Bike starts, idles, but dies on throttle...help with carb issue please.

[Kaneman]

The main issue is that I don't know what the fuck I'm doing and I can't find a good manual or tutorial for this carb. Its quite a bit different from the XR50 carb I rebuilt...which is my only other foray into the carb world. The is a pumper carb on a 1998 DR350 Offroad.

Bought this bike last week and have run a full tank of fresh gas through it, with seafoam. Went offroading on Sunday for a couple of hours and it ran great, starts first kick, etc. On the way home I'm cruising down the road and the bike loses power. I pull over, it dies, but fires right back up when I kick it. It will idle, but when you give it gas it dies. The motor will rev up high on full choke, but can not be revved with the throttle. On throttle it immediately bogs and dies.

Well, the bike has been sitting for a while before I bought, and I knew that. I was excited though and didn't bother to clean it or change the filter or anything before I rode it. The airfilter was fucked and the carb was filthy.


I took the carb apart as much as I felt comfortable with, cleaned it, blew it out...thought it was be cool....but still having the same problem. I've taken it apart and cleaned it twice now. The throttle itself moves more smoothly now that the carb is clean, but it still bogs and dies.

The first thing I need to know is can the carb be broken apart more than I have done so far? Since I see no way to adjust the needle I would say yes?


Second question, is the needle supposed to just drop down in here with nothing securing it? It just fell out when I broke the carb down, and that seems odd...


Ok, then there's this lil' guy. It seems like it should move up and down freely on the spring that it sits on, but when I break the carb down I find it compressed and stuck...I have to tap it a few times to get it to release so I can take it out. I've cleaned it completely inside there so I can't figure why its getting stuck..


I know I should take it to a mechanic and have him work it over, but if I'm gonna do the dirt thing I gotta learn to do this myself...and I don't know anyone to guide me through it. Thanks in advance for the help.

[6doublefive321]

I can't see the pics at work, but I will take a stab. Since the bike will run and rev on full choke, it sounds like you have a fuel starvation issue. With the choke on, the carb is in rich mode. Since you can rev the engine with the choke on but not with the choke off, you may not be getting enough fuel with the choke off. The root cause can be a number of things, but a clogged circuit or jet is probably the most likely suspect. Tear that bitch all the way down. It will go back together.

[Kaneman]

Originally Posted by 6doublefive321

I can't see the pics at work, but I will take a stab. Since the bike will run and rev on full choke, it sounds like you have a fuel starvation issue. With the choke on, the carb is in rich mode. Since you can rev the engine with the choke on but not with the choke off, you may not be getting enough fuel with the choke off. The root cause can be a number of things, but a clogged circuit or jet is probably the most likely suspect. Tear that bitch all the way down. It will go back together.

I can't rev the engine with the throttle on choke, I meant to say that the engine revs up when I put the choke on (as normal).

Looks like I need special tools to take the carb the rest of the way down. I'll go see what they have at autozone.

[Trip]

Could be the air screw, find out what is the typical turns out for your elevation and reset it.

[G-Rex]

That needle should have something to secure it to/with the diaphgragm.

I stole the below picture from the interwebs, but it illustrates generally what you should have, and the order they should be in. Think of the diaphragm as the bottom of this assembly. Everything else should drop in above it and then secure the cap on top of all that. If the needle just dropped, you are missing parts, or lost parts on disassembly.

The reason it won't run is that the needle is blocking the air/fuel flow. The reason it runs on the choke is because that part of the carb is a different circuit typically.

[Avatard]

The needle sits in the main jet. It should pop up with the slider (or with a turn of the butterfly, depending on design), admitting gas as the slider (or butterfly) admits air.

You're adding air without fuel, as the slider is rising, but leaving the needle stuck in the main jet like a cork. Find that E clip!

[Kaneman]

Well the needle was broken off at the 3rd ring on the top, which is why it was just loose in the carb. I called Kientech and talked to Jesse, he walked me through disassembly and told me what to be looking for. The interior of the carb wall was worn pretty badly by the slide, the slide itself needed to be replaced along with all gaskets, jets (badly corroded) and o-rings. I ended up just ordering a new pumper carb from Jesse and threw in a stainless header for the fun of it! I'll let you guys know how she runs.

[Particle Man]

Originally Posted by Kaneman

Well the needle was broken off at the 3rd ring on the top, which is why it was just loose in the carb. I called Kientech and talked to Jesse, he walked me through disassembly and told me what to be looking for. The interior of the carb wall was worn pretty badly by the slide, the slide itself needed to be replaced along with all gaskets, jets (badly corroded) and o-rings. I ended up just ordering a new pumper carb from Jesse and threw in a stainless header for the fun of it! I'll let you guys know how she runs.

When in doubt, just replace the whole fucking thing, eh?

I suppose that works too

[Kaneman]

Originally Posted by Particle Man

When in doubt, just replace the whole fucking thing, eh?

I suppose that works too

Nah, it was just to worn out to be reliable.

[Trip]

Originally Posted by Kaneman

Nah, it was just to worn out to be reliable.

With my experience with fiddy carbs, this definitely is the best route. I started out with a chinese carb that's a piece of shit, then to a KLX110 carb that doesn't fit right, then to a 1970s keihin off ebay, and finally just bought a new keihin that works.