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Post Info TOPIC: Piston Rings ????????


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Piston Rings ????????
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Why when you fix one problem does another problem appear????

Finally got my DT running ok, pulling through the rev range!

Then today while thrashing it off road ( racing my brothers CRF450)...... started to lose power again..... a couple of backfires...... then nothing!!disbeliefdisbelief

Piston rings??? What compression should I be getting? Think its time for a strip down.



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Isnt that just petrol? Mine looses power then backfires(Not very big but my mates dtx with full arrow shot a flame once) then cuts out then i put it on reserve then im off again to the petrol station =]

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Wish it was just petrol. Nearly a full tank!!!

There's no back pressure when I kick start it now. So pretty sure piston rings or worse could be the cause.

I'll need to get the compression checked out, anyone know what compression reading I should get?

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130 or something?

if the rings suddenly went you'd prob know about it..



-- Edited by element on Saturday 12th of December 2009 01:40:05 PM

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04' DT125RE 32k miles and counting / 89' DT125R 3RN1 Rebuilt + Supermoto'd.
"Those who risk nothing, do nothing, achieve nothing, become nothing" 


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stripped the engine out the Dt today.
The piston rings are defo goosed, so is the piston!
The bore feels ok but might get it ground anyway when i'm this far in,what is the maximum regrind bore dia??  Is there anything else I should do when i've got the engine out?

Couple of pics from today:DSCF6174.jpgDSCF6175.jpgDSCF6176.jpgDSCF6166.jpgDSCF6167.jpgDSCF6168.jpgDSCF6161.jpgDSCF6160.jpgDSCF6048.jpgDSCF6171-1.jpg



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i hope you clean that engine before you put it back :) the bore does look very scratched probabably a good idea to get it rebored just incase theres anything you have missed?

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Will defo clean it all down before I rebuild it. Couldn't clean it before I stripped it down as my hose pipe is frozen solid & everything is covered in snow. Too impatient to wait on it defrosting in a week or so!!



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Try and find somebody that has a deglazer i've managed to get tractors running sweet as a nut after sticking one of them down the barrel after they've been like that and its got rid of it. But this won't work if there are deep gauges in the bore.

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should be over 100 to run, see if you can buff out the scores with 1200 sand paper, also did you run it in for 500 miles because it looks like you havnt beded engine in, looks more like youve force it to bed casuing it to score the sh*te out of it smile.gif

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I didn't replace the piston rings previously. I'll try & give the bore a rub with wet & dry paper. If that's no good I'll probably take the head into my work & try & grind the bore out.
The piston rings were actaully siezed into the grooves. had to snap them to get them out.


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you can get a rebore for £30.. Id get it bored..can get pattern piston kit for £25 and then £20 for gaskets which you gonna need anyway..

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04' DT125RE 32k miles and counting / 89' DT125R 3RN1 Rebuilt + Supermoto'd.
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alrgt element where do you get bores for £30? is this guy in plymouth? let me know the name of the company,cheers mate smile.gif

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http://www.stanstephens.com/street.htm


under rebores m8.. not local though..

-- Edited by element on Saturday 2nd of January 2010 06:03:20 PM

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04' DT125RE 32k miles and counting / 89' DT125R 3RN1 Rebuilt + Supermoto'd.
"Those who risk nothing, do nothing, achieve nothing, become nothing" 


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nice1 thought it be more expensive, nice1 just gota sort the postage, have you used them? i reckon £7 for me to send, i wonder what they charge for sending it back? im gona try call em tmrow smile.gif cheers smile.gif

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I'm going to rebore the engine myself.

Does anybody know what the oversize bore Dia's are?

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i totally rebuilt my top end and bottom end a few months back...after piston failure. Seized up. The piston done 20K miles! It was knackered. out of round which caused the seize in bore. with too much piston bore gap. in places. Cracked skirt too. But it done the miles.


New rebore, new piston, new rings..all went well, but hell.. a very good grandad driving 500 miles will set u right.. dont go blasting around on a new top end build. It will seize due to the small tollerences, it needs bedding in.. ive have done 2K now on it now all brill!..thats doing 9K revs on carrageways for 15 miles all day with out problems. Make sure you get the head skimmed too.. I didnt! and it leaked like a pig. 2 head gaskets later! wish i did it in the first place.

goood luck

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DTR125CRAZY wrote:

nice1 thought it be more expensive, nice1 just gota sort the postage, have you used them? i reckon £7 for me to send, i wonder what they charge for sending it back? im gona try call em tmrow smile.gif cheers smile.gif




rebore and hone isnt a big job.. almost a 5 minute job!

stan stephens is the daddy at 2 strokes though mate.. I'll be sending mine there when it needs doing (and maybe get a stage one, bit of mild porting).. mate of mine had his gsxr 750 (slabside) done there. he was well happy!

failing that theres a place at marsh mills. 2 wheel technica or something like that.. there are supposed to be good to but then they probably outsource all the rebores anyway.. 

there is also another guy but the name has gone.. he is like stan stephens... legend 2t tuners..

 

 



-- Edited by element on Tuesday 12th of January 2010 03:14:14 PM

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04' DT125RE 32k miles and counting / 89' DT125R 3RN1 Rebuilt + Supermoto'd.
"Those who risk nothing, do nothing, achieve nothing, become nothing" 
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