Yamaha RD 250 Take Two Engine Reassembly 

I had a RD250E in 1981-82 in yellow. Loved that bike. It achieved 105mph over a flying mile at an airfield with mild tuning and slight gearing change, those were the days! And now I can really appreciate the mechanicals of the bottom end and gearbox with the horizontal split cases, so easy to work on. I would love to get another one and do a few updates, like halogen headlamp, uprated forks and shockers, twin discs with more modern calipers and replace that silly swinging caliper on the rear, that on my bike kept sticking on slightly. I'd try to made them sympathetic updates, like keep original colours of brake calipers and rear shocks so it looks standard. Thank you for your series of video's, I am re-living my youth through them, as I will probably never get an immaculate 250E in yellow.

Love your work, and your patience! Thank you for making these videos!!

Coming along nicely. Redoing stuff is a drag, but that's how we tend to learn. Looking forward to the next session.

Ohhhh what a ball ache having to repeat the process, easily done though, at least you found the reason for the locked gearbox pretty quick, lets hope the worst is over and the rest is planesailing you have done well !!!

good progress ! excellect you sorted the gear box out before fitting ;-) I've been doing my timing with the cylinders heads off mainly because I lost my screw dial gauge for the plug hole (!) . I can visibly see the TDC that way but I aknowledge that virtually everyone else does it with the cylinder head on . I still have points system as I've still not found an electronic kit for a Suzuki GT185 . Looking forward to the next episode , fingers crossed all goes smoothly from now on !

Once you verify timing marks on your rotor, you can use a timing light that has a two stroke setting that also you can “0” out the advance setting. I bought one and setting points and timing on my RD 350 went from stupid fiddly to a 10 minute job. You can get your timing spot on without hassle. I got mine at the Home Depot believe it or not. Works great.

Well done mate so far so good 👍

The RD 250 was an excellent Bike iconic my little brother bought one new his first road bike awesome little machine hope you have the body work

Best extension in the dial gauge is a bicycle wheel spoke, the threads are the same and on the other end you bevel cut the spoke with a hacksaw and file finish so it cuts through any crud on the top of the piston to the metal. Be careful not to punch out the dial gauge mechanism when trial and error finding the correct spoke length...

I’ve said this before but I would strobe the Vape once the engine is running to see where on the pick-up it’s actually firing. The manual states it fires when the nose of the magnet passes the edge of the pick up nose but in my experience it’s often closer to the middle of the pick up.

Very good .

Well done mate it may seem a bit of a pain having to re do it but you will look back with satisfaction and enjoyment cheers for now c u in the next one 👍

As you've had the crank rebuilt. I would always check the TDC positions of both pistons, using the dial gauge. This should ensure that both pistons reach TDC at exactly the same time. It might sound mad, but the slightest misalignment of the crank MAY mean one piston reaches TDC, before the other. This is very unlikely, but it always pays to be cautious, as fractions of a millimetre can make a difference in timing. If one piston reaches TDC, before the other. Then you need to time off the piston that reaches TDC last, to be on the safe side. This ensures that the first cylinder will be running on very slightly retarded timing, compared to the other. I have seen various advance settings from 1.8 to 2.0mm BTDC, for these old air cooled motors. If you're not bothered about the maximum possible power, then maybe consider retarding the ignition timing slightly. This will help further negate any detonation and give slightly better low end power.

Nice to see ya back. By the time you have this done you could set up a very good bussiness rebuilding RD engines 😅😅😂😂Only joking . I know its no joke when this happends. This is whats happening with me at the mo. I am rebuilding a CBR1000F and now need to buy a cam chain . The other bike that i am working on is a Kawasaki 550 and am now re builing the carbs ooooooh i hate carbs. Great job keep up the good work . Great stream 👍👍👍👍

With regards to the ignition timing what you have done is OK 'but' really you should turn the engine backwards until the piston is say 3mm BTDC then turn the engine in its normal direction of travel to bring the piston up to 2mm BTDC. Doing this will take out the tiny amount of slack that you get in the big end and little end. It probably won't make much difference but its 'good practice'

great job lad glad u figured your gearbox out easy fix next video please

Why did you strip the top end instead of turning the engine upside down and accessing the gearbox by removing the lower engine case ?