Team 3UpRacing Blogs

Now that I’ve had the opportunity to put some miles (and a track day) under the belt of the work done to the rear axle, I thought I’d post some observations and conclusions. While I wasn’t really concerned about the structural integrity of the work I’d done, it was good to get confirmation that everything seems fine so far.

In summary:

• The standard wheel mounting spindle and nut was replaced with a one-piece alloy nut directly threaded into the hollow axle.
• A cush drive was added to the rear sprocket (see earlier post)
• The rear brake was converted to a smaller disc and underslung ISR mini caliper.
• Total weight (all unsprung) removed from rear axle amounts to 1190 grams. Not an inconsiderable amount.

Here are some details on the rear brake conversion. The cush drive and wheel nut conversion are detailed in earlier posts.

The rear disc is now 195 mm in diameter as opposed to 220 mm.

The ISR rear caliper and new caliper mounting bracket.

Caliper and bracket assembled.

And, finally, a few pictures of the complete, installed assembly.

After a last minute scare with the gearbox, I made it to the 2-stroke track day at Cadwell Park on July 1st. Sadly, I didn’t get as much track time as I had hoped. Three problems on the day prevented me from completing all of the sessions.

The first was that the battery connection came loose which was a simple and quick fix. The second, however, was more frustrating as the rear sprocket nut fell off. This, unfortunately, put an end to proceedings for me. Also, the clutch was slipping higher up in the power band.

Still, it allowed me to test most of the special parts, the engine, gearbox, electronics, suspension, etc. Here are the conclusions:

• The 38VM carburettors are OK for the track but will need to be changed to something like 35PWK’s for road riding duties.
• All the furnctions of the Ignitech unit worked flawlessly including the standard YZR-R125 tacho, the integrated shift light, the electric waterpump, the quick shifter (superb!), and the control of the power valves, and of course the ignition.
• The clutch pack thickness needs setting up properly and some new plates put in, maybe even add 3 TZ750 springs in order to eliminate the slipping.
• Suspension worked well given the relatively short amount of time spent on track. It doesn’t seem far off, though.
• The water temperature was never an issue all day. Good news then!
• The power was typical 2-stroke but not overly aggressive. No idea what amount of power it makes but it certainly seem to have plenty for the state of tune. Ultimately, it will go on the dyno to get it checked and setup fully, but not until the new carbs are on.

So, for a first track outing it was pretty successful.

Well, I finally managed to edit the video I took of the first startup. With no stinger nor silencers, and no water running time is obviously short. Still, it was nice to hear it roar to life!

This is also the first time, the forward engine mounts got any kind of test. Clearly not a full test, but so far it looks very encouraging. While still rubber mounted, the engine has none of the engine rocking couple that the standard mounting system exhibits. And, the engine vibrations are still pretty well dampened with only a very modest amount being transferred into the frame.

All this without the stabiliser bars!

Well, the big moment in every special builders project had finally arrived. Everything was triple checked and neighbours alerted to keep a look out for small explosions.

As the bike doesn’t have a kick starter due to the engine having TZ350 side cases, I used the external starter from my 95Racer. Luckily the cranks turns the same way on both. So, using a 19 mm socket on the flywheel side, the bike started easily.

It is a bit loud without silencers so kept running time to a minimum. I was, however, able to check all the functions of the Ignitech unit. Kudos to these guys. They build a very good product providing incredible value. I’ll put up a more detailed post about the ECU and its function shortly.

Highly recommended: Ignitech ECUs.

No drama whatsoever! Very pleased with that.

If you’ve followed my blogs for a while, you may have read that I maintain another website which is more about projects I do for customers. This blog is entirely about my own personal projects, i.e. bikes that I own myself.

It is becoming just too much work to maintain multiple sites and domains. Therefore, I will be moving this blog over to my main site:

I have been working on a complete overhaul of my 2moto site, which will launch at the same time. Hopefully the entire process will be completed by the middle of February.