hello to you all. just a quick profile of myself .started track racing a couple of years ago when i turned 60 .currently racing a 1987 tzr 250 in the classics .now my question is i have also imported 1988 1kt from japan .i thought that it would be the same as my 87 .but it has wider rims, chrome bores and a extra exhaust port this looks like its stock factory mods.does anyone know anything about this model.thanks
Hi. I know lots about the 1988 TZR250 2XT. I race mine in Australian P6 Historic Road racing. It is heavily modified. I have converted most of the parts book to english.
hello mboddy . ive just got my 87 back from the workshop . (new crank pistons the head ported to uk specs and expansion chambers fitted .ive been for a couple of rides around the back roads to run her in .get on the track in early feb to see what she can do any way great to hear from someone with history with regards the tzr 2xt what mods have you done to get the best out of her.mine will only be used on the road as she is in such great condition (10,000kms) that it would be a shame to drop her in a race .i will try to get some pics of both bikes to upload . and im across the ditch (nz)
Lots of info on my 2XT and modifying TZR250s on this TZR Forum post: http://pure2strokespirit.net/forums/index.php?topic=175.0 I just write the following for you. It doesn't include engine stuff yet, pipes, fairing etc. More to come. My TZR250 2XT F3 race bike is the best road bike I have ever ridden. This is because in modifying it I have stayed true to the vision of those who designed it. Most motorcycles are designed by a committee. The TZR250 1KT was designed by the YEC race team that designed the YZR500 GP bike. They used the geometry of the JJ Cobas which was the best handling 250 GP bike. Any modifications need to ensure that the weight of the bike remains minimised, particularly if the weight is unsprung or rotates. Any minor weight increase must be critically assessed to ensure that it is worthwhile. Parts on the 2XT that are heavier are the wider wheels, thicker front axle, wider radiator. All these parts can be justified. Also heavier on my bike is the Wilbers 631 shock with remote reservoir with high and low speed damping adjustment. But the overall weight of the bike is under 100kg. With such a light bike it is very important to minimise the unsprung weight. The carbon fibre front guard weighs 250gm including the bracket. It is held on with cable ties. The GP3 slick tyres are very light. The front wheel is 2.5” from a TZ125 but is only for the track as it is too light for a street bike and could be bent by a pothole. Hollow brake caliper bolts from a YZF1000 or aftermarket titanium ones. Twin disks are unnecessary, in fact the front disk could be reduced to 300mm because the bike is so light. USD forks would increase the weight and so the Andreani cartridges were fitted instead. They are fantastic. The swingarm was replaced with a delta box swingarm from a FZR250 3LN which is stiffer around the pivot but lighter overall due to the delta box shape. It is connected by a 3MA linkage narrowed 1mm each side via custom tie bars. Brembo rear caliper is half the weight of the original Yamaha and is attached via a custom 6mm alloy plate. Brembo rear caliper got 11mm Brembo master cylinder to match. Alloy sprocket and light weight race chain. Alloy wheel spacers.
What is a Yamaha TZR250 2XT? Yamaha showed the TZR250 1KT at the 1985 Tokyo Show and it went into production in 1986. It was a very expensive bike for a 250 and was a serious race replica style bike. Matt Oxley used it to do the first 100mph lap of the Isle of Mann on a 250cc road bike. A Formula 3 kit was produced by YEC (Yamaha Engineering Corp) for Japanese F3 racing. A full F3 kit contains lots of upgraded parts including close ratio gearbox, crank, cylinders, pipes, head, carby jet kit, ignition, YPVS controller, tacho and wiring loom. A top fairing and screen that is low like a TZ, seat, reasets, etc. Yamaha sold the 2XT for 9 months in 1988 in Japan only to provide an upgraded base for F3 racing, It had wider wheels to suit the then new radial tyres, 15mm front axle (up from 12mm) with forks modified to suit and a bigger radiator with a new subframe to suit. Carbies updated to make them easier to do the F3 primary style needle jet modification. Ignition was digital with integrated YPVS controller like the TDR250 and later R1-Z. Cylinders were Nickosil plated with two exhaust booster ports per cylinder. New pistons and the piston rings were coated with titanium nitride. New top crankcase incorporated the housing for huge 8 petal reed blocks easily suitable for 36mm carbies (or bigger). There was an updated F3 kit but I have never seen one. I do have the 2XT F3 kit manual though.
My TZR250 2XT F3 race bike uses the unmodified 2XT crankcases, reed blocks and reeds. NZ Cylinders stripped the Nickosil from the cylinders, bored them to maximum allowable for the class and then replated them to fit the Wossner DT125R forged pistons. The cylinder head is skimmed 0.6mm which suits the VP Racing Fuel Roo99. The crank is from the F3 Kit. Carbies are 34mm Powerjet Lectrons machined down to fit in the 2XT inlet manifolds which are opened up to suit. With bigger manifolds I think it would work with 36mm Lectrons and maybe 38mm. Stan Stephens ran 35mm PWKs on his. It would be great to try some 38mm TMXs with Powerjets if we had a lot of dyno time. Gearbox is close ratio from the R1-Z. It is nearly as close as the ratios from the F3 kit but has the later durability modifications. I had JP Mestre contact the HPI factory to build the custom ignition. He also made the stator backing plate. The rotor is 1.1 kg lighter than stock so it revs up very freely. Exhaust pipes appear to have the same specs as the F3 kit pipes but with a round profile rather than oval. Exhaust manifolds are based on the Dog Fight replicas for the 3XV. I spoke to Martin Johnson who makes a couple of different spec pipes for the TZR and he said that the extra boost exhaust ports in the 2XT cylinders bring the revs that it makes peak horsepower down by about 400 to 500 rpm which is probably why the F3 Kit dimensions work so well. So his high rev pipes would be best. Silencers are Tyga which Martin uses too. Dan Williams at Gecko Motorcycles in the UK is also a 2XT fanatic. http://www.geckomotorcycles.co.uk He has dynoed his 2XT F3 with a lot of different pipes. The YPM guys like the Jolly Moto pipes but they have to use the stock 28mm carbies. When I dynoed the 2XT engine in my TDR250 with Jolly Motos it made 56hp at the rear wheel but seemed really strangled and wasn't making use of the larger carbies. I didn't get the 2XT on the dyno before MotoGarage moved to Queensland but I estimate it has 65hp or more as the TZs don't run away from it at Eastern Creek. It is alright at 6,000 rpm and by 7,000 is making good power through to 11,500 where I normally change. If I hold it to 12,000 it is still strong and seems to want to keep on going. The F3 Kit manual advises not to exceed 14,000 rpm or you risk damaging the engine. I like to have long crank life which is why I normally only take it to 11,500.
thanks for all that intel mboddy.it looks like you have a bloody rocket to ride !!!!! and all the best for next year. well it looks like i fluked a tzr with a lot of potential .but i will see how the mods go on my race bike before i make any decision about the 2xt .at this stage she is such a blast to ride on the road that she may remain stock apart from the pipes.
You might want to check your 2XT exhausts. I have a vague recollection that they may have had a restrictor welded into the header pipes. If you take it out you should check the jetting. Any engine or pipe changes you should jet richer and then come back down until it is right. What exhausts are you looking at getting?
