Yamaha RD250 Engine Rebuild Doesn’t Go To Plan

[@georgemalkin6546]

Joys of working on bikes, i think we have all been there, life is a learning experience. Bonne chance.

[@RepairandRideout]

Thank you. Character building I’m sure😂

[@the_forbinproject2777]

ah one of those things with the gear box , dont feel downhartened though because you did check before putting it into the frame ! I have always fitted pistons when they are TDC as that allows me to put a cloth over the crank hole so as to prevent debris and circlips falling into the crank case (!) . Twins I insert the inner wrist pin circlip first before fitting to the conrod ( like wise rings like you did ) then push the pin through and then fit the outer circlip. The extra room at TDC allows me to keep a close eye on the pistons rings making surre they stay in place with the retaining pin in the piston - sometime they ride over if you're not careful . Looking forwards to the next espisode ! thanks

[@RepairandRideout]

I was too concerned with using the circlips just the one time and lost sight of other details. You live and learn 😊

[@Kev-N42000]

Oh man that sucks lol, I usually run it through the gears with the top case half off, that’s what’s nice about them motors

[@philallen3261]

Really enjoying your engine rebuild well spotted so deep breath have a coffee then off you go again looking forward to your next video 👍👍

[@RepairandRideout]

A bit of a set back but at least the engine wasn’t back in the frame

[@cbrider726]

I put the pistons the cyclinder first than mount them on the con rod . Just to make sure that i dont damage the rings as new rings can be a bit tight . I also lube the pistons with a bit of light oil .Nice job. We all have suffered disasters during engine or gear box rebuilds . But we just keep on lol. Love your streams 👍👍👍I feel your pain

[@RepairandRideout]

Thanks for your help and support, much appreciated

[@Scott-ph2yk]

A minor setback on the gearbox. No damage done, but a good learning experience. Hang in there, you will get her done up, right.😊 Your leak test set up looks good. I would suggest two things to add. 1. Use a spray bottle of water and a little dish soap to spray on the engine points where leaks can occur. If you get bubbles, you have a leak. Much better than relying on hearing and air pressure alone. Make sure your air pressures holds for 15 minutes without dropping. 2. Reverse your intake plugs and rest from the opposite too. Test twice, always nice. On assembly: Good job oiling with 2 stroke oil as you assemble. Just right, not too much oil. Things to consider: Apply a thin amount of 3 Bond to your cylinder base gaskets, and your carb intakes. These are notorious for leaking air. Testing your piston to head squish clearance. This can easily be done with pieces of solder taped temporarily to the pison crowns, in a cross pattern. You simply cycle the engine around a couple of times by hand, then remove the solder, measuring the crushed portions with your calipers. Compare your measurements to the shop manual. If you are in the range of success, bravo. If not, then investigate and correct cylinder torque down and head gasket. Way better than ruining a piston or two. Final thought: Since you gave to reopen the cases, why not check your shift shaft to make sure she is good to go. 1. Check the spring on the clutch side. They sack out over time. 2. Check the shaft for straightness. No bends allowed. 3. Check the final drive side for shaft abrasions that will tear up the shift seal. 4. Check the engine case where the shift shaft comes out on the final drive side. This should be tight, with no slop. Over time this can wear causing leaks along the shaft and poor shifting. Later model RD's have a small pressed in bushingbetween the shaft and the engine case, which can easily be replaced. If your cases do not have the bushing, you could add a bushing by boring out the case opening, or fitting an external bushing kit that contains a replace-able busing and seal. The external option is available in the UK from RDLC-crazy, also known as Norbo. You are doing great with your rebuild. Do not get discouraged.😊

[@RepairandRideout]

Thank you for taking the time to write such a detailed response, I really appreciate it. I’m sure others will find it helpful as well.

[@Scott-ph2yk]

@@RepairandRideout My pleasure. I just went through an engine rebuild on my YPVS 350 a couple of years ago. Aside from the power valve and the water cooling, the RD engines are the same. Way back when, I had a '74 air cooled RD. Suffice to say, RD's hold a fond place for me. Glad to share where I can. Looking forward to seeing your RD back on the road in your videos. Updating my rear suspension and brakes this Winter. Getting ready for Spring here in the USA.

[@mikekilbride]

Ahhh I really feel for you. You are doing such a great job andits frustrating but dont let this get you down to much as you will have a great bike when finished

[@RepairandRideout]

Thanks for your support

[@cambo1200]

This is why I do a dry fit and test to make sure I don’t mess up anything.

[@deedahinkent]

Patience is a virtue mate well done for staying calm ! c u next time.

[@RepairandRideout]

I managed to keep my inner Basil Fawlty in check

[@paulb1034]

Not necessarily, check the selector pawl on the end of the selector shaft at the clutch basket side, it may not be correctly centred on the pawl of the selector drum, removing the clutch basket will allow you to withdraw it slightly and centre it on the drum pawl

[@gk73man51]

Indeed. More likely to be the shift mech than the cluster itself.

[@RepairandRideout]

I’ll have a look but I fear it’s all got to come apart again

[@peterlobb6456]

We all feel for you! Chin up, have a cup of tea and re-group :) It'll be worth it in the end,

[@RepairandRideout]

Cheers, just a small set back in the scheme of things

[@DaveHines1]

As soon as you said “diligently” I knew something was wrong 😃🍻

[@RepairandRideout]

Rather set myself up there didn’t I

[@markaddy53]

been there done it lad we all make mistakes keep at it ul get there

[@RepairandRideout]

Pleased to know I’m not the only one

[@shaunhardie6077]

ARGHHHHHHHHHHHHHHHHHHH, what a bummer, hopefully you get it sorted, 🤞.

[@RepairandRideout]

Not enough attention to detail!

[@viggowiberg]

Got and RD250 1974 im currently working on and I was just wondering where you bought the pistons from? Greetings from Sweden :)

[@RepairandRideout]

Hello! I brought the pistons from Wemoto, the French site. Good luck with your rebuild

[@paulstokes393]

I feel your pain 😖

[@RepairandRideout]

Cheers, I’ll get there eventually

[@martinowl]

If it turns out you need to split the crankcases, do you definitely need to remove the heads & barrels? Hidden bolt(s)?

[@Scott-ph2yk]

On a Yamaha RD, yes you do need to pull everything. No short cut here.

[@martinowl]

Fair enough. Cheers for the reply.

[@RepairandRideout]

I think so. Never mind

[@MX-fo2nu]

Good luck you will manage

[@sidecarbod1441]

What a bummer! I must admit that I'm finding it hard to imagine what you have done wrong. Anyway look on the bright side, if you had not checked and just fired up the engine you might have destroyed the gearbox,

[@RepairandRideout]

Thank, you’re right it could have been much worse

[@samjoentess9168]

Doh !!

[@RepairandRideout]

😂

[@SwPiotrek]

Annoying, but would be great to only have problems like that.

[@RepairandRideout]

That’s so true