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biltonjim wrote:

I imagine that for the cam timing to have changed, the cam chain would have to be so far from being at the correct ‘tension’  that you would have had audible warning that something was amiss in that department. Was the engine sounding rattly?

It has been awhile , but from Memory , [ 1988ish ] here is what happened to My Bike . Pulled into Service Station for Petrol [ Gas ]. Pulled out into Traffic , busy Road , no quick acceleration . Pulled off the Main Road ,  30 MH limit , opened throttle , riding riding without haste . Felt hesitant , sensed , rather than felt , misfire . Assumed bad Petrol , never used that particular Service Station before , but it was always busy. Arrived Home. Removed Petrol from Tank into a large plastci container , and sure enough , I could see a glob about 6inches diameter , just like a Jelly Fish . Emptied Float Bowls , re-fitted , re-filled Tank , tested the Bike , same problem . Removed Carbs , found them spotless , and re-cleaned them to be doubly sure . Went through all the Electrics , no change . Over about Three Weeks , after Work I double checked everything , and started to doubt myself . I then , first time ever , and I have been riding since 1964 , I took my bike to a Local Shop . Went to collect , all done , they said , we balanced the carbs , all appears O.K  . On the ride Home , it did feel better , but I could feel a misfire . As I had checked everything , all that was left , I was thinking , was the Valve Timing . Remember , We now have the Wonderful Internet . That is when I found the Timing Chain had jumped one Tooth , on the Exhaust Camshaft . Replaced chain [ funny story there ] , and all was good .
 

Long day in the garage today but the water pump mechanical seal is done 
The job went really smooth but just took a lot longer than expected. I did replace the pump drive shaft oil seal while I was in there as it seemed daft not too. Cam box cover off tomorrow and check the valve timing and condition of the jockey wheel and tensioner as well. Wish me luck 
 

Ok this is what I hope is a final update on the long running saga  

 
It turned out the exhaust cam had jumped a tooth and put the timing out of sync. She’s all back together now and running as she should. I think the problem was of my own making as I didn’t adjust the tension correctly on the manual adjuster I bought off eBay. I’ve replaced the original one after doing the modification and she runs a lot quieter now. While I had the top off I checked the valve clearances which where all in spec. A quick visual check of the jockey pulley and front rub guide showed very little wear so I’m happy she’s ok for now although I do intend to replace the tensioner with the upgraded one mentioned on here in the near future. Thanks to everyone for all the help and especially Clive (englishcw) for pointing me in the right direction with the timing jumping. 

CONGRATS! Well done. When my exhaust cam was 1 tooth out, it would idle and run great until pulling a hill.. then lack of power and over heating.

I bet you danced a jig when you found it, couldn't believe what you saw, and checked it twice? 

dcarver220b wrote:

CONGRATS! Well done. When my exhaust cam was 1 tooth out, it would idle and run great until pulling a hill.. then lack of power and over heating.

I bet you danced a jig when you found it, couldn't believe what you saw, and checked it twice?

Yes I didn’t believe what I was seeing? 
the inlet cam is easy to check as it’s got two center punch marks, one on top and the other inline with the cam box face at 90deg. The exhaust cam just has an “0” inline with the face which isn’t easy to see. I wound the motor over half a dozen times to make sure what I was seeing