Thoughts on this billet head
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I was looking for parts for my supermoto conversion, and came across a site that sells a customized billet head for the dt125r with customized squishband area. Would the power gain be worth the 240€, or will it just make it less reliable?
Link for the billet head =
https://www.jlmotorsport.pt/products/BILLET125DTWR -
I was looking for parts for my supermoto conversion, and came across a site that sells a customized billet head for the dt125r with customized squishband area. Would the power gain be worth the 240€, or will it just make it less reliable?
Link for the billet head =
https://www.jlmotorsport.pt/products/BILLET125DTWR@YYHpilo Oh that is so fricken cool!
So two strokes make an awful lot of power just in the head alone.
I'd say the money is expensive and the best way to get performance out of your cylinder is to have the head ported to your setup (piston etc).
But I'd buy this if I were still tuning DTRs. That's a lovely bit of kit!
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I was looking for parts for my supermoto conversion, and came across a site that sells a customized billet head for the dt125r with customized squishband area. Would the power gain be worth the 240€, or will it just make it less reliable?
Link for the billet head =
https://www.jlmotorsport.pt/products/BILLET125DTWR@YYHpilo It's a lovely piece of machining and I like the O-ring sealing but I'm not sure about omitting the thermostat. As well as regulating coolant temperature, the idea IIRC is to keep the coolant in the actual water jacket around the cylinder and head under higher pressure than the rest of the system to increase its boiling point. Even some competition bikes which don't run thermostats have restrictor plates at the outlet on top of the cylinder head to achieve this. The website says the DTR thermostat is prone to sticking; I've never had that happen on any DTR, including the one I owned for two years/30,000+ miles as a teenager. I did 3 or 4 top end rebuilds on that bike before selling it to a friend who did another few thousand miles before passing his test and getting a bigger bike, and neither of us ever touched the thermostat. I think this happens because people don't replace their coolant often enough or with the correct grade TBH. Or they just use water judging by the rust inside some of the secondhand barrels/heads I've bought in the past.
Also not sure why they'd supply stainless (not to be used in load-bearing applications) bolts for fixing the head to the cylinder; every time you take off the head (possibly to try a different squish shape according to track conditions etc. as the head is marketed as being "for tuners, not for people who don't know what they're doing") the threads in the cylinder will become a little more worn ultimately leading to failure. Incidentally the torque wrench setting for the cylinder/head studs is 13Nm whilst for the cylinder head nuts this is 22Nm (and 28Nm for the barrel nuts); the idea here is, the combination of long thread engagement, low (stud) torque value and being relatively undisturbed ensures long life for the threads in the cylinder and cases which are expensive. Surely supplying their own cylinder studs the correct length isn't beyond the wit of anyone capable of producing something as beautiful as that?
I have to say I don't go much on this guy; the upswept stainless expansion chamber appears to attach directly to the frame (which guarantees it will crack from vibration as the rubber vibration damper isn't present in the photos) and the Supermoto front caliper bracket looks a bit flimsy to me. Considering larger front disc rotor = increased braking forces, I'd want this to be at least as thick/beefy as the caliper mounting lugs on the fork slider. He's clearly good at machining and can in all probability use the two-stroke tuning equations to make an expansion chamber of the correct dimensions but beyond that, he seems to be of the rather dangerous mindset that no-one (including Yamaha) can tell him anything.
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@YYHpilo It's a lovely piece of machining and I like the O-ring sealing but I'm not sure about omitting the thermostat. As well as regulating coolant temperature, the idea IIRC is to keep the coolant in the actual water jacket around the cylinder and head under higher pressure than the rest of the system to increase its boiling point. Even some competition bikes which don't run thermostats have restrictor plates at the outlet on top of the cylinder head to achieve this. The website says the DTR thermostat is prone to sticking; I've never had that happen on any DTR, including the one I owned for two years/30,000+ miles as a teenager. I did 3 or 4 top end rebuilds on that bike before selling it to a friend who did another few thousand miles before passing his test and getting a bigger bike, and neither of us ever touched the thermostat. I think this happens because people don't replace their coolant often enough or with the correct grade TBH. Or they just use water judging by the rust inside some of the secondhand barrels/heads I've bought in the past.
Also not sure why they'd supply stainless (not to be used in load-bearing applications) bolts for fixing the head to the cylinder; every time you take off the head (possibly to try a different squish shape according to track conditions etc. as the head is marketed as being "for tuners, not for people who don't know what they're doing") the threads in the cylinder will become a little more worn ultimately leading to failure. Incidentally the torque wrench setting for the cylinder/head studs is 13Nm whilst for the cylinder head nuts this is 22Nm (and 28Nm for the barrel nuts); the idea here is, the combination of long thread engagement, low (stud) torque value and being relatively undisturbed ensures long life for the threads in the cylinder and cases which are expensive. Surely supplying their own cylinder studs the correct length isn't beyond the wit of anyone capable of producing something as beautiful as that?
I have to say I don't go much on this guy; the upswept stainless expansion chamber appears to attach directly to the frame (which guarantees it will crack from vibration as the rubber vibration damper isn't present in the photos) and the Supermoto front caliper bracket looks a bit flimsy to me. Considering larger front disc rotor = increased braking forces, I'd want this to be at least as thick/beefy as the caliper mounting lugs on the fork slider. He's clearly good at machining and can in all probability use the two-stroke tuning equations to make an expansion chamber of the correct dimensions but beyond that, he seems to be of the rather dangerous mindset that no-one (including Yamaha) can tell him anything.
@HOTSHOT-III Absolutely spot on information here.
I've not had the thermostat fail on me, but MY GAWD does my DTR run hot. I am not making this up, my Vespa runs cooler than my DTR.
The DTR could seriously benefit from a lower opening thermostat, especially when you tune.
I've removed my thermostat and now the DT runs a cool 60 degrees. But you're absolutely spot on about having pressure at the cylinder head. It is stops pockets of stale gas forming causing hot spots on the cylinder head (promoting knock).
