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Old 06-06-2011, 11:42 PM
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Default smoky xr400

     

i know, its an xr400 and all xrs smoke, but this one looks like a two stroke kinda smoking... so, once its warm, it still smokes but it runs super nice! so what could it be? valves havent ever been touched, literally. i think there still stock positions. and never had a new top end, so its in need of some love, what should i do? im going to adjust the valves soon if that would work (not me, ill have the local shop do it)
as far as ive gotten, i think im going to buy new valve guides and a new top end, would that do the trick?

---------- Post added at 10:42 PM ---------- Previous post was at 09:50 PM ----------

mainjet... i could use your help right now
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Old 06-07-2011, 06:29 AM
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Originally Posted by supercr125 View Post
i know, its an xr400 and all xrs smoke, but this one looks like a two stroke kinda smoking... so, once its warm, it still smokes but it runs super nice! so what could it be? valves havent ever been touched, literally. i think there still stock positions. and never had a new top end, so its in need of some love, what should i do? im going to adjust the valves soon if that would work (not me, ill have the local shop do it)
as far as ive gotten, i think im going to buy new valve guides and a new top end, would that do the trick?

---------- Post added at 10:42 PM ---------- Previous post was at 09:50 PM ----------

mainjet... i could use your help right now

can it not be something as simple as worn rings? What colour is the smoke? Smokes on accelleration/decelleration/always?
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Old 06-07-2011, 06:40 AM
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mainjet... i could use your help right now
You should have enough PM's to get you going....
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Old 06-07-2011, 08:44 AM
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You should have enough PM's to get you going....
i do, that was posted before the convo tho
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Old 06-07-2011, 09:38 AM
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i know, its an xr400 and all xrs smoke,

---------- Post added at 10:42 PM ---------- Previous post was at 09:50 PM ----------

mainjet... i could use your help right now
Dude ... not ALL XR's smoke.... is a matter of fact they shouldn't I think Main probably helped you out on this one already. Probably valves and rings would be my guess.

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Scott
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Old 06-07-2011, 12:22 PM
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yea sorry roost just alot of the people (so called "mechanics") say xr`s smoke, i dont beleive them. im going to fix this asap!
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Old 06-07-2011, 01:51 PM
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They don't all smoke; and they shouldn't, really. I have noticed that a lot of them do because their owners have found that they don't have to care. They keep the oil topped off and ride them for years that way. Not that I would recommend that of course.
With any big thumper, if you flood it good (and you will), the excess gas in the cylinder will wash oil out of the rings and it will smoke pretty good for a couple minutes. All the more reason to get your starting regiment down asap.
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Old 06-07-2011, 01:54 PM
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i wonder if adjusting the valves and running some seafoam thruough the bike would help the smoke any
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Old 06-07-2011, 02:08 PM
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i wonder if adjusting the valves and running some seafoam thruough the bike would help the smoke any
With a newly-purchased bike, I'd go in and fix it right. If you don't know its recent past, you don't know if something serious is close to happening.
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Old 06-07-2011, 02:10 PM
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As valve guides and seats get old they tend to leak and cause bikes to smoke and that is more often than not what the issues are with older 4-strokes.

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Scott
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Old 06-07-2011, 02:17 PM
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im just going to put 200$ into top end and valve guides and seals and getting the valves lapped
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Old 06-07-2011, 02:26 PM
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im just going to put 200$ into top end and valve guides and seals and getting the valves lapped
That should take care of it for sure....

Thanks
Scott
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Old 06-07-2011, 02:29 PM
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yep! ill have the shop take it apart and see if the piston needs replacing, if not, ill have him slap on some new OEM stock rings on there and save me some $$$
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Old 06-08-2011, 05:38 AM
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What the heck dude, your not gunna jump into it yourself, those bikes are pretty simple I think you can handle it Minus doing the guides
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Old 06-08-2011, 08:38 AM
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What the heck dude, your not gunna jump into it yourself, those bikes are pretty simple I think you can handle it Minus doing the guides

No kidding they are and the best part is that the dang valves are not the shim type.....

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Old 06-08-2011, 09:05 AM
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It really isnt worth trying to lap a stock honda (stellite) valve. Yours may be happy just getting the guides knurled and a new set of seals. while you are there a trip up and down the cylinder with a hone and then reassemble with a nes set of rings may extend the useful life of everything else. Maybe spend on some new exaust valves while you are there.

So called mechanics who tell you that all xr's smoke are just used to older ones which keep on running, and running, and running.
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Old 06-08-2011, 11:04 AM
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you guys think i could do it? im going to buy or borrow a workshop manual before i tare into it if i decide to do it myself, the library should have a nice clymers, ill see how it all looks once i get in there! im going to pre order vale guides and valve guide seals before i buy a set of rings just incase i need a whole top end
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Old 06-08-2011, 11:22 AM
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Originally Posted by supercr125 View Post
you guys think i could do it? im going to buy or borrow a workshop manual before i tare into it if i decide to do it myself, the library should have a nice clymers, ill see how it all looks once i get in there! im going to pre order vale guides and valve guide seals before i buy a set of rings just incase i need a whole top end
If I recall correctly most of the XR's just needed valve work to fix problems like your having, but don't hold me to that, it's been 20 years

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Scott
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Old 06-08-2011, 11:43 AM
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ok please note that if you are going to change guides that you will most likely have to recut the seats as the guides sometimes vary and if you are going to install them with a press or a driver they likely are going to "locate" slightly differently. I find that machine shops can knurl them and i get a better fit using the old valves that way. usually when guides are put in at home you can find the leaks in the valves with a flashlight afterwards.

A valve job on an older rig that winds as high as those do is usually an all or nothing type of thing to make it worthwhile. if your rings and cylinder are worn it will show more after the better sealing valves are helping to create a betting vacuum.

so you may want to live with it smoking, or just replace the seals which you can do without removing the head in most cases.
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Old 06-08-2011, 12:24 PM
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alright so then IM not going to replace the guides, if they need to be replaced ill have a shop do it, but ill do the seals and rings
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