Post by Nismosis on Oct 19, 2012 9:10:55 GMT 1
Hello Chaps,
Right… Where do I start…………..
It all started a good few weeks back when I was riding my recently purchased RD125LC, it just seemed to lack top end grunt and was getting very hot. The temperature gauge was sitting at ¾ and over under normal running and I was getting concerned that it may seize or cause major engine damage.
Once back in the garage I notice oil residue leaking from the underside of the exhaust where it bolts to the barrel, I though to myself “ahhh haaaaa the exhaust gasket is leaking and could explain my lack of power”.
I removed the exhaust and the gasket looked very old and charred and needed replacing. With the exhaust off I had a quick look up the exhaust port expecting to see a nice shiny piston, How wrong I was……… I was confronted with a manky looking piston that had divorced its top piston ring
I couldn’t believe what I was looking at, I was totally amazed at how the engine managed to haul my 15 stone butt along the road. I was gutted to say the least.
Once the dust had settled and I had calmed down, rational thoughts came back into my head… It was time for a top end rebuild….
I started stripping the top of the engine down and was confronted with a few more horrors and the reason my engine was overheating.
They say pictures speak a thousand words…………
The Mellon who put this engine back together must have had shares in Instant Gasket!!!! Some people just shouldn’t be let loose with a spanner set!
Anyway, the head was showing signs of detonation and you could see the argument it had with the top piston ring. After showing a few people the piston it was obvious that the top ring had been missing for some time, judging by the burn marks on the piston. The bike rode like this when I bought it and it wasn’t something that just ‘happened’ whilst I was riding it. As this was my first RD125LC I had nothing to compare it too and just assumed that was all the power they produced. It was only when a good friend who has owned many RD’s took it for a ride and said it was low on power and knocking like a woodpecker. I realized something was wrong…..
In the defence of the guy I bought it off, he hadn’t actually done any work on the engine since owning it.
I took the barrel and head to Sutton Rebore (Mike who owns it is a good friend of the family) and I asked Mike to rebore the barrel and supply a new piston kit to suit. I also wanted to get the head and barrel powdercoated in satin black as the paint was starting to flake.
After a few weeks I got the bits back and I was very excited to get them fitted…
After 2 hours in the garage I had the bike back together and ready for the nervous ‘first kick’….. Will it start…… Will it leak….. Have I remembered everything……
It had mental amounts of compression compared to before and I was feeling pretty confident…. Nothing on the first kick……. Deep breath…… Second kick and barooooooommmmmmmmm she fired up filling my garage with a cloud of 2 stroke smoke
She just ticked over and purred like a kitten, the engine was so quiet, no knocking or whining, just the crackle from the exhaust. I was delighted and couldn’t believe how easy it was to work on these bikes. My only concern was will it start leaking from the head, maybe the mellon who built the engine put that much instant gasket on for a reason…… No leaks, lots of compression and a very smooth running engine….
I’ve done about 30 miles on the bike since the rebuild at sub 6000rpm and its brilliant. It doesn’t overheat any more and seems to be a lot more rideable below 6000 rpm. No leaks so far and the coolant in the expansion tank is still bang on the F mark.
I’m looking forward to getting around 100 miles on her so I can go above 6000rpm and start to feel the real difference……… ;D
Right… Where do I start…………..
It all started a good few weeks back when I was riding my recently purchased RD125LC, it just seemed to lack top end grunt and was getting very hot. The temperature gauge was sitting at ¾ and over under normal running and I was getting concerned that it may seize or cause major engine damage.
Once back in the garage I notice oil residue leaking from the underside of the exhaust where it bolts to the barrel, I though to myself “ahhh haaaaa the exhaust gasket is leaking and could explain my lack of power”.
I removed the exhaust and the gasket looked very old and charred and needed replacing. With the exhaust off I had a quick look up the exhaust port expecting to see a nice shiny piston, How wrong I was……… I was confronted with a manky looking piston that had divorced its top piston ring
I couldn’t believe what I was looking at, I was totally amazed at how the engine managed to haul my 15 stone butt along the road. I was gutted to say the least.
Once the dust had settled and I had calmed down, rational thoughts came back into my head… It was time for a top end rebuild….
I started stripping the top of the engine down and was confronted with a few more horrors and the reason my engine was overheating.
They say pictures speak a thousand words…………
The Mellon who put this engine back together must have had shares in Instant Gasket!!!! Some people just shouldn’t be let loose with a spanner set!
Anyway, the head was showing signs of detonation and you could see the argument it had with the top piston ring. After showing a few people the piston it was obvious that the top ring had been missing for some time, judging by the burn marks on the piston. The bike rode like this when I bought it and it wasn’t something that just ‘happened’ whilst I was riding it. As this was my first RD125LC I had nothing to compare it too and just assumed that was all the power they produced. It was only when a good friend who has owned many RD’s took it for a ride and said it was low on power and knocking like a woodpecker. I realized something was wrong…..
In the defence of the guy I bought it off, he hadn’t actually done any work on the engine since owning it.
I took the barrel and head to Sutton Rebore (Mike who owns it is a good friend of the family) and I asked Mike to rebore the barrel and supply a new piston kit to suit. I also wanted to get the head and barrel powdercoated in satin black as the paint was starting to flake.
After a few weeks I got the bits back and I was very excited to get them fitted…
After 2 hours in the garage I had the bike back together and ready for the nervous ‘first kick’….. Will it start…… Will it leak….. Have I remembered everything……
It had mental amounts of compression compared to before and I was feeling pretty confident…. Nothing on the first kick……. Deep breath…… Second kick and barooooooommmmmmmmm she fired up filling my garage with a cloud of 2 stroke smoke
She just ticked over and purred like a kitten, the engine was so quiet, no knocking or whining, just the crackle from the exhaust. I was delighted and couldn’t believe how easy it was to work on these bikes. My only concern was will it start leaking from the head, maybe the mellon who built the engine put that much instant gasket on for a reason…… No leaks, lots of compression and a very smooth running engine….
I’ve done about 30 miles on the bike since the rebuild at sub 6000rpm and its brilliant. It doesn’t overheat any more and seems to be a lot more rideable below 6000 rpm. No leaks so far and the coolant in the expansion tank is still bang on the F mark.
I’m looking forward to getting around 100 miles on her so I can go above 6000rpm and start to feel the real difference……… ;D
