250sx carburetor problems AGAIN! (still...)

[filthyhat]

Hello all! Let's get right to the neety greety...

So, like the title says, my 85 250sx is giving me what I think are carburetor problems, but I will let you the trike experts make up your own minds as to what is happening.

I was out riding the other night with some buddies, and trikey was running reasonably great. Plenty of power, running mostly like a champ as far as I can tell. So then at one point I hit the gas and the darned thing lost all its power and started running like tee total crappola. It sounds fine, no strange noises or anything, the engine just started taking forever to rev up.

I thought at first that maybe my brakes had started sticking again, but it even displays the same symptoms in neutral. I give it the beans, and it revs very slowly. I went ahead and rode it for a few more hours that night and brought it home. The problem did not correct itself.

So I finally unloaded it from the truck last night and rode it a little around the yard, same issue. The darned thing just won't rev very well at all. I honestly haven't even looked at it since. As a reasonably competent bike mechanic (under a shady tree), I will of course start with a carb cleaning and then maybe run the valves, but this was a sudden thing. It was like a switch got flipped and suddenly I'm running at less than half power. It still pulled me around, but top speed has gone to about twenty and it won't even pull fifth gear anymore.

Also, on a possibly related note, my trike STILL cuts out and dies when I give it full beans from idle. This too is a very annoying problem, as I have to really control my thumb to keep it from dying off the line. Once it gets a few rpms under its belt it can take full throttle no problem, but from an idle it just wants to die. If it was a direct slide carb maybe I could understand, but aren't these kelvin carbs? I see videos on ebay and read about people saying how their 250sx is a "wheelie monster", but I can't get mine to wheelie at all. I have never ridden another 250sx so I have no idea whether it has the power it should have or not.

The old gal has had this particular problem since I got her. I have cleaned the carb numerous times to no avail, and even went so far as to visit flyingw and pick up one of his rebuilt carbs. After slapping that bad boy on there, the trike didn't run much if any better. Truth be told I think it idled better with my old carb. Honestly I think the carb I had before must have been fine but I really wanted to throw another hundy at it lol. It's not that I think Jim did anything wrong with this carb or anything, I'm just starting to think that it might not be a carburetor related problem.


So yeah if anyone has any idea what might be causing either of these problems please let me know. The old gal is starting to give me more and more trouble, and if I can't get it going there's liable to be some 250sx parts for sale on ebay shortly.

Dylan

[Flyingw]

Dylan,

Is there a time where you can toss the SX in the truck and pop over top the city? If two carbs are doing the same thing, I tend to agree the problem is not with the carb but possibly ignition. I have parts here to troubleshoot with.

[Dirtcrasher]

Fuel flow?? Is this a metal tank?? If so, tear out the petcock filter and run the inline fuel filter.

The SX is a damn good running machine.

Take every jet out and spray carb cleaner and compressed air all through it. Then splice in the filter.

If the tank is rusty, coat it.

Filter is clean and connected?? Hope so.................

[filthyhat]

Lol I typed a big long response but it somehow didn't get posted, so here's the long and short of it.

Jim, I wish I could bring it out but the truck isn't up to that kind of road trip right now. Maybe soon. I'm sure you could figure out what's going on with it.

Dirtcrasher, thanks for the suggestions. The tank isn't rusty, but the filter could probably use changing with all the riding I've done.

I'm hoping to be able to tear into the trike tomorrow. Also I think the rear end bearings have gone out on me, as I recently replaced the rear wheel bearings but not the rear end bearings and it looks like water sat in there for some time before I got the trike.

Dylan

[Flyingw]

Ok, I'm here when you need me. For now, lets look at the ignition system components.

1. Do you have a meter?

2.Do you have a factory manual?

[filthyhat]

It's trike day! or a reasonable analog for such.

Jim, I do have a dvom, and I have what I think is the factory manual on my pc. I do not have a paper copy of the manual.
The manual I have did help with the wheel bearing replacement but doesn't seem to have a lot of info on troubleshooting.

The plan for today is to pop some pain pills so my neck wont hurt as bad and then tear into the old gal, and I'll probably start with the carb. I have a nagging suspicion that the main jet may have fallen out, as I read that is possible online and it seems plausible from the way the trike acted.

In my twisted mind it seems like I should first address the loss of power problem, then the rear end and finally get her out there so that we can troubleshoot the takeoff problem. I am a little excited, because if we can get more power and better takeoff from the beast that would be downright neat.

Even down on power like shes been I have found my sx to be a very capable machine offroad. I have some warped kenda bearclaws on the back and have never met a mudhole, or a hill that I can't tackle. Unless you count the times that I've flipped her over backwards...

And also Jim, I realize that I am very fortunate to live within driving distance of a veritable 250sx expert, and I will be hitting you up for your expertise. Thanks for all your help.

[filthyhat]

Well, I'm not sure, but I think I may have found the problem with the carburetor.

I'm not sure of the technical terms for these things, but the rattling I heard when I took the carb out was the two screws that hold the armature in the top of the carb to the slide. I found them just laying in the top of the carb, so when I gave it the gas the armature would be raised but the slide would not. Lol I think that may have something to do with why it hasn't been running that well.

And I was mistaken, these are definitely not kelvin carbs. I'm gonna clean it out real good and loctite those screws in there, then move on to the rear end. Gotta love an easy fix!

[Flyingw]

That wasn't the carb I sold you was it? If you haven't done so yet, don't locktite those screws, you'll never get em out again.

[Flyingw]

if your pinion bearings are bad, I have the special tools to completely disassemble the diff. The ring gear bearings are easy enough with no special tools required but the pinion bearings are a whole different story. Call if you need any telephone support. 405.420.1114

[filthyhat]

Dammit! I was afraid I maybe shouldn't loctite those screws, but there goes my inexperience again. It is the carb you sold me.

I started to leave them dry but then I talked myself into it. I figured if they came out so shortly after you rebuilt the thing then they must need something, and the only reason to take em out that I could think of is to change the needle clip. Theyre glued in place and the whole thing is running much better now. Hopefully I didn't fubar things too badly.

I got lazy and didn't tear into the rear end today, Every time I look at it I think of tearing it down and seeing if your offer to powder coat stuff still stands.. Things are starting to get rusty back there. From what I could tell, the only things to powder coat would be the swingarm and the lower plate on the triple tree. Unless you can do an engine casing?

I guess the thing to do would be just ask... What parts of the trike can you powder coat? And do you still do that?

[Flyingw]

Most certainly I can powder coat stuff and I won't kill you on price. I can also do engine cases. The only thing I cant do is the frame as I don't have an oven big enough. I'll have to double check if I can get a swingarm in to my oven but I'm pretty sure I can. I'm bugged at the fact that it was my carb those screws backed out on. Sorry about that. I'll be sure in the future to double check those before I close the carb up. Let me know what you want to do.

[filthyhat]

It's no worries Jim, you're a stand up guy and I'm sure you put them in there. I would say I've at least put a few hundred miles on there with that carb and had no problems until now.

I'm being all flippy floppy about rebuilding the rear end. I need to just start taking it apart and see what happens. If we were going to powder coat the engine, how far would I have to disassemble it for prep? Like do I have to take it down to bare engine cases? And forgive my ignorance, but would powder coating the engine affect the cooling at all?

Honestly I'm not trying to build any kind of show machine here, looks are secondary on my toys I'm just looking to prolong the longevity of my beloved trike. I'm also not looking to dump unbelievable amounts of money into her if I can keep from it.

[Flyingw]

To PC the engine, a complete teardown is required. The parts have to be baked at 380deg so bare engine cases are required and no, PC does not effect its cooling properties. Let me know what you find when you open up the diff. Pay particular attention to the pinion shaft and any slop in it. That's the real failure area.

[filthyhat]

OK so I got the diff off of there, and I'm trying to remove my swingarm but the lower shock mount bolt is like frozen solid.
I've been spraying it with pb every few minutes but I wonder if there is something I'm missing? Is there some kind of catch to removing the lower shock mount bolt? I got the nut off...

There was some crud build up everywhere inside the axle and diff that I have looked so far, but I haven't actually opened up the diff yet. It seems ok when I turn it with my fingers, I don't know if this is the source of that strange noise or not. I'm starting to think maybe the u-joint is bad, and I figure that while I've got it this far torn apart I'll replace the crusty and possibly leaking u-joint boot at the very least.

And my drum brake is definitely leaking, as there is a big chunk of the "brake panel" missing near the bottom. So I've got my trike totally torn apart and now I get to try to figure out just how bad this is going to get into my pocket.

So that's where I am now. Since I'm stuck on the swingarm, I figure I'll go ahead and rip into that diff and see what I see. I shouldn't fail to mention that when I went to remove the left axle nut, it somehow was only finger tight. I hope that wasn't the source of my strange noise lol...

[Flyingw]

What's happened is the lower shock bolt has corroded to the bushing in the shock. Not uncommon. I have a brass drift I set on the end of the bolt to loosen it and knock it out. Post up a pic of the propeller shaft (drive shaft) and lets see if it needs attention. Yes its a good time to replace the boot. If the diff is going to be opened up, its a good time to rebuild it. The kits are about 50.00. Well worth every penny for that. Is your SX 85 or 86? the rest is pretty straight forward. Your out of pocket costs shouldn't be very much. Perhaps a fresh set of brake shoes, swingarm boot, diff bearing kit, tube of silicone, and at very least, some spray paint.

[filthyhat]

Yeah I got the diff open, and the bearings inside seem borderline. Not screaming bad but not perfect and new either. So, I'm going to order that rebuild kit. I have seen a couple of different sellers on ebay, is there a specific brand of kit you would recommend? I don't want to have to do this again for a few years. The ring gear has obviously sat in water at some point, but it is not bad and I don't see why it wouldn't last for years to come.

I understand flyingw that you have the tools to replace the pinion bearings? I am leaning heavily towards bringing you the diff to replace the pinion bearings and powder coat basically everything but the frame and engine. It will be a couple of weeks before I have time and money but I figure I/we might as well do it right while I've got it all torn apart.

If you don't mind, what do you think you would charge me for said services of replacing the pinion bearings and then powder coating my swingarm/rear axle/diff, the rear fender supports, that front triple tree piece that looks painted, and the heat shield on my exhaust? And anything else painted that I can remove, aside from the engine and frame. I think I've pretty much named it all... Also can you powder coat my muffler/exhaust and is that something that should be done? I don't know how expensive a process this is but I'm sure you're not gonna gouge me.

Feel free to pm me or call if you still have my number, or if you just don't want to post this kind of information on the forum then let me know and I can give you a call later. It will be a few days at least before I can even order the bearings so there's no huge hurry. Thanks for all your help!

Dylan

[filthyhat]

Also, since the parts to be powder coated are going to be baked like that, can I assume that means the rear wheel bearings will need to be removed for the process? I have just replaced them with new ones that have the rubber seals and it seems like they would melt. If necessary I can even buy a new set, If I'm going all out like this I'm gonna try and seal it up as well as possible to prevent ever having to do this again.

Heck as far as I know the original bearings in there are going on thirty years old. I'd be happy if I can get half that out of the new ones!

[Flyingw]

No worries, the bearings and seals are easy enough to get out.

[filthyhat]

Hello again all! With flyingw's help I have finally gotten my old trikey back in action.

The new diff works a treat, and the strange noise that I was chasing is gone.

However, This problem is still giving me fits.

It's almost like the carb doesn't want to take gas. When I got the old gal back together, I turned on the gas and virtually nothing flowed into the filter. So I tried to start the beast and it wouldn't start. It acted like it didn't have any gas...

I pulled the fuel hose from the petcock and fuel flowed freely in both "on" and "reserve". But it doesn't seem to be getting to the carb fast enough, almost like the float needle isn't opening fully.

When I first put the carb back on after finding those loose screws, the floats were totally stuck somehow. I had to remove the fuel bowl and fiddle with it before I could get any gas to flow, and then it started running again.

Why would the floats stick like this? I'm thinking I may not have the carb back together right, but I can't imagine what I must have done wrong...

I'm supposed to go riding today with friends, and I was planning on taking the trike, along with my bike. It is rideable, but it is very frustrating anywhere near idle as it would much rather die than allow me to crack the throttle.

Any help would be greatly appreciated. I'm sure this would be a simple fix for some of you out there, but it's got this smoke-retarded old rider stumped. She runs great mid to full throttle, and has plenty of power everywhere except bottom end, which I understand is where the sx is supposed to shine...

[Flyingw]

Refresh my memory but did you try taking the gas cap off of the tank? If not, try starting it up with the cap off and see if the fuel problem still exists. Post back up the results of that test. I'm glad the diff worked out good.

[Flyingw]

Option B if the gas cap test has no effect is for me to send you a different carb and see if it performs the same as that one. I can do that when I return to OKC next week.

[Dirtcrasher]

Hello again all! With flyingw's help I have finally gotten my old trikey back in action.

The new diff works a treat, and the strange noise that I was chasing is gone.

However, This problem is still giving me fits.

It's almost like the carb doesn't want to take gas. When I got the old gal back together, I turned on the gas and virtually nothing flowed into the filter. So I tried to start the beast and it wouldn't start. It acted like it didn't have any gas...

I pulled the fuel hose from the petcock and fuel flowed freely in both "on" and "reserve". But it doesn't seem to be getting to the carb fast enough, almost like the float needle isn't opening fully.

When I first put the carb back on after finding those loose screws, the floats were totally stuck somehow. I had to remove the fuel bowl and fiddle with it before I could get any gas to flow, and then it started running again.

Why would the floats stick like this? I'm thinking I may not have the carb back together right, but I can't imagine what I must have done wrong...

I'm supposed to go riding today with friends, and I was planning on taking the trike, along with my bike. It is rideable, but it is very frustrating anywhere near idle as it would much rather die than allow me to crack the throttle.

Any help would be greatly appreciated. I'm sure this would be a simple fix for some of you out there, but it's got this smoke-retarded old rider stumped. She runs great mid to full throttle, and has plenty of power everywhere except bottom end, which I understand is where the sx is supposed to shine...

Pull that damn old tank filter system out! Remove petcock to get to it..........

Run a clear inline filter to your rebuilt carb.