wr400 wont idle

[manther]

'99 wr400, won't idle. Everything was fine. It's a new bike to me. So naturally I decided to do a few upgrades...

Here's what I've done. ( I know I did alot of changes all at once, but my bike has been half taken apart for weeeks now because parts would show up out of order or not at all).

First take:

Put yz cam with auto decomp on

put on an aftermarket pipe (pro circuitT4)

Still ran fine and idled, but had valve slap because

At first I over adjusted the valves (just by one or two shim sizes).

Next take:

(Did all these at once because I had a lot of down time while I was waiting for my new shims, every thing else showed up quickly)

Ordered narrower shims, and new timing chain, and decomp plug, and new air jets a 100 and a 60.

Put new timing chain on.

Put on autudecomp plug.

Opened up the airbox.

Cleaned and re-oiled the air filter

Took the carb off and looked at the jets in it.

Found a #48 pilot and a #190 main.

Replaced the 190 with a #170.

Took the AIS octopuss off and took the boot collar off to replace the air jets and found out OEM Thumper talk store sent me the wrong air jets. (they sent me the ones for a wr450), so I put the ais back on and the carb back in.

FINALLY shims show up. Installed them.

Put bike back together...

This is when the bike stopped idling. It runs as long as I have the choke pulled out (idles kinda high though), or if I keep the throttle open a little bit. But it doesn't run real smooth when driving it up and down the street. It pops a little bit. Anyway. Also when I was taking the carb off for the last time I noticed this spring on the ground... Not sure where this spring goes... I thought It might go where the throttle meets the carb but no... If you see in the second picture THAT spring is still there...

[manther]

Also I forgot to mention that I did the wr yz plastics conversion... Which means I put the YZ subfram on my bike. Which means the pro circuit silencer meets up with the header pipe a little less than perfect. you can actually see it in the second picture. Could a slight exhaust leak cause my problems? Could any kind of air leak be causing the idling problem? I've been pretty carefull to get the carb boots back on tightly each time.

[SXP]

'99 wr400, won't idle here's what I've done:

First take:

Put yz cam with auto decomp on

put on an aftermarket pipe (pro circuitT4)

Still ran fine and idled, but had valve slap because

At first I over adjusted the valves (just by one or two shim sizes).

Next take:

(Did all these at once because I had a lot of down time while I was waiting for my new shims, every thing else showed up quickly)

Ordered narrower shims, and new timing chain, and decomp plug, and new air jets a 100 and a 60.

Put new timing chain on.

Put on autudecomp plug.

Opened up the airbox.

Cleaned and re-oiled the air filter

Took the carb off and looked at the jets in it.

Found a #48 pilot and a #190 main.

Replaced the 190 with a #170.

Took the AIS octopuss off and took the boot collar off to replace the air jets and found out OEM Thumper talk store sent me the wrong air jets. (they sent me the ones for a wr450), so I put the ais back on and the carb back in.

FINALLY shims show up. Installed them.

Put bike back together...

This is when the bike stopped idling. It runs as long as I have the choke pulled out (idles kinda high though), or if I keep the throttle open a little bit. But it doesn't run real smooth when driving it up and down the street. It pops a little bit. Anyway. Also when I was taking the carb off for the last time I noticed this spring on the ground... Not sure where this spring goes... I thought It might go where the throttle meets the carb but no... If you see in the second picture THAT spring is still there...

The spring looks like it came off the arm of the decompression shaft that comes out of the head. As you've removed the shaft and plugged the hole, don't worry about it.

[maxtherat]

It sure sounds like a plugged pilot jet, but it could be from the valves being too tight. Did you remove the throttle cables from the carb when you removed it? It sort of looks like the spring that goes on the accelerator pump linkage. Not sure though.

[manther]

The spring looks like it came off the arm of the decompression shaft that comes out of the head. As you've removed the shaft and plugged the hole, don't worry about it.

Dude you totally right! When that spring showed up I had my "removed from this bike" parts box right there. I bet that's the auto decomp spring, and it just fell out of that removed parts box...Now onto the no idle problem... Can tight valves really cause idling problems? I messured the gap and put a certain size shim in. (went to 172, 172, 172 from 178, 179, 178) on the intake side... Got valve slap... Bumped it up to a 175, 175 175Valve slap gone...

[maxtherat]

Just look in the manual and, yes, there is a very similar looking spring that goes on the push rod link lever assembly(accelerator pump actuator). Page 4-15 in 2001 manual.

[manther]

It sure sounds like a plugged pilot jet, but it could be from the valves being too tight. Did you remove the throttle cables from the carb when you removed it? It sort of looks like the spring that goes on the accelerator pump linkage. Not sure though.

Yeah I thought the piolt jet was the issue as well. I pulled the carb and pulled the pilot jet and blew through it with carb cleaner. I can hold it up to the light and see a little pin hole that is clear all the way through... Not sure how tiny the pin hole should look though. (About the spring though, I'm pretty sure now that it was just left over from my removal of the auto decomp lever).

[maxtherat]

I don't think the valves are causing you idle problem, but I do know the slap can be caused if the buckets are getting stuck. This can happen if they are not put back it the exact same spot. Slap will go away if you have no gap and the cam lobe is always in contact with the bucket. Did you remove the slide from the carb. I have heard you guys putting the plates in upside down and their bikes would not idle. I'm no expert, just my .02.

[manther]

I don't think the valves are causing you idle problem, but I do know the slap can be caused if the buckets are getting stuck. This can happen if they are not put back it the exact same spot. Slap will go away if you have no gap and the cam lobe is always in contact with the bucket. Did you remove the slide from the carb. I have heard you guys putting the plates in upside down and their bikes would not idle. I'm no expert, just my .02.

You may or may not be an expert but neither am I. I'm just glad to have someone else to help think of things... In my searching of TT archives I also read about guys putting the slide back in upside down. Unfortunatley I didn't take the slide out.

[manther]

How bout jetting and the pilot and idle settings? I've started my pilot screw at 2 turns out. I also tried 2 1/2, and 3 screws out. It's getting richer as I turn it out correct? Also I have played around with the idle adjuster enough times now that I can no longer remember where it was at. How bout this... When I keep it from dying by holding the throttle on, and run it down the street, it pops alot... Is that a symptom of being too rich or too lean?

[SXP]

You may or may not be an expert but neither am I. I'm just glad to have someone else to help think of things... In my searching of TT archives I also read about guys putting the slide back in upside down. Unfortunatley I didn't take the slide out.

It wouldn't be something as simple as adjusting the idle up a little bit, would it? All the changes you made might just require the idle to be bumped up a tad.

[manther]

Forgot the mention I also did the grey wire mod... At the same time I did all the other mods.

[maxtherat]

My last though before I give up: Did you remove the throttle position sensor from the carb or did you unplug it when the carb was removed? If you removed it then you need to set it according to the manual so that it has a certain amount of resistance, I believe in ohms.

[manther]

It wouldn't be something as simple as adjusting the idle up a little bit, would it? All the changes you made might just require the idle to be bumped up a tad.

Yeah, this could be the prob. I have played with the idle adjuster a little. What I haven't tried was opening it up all the way.

My last though before I give up: Did you remove the throttle position sensor from the carb or did you unplug it when the carb was removed? If you removed it then you need to set it according to the manual so that it has a certain amount of resistance, I believe in ohms.

When this problem first started I had not removed this... Sometime today while trying to solve this problem I did remove the sensor... Then like one minute after I removed it I read in the manual that I shouldn't have removed it... So.. I guess now I gotta go though a bunch of crap to solve THAT problem too huh...

[maxtherat]

Yes yo do. Try unplugging the TPS and see how it runs. Also, a 48 PJ seems a bit big for that bike. I would try a 42 or 45 at about 1.5 turns out

[manther]

Yes yo do. Try unplugging the TPS and see how it runs. Also, a 48 PJ seems a bit big for that bike. I would try a 42 or 45 at about 1.5 turns out

Can it run with out the TPS?

I've been starting my adjustment process with the idle screw at 2 turns. Could I just be too rich?

[maxtherat]

Yes, you should be able to run the bike w/o the TPS plugged in. With that size of PJ you could be too rich. Will the bike run with the fuel screw turned all the way in and the idle screw turned way up? If you can get it to idle then you have too large of a PJ.

[manther]

Yes, you should be able to run the bike w/o the TPS plugged in. With that size of PJ you could be too rich. Will the bike run with the fuel screw turned all the way in and the idle screw turned way up? If you can get it to idle then you have too large of a PJ.

Just got done reading up on how to solve my TPS problem. Seems I need to go buy a new tool to set it correctly. Looks like it helps the timing curve advance as the throttle position changes, to help with a more responsive transition between different carb circuits.... (That may be all wrong). Anyway I will unhook the TPS while I'm trying to solve this idling problem. (Can I just unhook the coupler? Or do I have to unscrew it from the carb?) Tommorow I will turn the piolt screw all the way in, and turn idle all the way wide open. I will report back... BTW though. a #48 piolt was what was originally in the bike, before I opened it up with an aftermarket pipe and a wide open air box, I thought the 48 was kinda rich when it was stock, but it ran ok.

[maxtherat]

Yes, you can just unplug it. I'm not familiar with the 99 so a 48 pj may be what it needs.

[manther]

Ok I tried it today with the TPS unhooked, the pilot screw bottomed out, the idle adjuster turned all the way up. When I start the bike with the choke on it starts up fine and is idling super fast. I let it idle like that for a second and push the choke back in. The idle speed goes way dow very quickly. It will now idle for almost a full minute kinda sporadically. Then it pops and dies. Then I hear this gurgle come from the gas tank. It sounds like a big air bubble surfacing. I mentioned earlier that I did the WR YZ plastics swap... This has an untested gas tank on it now... I wonder if gas flow is not smooth... But then why would it run ok with the choke pulled out. Also I have the throttle cable disconnected right now because it's frayed and I'm in the middle of replacing it.