My Minor

[tortron]

The header pipe is quite restrictive, so that will be next on my list. I have a good dr200 high pipe header or I may make another low one. The high one looks like it will want the rack rebuilt to clear the muffler. Also I have a piston suitito take it out to 170cc. Other than that I don't think it needs much more. Carb seems to do the job, its close enough (a better carb would let me fine tune it a lot better) and a custom ignition would be nice but both are not high on my want to pay money for list.

I'm pretty happy with it. Will see how it goes loaded on the open road. My main goal has been to get it to cruise at 100 happily. I think it will do that now. Might change a sprocket if needed. Other than that I want a different headlight so I can run a H4 bulb. I did that to my old gn250 and it was so much brighter. That had a 7" lamp though, this is a 5.75 I think


Been grinning all day, what a blast to ride it now, should have come like this from the factory. Going on another small bike ride next month, last time I left the other gn125 in the dust. Should totally pants him this time haha

[claych]

Put a stage1 HotCam in my bike
goes well

^ a bit understated I think lol,
looks like an absolute blast to ride!
- I do not know the product, will the clutch/geartrain
live after engine tq/hp has been improved ?35-40%?
(conservatively)

[tortron]

Should be fine, never heard of one failing in a racing dr125. The bottom end is close enough to a dr200 as well as the old gn250 (but just different enough to not be able to use those parts in this engine)
This engine has 11hp stock, i have seen some very heavily modified ones pumping double that

The only issue i have ever had with them is worn out timing chains and running out of oil

I have some uprated clutch springs for a dr200 but the clutch seems to grip just fine


One thing i could do is take out one of the double valve springs, Thats supposed to be good for getting the rpm up quicker, apparently it doesnt bother the valve bounce.
Im pretty sure it doesnt have a rev limiter in it (other than the valves) so i think i only got another 500 or so rpm out of the cam. But it does continue to accelerate past 80kph happily now.

[claych]

^
Again, I do not know the product---
Chain driven DOHC with 'rocker' arms ?

More questions to follow.

[tortron]

Single over head cam.
This one is 2 valve, some of the other variants are 4 valve

[tortron]

and now its ruined again








Not sure whats going on, this is the 2nd time its only lasted 50km after putting a new set of rings in. (no numbers for a gn125 or dr125 so i use dr200 min spec of 0.1-0.2mm. Maybe i need to use 0.2mm)
maybe its just cheap pistons expanding funny.
Started right up and i rode it home with no issue. its a little noisier now

[tortron]

marks on the piston (4 of them) tell me the piston didnt have enough clearance.
my bad for assuming a stock piston would be happy in a bore that i have honed twice already (i blame china quality control tbh)

[geezer101]

Yeah I bet the tolerances on the China piston were 'iffy' at best. Also could be the actual piston metallurgy - weird thermal expansion?

[tortron]

Yeah i dunno. possibly they are just crap (cant even get a non china piston in this size, hell even cant get a stock non china piston)
might have to use those cbf pistons.
Maybe the timing is still too advanced
i had to run 98 octane to prevent pinging under load (just me on it i could usually just run 95) but i thought with 2 base gaskets and running 95 id be ok

it didnt ping at all. could it be that it was just running hot? im not sure where to go from here tbh, itl be months before a replacement piston would arrive, dont have pocket money to rebore the cylinder to an oversized one.

might have to just run the big cam and standard bore.... so sad eh

[geezer101]

Take the piston out, polish up the skirt and try adding 2T synthetic oil 50:1 mix to the fuel to reduce friction + keep the piston cooler and run it at lower rpm until you get some k's on it and/or just hone the bore again to open up the tolerances. It's sucky that it's scored the piston up, but it hasn't eaten it - you might be able to salvage it yet...

[geezer101]

*if the rings are munched, nothing you can do. I've heard about scooter/bike rings from China being either too hard and shattering, or too soft and literally grinding away in no time

[tortron]

I follow the wiseco break in procedure (but I don't size the piston to the bore I guess) but tbh I don't see 100km of slow rpm helping the rings, and I feel it would. still heat up and expand just the same

Dunno maybe I'm wrong on that (but I doubt anyone who gets a 150 kit takes it in for machining). I will either stone the piston skirt and run it, or grind the top off one of my GS pistons (I'm pretty sure that's what they do to make these ones)

[geezer101]

Don't know. It sounds like the piston just wants to be unpredictable. You were lucky it didn't really lock up so at least you had that going for you. Wiseco's aren't sketchy Chinese pistons but you'd hope that the break-in wouldn't be any different

[tortron]

yeah ive got a guy going bananas at me saying i need to do a full 300-500 break in at low rpm

but that will stuff the rings up mate
NO YOU MUST

haha.

anyways, i ran the piston over a stone, dingleballed the cylinder
actually measured the cylinder and piston by diggin out my dusty bore gauges
and its now slighlty over the minimum clearance, so its self clearanced nicely

gn125 minimum 0.03 to 0.051, dr200 minimum 0.04 to 0.05mm - max 0.12mm
i measure 0.55 so i think im good


going to put it back in and immediately redline it through every shift

[geezer101]

lololol you really want GN go kaboom? 'I' would break it in just because I hate pulling something apart every 5 minutes (or Km's) Maybe something conservative like 150 k's and row it through the rev range. I'd be scared that beating on it straight out of the box would snap rings and cut trenches into the cylinder bore...

[tortron]

I've got a bunch of pistons and cylinders spare

Anyways. I did the wiseco break in procedure
Yester day I warned it up over idle for 5min. Let it cool, again for 10min. Let cool. Again for 15min and let cool then retorque the head (and re do rocker clearances as 2 of the head nuts are inside the cover).
Then today I did a 5min ride, let cool, then a 10min, let cool, then a 15 min ride and it's done.

Got a good bit of road for that. It goes up around an old quarry and special military training ground. It's hilly, windy, and narrow. So you get a bunch of different rpm and loads in a short distance (and it's about 2 mins away from the airport where I usually do my speed runs alongside the runway on the flat)
Didn't seem to have any problems. Engine got nice and warm, laser thermometer says it didn't get over warm,. Few heat cycles and no issues now. Will take it on a similar ride next good weather, and push it harder, but it seems happy

[tortron]

couple hundred km on it, compression at 185psi warm, so all good on the piston cylinder side

took all the badges off, remade some brackets in titanium, drilled the inside of some bolts out. saved about 200g. I want to get this to 99kg (stock wet weight is 110kg) so 10% off. Most of the way there already


made up a stainless steel case guard for the stator side. looks the business for an adventure bike

[geezer101]

Wow, you are going to need to do some fettling to get 10 kg's off the weight. Illegal LED's, alloy pegs, alloy triple clamps(?) and bars, bikini or ABS mud guards and a single saddle conversion might get it there. Looks pretty cool

[xboxrox]

tortron ~ cool looking bike, like an old Japanese Honda ~ plastic fenders will save weight ~ dirt bikes got plastic, no..?

[tortron]

yeah, im working on something that wont look too out of place

also i dont want to spend any money, its a cheap bike, so spending a hundred bucks is a big investment. Got a buddy offering to make some carbon fibre ones, so maybe that with some paint if i can figure out how i want them

It looks like an old Japanese bike because despite being a 2019 model they havnt changed them since 1980. (I had an 83 gn250 and it differed in that it didn't have a tach and had a front drum brake)

[tortron]

Wow, you are going to need to do some fettling to get 10 kg's off the weight. Illegal LED's, alloy pegs, alloy triple clamps(?) and bars, bikini or ABS mud guards and a single saddle conversion might get it there. Looks pretty cool

We can use leds in everything but the headlight i believe.
i havnt weighed it in a while but so far
3kg off from the battery
the protaper bars are alloy rather than the steel standard one so some good weight loss there (though i forgot to weigh them before i swapped and sold the originals)
The original rack is removed - it weighs the same as my rack, flyscreen, headlamp shield, gaiters. so 0 change there!


Next up to go is the rear lamp and heavy brackets. Going for a smaller enduro xr style one, should be a lot of weight there
Then the exhaust. header is actually 2 layers, restrictive and heavy. Have been thinking of how im going to do a muffler, but will use a dr200 stainless high mount header.


I could easily get rid of lots of weight - but i want to keep it pillion ready, so need it as a 2 seater with pegs. I also want the seat to be comfortable because every trip is a long trip on a small bike. Also im going to "have" to add some weight in adventure bike accessories. i want a sump guard/bash plate for some of the silly places i try make this go.
i think i can still keep it under 100kg with some creativity though

[xboxrox]

yeah, im working on something that wont look too out of place

also i dont want to spend any money, its a cheap bike, so spending a hundred bucks is a big investment. Got a buddy offering to make some carbon fibre ones, so maybe that with some paint if i can figure out how i want them

It looks like an old Japanese bike because despite being a 2019 model they havnt changed them since 1980. (I had an 83 gn250 and it differed in that it didn't have a tach and had a front drum brake)

Maybe like these plastic fenders ~> https://www.prestonpettyproducts.com...les.asp?ID=259

[tortron]

They are not my cup of tea. The rear fender isn't an issue as it's easy to get something that looks ok (the chrome bit you see is actually all of it, from the indicators forward it's just a plastic panel) the front one- I prefer a long fender to keep the road spray off
I enjoy seeing all the guys with cut down front fenders in the rides I go on, having engines covered in mud and filthy visors while I'm still clean lol.

I would almost want to replicate the one on there but raise it maybe an inch or two for clearance (they do this to the farm GN125s here so must work fine without being super high)

[tortron]

I asked if anyone knew where I could find an enduronxr style tail light in stock. The next day a guy delivered this for me

IMG_20201115_173225.jpg

IMG_20201115_173236.jpg

Standard one for reference


IMG_20201115_173052.jpg
IMG_20201115_173105.jpg
IMG_20201115_173152.jpg

I will angle the guard up to a more visually appealing position from stock. Looks a bit goofy with the big indicators, I think they would look better in the stock position but suck is life, some smaller ones will be in the future.
Still need a number plate light and mount. The plate fits perfectly across the back of the rack on the seat, so probably there with a couple of tabs to bolt it to as it's easy.

[tortron]

Attachment 25961
Attachment 25962

Trying to figure out the least offensive way to have a brake light, number plate, number plate light and a reflector

Might end up getting a different guard so I'm not fully set on making this one look perfect

Plate on the rack is quick, easy, functional, and not likely to get caught on anything so maybe that. Looks funny though