pop goes the motor 11/10/20

This is a work in progress but as the blog is being written at the same time as I am working (for a change), I thought I might as well publish it to make it a live update of sorts. So do pop back in the future to see when I finally give up and set the lot on fire.

We never thought that 2020's race reason would even happen so when we found ourselves at Cadwell park, all be it as privateers and the sun was out, we were all pinching ourselves. All of the bikes were going well and so something had to give and it was the RD250.

2 laps into race 1 on Chris curve the RD suddenly lost power, regained it then died all together. My EGT and TTO temperatures all looked fine so I wiggled carbs and throttle cables but the engine came back with a noticeable rattle so the clutch was pulled and my race was over.
I had a back to back race on the VFR750 so by the time I was back in the pits, Roy Dale had kindly put my bike on its stand outside the van. We had a look to see what the prognosis was. I suspected cylinder 1 had gone as the carb had popped off in practice but that was clean as a whistle. Cylinder 2 however was a different story.
The pistons bottom had come away leaving the crown stuck at the top of the barrel and freeing the conrod to have a party destroying the barrel in the process.
That was the end of my racing weekend on the RD but only the start of a fair amount of work for me.

Once home the RD was chucked in the garage whilst I got busy finishing off the CBR400RR NC29 engine I had been working on so I had some work surface space to work on.
With that out of the way I spent an hour getting the RD's engine out of the frame and its fluids drained (well fluid, there is only supposed to be gear oil in it).
 With the engine on the workbench it was short work to get it apart and the crank out. This was then packaged up and sent off with another crank I had laying about to Grampian motors who will sort out the mess I had made of that.
Now I had time to breath whilst they magicked my crank back into shape. So far as I could see, it only needed a new conrod and a flush out but we will see what comes back.

I was left with the question of why it failed. The engine had been rebuilt with fresh Mitaka pistons over winter and my temps were all good. Could the piston have failed due to a quality issue? I suspect I had dropped down the gears too harshly into Chris curve causing the conrod to stretch but the new copper base gaskets were also suspects in the engine murder crime. I settled on blaming me for now but remained suspicious of everything else. Time to get cleaning.

And clean I did. With the engine stripped I could now clean out the cases inside and out in the degreaser bath. 

The oil in the gear box didn't look very clever so that was all thoroughly cleaned too with all the parts lubricated after to keep the rust off of them.

Thankfully there wasn't any scoring or bad damage to be found from the piston failure.

Seeing as the cases were clean however, I took the opportunity to weld up some chain failure damage that had happened before to stop any cracks from propagating.

 That was basically as far as I could go for now till the crank and replacement barrel were ready.

On the barrel front I had been hitting eBay to see what was about.

I am running 2R8's which are later air cooled barrels. I bought an earlier barrel from a C/D model by mistake which looked similar at first but on closer inspection, it had a lot less meat on it and very thin liners.

It was then that I remembered I had a set of spare barrels sat in the shed already!

One was dug out and I got busy with a Dremel cutting out all of the rough stuff like bigger stuffer block openings and lowering the A/B bridge before I handed the lot to Racing Green to do the more complex work.

By now the cranks where back from Grampians (they had them back to me within a week to tell the truith!) so I could rebuild the bottom end of the engine. I am pretty well versed at this but I again had to remind myself which way round the oil seals go in on the crank. In the air cooled manual it isn't even mentioned but in the water cooled book it is suddenly imperative which way round they are to hold everything in the right place and deal with pressures correctly. Pictures below are to remind me again for next time mostly.

got a bit excited with the gasket there.

Every time: it's the wrong size! No wait, primary gear shaft.

Something which did catch my eye during the rebuild was the evidence of the left crank seal leaking onto the back of the rotor. Not a huge amount but enough to say it needed changing. Good job I am fitting a new one.

The rotor can be fit properly later when I can check TDC which will require a barrel and some pistons which I am still waiting for from Japan.

Something else I noticed during the inspection stage was that the reeds looked a bit tired. New petals would set me back around £60 but I could get a set of V-force 4 stuffer blocks from Malaysia for £86. The choice seemed obvious to me and they were on my front door in only a week which was pretty good.

With the reed stoppers on the 4's, it might be a bit of a squeeze to get them in the barrel though. I will have to wait and see on that one. Time to cover the engine up and get to work on something else..

11/10/20

With time flying past but thankfully no racing to worry about I have just recieved the barrel back from Racing Green. A few priority jobs have taken priority but I think I will be getting this one rapped up soon if only to get some worktop space back!