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For all those gurus out there can anyone confirm if I need a top end rebuild.
A bit of history.
At the 40,000km service I checked the valves and on #3 the clearances were almost gone indicating Valve seat recession. (I believe this is a common fault on my year)
I also was running Pipercross air filters (foam) and I suspect the engine was ingesting more junk than normal which may have contributed.
Anyway I re did the shims and brought the clearances back into spec. All good.
Recently the bike has been doing a strange wheezing type thing (kind of like a misfire) every now and then which seems to be getting worse.
Today I hooked up a Carbtune manometer thinking it would all be just a matter of rebalancing the throttle bodies. At first indication #3 vacuum was much lower than #1 & 2. 1 & 2 were reasonably close and balanced easily. When I went to bring #3 up to meet them the wheezing I was hearing increased as a kind of backfiring out of the throttles of 1 & 2. The only way it will run at the moment is if #3 is left at a much lower vacuum otherwise it eventually cuts out due to a kind of misfire.
My guess is that the #3 valves or seats are no good due to the VSR and need remachining and lapping. A compression test would probably confirm this but I almost think it's not necessary.
Any ideas? I would appreciate any feedback - preferebly that which finds a simple inexpensive solution.
A bit of history.
At the 40,000km service I checked the valves and on #3 the clearances were almost gone indicating Valve seat recession. (I believe this is a common fault on my year)
I also was running Pipercross air filters (foam) and I suspect the engine was ingesting more junk than normal which may have contributed.
Anyway I re did the shims and brought the clearances back into spec. All good.
Recently the bike has been doing a strange wheezing type thing (kind of like a misfire) every now and then which seems to be getting worse.
Today I hooked up a Carbtune manometer thinking it would all be just a matter of rebalancing the throttle bodies. At first indication #3 vacuum was much lower than #1 & 2. 1 & 2 were reasonably close and balanced easily. When I went to bring #3 up to meet them the wheezing I was hearing increased as a kind of backfiring out of the throttles of 1 & 2. The only way it will run at the moment is if #3 is left at a much lower vacuum otherwise it eventually cuts out due to a kind of misfire.
My guess is that the #3 valves or seats are no good due to the VSR and need remachining and lapping. A compression test would probably confirm this but I almost think it's not necessary.
Any ideas? I would appreciate any feedback - preferebly that which finds a simple inexpensive solution.