Two Stroke Racelab

Excellent craftsmanship and a work of art on two-stroke exhausts. Visit Tony's(UK) site at tonygreenracing.com

Time goes by like a two stroke motorcycle and this blog is now six years old. Cheers!

Today I was working on a Yamaha DT200 YPVS controller, that belongs to Joel(NZ). This curve opens the exhaust valve at 4.620rpm and the cycle is completed at 8.640rpm. If you check the blog post that I did a couple days back, you may notice that Yamaha uses the same closing time for the 125cc model as well. Though the curve starts opening the valve earlier on the bigger capacity bike. This is something to keep in mind when tuning other bikes as well. It does help to use an exhaust valve curve that delays the opening of the valves on bikes with weak mid range or tuned for higher revs.  Here is how to set the DIP switches.

I have repaired and modified a YPVS controller for Kire(DEU) and found yet another one YPVS curve that was previously unknown to me and might be a good suggestion for all 125cc bikes, including the TZR125 models. This curve is opening the exhaust valve at 4.800rpm and the cycle is completed at 8.640rpm. Here is how to set the DIP switches. P.s Check the below post for another one DT125 YPVS curve. DT125 LC MK3 '87, YPVS Curve

Some boring photos of a Yamaha WR200 carb. Normally this work should be done on a 4-jaw independent chuck. I've used shims and took the carb countless times out of the chuck as to achieve the smallest runout. Then I bored the carb from 29.2mm to 31mm. Normally, the carburetor should be offset as well, as to remove the smallest amount from the base that the carb slide fits.    

It's 04:00 ante meridiem, listening to BBC Radio 4, drinking Ouzo and working on Richard's(UK) YPVS constrollers, how surreal is that? One unit needed a repair job and the DIP switch modification, for the other one I was asked to just do the modification job. Both YPVS units are now ready for posting back. Sometimes I need to do some kind of repair jobs, an electronics engineer wouldn't approve. This YPVS controller I received had some previous bad soldering job and a few damaged PCB traces  and I was forced to use somewhat "unconventional" ways to repair it. It is now sealed with PCB transparent protective coating and a bit of black hot stick glue to absorb any possible vibrations. It will last for a long time, if not forever.   The wiring loom fitments on these YPVS units were modified with water resistant plugs but I don't have enough info on that. I didn't liked them at first and I was a bit frustrated on how to thoroughly test the units bu...

Leak Down tester kits for the Yamaha TZR250 1KT - 2MA & TDR250 bikes, can now be purchased via my  online store. The leak-down tester is an essential tool for any high performance two stroke engine. This kit is installed in place of your carburetor and by pressurizing the engine cases you can check for any air leakage due to worn mating surfaces, erratic torque values due to aged parts, worn crankshaft seals etc. It is a necessary evil that it will help prevent catastrophic damage to your engine and keep performance up. A very valuable tool for a two stroke engine, handmade with care. Directions of use:  Testing can take place after a newly assembled engine to verify that everything is leak free, on a bike you just bought and you need to check crank seals condition etc. Place the tool in the carb manifold, seal the cylinder head with a normal spark plug and seal the exhaust flange with the included CNC exhaust blank plug. Pump the en...

A few months back I made a custom leak down tester for Jason(UK) and here are some photos that I received and wanted to share. Jason owns a Banshee motor with Athena 421cc cylinders and used to have constant seizures on LH cylinder and needed to verify that there is no air leakage on crankcases, oil seals etc. Hi Nick, You did me a special leak down tester for my 421cc Athena Banshee last October. Your kit fitted perfectly and I had zero leakage - actually gaining a bit of pressure after 7 minutes due to a little air bleeding back from the second cylinder through the labyrinth seal after I had taken the pressure a little over 5psi and then used the needle valve to set it to 5psi exactly. Thanks again - I am delighted. Jason      And here is Jason's bike. 

And here is the final part on using a wet clutch basket for a FCC dry clutch conversion. I installed the clutch basket on the lathe and just did a simple "boring" operation. The FCC basket had a clearance of about 0.5mm with the backplate, so this was not really a critical job and it was easy to aim for a tighter clearance as well.  And here is the result after the boring job... The backplate is now a nice and tight fit and everything looks good. I've also used the cushions from the WET clutch basket as they fit perfectly. I don't see why Honda may have used separate rubber cushions for a dry clutch. One thing to note though is that due to exposure to high heat and no lubrication, they become very stiff and fragile while the wet clutch cushions have normally a more prolonged life. I didn't bother with making or buying new rivets as well. I just used a tap to thread the existing holes. Just out of memory, I believe it was a M5 tap that I us...

I repaired a TZ250 YPVS controller today that belongs to Dale(UK). It's from a 1987 TZ250T model and I came across another one unknown YPVS setting that I'm sharing below. This setting doesn't seem to do a lot and it's more like an "on-off" switch for the exhaust valves, as it starts opening the valves at 7.500rpm and it completes movement at about 8.000rpm. And here are a few photos from Dale's bike. Cheers.