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Hittin' A Wall

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Hey Y'all, first post, so please bear with me.

Bought a '03 XR400R in December '06. Bike was in perfect condition, looked like very few hours. December in Idaho and iced up roads, so I didn't get to run it much before I bought it. My brother lives around the corner from the Honda shop so I just rode it over there and parked it. I want to ride it on the road, so the first thing I did was put a Baja Designs dual sport kit on it and a Trail Tech Vapor computer. So far, I love the bike.

Now the problem. At random times, I will rev the engine to 5000 RPM and it will hit a wall. If you try to roll the throttle more, it boggs even more.

The situation comes up in neutral or any gear. Will run fine through 1st and 2nd and it will hit in 3rd. Pull the cluch and rev it a few times till it clears 5000 and your off and runnin' again. Sometimes will cycle through the gears without a glitch. Sometimes it will hit while down shifting.

I have:

1) Run a couple of tanks of gas though it.

2) Cleaned the carburator. Looked great inside, no gunk, dirt, or water.

3) Checked the valves.

4) Spark plug looked like she is runnin' a bit rich.

5) Loosened the decompression cable, just in case it was openning on its own.

Okay. That's the lowdown. When I cycle through the gears, the bike feels great. Then it starts yakin' on a bone again. Drivin' me crazy. :applause:

So ....... any suggestions?????????

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PT,

Maybe your carb is running dry before you get to top speed. Either floats needs to be adjusted or the little fuel line that feeds the carb is pinching somehow. Once you stop and cycle the revs a little, carb refills and you are good for a few more gears worth. I would start checking on fuel delivery.

CHeers

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D1k,

Thanks for the input. Floats looked good when I had the carb apart and the fuel line is in good shape.

Its just weird. It seems totally random when it hits, but it always hits at 5000 RPM. Sometimes it will yak in all five gears in one shifting cycle, sometimes it will alternate gears, sometime it will be fine.

I've tried to ease through it. I've tried to rip through it. Once it is yakin', I can back off and it will run fine at lower RPM, but it will not rev through 5000 RPM. Pull the clutch and rev till it goes through or try another gear.

Crazy!?!

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I assume you are guessing at the rpm as a 400 has no tach. If it quits the same rpm in any gear at the same relative speed, it may be ignition related. Also check the obvious like the fuel tank strainer for blockage. You say your plug reads rich? Have you removed the spark plug cap resistor and replaced it with a piece of stainless steel screw?

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I want to ride it on the road, so the first thing I did was put a Baja Designs dual sport kit on it and a Trail Tech Vapor computer.

Thats my guess on how he knows it is quitting out at 5,000. Assuming it is hooked up properly and has the tach set up.

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My 250 was doing pretty much the same thing when i took it out of the shed a couple weeks ago. Thought i had to tear apart and clean the carb but it was still cold out so i just added some stabil and some injector/carb cleaner to the tank and drained the carb. Next time i took it out it ran like a champ and had more power than it ever had since i bought it last february. Carbs are picky things -- they look clean but might not be. it cant hurt to try it.

-john

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I've been thinking about what everyone has said.

I've used some STP Gas Treatment 2 of the tanks of gas, but did not try injector/carb cleaner. At this point, my plan is to:

1) Ride the last of the fuel in the current tank.

2) Pull the petcock and check it and the the screen set out.

3) Check the electrical connections to the coil and such.

4) Put her back together, fill the tank, and try some injector/carb cleaner in the fuel.

5) Ride it like I stole it!

Thanks for the suggestions!

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Sorry, I missed the Trail Tech tach, Zappa. Sometimes these things can cause wierd ignition problems.

disconnect this trail tech tach and see if the problems goes away

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disconnect this trail tech tach and see if the problems goes away

As far as I know, the tach just connects to the side of the engine and measure vibrations, nothing goes inside of the engine. It's a completely exterior device and just mounts on the bike and doesn't affect anything on the workings of the bike.

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For the tach portion of the computer, you wrap 1 lead of a wire around the spark plug wire and the other lead goes to ground.

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Update on my problem.

I ran a tank of good gas with carb/injector cleaner through the beast. Still no good.

I pulled the petcock out this afternoon. Is the screen set supposed to be deformed at all? Mine is in three segments; 1) screen closest to the valve was a bit deformed (limp noodle), 2) then there was a rigid part, 3) then more screen, but more cylindrical and straight. Could that be contributing to my problem?

Also, something on another post caught my eye. That was a discussion of the rev limiter in the CDI box. Thinking about my circumstances, when my bike is having one of it's episodes, it sounds exactly like it is up against a rev limiter. Could my CDI box be going schizo????

Any thoughts?

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I would check the tang on the carb float again. I have a cb450 that would run great until I actually tried to ride it at higher RPM's.High RPM's in the driveway were alright but it would sputter and cut out when riding. The problem went away when I bent the tang on the float to allow more gas in the bowl.

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When you say the float "looked" good, did you actually measure float drop?

Minimum drop should be 14.5mm and max 19mm.

Make sure the fuel tank cap is venting properly too. It the tank can't vent, you'll draw a vacuum on it. The carb can't draw fuel from the tank if there's a vacuum in the tank.

If you're hitting the rev limiter of the CDI, it's "supposed" to make the engine cut out like that.

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I did not actually measure the float drop. I appeared to be working freely.

On the rev limiter - when the problem hits, it is at 5000 rpm (not 9000).

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Another thought. If carburation is my problem, what are the chances that implementing Gordon's Mods would clear it up?

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Another thought. If carburation is my problem, what are the chances that implementing Gordon's Mods would clear it up?

Hey PT, what if it is the exhaust is plugged up with shit in it?

My other guess would be to start with carburation(easier) then get or borrow someones elses CDI box and check the ignition. That could be the cause of the intermittent 5000rpm or so choke hold !!

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Implementing The Gordon Mods will make your jetting leaner for the new configuration. You don't normally correct carburetion issues with intake/exhaust mods. You do your mods then jet and tune the carb to run with your configuration.

I highly recommend the Gordon Mods tho.

Another thought. If carburation is my problem, what are the chances that implementing Gordon's Mods would clear it up?

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My guess would be electrical. Check all of your wires under the seat and make sure the connections are clean and tight. Next take off the coil and make sure the coil is grounded good. Also take off plug cap and make sure it is on the coil wire properly. Also unhook the black wire to the coil and make sure the connector is tight and clean.

My bike did something similar and it was the coil wire was loose in its connection.

Good luck crap like this just drives you crazy, I thought of my fix while lying in bed after working on it for about 4 hours and deciding not to go to a race because it was running so erratically, run good then all of the sudden wouldn't hardly start and then did similar things to what yours is doing.

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Make sure the fuel tank cap is venting properly too. It the tank can't vent, you'll draw a vacuum on it. The carb can't draw fuel from the tank if there's a vacuum in the tank.

Also, the carb can't draw fuel if there's positive pressure in the bowl - check your carb vent lines for dirt or kinks.

The only way to find out if it's your CDI is to run a known working CDI and see if the problem goes away.

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