Hi guys and gals. I'm new to the forums, hoping you can help me out.

I'm having hella problems with my 2001 Scrambler 400 2x4. The only mod done to the bike is oil injection bypass. The single pull throttle cable is in the mail and will be installed shortly, as this will eliminate some of my symptoms (as described below). Let me give you the history on the whole deal.

First, I buy the bike for more than what it's worth without checking the counterbalance oil. Of course, I am so excited about this new bike that I go and ride it for a couple of hours before finding out that there IS NO counterbalance oil in it. Why? Because the water pump leaks, and if there was oil in it then the water wouldn't disappear. What a clever selling approach. Stay away from craigslist.

Regardless of my stupidity, I find someone local to fix it. This guy knows these 400L engines front to back. So we pull the engine. He replaces the bearings and all seals and gaskets. I also have him rebuild the top end with wiseco piston because the stock pistons on these are known to shatter and go through the case. No sweat, I'm building a machine that I hope to be riding for years to come. With exception to being water-cooled, this machine does not get any more bulletproof.

Ok, back on topic. I get the machine back. Take it to Mena for a day and a half ride. Runs excellent. A month later go to a little motocross track close to me just to fart around. No problems. Note that it is dry in mena. Some water crossings, but we're not wading rivers or mudding - this is important later in my story.

Over Christmas, I'm idling it in the garage to do some preventive maintenance (change the oil), and notice the water pump is leaking. I'm a little pissed, but call the guy and he says no sweat, he'll do all the labor, seals, bearings for the counterbalance, but I will have to buy a counterbalance from him for 150$. Not a big deal; the way I see it I was going to have to buy one anyway, so his error in judgment only costs me gas to get my ATV to his place.

I get the machine back, and wasn't planning on going riding for a couple months. Somehow I got all excited and me and some guys from work went out to Bonham, which is within an hour of my place. I wasn't planning on getting muddy, but it got the better of me and I went after it. Nothing too deep, everything below the frame. I was in the mud for an hr. Got stuck a couple of times, but all the mud was below the frame. About 2 hrs into the ride, I get 30 feet out of a mudhole and the machine acts like its running out of gas. It couldn't be out of gas, but I turn it on reserve and try cranking it again. It's hard to start. I mean it takes forever to start up...I'm flipping the choke over and back again. This thing cranks right up usually. Always has, even before I had it rebuilt. I finally get it started and make it over to the place where I can wash it off. I barely get there. If I recall correctly, I had to ride at like 1/8th throttle and with the choke on. I wash it off, and can't get it started again. We pull it back to the truck.

Get it home. Won't start. I pull all the plugs on the bottom....Starter drain, crankcase drain, recoil drain...I think that's about it. My recollection is that the starter had some liquid in it. IT was black, but I think it was water 4 drops or so? (Btw, I had drained all these plugs when I first got the machine and the starter did not have anything in it. The recoil had a drop and the crankcase a couple drops.) Back to the story... Recoil had a little in it (I'm thinking a drop or two). And I think the crankcase had a drop...probably premix from there though.

Next day I fool around with it, and it starts right up. Anyway, I ride it around the place a little bit, its running fine. I guess wishful thinking made me think it was all better now. My guess was that something had become stuck in the main jet and had somehow settled back down into the bottom of the carb and was no longer an issue. This was logical because my recollection is that the main jet supplies fuel for ¼ to ¾ throttle. One of those jets does anyway...

Ok so 2 weeks later we head to Mena. Mena is a pretty good haul at 8hrs round trip, especially for a day trip. Anyway we get up there and it is raining *****. That was the forecast, we knew that going in but didn't care because we just wanted to ride. We get out and are riding for about an hour and 15 mins and its running great. It's also pouring rain. So an hour and 15 mins in, the scrambler starts doing it again. Just wants to die. Somehow I am able to make it back to camp on 1/8throttle and the choke on.

Get it back, it's stopped raining now, so I pull off the airbox. The inside of the carb looks to be coated in white lithium grease. This is obviously oil from the air filter mixed with the very moist air. No sweat, we're pulling the carb off and going to clean it completely. Begin disassembly. (remember my initial philosophy that there was something stuck in the main jet?) It appears really clean - including float bowl and main jet - with exception to the oil/water mix that is in the main bore. (It should be, I rebuilt it 3 rides ago). I clean it with starting fluid (all we had), which works very well at dissolving grease btw. Reassemble. Starts up no problem. I think that I must have cleared out the small piece of dirt that had made it through my brand new air filter and brand new fuel filter.

Cool. I take it around the atv park there and it tried to die once, but came back alive no problem. So it starts raining again and we head off. Also a note is that my throttle has started sticking a little bit (just starting here in mena on this ride). We get 4 miles out and this crap starts again. This time it backfires several times, I think due to the fact that the throttle is on a little bit (cable sticking) and I am also on the brakes. When it dies this time, we can't keep it running. I cannot resurrect it. We tow it back to camp. To hell with it, let's call it a day.

So we bring it home. I think later that night I am playing with it some more, trying to get it started. I get it running a little and it backfires. I do it again and it backfires before it can start again. This time it is a very bad backfire (the kind that rings your ears for 30 mins) and the exhaust separates where it is held together with springs. The reason I know this is because I get it running again and it is so loud I can't hear myself think. So I fix the exhaust so it is right and have let it sit there all week.

Since then I have dedicated free time to researching a little on the internet (and the shop manual for the bike).

One thing I need to know is how do I adjust the choke on it? I started farting around with it and now I know it has to be out of adjustment. The shop manual mistakenly tells me how to adjust a pull-out push-in choke. The style of mine is the small lever that flips out. The adjustment is done on the carburetor as well. Does someone have a service manual scan they could send me on that procedure?

From my research, both online and in service manual, I believe the problem to be electrical. Reasoning is that it runs for a little while then all of a sudden won't work anymore. My dad had a mower that did this and the problem was a bad coil. 40 bucks and we're done.

I have a couple speculations; please help me reason them out.

1. There is something wrong with the ignition system. The coil is bad or stator is bad. I ride it for so long and it no longer wants to function. (possibly heats up after a lot of use...etc).
2. There is a moisture problem. Somehow water is getting in the stator area (perhaps through the starter??) and after a while (a very long while, mind you), this interferes with the ignition sequence.
3. When the guy assembled the bike the second time, maybe the timing became off. Maybe the gears were put on the counterbalance incorrectly (or slipped after install), maybe the stator is not lined up like it was when it came off. (I marked the housing and stator when I took it apart the first time). This doesn't explain why it would run fine for a while though and then a couple hours later start having problems. The book says when checking the timing to not let the engine warm up because it retards the timing 2 degrees. It should be pretty warmed up in 10 minutes, I'd think.

So, guys, anybody have any ideas? I'm leaning with number two. Reasoning is that if the coil was bad, I would think it would die sooner...like in 10 minutes. But how would I test that?

While I'm throwing stuff out there, is it a coincidence that this starts happening after I get it back from the guy the 2nd time, or is it that it just so happens that when I get it back the 2nd time, I am running in very moist environments both times???

Before I even touch it, I am going to adjust the choke and install the single pull throttle cable.

I was also thinking about replacing the float needle and o-ring in the carb. (I've read that backfiring can be related to both ignition timing being off and/or too much gas in the chamber).

If you made it this far, thanks for reading. Your time is very appreciated.

Dillon

 

DOESN'T TAKE A GENUIS TO FIGURE OUT THAT 2 STROKES AREN'T MADE FOR LONG HAULS, THEY ARE MADE FOR SHORT RACING, ETC. 2 STROKES ARE A THING OF THE PAST. SELL IT AND GET SOMETHING DEPENDABLE INSTEAD OF A POLARIS. NOT TRYING TO BASH BUT WITH THAT COMBINATION IT CANT BE GOOD.

 

<div class="FTQUOTE"><begin quote>Originally posted by: suzuki2009

DOESN'T TAKE A GENUIS TO FIGURE OUT THAT 2 STROKES AREN'T MADE FOR LONG HAULS, THEY ARE MADE FOR SHORT RACING, ETC. 2 STROKES ARE A THING OF THE PAST. .</end quote></div>


ok basher
my 2 stroke runs great all day and as far as two strokes not for long hauls better call evenrude about their e-tec outboards let them know your opinions on longevity or any fast snowmobile for that matter about short racing only

many polaris 2 stroke atv's run thousands of miles without any motor problems i've seen some with 7000 and heard of some with 10k plus i have personally run mine for hours on end never missed a beat in 3 years

 

Just telling personal opinion, never had a bit of luck with any 2-stroke they are constant maintenance, and my two best friends race motocross, and say same thing raced 85's and 125's and they both rode 2 strokes forever hated them bought a crf250r and they loved it, not one problem since.

 

Yur probs are far above my head. But great story, was like reading a book. Loved it. good luck in finding out the probs. Good smart guys on this site shld be able to bounce ideas off you. Again great story!!!!




O and to this!!!!!!!


<div class="FTQUOTE"><begin quote>Originally posted by: suzuki2009

DOESN'T TAKE A GENUIS TO FIGURE OUT THAT 2 STROKES AREN'T MADE FOR LONG HAULS, THEY ARE MADE FOR SHORT RACING, ETC. 2 STROKES ARE A THING OF THE PAST. SELL IT AND GET SOMETHING DEPENDABLE INSTEAD OF A POLARIS. NOT TRYING TO BASH BUT WITH THAT COMBINATION IT CANT BE GOOD.</end quote></div>

WHAT THE *&$% ARE YOU TALKING ABOUT LMAO!

Sorry cld not help it!

 

You never mentioned if you took the pilot jet out and cleaned it.Also is your exhaust tight and no leaks in the pipe.

 

<div class="FTQUOTE"><begin quote>Originally posted by: suzuki2009

DOESN'T TAKE A GENUIS TO FIGURE OUT THAT 2 STROKES AREN'T MADE FOR LONG HAULS, THEY ARE MADE FOR SHORT RACING, ETC. 2 STROKES ARE A THING OF THE PAST. SELL IT AND GET SOMETHING DEPENDABLE INSTEAD OF A POLARIS. NOT TRYING TO BASH BUT WITH THAT COMBINATION IT CANT BE GOOD.</end quote></div>



I just came off of a 150 mile trail loop with my 500 2 stroke sled. Never a problem with it and it has 7500 miles on it and still has 125lb compression in both cylinders.

I had a old rd 350 two stoke street bike and rode that 300 miles on the Highway in one day. 20,000 miles on that one before being sold. Motor never was touched.

 

<div class="FTQUOTE"><begin quote>You never mentioned if you took the pilot jet out and cleaned it.Also is your exhaust tight and no leaks in the pipe. </end quote></div>

Thanks for the response.

There are no leaks in the exhaust.

I am leaving town for a week, but upon my return I will pull the pilot jet and clean that out. (I will disassemble the whole carb again and clean it). Do you know what the stock pilot jet number is? (All the stock jet numbers if anyone knows them) That will allow me to verify the correct jet is in place. I have noticed that I have to tension the throttle cable a little to get the bike to idle. (That is, I have screwed in the idle adjust screw all the way, but it alone is not enough for the bike to idle).

I currently have the jet needle in the third groove. I neglected to mention in the original post that--when I had the engine rebuilt--the jet needle was in the second position (whatever the next leaner position is) and the air screw was out 3.25. When I reassembled the carb, I put the airscrew at 1.5 turns out and the jet needle at the third groove. I also replaced the NGK BR7ES with the stock BR8ES. The guy I had working on it said these were the stock settings.

The reason I ask for the jet numbers is the guy that sold be this bike obviously had it jetted to run with a leaking water pump (ie hotter plug and jetted leaner).

Also, is there a way to change my password to the forums? I can't remember the one they gave me.

Thanks again guys.

Dillon

 

If this helps anyone, the problem ended up being that I didn't replace the double pull throttle + oil injection cable when I bypassed the oil injection pump. I put on the single pull throttle cable and haven't had any problems since.

Ended up selling the scrambler because I fixed the water pump 3 times in a year. Now I have a 2006 trailblazer 250 with HPD exhaust, green spring, and 11/42 sprocket kit.