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georgie
13th January 2008, 15:37
Hi all,
So, I've had my rg150 for a few months now, and after reading all that I could about them on here I decided that checking the power valves was a good thing to do (one is totally toasted, but payday is still a a week away:(). While i had the thing in pieces i decided to check the piston as well... so, question time..
Pic1... Is this bad? (or should i say, how bad is this?)
pic2... whats this wibbly bit that was under the ring?
pic3... does this pin bit look ok?

also, are the rings meant to be able to move around the piston? if they are, what are the pins in the ring grooves on the piston meant to do? :confused:

Lots of questions sorry! But I am a recent convert to 2 wheeled transportation, so all help muchly appreciated

georgie
13th January 2008, 16:24
Also.... the manual that I downloaded shows a picture of the piston being de-carboned by the crown being scraped. This the best way to do it? Oh and, I know what the wibbly bit in pic 2 is now ( read the manual properly georgie!!)

quallman1234
13th January 2008, 16:37
Pistion Doesn't look too bad. If the second picture is the rings then that looks shocking.

When you put it back in dont forget to buy new circlips! (Never use circlips twice) Only like 20c each.

georgie
13th January 2008, 16:45
haha, nope, pic 2 is something that was under the lower ring. Looking at the manual, I think it is an expander ring? maybe? Will be sure to get new circ clips before it all goes back together.

xwhatsit
13th January 2008, 19:41
Is the piston supposed to be so scuffed up like that? Did it seize? It looks nasty, but I have no idea about these things.

Ixion
13th January 2008, 19:44
Seen worse. Much worse. Fair bit of blow by, but. Y' might want to think about a new set of rings.

xwhatsit
13th January 2008, 19:48
Blow-by? Is that scuffing caused by combustion gas?

Nasty
13th January 2008, 19:51
to quote AJTurbo .... "its pharked" :doh::doh:

georgie
13th January 2008, 20:15
Is the piston supposed to be so scuffed up like that? Did it seize? It looks nasty, but I have no idea about these things.
Freaked me out a bit when i pulled it out too. he hasnt seized since i got him, but I'd guess he has in the past :(


Seen worse. Much worse. Fair bit of blow by, but. Y' might want to think about a new set of rings.
That makes me feel MUCH better :)


to quote AJTurbo .... "its pharked" :doh::doh:

This makes me feel Much worse!! :laugh: Ah well, at least I'm learning a lot as i go. I am definitely getting addicted to my busted up little 2 stroke:love:

quallman1234
13th January 2008, 21:48
Get a set of rings def.

Pistion should be fine as long as your not fanging it too much.

Like ixion said i too have seen way worse what have been quote "fine to run".

I reckon she'll be alright unless your racing then i would get a new pistion kit.

georgie
13th January 2008, 21:58
Wicked. New set of rings it shall be :)... And definitely no racing for me.. yet.. hehe

One other thing, how can I tell if the bearing at the other end of the conrod is OK? what sort of tolerance should there be for side to side movement?

Thanks for the replies, you guys rock :clap: I will have to figure out how to do that bling thing :)

Ixion
13th January 2008, 22:01
Big end bearing it's called (cos it's the big end of the conrod - unimaginative lot engineers), a bit of pure side to side is usually OK, a millimetre or two - some very high tuned engines are fussy but an RG150 should be OK for a mm or so. But absolutely NO up and down movement at all. Ideally no rock from side to side at the little end either, but a lot of engines allow some tolerance for this

dangerous
13th January 2008, 22:18
Pic1... Is this bad? (or should i say, how bad is this?)
pic2... whats this wibbly bit that was under the ring?
pic3... does this pin bit look ok?

4) also, are the rings meant to be able to move around the piston? if they are, what are the pins in the ring grooves on the piston meant to do? :confused:


1) yes, dont care what the others say but thats a defnit sieze could be a cold sieze common as is that same mark on all 4 corners of the piston (4 point sieze) replace it Check the bore for corosponding damage.

2) that belongs behind the ring, it helps keep the ring out against the bore wall replace it (comes with ring kit)

3) replace it it will come with a piston kit as will the rings, circlips should also be in a kit depending on brand.

4) The rings should not rotate the wee pin should stop this, but to test you will need to compress the ring. If the rigng rotates on the piston it can and will get cought up in a port riping the top of the piston off.

koba
17th January 2008, 11:50
1) yes, dont care what the others say but thats a defnit sieze could be a cold sieze common as is that same mark on all 4 corners of the piston (4 point sieze) replace it Check the bore for corosponding damage.

2) that belongs behind the ring, it helps keep the ring out against the bore wall replace it (comes with ring kit)

3) replace it it will come with a piston kit as will the rings, circlips should also be in a kit depending on brand.

4) The rings should not rotate the wee pin should stop this, but to test you will need to compress the ring. If the rigng rotates on the piston it can and will get cought up in a port riping the top of the piston off.

I second that.
A piston kit aint cheap but its gunna be a shit if you have to pull the whole thing apart again in a week!
A bike with everything running nicley is happy and rewarding, it really is worth doing that piston!

Also check the bore, if you have the right manual it will tell you how to.

FruitLooPs
18th January 2008, 00:11
Thirded, mine was rooted with a piston that wasn't as bad as that, although I had a tiny wee bit of a squashed ring land. After the piston was taken off a thorough looking over found a hairline crack in the inside of the skirt too, too much of a chance to take IMO. If the power valves were stuffed you shouldn't go halfway, fix it up good. Then again it might be dandy..

If you ask Oyster for his opinion I'm sure he could show you 3 or 4 more RG pistons that look nearly the same and tell you just whats happened and if you should replace or not. Methinks replace though.

Check bore etc, that first pic fullsize looks like it has some gouging on the side of the piston, might just be carbon though. :crazy:Piston kit and rings are reasonably inexpensive when you consider it could grenade/collapse and screw the bore and spit crap into the crank etc.

Use good synth oil etc, usual 2 stroke advice.

*edit*
I'm in a good mood so I grabbed my old piston and took pics of all the bits so you can see and compare. Also note the vertical scuffing bright marks, that was in my case from a shot powervalve grinding away. No idea what that random hex bit was, its not on my piston assembly (well not how it was returned anyhow) - you should have piston, pin circlips, rings, roller bearing and wrist pin so far as I can tell. 82815

The general scuffing on your piston appears to be quite a bit deeper than mine though, might just be the pic though.

FilthyLuka
18th January 2008, 09:13
Get a new piston, they're not expensive. its $90 for a piston kit.

But like Ixion said, there's been worse. Clean it up with a bit of sand paper and whip her back in if your a tad on the cheap side

koba
18th January 2008, 09:19
Get a new piston, they're not expensive. its $90 for a piston kit.

But like Ixion said, there's been worse. Clean it up with a bit of sand paper and whip her back in if your a tad on the cheap side

jeeze man, where can ya get 'em that cheap?:shit:
Im in if you can...

quallman1234
18th January 2008, 11:11
jeeze man, where can ya get 'em that cheap?:shit:
Im in if you can...

+1 :shit:

10 Char

Billy
18th January 2008, 11:27
You cant.That would be piston only and just under cost price.That bike definitely needs a new piston,rings and gudgeon.Iwould also suggest you replace the little end bearing as well as the engine has partially seized probably due to powervalve failure.The blowby mentioned earlier in the thread is actually a teflon coating and is meant to be there and the ring shown is the expander ring that goes under the bottom ring.There was a piston kit on trade me @ $175.00 with reserve met.Also with regards to the powervalve failure you can replace the powervalves with blanks and never have to worry about them ever again,You will however have to go through some jetting changes but its well worthwhile at the end of the day.You will lose some lower end power(below about 7500) but if youre racing this bike its 9000 or upwards or you might as well stay at home.If you want some powervalve blanks made up PM me and I will put you in touch with the engineer that did my bike.Cheers Billy

georgie
19th January 2008, 18:22
Thanks for all the info guys (I'm feeling all knowledgeble now:yes:). I'm going price up all the bits and see how the budget looks :2thumbsup Ideally I'll sort it all out at the same time. will let you know how it all goes.

dangerous
19th January 2008, 19:50
Thanks for all the info guys (I'm feeling all knowledgeble now:yes:). I'm going price up all the bits and see how the budget looks :2thumbsup Ideally I'll sort it all out at the same time. will let you know how it all goes.

Can sort you out a piston kit for $180 plus P&P, let me know how that compairs with other pricing.




Get a new piston, they're not expensive. its $90 for a piston kit.
ummm where abouts please, cos Im not sure you are right there.

FilthyLuka
20th January 2008, 13:07
Can sort you out a piston kit for $180 plus P&P, let me know how that compairs with other pricing.




ummm where abouts please, cos Im not sure you are right there.

turns out i was :shutup:

seems i was off by $90, heh

http://www.motorbikeparts.co.nz/product_details.php?category_id=2&sub_category_id=3&product_id=288

dangerous
20th January 2008, 15:55
turns out i was :shutup:

seems i was off by $90, heh

http://www.motorbikeparts.co.nz/product_details.php?category_id=2&sub_category_id=3&product_id=288

Good on ya... thats the site we need to check out, Ill get the man for ya stay there...

MDR2
23rd January 2008, 17:12
Not to steal the lime light or anything but...

Guess who's power valves had a tea party with their piston.

....Yay

georgie
23rd January 2008, 17:16
Not to steal the lime light or anything but...

Guess who's power valves had a tea party with their piston.

....Yay

ouchie :(

tommorth
23rd January 2008, 18:48
bugga how bout a pic of the bits that got friendly

MDR2
23rd January 2008, 20:24
Maybe when I next go in to see the mechanic.

Damn I have a knack for buying lemons.

koba
23rd January 2008, 20:46
Maybe when I next go in to see the mechanic.

Damn I have a knack for buying lemons.

Fark, if you wanna get rid of it...

MDR2
24th January 2008, 08:14
im in it for the long haul :)

As soon as I get it back it gets shipped down to Dunedin.

Going to terrorize the locals and the sheep for a few years.