Two Stroke Racelab

David(AU) and his journey on restoring a RD500 bike. Thanks for your kind words Dave. 

Two more RD500 bikes will once again ride smoothly soon. Many thanks to Jean(CA) for the photo. 

Many thanks to Steve(UK) for the photo.  RZ500 in the background... 

RD125 1GU YPVS unit repaired and modified for Lars(DE). The exhaust valve starts opening at 6.250rpm and is fully open at 9.000rpm. Have fun Lars. Nick

Many thanks to Paulo for using my stickers on his lovely RZ500 and also in his workshop in Madeira island!!!

Three more YPVS control units ready to leave the workshop. First one is for a TZ250 '84 and two RD500 units.  Many thanks to Nath and Paulo for the photos of their bikes. Cheers. Nick

 YPVS control units for Michael(UK) and his lovely TZR125 bikes. 

 Freshly repaired Rd500 unit for Mark(NZ) and Tzr250 unit for Nick(GB). Both YPVS units repaired and are now in excellent working order.

I just finished the repair of an ultra rare YPVS control unit, that belongs to Dan(UK).  I have repaired quite a few TZ250 ypvs units and also Rz500 YEC prototype units but I had never seen this one. It is an official F3 Kit part for the Tzr250 1KT - 2MA bike. Of course, it does feature it' s own unique racing exhaust valve timings, as to accompany the rest of the kit parts.  You can find the Tzr250 KIT manual, in the below link that is also an excellent resource for all Yamaha 2T street bikes :  pure2strokespirit.net  

A busy day at the lab, repairing four ypvs controllers for Damian(UK) and modifying a RD500 YPVS unit for Daniel(USA). Thank you all for trusting my services. 

There are issues with posting delays lately as a result of both limited air transportation and changes in how postal operators deliver. That said, I always do my best to have any orders delivered back as soon as possible.  Here are a few units that I received, repaired - modified and delivered back within 48 hours. A Honda Rs250 NX5 PGMII for Oliver(GB), a Tzr125 YPVS controller for Simon(GB) and a Rd500 YPVS unit for Tony(USA).  Thank you all for your understanding. Nick

The below ypvs exhaust curve was stock on John's(USA) '86 Rz350 bike. I'm not sure I've seen this curve in the past. The exhaust valves starts opening at 7.000rpm and are fully opened at 9.500rpm. A few photos of John's RZ bike. 

I've been working on some YPVS controllers for Pete(GB), Gavin(GB) and LES(CA) and I just found out a new exhaust valve curve that I want to share. Pete owns a Tz250H converted to an L (electronic power valve). I have a few TZ250 (mostly reverse twins) exhaust valve curves on the blog but the below one is new to me.

Many thanks to Terry(UK) for using my sticker on his magnificent RZV500R bike.

Many thanks to Tom(UK) for the photos of his lovely Tzr125 bike.

I had recently repaired - modified a YPVS control unit and also made a custom SDR200 leak down tester tool for Matthew(UK). The Sdr200 is a unique bike with a Trellis frame. The YPVS exhaust valve curve is also unique to this model.  And here are the YPVS settings, specific to the SDR200 model.

I just repaired a YPVS unit for a Yamaha DT200R 37F bike, that belongs to Tony(UK) and I have another one rare YPVS curve to share. This unit doesn't seem to use the regular DT200 ypvs curve but instead uses the one below. P.s Dt125 and Dt200 owners might want to give it a try.

Another one interesting repair job that got me scratching my head for a while. The below RD/RZ500 YPVS unit belongs to Mark(UK) and needed a repair job to be done. The IC chip was badly corroded and lots of the pins didn't made contact with the PCB due to the oxidation. This is not rare on Yamaha YPVS units but I'm not sure I have ever seen one at this state.  Any attempts to clean the pins and put new solder on them was at least discouraging as the pins cracked in half by only slightly touching them. There are some tricks that can been done as to trigger the circuit from different pins but this proved to be inappropriate in  this situation as well. After hopelessly looking at the YPVS unit for a while, I accepted my defeat and I informed Mark that there is nothing that I can do as to repair his unit.  A few minutes passed by and while randomly searching at my "junk" box, a possible solution caught my eye. I'm not sure why I always find solutions amon...

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