Yamaha RD250 Disaster Rebuild

[@richardsouthey430]

Looking good , it will be nice to hear the engine start ,after the rebuild. Richard

[@RepairandRideout]

Hi Richard, I can't wait either. I do love a two stroke!

[@Pokemongold88]

Weather looks great for a ride out soon as the rd is boxed up ,not long now hope it all goes ok👍

[@RepairandRideout]

Thanks, a really nice day today. Back to 6c tomorrow. Might have to put some heat into the garage

[@the_forbinproject2777]

opefully thats a reboring company chamfered the ports - with suzuki theres a 2 step process for the that - stops snagging rings. . Another great update and looking forward to the next expisode - don't forget - better slightly rich than lean (!)

[@RepairandRideout]

Just collected the cylinders and they have chamfered the ports. Good engineering company, Sebastian knows his stuff

[@MX-fo2nu]

Looks good and why not have a Look for Port and match. PISTON lower Shirt is to wide on both sides but must be wide enough over/wider the Ports ; and a hole e.g. 6mm above the 2 membrane inlet holes and below the rings cooles the piston Head from the inner side of the piston and supports the spray of the 5th transver. Have a Look in the Internet. If you wann to use it upside the road on the track.

[@RepairandRideout]

Thanks for all that info. I don’t have the nerve to do it myself

[@deedahinkent]

So far so good mate not far to go now being very meticulous will be worth it in the long run ,great video hope it all goes well 👍

[@RepairandRideout]

Thank you. Taking it slow and steady. Hopefully I'll get it right first time?

[@deedahinkent]

@@RepairandRideout The only way , looking forward to hearing that lovely exhaust note!🎶👍

[@sidecarbod1441]

I would not worry about port matching the transfer ports if the rest of the motor is 'stock' You will probably find that they are matched fairly well anyway (you know what that Japanese are like!). If you were going to 'port' the rest of the engine and work on the heads then yes you do everything you can to gain BHP but your not doing that, I believe. As others have said, make sure that the ports have been chamfered, if not do it yourself.

[@RepairandRideout]

I wonder if it's a necessary step, it might just complicate things if I get it wrong. Lets see.....

[@sidecarbod1441]

@@RepairandRideout I doubt you would get it wrong, you can use a base gasket as a template, its probably just not worth the bother, having said that it will only cost you some 'time' and nothing else, if it makes you happy, go for it!

[@gk73man51]

I don’t know why they fitted those silly o-rings with the block. The early bikes don’t have them. Castellated side of the lip seal faces the bearing to space it away. Remember to check squish as well. Port matching won’t give you any real benefits on an otherwise stock bike but if you have the tools to do it then why not.

[@mickmc3250]

Funny you should say that! I have just rebuilt my 250E motor and couldn't find the seal on the exploded parts diagram so I didn't fit one!!! I stipped the engine over a decade ago so can't remeber if it had one or not.......do you think I should put one in anyway to stop the crank swimming in gearbox oil???.....I hope somone see this and can advise!

[@gk73man51]

@@mickmc3250 E parts book doesn’t show it, I assume they went back to the original end web design for the E and F. www.aircooledrdclub.com/manuals/250400E.pdf

[@RepairandRideout]

Thanks for your advice. I'll look at the port matching, it depends on my nerve when it comes down to doing it

[@RepairandRideout]

I didn't know it was there either. I was looking through the Yambits parts list for the rebuild when I saw it listed. I had no idea what it was so I had to go and check to see that my engine had one. I could just about see it, so I thought I'd better get one! @@mickmc3250

[@colinculverwell325]

The primary gear o ring was fitted to the C/D model but not the E/F. Looks from the parts list that it was also on the A&B models as well and I have found them on all the cranks I've had up to the E/F. I've never been able to see why the later models didn't have them. The primary side of all the cranks is the same design. Maybe someone knows?

[@RepairandRideout]

Strange? On reflection it can’t be the source of the air leak as it is inside the oil filled clutch cover.