ADVrider (
-   Thumpers (
-   -   1998 xr400 build (

booger1 01-08-2011 04:59 PM

1998 xr400 build
Yearlier this year I was in Baja, A trip I've been wanting to do since I was was 10 yrs old after hearing and seeing pictures of the Baja 1000. I'm now 37 and was getting the chance to go.
Long story short, The bike was running awsome, a little smoke on start up but goes away, typical of the old xr's (old valve guides).
But really it ran awsome, usually 1 or 2 kicks to start in the mornings and even after crashing.
Well 4 days in to the trip,

That's the bearing for the counter balance shaft.
Some extra carnage.

I know this doesn't typicaly happen on xr's, but to it's defense, I've had her for about 8yrs now and numerous topends in various configerations from bone stock to 440 power, This thing would top out at 98mph (per my GPS).
Luckily I got back, thanks to my girlfriend coming down to get me.
And I wanted to do something differant with the bike than most ppl would do, make it electric start.
I was already planning on this for awhile now.
Found an ex400 bottem end on craigslist for $100 and a wiring harness for also $100 a few yrs back, so all is sitting in my little garage when I got back.
Someone had said that the motor was not a direct fit. This would be a show stopper, so I cleaned up the engine cases and put it in.
It's close, but the bottem front mount does appear to be off, but the counter sprocket shaft looks good to continue.
Now I also wanted to do something else with this thing:evil, because I can, Give it a kick start as well. Know I'll have 3 ways of starting this thing. 1 .electric, because I'm getting old and lazy, 2. kick if the battery dies and if that happens 3. push start.
I ended up talking to another ADV inmate (forgot his name, sorry) one day, because he had done this and said he hard a hard time getting the E-start reliable, but once he did he said it was all worth the trouble.
So I'm on a mission now, I have the whole bottem end of the ex motor and various parts to the xr. I found be using the counter sprocket shaft from the xr (replaced 3yrs ago, should be good) and putting all the ex transmission gears on that shaft would allow me to put the kick start gear on.

This bushing will go on the xr shaft to allow the gear to go on, I suppose if you had the means you could have the ex shaft milled down, but I have the shaft, bushing, and gear.
And it goes on like this.
and will look like this once all is in place.

booger1 01-08-2011 05:26 PM

Building motors is fun for me, been doing it for many yrs and it just plane relaxs me. If it's not broke, I have to figure out away to fix it.
I was going to document prices for this whole build, but I didn't write anything down when starting to purchase this stuff, but I do remeber everything that went into it.
First was the weisco crank and rod. Pricey at about $300 but it's heavy duty and I don't want to take a chance on running old parts at this point.
I've heard great things about JE pistons and since I've always used wiesco I thought I'd give it try. I can't remember how much more it was but I do know it was more money than the wiesco's.
Just so you know, I went back to the stock 398cc's but raised the compression to 10.5-1.
I was suprised to see a spec sheet that came with the piston, showing measurments and weight. Already a plus, not that it makes much difference, looking at the piston it does appear to be better quality. But I'll find out after a year or so riding if it is better.
I had also heard about using a crf450 cam chain, they say it's cheaper, but I don't really care about that, I like the idea that it's stronger.

It's starting to take shape.
As I stated before about the vavle guides going bad.
All new kibble white stuff in here. The parts were around $200 to $250, but the sticker shock came out the machine shop installing them $350 :eek1.

But they look nice in there.
I had already ported the head awhile back.
D-shaping the exhaust ports.

Cleaned up the intake. This use to be nice and shiny but they used glassbead to clean them up.

mcma111 01-08-2011 06:39 PM

The engine work is looking good.

Since you have it this far apart how about getting the frame powder coated? Send the kickstand and any other parts you need spiffed up.

booger1 01-08-2011 07:56 PM

I did think about the powder coating thing, but it's a dirtbike, I'm only planning on painting where I welded.

RideFreak 01-09-2011 05:24 AM


Booger, thanks for the pics and writeup, I've been toying with the same idea, TRX bottom end swap w/ kick start. I heard the same thing, that it didn't fit. If all that's different is the fr mm that's not a show stopper for me at all. Did you get the EX stator also, the charging system should be a breeze w/ that. I see no issues with making the charging/starting system just as reliable as the EX, it's going to take a decent battery though, KTMs been doing it with the RFS models for years with a small battery. The XR4 airbox w/ the top removed looks like you could fit a KTM sized battery and solenoid suspended in there just like they do on the RFS models, should be an easy bracket fab. The PO cut the top out of my XR4's airbox and it's not been an issue in deep water nor NMs dusty desert conditions with a twin air filter. PM me if you end up making your own harness and need any info/ideas, I've built a few for some XRs that worked out pretty well and got some diagrams that may help you out.

booger1 01-09-2011 05:42 AM

Ridefreak, I'm getting to that stuff. As for the battery in the airbox, I decided that I would just build a box for the subframe like on the xr650l. I know alot of ppl put it in the airbox but, I kinda of want to make it look all stock, as if Honda built it that way.
I, like your self had been looking all over the internet for some kind of write up on doing this, I saw alot of pics and video's, but no discreption of how it was done.
I should also state that the ex engine is out of a 2000 model quad. I'm not sure if they all are built alike.
I now that there were some differances between the 98 xr and 99 xr. That counter sprocket shaft is the one differance I found out 3 yrs ago. The 99 shaft is 1mm thicker, I guess that's why mine had broke, but I was running close to 13-1 compresssion.
as this write up goes on I may look you up for help on the wiring, that's my weak spot, I jsut don't have enough experiance with that, Thanks in advance for your help that I may need.

booger1 01-09-2011 05:57 AM

Now that the motor is built, it's time to get the thing mounted. The top mount is way off and the bottem mount is close.

I cut the bottem brackets off and bolted them to the motor, this well locate them correctly on the frame when I weld them back on.

Tacked into place.

A little tip here for all of you that may want to do this. This tubing is very thin and easy to blow through. I aslo descovered that there was moisture in there. There are drain holes on the back of the frame, but still higher up. Something I may address later.

brucifer 01-09-2011 05:57 AM

Cool build, booger. I'm with ya on building engines. I find it very relaxing as well. Good luck on it.
I'l be :lurking.

booger1 01-09-2011 06:07 AM

As for the top mount, I started out with some shoebox card board to make a template. I did a rough cut and then placed it up where they needed to be, drilled the 3 holes and now I have a template.

The orginal mounts are made of 1/4 in aluminium. I happen to have some 3/16 in laying around. It's only 1/16 differant, but I don't see why it wont work. If it does break later I can make new ones.
I traced it out on the plate and took the plasma torch to it (I love that tool).

Cleaned up and installed.

I may drill a hole in the center of the mounts like the factory ones had, but I'm not sure of the purpose of that, so I'll leave it alone for now.

booger1 01-09-2011 06:52 AM

With the motor in I tried to put in time. I had gotten a flywheel (ex400) off of ebay, I didn't inspect it real well when I got it. I couldn't find the timing marks. Pulled the cover off and sure enough no timing marks. It appears someone had takin alot of weight off of this thing as well as the timing marks. At first I thought cool, but then I thought if I run into trouble in the desert this well make it difficult to get right, and thenthe thought of is it still balanced. Don't want to take a chance here. Another $75 down the drain. I may try it later, but it's important to me to be able to work on it when I'm out.

I had also read that there would be clearance issues if using a TM36 pumper carb. This had me concerned, how would I make this work. I love this carb and not being able to use it is out of the question.
I got lucky.

I have little room to spare. I feel this carb was the single greatest investment on this bike. Thank god there's room.

Onward to the next step, see if she'll start.
3 kicks and she came to life, idles great bogs down when giving it throttle. I just happen to have a couple of sets of jets, And it appears I guessed right the first time.
I bet your all wondering why I would build a e-start bike and then kick it to start it.

well electrical is not my thing, all this wiring and color codes and I still need a battery.
After weeks of looking for a battery I decided on a drycell from odyssey. $140 I figured this would be the most durable and give me plenty of power to crank it over as long as I needed or run heated gear.
When the battery gets here, hopefully this week I'll build a box for it.
So back to the wiring, I had to lengthen some to be able to reach the handle bars so a splice here and a splice there, they now reach.

I found these electrical connectors at fry's electronics for pretty cheap. I know I should use water proof ones, but there expensive and I don't have a whole lot of experance with this stuff, so in the mean time these will work and maybe I'll back some silicon in the back side. I most likely will take these out later to put the proper ones in once I have everything done and have worked out all the bugs.

So now I'm waiting for the battery and a few electrical parts to come in, I'm trying to figure out where some of these wires go. It would have been easier to put the ex400 starter switch on, but it's a dirtbike and wouldn't look right having that big switch gear on the left handlebar.
So I have a run start switch off of a 650l mounted on the right handlebar and got a light switch for the left side.
While having the bike run I'm test to see which wires have power and where the others will go.
POW (Like in the batman movies), what was that.

Not sure if I had hooked this up wrong or if it arced out on the frame, I need a book. That was another $26 (from ebay) that I really didn't want to spend.
So in my quest to find a book the other day and not having any luck other than ordering online and waiting a week or so. I walked into cycle gear, they didn't have one but the nice guy (Eric) who I've gotten to know over my many yrs of shopping there said he has a factory manual he'll let me borrow as long as I need it, cool guy. He'll probably find a 20 in the pages when I return it.
So now I'm all caught up this report, it will be slow going at this point. It has taken me 2 and half months to get here.
I well most likely take any advise on electrical at this point, the book should help. I'm also still waiting on a battery and a new starter seliniod to come in.

RideFreak 01-09-2011 06:58 AM


Originally Posted by booger1 (Post 14892026)

Cleaned up and installed.

I may drill a hole in the center of the mounts like the factory ones had, but I'm not sure of the purpose of that, so I'll leave it alone for now.

It's a weight thing, the plate is very strong even with a hole in the center and that's a low stress mount.

Nice job!

Re: battery mount location - I'm running one of those alum tool holders under the LH side cover so I'll have to locate the battery somewhere else, there's plenty of room there though.

Get a copy of the EX's wiring diagram, it's going to be the most help when putting the electric start in order. I use the OEM handlebar switches, they carry more current (bigger wires) than the DS switches I've seen, used one's are cheap too.

Tukata 01-09-2011 07:46 AM

Next time find a few electric model guys for the battery. On my 01 I ran a 2200ma cell battery pack.
Fit is the bottom of the air box, had more power, and just took time and skill to solder up and seal. Oh yea, I was in under $30

booger1 01-16-2011 05:56 AM

Another productive week.
Found this on CL for $35, That should help out with night riding.

Also, the battery came in, and started building the battery box.
Using 18 guage sheet metal. A found a sheet of this at a metal yard in ther scrap bin for $3. It was roughly 20 x 20 in.

I do plan on making it out of aluminium later. I just got a tig welder and need to replace the water lines and get a bottle of argon. But for now this will work. It came out a little tight, so I drilled a hole in the back to help in removing the battery later.

I want to mount it on the left hand side under the number plate. Drilled some holes in the sub frame to allow the 1/2 in tube to go through.

Welded in place.

all welded up, both sides, then took a grinder to flatten the surface.

Made the mounting brackets and welded those on to the box. I used some 1/4 by 1in flat stock to make the hooks for the battery strap. Not sure where I got the strap from, but it's been floating around in the garage for a few years. I couldn't believe I Knew where it was.

Front view.

booger1 01-16-2011 11:01 AM

Next is mounting the starter relay, ( so that it won't short out on the frame again). Some more of that sheet metal and grinding, bending and welding it to the frame.

Now to run the cables. I found these at a audio supply store, I got 10 ft of this 8 guage cable for $11. They only had red, so I used electrical tape to make it black for the ground. I know this wasn't neccesary, but for ease in the future I thought it would be a good idea.

I placed the regulator/rectifier near the intake on the air box becuase it would fit there. I may change the location in the future if it causes a problem. I wanted to mount it to the battery box, but it already takes up alot of room and I don't want the tire hitting it.
All the cables are now zip tied to the frame and all fits under the seat.

booger1 01-16-2011 11:34 AM

Made a key switch holder using that same scrap metal. I would like to make a aluminium box that well mount to the headlight assembly later. I'm trying to get the bike put together for a ride coming up in 2 weeks. I'm not to happy with the wiring. I fought with the engine run/off switch for 4 hours and still can't seem to get it to shut off with that switch. But it does shut off with the key. So after 4 hours of messing with that I went forward with the lighting and horn.
It's amazing how bright the tail light is from the stock xr stator to the 400ex 140 watt stator.
The brake light only seems to be working when you turn the lights on, I would like to wire it up differantly so that the brake light works on it's own with out lights having to be on.
I used the magic button got a high pitch squeel and then the starter motor spins, no fire. a few more attempts and the thing came to life with the majic button. Fired it up a few more times as the wiring took progress and the starter gremlin went away.

Put the chain on and wheeled it out to the street, pushed that little button and, High pitch squeel and starter motor spins freely. I went ahead and ordered a new starter clutch assembly ($134).
That's okay, I've got kick start too, 1 kick and went for a ride around the block.
Bike seems to hesitate a bit when she got warmed up, I figure I'll try jetting it in the morning. It's been a long day, I've been working on it all day and my girlfriend didn't complain at all (she was doing alot of house work). Thanks honey.

Next morning I go outside to finish up a few things. Exhaust bracket does not line up. The motor sits alittle more forward, which raises the exhaust pipe.

1/4" steel used to make the new bracket.

welded in, looks good, and works.

I figured I would start it up to let it warm up before tackeling the jetting issue and discovered I had left the choke on for last nights little ride. Bike seems to be running great, I''ll try to take it out this afternoon to see if all is good.
2 other thing I ran into in this project, with the motor sitting more forward the spark plug wrenchwouldn't fit. You could get the plug and wrench in and tighten it down but then I couldn't get the wrench back out. I ground off about 1/2 inch off the top of the socket to fix the problem.

Another thing, I should have looked into before ordering a gear shift lever. The xr's gear shift lever will not work. The stator cover comes out much further on the ex's. No problem tho, I have friend that may need this later.

The reason I decide to document this is that I've heard of ppl doing this conversion, but no one has documented it.
Also the xr is a very capable bike, and pretty much anyone who owned one in the past thought the only flaw in the bike other than it sits high was that it didn't have an e-start.
I well go back through my records and list everything that I used and the prices later.
Hopefully this well help others in doing somthing like this.
Good luck

Times are GMT -7.   It's 02:30 PM.

Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2015