2004 Zuke LT-R250 Carb issues

[dag1911]

Hey all! I am new on here and searched around to see if I could find a solution to my issue. There were a few threads that beat around the bush but I didn't find one that nailed my problem. So here it is (hopefully not again)!

I bought a little 250 for my wife and we took it out right after that and it ran great. Came back to the shop, parked it for about a week or two with a few starts in between, and then went out over the weekend and it started cutting out and backfiring into the carb. It seems like the choke was sticking cause it was "loading up" and you'd have to give it a bunch of gas to get it running again. It won't idle while in gear, or in neutral for that matter. It runs for a few seconds and then will backfire and die. There was a bit of smoke that would come out the top of the carb as well. When I'd have it running and in any gear, I'd take it up to about 3-4000 rpms and you could hear it cutting out a bit. No pattern to it, just random cutting out. However, when going through the gears at full throttle it ran fine.

I have went through the carb and cleaned up everything as best as possible. There were some o-rings that could have been replaced but didn't have any. I put it back together without the new ones but they are on order. There was one thing of curious note...on the diaphragm on the top of the carb, there is/should be a brass cylinder on the outside of the diaphragm. It is now missing. Will that make the difference? I always thought it was for idle purposes. I know its supposed to be there cause I have saw them plenty on my R6 carbs. (nearly robbed one out of my spare set of carbs)

Overall, I'd like some input on why this is happening and what I can do to fix it. Are there any rebuild kits out there worth a crap? Let me know...and sorry for being so long winded!

Edited September 26, 2013 by dag1911

[dag1911]

No help? Anyone? Beuhler....Beuhler...Beuhler???

[marioweldinginc]

I am not a carb guy (hate em) but will try and help. Cant vouch for anyone else here but I am a welder and work 70+ hours a week. Im quite tired when I get home. Most of the time I just dont feel like typing. Alot of carb problems are already posted with answers (not always on here but other forums) and not saying yours os a common problem but with some research the answers are out there.

So lets start from the beginning

Any mods done to the quad? Did you verify that the jets were correct and the needle was in the correct position? If you dont already I would check the shop manual thread and d/l one. If this is a stock bike I would make sure the carb was put back to factory spec. Yes you need the brass piece on the diaphram and I would wait till those o rings are replaced. Are you 100 percent sure its a carb problem and not an ignition/carb issue when you hit the 3-4k area. I would def wait till you have the carb back together with all new gaskets, orings etc. before you keep trying to diagnose this peoblem and drive you batty

Good night

[dag1911]

Nope, no mods made to the wheeler. Its bone stock. The jets are all stock and correct as it ran perfect the week prior to my issue coming a long. The needle only has one position, so its correct. I have since rebuilt the carb with a Shindy carb rebuild kit....everything was replaced correctly. The entire carb is clean as I left it in some solvent for a couple days. The reason I think its fuel is because its not a constant like it might be with electrical. The rectifier is in good shape, its got a new plug, the battery is newer, the grounds are solid.

As I understand it, from other forums like you suggested, the problem could be getting fuel through the petcock because of the diaphragm or gasket in there gets fouled up. Also as I understand it they work off of vacuum in turn causing funny problems. So the solution I am going to try is putting on a Raptor 660 petcock (perfect fit) and blocking off the vacuum port on the carb. Apparently it fixes everyone's ailments. Thanks for your input welder.

[oxidized_black]

when the carb is back together with the same results, do you think it might be the coil breaking down when it gets warm/hot ?

[dag1911]

I had a petcock off of an old WR that I had and slapped that in there...it helped but didnt cure it. It would idle for the most part but there would be random times that it would miss, almost like someone gasping for air, and then pick back up and run fine. At the higher RPMs it was still spitting and sputtering. So yes Oxidized I think that the rectifier may have an issue. I placed an order for a "guaranteed to work" used model off of eBay. Guess we will see if that is my issue. If not, any other ideas?

[marioweldinginc]

Not sure if this is remotely related to your problem but a friend of mine has a honda 250r and his midrange running problem was cured by a dial-a-jet. His is also modded with a big bore kit so it might be that his carb was not jetted correctly to begin with.

[dag1911]

Well I put in a new petcock and that seemed to cure my idle issues. It purrs like a kitten again.

I have since got a new/used rectifier from a guy "guaranteeing" it to work. After I put it on, I have the same results as before. It will run up to half throttle and then it seems as if it hits a throttle limiter. It will rev up and then back down, just cycles through it if you hold the throttle wide open. There will be a bit of a backfire in there as well. Do you guys have any ideas of what to try next?

Carb is rebuilt, air cleaner is new/clean, rectifier should be good, new petcock without vacuum and capped off on the carb. Whats next?!