Replaced leaking petcock: bike will start but doesn't idle

Bike: 2002 DRZ400S

 

Long time lurker here and am posting now that I've tried everything short of removing the carb.

 

Basically, I bought a DRZ400 a week ago. The test ride went fine though it had some backfire on deceleration - no big deal, and the seller made sure to point out that the petcock was leaking a bit - being inexperienced with vacuum petcocks, I figured the fuel hose just needed replaced.

 

Fast forward a week and I've replaced the petcock with a manual one and plugged the vacuum line. Now the bike will not idle at all. I've tried having the throttle stop all the way in, all the way out, and everywhere in between and it still has the same issue - it'll start up, rev quite high, then if I don't rev it with the throttle it dies.

 

When revving it with the throttle it sounds like it'll be fine, but when I stop it'll die almost instantly. If I keep revving it'll start to sound bogged then eventually will die.

 

I made sure the vacuum hose was completely plugged with a snug bolt. One other thing is that the fuel outlet on the new petcock is quite smaller than the stock one, but tightening the clasp seemed to give a good seal.

 

Here's the replacement petcock: http://www.amazon.com/gp/product/B009B07YYK

 

Anyone ever have this issue or have any ideas?

Does your oil smell like gas?

Yes, probably the oil is contaminated with fuel.  Change the oil.

You may need to clean or replace the carb pilot jet

Get a proper cap for the vacuum nipple on the carb.  Bolt in the vacuum hose is never the right solution.

Thanks for the responses.

 

I changed the oil and filter and it did smell of gas, so I got my hopes up that it was the problem. Nope. I have it all back together and I'm having the same issues. It's almost like it's unable to pull fuel in, as it takes a good 20 seconds of the engine turning, me sitting for a minute, then trying again just to get it to start, rev high, and stall. I also got a bit of backfire from the choke (I'm not sure if this was where the backfiring came from, but I felt the warmth).

 

Anyway, it looks like I'm going to have to clean and rejet the carb. How do I pick out the jets? The bike has a full Yoshimura exhaust and the 3x3 mod, would this change which jets I should put in it? (this is more of a side questions since I'll just Google around for the answer).

 

Thank you

Thanks for the responses.

 

I changed the oil and filter and it did smell of gas, so I got my hopes up that it was the problem. Nope. I have it all back together and I'm having the same issues. It's almost like it's unable to pull fuel in, as it takes a good 20 seconds of the engine turning, me sitting for a minute, then trying again just to get it to start, rev high, and stall. I also got a bit of backfire from the choke (I'm not sure if this was where the backfiring came from, but I felt the warmth).

 

Anyway, it looks like I'm going to have to clean and rejet the carb. How do I pick out the jets? The bike has a full Yoshimura exhaust and the 3x3 mod, would this change which jets I should put in it? (this is more of a side questions since I'll just Google around for the answer).

 

Thank you

Did you just cut the 3x3 hole and not rejet the carb? That could be your problem..

What elevation are you at? (Sea level etc)

Something else to think about would be removing the enricher.

If the bike is used and you purchased it with the exhaust and 3x mod most likely the carb has been jetted. It would be an asset to you to pull the carb and open it up and investagate what is really in it jet and needle wise. Also check the diaphram. While in there check the float needle, seat o ring and float height.. Give the carb a good cleaning. Does it have an aftermarket Fuel screw too??? Make sure you have no vacuum leaks. I bought a petcock from ebay and noticed the small ports. I drilled them out larger and changed the tubes by putting the ones from my stock petcock in it. That makes sure your reserve stays the same. Those little plastic ones were way diff than stock.

Did you just cut the 3x3 hole and not rejet the carb? That could be your problem..

What elevation are you at? (Sea level etc)

 

I bought the bike with the 3x3 mod and exhaust added. It didn't run too well (had some backfiring), but I'm almost positive it was rejetted for those mods. I'm in DC which is 1-150ft (1 - 45m) elevation but will sometimes ride through the rolling hills of WV/VA/PA (up to 3000ft/1000m).

 

Something else to think about would be removing the enricher.

 

What/where is the enricher? When looking it up most results are of people asking what the enricher is.

Removing the enrichener applies only to the DRZ400E with the Keihin FCR carb.  The S model also has an enrichener (usually called an air cut-off valve) but it is not easily removed.  I suppose it is possible it is defective but not likely.  As long as the spring is under the cap, the only thing to go wrong with it is a punctured diaphragm.  You can look at all of that when you remove and clean the carb.

If the bike is used and you purchased it with the exhaust and 3x mod most likely the carb has been jetted. It would be an asset to you to pull the carb and open it up and investagate what is really in it jet and needle wise. Also check the diaphram. While in there check the float needle, seat o ring and float height.. Give the carb a good cleaning. Does it have an aftermarket Fuel screw too??? Make sure you have no vacuum leaks. I bought a petcock from ebay and noticed the small ports. I drilled them out larger and changed the tubes by putting the ones from my stock petcock in it. That makes sure your reserve stays the same. Those little plastic ones were way diff than stock.

 

I'm planning on pulling the carb, which as you know is one of those things that noobs like me try to avoid at all cost but I will hopefully learn it isn't too bad. To my knowledge it has the original fuel screw - that's the throttle stop, right? 

 

Removing the enrichener applies only to the DRZ400E with the Keihin FCR carb.  The S model also has an enrichener (usually called an air cut-off valve) but it is not easily removed.  I suppose it is possible it is defective but not likely.  As long as the spring is under the cap, the only thing to go wrong with it is a punctured diaphragm.  You can look at all of that when you remove and clean the carb.

 

Got it. I'll keep that in mine when going through the carb.

"Removing the enrichener applies only to the DRZ400E with the Keihin FCR carb.  The S model also has an enrichener (usually called an air cut-off valve) but it is not easily removed."

 

That is not my experience. I was pulling what's left of my hair off with the Mikuni on my recently acquired S, after

meticulous cleaning and checking it went on and on with bad idle, hard start, jerkiness, and what have you. After i read here on TT about removing the enricher spring, i did so (a five minute job), and the bike sighed with relief, everything's working great now. It's interesting to note that, with the spring on, there was plenty of decel popping, now none at all, so even what it was designed to do it was failing at.

 

I believe the air to the idle jet is too much, and cutting it off by closing the valve (removing the spring) provides a

much needed enrichment. I have left the diaphragm on for sealing.

 

Take it easy removing the carb, you can't be too patient. What I have done is remove the air bell belt (the steel fastener), and then push said bell backwards into the air box, allowing for the carb to be pushed back from the engine. Then twist it upwards (clockwise facing front) and then out with the front end, the rubber intake removed at the engine side (stays on the carb). After removing the cables of course.

 

If your oil smells like gas, then your petcock AND your float valve are (were) leaking. Do the raptor mod (get the manual petcock from the Yamaha raptor) and get a new float valve set.

With a bad valve no way a bike can run well.

 because the gas level in the carb will be too high

Edited by michaelks

No that is not the throttle stop. It is actually the Air/Fuel mixture adjustment screw. It is on the lower part of the carb. If your carb has been modded/jetted most likely the little cover cap has been drilled and removed in order to adjust the mix. If not you will need to remove the cap to adjust it. It is better and more convient to install an aftermarket a/f screw for easier adjustment in the future. If you want to cure some of these problem relatively easy and know you have jetted correctly I would recommend purchasing a JD Jetting kit part number JDS005 and a Keintech Fuel mixture screw for the Mukuni carb part number JDFM 050. The TT store offers them both I think. If not you can get them direct from www.jdjetting.com. Inside of the kit are some excellent directions. When I was a noob 7 years ago I did just that. Took me a little over an hour and haven't looked back since. Your only green at it once... :D

 

Always feel free to ask questions. You might get some difinitive answers and a lot of others as well... ;)

No that is not the throttle stop. It is actually the Air/Fuel mixture adjustment screw. It is on the lower part of the carb. If your carb has been modded/jetted most likely the little cover cap has been drilled and removed in order to adjust the mix. If not you will need to remove the cap to adjust it. It is better and more convient to install an aftermarket a/f screw for easier adjustment in the future. If you want to cure some of these problem relatively easy and know you have jetted correctly I would recommend purchasing a JD Jetting kit part number JDS005 and a Keintech Fuel mixture screw for the Mukuni carb part number JDFM 050. The TT store offers them both I think. If not you can get them direct from www.jdjetting.com. Inside of the kit are some excellent directions. When I was a noob 7 years ago I did just that. Took me a little over an hour and haven't looked back since. Your only green at it once... :D

Always feel free to ask questions. You might get some difinitive answers and a lot of others as well... ;)

Thank you!!! Would this kit work with a yosh full exhaust and 3x3 mod?

michaelks - interesting post.  I have not heard of the procedure to purposely remove the spring from the air cut off valve.  You are correct, removing the spring allows a lower vacuum signal on the diaphragm to close a valve cutting off about 1/2 the air mix to the pilot circuit richening the idle mixture.  I can't argue with what works but it is my experience on various motorcycles over many years that a properly functioning air cut off valve will kill the motor if the spring is removed.  I have to think there is some other problem in your carb if that procedure improves the idle. But hey, if it works, it works.  I may have to experiment with this idea.

 

You do need to leave the diaphragm for sealing the cap and so that you are not mixing manifold vacuum with the idle air circuit.  I don't know what would happen if you did that.

Would this kit work with a yosh full exhaust and 3x3 mod?------Yes.  Not only will it work, it is highly recommended and nearly mandatory.  Best way to re-jet for intake and exhaust changes.

Yes it will work just fine. The kit has multiple main jets to choose from too. If you like you can PM me if you get the kit and I can try to help you through the process. It is not that hard to do. Just be confident and follow the instructions given and you should do just fine. PS you have probably messed up the way it runs by adjusting the idle out of balance with the fuel screw. That is a diff topic to tune it finer once jetting has been done. We will help you out! :)

Edited by Jim BurnCycle Abbott

Hell yeah! Thanks all!

Jim, I'll PM you if I have any questions!

Was the bike sitting for quite some time before you bought it? The hard start and not wanting to idle are signs of a plugged pilot jet. Does it idle better after it warms up with the choke out?

Was the bike sitting for quite some time before you bought it? The hard start and not wanting to idle are signs of a plugged pilot jet. Does it idle better after it warms up with the choke out?

 

I'm not sure if it was sitting. Even after it's warm it was stalling, but I think that also had to do with the petcock having an alarmingly fast leak.

 

This damn bike is going to be brand new by the time I'm done with it. I guess you never really own a bike until you're able to take it completely apart!

Okay, I'm embarassed asking this but can't find a straight answer anywhere on the web, but I've read that Automotive Carb cleaner is bad for MC Carbs, so does anyone have a recommendation for what I should use?

 

Apart from basic tools and the carb cleaner, are there any other products I should consider for "float height measurement", lubrication, cleaning, etc?

 

Thanks!

 

Edit: I just grabbed the PJ1 Pro-Enviro Carb Cleaner from the TT store along with the TT Extended Fuel Screw and the JDS005 Jet Kit. Woop!

Edited by pavanjared

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