Skip to main content


Leak Down Testing on a Lambretta

Mark(UK) performing a leak down test on a Lambretta TS1 238 cc engine with his custom tool. Many thanks Mark and I hope everything goes well with your project.

Recent posts

Yamaha DT200R 37F '86, YPVS Curve

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.

Nsr250 PGM Key Ring

A low budget birthday gift for a friend...

CR125 HPP, Altering the Exhaust Valve Timing

A recent modification on a '98-'99 Cr125 bike that alters the exhaust valve timing. A simple spacer made on the metal lathe that adds some preload on the governor spring hence retarding the engagement with the exhaust valve linkage. This mod can help for enduro use or with bigger carbs.
I mostly followed the instructions from the below link though I made the spacer slightly thinner at 2mm thick.
Link at :
Honda 125 - HPP setup TIPS & TRICKS & TUNING @

YPVS repair, Yamaha 34X IC chip transplant

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 among things th…

Piston, Drill Lubrication Holes

A couple months back I installed a fresh top end on a friend's bike, a '99 Cr125. The piston came without lubrication holes at the exhaust side. So, I thought it wouldn't make any harm to add a couple holes, quite the opposite I reckon.

The piston was temporarily placed in the cylinder with the piston ring just above the exhaust port roof and the exhaust bridge layout was then scribbed on the piston skirt.
Two marks were then punched on the piston, from memory it was about 8mm and 18mm below the piston ring. The punch marks were then spot drilled on the Dore Westbury miller and then drilled through with a 1.5mm drill.

The holes seem a little bit too large due to the chamfering. A drill of 1 or 1.5mm is adequate enough for this modification. 
For more info on the subject, check out this older blog post - piston preparation
and also this nice article from the Wiseco blog - relieving the exhaust bridge and drilling lubrication holes

Honda Cr125 Water Pump Shaft Repair

I've been recently working on a Cr125 engine and the water pump shaft was in bad shape and didn't seal properly.
The gear is a press fit and can be easily removed from the shaft.
Two different ways come in mind for repairing the shaft. One is to turn down the diameter of the shaft and press fit or loctite a sleeve with the correct dimensions. Instead, I just tig welded the shaft with stainless wire (ER308 type, don't ask if it's the correct rod, it's the only one I had laying around).
Then comes the lathe, turning the shaft diameter to it's correct dimensions.
And here is the end result, ready to be installed on the clutch cover and hopefully serve for a few more years.
Here are the dimensions, please note that this is for the CR125R 1998 model ONLY!