Yamaha XJ 650 Top End Engine rebuild

[@CaptHollister]

I had a 1982 XJ650RJC Seca. The C in the designation identifies it as the ultra-rare Canada-only version. This is the one even most Yamaha experts have never heard about. One apparent difference between my bikes and yours is that mine had Yamaha's YICS system. The first summer, my future wife and I packed our stuff and put ourselves and the bike on a plane bound for England. From there we rode on yto the continent and ultimately Italy. We were in our very early twenties and it was an unforgettable adventure. I ended up keeping that bike for 11 years during the earliest of which it was my only transportation. It even saw some snow storms. We all have that one bike we regret selling, mine is the 650 Seca.

[@pat2bornot2b]

Yes I've not heard of the XJ650RJC, and that a great story and adventure. This XJ is not mine I restored it for a friend and it's been living here ever since as he does not have a good place to store it so it is 'living in my garage' until he gets sorted, when ever that will be. We as motorcyclist alway have bike we regret selling, some for sentimental reasons others because we needed the money at the time or in my case often just stupidity. Thank you for the comment, and what bike if any do you have at the moment.

[@CaptHollister]

@@pat2bornot2b I have a 1976 Honda CB400F which was my first bike in 1979 and which I managed to never sell, a 1976 Kawasaki KH100, a 1976 MotoBi 125 2C which was gifted to me by an uncle in Italy and lives at my cousin's home in the old country, and a 2017 Moto Guzzi California. On the lift in the garage is a 1979 Honda CX500C which belongs to my daughter and which I'm slowly recommissioning.

[@pat2bornot2b]

That's a great collection, here I've a 2001 Ducati monster s4, that is a replacement for my original S4 a bike I stupidly sold, a 1978 Laverda 500 that I rebuilt from rusty bits, a 2005 Suzuki en 125 that I bought for my daughter but I now use a run around and a 2018 Yamaha Niken that got me back on motorcycles after an accident that almost ended my biking. One of the bikes I regret selling was a 2006 Moto Guzzi Norge 1200, a super bike and wished I had kept. I had a lot of bikes since I first started on a Honda CB125 in 1974. I owned a good many Honda, Yamaha, Kawasaki, Aprilia, Moto Guzzi before so a long list. Enjoy the restoration of the CX500 and riding the Guzzi, which I'm jealous of as I love a Moto Guzzi California Vintage.

[@karlvanboxel561]

I had a 1980 xj650H very gd bike a bit of an oversight by mr yamaha tho imo is the lack of tensioner on the alternator/ starter chain which can flap around with higher mileage and cut the oiling nozzle 😮

[@pat2bornot2b]

Thank you I learn something new every day.

[@godzonerefections]

Nice rebuild well explained. Have recently purchased an '83 XJ650 done 140,000km and not ridden since 2015 according to WOF records. After some days reorganising and replacing some parts I have started it and sounded okay but wont run after a few revs. We have good spark on all but centre cylinders don't appear to be firing as opposed to the outers as the plugs remain clean. The centre cyls are 90psi and outer at 110 and 120psi. Assume it might be valves not seating - your thoughts?

[@pat2bornot2b]

Thank you for the question, my first reaction would be to look at the carbs.Have you replace the jets as the one in the video that jets crumbled when I set to replace them?

[@johnrenehan7406]

Id also check all valve clearances All four must have good near recomend ed gaps Second , run the engine for at leadt 20 mins - under load if possible Then re do the compression test with throttle pegged full open Should be above 130 to 140 psi if the engine is ok ??

[@godzonerefections]

@@johnrenehan7406 Thanks for reply. I have he XJ650 startong instantly and idling woohoo. I can get the reves yp but then spluttering and assume the advance retard is not actuating. There is a tube coming off #1 carb inlet connected to the fuel petcock which may be the advance vacuum tube but can't see where to connect otherwise.

[@karlvanboxel561]

From memory u r supposed to position the crankshaft in a certain position via the marks on the ignition trigger plate and crank case b4 you release the camchain tensioner I know this all too well because I failed to do that prior to slackening my tensioner and retensioning the lock nut and there was a rather disturbing noise coming from the cam chain😮

[@pat2bornot2b]

Thank you for making the comment, you need to check position after tensioning best to have the cam cover off when doing this because it can put the cams out by one or more teeth

[@karlvanboxel561]

Just checked my factory manual it says to line up the C Mark on the trigger plate with the crank case mark b4 u do the undo the lock nut and bolt not quite sure why this is could be when all the pistons are all lined up evenly in the centre of their stroke or if there’s a spot in the crank rotation where there is not as much tension on the cam chain? Some people swap to the later model auto tensioner

[@pat2bornot2b]

@@karlvanboxel561 you are correct as this is for adjustment and most likely as you point out that the cylinder are all at the same point and possibly that no tension from the valve springs is on the camshafts themselves. I'm must check this out, thanks for the comment and info.