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smoking xr400

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I have a stock 01 XR400 that is putting out a lot of whitish smoke. There's probably a little more when it's first started but it keeps smoking even when hot. A couple of months ago I sank the bike in a puddle and took a lot of muddy water into the engine. I changed the oil til it was clean and the bike seems to be running well except for the smoke. I don't get to ride much and the bike stays parked for months at a time.

Any ideas on what the problem is?

Thanks.

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Did it start smoking soon after sinking it? If you got muddy water into the cylinder, dirt could have scored the walls allowing some oil to get through. If you have no power loss, i would not worry about it too much, just make sure you check your oil often.

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Yea, I never noticed any smoke until it got the water in it. If it was just a little smoke I wouldn't worry about it, but it's a lot.

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Well, I have a 98 400, and it started to smoke really bad about a year ago. (just from wear and tear, no water). I went ahead and got a wiseco piston and rings (next size up from stock) and had the cylidner bored and honed. I also put stainless steel valves in, but this is not necesary imo, i just did it cause i had the top end open, and had the money. I would at least replace the valve stem seals if i were you since you said it smokes more at startup than when hot. You should be able to get the bore/hone/piston/rings/top end gasket set for around 200 or so if you take it apart and reassemble it yourself. Good Luck!! I think the store hear has all the parts you will need, anyone got any links?

You should at also see if the valves seep while you have it apart, and check the cam chain for any excessive play.

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:banghead:🤣:banghead: Hello Chud,are you sure you cleaned it out good enough? If it started this bussiness after it went blub blub blub,and not before than you should be on the right track,also,Mar says to blow it out real good with compressed air, but you knew that right? re change the oil again,may still be some moisture lurking some where.Hope you get it squared away. XR_Ron

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I had some smoke coming from my 99 xr 400. I had the ring and piston replaced and they said it was from water that had scored the side of the piston. They showed me the piston and it wasn't much but enough to let oil get by. I would go ahead and have a new piston and rings clips and all that put on if i was you. The only thing i need to do now is tighten the valves up anyone got any experience with this i would appreciate the help.

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My XR is smoking.

Blowing blue smoke out the back, not on start up only when hot and riding, looks like a 2 smoke. New top end done only 2500km's before. Rings gone?

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sounds more like your mixture is too rich, usually white smoke is oil. Blackish blue is usually a rich condition.

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i have this exact problem with my XR. i was following some nitwit after only having my moto a few days (it was my second ride on it ever) and i went into a puddle, so deep and hogged out by quads that when i stopped and leaned over to put my foot down there was nothing... just water. fell over and sunk the thing. anyway, i had that week off work and planned on riding the piss out of it, so i dissassembled everything down to the base, cleaned it up (there was about 1/2" of muck sitting on top of the piston) and re-installed it all. well, i'm smoking just like you are. i'm sure the cylinder needs to be honed and a new piston and rings installed. here's where one has to wonder about going bigger, 416 kit or something along those lines. right now my machine starts 4th kick after sitting for a week and first kick everytime when hot. even after dumping and spewing petrol all over the place, it'll start second kick. do i really want to muck with all that, go big, re-jet, etc?

anyway, we do some seriously iron-butt rides up here, it's not uncommon to do 100 miles of intermediate/expert trail. in that 100 miles i have to check my oil once, or i'll be about 3/4's of a quart below top by ride's end. i'm so used to this i've a small paper funnel and a quart of oil in my camelback as regular gear.

this winter, though, is the rebuild. you can send your cylinder right to Wiseco in Ohio and they'll hone it, mic it, and send you back the rings for it, or the piston and rings, as it were. then you'll know you're right on. there are many machine shops that can re-do the head for you, and if you're smoking oil, you should have it done, unless you do a leak-down check and insure that the valves seals aren't leaking (this is common XR's with some age on them).

unless Dirty B wants to make some money and help me with the hone and head. re-building the top end on this moto was the most work i've ever done on a motorcycle and, quite honestly, i found it a bit daunting. fortunately, with the help of the OEM manual, a lot of common sense mechanical ability, and my GF, it wasn't a problem. took me a day to take it down, another day to clean it, re-build it. but i'd gladly take the bike to someone's house who has done this before and pay them for the assistance. the shops around here are.... one is better off doing things one's self or sending them off.

matt

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My 98 XR4 was smoking badly too - lots of blue/grey oil smoke when hot. Thought it might just be the valve stem seals. Took it apart and found the piston and cylinder wall to be badly scored.

Bit the bullet and ordered a 440 wiseco kit. Had a local machine shop machine my barrel and fit the new clylinder sleeve, bore and hone it. Put the rest of it together myself (did the valve seals as well).

Put it all back together and I am extremely proud to say it started first kick. No smoke at all now. Loads more power and luggability. I went with the 11:1 compression piston. Am delighted with the results.

Piston kit (c/w sleeve, gaskets etc), machine shop work and new seals cost me a total of $400. Well worth it. Bike feels really torquey and has a great top end. Will wheelie off the throttle in 3rd now, no problem.

Here is the original piston showing scoring on the side. This combined with the corresponding scoring on the cylinder and worn valve seals caused my smoke and oil consumption problems.

38227428-L.jpg

Here is the damage done to the cylinder.........

38227429-L.jpg

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Valve seals is very easy. First you need to buy (or rent) a valve spring compressor. Take the head off, compress the valve springs, release the 2 little retaining 'collets' , release the tension on the compression tool and remove the valve. The seal is a little brown sleeve that sits on top of the valve guide. Just pull the old one off and pop the new one on. Repeat for the remaining 3 valves. With the head off, you can do this on all 4 valves in less than 20 minutes. Tricky bit (unless you know how) is re-fitting the valve spring retaining collets. Use some grease to make them stay in position when you release the spring compressor. The workshop manual shows you how to do all this.

Regarding the jetting, I am running a 55 slow jet and 162 main jet. Needle clip is on 3rd ring down from the top. Bike runs great that way (this is how my bike was jetted when I first bought it as a standard well-used 400cc bike).

I have ordered a selection of spare jets that I will experiment with but the bike runs great as it is. Plug is a healthy colour and it doesn't appear to run hot. I am at sea level - never above 1200 feet for the most part.

Ferg

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thanks for the help. i'll consider doing it myself. there's a machine shop near here which will re-do the head for a price. but money is at a premium now, not like in Ireland with near full employment.

where in Ireland are you and have you got a spare bike for a corker?

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Machine shop (Murphy's Engine Overhauls - yes really) did all the work for €90 euros - about $115 . That included removing old cylinder, machining barrel to take new cylinder (with a 4 thou' intereference fit), boring & honing new cylinder for the new 89mm piston and cleaning the completed assembly. Good value I reckon.

I'm from Cork (the rebel county !!).

No spare bike though - sorry !!!! :banghead:

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very good value. i have to get this smoker fixed. i'm using too much oil. are there many places to ride there or do you do a lot of green laning? i have an extra for (XR250) if you come to this side. we have 3,000 miles of established trail up here.

Oglaigh na hEireann

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