Let's call it a RNZ 140

[Cheesy]

This is going to be a fairly long and involved project, mainly because I can and it is cheaper than buying something that still isnt quite what I want.
To start the story the wife got dragged along on a bit of a trail ride a round a farm near my dads place, this involved her learning to ride an absolutely clapped out AG175 frambike..... you know the ones, foot pegs that wobble and point down, bent handlebars, brakes that dont really work, old bald hard tyres etc, in spite of this and falling off in a creek she really liked it. Excuse for a project.

Probably her biggest problem was the kick start and not being tall enough to start it on any sort of hill, this lead to the two critical factors for this build.
Electric start
Low seat height

I ended up with a RM85 with a dead engine (needs a sleeve and piston kit) and decided to be difficult and put a Suzuki 4 stroke engine in it. Now for anyone interested a Honda (or clone with electric start) engine would be infinity easier to put in because they dont pick up on the swing arm pivot bolt like the Suzuki engines. I found a $20 DF 125 engine on TM but the cases were stuffed as was the cylinder and crank, the cam chain was so worn it was touching itself. I was very kindly donated a set of GN125 cases and a crank from a member on here so that is the start of the build.

I dont have any pictures of the RM to begin with but there was a lot of angle grinder use and a couple of 1mm cut off discs and flap discs sacrificed to make enough room for the engine

[bogan]

We need pics...

Sounds interesting though

[ducatilover]

pics are mandatory

[Cheesy]

Getting there, photobucket is slow

Honda engine, too easy (and no electric start)


DF125 engine


The bottom engine mount is right in the middle of the cross member so that had to come out too


I made up a jig to make sure everything stayed in place with most of the frame now removed, it locates on the swingarm pivot and the bottom head bearing seat, it also has a location for the linkage mount which came out with the crossmember. The pieces the swingarm bolt sits in are the same width as the swingarm.

[Cheesy]

In the second to last picture you can see how much had to be removed from the cases to fit between the swingarm.

The whole mount needed to be cut out of the right hand case, this is the actual GN case I will use


Attack of the hole saw, it still needed a fair bit of filing to fit the curved piece nicely


And welded in, I had it clamped to a flat surface but had the case sitting on bits of craft knife blade to leave me some metal to file down to flat on the bit I welded in.


Now I am not a pro welder but I can stick a couple of bits of metal together though. The Suzuki cases on the other hand were crap to weld, they are full of inclusions and contaminates, there were even bits no where near the arc that bubbled! I will use some Devcon to make sure it is oil tight near the end. The left case needed cut down a bit as well


And welded


It would be nice to have a mill for this but no. Luckily these have a breather system up the back of the case so there is an internal web close to where I was welding. Coloured in with black vivid and then rotated a file on top of an ejector pin stand off near the crank (essentially draw filling) until the vivid was just being removed.

[Cheesy]

Now the RM frame has a 12mm swingarm bolt while the GN has a 14mm bolt. I also needed to take a few mm off the left hand side of the LH case. Enter these funny Chinese hole saws, I got a set of them and the ID and OD almost match up


First I went through the whole thing with a 16mm one. Conviniently I had some shouldered bushes I made a long time ago for something else that I could use to replace the iron inserts in the cases. This picture is a few steps at once, one of the bushes is in place, to bring the surface down to the correct depth I stepped up the various size hole saws with the small one mounted backwards as a pilot. After this picture I cut off the excess with the angle grinder and 1mm cutoff disc. The other side just needed a recess for the shoulder.





And sitting in the frame again, its to high in this picture, the head wont come off the studs

[Cheesy]

Oh and the 140cc bit, since the cylinder was stuffed I bought one of the Chinese 150cc kits which are really 140cc, 62mm piston in a pretty standard cylinder, the only difference is the liner is not turned down as small where it goes into the cases as the 125 one

[Kickaha]

Oh and the 140cc bit, since the cylinder was stuffed I bought one of the Chinese 150cc kits which are really 140cc, 62mm piston in a pretty standard cylinder, the only difference is the liner is not turned down as small where it goes into the cases as the 125 one

I could have told you how to get it out much bigger than that

[Cheesy]

I could have told you how to get it out much bigger than that

Yes, that may have cost a lot more though! Maybe a cut down GSXR1000 head as well.....

The GN needs a head steady which the RM didnt have, I cut a plate to fit where the CDI was mounted, filed a couple of M8 nuts down to round and welded them to the plate, then drilled a couple of holes in the frame for the nuts to sit in and welded it into place. It would have been nice to have the motor a bit closer to the frame spine but that is as close as it can be while still being able to get the head off.





Then the head steady

[Cheesy]

Next, frame rails. It would be nice to have a tube bender and new steel but I dont so the RM rails were spliced into some bends I cut out of an old bike rack that goes on a towbar. I cut 4 straight sections about 30mm long (25mm*1.6 tube), cut a piece out of the middle so they were a fight fit into the frame tubes. The bike rack had the same bend radius as the RM frame around the swingarm pivot so that got carried around, not the best looking but its what I had.



And sitting with the rails in place



Checking starter motor clearance



Drill press abuse for the down tube, an old exhaust clamp worked quite well to hold it in place

[Cheesy]

Down tube tacked in, when its closer to finished I will wrap the ends of the down tube to close up the hole it the bottom. The plan was to have a perfect fit on everything and tig it all.... haha not going to happen will be miged, much quicker too.



Then reused some engine mounts from the RM frame and a 25mm RHS for the foot peg cross member and some 3mm cold rolled sheet to attach it to the frame rails



Crossmember back off so I can weld the frame rails to the frame, looks like some sort of cow catcher off a custom Harley. The plates will be completely boxed eventually. I also had to slot one of the engine mount plates as there is not enough clearance to pull the bolt right out, even the bolt I found with the wasted shank and ground down head.



First join in the frame rails fully welded and cleaned up with the crossmember tacked in. The next job is getting the linkage mount onto the crossmember however it does not fit into the jig I made as it sits at the moment so a bit of grinding and tacking scraps together will be required. That brings it up to its current state

[Cheesy]

It slows down a bit when it gets to real time.... The singarm mounts pulled in a bit when I welded the frame up, not a huge problem, its probably 0.5mm too tight to get it all in place so easily fixed. Managed to get a little bit done in the garage with 4yr old daughter in the weekend, a bit of cutting out and sticking bits of cardboard together, I just need to get her welding next then I wont hear anything about Elsa, Arna and Frozen again!! It is tricky fitting a battery in there as well, doable though. I still have to decide whether to make up the airbox with aluminium sheet or make a fibreglass one, since I need to make a glass boot to the carb it may well be easier to make it all from glass.



The RM fuel tank isnt going to fit so the plan is to have a go at making an aluminium tank. Which if I can make as well as I can imagine it, it will be way cooler. I dont like air cooled bikes having fake radiator shrouds, its kind of a form over function thing... Also the aluminium tank will be symmetrical (no radiator cutout) and hold a bit more gas than the RM tank.

[Cheesy]

A bit more done, most of the head tube / down tube gusseting has been cut out and welded in. The steel I had was a bit thinner than I would have liked so I added the hole/tube to prevent any local buckling



The lower front engine mount intersects the frame rails so these were notched and have crush tubes welded in, there will also be a flat plate added to the inside that will extend down to the frame rail centre line.



Welded but not cleaned up yet, the coil is also mounted to the frame gusset

[Cheesy]

Front engine mounts welded in and down tube to frame rail junction tided up



I was going to put tubes back in for the diagonal bracing of the cross member but since I needed to box the plates that attach the cross member to the frame I just used some 3mm plate with some speed holes



Im still impressed by the quality of the holes cut with the funny Chinese hole saws, I think it was about $20-$25 for a set of 6 of them, 16mm to 32mm. The arbors are not great but I have been using them on a M10 bolt with the head cut off and a flange nut behind the cutter, I think just putting them in the chuck on the round shoulder instead of the three flat faces would work alright as well.



Now its time to do a bit more scrounging for some more engine parts and a more suitable carb, a TM31 will be pushing things a bit I think. So if any one has some GN bits they want to get rid of let me know, all I really need are both engine covers and the electric start, fly wheel and stator bits. Conversely if any one needs DF kick start parts or engine covers they are not much use to me.

[bogan]

That's some pretty good progress man!