My Minor

[xboxrox]

I'm impressed, you guys know a lot about life, welding & metallurgy..! Even more about bikes..!

These factors will help you braze 'n solder better (think % of bond in the joint between the pieces 80%+ is great)
a) Low gas pressures -- keeps the heat from bouncing off the weldment -- oxy 6psi try 3 psi for fuel -- (can't remember BUT LOW pressure works) use a neutral flame
b) Joint fit-up -- keep tolerances close (.003" or less)
c) Clean base & filler metal (sanitary clean)
d) Best quality & proper Flux (clean & thinned with water if needed)
e) Proper torch manipulation (evenly heat the pieces) keep the torch moving

Aloha --
George (one new case Oahu today)

[tortron]

New project dog
Rescue, probably half English pointer. He's been plated and tagged apparently as he's got multiple vin numbers (micro chips lol) but is freshly regod
Pretty thin, but healthy. Not trained in any way but he's a sweetheart and learning the basics
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Here he is helping me work under the exploder
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[geezer101]

Nice tortron. And he's just doin' doggo stuff

[85Ram50]

Here is a picture of the oxy set up I have. Got the carrier with bottles at an estate sale and bought the hose and gauge kit at harbor freight. Normal sized fittings.The welder supply had to keep and test my bottles before they would sell me refills.
oxcyacet1.jpg oxyacet2.jpg

[geezer101]

That is a nice old school welding rig I get that gas suppliers have to make sure nobody does something sketchy with bottles and turn themselves into a crater but at least they don't hold you for ransom like they used to here.

[tortron]

got the GN back from suzuki
welded up with birdshit and fisheyes in the paint - so it matches the factory finish at least

bought a bunch of parts, but none of them ended up fitting (i got all the kick start components from a dr125, i had been told by someone that they had done a kickstart conversion to a gn, maybe an early gn, but this one doesnt have any of the castings inside the crankcase, got to use a dr bottom end to do it. Got a china performance cam, supposed to be a copy of the standard LT230 cam i believe, i ordered 3 of them since december last year, one finaly arrived, it was a standard cam at twice the price, so thats out, and 3rd i got a gs150 piston to see what i could do with it, would be good with a 200 or 230 head, but not for a gn125 head as shown below)

I said bugger it, and am getting a hotcams grind for the lt230, which should go well in this engine, but is expensive for a bike like this

so on to the work i can do

IMG_20200619_105213.thumb.jpg.9125f9e85b9c02426c9b67c3c9a53ae0.jpg
left to right. totally flat 125 piston, slightly domed big bore kit piston (which i have taken the sharp edges off the valve recesses and mirror polished), much more domed gs150 piston.
51101IO7utL._AC_.jpg
GN has squish areas like the head on the left. GS and i believe DR have a more open combustion chamber, and the DR200 and LT230 have a totally open combustion chamber and i beleve use a domed piston for the squish area. Early GNs have a piston with a big knuckle on top, so lets ignore those.

heres my head with a 125 head gasket (silver) and a 150 kit head gasket (black and 1/3rd the thickness)
IMG_20200618_145059.thumb.jpg.8553b0bbf6c37061ea5c4d2e7b5b90d4.jpg
IMG_20200618_145116.thumb.jpg.e85a10bcaf844ea63a7feac06a05bff1.jpg

heres a close up of the sharp edge of the squish area
IMG_20200618_145150.thumb.jpg.4a675086d01d5b0d6883536a1e47e0d3.jpg
and im talking cut yourself on it sharp.

Now, heres my piston thats in there now
IMG_20200616_130648.thumb.jpg.2187d5ab27005406b150af69c6d4ead6.jpg
Ive been getting blowby into the crankcase, and theres scuffing on the intake side only. I believe this has been caused by preignition.
I may have mentioned i have had to use premium 98 octane since i put the big bore kit in.

a short bit on squish areas
these act to prevent unwanted detonation by forcing the air fuel mix back towards the combustion chamber. You want a tight clearance to limit spots that can cause ignition, typically modern cars have a large squish area, and messing with them is generally discouraged

What i think is happening is that instead of the squish areas squishing the mix back towards the combustion chamber at TDC, that the clearance between the domed piston and the edge of that squish area is causing some of the mix to become trapped at the outer edge of the piston and causing preignition expecially when at high rpm or under load.
The flat edge on the piston is too narrow. Piston options are limited in this size with a 14mm pin size. Best performance option is to get a bigger head and a domed piston to match, next best is to get a flat top piston. next up is modify what i have and hope it works.
An extra base gasket is my back up plan.

I figured i could break that sharp edge to help the mix to flow past the dome edge better
IMG_20200618_145202.thumb.jpg.4887dd09cf15bb6f4ec3a967bd5518d3.jpg
IMG_20200618_145215.thumb.jpg.14dc62be1dffcea088dd0b00fb0d9b9e.jpg
IMG_20200618_145237.thumb.jpg.ba7c45fef474401256f9aaac8d9ce710.jpg
i broke the edge, and cleaned everything up to 1500 grit and then a polishing mop. At a guess i took maybe 1mm from the sharp point and rounded it over. The consensus is that you want that edge sharp, maybe a quick sand so you dont cut yourself, but dont round it. Well most people arent having knocking issues and are using bigger domed pistons in a higher compression chamber designed for a flat top, so i think im good, but im yet to test it.

and then while the head was apart i cleaned it up. nothing major as its about as good as its going to get already. (better to get a larger head that already has bigger ports and valves)
IMG_20200619_135204.thumb.jpg.1936bfc44ecc145997aaaa85ba77b171.jpg
Head is set up for EGR for some markets
IMG_20200619_135213.thumb.jpg.527f97d75ba317225f098d7312cbb35e.jpg
IMG_20200619_135241.thumb.jpg.3ef2c10c32dd450d0f3882364e155664.jpg
little bit of a step on this machined section
casting is pretty good, just a little to clean up on the sides


80 grit finish on the intake
IMG_20200619_135254.thumb.jpg.f991dcda9fe870db1d17d4eee1e90eb8.jpg
took a little off the leading edge of the valve guide

IMG_20200619_135330.thumb.jpg.36f8ca7ce5302269cdfea556d152c41e.jpg

and similar with the exhaust, but i went through the grits and polished this
IMG_20200619_135343.thumb.jpg.ed1b21ae3a63eb440f60ce84bd7e73a1.jpg
IMG_20200619_135356.thumb.jpg.a27e6c09ef89fe8fb536f6202d245c22.jpg

only tools used were an electric drill and a 6mm diameter aluminium rod with a slot in it to hold some sandpaper (and a polishing mop)


I have also polished the valve faces and backs (i left the back of the intake a bit rougher incase it helps the fuel tumble in) but mainly just to clean them up.

Sound about right Geezer?

[tortron]

oh i just found a piston that might suit for a 160cc. need to check out the height, but looks like it will work. its flat too

[geezer101]

Sounds spot on dude I haven't read up on your GN %100 - you derestricted the carb spacer and picked up a bigger main jet? I might round the back edge off the intake valve a little to improve fuel charge fill - and maybe index the spark plug so the open gap is facing into the roof of the combustion chamber just to be OCD.

[tortron]

Carb spacer seems fine from factory, (bike isn't restricted like some used to be) I ended up running the standard jetting, I tried bigger and smaller and all combinations of needle height with my wideband and standard was as good as it got (I think needle mods would improve it but I haven't been bothered to get into that drama too much yet)

You are probably correct on the intake valve, it was something I was thinking of today.
Same with the plug, I noticed it's facing away from the chamber when I took the head off, new one will be indexed

[tortron]

IMG_20200715_130110.thumb.jpg.26da3a4f1b3c56014d6f312c304128ae.jpg
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Why not go full Ham on this, its fairly cheap fun (not cheap in a dollar per horsepower, but cheap in terms of if i blow the engine up i can just get another lol)

[tortron]

found some more pistons with a 14mm wrist pin
pistons1.jpg

will bump the cc's up to 155 or 160 respectively

good cos i have a scratched cylinder here waiting for a new life

[tortron]

Put the cam in and broke it in, but havent been riding cos of lockdown and rain.
have been doing this



Tiny home going in there. 3m x 7.4m

[tortron]

welcome to tortrons house of rust


Just doing some typical 70s holden rust

[tortron]

And then I made a new one


Waiting on some paint to dry and then I have a reproduction panel to weld back on top (after spending the morning making it actually fit)

Then the other side

[85Ram50]

Nice work.

[camoit]

What a nightmare fix. I guess the window was leaking for a long time.

[geezer101]

Oh sheee-it. Are you sure this truck wasn't dredged from the bottom of the ocean? That kind of rust is normally a deal breaker. My hat off to you for even being mad enough to tackle it dude

[tortron]

What a nightmare fix. I guess the window was leaking for a long time.

It had some small patches put in the cowl corners back in the late 80s or early 90s, plus the screen looks like its been in and out a few times, so rust started forming under the mastic and here we are today. They all rust out here

Oh sheee-it. Are you sure this truck wasn't dredged from the bottom of the ocean? That kind of rust is normally a deal breaker. My hat off to you for even being mad enough to tackle it dude

These old holdens are worth fixing now days, can get a complete upper and lower cowl panel if you are keen, but they are for all the H series holdens and need quite a bit of work for the price. normally just the corners rust out.

[geezer101]

Ah that's what threw me. I'm looking at the first pics and thought "wait a minute... since when was a Gen 1 built like that?" I should've realised by the corner of the dash pad it was a HQ/HZ Holden. Bet the frame has been patched in that place behind the cab a few times too.

[tortron]

Bet the frame has been patched in that place behind the cab a few times too.

Not even gona look tbh, squizz some acrylic lacquer on it and send it out the door

[geezer101]

I pity the fool that has to deal with that. Notorious for completely rotting out. I saw a HQ folded into a 'V' in North Adelaide due to frame rot

[tortron]

And it's fixed
IMG_20201012_120823.jpg

Was a bigger to blend the roof in, the brake shop managed to spray fluid on the roof???? And it lifted the lacquer. Had to use some 2k to seal the edges to stop it lifting when I sprayed fresh stuff on top. Came up pretty good, will look original with a cut and polish.
Should probably charge for this eh