never heard so much shit!!!!!
-
- Posts: 93
- Joined: January 3rd, 2010, 3:27 pm
- Location: Australia
never heard so much shit!!!!!
am putting this on here due to the experience all 500 owners should have with the exhaust port bridge eg releiving and drilling holes in pistons.
any how please give me all your opinions on this.engine in question 2002 cr250(sorry its not a 500 but it is relevant to its prob area)
so we pulled the engine apart and it had the tiniest crack and pealing on the ehaust bridge,nickasil had started to peel at this point but the rest of the cylinder was fine,engine was running satisfactorly...so we order a new mitaka piston kit and send the cylinder and piston away to nz cylinders for a replate with a formal request for extra releif on the bridge,they call me a say they will have to weld the cracked bridge prior to replating which would be certain practice,so we receive the piston and cylinder back,job looks good nicely finished,checked piston clearance and ring gap,all fine,asseble engine,new gaskets etc,start the engine running 32:1 let it gradually warm up,do all checks all is fine run for approx 3 5 mins and turn off and let cool,drain carb and leave engine,come back the next day and turn fuel on and start and run engine to operating temp,put in to gear and drive engine through gears up and down nicely for approx 5 mins,turn engine off let cool and recheck all ancilaries,all is fine,start engine again,sounding crisp,run engine increasing rpm range and speed,going to 2 thirds throttle for a couple of runs..then it rains so we stop the bike and return to the workshop.now my friend texts me you should come and have a look at this piston it doesnt look to good! now i though he wa having me on so i rushed round there,looked up the port,n thought wtf! ther was slight seizing inthe xhaust bridge area,so i pulled the head off and couldnt beleive it was running so mint the nickasil had completly gone and the crack that was welded up was right back ther in the xact same spot???????????? hmmmm i pulled the barrel off and inspected the piston it was scuffed up and groved/fuked in that area a coresponding exhaust bridge groove and seizure on the piston and a vertical crack on the skirt in the same locality...so what would you think????i am a motorcycle mechanic of 17yrs,service manager at the local kawaski dealer ship honda for 10 years bla bla bla,,any how i have used mitaka pistons and have found them to be reputable so far, i have assebled 100s of two strokes and specialise in 500s,i am very aware of the nature of the bridge etc..so apply very stringent critisium to this area when building my engines....my opinion is this quite evidently the xhaust bridge has not been repaired properly,the crack has still been evident beneath the replate and this has quite clearly pronouced itself against the piston causing heat, damage and eventually hairline fracturing in the skirt
the rest of the cylinder and piston is fine..so am not happy as the run in procedure even though not complete was textbook to this point,i call nz cylinders and explain the situ,i send the components back for inspection and wait for there response,this is what i got"we have looked at the piston and cylinder and also called wayne "wobbly" wright(x gp mechanic, and the piston has caused the damage,mitaka dont make there pistons correctly and this has cracked in the skirt and caused the exhaust bridge to crack!!!!!!!!!in turn fukin the cylinder!!!" i couldnt beleive my fukin ears..... whats youir take on that,,all opinions more that welcome on this one
any how please give me all your opinions on this.engine in question 2002 cr250(sorry its not a 500 but it is relevant to its prob area)
so we pulled the engine apart and it had the tiniest crack and pealing on the ehaust bridge,nickasil had started to peel at this point but the rest of the cylinder was fine,engine was running satisfactorly...so we order a new mitaka piston kit and send the cylinder and piston away to nz cylinders for a replate with a formal request for extra releif on the bridge,they call me a say they will have to weld the cracked bridge prior to replating which would be certain practice,so we receive the piston and cylinder back,job looks good nicely finished,checked piston clearance and ring gap,all fine,asseble engine,new gaskets etc,start the engine running 32:1 let it gradually warm up,do all checks all is fine run for approx 3 5 mins and turn off and let cool,drain carb and leave engine,come back the next day and turn fuel on and start and run engine to operating temp,put in to gear and drive engine through gears up and down nicely for approx 5 mins,turn engine off let cool and recheck all ancilaries,all is fine,start engine again,sounding crisp,run engine increasing rpm range and speed,going to 2 thirds throttle for a couple of runs..then it rains so we stop the bike and return to the workshop.now my friend texts me you should come and have a look at this piston it doesnt look to good! now i though he wa having me on so i rushed round there,looked up the port,n thought wtf! ther was slight seizing inthe xhaust bridge area,so i pulled the head off and couldnt beleive it was running so mint the nickasil had completly gone and the crack that was welded up was right back ther in the xact same spot???????????? hmmmm i pulled the barrel off and inspected the piston it was scuffed up and groved/fuked in that area a coresponding exhaust bridge groove and seizure on the piston and a vertical crack on the skirt in the same locality...so what would you think????i am a motorcycle mechanic of 17yrs,service manager at the local kawaski dealer ship honda for 10 years bla bla bla,,any how i have used mitaka pistons and have found them to be reputable so far, i have assebled 100s of two strokes and specialise in 500s,i am very aware of the nature of the bridge etc..so apply very stringent critisium to this area when building my engines....my opinion is this quite evidently the xhaust bridge has not been repaired properly,the crack has still been evident beneath the replate and this has quite clearly pronouced itself against the piston causing heat, damage and eventually hairline fracturing in the skirt
the rest of the cylinder and piston is fine..so am not happy as the run in procedure even though not complete was textbook to this point,i call nz cylinders and explain the situ,i send the components back for inspection and wait for there response,this is what i got"we have looked at the piston and cylinder and also called wayne "wobbly" wright(x gp mechanic, and the piston has caused the damage,mitaka dont make there pistons correctly and this has cracked in the skirt and caused the exhaust bridge to crack!!!!!!!!!in turn fukin the cylinder!!!" i couldnt beleive my fukin ears..... whats youir take on that,,all opinions more that welcome on this one
- Roostius_Maximus
- Site Admin
- Posts: 4641
- Joined: November 16th, 2007, 3:24 pm
- Location: Mt Nebo, Manitoba, Canada
- Contact:
sounds like the crack wasnt properly repaired.
ive never used that piston, but Namura works good, like an oem.
we have 2 of those bikes , not big hours on them tho but no cracks on the bridge
ive never used that piston, but Namura works good, like an oem.
we have 2 of those bikes , not big hours on them tho but no cracks on the bridge
http://www.youtube.com/user/500bigbore
My CR500 Tech Reference... http://sdrv.ms/1a0CIiz
MRE Components... http://sdrv.ms/1bs2zhd
My CR500 Tech Reference... http://sdrv.ms/1a0CIiz
MRE Components... http://sdrv.ms/1bs2zhd
-
- Posts: 93
- Joined: January 3rd, 2010, 3:27 pm
- Location: Australia
- glen howell
- Posts: 295
- Joined: July 23rd, 2007, 12:21 am
- Location: ca.
- Contact:
You know Red,That L.A.Sleeve say's not to renaksil or rechrome a 250 they say it's better to sleeve them especially if the bridge has a crack.You most likly could of had a sleeve put in and then it could be bored many times,For what the cost of the welding,machining,replating.Just a thought,That piston should have been fine,I've used several in my builds.Glen
gas is for washing parts, alcohol is for drinking,nitro is for racing
- Roostius_Maximus
- Site Admin
- Posts: 4641
- Joined: November 16th, 2007, 3:24 pm
- Location: Mt Nebo, Manitoba, Canada
- Contact:
some guys came to my track to ride about 1/2 an hour ago, its too wet but the guy was looking for a place to break in his 06 cr250, said he just got a new jug after cracking the bridge
and id never heard of it before
said he has had lots of riding on it, but recently changed to running strait u4.4 in the bike instead of mixed 1/2 with premium. he'd jetted up 2 sizes from stock for his mix and went to strait without a jet change, figures thats what ate it up. piston looked good. fmf gnarly pipe and silencer, otherwise stock bike and oem piston. bought a new jug from (i think he said honda of troy) instead of waiting for a replated one
and id never heard of it before
said he has had lots of riding on it, but recently changed to running strait u4.4 in the bike instead of mixed 1/2 with premium. he'd jetted up 2 sizes from stock for his mix and went to strait without a jet change, figures thats what ate it up. piston looked good. fmf gnarly pipe and silencer, otherwise stock bike and oem piston. bought a new jug from (i think he said honda of troy) instead of waiting for a replated one
http://www.youtube.com/user/500bigbore
My CR500 Tech Reference... http://sdrv.ms/1a0CIiz
MRE Components... http://sdrv.ms/1bs2zhd
My CR500 Tech Reference... http://sdrv.ms/1a0CIiz
MRE Components... http://sdrv.ms/1bs2zhd
-
- Posts: 93
- Joined: January 3rd, 2010, 3:27 pm
- Location: Australia
yeah i agree glen i really do and was contemplating the sleeve prior to the replate,do to the flexability of rebores,cheers for your comments it cements what i already beleive....thing is though for the application the replate has been more that satisfactory in the past,my grumble is the bollocks they are trying to pass off as reason for the failure when it is staring you in the face!!! fair enough if i had done an hour on it then rung the fuk out of it for 800meters or so,i may of been able to adhear to there excuse,however after max 10,15 mins of baby break in procedure...cheers for hearing me out guys..oh yeah as for the piston,i have had no probs with them UNTIL now!! funny that...
cheers for the feed back roostius,appreiciated...
cheers for the feed back roostius,appreiciated...
-
- Posts: 93
- Joined: January 3rd, 2010, 3:27 pm
- Location: Australia
some more info for you,my freind whos engine this is,he is a aluminium stainless fabricator and welder,its all he does,i showed him what they claimed to have done,he commented,i dont understand if it had been welded properly,it would not have cracked in exactly the same place,he said if it was to crack again it should more likely to be beside the repair,said it was strange!!....
-
- Posts: 4394
- Joined: July 4th, 2007, 6:57 pm
-
- Posts: 93
- Joined: January 3rd, 2010, 3:27 pm
- Location: Australia
- Rosco-Peeko
- Posts: 823
- Joined: June 1st, 2007, 2:47 pm
-
- Posts: 4394
- Joined: July 4th, 2007, 6:57 pm
- glen howell
- Posts: 295
- Joined: July 23rd, 2007, 12:21 am
- Location: ca.
- Contact:
-
- Posts: 93
- Joined: January 3rd, 2010, 3:27 pm
- Location: Australia
just for the few watching this,i spoke with them at length toady about this prob,some of senarios the chap came out with actually had me laughing out loud after id finished,however after politely shutting down any excuse he had,he agreed to replate the cylinder! we still have to fork out for another piston kit etc,summiseing he never admited to the fault,never gave substansaited reason for the failure,but maintained it was not the bridge but the piston causing the failure! but then he decides to replate iy any way...me, i just cut the shit and get on with it,talking smack about this that and whoever said,fuk! staring you in the face pal,fuk youd hope he better not miss his missis crack like that eh!!!well up the bum no babies i suppose!! cheers guys...
-
- Posts: 4394
- Joined: July 4th, 2007, 6:57 pm
- 2strokeforever
- Posts: 1524
- Joined: November 13th, 2009, 1:04 pm
- Location: Vernon B.C Canada
02+ id be careful of honda pistonshonda piston is $67. never had a issue with mine
dont know about the 02 cr250 but the 02 125 piston was sized wrong from honda... i was dumb enough to buy 2 before measuring clearance... 7 thou brand new!!!!!!!!!!!!!!!!!!! on a 125 cylinder was in spec and not worn, ended up going with a pro x rm 125 piston which needed the head cut 1.5mm deeper because of 1.5mm taller, made the port timing better, more low mid, and didnt lose any top( at least i couldnt tell if it did) but the 125 came with messed up port timing stock
the 450 will have less power and will be harder to start, and will be heavier, but to make up for it it will require more maintenance.
4stroke=dead fish
4stroke=dead fish