29-04-17, 11:35 PM
(This post was last modified: 30-04-17, 04:04 AM by tommyardin.)
(06-03-17, 07:55 AM)red98 link Wrote: Another one for valve clearences :thumbup ....re-grinding the valves would help your compression figures aswell....
had my X7 rebored a couple of yeasr ago...£50 per cylinder + new oversized pistons and rings , dont think thats your problem though .....
tommy , showing your age there buddy :lol ..those old bikes would have been "overhead valve" engines , valves operated by a push rod from the cam located close to the crank , these new fangled motor cycles have the cam on the top and driven by a chain...called "overhead cam" engines.....still important to check valve clearences on the fazers after head removal....
Are not all modern motor cycle engines overhead valve? the really old motorcycles like my original BSA M21 was Side Valve, the BSA Super Rocket (1961) was Overhead Valve with under slung cam shaft running push rods .
If the valve settings are tight it will cause the seats on the valves to burn and also the seating in the head, they will require lapping/grinding in or replacing if they are badly burnt.
I will side with the others in here that said valves causing the lack of compression as the bike has done low mileage, if the bores still had any sign of honing in them they are not worn, plus the piston rings are under a lot of compression in the bores and will take up a certain amount of wear ,as long as the wear is uniform and the bore are not slightly oval, the usual sign of bores being worn is piston slap and a small amount light blue smoke when running, if the bike gives out a big puff of blue smoke when it first start but stops smoking after a few seconds it can point to unseated valves and/or worn valve stem/guides.
But as Red said my knowledge is of older machines, but the principles of the combustion engine remains the same, just much more refined.
As someone else pointed out a teaspoon or two full of clean engine oil down each plug hole will determine if its bores, all the plugs out to start with, oil down each bore one at a time as you test it with the throttle against the wide open stop, if there is no marked improvement in compression then it points to the valves or a head gasket blowing between cylinders.