glazed cylinder bore on brp


16 replies to this topic
  • xrvince

Posted November 25, 2004 - 12:36 PM

#1

i spoke to my mechanic about my brp loosing oil and he said it could be as simple as a glazed cylinder,what would cause this ?could it be a bad run-in procedure or just bad luck? he said it will need honing out and new rings and that should solve the problem of it burning oil ,i will throw a set of valve stem oil seals while i'm at it .has anyone elses come accross this prob and fixed it? :cry:

  • frankstr

Posted November 25, 2004 - 01:55 PM

#2

My BRP dos'nt have any oil issues... :cry:
Have ya got it hot at all,That could glaze the cyl. wall..
How much time is on it???

  • xrvince

Posted November 25, 2004 - 02:32 PM

#3

it has 1000 miles since full engine rebuild ,don't think it has got hot ,atleast the coolant hasn't spat out of the cap,it had a new rod ,re-nikasiled barrel and new piston.

  • HeadTrauma

Posted November 26, 2004 - 09:22 PM

#4

Was it broken in on petroleum oil? Maybe it wasnt broken in hard enough...

Does it just use oil, or does it smoke? If it smokes, does it do under acceleration, deccelration, just on startup, etc?

  • roadcam

Posted November 27, 2004 - 02:21 PM

#5

if ya get to the point youre looking at a rebuild, just to compensate for glazed cylinder walls .... the time-tested old mechanics trick ( yes, Im an OLD mechanic ), while running the engine at fast idle, sprinkle a SMALL amount of BON-AMI kitchen cleanser thru the carb throat ... this will etch the glaze without damage ( bon-ami isnt overly abrasive ) ... the blue oil smoking should cease almost immediately ... when it does stop, shut it down, and change the oil and filter ... change it again after 30 minutes of riding ... you're good to go .. I know this sounds pretty shadetree, but I have personally watched GM Technicians flown to our garage on unsolved warranty claims, do just exactly this method ... same with Cummins diesel engine factory technicians ...

  • savageracing

Posted November 27, 2004 - 02:41 PM

#6

I Agreewith Roadcam. Look At This Way. You Are'nt Going To Hurt Anything That You Would'nt Have To Replace Anyways. It Is Worth A Shot.

  • xrvince

Posted November 28, 2004 - 09:56 AM

#7

when it smokes it does it when you close the throttle and accellerate hard ,i look back and close the throttle at about 40 mph and whack it open hard and it gives off a puff of white smoke .

  • roadcam

Posted November 28, 2004 - 12:24 PM

#8

when ya let off the gas, then slam it back on, your engine vacuum is pulling the oil up past the rings, and possibly valve guides ... no big deal, engines dont self-destruct from over-lubrication ... as long as its not fouling the plug, or compression so bad it wont run.... ride it like ya stole it ! :cry:

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  • xrvince

Posted November 28, 2004 - 01:20 PM

#9

it never used to burn oil at all till the big end went ,since then it was rebuilt with the 12/1 high-comp piston,stage 1 hot cam ,carrillo rod,xr's only high rev kit ,mikuni tm 40 carb and big gun headers with a leovince x3 titanium race can and a ported head .last dyno run was showing 60rwbhp and the bike is in supermoto trim and is awesome comes up in fourth with a slight tug on the bars.it eats most other supermoto bikes and some sports bikes on the road .

  • xrvince

Posted November 28, 2004 - 02:09 PM

#10

when ya let off the gas, then slam it back on, your engine vacuum is pulling the oil up past the rings, and possibly valve guides ... no big deal, engines dont self-destruct from over-lubrication ... as long as its not fouling the plug, or compression so bad it wont run.... ride it like ya stole it ! :cry:


why would there be such a strong vacum ,would it be glazing that allows the oil passed the rings ?or could it be a crankcase breather problem?i'm going to put a k&n breather on the crankcase breather hose and blank the airbox inlet off ,so there will be no breather tube to get squased by the tank anymore.could abnormal crankcase pressure force oil passed the rings?

  • zx7rye

Posted November 28, 2004 - 04:53 PM

#11

could abnormal crankcase pressure force oil passed the rings?


Unlikely...It would find the path of least resistance...which is a seal (pushrod, countershaft etc.).

  • roadcam

Posted November 28, 2004 - 05:02 PM

#12

breather hose would be unlikely to contribute, just from the fact that it has very little pressure in it, surely not as compared with either engine vacuum , or compression ... the oil simply is pulled up past the rings (blow-by) because of a poor, worn ring/cylinder seal caused by ring/cylinder wear, or a glazed cylinder which does not provide a good seal, or both ...

  • CRUDE_DUDE

Posted November 29, 2004 - 02:52 AM

#13

I had a bike that I had hopped up with porting, piston, valves...and from the day I picked it up it smoked on warm up or when I'd whack the throttle. I went round and round with that builder. He even did the bon-ami trick--a water and bon-ami mix and then sprayed in into the carburator...but didn't fix the problem. Eventually I had it torn down by someone else and it turned out that the ring gap had not been set. New set of rings end gap file fitted properly will probably fix your 4smoker. JMHO

  • xrvince

Posted November 29, 2004 - 08:53 AM

#14

would a too small ring gap cause the smoking ? :cry:

  • roadcam

Posted November 29, 2004 - 09:02 AM

#15

if your rebuilder set the engine up too loose, or just plain wrong, of course the Bon-Ami trick wont do any good.....I answered the original post as to how he could reduce or stop his oil-burning.... I hope this isn't too hard for some of you to either understand, or believe... but Bon-Ami also wont fix flat tires, either... sheesh!!...maybe I shouldnt try to help you younguns...

  • CRUDE_DUDE

Posted November 29, 2004 - 01:10 PM

#16

if your rebuilder set the engine up too loose, or just plain wrong, of course the Bon-Ami trick wont do any good.....I answered the original post as to how he could reduce or stop his oil-burning.... I hope this isn't too hard for some of you to either understand, or believe... but Bon-Ami also wont fix flat tires, either... sheesh!!...maybe I shouldnt try to help you younguns...




My post was not in any way meant to devalue anything anyone else had offered in the way of help and I appologize for coming across that way, roadcam. :cry:

Most ring sets, I believe, come with detailed instructions on setting/filing the gap. I'M NOT A BUILDER, but from being in the shop this is what I saw--It consists of putting the (top) ring on the piston and then running it in the cylinder. With the dome an inch or two below what would be TDC use a feeler guage to measure the endgap (I think he had a special set of feelers to do this). You'll then have to pull the ring and file to meet spec. Again, I'm not a mechanic or builder, this was just me relaying a similar experience...BTW, if I remember correctly, it was just the top ring that had to be fitted. (All this can be done on the bench...)

And yes, too small of ring gap was my problem and I'm thinking that may be yours also.

Jim

  • xrvince

Posted November 29, 2004 - 02:51 PM

#17

i build my own engines and on the first hop up i did the ring end gap and had to file a tiny bit off the compression rings but after the big end seized i rebuilt it again and put a new piston in but didnt do the ring end gaps on it,so you could be right.have some new rings and gaskets coming tommorow so i will have to pull the top end off and have a look at it may have to re-hone the barrel.





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