tortron Posted January 29, 2021 Author Share Posted January 29, 2021 Figuring out what degree of retard I want to go. Here's some measurements I took Gn125 head has Valves 25.5/22.5mm Inlet port 25mm Dr125 head has Valves 28/25mm Inlet port 28mm Dr200 head has Valves 33/28mm Inlet port 30mm I could run a domed piston in the dr200 head to make up for the massive combustion chamber, but it and the ports are pretty big I think I could run a domed piston in the dr125 head too, but gotta check that for clearance, I think it has the tightest valve angle too so a big cam may upset it Dr125 head needs work, the others I could just put on with the correct piston cam combo. Or maybe I clearance the low dome piston I was using in th GN so the valves don't touch (not entirely sure if it kissed and bent first, or if the valves collided and then got squashed tbh) 2 Quote Link to comment Share on other sites More sharing options...
tortron Posted January 29, 2021 Author Share Posted January 29, 2021 Looks like the gs150 piston would have more dome than the dr200 when installed. So the compression may work out. Not convinced on the big valves and ports tho, I think with slower airfuel speeds it would big the engine at anything less than full throttle full rpm So no issue then Tho Quote The LT230 head just measured 30cc on the chamber and a whopping 50cc on the intake port drz125 21.5cc's chamber - intake portis 36.5cc The lt230 head was either the same as the dr200 or ever so slightly higher compression i believe Quote Link to comment Share on other sites More sharing options...
tortron Posted January 29, 2021 Author Share Posted January 29, 2021 my eyeballs are starting to fall out in the shed, but some rough and ready measuring and i think that domed piston will work. The deck height (at the edge) is about 3mm taller than the low domed piston - which is heaps, but measuring from where the top ring was reaching on my other cylinder (only used with one base gasket) it looks like im getting 1mm clearance with no head gasket and the dr200 cylinder pressed onto the 150 cylinder. So depending on head gasket (i have single layer and thicker multilayer) i then have the option to use 2 base gaskets to fine tune the clearance. Will go ahead and prep that head for install and then squish some stuff to see how it and the valves go and it all good take it for some 0-10000rpm from cold test rides. I think it wont be a winning combo but i cant find any one running it (just people wanting to put a 200 head on a stock 125) so will satisfy my and the 6 people on youtube who are interesred in ruining GNs. really wish i had a dyno for it tho 5 Quote Link to comment Share on other sites More sharing options...
tortron Posted January 30, 2021 Author Share Posted January 30, 2021 threw it all together and the deck height is just too much. Looked back at my notes thinking i should get an lt160 conrod and make a stroker (5mm shorter). Noted the FX125 uses a 3mm shorter rod, which is other wise identical to the gn125 rod (pretty sure the gs150 also has a 3mm shorter rod, which makes some sense, thats the piston i wanted to use). Dont really want to split the cases and change a conrod, but could be something to do later on (plus its about 130 for a lt160 conrod and i dont want to spend that) Quote Link to comment Share on other sites More sharing options...
tortron Posted February 5, 2021 Author Share Posted February 5, 2021 See Intake - Radial clearance 4mm Piston clearance - 2mm Exhaust Radial clearance - 2.5mm Piston clearance 1.5mm Looks like safe r.o.t for clearance is Intake 2mm Exhaust 2.5mm Radial 1.4mm So that and the witness mark on the piston in the exhaust notch probably means the exhaust valve hit the piston and then the intake valve got caught on that and went 90degrees Il turn a valve into a notching tool and take out the exhaust another 1mm, got a wornout piston to cut in half to check how thick itl be, should be fine tbh as the intake is milled deeper. 3 Quote Link to comment Share on other sites More sharing options...
tortron Posted February 5, 2021 Author Share Posted February 5, 2021 Some old sanding belt hot glued to an engine valve and all thrown together in a drill press. 7 Quote Link to comment Share on other sites More sharing options...
Popular Post tortron Posted February 5, 2021 Author Popular Post Share Posted February 5, 2021 Now at 3mm clearance on the exhaust valve which should be all good Now to put it all back together and blow some other part to bits 14 Quote Link to comment Share on other sites More sharing options...
tortron Posted February 13, 2021 Author Share Posted February 13, 2021 Had a look at DR125 engine mostly full of smoooo, gear lever welded on, new clutch plates or very new ones. pretty sure its a 6 speed, as far as i can figure out its a 1984 engine, some people say they are all 6 speeds, some say they are all 5 speeds. Suzuki says 6 speed, 'feels like' its a 6 speed but soemthings not right with the shift as the lever doesnt go back into centre and sometimes it goes into gear and sometimes i can just keep spinning it over. Probably full of smoo again. Smoo seems to be finely ground camshaft and camshaft 'bearings' where it runs in the head. Plan is - get a reamer, linish down the head and cam cover, ream cam bearings back to spec. Put in a big cam shaft - split cases, clean out the smoo. throw cheap GN parts at anything thats stuffed - Michio Suzuki willing its a 6 speed but if not thats not the end of the world - excessively big bore cylinder. i.e as big as i can go - probably stroke it depending on a few things can fit a dr200 crank - and therefore a 16mm gudgeon pin to dr125 cases. but im not 100% sure on how it interacts with everything else. the primary gear i think needed to be swapped and something about the clutch basket. The dr200 crank also has about 11 mm more stroke. I have all these parts already exploded in a box so trying them out is no worries. pretty sure a 200cc sleeve needs the cases cleared on a 125. TLDR, fucked old engine is fucked 5 1 Quote Link to comment Share on other sites More sharing options...
tortron Posted February 13, 2021 Author Share Posted February 13, 2021 Might heat squash a Conrod to make a stroker. These used to be sold for the Dr and drz by Powell. But are long gone now. From what I have found out they didn't use a stock rod. Possibly so they could sell you the piston too, or possibly the Suzuki rod wasn't suitable. I think it would be ok with a forged rod, $18 China GN rod probably is fine to do this to I'm sure. Will consider this as I look for different suitable short rods from other bikes, big end pin will be moved for stroking, so a different size is ok. Better sized small end Is also ideal for piston choice. "Bolt in" option is a lt160 Conrod which is 6mm shorter. The old Powell kits were 8-10mm 3 Quote Link to comment Share on other sites More sharing options...
tortron Posted February 14, 2021 Author Share Posted February 14, 2021 Was Gona sell this from my dr200 stash, but this mid 80s rm125 seat fits the GN amazingly well. Even the I think it's an airbox scoop built into the pan sits nicely between the frame crossbar and rear fender Real hard tho but 6 Quote Link to comment Share on other sites More sharing options...
keltik Posted February 15, 2021 Share Posted February 15, 2021 Best be naming this thing the ship of Theseus 1 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted February 15, 2021 Share Posted February 15, 2021 Digging the new seat! Quote Link to comment Share on other sites More sharing options...
tortron Posted February 15, 2021 Author Share Posted February 15, 2021 16 minutes ago, flyingbrick said: Digging the new seat! It's pretty hard. Be good if the GN had any degree of performance, but Luxo GN cruiser seat is fine for the casual cornering it's capable of. It is 600g lighter tho. And doesn't allow for a pillion Quote Link to comment Share on other sites More sharing options...
tortron Posted February 15, 2021 Author Share Posted February 15, 2021 39 minutes ago, keltik said: Best be naming this thing the ship of Theseus Never seen something modified before? Quote Link to comment Share on other sites More sharing options...
Positive Ape Posted February 15, 2021 Share Posted February 15, 2021 Yeah, but this is some next-level committment to eeking out the last iota of potential! keep up the good work, Tortron Quote Link to comment Share on other sites More sharing options...
Muncie Posted February 16, 2021 Share Posted February 16, 2021 Tortron Millyard. Convert it to 2 stroke for less valve hassles? About 86% serious, reckon you could do it half the strokes 2x the power. 3 Quote Link to comment Share on other sites More sharing options...
tortron Posted February 16, 2021 Author Share Posted February 16, 2021 Honestly, unpopular opinion here. I dont give a shit about 2strokes. I would have to buy a lathe and a mill etc etc but i did briefly think about a parallel twin. seems like a lot of work for no return tho Want a garbage Suzuki farmbike in 2stroke get one of those rego'd ts185s (would toats get a new one tho tbh) Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted February 17, 2021 Share Posted February 17, 2021 What are your goals with this? Or just muck around until ya bored? Quote Link to comment Share on other sites More sharing options...
keltik Posted February 17, 2021 Share Posted February 17, 2021 1 hour ago, tortron said: Honestly, unpopular opinion here. I dont give a shit about 2strokes. Invented by Satan to keep small engine mechanics in business and developed by nazis to actually make power. 1 Quote Link to comment Share on other sites More sharing options...
tortron Posted February 17, 2021 Author Share Posted February 17, 2021 11 minutes ago, flyingbrick said: What are your goals with this? Or just muck around until ya bored? Make a lol little bike for dumb adventures So that means not aiming for bleeding edge performance and weight savings out if it Would get something fast/capable if that's what I wanted 4 Quote Link to comment Share on other sites More sharing options...
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