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What should the cylinder compression be on a 1966 Yamaha 100cc twin jet motorcycle?
I remember these lightweight steeds that had an almost cult following in the UK, resulting in a large number of tuning parts becoming available at reasonable prices.
The noise of a gaggle of them pulling away from the lights all at once could and did break the windows of nearby houses.
The compression pressure of an exhaust tuned 2-stroke engine is necessarily quite low - because the cylinder capacity and the compression ratio "grows" at the rpm the reflected exhaust pressure wave effectively blocks the exhaust port and the engine power suddenly increases. Yamaha engines of that time were notoriously "sudden"...
I don't know the exact compression pressure but I would be happy if I did a test and achieved around 100 psi. My Suzuki of a similar design produced 105 psi on the kick starter. Much more pressure than that and there would be a danger of the fuel detonating in the cylinder when the engine "was on the port", usually resulting in a hole melted in a piston.
on Oct 16, 2020
Yamaha neo 4 2011 flash codes 5 long 1 short what is that
I had the same problem with my 2016 neos 4. I had replaced the rear brake shoes and ran the bike for a while while it was sitting o the stand. The issue was simple... the engine management system thought that there was an issue with the speedometer as the Speedo reeds the speed from the rotation s of the front wheel. As the bike was on the stand the front wheel, hadn't turned while the rear one was spinning with the engine revved...
the solution was simpler... SPIN THE FRONT WHEEL, Or take the bike for a ride. Sorted
on Sep 15, 2020
2001 Yamaha 1000 Fazer
I pulled the ignition fuse
there is power coming from BOTH terminals with the fuse pulled !!
I am guessing you checked that with a voltmeter?
A voltmeter needs only microamps but such a tiny amount of current hardly qualifies as power. A backfeed because of leakage from something will register a voltage, especially with a digital meter but I wager there wouldn't be enough current to light a bulb - which is why I mostly use a testlamp for such checks.
Most modern ignition/engine management systems use more than one supply and internal leakage between them might be normal or might be a fault. Reference to a wiring diagram might help. Certainly if both fuse terminals have real power - that wouldn't be normal.
on Aug 20, 2020
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