CBX250RS-E Engine Rebuild 09/04/2012

And so, upon further inspection, the new cams are different to the old ones. The old ones are larger in diameter by 1mm and the bearings that are on them have a diameter 1mm smaller.. The new cams with their larger bearings were never going to fit. This is quite a downer, and I can't understand how this would be the case when the new cams are a superceded part, but they're just not going to fit without major work.

I shall refit the old rockers and cams for now and figure something out at a later date, at least it'll run for a bit.. It's not going to be how I'd like it though :(

The old cams have bearings with a 20mm inner and 37mm outer diameter, making them a normal 6904 bearing. The newer cams have bearings with a 19mm inner and 38mm outer diameter, which is not a standard size but can be found. I did have a quick look for bearings with a 19mm inner and 37mm outer but I can't find any, though maybe they exist somewhere.. I do wonder if they could be got from Honda as a sort of conversion kit? It is quite possible they are imperial, but I don't have anything precise enough to measure tenths of a millimetre. The bearings themselves have SC0481C3 written on them if that helps, and of course they are from NTN (or at least I think they are).

The past few days have been very busy, with the old stuff fitted back on it was time for all the other stuff to be put on - carbs, airbox, wiring, all faffed about with. I did have an issue with one of the bolts for a cam holder not torquing down properly but it seems to hold it okay. In fitting the rocker cover I came across an odd problem - the manual clearly states that the spring for the small bit of tensioner should go around the bolt, but if it were there the gasket for the cover couldn't fit..

I just curled the spring around the casting instead, it certainly looks more like where it should go. I also fitted a brand new oil pipe to feed the top end, filled the engine with oil from the head so everything at the top was sitting in a pool, and feverishly plumbed it all in. at around half nine tonight the tank was on and it was time to go.. It turned over about 6 times and gave a pop. A couple more churns and it came to life! I was happy for about 3 seconds until I noticed the odd, off beat knocking of metal on metal.. It's almost like a large version of gear chatter. My Dad reckons it's the cam chain, I reckon it's something to do with the primary drive or the clutch. More revs make it louder and more often though, whatever it is. Otherwise it runs fine, no smoke or death rattles, but this knocking is something of a let down. It doesn't even seem to leak oil!

I'll take the clutch cover back off and look for shiny bits, but I really don't know what it might be :(