RG150 Loud rattle after new piston

[Sketchy_Racer]

ooooooooOOOohh... Thats not a piston knocking..

I would suggest you pull the barel off (dont take the head off, saves a head gasket) and check for any free play. Unfortunatly I think the guy could be right about it being a big end or a main bearing

[tommorth]

it sounds sick id do what Sketchy_Racer says
you didnt drop somthing down the plug hole?

[FruitLooPs]

It sounds to me like you have the same problem Magua had with his bike, thats his in the clip I posted up earlier.

here is his thread about his bike, it's pretty old but might provide some insight.

http://www.kiwibiker.co.nz/forums/sh...ighlight=rg150


On another note, just got my RG sorted once again - one pvalve was stuffed, new tyre chain and rear pad. Mm was fun on the port hills though

*edit* a quick scroll through his thread, yeah his big end was shot and crank etc. Hope thats not the case for you, but it sure does sound like it to me

[Jase W]

ooooooooOOOohh... Thats not a piston knocking..

I would suggest you pull the barel off (dont take the head off, saves a head gasket) and check for any free play. Unfortunatly I think the guy could be right about it being a big end or a main bearing

How much play am I looking for, and in which direction (I assume moving the rod side-side to see how much it moves?).

I was pretty careful, made sure that it was all covered so that nothing could fall in, if there happened to be any loose bits around (ie piston circlips).

[oyster]

In a GP bike like an RS 125 the big end has a life of around 3000km.
You expect that, 45hp and 12000rpm all day. On an Rg its still 12000rpm but only 60% of the power, but this means RG's have a big life that's still quite short. For racing probably 6000km, on the road 15000km. All depends on oil quality, condesation ingress (very common) and the thrash factor.
On a race Rg a big end goes from quiet and performing perfectly to complete blow up in a tenth of a second. On the road often they die slowly and I've seen (and heard) plenty on the way out. Of course a good thrash up the motorway or tack and it'll go bang big time. Will wreck casings, barrell, the lot.

To check the big end the easy way take the exhaust off and the alt cover. Turn the crank back and forth and if you can detect the the crank moving but (momentarily) the piston not. (Look up the exhaust port).
The full check means barrel off and very carefully feel for radial movement.
Axial no problem, factory setting 0.4 from memory
Any more that 0.02mm radial can be felt, and if it's there, it's stuffed.

Only answer is new big end.

[Jase W]

Cheers for that mate. When the weather fines up i'll give it a go. When I had it apart for the piston, there was a tiny amount of side-to-side movement (Axial?). Probably within the tolerance you have specified there. Im pretty sure there was bugger all (if any) play when rotating the crank (Radial?). Of course I wasnt actually checking anything so chances are there was a bit of play and I didnt notice it.

Is it worth trying to do a big end myself (for the learning factor etc), or is it one of those jobs that is better to let the professionals handle, or should I just replace the whole engine (anyone got a good one for sale?)?

Thanks again to everyone that is helping me without actually seeing the bike!!

[Jase W]

Ok i've just a had a look up the exhaust port while turning the kickstart (dont think it matters if I do it this way?), there is definently no delay before the piston moves once there is resistance in the kick lever. I did notice some faint vertical scratching on the side of the piston though... dunno if that matters.

Is there anyone in the wellington area with experience that could come around and have a listen/play? My video does get the general gist of it across but I guess its always easier to diagnose in person...

[ajturbo]

think you should be asking sketchy....

[Jase W]

Im going to pull the engine out tomorrow as its going to need to be pulled apart anyway. Maybe once I have the barrel off there may be some more clues as to what the noise is.

[Spuds1234]

Sounds like my gs250 when it shat a big end bearing.

Apart from that Im no mechanic so I dont know shit.

[ajturbo]

Im going to pull the engine out tomorrow as its going to need to be pulled apart anyway. Maybe once I have the barrel off there may be some more clues as to what the noise is.

hey... when you have pull all apart, give me a call..
0274 595830....
i'll see where i am and could pop over... and stand there strocking my chin and saying ..
hymmmmmmmmmmm....
Oooo look there is that thingy bit!
where's ya beer?
now THAT doesn't look good... but ya sister does!... (hope she looks good!)
well.. at least your tyres are black... not like some of the trail bikes that i have seen that are yellow/blue/orange..ghey...
and ...

[Jase W]

lol ok ill keep that in mind mate, cheers.

Right now I need to find something suitable to insert through the swingarm pivot to stop it all collapsing when I pull the bolt for the rear mount.

[Gubb]

Will your cock do?

[roadracingoldfart]

I dont like the sound that engine makes at all.
Did you check the gudgin pin was the same diameter as the rod end and the same as the piston pin diameter ????
If they are ok i think a big end has just gotten bigger

[Ixion]

Um, I know this is a REALLY silly question, and please don't be offended, but you *did* put the little end in, didn't you ? Just I know someone once forgot it ! (No it was NOT me !)