appreciated. I also loosened the throttle cable at the throttle body, but right now the throttle cable is set to have little play in it as noted in factory specs.**

Here is what I have tried so far:

Timing is perfect, I am 100% sure it is perfect.
New 100 Octane Fuel.
New Spark Plug gapped to spec, (tried old plug also).
Idle screw @ factory spec and in/out both ways.
Throttle cable turned in/out on both adjusters.
Adjusted choke cable in/out at both adusters.
TPS is where its supose to be at, the mark lines up.
Piston rings gapped to specs.
All bolts torqued to specs during piston install.

Any help on where to start will be greatly appreciated, I will start from scratch as long as somebody knows what they are talking about.

One question I have , is should I try adjusting the TPS? or leave it where its at? Thats the only thing I havent touched.. I have about 5 hours into this thing trying to get it to idle since I finished putting the new piston in..

EDIT: I had the quad idling at high rpm and as I walked away I can hear the valves ticking... I know this is known for hard-starting and poor idle, but it idled fine before I broke my piston ring. When I broke my ring it idled poorly, but thats because of the broken ring, or so I thought? My motor feels like it has plenty of compression when revving it, maybe not enough to idle? Why wouldnt it idle now with a new piston even though it idled with the old piston?

[motomxman450]

DId you check the swirl filter?

[Jim417mx]

No I didnt check that, Its at the dealer now, suprisingly they do good work and dont screw you over like most dealers.... this is only the 2nd time I've ever had to take a quad to a dealer for work in 8 years, i feel like a dummy when I cant fix my own quad

:(

EDIT: Well, turns out theres not enough compression... sooo I'm guessing a peice of the piston ring got caught in a valve or something along those lines.. time to spend more money:mad:

[hanes17]

Did you do any reprograming after installing the new piston. Any time I have installed a high compresson piston in any of my ltr's I have had to have it reprogramed.

[omararacing26]

check the small grey hose on the back side of the throttle body if it isnt hooked up to the oxygen sensor (by the airbox) or if has a hole in it it wont idle or barely run

[bigbad400]

dont take offence to this i just dont want you to overlook something so small.... have you checked your air filter?

outerwears socks DO go bad too if you have an older one it will restrict the air flow.

althow symptoms are backwards of a dirty filter many of the fuel injected quads i have rode do that because the fuel is under pressure and its actually richening it out due to lack of air flow. make sence....?


just a thaught since everything else checked out.

also was this compression test done with a real tester, and licensed mechanic? or a good quad mechanic anyhow? most quads and bikes have a decompression mechanism on the cam, if its stuck open it wont build compression, they are there for ease of starting the higher compression motors.... it opens one of the exhaust valves slightly and lets the cylinder decompress so that it can roll over faster on the intake stroke and closes again befor the compression stroke alowing it to fire. but i dont know if this quad even has one. again just another thaught.

[Jim417mx]

I ended up taking it to our local dealer, turns out 3 of the valves were "mushroomed inwards" due to lack of valve jobs/shimming. They said they put the biggest shims they could in there and its still not right, so I need new valves. I guess thats what I get for just racing my quad all year and not shimming the valves throughout the season , Oh well, that just means its time for an ATP head :D . Thanks for everybodys input though!

EDIT: I just pulled my head off and let parts washer solvent sit inside the "dome" while the head was upside down, you could literally watch the solvent slowly seeping through. I then removed the valves and you can see the black marks where they were not sealing up on some sides. Definitly time for a new head!