Pete's TF125 build

[F5 Dave]

Well here's just a quick build to try and produce something raceable from something that looked pretty but was not. Pete saw the pics of the Orange NSR on Tardme and bought in faith.

When it arrived from Auckland clearly all was not well. In no order, the brakes were useless, the crazy big rear tyre made it handle like a truck, it was also offset to one side to get it to clear the chain. Uh Duh!

Supposedly the bike was faster than a warm FXR. Clearly that was a lie. The bike had never been raced I'd guess and the clutch slipped so bad it was a joke. And it vibrated.

Engine out and in my garage. Clearly everything ignition, carb, and mostly the porting were stock. The crank looked rebuilt and supposedly it has a TS gearbox in it which provides better ratios. We'll be checking that obviously, but there is a spare bottom end and that is a TS.

So the plan is to build a petrol push and ride engine for my good mate Pete that will give him the 2stroke fix he desires and be more competitive than his mostly stock FXRAGH. It will want to be grunty as it has to pull his, er. . . manly carcass about the track.

I decided we weren't going to stray into too much development. Just built with good parts which allow more power through good engineering.

At this point I'd like to thank our benefactor TZ350 who super generously sent some GP clutch parts, an RGV250 rodkit and all manner of odds and sods for the build. As well as some good ideas. GPs have an extra clutch plate and the inner basket swaps over. The outer basket has a different gear and matching gear doesn't fit the crank.
But the basket was better with less slop so I swapped them over and helicoiled the rivet holes and bolted together with lots of studlock.

[mr bucketracer]

Poor Mr g...

[F5 Dave]

After much adoo deciding what parts to hold it together with and with some ideas and measurements of parts TZ had laying around I decided to run the RGV rod and a YZ125 Wiseco piston.(we part number) It needed a rebore as there was a clear groove from the old ring where it must have rusted to the bore. I bought a longer hollow big end pin as the RGV one was a bit short. I also bought a Proper RGV bearing as the kit was aftermarket and the bearing a cheaper non flat cage design. Pjme in UK carry them cheap and post cheap once you email them.

The 80s YZ piston is much better than the 70s TF one and flat top with 1mm ring.

[F5 Dave]

This will be a work in progress
Look at the cool bag the piston comes in!

[Akzle]

fucken pete .

[F5 Dave]

Getting ready for the game.


Bwahahaha

Just kidding don't give a fuk about sweaty men playing a kids game.

Milled reed block to a more RM or RG angle.will cut barrel to suit.

[F5 Dave]

fucken pete .

We're good mates but never crossed that barrier.

However a little wine. Some smooth music. You never know.

[timg]

Cool. I'll be watching progress with interest.

[F5 Dave]

And more pics

Here are some heads. Dreadful offset plug. Also I can't machine with a central mandrel. This one is non squish so needs some weld.

[F5 Dave]

OK the piston is much shorter. Means the intake timing is 200 degrees. Way too radical. I'll fill the bottom of the port to reduce this.

Makes the ports too small. But I can now move the port roof up. Usually you can't do this but the piston is much shorter.

Here's the old crap piston.

Line is where the new piston lives.

[F5 Dave]

The pipes a bit shit so we'll see what we can do.

We'll run 196 and 129 which should see it OK. Try for 185 inlet after I fill the bottoms of the ports.

So we've ordered an ignitech and will run a lifan stator as shown in TZs thread.

38hp? Sure why not?


or maybe 1\2 that.

[F5 Dave]

So we're going to run .35 carbon on the reeds. The crank has been bored out to 22mm from 19mm which means we can run a better rod and it will be a more rigid crank.

The 1mm ring will flutter at much high revs than the snoozoki meaning better cooling and less power loss through fluttering.

[speedpro]

I ran my TS intake at 200deg by dropping the port down, not for the full width. Maybe 60% of the original port width. I also ditched the reed valve and devconned the hole in the bottom of the port where it used to be which made a nice flowing intake port. My thoughts were that the reed valve was only ever going to be used when the motor was revved beyond what the piston port duration was good for, taking into account resonance and such. Had 200 degrees exhaust as well and probably ran compression at about 14.7:1. It only made 19.9hp but it was a huge fat 19.9hp. Not tooo bad 25 years ago. With what we know now about ports I still wouldn't change the intake on that motor. The exhaust port I might change but only at the exit to the pipe. The transfer angles I did change but didn't go far enough at the time.

[F5 Dave]

Yeah I remembered your intake and devcon reed area. I'll try the 1/2 reed version, its only running a 24mm carb and I got it working well on the RG. I did consider cutting rear off and reedvalving it. Transfers staying completely std. This will hopefully be a low effort build making power from some sensible part choices.

[F5 Dave]

The crank has been bored out to take a 22mm pin. This allows the RGV rod and also should give some added rigidity to the crank as it pounds up and down, hopefully reducing vibration as a nice side effect. Some meat has been taken from the pin area to give more clearance for thicker rod and race clearance plus opening one balance hole should help the vibration point be moved to a non race rev area.

These bikes live their life at about 5000rpm chasing chooks or dragging Baabra up to the top paddock to do whatever farmers do in the top paddock.