XR400RMan

Member
Dec 11, 2000
213
0
Well as some of you know I have a 91 XR250R that I had the entire engine rebuilt,Cylinder Head,Cylinder Head Cover,All internal parts,Cylinder and Sleeve. When I got it back together it was burning oil, Well the ones of you that read the post a good while back wanted to know what happened so it ended up being the Piston Rings, The thing is I haven't had the new rings put in yet because I have been waiting for them to arrive at my Dealer, What I want to know is this-ok you know when you change rings you have to be very carefull because the slightest bend can break them? Well you can take the rings that were on my bike and twist them like a twist tie you put on bread,potato chips etc and they won't break!! What could have happened, My dad said if the bike overheated then it would make that happen. But all my riding was during the cold months and I wasn't riding any tight trails so I know it didn't overheat from not having enough air blowing across the fins, Remember that I discovered that the right side exhaust Valve wasn't operating properly and was forcing most of the gases out the left one, Could this had let the bike get to hot by not letting it breath enough or something? I want to know what most likely caused it before I get it back together and then have to tear it down again because it happens again. So do any of you know what caused this? Thanks Matt
 

jmics19067

LIFETIME SPONSOR
Jan 22, 2002
2,097
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thats pretty bizarre. I would have no clue but my guess would be that since you never got the rings to set the blow by got them hot enough to take the temper out?!? :think:
 

IrishEKU

A General PITA.
LIFETIME SPONSOR
Apr 21, 2002
3,808
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XR400RMan,
"Remember that I discovered that the right side exhaust Valve wasn't operating properly". Could it be that your valve seals are seeping oil ito the combution chamber?
 

DEANSFASTWAY

LIFETIME SPONSOR
May 16, 2002
1,192
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What was the cylinder finish like. Not to be a smartass or any thing but Ive seen bike cylinders bored out and never finish honed . This either happens when a customer takes his cyl to an industrial machine shop or takes the cyl to a place that just doesnt know. Think about it , If you take a cyl to a machine shop and say botre this out thats what you might get . In the past 15 years or so Ive seen it about 4 or 5 t imes . Ive also seen machine shops bore out the Nickasil and hone the Aluminum to fit a new piston . This would last about 5 minutes in your bike , Ive seen this about 3 times. Some lawnmowers actually have alum bores (unplated ) and they run special rings . CHEERS
 

DEANSFASTWAY

LIFETIME SPONSOR
May 16, 2002
1,192
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Were the rings stuck in the piston when you took it apart? Doesnt your XR have a steel sleeve ? were there grooves or scuff marks ? Was this the motor that you thought the oilwas boiling in the cases. Did the rings turn blue from heat ?
 

XR400RMan

Member
Dec 11, 2000
213
0
Sorry it took me so long to reply,Been Busy. No the Cylinder Bore looked Great, I just took a brief look at the rings and I didn't see any Blue on them but I didn't look closely, I'll have to ask my dad. Yeah it does have a steel sleeve. The head was in great shape also except for some carbon build up, I have one more question, Since my XR was only really running with 1 properly working exhaust valve(The right one was just barely opening)Since the valve is working right now how much more power will my bike have? Also since it should have more compression since the rings wern't sealing, I used to get in 1st or 2nd gear and I couldn't get the front up no more than maybe 2 inches, Will I be able to do wheelies easy now? My dad said it would probably have 25 to 30% more power than it did before, What do you guys think? Matt,Thanks for the help,
 
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