china bike 122cc dohc 4 valve project

[epod]

Nice work bro

Show me more please. Great stuff. Really want to see all the timing gear come togeher. Peace

 

[tormentandglory]

getting closer...

ripped heaps more metal off tonight! cams now spin, and its starting to look like a cylinder head, not a huge chunk of alloy next job is to fit the cam gears to the cams.

 

[tormentandglory]

some more pics

gotta strip another engine tomorrow to get some more parts. need another cam sprocket and I have to join 2 chains together. original chain is way to short.

 

[unit_mx]

My god , that thing is a monster. Can't wait for the finished product... Looks stunning.

 

[tormentandglory]

timing chain layout

I'm using the little gears off the crappy chinese electric starters for cam chain idlers. I've machined the centres out and pressed ball bearings in. cam gears aren't fitted properly yet, thats tomorrows job.

 

[themountain]

you are not putting some guides in?? this engine will rev to the moon and the chain is pretty long....you better take care of that

 

[tubes380]

mate thats coming along nice!!!
how are you going to seal it up, whats your thoughts?

 

[cardy]

thats pretty intense

 

[tormentandglory]

you are not putting some guides in?? this engine will rev to the moon and the chain is pretty long....you better take care of that

Hehe yeah, I'm aiming for a revvy engine. I'll be disapponted if it wont spin to 14k. If the chain rubs in the top of the head I'll put a nylon runner in there, but I'll wait and see first. I'm sure it'll have to come apart a couple of times to sort out bugs before its perfected. I use manual chain tensioners from early model z50j's in all my engines. The spring type ones are useless. As for sealing up the front, thats gonna be a bit of a challenge. I'm sure I'll come up with something

 

[tormentandglory]

Cams completed

Cams are now finished completely, and the timing gears fitted.

 

[corey58]

looking like a motor now, very nice

 

[coolmodee01]

lookin sweet bro
cant wait to see her run
the only issue i'v piced out of you set up is the lack of guide between the 2 cam sprockets
you may find under no load that you will get a bit of chain slap and if your unlucky it will jump a tooth or even throw
if you can rig up a guide or an idler between the 2 you will solve this problem and you will also have more teeth in mesh so power transfer through the drive wont become and issue

yes room and suficient lubrication might be an issue also

but i like

so when ya finished can ya make a 3 valve one for my 110 that would be great

how much has this cost so far

 

[numroe]

Cams are now finished completely, and the timing gears fitted.

Good work! I notice your cam lobes look very smooth in terms of their curves from initial valve open until close. And one cam has a "fatter" duration on its lobes than the other. Where do you get your cam shapes from? I mean do you come up with those yourself too?

 

[tormentandglory]

Hehe this one started out as a 110cc three valve! It actually hasn't cost much to build so far. I'm a cheap-ass. I'm always looking for free stuff/cheap stuff to work with.

I got the original engine super cheap. It had a broken top mount, which has been welded up again. I got a whole gpz400 engine for $100, with only 1200kms on it. That donated the piston and rings, and leaves me with 3 spare sets. I got a complete zxr250 head for a slab of beer from a friend at a motorbike shop. $60 for an inner rotor kit. $70 to get the cylinder bored and honed (I don't have a honing machine! ) Aside from that, its just been bearings and billets of material to work with. I've pillaged a lot of odds and ends out of friends junk boxes to. When its all said and done, it shouldn't owe me much more than about $600. Oh, and about 200 hours of my life.

All of the engineering has been designed around parts that I could get for minimum cost. I've been wanting to build this for years but only recently have I found a set of components that seem like they're gonna work well together.

Oh, the chain won't be able to jump over the cam sprockets, there physically isn't enough room between the gears and the inside of the cambox. Its a tight fit, fiddly to assemble. And with a manual timing chain tensioner, the chain wont have much chance of flapping either.

If anyone needs custom machining done, I might be able to help out. I charge sensible money for my work. God knows these china bikes are built so badly, pretty much everything needs to be reworked. Email me at [email protected] (no tyre kickers please)

 

[tormentandglory]

Good work! I notice your cam lobes look very smooth in terms of their curves from initial valve open until close. And one cam has a "fatter" duration on its lobes than the other. Where do you get your cam shapes from? I mean do you come up with those yourself too?

Both of the cams are the same and were cut from the zxr250 exhaust cam. The zxr inlet cam had slighty less duration. Lift is 5.8mm. I just chopped it up and machined the ends for bearings. The timing gear hub is a press fit, just like china bike cams. I haven't measured the exact duration yet, but they look pretty fat.

 

[tormentandglory]

Almost ready to run!

Cylinder head is nearly finished. Yey! I can't find anyone in melbourne who can machine the valve seats for me because they're so small and they run on 4mm stems. Gotta send it to rams head service in sydney. Hopefully they'll get it back to me pretty quickly.
I ditched the gpz400 piston, I'm using a yx140 piston instead now. Needed a few mods, but its much lighter, it fits directly on to the conrod (without the spacer sleeves the kwak piston needed) and doesn't need the spacer plate under the cylinder either. Compression has been set at 12:1.
Cam duration is only 260deg, I was hoping they were gonna be hotter than that, but I'll run em and see how it goes. If its a bit flat I'll get them welded and re-ground a bit hotter.
Crankshaft rebuilders honed my barrel oversize, and its wrecked I'll have to find another one and get it bored again. Aside from that I just have to make a timing chain cover, cam covers, set up external oil lines to the head and its about ready to go. I'm pretty confident its gonna howl like a mad thing hehehe

If anyone is running a mojo 110cc three valve, the yx140 piston might be a good hot up. Brings it from 107cc up to 122cc and will fit in with minimal fuss. Might need to stick another base gasket in for head clearance. Maybe tweak the chamber and piston crown a bit with a die grinder to, for valve/piston clearance. Easy mods though, if u want some more sniff for not much cash. You'll need to port the head to, a mouse couldn't fit its dick in the stock ports, they're tiny!

 

[tubes380]

i have a lifan 138cc replacement bore if itll work, not sure what your looking for?

 

[tormentandglory]

I found a new barrel, and got it for nothing to . Made cam covers tonight. Can't do much else until the head comes back.

 

[Sidney]

Hey man, that is looking soooo sick.

I'm guessing you are a machinist by trade?

 

[epod]

Allmost there.

Rippin mate. What a piece of art. Rams will charge you a bit though, although I here they do great work. Are you gona let us know how many HP she'll pump out, when it is all done.
Ride on.