Dt 125 R engine mixed parts?
-
@Hybrid_Theory01 The 3BN head is restrictive and has a combustion ring in the squish. A 3MB head can be sourced and is an upgrade, later models ran them.
Very early models ran a 3BN cylinder which has a slightly larger bore IIRC. But yes all looks normal.
@Calum thank you for that information, might do the upgrade in the future
-
@Hybrid_Theory01 The 3BN head is restrictive and has a combustion ring in the squish. A 3MB head can be sourced and is an upgrade, later models ran them.
Very early models ran a 3BN cylinder which has a slightly larger bore IIRC. But yes all looks normal.
-
Why do people think that the 3bn head is restricted? When I did a cc capacity test it was higher compression than the 3mb. The ring might actually help swirl...
@SpookDog it's not the swirl, it's the fact it disrupts the propagation of the combustion flame which slows down the burn which reduces the effectiveness of the explosions effect on pushing the piston downwards.
Ideally you want the entire air gas mixture to spontaneously combust at the same time to maximise the downward force generated on the piston crown at TDC. Unfortunately that isn't real life, so the fuel air is ignited before TDC to allow the flame to propagate appropriately and act downwards as the piston descend towards BDC. Any force acting down as the piston is approaching TDC is knock and will destroy your engine. So it's a fine balance.
If that ring were "performance" then you'd see them in race engines and the like.
-
@SpookDog it's not the swirl, it's the fact it disrupts the propagation of the combustion flame which slows down the burn which reduces the effectiveness of the explosions effect on pushing the piston downwards.
Ideally you want the entire air gas mixture to spontaneously combust at the same time to maximise the downward force generated on the piston crown at TDC. Unfortunately that isn't real life, so the fuel air is ignited before TDC to allow the flame to propagate appropriately and act downwards as the piston descend towards BDC. Any force acting down as the piston is approaching TDC is knock and will destroy your engine. So it's a fine balance.
If that ring were "performance" then you'd see them in race engines and the like.
Alright, not swirl. I’m not versed in the dark arts of 2stroke. But isn’t a squish band there to promote a clean/even burn with no hot or cold spots? By keeping the mixture ‘moving’ in the chamber?
I’m just not convinced it’s a form of restriction, There were 3bn head bikes sold in non 12bhp non-restricted countries, no? There have to be less arcane ways of restricting 2strokes?
I’m not saying you’re wrong
I just don’t ‘see it’ -
Alright, not swirl. I’m not versed in the dark arts of 2stroke. But isn’t a squish band there to promote a clean/even burn with no hot or cold spots? By keeping the mixture ‘moving’ in the chamber?
I’m just not convinced it’s a form of restriction, There were 3bn head bikes sold in non 12bhp non-restricted countries, no? There have to be less arcane ways of restricting 2strokes?
I’m not saying you’re wrong I just don’t ‘see it’@SpookDog Well, as I say, if it was the best thing then you would see it in competition engines.
On two strokes, the head is where 75% of the power is made/lost. So ensuring this is the best it can be is essential.
Chap on here had his 3BN sent to Mick Abbey.
I am sure if Mick thought that the factory combustion ring was a good thing he'd have left it in there to maximise performance.
-
@SpookDog Well, as I say, if it was the best thing then you would see it in competition engines.
On two strokes, the head is where 75% of the power is made/lost. So ensuring this is the best it can be is essential.
Chap on here had his 3BN sent to Mick Abbey.
I am sure if Mick thought that the factory combustion ring was a good thing he'd have left it in there to maximise performance.
I’m not saying it’s the best or performance enhancing. I’m just not convinced it’s a form of restriction. Especially when it has a higher compression ratio than a 3mb. I mean there’s no discernible difference between running the two performance wise.
I don’t know what Yamaha were thinking, I just don’t think it was restriction. Far easier cheaper to produce, ways.. -
I’m not saying it’s the best or performance enhancing. I’m just not convinced it’s a form of restriction. Especially when it has a higher compression ratio than a 3mb. I mean there’s no discernible difference between running the two performance wise.
I don’t know what Yamaha were thinking, I just don’t think it was restriction. Far easier cheaper to produce, ways..@SpookDog Sure, to clarify what I'm saying, the head is restrictive and there is noticeable benefits to swapping over to a 3MB head, many have done this and noticed gains. The head can be reworked for a nominal fee and you'll gain more performance and even more than the 3MB if done correctly.
Always Originate, Never Pirate!
-
@SpookDog Sure, to clarify what I'm saying, the head is restrictive and there is noticeable benefits to swapping over to a 3MB head, many have done this and noticed gains. The head can be reworked for a nominal fee and you'll gain more performance and even more than the 3MB if done correctly.
The 3BN has the same combustion chamber with the 2RH head and is not considered restrictive for the TZR 2RH engine. I have all the heads, I think the design is for lower octane fuel,the early early tzr and early dt's required regular gasoline which is 87 octane.
I need my tools and a pile of junk.....
-
The 3BN has the same combustion chamber with the 2RH head and is not considered restrictive for the TZR 2RH engine. I have all the heads, I think the design is for lower octane fuel,the early early tzr and early dt's required regular gasoline which is 87 octane.
-
@MadGyver Sure, I can't remember which it is, either the TZR 2RK or 2RH but one of those is woefully underpowered. So probably isn't a good example.
@Calum All the parts that are inside in my DTR engine are from a 2RH engine that was fitted on a DT LC,in bad condition but was ripping. The 2RK don't think ever came here in Greece. In 80's and 90's everything was imported full power or side imports to have full power model's.With the EU came the restrictions.
I need my tools and a pile of junk.....
-
@Calum All the parts that are inside in my DTR engine are from a 2RH engine that was fitted on a DT LC,in bad condition but was ripping. The 2RK don't think ever came here in Greece. In 80's and 90's everything was imported full power or side imports to have full power model's.With the EU came the restrictions.
@MadGyver I have the 3BN head on a 16.9 KW bike
