If you have an old rotary valve engine that deserves to be restored
contact me. I am really good at it and very particular.
100cc Air Cooled Rotary Valve
Stroke: 48.5mm
Rod length 96mm
Bores Size: 50.7mm
Piston Size: 50.61mm
Clearance: 3.8 thou
Exhaust = 168 deg
Transfer 126 deg
Boost = 126 deg
Valve close = 64 deg
Valve opens = 124 deg
RV clearance = 12 thou
End Play = 10 thou
Timing = 2.1mm
Squish = .9 mm
Combustion chamber = 7.1cc
Compression Ratio = 14 : 1
RPM limit 17,500
Stroke: 48.5mm
Rod length 96mm
Bores Size: 50.7mm
Piston Size: 50.61mm
Clearance: 3.8 thou
Exhaust = 168 deg
Transfer 126 deg
Boost = 126 deg
Valve close = 64 deg
Valve opens = 124 deg
RV clearance = 12 thou
End Play = 10 thou
Timing = 2.1mm
Squish = .9 mm
Combustion chamber = 7.1cc
Compression Ratio = 14 : 1
RPM limit 17,500
In 1975 this was DAP's flagship homologation. Brand new model. A
deviation from the long stroke T70's. At a time when IAME, BM, Manx
and others were rushing to short stroke engines. However, DAP made a
critical error that ruined this engines reputation. The new 96mm
DAP I Beam rod failed instantly, pretty much in every engine.
Shame. It was easily as quick as a BM K96 or Komet K78TT with more
cooling. In late 1976 I had the choice of 2 DAP T80's for the
price of 1 Parilla, BM or Komet. I took the two DAP's. I liked
the idea of being able to screw in the high jet with greater
certainty. After a 40 minute run in both engines broke conrods at
the first full rev.I had been warned. No problem. I put 2 IAME knife
edge rods in and they were fine. Because the rods failed at
relatively low rpm's no other components were damaged. Neither
engine ever failed again. I ran hard for the next 12 months winning an Australian Championship, (Junior International), an
International race meeting at Orange (100cc International, Canobolis
kart prix) plenty of trophies at all sorts of meetings in 100cc
International senior, club championship and on. On the front row for
the final at the NSW champs in Gilgandra when the chain came off.
Real shame as it was the quickest engine on the day. This sub
standard conrod set DAP back for years.
I took to my Championship engine. Higher and wider exhaust, bigger transfer with bridge removed, 2mm enlargement of the intake transfer and 4mm enlargement of the ignition side, big valve timing. Everything squared, matched and polished. It was quick. Boost port engine that out ran all the TT's of the time. I was also a quick driver on a fantastic Deavinson chassis. That helped. I ran the standard engine at club level and won everything. It was beaten once (just) by Howard Heath running the latest factory Parilla TT23.
This engine has a knife edge rod that seems exactly the same as the IAME rod. Safely assume they came from the same supplier. I am tempted to take to this engine and run it. So far I haven't. Its almost irreplaceable as a New kart engine approaching 50 years old.
I took to my Championship engine. Higher and wider exhaust, bigger transfer with bridge removed, 2mm enlargement of the intake transfer and 4mm enlargement of the ignition side, big valve timing. Everything squared, matched and polished. It was quick. Boost port engine that out ran all the TT's of the time. I was also a quick driver on a fantastic Deavinson chassis. That helped. I ran the standard engine at club level and won everything. It was beaten once (just) by Howard Heath running the latest factory Parilla TT23.
This engine has a knife edge rod that seems exactly the same as the IAME rod. Safely assume they came from the same supplier. I am tempted to take to this engine and run it. So far I haven't. Its almost irreplaceable as a New kart engine approaching 50 years old.
