The XR400 Thread

[farrington300]

I would start your jetting quest at 60 160, and go from there.

Originally Posted by birds

I have some questions about carb tuning

My carb is in dire need of gaskets, and I want to make sure the jets are right, as I had an overheating problem recently (maybe too lean?). I have no idea what is in there now. What jets should I start with while trying to tune it?

- '99
- uni air filter (bike came with k&N)
- no snorkel
- seems to be stock header with FMF Megamax muffler
- sea level

Any other information I need to find out?
Any things I need to order other than the gaskets and jets?

[HopheadRed]

Originally Posted by HopheadRed

So I've been having some starting issues (read as won't run!) with my 01 XR400r, figured this thread would be a good spot to post a few questions where maybe I could get some ideas...Here's some background.

Purchased an 01 XR400 with an Electrex Dakar dual sport kit installed. Always was a bit of a pain to start, but once it was warm, 1-2 kicks max. From day 1 this sucker leaked gas out of the overflow like crazy. I rode a few times with the bike in this condition. I travel a lot for work and was getting ready to leave for a few months in the middle of purchasing/moving to a new home- my buddy convinced me to leave the XR with him for the few months I was gone.

When I returned home and picked up the bike, the spark arrestor insert had come out while he was riding and the bike was running pretty rough. The bike sat outside a few weeks. He installed new throttle cables, a new ignition coil (ebay - thought it would solve starting issues) & cleaned it up before he gave it back to me. While settling into the new house, I didnt have much time to ride, so I didn't even touch the bike. After sitting for a few months, I decided to clean her up, give her some love, and make sure it was in good running shape. I removed the stock airbox snorkel, rejetted to 155/55, new tires, and replaced the muffler with a stock exhaust from a 1996 model. I could NOT get it to fire up - Removed the carb and cleaned out the bowl, fresh gas, fresh plug. Still no luck.

So wanting to ride and with time to work on the bike being an issue, I decided to drop the bike off to a local mechanic (recommended by some inmates here!). John, the mechanic, took a look at the bike and removed the head to discover a screw somehow lodged into the intake valve and was holding it slightly open. He removed the screw, examined the top of the piston for damage - set proper valve clearances, cleaned up the carb (no drain screw was the culprit for the leak!) He said overall, mechanically the bike was in good shape (no reason for it not to run) but even turning it over with a drill, he couldn't get it to fire and it had a weak spark. I had him remove the Electrex kit and revert to stock wiring - Still no progress. John diagnosed the CDI box as a possible culprit (unable to test w/out a peak voltage adapter - he nor local Honda had one).

After placing a phone call to the guys at XRs only, they told me the chances of CDI failure on this machine is slim to none. Likely culprit is the pickup coil. I purchased a HO Rickystator kit (had planned on getting one in the future) and had John install while the bike was in the shop. After install he told me the spark is MUCH crisper, def hotter, and now sparks 3-4x instead of the previous intermittent weak spark. Still unable to get the bike to fire -- He tells me he is still thinking it's the ignition control module. So I find a "working" CDI for an 01' on ebay and send it to John -- No progress, still won't fire.

This is pretty much where I stand right now - The other day I dropped off the stock ignition coil (that was on the bike when it was last running) and a simple push button killswitch (KS was integrated in DS lighting controls). I haven't heard any updates from him yet.

I apologize for the lengthy post, but I figured the background is necessary. I should also mention the bike currently has no headlight (dakar kit had headlight w/ integrated electronics), but I can't imagine this would affect ignition system. For such a simple, solid machine, this thing is blowing my mind. Anybody have any thoughts? Suggestions? Somebody has to have some insight...I'm at a total loss and can't really keep throwing money at this thing!

I'm out of town for work until the end of June, but I've left the bike at John's shop (Cyclecraft Motorcycles, NJ - recommended by folks here). He's got about 10hrs into it so far and we've replaced the following: brand new stator (ricky stator 200w), ignition coil (ebay - working), CDI box (ebay/existing same issue), and John told me today after speaking with some people, he replaced the crank rotor (magneto?) and still having the same issues. He also said he's got continuity on all wiring, terminations are good, and everything is connected the way it should be. John is 100% convinced it's an electrical issue -- but after replacing all the above parts, whats left electrically? I guess I'll see if I can find a wire harness on ebay...

Any further thoughts?!? I'm baffled, i thought these things were as easy as a lawnmower to work on..

[laramie LC4]

got correct timing?

only a few things keep an engine from running..... fuel, spark, compression, timing.

if your mech hasn't been able to solve the problem yet, after throwing all these parts at it, i hope he doesn't plan on charging you too much. at this many man/mech hours, you could have bought another xr....


oh, and i'd have another talk with your buddy about what he messed with on the bike. a screw in the valve? sounds like someone thought he knew how to do something. if he had the engine apart, he could have easily screwed up putting it back together.


good luck,

laramie

[HopheadRed]

Originally Posted by laramie LC4

got correct timing?

only a few things keep an engine from running..... fuel, spark, compression, timing.

if your mech hasn't been able to solve the problem yet, after throwing all these parts at it, i hope he doesn't plan on charging you too much. at this many man/mech hours, you could have bought another xr....


oh, and i'd have another talk with your buddy about what he messed with on the bike. a screw in the valve? sounds like someone thought he knew how to do something. if he had the engine apart, he could have easily screwed up putting it back together.


good luck,

laramie

From my research, I thought timing would be the issue. When I mentioned this to the mechanic, he said absolutely not and almost sounded offended saying, it's 100% electrical. The engine has never been apart, minus John the mechanic, taking the head off to discover the screw. He has also gone over the bike and said it's mechanically in top shape.

[Ed@Ford]

Originally Posted by HopheadRed

From my research, I thought timing would be the issue. When I mentioned this to the mechanic, he said absolutely not and almost sounded offended saying, it's 100% electrical. The engine has never been apart, minus John the mechanic, taking the head off to discover the screw. He has also gone over the bike and said it's mechanically in top shape.

the fact that the head has been off tells me double check cam timing

I believe this engine has a spark at about 10 degrees before every top dead center....but it also has a spark plug wire you can get at with an old fashioned timing light that has a inductive pickup which clamps over the spark plug wire....if you remove the small plug on the alternator, there is a set of timing marks in there...T & F...F = firing....

You'll probably have to have someone kick it over, while the other looks in the hole....if the timing light doesn't flash....well no spark....if it does flash and you see "F" in the hole...see page 16.9 of the service manual....you have properly timed spark

The process for cam timing is chapter 7 of the manual...it involves removing the cam cover....not a trivial process

[HopheadRed]

Originally Posted by Ed@Ford

the fact that the head has been off tells me double check cam timing

I believe this engine has a spark at about 10 degrees before every top dead center....but it also has a spark plug wire you can get at with an old fashioned timing light that has a inductive pickup which clamps over the spark plug wire....if you remove the small plug on the alternator, there is a set of timing marks in there...T & F...F = firing....

You'll probably have to have someone kick it over, while the other looks in the hole....if the timing light doesn't flash....well no spark....if it does flash and you see "F" in the hole...see page 16.9 of the service manual....you have properly timed spark

The process for cam timing is chapter 7 of the manual...it involves removing the cam cover....not a trivial process

I'll be sure to pass this info along to John, but the bike wasn't running prior to the removal of the head. As I mentioned before, he was confident it's not a timing issue and was almost offended when I mentioned it. Lol...I'd like to not doubt this guys mechanical abilities, especially since he came highly recommended by more than one person here, but how it's such a simple machine! I know this thing is killing him...but not quite as much as its killing me i bet!

[Ed@Ford]

Originally Posted by HopheadRed

I'll be sure to pass this info along to John, but the bike wasn't running prior to the removal of the head. As I mentioned before, he was confident it's not a timing issue and was almost offended when I mentioned it. Lol...I'd like to not doubt this guys mechanical abilities, especially since he came highly recommended by more than one person here, but how it's such a simple machine! I know this thing is killing him...but not quite as much as its killing me i bet!

DUH!! My bad for failing to not properly note it was not running B4.....probably because if the valve being jammed with the screw

my xr used to be a real PITA and not even pop....but if I shoot some starting fluid or butane lighter fuel in thru the bowl overflow on the LH side of the carb (with the throttle open) then close the throttle, it would always pop and run up enough to tell me "the normal fuel system has a problem"...it found a plugged slow jet....and upon removal to clean it....the main jet had vibrated out and ended up in the float bowl. Sure...this is a very odd coincidence...but it did happen!!

[HopheadRed]

Originally Posted by Ed@Ford

DUH!! My bad for failing to not properly note it was not running B4.....probably because if the valve being jammed with the screw

I was really hoping that was going to be the issue! Unfortunately, it's compounded since than! Thanks for your input though, I appreciate the help.

[Luke]

Originally Posted by HopheadRed

From my research, I thought timing would be the issue. When I mentioned this to the mechanic, he said absolutely not and almost sounded offended saying, it's 100% electrical. The engine has never been apart, minus John the mechanic, taking the head off to discover the screw. He has also gone over the bike and said it's mechanically in top shape.

A few random thoughts:

So it has a strong spark, but the mechanic is 100% sure the problem is electrical. Uhhhh.. ok. The spark could be at the wrong time, but the most likely cause of that is a sheared flywheel key.

Not that I think you need one now, but for general reference you can make your own peak voltage adapter



The half wave version is what the manual calls for, the full wave version is IMO a little easier to use as you don't need to worry about polarity.



Hook it up to a good digital meter (a $30 radioshack one is fine, the $4 harbor freight meter is not) and it will save hours of guessing.


After John found the screw in the valve, did he check that the valve sealed properly? I would expect the valve to bend a little from that.

Is the choke plate in the carb in good shape? Missing a screw???? How about the spring on the flap. Is it holding the flap closed?

I'd change the pilot jet to 62. On my bike, 60 ran slightly better, but 62 made it easiest to start. It was very hard to start it with a 55, even with e-start, even at highish altitude.

Speaking of.... the drill test may not mean anything. The e-starter doesn't turn the motor over fast enough to get the CDI to fire, converted bikes usually use the TRX CDI which will fire at low speeds. The drill may not be turning the motor fast enough to get spark.

[Ed@Ford]

LUKE:

That peak voltage doodad is SLICK!!!

[HopheadRed]

Originally Posted by Luke

A few random thoughts:

So it has a strong spark, but the mechanic is 100% sure the problem is electrical. Uhhhh.. ok. The spark could be at the wrong time, but the most likely cause of that is a sheared flywheel key.

yeaaaahhhh... What would cause a sheared flywheel key? I just don't understand the fact that it was running previously with the DS kit - kinda makes me lean towards wiring?

Originally Posted by Luke

After John found the screw in the valve, did he check that the valve sealed properly? I would expect the valve to bend a little from that.

Yes, the valve was not bent - He initially thought it was, but that was prior to removing the head to find the screw. He said the valve was surprisingly not damaged and seals fine.

Originally Posted by Luke

Is the choke plate in the carb in good shape? Missing a screw???? How about the spring on the flap. Is it holding the flap closed?

Choke assembly and carb are in good order and clean. Spring is tight, etc.

Originally Posted by Luke

I'd change the pilot jet to 62. On my bike, 60 ran slightly better, but 62 made it easiest to start. It was very hard to start it with a 55, even with e-start, even at highish altitude.

Speaking of.... the drill test may not mean anything. The e-starter doesn't turn the motor over fast enough to get the CDI to fire, converted bikes usually use the TRX CDI which will fire at low speeds. The drill may not be turning the motor fast enough to get spark.

This def crossed my mind - after what I've read between here and TT, I was thinking along the lines of this knowing you have to kick this machine like you mean it. But I would think between the drill and the car-powered roller to try and bump start it it would fire.

[HopheadRed]

Originally Posted by Ed@Ford

LUKE:

That peak voltage doodad is SLICK!!!

+1 on the custom adapter btw! Sweet!

[IronSpadeCycles]

Originally Posted by Davidjohnson

Any suggestions? The bike is a '98 model and has been uncorked, but stock otherwise.

thx

David, I did a big ride in CO last year down near Durango after driving up from the TX gulf coast. My Mikuni/Sudco catalog suggests a reduction of one jet size per 1750 vertical feet of altitude change. Are you running a Trail Tech computer? I'd use it as a tell tale to help you with final jetting. If your riding around at 70-80F degrees air temp and getting CHT (cylinder head temp) in the 190-230F range your about right jetting wise. I was getting in the 295+ range with several situations of it going over 300F when it got hot riding down around 6000 ft. I ended up going back to what I thought was stock jetting.

Although I had a suggestion for jetting from the local area Honda shop in Durango, my bike ran very hot the whole weekend at altitudes in the 9-11K ft range near Telluride. Turned out the shop was basing the jetting figures on stock jetting for a 2001 XR4 (which is lean to begin with) but my bike was equipped with a high comp piston I was unaware of, (I bought the bike used and it had changed hands 3 times in 10 years). The jetting I had in the bike at sea level was running lean at best and probably restricting it so when I blindly changed over to what the shop suggested I really leaned her out, well beyond what I needed for 9000ft+ altitude.

Jetting is a very touchy subject, we can all make suggestions and when you blow up your bike taking our advice, who's really to blame? The trick is to have some kind of data collection device like the Trailtech computer, it will give you all the needed info as well as help you keep from running out of gas while on your ride. One suggestion is because the spark plug is such a bitch to get to in an XR4 the heat sensor should be attached to the top valve cover bolt between the upper engine mounts instead of the spark plug. While doing this figure the actual CHT at the combustion chamber is probably another 30-50 degrees hotter than what will read at the outer most extreme of the valve cover. Take this in consideration. So with the sensor placed there on the top of the head your ideal CHT read out on the TrailTech should be between 150-200 depending on outside air temp (obviously it will read hotter if ambient air temp is hotter then 80 degrees)

I hope this helps. I've purposely not just given you an ideal jet size cause every bike is a little different and your idea of "uncorked" may be very different than my interpretation. So if you know your bike is spot on at sea level and your intended riding area is on average 7000 feet, you would reduce the jet size by 4 sizes (7000ft/1750= 4) (Mikuni jets are in steps of 10 equals 1 full step and 05 is a half step) So if 162 was stock dialed in sea level jetting a reduction to 122 main is what they suggest, but again this is only a suggestion.

I found another link that explains it a little better and I hope this helps you out. Best thing you can do is get several main jets and a couple pilot jets. If your having trouble starting the bike change the pilot jet, if your running hot overall change the main jet. Always error to the fat (rich) side, worst thing is you'll run cool and foul a plug, error to the lean side and well grenades make noise. The two circuits will work together but just changing the main for areas in the 3000-5000 ft range won't really be a big deal, anything higher you will need to change both. Leaving in your stock pilot at 3-5K ft and you won't need your choke to start the bike, anything over 5K ft and the bike might not start at all and just flood out the plug.

Later Travis

http://www.4strokes.com/tech/howtojet.asp

[IronSpadeCycles]

I almost forgot, keep a 6mm 1/4" drive socket with a short extension and ratchet in your tool bag with a 17mm wrench and a short Phillips and straight blade screw drivers. If you need to change just the main jet on the trail it can be done in about 10 minutes, if you need to pull the bowl to change the pilot it will take about another 5 minutes. Trust me I know I did this several times over a few weeks and 5200 miles logged from Durango CO to Portland OR and back to my home town of Port Lavaca TX. You don't need to remove the carb or even turn it, just drop the lower bowl drain screw with the 17mm wrench. When you get the main out take care not to loose the small white plastic skirt that shrouds the jet. I often used a dab of grease to hold it in place each time I changed a jet.

Hope this helps.

Later Travis

[Davidjohnson]

Travis, thanks for posting this. I will need time to digest all of it but it is very helpful. I do not have any kind of monitor that reads temp but will look in to that.

David