My gn125 is a 1997 it has the Dr type head, that uses the double lump piston, I used a domed bbk and the piston was hitting the head, I used 2 base gaskets and custom copper head gasket between the 2 super think head gaskets that come with the bbk kit , runs fantastic now top speed 70mph, think I broke it in with heat cycles then 150 miles at 6k rpm max. No issues starts and runs fantastic, I also fitted oil cooling radiator that works great too. Nice video man 👍👌
Cool to hear, yeah just after this video I tried some pistons and some putty in the head (without cam for now) to see what sort of squish would happen in the combustion chamber. The low dome piston left 10mm clearance to the valve at tdc. But the high dome will hit the head. With 1 base gasket and the thin 150 kit head gasket, the head still needs to be spaced up about 4mm to avoid the piston hitting it. So I'm not sure what they think the high domed piston is supposed to fit, you could use it with a lt185 or dr200 head, but they are really too big for a 62mm piston. I might have a cylinder base gasket spacer plate cut, maybe 3mm aluminium with 2 base gaskets, it would be a good solution similar to your headgasket. For now I will run the low dome piston and see how it goes with the hotcam in terms of clearance. Long term I want to bore the cylinder out further and use a different conrod for more piston choice
@@tortron from what was happening with mine was, I think a ring right around the outer piston and one spot on the side of the piston, There's a guy called Raymony88 on TH-cam helped me figure what was going on, I had good valve clearance I used bluetack to check, it was a head ache but got there, think I have some pics of where it was hitting I'll make a video of them after work and upload it, I hope you can get it sorted in using dr200 can also the GN is running awesome at the moment .
@@upsidedown1986 Yup there's Definately a 3mm or so ring that is hitting. A quick cut in a mill would be a good way to fix that actually, but I'm interested is where you had the other spot hitting, I didn't notice that on mine
@@tortron I uploaded a short made from photos, Yiu can see where the piston was hitting the head there's a clean silver ring around the piston and the exact mark of the head on the piston if you go over to my channel you'll see the marks on the head and piston 👍
Hi man, done almost 500 mile trip this weekend, no problems I didn't find on some longer hills the speed did drop off some times to 55 mph, I did hit 75mph on slightly long down hill part of the motorway... Great bike very impressed, I have to figure out a way to keep the speed up while going up hill then it will be perfect. Any ideas on that?
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My gn125 is a 1997 it has the Dr type head, that uses the double lump piston, I used a domed bbk and the piston was hitting the head, I used 2 base gaskets and custom copper head gasket between the 2 super think head gaskets that come with the bbk kit , runs fantastic now top speed 70mph, think I broke it in with heat cycles then 150 miles at 6k rpm max. No issues starts and runs fantastic, I also fitted oil cooling radiator that works great too. Nice video man 👍👌
Cool to hear, yeah just after this video I tried some pistons and some putty in the head (without cam for now) to see what sort of squish would happen in the combustion chamber. The low dome piston left 10mm clearance to the valve at tdc. But the high dome will hit the head. With 1 base gasket and the thin 150 kit head gasket, the head still needs to be spaced up about 4mm to avoid the piston hitting it. So I'm not sure what they think the high domed piston is supposed to fit, you could use it with a lt185 or dr200 head, but they are really too big for a 62mm piston. I might have a cylinder base gasket spacer plate cut, maybe 3mm aluminium with 2 base gaskets, it would be a good solution similar to your headgasket. For now I will run the low dome piston and see how it goes with the hotcam in terms of clearance. Long term I want to bore the cylinder out further and use a different conrod for more piston choice
@@tortron from what was happening with mine was, I think a ring right around the outer piston and one spot on the side of the piston, There's a guy called Raymony88 on TH-cam helped me figure what was going on, I had good valve clearance I used bluetack to check, it was a head ache but got there, think I have some pics of where it was hitting I'll make a video of them after work and upload it, I hope you can get it sorted in using dr200 can also the GN is running awesome at the moment .
@@upsidedown1986 Yup there's Definately a 3mm or so ring that is hitting. A quick cut in a mill would be a good way to fix that actually, but I'm interested is where you had the other spot hitting, I didn't notice that on mine
@@tortron I uploaded a short made from photos, Yiu can see where the piston was hitting the head there's a clean silver ring around the piston and the exact mark of the head on the piston if you go over to my channel you'll see the marks on the head and piston 👍
Hi man, done almost 500 mile trip this weekend, no problems I didn't find on some longer hills the speed did drop off some times to 55 mph, I did hit 75mph on slightly long down hill part of the motorway... Great bike very impressed, I have to figure out a way to keep the speed up while going up hill then it will be perfect. Any ideas on that?
Md90 piston rings