My XR400 Rebuild

So this is the third time that I tried to post this and so we'll see if it actually posts! I bought a 2000 XR400 in December and have been rebuilding it since then. I initially tore it down to the bare frame and then just started cleaning or replacing parts as necessary.

I thnk its the pictures that have been causing problems so i'll try those again later.

I didn't run into many major problems except for the typical swingarm bolt problem. I ended up cutting the bolt off and replacing the swingarm with an extra one I received with the bike. I took the engine into a machine shop to have the remainder of the bolt drilled out properly.

I broke the engine apart just enough to replace the cam chain and then put the original piston and rings back in. I figure I could tear it apart later if need be.

The carburetor seemed to be in decent shape but i decided since I had it out I would get an overhaul kit and replace the seals etc.

I was finally able to get it all back together and after running it down the street a few times I got it to roar to life.

Now I've got to get it running smoothly and properly and thats where I need some help. I've never tuned in a bike before so I don't really know a lot about it.

1. I put a UNI air filter in and so I think that I need to rejet the carb. It runs well enough at low RPMs but when I open it up going down the road (even when done slowly) it starts coughing and kind of sputtering.

2. It smokes like HELL!! Sometimes its not too bad but when I really start revving the engine I get a nice large white cloud forming behind me. I did not do any work to the cylinder or valves as they looked ok. I was unable to measure the cylinder because i do not have the tools for that. I am guessing that some new rings would be in order.

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On the way home

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Ready to begin



Changing the cam chain


Frame cleaned, painted and reassembly started

I have a bunch more pictures but most were simply for my reference when I put it back together.

2013-01-26 15.12.14.jpg

Had to leave it here for a while because work was taking up too much of my time

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When it first started to run!

2013-04-19 14.34.10.jpg

Just missing the trim pieces and various guards.

When talking about jetting, you always need to give your elevation. When you had the carb apart for cleaning and the new seal kit, did you take note of the jet sizes? Did you check/set the float level? Needle clip position? You need to find out all of that.

You should check the valve clearances.

I too think it probably needs new rings, at the very least. If just blows smoke for a few minutes after starting, it's most likely the valve stem seals/guides. If all the time, rings or more. Pay attention to your oil level, don't let it get too low.

The exhaust looks stock. Look inside the exhaust exit, between the silver trim ring and outlet pipe. Do you see and holes? If so, it has had the Gordon mod done to it.

Is the underseat snorkle for the airbox installed?

Once you do all this and figure all this out, then we can talk jetting.

Thanks for the help Trailryder. I'm tired for tonight but I'll try to post those details in the next day or two.

Did it smoke before disassembly?

Is the oil over-filled? There is a special procedure for these dry sump bikes.

Did you orient the rings exactly as they were before disassembly?

If you replace the rings, you must hone the cylinder.

TrailRyder, here is the information you asked for. DFW area seems to be around 500-1000 feet elevation and the local riding probably no more than 3000 feet. I believe the installed jets are 142/52. The float level was checked and was within spec. I cannot remember the needle clip position but it matched the replacement one which was in the center position (3rd from end)

I adjusted the valve clearances before running the bike and they all seemed a bit tight (even after rotating the engine 180 degrees) so there were adjusted within the limits specified in the manual.

The snorkel has not been removed but the previous owner drilled holes in the airbox cover. The exhaust doesn't have any of the Gordon mod holes drilled in it.

I would like to buy your untouched-unmodified silencer if you decide to get one of those sexy pretty ones.

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