Charlie Oakman finally finishes the TZR250!
…and three back for our very own Fast Berk Charlie Oakman. Will he make it to Snetterton in time?
The van is packed and I am finally heading off to Snetterton for what should prove to be an interesting weekend. As you may recall we had a Yamaha TZR250 2MA desperate for attention, pretty much in bits, languishing at the back of CMM sister title Fast Bikes’ garage. I came up with an ambitious plan: re-build it and race it at the final round of the Yamaha Past Masters (YPMS); nothing that out of the normal there really apart from the fact that I had never ridden a two-stroke before, let alone built one – never raced before either! It’s been a challenging nine months. When I signed off last month I had another van packed, this time for a track day at Castle Combe to test the build that our local Yamaha dealer, Phoenix of Trowbridge had spent so much time helping with. After unloading, I was soon on the phone. I had got through noise
testing okay but then the bike just died, started and died again. As I chatted this through with Wayne Philips, my spanner man at Phoenix, he told me to check the fuel tap. As he suspected, the vacuum hose had come loose, thus starving the engine of go-go juice. A quick fix and we were ready again. Lining up to go out once more I gave a cursory glance to my left-hand side and saw a big puddle of fuel. Guessing that the float valves were sticking in the carb I gave them a knock, but with no joy. It was back to Phoenix to find the problem and (to cut a long story short) with a further call to Fowlers Parts new needle valves were on their way. It had been so long since fuel passed through the carbs they just failed immediately. So here was another delay but in the end this is what testing is for I guess, and as usual it wasn’t long before Wayne had her running again. Since announcing this project I have been in constant contact with a chap called Len Whalin, technical coordinator of the YPMS and a real TZR guru. He is in my corner for the race weekend and has a background which has included time in with legendary GP crew chief Erv Kanemoto, spannering for Mick Grant and aiding ‘Dozy’ Ballington, the nickname of Kork Ballington’s brother who built the engines that gave his sibling four world titles. More importantly than this though, we have become good friends and he suggested I ran the finished TZR over to him for a pre-scrutineer before the Snetterton round. It was an early start to get to Brands Hatch Morgan: Len’s place of work, but I was greeted with a big smile and bacon and eggs sizzling on a makeshift toolbox grill. I knew I would need my strength for a day of tinkering, but what I didn’t know was what Len was about to engage in what could have cost me a four-figure sum if it wasn’t for his eagerness to get me and this bike onto the grid. As an overview it was obvious he liked what he saw: another 30-year-old TZR ready for some Bemsee/ypm action. There were a few things to be done immediately: lock wire the calipers, drain plugs and radiator cap. Another stipulation was an oil catch bottle needed to be on the gearbox breather pipe. Easy enough to fashion and would only find fluids running into it if I was upside down so here’s hoping it won’t be necessary. The clutch was good, and though many will fit heavier springs it’s not always necessary – though if at Snetterton I get clutch slip he would fit them for me. I also need to tie in the kick-start so it doesn’t start to flap about once on track. My notebook was filling up. Fortunately I have the right gearing for Snetterton: 14 teeth on the front, 43 on the rear that should deliver on the straights at Snetterton while giving enough mid-range for the twists and turns on the 300’s infield. We then discussed the exhausts, as you may be aware I am still running standard pipes, though Benjamin (who donated the bike for this project) is convinced that his F3s should be on the bike. Len agreed with the thinking, for a start the F3 pipes together probably weigh as much as half of one of the standard exhausts. However there is no F3 kit on the bike – this is illegal within the YPM stipulations and we also had the manifolds missing. The suggestion is when we get to Snetterton for the test day to fit them and give it a try and see if they make a sizeable difference. As it is the
whole paddock ran standard pipes up until around eight years ago. They should be pretty good for the Snetterton demand for midrange drive and Len noted the sound was like an old friend returning, having not heard standard pipes for some time. With a lost manifold I genuinely thought that the F3s were a defunct idea. However another bike wizard, James Holland of JHS, managed to tool a manifold up on the lathe. The F3 pipes are now an option and as I have a practice day at Snetterton on the Friday they have to be worth trying: especially given James’s efforts. Len then delved into the carbs. Having already asked whether I had changed the jetting, which I hadn’t, he introduced me to why it was so necessary. I had not thought about it really but if you are running premix the fuel is thicker, thus the jets need to be wider. So Len removed the 20 grade pilot jets and put in 27.5s. Bigger jets means more fuel, thus we need more air. The air-box was modified simply by removing the trumpet which will allow more air intake. Here came another ‘discovery’ which has me waking up at night screaming at my stupidity – when I had bought the air-box from ebay they stated “will need a new air filter”, fair enough. But what I failed to notice was that the old air-filter was still present, pleasantly rotting away and from my brief runs had flown through into the carbs clogging up the whole job. So now all back together, Len kicked the bike over and it idled beautifully, those few changes making such a difference and (hopefully) ready for racing. Well so we thought; the slightest drop of water found on the head became a massive concern leading to a further strip and removal of the head. I was pretty sure that this water hadn’t come from the hose as (pre-combe testing) Samco had delivered a bespoke hose to me for the radiator modification I made at the start of this project. Most YPM bikes have upgraded their rads and used a combination of hoses buckled together. However having supplied Samco with the measurements and info they went about making a CAD drawing, a mould and then started adding the numerous layers and liners that deal with the internal pressure and heat. I had no idea that so much went into the building of hoses and good ones are not cheap, but with a lifetime guarantee it’s a sensible investment. So with the head removed Len looked at the skim that had been performed on the head to increase compression, thus power and decided to ‘test the squish’. There should be a clearance of about 0.8mm between the piston and top of the head. As it was we had 0.45, thus as the con rods had expanded with the heat the pistons would have started to make contact with the head. All of a sudden not getting out at Castle Combe was actually a very fortuitous result. The engine had been supplied to me as rebuilt and perfect but obviously this was not the case. Based as we were at Len’s place of work a lathe was present, thus he managed to rectify the problem, though had we been at the track we could have fitted a double gasket which have been an adequate temporary fix. Having spent eight hours with Len I left with a couple of further pointers, needing a kill switch and a slight shave off of the back of the front caliper which was just that bit too close to the wider wheels for the scrutineers’ pleasure. Then it was back to JHS and James who took to the task and also aqua-cleaned the whole mechanism, including the levers and master cylinder. What a lovely job he did too. So this leaves me here, about to make my way to Snetterton for a free practice day on Friday then racing on Saturday and Sunday. The bike may look like my son’s bedroom door but every sticker present is from someone who has helped me with this project. I owe each and every one a debt of gratitude and will get round to it. But firstly I owe them as good a performance as I can muster at Snetterton for the finale of this, my Fast Berk project. Fingers crossed.