650L top end rebuild now backfiring and smoke from the engine

Hi all.  I just recently rebuilt the top end on my 2000 XR650L.  It was run low on oil and trashed the cam journal.  I sent it to XRs only and they remachined the journal and did a valve job.  I installed the new head and put it all back together.  I put a HotCams stage 1 cam in it.

 

Bike fired right up and idles ok.  When I rev it and let off though, it backfires and it looks like there is smoke coming from the engine!  

 

Any help or suggestions would be great, I just want to get this thing running so I can sell it and get a KLR.  I'm done with this thing!

Smoke from the engine? Like when oils on the header and smokes up? Or puffs from the tail pipe?

Need more information about the smoke, where exactly is it coming from?

Too bad, I would never trade my XR for a KLR.

Smoking would be normal for a fresh top end the rings haven't seated yet.  Have you "broke" in the engine yet?   Most re-builds will burn oil for about 500 miles while the rings seat.  Is it backfiring throught he intake or exhaust, if intake then richen up the pilot screw if through exhaust then lean out the pilot screw.  

As I said, the smoke is coming from the engine, like the head.

 

Basically, if I rev it up it chokes initially on the way up and backfires after I let off the throttle on the way down.  Then (only can see it at night) there is a puff of smoke that radiates from the engine head.  I did not put new piston and rings, just the cam and valve job.  

 

Based on what I've read, could it be the timing chain is off a tooth?  I hope not, I don't feel like tearing it apart again.  Could this be the issue?  I'm going to recheck the valve clearance tonight again.  The jetting was fine before the rebuild...  Done by a mechanic.

The jetting was fine before the rebuild...  Done by a mechanic.

 

Fine how? Do you know what the jets were then or now? You can't just do power mods like a cam without paying attention to the jetting.

 

you also need to isolate where the smoke "puff" is coming from.

 I did not put new piston and rings,  

 

 

Did you pull the jug and piston out of the bore?

 

The smoke seams like an exhaust leak.  New copper gaskets?  

 

It could be off a tooth.  Yes, that would explain the backfire.  I use a piece of wire in the spark plug hole to feel when the piston is at TDC.  The marks on the flywheel can be confusing.  Loosen the rocker cover and peak inside but make sure it's on the compression stroke at TDC otherwise the cam will push the rocker cover up which is OK actually but makes it hard to tighten back down..

Edited by Baja Rambler

I say go to the KLR topic and ask them

I say go to the KLR topic and ask them

Why do people like you even bother being alive?  GFY

Why do people like you even bother being alive? GFY

You kinda had it coming... haha

I bet its a gasket leak kand oils seeping onto your header and you dont notice it cause it a slow seep that burns off before accumulating. There arent any "holes" in the head open to the atmosphere. Even if your inspection cap o rings werent there or the breather hose i dont see smoke coming from INside the motor. Id tighten all the rocker rod bolt are where the copper rings are and maybe inspect the front of your valve cover gasket.

And take it eeeeeezzzyyy man. Of course you gonna get shit for saying your gonna get a klr on here. Just get a purple one and be sure to post a pic.

PS. Not talking shit here but learn the motor, its a simple one. Forget xrs only exists and rebuild it with just tools and a manual and us here on TT to help...

i don`t see anywhere the OP saying he pulled the cylinder,,he rebuilt the head and re-installed???????

 

or am i missing that..........????

 

If the cylinder wasn`t pulled ,,and it was run low on oil,,the piston is likely toast on the thrust side,, you did 1/2 a rebuild.....

 

Smoking from the head.....possible exhaust gasket leaks????..or residual oil burning off??????

 

B

Edited by brianhare

Yeah, I've asked a lot of unanswered questions on this site.

 

Sometimes they just tear off the covers and eat the pages.

Ok, so i tore it apart again today.  Piston and rings were fine btw.  I checked the timing, it may or may not have been off, but i quadruple checked the tooth alignment and reinstalled.  Put it all back together.  Disregard the smoking problem, it was the headers being uneven when tightened and is fixed.  

 

Problem is still there though:  Hesitation when adding throttle and backfiring when letting off.  It is not as bad now though?!?!  I find it hard to believe that jetting would cause this much backfiring.  Any suggestions on what to try next.

 

Also, if you don't have anything helpful or constructive to say, seriously GFY, I don't have time for &%$#@! in real life let alone on the internet.  If that's how you get your rocks off and you have nothing better to do than criticize people for riding a different motorcycle than you, I'd seriously consider walking into oncoming traffic.  No really go... right now!  If I wanted to deal with twelve year olds I'd go to an xbox forum or the chive.  Grow up.

Problem is still there though:  Hesitation when adding throttle and backfiring when letting off.  It is not as bad now though?!?!  I find it hard to believe that jetting would cause this much backfiring.  Any suggestions on what to try next.

Drop the float bowl, see what jets are in there, and get back to us. It would have been far easier than tearing the top end apart...again.

 

Also, if you don't have anything helpful or constructive to say, seriously GFY, I don't have time for &%$#@! in real life let alone on the internet.

Likewise, we don't have time for people with giant chips on their shoulders that demand free help and cop an attitude while doing it.

Header to muffler connection leak free?

 

go a half turn out on the fuel screw see if its any better

 

hesitation just sitting in the garage revving it up or riding it?

 

good luck

Also, if you don't have anything helpful or constructive to say, seriously GFY, I don't have time for &%$#@! in real life let alone on the internet. If that's how you get your rocks off and you have nothing better to do than criticize people for riding a different motorcycle than you, I'd seriously consider walking into oncoming traffic. No really go... right now! If I wanted to deal with twelve year olds I'd go to an xbox forum or the chive. Grow up.

Woah big boy with a big boy job calm down

So this guy has to put his own dick in his own ass (GFY)...AND walk into traffic? Damn homie, you sound like the chipped shoulder em effer right here!

Calmateway! Being a pig owner is a right of passage. Go get a klr and throw away this baja winning brotherhood that is the xr.

I got plenty of time for a holes. Bring it my way

Edit: i think keeping you off a klr and out of xrs only is plenty constructive.

Edited by notoriousE-R-I-C

Agreed ^

|

The hesitation is when revving from idle to max rapidly.  Then it backfires on the way back down when letting off.  I'm going to try and check the jetting later today.  

 

As far as the headers go, is there a trick to installing them?  Something I missed?  I installed the bolts and nuts and the semicircular holders IAW the Honda manual and torqued them to specs.  Also new metal O rings when I put it back together.  Could this be an issue with valve clearance?

 

Apparently some of you missed Tate's post.  I don't have a chip on my shoulder at all, I just don't have time for immature people being jerks for no reason.  I came here asking questions and looking for some advice from people with more experience than me.  Based on previous experience I thought the dual sport community was a pretty good group of guys and gals in general.  I guess there are a few bad apples out there.  I personally don't care what you ride, Harley BMW Goldwing or a moped, the important thing is getting out and riding, not the kind of equipment you have.

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